Spunlace non-woven fabric and manufacturing method thereof

Abstract

Provided is a method for producing a spunlace nonwoven fabric in which, when a web comprising cellulose fibers is made into a nonwoven fabric by water flow interweaving, a multi-stage water flow interweaving treatment is performed with sterilized water, and a drying treatment is performed at a temperature of 120 DEG C or higher after the water flow interweaving treatment. At this time, it is possible to perform at least the last stage of treatment among the plurality of stages of water flow interlacing treatment using sterilized water directly supplied from the water source instead of circulating water in the water flow interlacing device. Provided is a spunlace nonwoven fabric in which the moisture content of the nonwoven fabric is 8 mass% or less and the number of bacteria (average value) is generally 50 CFU / g or less.

Description

[0001] This application is a divisional application of patent application 201810116714.7 (application date: February 6, 2018, invention title: spunlace nonwoven fabric and method of manufacturing thereof). Technical Field

[0002] This invention relates to a method for manufacturing spunlace nonwoven fabric. Background Technology

[0003] Spunlace nonwoven fabric is known as a high-quality nonwoven fabric (Patent Document 1). Spunlace nonwoven fabric is made by weaving a web of cellulose fibers such as cotton into a nonwoven fabric through water flow. In particular, there are spunlace nonwoven fabrics that are used in a wet state and are used in applications such as face masks, wet wipes, disinfectant wipes, and body wipes.

[0004] Patent Document 1: Japanese Patent Application Publication No. 2010-144281 Summary of the Invention

[0005] However, special care needs to be taken to prevent bacteria from multiplying when using nonwoven fabrics in a moist state.

[0006] Therefore, the purpose of this invention is to obtain a spunlace nonwoven fabric with a low bacterial count.

[0007] The spunlace nonwoven fabric and its manufacturing method of the present invention have the following characteristics.

[0008] (1) A method for manufacturing a spunlace nonwoven fabric, characterized in that, when a web composed of cellulose fibers is nonwoven by water flow interweaving, a multi-stage water flow interweaving process is performed using sterilized water, and the fabric is dried at a temperature of 120°C or higher after the water flow interweaving process.

[0009] (2) The method for manufacturing spunlace nonwoven fabric according to (1) above is characterized in that sterilized water supplied directly from a water source is used instead of circulating water in the water flow interlacing device to perform the final stage of the multi-stage water flow interlacing process.

[0010] (3) The method for manufacturing spunlace nonwoven fabric according to (1) or (2) above is characterized in that the moisture content of the nonwoven fabric after drying is 8% by mass or less.

[0011] The spunlace nonwoven fabric of the present invention has the following characteristics. That is, a spunlace nonwoven fabric is characterized in that it is composed of cellulose fibers and is formed by interweaving the cellulose fibers with water flow to form a nonwoven fabric, and the moisture content of the nonwoven fabric is 8% by mass or less, and the average bacterial count is 50 CFU / g or less.

[0012] In addition, a spunlace nonwoven fabric is manufactured by any one of the manufacturing methods in (1) to (3) above.

[0013] In addition, a spunlace nonwoven fabric is characterized by being manufactured by any one of the manufacturing methods in (1) to (3) above, and having a general bacterial count (average value) of less than 50 CFU / g.

[0014] In addition, a spunlace nonwoven fabric is characterized by being manufactured by any one of the manufacturing methods in (1) to (3) above, wherein the moisture content of the nonwoven fabric is 8% by mass or less.

[0015] According to the present invention, by using sterilized water for multi-stage water flow weaving treatment and drying it at a temperature of 120°C or higher after water flow weaving treatment, a spunlace nonwoven fabric that maintains a moist state and has a low bacterial count can be obtained. Detailed Implementation

[0016] Spunlace nonwoven fabric uses cellulose fibers as its constituent fibers, with cotton being particularly preferred. The fibers are interwoven using high-pressure water jets, thus maintaining the nonwoven fabric's shape. Because spunlace nonwoven fabric maintains its shape solely through the interweaving of fibers, it retains the gaps between fibers, resulting in a fluffy texture, a pleasant feel, and softness. Furthermore, by using cellulose fibers as the constituent fibers, the fiber ends are not sharp, making it smooth to the touch and suitable for applications involving direct skin contact.

[0017] In manufacturing such spunlace nonwoven fabrics, firstly, a web is obtained using cellulose fibers such as cotton through known methods. Next, the obtained web is loaded onto a perforated support. Examples of perforated supports include wire mesh, synthetic resin mesh, and other mesh fabrics with appropriate mesh counts.

