JPH0137508B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a nonwoven fabric manufacturing method and apparatus. More specifically, it provides a method and apparatus for manufacturing a thermally bonded nonwoven fabric at high speed and with good productivity by gripping a nonwoven web containing thermoplastic fibers with a porous member and injecting heated gas through the web at high speed. It is something to do. Conventionally, a method of thermally bonding webs by feeding them with their breathable conveying surfaces facing each other and supplying heated air is disclosed in US Pat. No. 4,011,124. In a similar method, heated gas is supplied to the web at a very slow speed of 50 m/sec or less to soften and melt the low melting point polymers that make up the web, thereby thermally bonding them. However, the processing speed was slow at less than 40 m/min, resulting in low productivity. Alternatively, it is necessary to perform the treatment many times and to provide a large number of treatment zones. On the other hand, the present inventors discovered that when high-speed heated gas is ejected through a very narrow slit, it reaches the web surface in an under-expanded form in an adiabatic manner, and then instantaneously passes through the porous member and nonwoven web. They discovered that the material expands and receives and receives heat, which significantly increases the processing speed. Furthermore, it has been found that the number of times of processing and the processing zone can be reduced and the size of the processing zone can be reduced even when the material has a relatively thick basis weight, probably because it enters the web in an under-expanded form. That is, the present invention grips a nonwoven web containing thermoplastic fibers from both sides with a moving porous member, and directs a heated gas flow from at least one side of the porous member through the porous member. When spraying and thermally bonding the nonwoven web, at least 2
It is characterized by thermal bonding by passing a heated gas flow at a speed of 100 m/sec or more through a long fiber nonwoven web made of single fibers made of polymers with different melting points or a mixture of these polymers. That is. The "nonwoven web containing thermoplastic fibers" in the present invention is made of an organic thermoplastic polymer. Examples include polyamides, polyesters and polyolefins. Furthermore, the thermoplastic fiber is a fiber in which a single fiber is made of at least two or more polymers having different melting points (for example, sheath-core type, eccentric sheath-core type, laminated type, etc.);
Alternatively, it is necessary to use fibers in which a plurality of single filaments are composed of at least two or more types of polymers having different melting points (for example, a mixed fiber type), or a mixture of several of these types. The melting point difference shown above is, for example, 10°C or more, preferably 50°C or more. Furthermore, for the (eccentric) sheath-core type, it is necessary that the low melting point component be on the sheath side. The low melting point component is softened and melted to the point where it can self-adhere. The ratio of the low melting point component to the high melting point component can be set arbitrarily based on the cross-sectional area ratio, but the lower limit of the ratio is determined from the viewpoint of adhesive strength, etc., but is preferably about 1/16, and the upper limit is It is determined based on the physical properties of the fiber. The nonwoven web in the present invention is a long fiber web, and it is particularly necessary that it be manufactured by a spunbond method. This is because the method of the present invention
This is because it exhibits excellent effects when used in the spunbond method, which has an extremely high production rate, which is becoming even faster in order to reduce costs. Moreover, a plasticizer, an adhesive, etc. may be applied to the web in advance in order to improve thermal adhesion. In the present invention, the speed of the heated gas must be 100 m/sec or more. Preferably 200m/
Should be taken at least sec. At speeds lower than 100 m/sec, the production rate will drop significantly or multiple treatments will be required. This also causes problems such as the thermal bonding state of the nonwoven fabric being different between the front and back sides. In the present invention, the heated gas is heated at 100m/sec from the slit.
The characteristic of the above speed is that it reaches the web in an adiabatic state, is instantly decelerated in the web layer, and heat exchange occurs. According to the present invention, its effects are fully exhibited when the moving speed of the web is 50 m/min or more, preferably 70 m/min or more. The velocity of the heated gas is adjusted by the flow rate of the heated gas and the slit width of the heated gas jet tube. Gas velocity is measured by inserting a pitot tube along the streamline, detecting the difference between dynamic pressure and static pressure, and converting the difference.The velocity is detected immediately after the heated gas is ejected from the slit. That is, it should be carried out at a position within 5 mm from the slit formation surface.
