JPH0457953A - Microorganism-degradable nonwoven fabric - Google Patents

Abstract

PURPOSE:To obtain the subject inexpensive nonwoven fabric, useful for cover stock, etc., of disposable diapers, sanitary products, etc., and having a high tensile tenacity with thermoplasticity by constructing the nonwoven fabric from fiber of a specific single filament size composed of polycaprolactone-containing polyethylene. CONSTITUTION:The objective nonwoven fabric is obtained by melt spinning straight-chain low-density polyethylene or high-density polyethylene, containing 3-30wt.% polycaprolactone with preferably 20000-50000 molecular weight and having <=45 g/10min melt index value and using the resultant fiber having <=5 denier single filament size.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a nonwoven fabric that is biodegradable by microorganisms. More specifically, the present invention relates to a nonwoven fabric that is suitable for use as a cover stock for disposable diapers and sanitary products, or general household materials such as wipers and packaging materials, and is also biodegradable.

BACKGROUND OF THE INVENTION Nonwoven fabrics are widely used as sanitary materials, general household materials, and industrial materials, and the fiber materials that make up nonwoven fabrics are mainly polyethylene, polypropylene, polyester, and polyamide. Nonwoven fabrics made of these materials are chemically very stable in the natural environment of backing. Therefore,
Currently, used disposable nonwoven fabrics are disposed of by being incinerated or buried in the ground. In Japan, incineration is widely practiced, but it requires a large amount of overhead. Regarding burying, there is a problem that because the material is chemically stable, it remains in its original state in the soil for a long period of time. In recent years, pollution caused by waste plastics has been occurring, and how to deal with waste plastics has become a major social issue in terms of protecting the natural environment and the living environment. For these reasons, in the field of disposable products, the amount of nonwoven fabrics used is increasing year by year, and there is a demand for new nonwoven fabrics that naturally decompose within a short period of time. In general, fibers that are biodegradable by microorganisms include cellulose fibers such as cotton and hemp,
Examples include protein fibers such as silk. However, although it goes without saying that these so-called natural fibers have many excellent properties, the use of these fibers as non-woven fabrics for disposable products is not only costly, but also difficult to use. It may not be appropriate depending on the intended use. In addition, since these natural fibers are non-thermoplastic, it is not possible to use the so-called thermal bonding method, which involves thermally bonding fibers together to form a non-woven fabric. There is polyester that is made in nature. The most typical example is a polymer of 3-hydroxybutyrate (3HB). In addition, there are copolymers of 3-hydroxybutyrate (3HB), 3hydroxyvalerate (3HV), and 3-hydroxycaprolate (38C), and other copolymers.

On the other hand, industrially, microbially degradable and thermoplastic copolyesters are being produced using fermentation synthesis methods.For example, 3-hydroxybutyrate (3H
There is a copolymerized polyester of B) and 3-hydroxyvalerate (3HV).

However, there is currently a problem in that the production cost is extremely high.

As other synthetic polymer materials, aliphatic polyesters such as polyglycolide and polylactide, and copolymers thereof are widely known. Since these polymers are thermoplastic, they can be melt-spun, but the high cost of the polymers limits their application to areas such as bioabsorbable sutures.

Recently, some films in which starch is mixed with polyethylene have been put into practical use as microbially degradable films. but,
Since it is not easy to obtain fibers with a fineness suitable for use in nonwoven fabrics, starch-containing fibers with a fineness of fineness are not available at present.

As mentioned above, it is extremely difficult to obtain fine fibers that are microbially degradable and thermoplastic at a low cost. It can be said that the practical application of this technology is significantly delayed.

Problems to be Solved by the Invention In view of the above background, the present invention aims to provide an inexpensive nonwoven fabric that is both microbially degradable and thermoplastic, based on polyethylene, which is a general-purpose material. It is something.

Means for Solving the Problems The present inventors have conducted intensive studies to solve the above problems, and as a result, have completed the present invention.

That is, in the present invention, polycaprolactone is contained in an amount of 3 to 30% by weight.
It is a microbially degradable nonwoven fabric composed of polyethylene fibers with a single filament fineness of 5 deniers or less.

To describe the present invention in more detail, the polycaprolactone used in the present invention is generally a thermoplastic crystalline polyester having a melting point of about 60°C obtained by ring-opening polymerization of ε-caprolactone. For details, the molecular weight is 10,000.
~100,000 polycaprolactone is used, preferably polycaprolactone having a molecular weight of 20,000 to 50,000. On the other hand, polyethylene as a base polymer is linear low density polyethylene (LLDPE).
), or high density polyethylene () (DPE), A
The melt index value measured by STM-D-1238(E) method is 45 g/10 minutes or less. Methods for mixing polycaprolactone and polyethylene include a method in which these two components are mixed in advance with a two-wheeled extruder and then used as a master chip, and a method in which they are mixed during spinning (chip breading or melt blending), but these two components are preferably mixed. The former method is used. In this case, the amount of polycaprolactone mixed with polyethylene is preferably 3 to 30% by weight. If it is less than 3% by weight, the microbial decomposition rate will be slow, and if it exceeds 30% by weight, the microbial decomposition rate will be faster, but the resulting fiber strength will be low, resulting in a decrease in the strength of the nonwoven fabric, making it unsuitable for practical use. . When polyethylene, which is the base polymer, has a melt index value exceeding 45 sr/10 minutes, it is difficult to increase the fiber strength.
The strength of the nonwoven fabric becomes low, which is not preferable.

