JP3465752B2 - Biodegradable short fiber - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a biodegradable short fiber which is useful as a biodegradable nonwoven fabric or a biodegradable heat-adhesive fiber and which is excellent in post-processability.

[0002]

2. Description of the Related Art Conventionally, fibers used for sanitary napkins, sanitary materials such as diapers and daily life materials such as hand towels, wiping cloths are polyester, polyolefin,
Synthetic fibers such as polyamide are used. These fibers are difficult to decompose if left in the natural environment after use,
There are various problems. Therefore, it is necessary to bury these hygiene materials and daily life materials in the soil or incinerate them. However, the use of the land was limited because of its low biodegradability when buried in the soil. In order to solve such a problem, it is possible to use a material that is decomposed in the natural world.

As the biodegradable polymer, cellulose,
Cellulose derivatives, polysaccharides such as chitin and chito acid, proteins, poly-3-hydroxybutyrate produced by microorganisms, copolymers of 3-hydroxybutyrate and 3-hydroxyvalerate, polyglycolide, polylactide,
Aliphatic polyesters such as polycaprolactone are known.

Cellulosic cotton mainly used,
Regenerated cellulose is inexpensive but it is not thermoplastic and thus requires a binder, and when polyolefin, polyester fiber or the like is used as the binder fiber, these fibers are
This is a problem because it is difficult to disassemble.

Poly-3-hydroxybutyrate and copolymers of 3-hydroxybutyrate and 3-hydroxyvalerate produced by microorganisms are expensive and have limited uses, and are disclosed in JP-A-59-59419. As described above, there is a problem that sufficient strength cannot be obtained.

Polycaprolactone is a relatively inexpensive biodegradable polymer, but its melting point is as low as about 60 ° C., so that there is a problem that the drying temperature cannot be raised when a nonwoven fabric is produced by hydroentangling or a papermaking method. Further, the temperature of 60 ° C. is a temperature that can occur in the distribution stage in the natural world in the summer and there is a problem in heat resistance. Japanese Unexamined Patent Publication (Kokai) No. 5-78914 discloses a staple fiber made of polycaprolactone and / or polypropiolactone in order to improve heat resistance, but has a melting point of 60.
Since it is as low as -100 ° C, the thermal stability is not sufficient.
Japanese Patent Application Laid-Open No. 5-93316 discloses that heat resistance is improved by adopting a core-sheath structure, but once the core component is heated above its melting point, it cannot maintain its strength and is sufficient. is not. Further, when short fibers are used to make a nonwoven fabric in a webber or a papermaking process, conventional short fibers have a high elongation and it is difficult to uniformly defibrate them.

A material prepared by mixing polyethylene with starch has been studied as an inexpensive material, but it is not satisfactory in terms of biodegradability, and fibers having uniform mechanical properties have not been obtained.

[0008]

DISCLOSURE OF THE INVENTION In the prior art,
To obtain a biodegradable non-woven fabric which is relatively inexpensive and has practical heat resistance and strength, has a good texture when used in a non-woven fabric, and is free of thermoplastic biodegradable short fibers that are completely decomposed rapidly by microorganisms and which is practical. I couldn't. In view of such circumstances, the present invention is a thermoplastic biodegradable resin which is relatively inexpensive, has practical heat resistance and strength, and is completely decomposed by microorganisms having a good texture when a non-woven fabric having excellent post-processability is used. It provides short fibers.

[0009]

DISCLOSURE OF THE INVENTION The present inventors have found that thermoplastic biodegradable short fibers that are relatively inexpensive, have practical heat resistance and strength, and have a good texture when used in a nonwoven fabric and that are completely decomposed by microorganisms. As a result of earnestly studying the above, the above problem was solved by using polylactic acid and / or a thermoplastic resin mainly composed of polylactic acid as short fibers. That is, the present invention relates to a fiber made of polylactic acid and / or a thermoplastic resin containing polylactic acid as a main component and having a fiber diameter of 2.8.
d or less, strength 2.9 g / d or more , elongation 20% or less, 11
Dry heat shrinkage at 0 ° C is 30% or less, melting point is 120 ° C
Above and below 200 ° C. , mainly composed of biodegradable short fibers or polylactic acid and / or polylactic acid
In the thermoplastic resin,
Ester-bonded with acid, strength 3.5g / d or more,
The use of biodegradable short fibers characterized by having an elongation of 19% or less .

