Background of the Invention Nonwoven fabric is widely used in various applications, for example, baby's napkin, women's sanitary napkin and toilet paper, packaging materials of foods and detergents, adsorbents, adhesives, base fabric for embroidery, head rest for airplane seat and the like. The conventional various nonwoven fabric is made of synthetic fibers or natural fibers. As the synthetic fibers are not water soluble, the nonwoven fabric causes a serious environmental problem. Although the nonwoven fabric is made of natural fibers, if the natural fibers are not water soluble, the nonwoven fabric causes an environmental problem, too.

The natural fibers are cellulose fibers and classified into pure natural fibers such as cotton and wool, regenerated fibers such as viscose rayon, and pulp fibers.

The synthetic fibers are prepared from polymers such as polyethylene, polypropylene, polyamide, polyester and the like. Such natural and synthetic fibers are not water soluble. Therefore, most of the conventional nonwoven fabrics including the packaging material and the head rest are water insoluble.

Such nonwoven fabrics are rarely recycled and disposed by burial in the ground or by combustion. The burial or combustion of the nonwoven fabric causes

serious environmental problems. If the nonwoven fabic is water soluble, such environmental problems could be prevented.

In case that a water soluble nonwoven fabric is absolutely needed, a special method to dissolve the nonwoven fabric has been applied. For example, a base fabric for embroidery should be water soluble. The base fabric for embroidery is a nonwoven fabric and used for embroidery in lingerie. The base fabric is used to embroider on the lingerie, then the base fabric should be removed by dissolving.

The conventional nonwoven base fabric for embroidery is prepared from polyvinyl alcohol staple fibers. After embroidery on lingerie, the base fabric is removed. To remove the base fabric, the product should be treated in a hot bath over 95 °C. As the product is treated in a hot bath to remove the base fabric for embroidery, the lingerie can be damaged, the cost for manufacturing increases, and the material of the lingerie should be resistant to the hot temperature. If a base fabric for embroidery which is water soluble at room temperature is developed, the disadvantages above can be solved. If so, it is not necessary to treat the lingerie at a hot bath to remove the base fabric, the cost for manufacturing shall go down, the material of the lingerie can be diversified to choose, and there is no risk for the product to be damaged from the hot bath.

If a nonwoven fabric which is water soluble at room temperature is developed, the applications can be expanded, for example, to the packaging materials, mulch films for agriculture, gauze for medical use and the like. The conventional gauze is agglomerated with blood on the skin of a human body. Accordingly, when the gauze is removed, a pain occurs. If the gauze is water soluble at room temperature or hot water soluble, the gauze can be easily removed without pain by dissolving the gauze in the water.

Further, if a water soluble nonwoven fabric is developed, the nonwoven fabric can be applied to mulch film for agriculture. There has been lots of efforts to develop a water soluble, biodegradable or ultraviolet degradable mulch film to obviate environmental problems. However, conventional mulch films are collected to dispose after harvest. Although a water soluble nonwoven fabric is developed,

the nonwoven fabric should not be dissolved for a certain period. Usually the nonwoven fabric for mulch film should not be dissolved for about three months which is a cultivation period. In other words, if a nonwoven fabric should have a dissolving time for about three months, the fabric can be applied to a mulch film.

U. S. Patent No. 5,041,252 teaches a nonwoven fabric consisting of water soluble resin fine fibers having a mean fiber diameter of at most 30 um and a basis weight of 5 to 500 g/m2, which is prepared by extruding an aqueous solution containing a water soluble resin or a melt of a water soluble resin plasticized with water through nozzles, stretching the extruded material to form fibers by a high speed gas flow, heating the fibers to evaporate the water in the fibers and then collecting the fibers.

Korean Patent Laid-Open No. 1999-67946 discloses a water degradable nonwoven fabric which is treated with a water jet, and has a high density portion and a low density portion, and has a breaking strength of at most 100 g/25 mm at wet state, and contains a water soluble or water swelling binder. Of course, the present invention is distinctive from the inventions of the U. S. patent and the Korean patent application above.

The present inventor has developed a new method of preparing a nonwoven fabric which is water soluble at room temperature, and whose dissolving time can be controlled for use.

Objects of the Invention A feature of the present invention is the provision of a nonwoven fabric which is water soluble at room temperature.

Another feature of the present invention is the provision of a water soluble nonwoven fabric which does not cause an environmental pollution.

A further feature of the present invention is the provision of a water soluble nonwoven fabric which is used as a base fabric for embroidery for lingerie, thereby the product is not treated in a hot bath, the lingerie cannot be damaged, the cost for

manufacturing decreases, and more materials for lingerie are available.

A further feature of the present invention is the provision of a water soluble nonwoven fabric which is used as mulch film for agriculture.

A further feature of the present invention is the provision of a water soluble nonwoven fabric which is used as a head rest for airplanes or buses.

A further feature of the present invention is the provision of a water soluble nonwoven fabric whose dissolving time can be controlled for use.