The pressure of the heated gas in the supply pipe of the heated gas is preferably 2 kg/cm ² or more, approximately 4 to 7 kg/cm ² . In the present invention, heated gas passes through a nonwoven web held by a porous member, expands, and after sufficient heat exchange is performed, it is sucked by a blower via a suction box. The suction action is performed for the purpose of environmental purification by not scattering the heated gas around, and for the purpose of providing some assistance for the heated gas to penetrate through the nonwoven web. It is desirable that the suction flow rate of the heated gas is at least the same amount as the ejection flow rate, preferably 5 times or more. In the present invention, the temperature of the heated gas is set to a temperature higher than the softening point of the lowest melting point component of the fibers constituting the nonwoven web and lower than the melting point of the high melting point component, for the purpose of thermally bonding the nonwoven web. The temperature must be sufficient to heat the The method for generating the heated gas is not particularly limited, and may be performed by a conventional method such as heating pre-pressurized air, pressurizing combustion gas, or heating high-pressure steam. Next, the present invention will be explained based on the drawings. FIG. 1 and FIG. 2 are explanatory diagrams showing an embodiment of the apparatus of the present invention. Arrows in the figure indicate the flow of heated gas. High-temperature, high-pressure heated gas generated by a heated gas generator (not shown) flows from the piping into the heated gas supply pipe 1, passes through the slit 12 shown in FIG. It is ejected onto the woven web 7 and is evacuated or reheated via the net conveyor 4, which also moves, from the suction box 2 provided close to the net conveyor 4 by the turbo fan 17 shown in FIG. On the other hand, the nonwoven web is transferred to a net conveyor 4, which is moved by a drive roll 5, and an upper net conveyor 3, which is moved in synchronization with the net conveyor 4.
Then, it is gripped and sent out via two pairs of presser rolls 6. In this way, the heated gas is passed through the entire surface of the nonwoven fabric, resulting in thermal bonding. The heated gas supply pipe according to the present invention is shown in FIGS. 3 and 4. Arrows in the figure indicate the flow of heated gas. The heated gas flows in from the pipe 13 of the flange 8,
It goes around from the tube end with the buff full 9, and the slit 1
Inject from 2. The slits 12 are formed by a slit interval setting plate 11 held by a holding plate 10 made of a heat-resistant material. They are integrally fixed in the defined slits by means of locking bolts 14. The heated gas supply pipe is not particularly limited in structure except that it has a slit through which heated gas is ejected in a curtain shape. The width of the slit is 5 mm or less, preferably 1 mm or less. If the width is larger than that, the required flow rate of gas is very large, the production speed is slow, and the degree of welding between the front and back of the product is different. Further, it is preferable that the internal structure of the heated gas supply pipe is such that the temperature of the gas is made uniform by using a baffle plate or the like as shown in FIGS. 3 and 4, for example. The heated gas may be supplied to the heated gas supply pipe from the top of the pipe or from either end of the pipe,
Although not particularly limited, a method that minimizes the temperature distribution of the ejected gas in the pipe length direction is preferably used. The porous support member in the present invention means a porous conveyor or drum made of wire mesh, cloth mesh, plastic, or the like. Particularly when bonding bulky nonwoven webs, it is often advantageous for any of the support members to be constructed of a porous conveyor, such as to suppress shrinkage of the web as a whole. When the conveyor is constructed of a wire mesh, it is preferable that the wire diameter is 0.5 to 0.005 mm, the mesh is 20 to 150, and the porosity is 30 to 60%. For example, if the wire diameter is 0.5 mm and the mesh is coarser than the mesh 20, mesh-like marks will be left on the product and the quality will deteriorate. Also, wire diameter 0.05mm, mesh
If the mesh is finer than 150, the penetration power of the heated gas will be significantly lower, resulting in differences in the thermal bonding state of the product between the front and back sides. The heated gas supply pipe is provided with the slit 12 facing the web gripped by the porous support member so that there is almost no gap. On the other hand, a suction box is provided opposite the slit of the heated gas supply pipe via the web held by the porous support member.
A suction slit 19 is placed adjacent to the porous support member. At this time, the suction gas flow rate/the ejection gas flow rate should be set to 1 or more. If it is less than this, there may be a difference in the thermal adhesion between the front and back sides of the product. In addition, 15 in the figure is a smooth and slippery board,
16 is a suction box body, and 18 is a heater. In the present invention, the porous support members that grip the web must face each other and be pressed against each other in order to suppress shrinkage of the web during thermal bonding. The pressure is approximately 0.1-1 Kg/cm. According to the method of the present invention, even if the feeding rate of the nonwoven web is high, the number of processing times is extremely small, and a product with good productivity and no difference in thermal bonding state between the front and back sides of the product can be obtained. Examples will be described below. In the examples, tensile strength was measured according to JISL1068, and tear strength was similarly measured using the Elmendorf method. Further, the surface smoothness was measured using a surface roughness tester. The fluff is measured using a friction tester (manufactured by Daiei Kagaku).