[0018] Then, a high-pressure water flow is applied to the net thus supported on the porous support. The high-pressure water flow is obtained, for example, by injecting water at a pressure of less than 10 MPa from a jet orifice with a diameter of 0.05 to 2.0 mm. When this high-pressure water flow collides with the net supported on the porous support, the energy of the high-pressure water flow becomes the energy that causes the fibers constituting the net to move, resulting in the interweaving of the fibers.

[0019] High-pressure water flow is typically applied in multiple stages. From a water conservation perspective, the treated water used in the high-pressure water flow is recycled and reused after a single use. In this invention, water that has undergone sterilization treatment is used in the circulation. For example, water with approximately 0.1 to 0.3 ppm of sodium hypochlorite added can be used after sterilization treatment. Water that has undergone similar sterilization treatment, such as groundwater or river water, can also be used in addition to the circulating water.

[0020] By using sterilized water and applying high-pressure water jet treatment, sterilized nonwoven fabric can be obtained.

[0021] Alternatively, in addition to the above, sterilized water supplied directly from the water source, which is not part of the circulating water supply, can be used for the final stage of high-pressure water flow treatment. In this case, the number of bacteria present in the manufactured nonwoven fabric can be further reduced compared to using circulating water.

[0022] The material, after undergoing high-pressure water jet treatment, is dehydrated using a dehydration device such as a squeezing mill, and then dried at high temperature. High-temperature drying provides a more reliable sterilization effect. For example, the material can be passed through a hot air dryer. The preferred processing temperature, i.e., the set temperature when using a hot air dryer, is 120–150°C. Since the material is moist before drying, high-temperature drying results in a humid-heat state, thus achieving a sufficient sterilization effect. If the processing temperature is below 120°C, it is difficult to effectively sterilize common bacteria. Conversely, if the processing temperature exceeds 150°C, the energy cost in production increases. Therefore, a more preferred drying temperature range is 130–145°C. Within this range, a sterilized nonwoven fabric can be obtained without affecting production factors such as the basis weight and production speed.

[0023] The drying time is preferably 1 to 3 minutes. If the time is shorter than the minimum, even if the temperature is set within the appropriate range mentioned above, sufficient sterilization effect will not be achieved. Conversely, if the time is longer than the maximum, the production speed will be slower, the productivity will be lower, and the cost will be higher, resulting in waste.

[0024] That is, according to the present invention, by using sterilized water for high-pressure water flow treatment and then performing a high-temperature drying treatment at 120-150°C, or by using sterilized water supplied directly from a water source for final-stage high-pressure water flow treatment and then similarly performing a high-temperature drying treatment at 120-150°C, even for use in a humid state, a spunlace nonwoven fabric with low bacterial count can be obtained. To maintain a sterilized state, the moisture content of the dried nonwoven fabric is preferably 8% by mass or less. Particularly preferred is 7% by mass or less. It should be noted that from the perspective of maintaining a sterilized state, the lower the lower limit of the moisture content, the better; however, considering the management of the manufacturing process for obtaining such a low moisture content spunlace nonwoven fabric, the lower limit is preferably around 4% by mass. From this perspective, a lower limit of 5% by mass is more preferred. The moisture content is determined based on Japanese Industrial Standard (JIS) K 0068 (2001), "Method for Determination of Moisture Content in Chemical Products," Section 7. Loss on Drying Method. It should be noted that the standard specifies a drying temperature of 105°C. The actual temperature is 2℃, but the moisture content recorded in this instruction manual was measured at a drying temperature of 110℃. The reason for changing the drying temperature is to achieve earlier drying.

[0025] It should be noted that high-pressure water flow treatment using water from a source is not limited to the final stage of treatment; the same treatment can also be implemented in stages earlier than that. That is, it is sufficient to implement the treatment at least at the final stage.

[0026] By performing this operation, a well-sterilized spunlace nonwoven fabric can be obtained, for example, a nonwoven fabric with a general bacterial count (average) of 50 CFU / g or less. The general bacterial count (average) is preferably 40 CFU / g or less, more preferably 30 CFU / g or less, and even more preferably 20 CFU / g or less.

[0027] In this invention, the general bacterial count (average value) is determined using the following method: 1 gram of spunlace nonwoven fabric is prepared, and after finely cutting the fabric to a size of 5 mm square or less, 20 ml of phosphate-buffered saline is added and mixed. 1 ml of the resulting mixture is taken from each of three petri dishes, and 20 ml of standard agar medium is added to each. After incubation at 35°C for 48 hours, the colony count in each petri dish is measured. The colony count per gram of spunlace nonwoven fabric is calculated from the measured values, and the average value is taken as the general bacterial count (average value) (CFU / g).