The reason why the single fibers of the fibers constituting the nonwoven fabric are limited to 5 deniers or less is that the nonwoven fabric of the present invention is intended to have a soft texture that can be applied to disposable diapers, cover stock of sanitary products, wipers, etc. If the single fiber exceeds 5 denier, the nonwoven fabric will have a rough and hard texture, which is not preferable.
Alternatively, it is mixed with high-density polyethylene (HDPR) and spun using a normal melt spinning machine at a melting temperature range of 210 to 280°C, and after cooling and solidifying the spun filaments, the filaments are collected using an air sucker or the like. In the present invention, the web can be obtained by collecting and depositing filaments on a moving endless wire gauze to form sea urchin whelks, and then thermally bonding the web with a heated flat roll or embossing roll. The spun filament may be drawn after cooling and solidifying, and the drawn filament may be made into a web. In this case, the process from spinning to web formation may be carried out in a continuous process, or the drawn filament may be obtained separately and It can also be made into a staple fiber from a drawn filament,
The staple may be made into a web using a card machine, or the crimped stable fiber may be made into a web using a wet paper making method.

Of course, the cross-sectional shape of the filament is not limited to a round shape, and may be hollow, flat, Y-shaped, or other irregular shapes.

Function: With this configuration, it is possible to provide a nonwoven fabric with good microbial degradability, high strength, and a soft texture that can be applied to disposable diapers, cover stock for sanitary products, and the like.

Example Hereinafter, the present invention will be explained in more detail based on Examples.

The method for measuring the tensile strength of the nonwoven fabric shown in the Examples is as follows. Tensile strength crab of non-woven fabric JIS
According to the strip method described in L-1096, width 3 am,
The maximum tensile strength was measured from a test piece of length 103.

Examples 1 to 4, Comparative Examples 1 to 2 Contains polycaprolactone with an average molecular weight of about 40,000 and 5% by weight of octene-1, and has a density of 0.937 t/c11
ゝThe melt index value is ASTM D-1238 (
Measured by the method of E) 25g/10 minutes, melting point is 125
Master chips were prepared by mixing linear low-density polyethylene (LLDPE) at various ratios using a biaxial cross-wire extruder.

In addition, in Example 1, the content of polycaprolactone was 3% by weight, in Example 2 it was 10% by weight, and in Example 3 it was 20% by weight.
The percentage by weight was 30% by weight in Example 4, 1% by weight in Comparative Example 1, and 35% by weight in Comparative Example 2.

Next, using the obtained master chip, the hole diameter was 0.35mm.
, using multiple nozzles with 64 holes, 1.2g/
The continuous multifilament is melt-extruded at a spinning temperature range of 230-250'C at a discharge rate of 1 min/hole, and is taken up and moved at a speed of 3500 m/min using an air sucker installed at a position 120 clI below the nozzle. After the filaments were collected on an endless wire mesh to form a web, they were heat-treated using a metal embossing roll and a metal flat roll at a linear pressure of 30 kg/cs*, a pressure contact area ratio of 20%, and a heat treatment temperature of 105°C. A spunbond nonwoven fabric having a basis weight of 20 t/m and consisting of filaments having a single yarn fineness of 3 d was obtained. Table 1 shows the performance of each of the obtained nonwoven fabrics. In addition, in Table 1, regarding microbial degradability, nonwoven fabrics are
After being buried in soil at 0 to 25°C for 6 months, judgment was made based on whether the nonwoven fabric maintained its shape, or whether the tensile strength decreased to 50% or less of its initial value even if the nonwoven fabric maintained its shape. . If the tensile strength decreased to 50% or less of the initial value even if the nonwoven fabric was maintained, it was considered to have good microbial degradability, and if it did not, it was considered to have poor microbial degradability. Even in the case of good microbial degradability, the initial tensile strength of the nonwoven fabric is 800g/3c
If it was less than n, the overall evaluation was judged as poor.

From the results in Table 1, it can be seen that the nonwoven fabrics containing 3 to 30% by weight of polycaprolactone in Examples 11 to 4 have the highest nonwoven fabric performance (tensile strength).
It can be seen that both microbial decomposition properties are good.

Effects of the Invention As described above, according to the present invention, a nonwoven fabric having high tensile strength, microbial degradability, and thermoplasticity can be obtained without a significant increase in cost.

Agent Hiroshi Mori Moto

Claims (1)

[Claims] 1. A microbially degradable nonwoven fabric made of polyethylene fibers containing 3 to 30% by weight of polycaprolactone and having a single filament fineness of 5 deniers or less.