A feature of the present invention is the provision of a method of preparing a nonwoven fabric which is water soluble at room temperature.

Other objects and advantages of this invention will be apparent from the ensuing disclosure and appended claims.

Summary of the Invention The water soluble nonwoven fabric according to the present invention is prepared by (a) preparing a nonwoven fabric with cellulose fibers, (b) mercerizing the nonwoven fabric with aqueous sodium hydroxide in a solvent in a bath, (c) carrying out etherification of the mercerized fabric by adding monochloro acetic acid solution, (d) neutralizing the fabric with a hydrochloric acid solution to be a pH of about 6.0 to 9.0 in the bath, and (e) post-treating the fabric through dehydration and drying. The dissolving time of the nonwoven fabric can be controlled depending on the amounts of the solid monochloro acetic acid, solid sodium hydroxide and hydrochloric acid to be used.

Detailed Description of the Invention To prepare a water soluble nonwoven fabric according to the present invention, a nonwoven fabric should be prepared with cellulose fibers. The nonwoven fabric is treated to provide water solubility in accordance with the method of the present invention. A nonwoven fabric prepared with synthetic fibers cannot be applied to the

method of the present invention. A woven fabric, a knitted fabric, a sheet and a film which are prepared with cellulose fibers can be applied to a method of the present invention. Therefore, in the present invention, the nonwoven fabric prepared with cellulose fibers includes a woven fabric, a knitted fabric, a sheet and a film which are prepared with cellulose fibers.

The cellulose fibers are classified into pure natural fibers such as cotton, wool, linen, hemp and the like, regenerated fibers such as viscose rayon, and pulp fibers.

The products prepared with the cellulose fibers can be water soluble at room temperature when they are treated in accordance with the method of the present invention.

The nonwoven fabric prepared with cellulose fibers is treated with aqueous sodium hydroxide in a solvent in a bath. The treatment of a cellulose fibers product with aqueous sodium hydroxide is known as mercerization. The mercerization is easily carried out by an ordinary skilled person in the art to which the present invention pertains. A solvent is used for mercerization. Alcohols and acetones can be used as the solvent. The representative examples of alcohols are methyl alcohol, ethyl alcohol, isopropyl alcohol and the like, and the acetones can be easily selected by an ordinary skilled person in the art.

For mercerization in the present invention, aqueous sodium hydroxide and solvent are put into a closed reactor. Into the reactor is a nonwoven fabric prepared with cellulose fibers put. The aqueous sodium hydroxide is prepared by dissolving about 50-80 g of solid sodium hydroxide in powder per 100 g of the nonwoven fabric in about 30-180 g of water. A solvent is added to the reactor in the amount of about 600-1000 ml per 100 g of the nonwoven fabric. The amount of sodium hydroxide in solid controls the dissolving time of the water soluble nonwoven fabric.

In other words, the dissolving time of the water soluble nonwoven fabric depends on the amount of the sodium hydroxide in solid to be used in the mercerization step (b).

The more the solid sodium hydroxide is used, the shorter the dissolving time is. The closed reactor is kept at the temperature of about 30 ~ 60 C. The mercerization is conducted for about 1-4 hours.

After completion of mercerization of the nonwoven fabric, etherification of the mercerized nonwoven fabric is carried out by adding monochloro acetic acid solution. The etherification is conducted by adding monochloro acetic acid solution to the closed reactor. The monochloro acetic acid solution is prepared by dissolving about 10-120 g of monochloro acetic acid in solid per 100 g of the nonwoven fabric in about 20-720 g of a solvent. Alcohols and acetones can be used as the solvent. The closed reactor is kept at the temperature of about 60 ~ 90 °C. The etherification is conducted for about 1-3 hours. The amount of monochloro acetic acid in solid controls the dissolving time of the water soluble nonwoven fabric. In other words, the dissolving time of the water soluble nonwoven fabric depends on the amount of the monochloro acetic acid in solid to be used in the etherification step (c). The more the monochloro acetic acid is used, the shorter the dissolving time is. For example, if about 80-120 g of monochloro acetic acid in solid per 100 g of the nonwoven fabric is used, the dissolving time is controlled within about 2 hours.

If about 10-40 g of monochloro acetic acid in solid per 100 g of the nonwoven fabric is used, the dissolving time can be extended up to about 1 through 3 months.

In case that a shorter dissolving time is required as in the base fabric for embroidery, gauze and the like, the etherification of the nonwoven fabric is conducted with a monochloro acetic acid solution containing a more amount of monochloro acetic acid. And, in case that a longer dissolving time is required as in a mulch film for agriculture and the like, the etherification of the nonwoven fabric is conducted with a monochloro acetic acid solution containing a smaller amount of monochloro acetic acid.