The present invention will be described in detail below. The viscosity average molecular weight of the polylactic acid and / or the thermoplastic resin mainly composed of polylactic acid used in the present invention is 5,000 or more, preferably 10 ⁴ to 10 ⁶ .
If it is less than 5,000, sufficient strength as a fiber cannot be obtained, and 1
If it exceeds 0 ⁶ , the viscosity becomes high during spinning and the spinnability is poor and not good. Thermoplastic fibers mainly composed of polylactic acid include cyclic lactones such as ε-caprolactone, hydroxycarboxylic acids such as hydroxybutyric acid, hydroxyisobutyric acid and hydroxyvaleric acid, lactic acid, ethylene glycol, 1,4-butanediol and the like. A dicarboxylic acid such as glycols, succinic acid and sebacic acid may be used alone or in combination of two or more.

The short fiber of the present invention has a strength of 2 g / d or more,
It is necessary that the elongation is 20% or less. Strength is 2g
If it is less than / d, the fibers may break or uniform fibrillation may not be possible during the processing of the nonwoven fabric by the webber or the papermaking process, which is not preferable. Further, if the elongation is more than 20%, it is difficult to uniformly disintegrate during processing of a nonwoven fabric by a webber or a papermaking process, which is not preferable. Dry heat shrinkage at 110 ° C is 3
It should be 0% or less, preferably 25% or less. When the dry heat shrinkage ratio at 110 ° C. is larger than 30%, the dimensional stability of the nonwoven fabric is deteriorated during the drying or hot air treatment process during the processing of the nonwoven fabric, or the texture becomes hard due to shrinkage, which is not preferable.

Polylactic acid and / or used in the present invention
Alternatively, by subjecting the terminal hydroxyl group of the thermoplastic resin mainly composed of polylactic acid to an ester bond with a carboxylic acid,
The thermal stability can be improved. The fiber strength can be improved by improving the thermal stability. Aliphatic carboxylic acids such as lauric acid and stearic acid can be used as the carboxylic acid. However, the carboxylic acid is not limited to the aliphatic carboxylic acid. Further, a lower fatty acid that vaporizes at room temperature and emits an irritating odor due to decomposition or the like is not preferable.

The biodegradable short fibers of the present invention can be obtained by melt spinning the above polymer by a conventional melt spinning method, stretching and then cutting, or high speed spinning and then cutting. The biodegradable short fibers can be subjected to a mechanical crimping process before being cut. As the mechanical crimping process, a pressing heating gear method, a stuffing box method, or the like can be used. The crimping method is not limited, and a known method can be used. When forming a web with a card, it is possible to improve spreadability. The number of crimps is 5 to 50/25 mm, preferably 10
The cut length is 10 to 80 mm, preferably 20 to 60 mm. In this case, if the number of crimps is less than 5/25 mm, an unopened portion is likely to occur during opening, and if it exceeds 50/25 mm, uniform opening cannot be obtained. The crimp ratio is preferably 5% or more, and more preferably 8% or more. When the crimping rate is less than 5%, a uniform web cannot be obtained when applied to a card and a sparse and dense portion is generated, which is not good.

The biodegradable short fibers used in the nonwoven fabric produced by the papermaking method have a fiber diameter of 0.5 to 5.0 d, preferably 1.0.
To 3.0 d, and cut length 1 to 25 mm, preferably 3
~ 15 mm. When the fiber diameter is less than 0.5 d and the cut length is less than 1 mm, it is difficult to make paper, and when the fiber diameter is more than 5 d and more than 25 mm, it is difficult to obtain a uniform nonwoven fabric by paper making, which is not preferable.