[0028] Example

[0029] (Example 1)

[0030] As a cellulose fiber, kapok fibers with a single fiber fineness of 1.7 dtex and an average fiber length of 25 mm were prepared and opened using a random carding machine to obtain approximately 100 g / m². 2 The obtained nonwoven web was placed on a movable perforated support (18 mesh) made of plastic fabric. For the nonwoven web, a high-pressure water jet device (nozzle diameter 0.13 mm, jet spacing 0.6 mm) was used to perform one high-pressure water jet treatment on one side (surface) at a jet pressure of 2 MPa, and another high-pressure water jet treatment at a jet pressure of 5 MPa. Then, the nonwoven web was reversed, and the other side (back side) was subjected to one high-pressure water jet treatment at a jet pressure of 4 MPa, and another high-pressure water jet treatment at a jet pressure of 5 MPa. Then, it was reversed again, and the surface side was subjected to one high-pressure water jet treatment at a jet pressure of 7 MPa. The water used in these five high-pressure water jet treatments was circulating water commonly used in nonwoven fabric manufacturing plants, and sterilization was performed by adding 0.1 ppm of sodium hypochlorite during the high-pressure water jet treatment.

[0031] The nonwoven web that has undergone high-pressure water jet treatment is subjected to a process where excess water is squeezed out by passing through a liquid rolling mill roller. Then, it is dried at a temperature of 145°C to obtain a cellulose nonwoven fabric with a moisture content of 5% by mass.

[0032] The average number of bacteria in the obtained cellulose nonwoven fabric was 40 CFU / g.

[0033] (Example 2)

[0034] Compared to Example 1, the following changes were made: In the high-pressure water jet treatment, after a total of 5 high-pressure water jet treatments were performed on the surface and back side, a further 1 high-pressure water jet treatment was performed on the surface at a jet pressure of 5 MPa. Otherwise, the cellulose nonwoven fabric of Example 2 was obtained in the same manner as in Example 1. Its moisture content was 5% by mass. It should be noted that the water used in the final (6th) high-pressure water jet treatment was not recycled water, but directly supplied water from a water source, which was sterilized by adding 0.1 ppm of sodium hypochlorite.

[0035] The average number of bacteria in the obtained cellulose nonwoven fabric was 20 CFU / g.

[0036] (Comparative Example 1)

[0037] Compared to Example 1, the following changes were made: sodium hypochlorite was not added during the high-pressure water flow treatment, and circulating water that had not undergone sterilization treatment was used. Then, except for this, the cellulose nonwoven fabric was obtained in the same manner as in Example 1. Its moisture content was 5% by mass.

[0038] The average bacterial count of the obtained cellulose nonwoven fabric was 67 CFU / g. It should be noted that there were deviations in the values ​​of the three petri dish samples in the general bacterial count determination, with one sample even exceeding 150 CFU / g.

[0039] (Comparative Example 2)

[0040] Compared to Example 1, the following changes were made: the drying temperature after high-pressure water jet treatment was set to 90°C. Then, except for this, the cellulose nonwoven fabric was obtained in the same manner as in Example 1. Its moisture content was 9% by mass.

[0041] The average number of bacteria in the obtained cellulose nonwoven fabric was 320 CFU / g.

Claims

1. A method for manufacturing a spunlace nonwoven fabric, characterized in that, When nonwoven from a web made of cellulose fibers through water flow interlacing, a multi-stage water flow interlacing process is performed using water that has been sterilized by adding 0.1 to 0.3 ppm of sodium hypochlorite. After the water flow interlacing process, the wet nonwoven web is dried at a temperature of 120 to 145°C, so that the moisture content of the dried nonwoven fabric is less than 8% by mass, thus producing a sterilized and dried nonwoven fabric. Subsequently, the nonwoven fabric is made into a wet state to produce any one of the following: a face mask, wet wipes, disinfectant cotton, and body wipes made from spunlace nonwoven fabric.

2. The method for manufacturing spunlace nonwoven fabric according to claim 1, characterized in that, Using sterilized water supplied directly from the water source, instead of circulating water in the water flow interweaving device, at least the final stage of a multi-stage water flow interweaving process is performed.

3. A spunlace nonwoven fabric manufactured by the manufacturing method described in claim 1 or 2.

4. The spunlace nonwoven fabric according to claim 3, characterized in that, The average bacterial count is generally below 50 CFU / g.