After completion of etherification of the nonwoven fabric, the nonwoven fabric is neutralized with a hydrochloric acid solution. The neutralization of the nonwoven fabric is conducted in the closed bath by adding a hydrochloric acid solution. The neutralization of the nonwoven fabric may also be conducted in a separate bath in which the etherified nonwoven fabric is neutralized with a mixed solution of hydrochlroride and a solvent. The amount of hydrochloric acid controls the dissolving time of the water soluble nonwoven fabric. In other words, the dissolving

time of the water soluble nonwoven fabric depends on the amount of the hydrochloric acid to be used in the neutralization step (d). The bath for neutralization should be kept at a pH of about 6.0-9.0. The hydrochloric acid solution is prepared by mixing about 10-40 ~ 40 ml of hydrochloric acid with about 300 ~ 500 ml of a solvent per 100 g of the nonwoven fabric.

After completion of neutralization of the nonwoven fabric, the nonwoven fabric is post-treated through dehydration and drying. In the post-treating step, the nonwoven fabric is dehydrated by a conventional method which is easily carried out by an ordinary skilled person in the art. The dehydrated nonwoven fabric is preferably dried at the temperature of about 50-150 °C.

As the nonwoven fabric according to the present invention is prepared with cellulose fibers and is completely water soluble, the nonwoven fabric can prevent any environmental problem. In particular, as the dissolving time of the nonwoven fabric can be controlled, the nonwoven fabric according to the present invention has various applications upon the uses.

The invention may be better understood by reference to the following examples which are intended for the purpose of illustration and are not to be construed as in any way limiting the scope of the present invention, which is defined in the claims appended hereto. In the following examples, all parts and percentage are by weight unless otherwise indicated.

Examples 1A-1D Nonwoven fabric was prepared with cotton fibers. Four specimens of the nonwoven fabric were prepared. Each specimen was 100 g. The specimens were put into four reactors separately (Examples 1A-1D). To the reactors were 50, 60,70 and 80 g of solid sodium hydroxide in powder added, respectively. To the reactors were 75,90,105 and 120 g of water added, respectively. Methyl alcohol of 800 ml was used per reactor as solvent. The reactors were kept at 50 °C. Mercerization was

conducted in the reactors for three hours.

To the closed reactors of Examples 1A-1D were 100 g of solid monochloro acetic acid and 300 ml of methyl alcohol added, respectively. Etherification was conducted in the reactors at 80 °C for 2 hours.

To the closed reactors was a mixed solution of 30 ml of hydrochloric acid and 400 ml of methyl alcohol added for neutralization. The treated nonwoven fabrics were dehydrated and dried at 100 °C.

The water soluble nonwoven fabrics of Examples 1A-1D were obtained. The dissolving times of the nonwoven fabrics of Examples 1A-1D were measured as 1.5, 1.2,0.5 and 0.2 hour, respectively.

Examples 2A-2D Nonwoven fabric was prepared with cotton fibers. Four specimens of the nonwoven fabric were prepared. Each specimen was 100 g. The specimens were put into four reactors separately (Examples 2A-2D). To the reactors was 70 g of solid sodium hydroxide in powder added, respectively. To the reactors was 105 g of water added, respectively. Ethyl alcohol of 800 ml was used per reactor as solvent. The reactors were kept at 50 °C. Mercerization was conducted in the reactors for three hours.

To the closed reactors of Examples 2A-2D were 10,50,90 and 120 g of solid monochloro acetic acid, respectively. To the reactors was 300 ml of ethyl alcohol added, respectively. Etherification was conducted in the reactors at 80 °C for 2 hours.

To the closed reactors was a mixed solution of 30 ml of hydrochloric acid and 400 ml of ethyl alcohol added for neutralization. The treated nonwoven fabrics were dehydrated and dried at 100 °C.

The water soluble nonwoven fabrics of Examples 2A-2D were obtained. The dissolving times of the nonwoven fabrics of Examples 2A-2D were measured as over 1 month, 3 days, 5 hours and 5 minutes, respectively.

Examples 3A-3D Nonwoven fabric was prepared with cotton fibers. Four specimens of the nonwoven fabric were prepared. Each specimen was 100 g. The specimens were put into four reactors separately (Examples 3A-3D). To the reactors was 70 g of solid sodium hydroxide in powder added, respectively. To the reactors was 105 g of water added, respectively. Methyl ketone of 800 ml was used per reactor as solvent. The reactors were kept at 50 °C. Mercerization was conducted in the reactors for three hours.

To the closed reactors of Examples 3A-3D was 100 g of solid monochloro acetic acid, respectively. To the reactors was 300 ml of methyl ketone added, respectively. Etherification was conducted in the reactors at 80 °C for 2 hours.

To the closed reactors was a mixed solution of 10,20,30 and 40 ml of hydrochloric acid and 400 ml of methyl ketone added for neutralization, respectively.

The treated nonwoven fabrics were dehydrated and dried at 100 °C.

The water soluble nonwoven fabrics of Examples 3A-3D were obtained. The dissolving times of the nonwoven fabrics of Examples 3A-3D were measured as 1.3 hour, 0.5 hour, 5 minutes and 1 minute, respectively.

The present invention can be easily carried out by an ordinary skilled person in the art. Many modifications and changes may be deemed to be with the scope of the present invention as defined in the following claims.