Biodegradable short fibers include anionic surfactants such as potassium lauryl phosphate and quaternary ammonium salts in consideration of card passing property, antistatic property, bundling property and dispersibility during papermaking. Cationic surfactants, nonionic surfactants such as aliphatic higher alcohols and ethylene oxide adducts of higher fatty acids, polyethylene glycol, polyalkylene glycols such as polyethylene glycol / polypropylene glycol block copolymers,
One or more kinds of silicone oils such as dimethylpolysiloxane, polyether modified silicone oil, and higher alkoxy modified silicone oil can be added.

The nonwoven fabric can be three-dimensionally entangled with a needle punch, a high-speed jet fluid, or the like. By carrying out three-dimensional entanglement, the strength and abrasion resistance of the nonwoven fabric can be improved.

When processing a non-woven fabric, some heat resistance is required. Usually, a drying step after water entanglement is required, and in this case, the drying efficiency becomes poor unless the temperature is 100 ° C. or higher. Also, considering the temperature stability of products in distribution, the summer season is 8
It may be stored at 0 ° C. As a fiber,
A melting point of 120 ° C. or higher, preferably 130 ° C. or higher is required.

The biodegradable short fibers in the present invention include other aliphatic polyesters such as polycaprolactone, polymers such as polyvinyl alcohol, polyalkylene glycol and polyamino acid, talc, calcium carbonate, calcium sulfate and calcium chloride. One kind or two or more kinds of inorganic substances, starch, proteins, food additives and the like can be mixed in appropriate amounts, and various mechanical properties, biodegradability and the like can be changed.

[0019]

The present invention will be further described with reference to the following examples. The tensile strength, elongation and dry heat shrinkage at 110 ° C. in the examples were measured according to JIS L1015.
The number of crimps and the degree of crimp were measured according to JIS L1015. The paper-making property and the card passing property were visually evaluated. The evaluation was made into three grades of bad, normal and good.
The texture of the non-woven fabric was evaluated by panelists (10 persons). The results were evaluated as 5 levels and averaged (5: very soft, 4: soft, 3: normal, 2: hard, 1:
Very hard). The melting point was measured by DSC. Regarding the biodegradability, the obtained non-woven fabric was buried in the soil, and after 3 months, the state of degradation of the non-woven fabric was visually evaluated. When the shape was lost, the biodegradability was considered good.

Examples 1, 2, 3 and Comparative Examples 1, 2. Polylactic acid having a viscosity average molecular weight of 80,000 has a diameter of 0.
Spinning speed of 50 from a spinning nozzle having 32 3 mm spinning holes
Melt spinning was performed at m / min. After unwinding the undrawn yarn, it is drawn 2.5 to 3.5 times at 80 ° C. to obtain a single yarn fineness of 3.5 to
2.5d of fiber was obtained. Apply an oil agent to this fiber and
Short fibers for papermaking were cut into m lengths. A non-woven fabric having a basis weight of 30 g / m ² was obtained by papermaking (Example 1). In addition, after drawing, fibers having a single yarn fineness of 2.5 to 3.5 d are introduced into a pressing gear type crimping machine heated to 70 ° C. to crimp them, and then an oil agent is applied thereto, and cut into 51 mm to obtain a card. A short fiber for use was obtained. 50 g of the short fibers with a random webber
/ M ² web, and then hydroentangling treatment to obtain nonwoven fabrics (Examples 2 and 3, Comparative Examples 1 and 2).

Comparative Examples 3 and 4. Lactic acid / ε-caprolactane copolymer (molar ratio: lactic acid / ε-caprolactane = 95 /
5) Polylactic acid having a viscosity average molecular weight of 60,000 is used at a spinning temperature of 140 ° C.
Then, melt spinning was performed at a spinning speed of 1000 m / min from a spinning nozzle having 32 spinning holes each having a diameter of 0.3 mm. The undrawn yarn was once wound and then drawn 1.8 times at 55 ° C. to obtain a fiber having a single yarn fineness of 2.0 d. Apply an oil agent to this fiber and
Short fibers for papermaking were cut into m lengths. A non-woven fabric having a basis weight of 30 g / m ² was obtained by papermaking ( Comparative Example 3 ). In addition, after drawing, a fiber having a single yarn fineness of 2.0 d is introduced into a pressing gear type crimping machine heated to 60 ° C. to crimp it, and then an oil agent is applied and cut into 51 mm to produce a short fiber for a card. Got The short fibers were made into a web having a basis weight of 50 g / m ² by a random webber and then hydroentangled to obtain a nonwoven fabric ( Comparative Example
4 ). Table 1 shows the physical properties of the short fibers obtained in Examples 1 , 2, 3 and Comparative Examples 1 , 2, 3, 4 and paper-making properties, cardability, and biodegradability.

[0022]

[Table 1]

It can be seen from Table 1 that the biodegradable short fibers of the present invention have excellent biodegradability and good physical properties, and also have excellent heat resistance. In Comparative Examples 1 and 2, the elongation was high and the card passing property was poor.

Example 4 , Comparative Example 5 . Polylactic acid obtained by esterifying terminal hydroxyl groups with viscosity average molecular weight of 60,000 with stearic acid (molar ratio: lactic acid / stearic acid = 100 / 0.3)
Was melt-spun at a spinning temperature of 190 ° C. from a spinning nozzle having 32 spinning holes of 0.3 mm in diameter at a spinning speed of 300 m / min. The unstretched yarn was once wound up and then stretched 3 times at 80 ° C. to obtain a fiber having a single yarn fineness of 3.5 d (Example 4 ). Polylactic acid having a viscosity average molecular weight of 60,000 whose terminal hydroxyl group was not esterified with stearic acid was melt-spun in the same manner as in Example 5 and then stretched to obtain a fiber having a single yarn fineness of 3.5d (Comparative Example).
5 ). The physical properties of the fiber are shown in Table 2.

[0025]

[Table 2]

It can be seen from Table 2 that the fiber strength is improved when the terminal hydroxyl group is esterified with carboxylic acid.

[0027]

Industrial Applicability The biodegradable short fiber of the present invention has excellent biodegradability and good mechanical properties, is heat resistant, and has a good texture when used in a nonwoven fabric. Further, the nonwoven fabric using the biodegradable short fibers of the present invention is a disposable diaper, suitable for living materials such as sanitary napkin surface sheets and wiping cloths, agricultural materials, civil engineering materials, and has complete biodegradability in the natural world. .

Continuation of front page (51) Int.Cl. ⁷ Identification code FI D06M 101: 32 D06M 101: 32

Claims (2)

(57) [Claims] 1. A fiber made of polylactic acid and / or a thermoplastic resin mainly composed of polylactic acid, comprising the following (A):
Characterized by simultaneously satisfying (B), (C), and (D)
Biodegradable short fiber to be. (A) Strength of 2.0 g / d or more, elongation of 20% or less, 110
Dry heat shrinkage at 30 ℃ or less, melting point is 120 ℃ or more
Above and below 200 ° C. (B) The fiber has a cut length of 3 to 15 mm. (C) The number of crimps is 10 to 30/25 mm, and
The reduction ratio is 5% or more. (D) Anionic surfactant, cationic surfactant,
Nonionic surfactants, polyalkylene glycols and
And selected from the group consisting of silicone oils
At least one or more surfactants are added. 2. The polylactic acid and / or polylactic acid is mainly used.
The hydroxyl group at the molecular end of the thermoplastic resin
The biodegradation according to claim 1, which is ester-bonded with boric acid.
Short fibers.