After 100 times of rubbing, evaluation was performed on a 5-grade scale (grade 5: no fuzz at all to grade 1: noticeable fluffing). Example 1 This example shows an example of a preferred embodiment. Figure 1 shows a web of 3-denier single yarn obtained by the spunbond method deposited on a net conveyor with a core made of polyethylene terephthalate and a sheath made of nylon 6 with a cross-sectional area ratio of sheath/core = 7/5. Thermal bonding was carried out under the following conditions using the apparatus shown in . Net conveyor (upper and lower parts that grip the web) Mesh: 30 Conveyor speed: 60 m/min Wire diameter: 0.29 mm Net pressing force: 0.2 Kg/cm Open area ratio: Approx. 45% Heated gas (air) Air temperature in supply pipe; 280℃ Air pressure inside the supply pipe: 5Kg/cm ² G Spout speed (5mm from the slit): 210m/sec Supply pipe slit width: 0.7mm Air flow rate: 198Nm ³ /Hr Suction flow rate / Jet flow rate: 40/1 Supplied at high speed Both sides of the nonwoven web were thermally bonded by one heat treatment, and the surface was very smooth. The physical properties of the nonwoven fabric are shown below. Weight: 31g/ ^m2 Tensile strength: Vertical 8.4Kg Width 3.5Kg Tear strength: Vertical 0.96Kg Width 0.5Kg Thickness: 0.4mm Surface roughness: Vertical 7.1μ Width 6.5μ Fuzz: Front grade 4 Back 4 grade comparison Example 1 This comparative example shows the drawbacks of the conventional hot air suction method. The same nonwoven web as in Example 1 was used. Thermal bonding was carried out using the apparatus shown in FIG. 1 under the conditions shown below. Net conveyor Same as Example 1 Conveyor speed: 60 m/min Heated gas (air) Gas temperature inside the supply pipe: 283°C Supply pipe slit width: 1 m Ejection speed (slit exit): 5 m/sec Air flow rate: 10 Nm ³ /Hr Suction flow rate /Gushing flow rate; 400/1 The nonwoven web is not sufficiently thermally bonded to the back side with one heat treatment, and if it is not turned over and treated once again, it may cause puckering, and the inner layer is not bonded sufficiently, and the inner layer This caused peeling. The physical properties of the nonwoven fabric are shown below. Weight: 32g/m ³ (a) One heat treatment (b) Two heat treatments Tensile strength: Vertical 5.5Kg Width 2.8Kg
Vertical 6.8Kg Horizontal 3.1Kg Tear strength; Vertical 0.98Kg Horizontal 0.51Kg
Vertical 0.95Kg Horizontal 0.4Kg Fleece; Front 3rd grade Back 2nd grade
Front 3rd grade Back 3rd grade Example 2 This example shows the speed of heated gas and the state of thermal bonding. The same apparatus as in Example 1 was used, except that the pressure of the heated air was changed to adjust the gas velocity, and all other conditions were the same as in Example 1. The nonwoven web used was the same, had a basis weight of 33 g/m ² , and was treated once.

[Front] (B) shows that the sample was turned over and processed again.
Similar to (c) and (d), a product with no fluff was obtained, but (a)
Even after 4 treatments, fluff remained. Example 3 This comparative example clarifies the effect of suction and the structure of the conveyor net. A nonwoven web with a sheath/core cross-sectional area ratio of 2/1, consisting of a 2-denier single yarn obtained by a spunbond method, whose core portion was made of polyethylene terephthalate and whose sheath portion was made of polypropylene was used. Thermal bonding was carried out once using the apparatus shown in FIG. 1 under the following conditions. Net conveyor net speed: 80 m/min Net pressing pressure: 0.9 Kg/cm Heated gas (air) Air temperature in the supply pipe: 286°C Air pressure in the supply pipe: 4 Kg/cm ² G Speed (position 5 mm from the slit): 158 m/cm
sec Supply pipe slit; width 3mm x length 500mm Suction slit; width 20mm x length 550mm Other conditions are shown below. Suction flow rate/jet flow rate Net conveyor (E) 1/2 Upper/lower side 40 mesh wire diameter 0.27mm, pore size approx. 40
% (f) 1/1 〃 (g) 5/1 〃 (ch) 10/1 Upper 40 mesh, wire diameter
0.27mm open area rate approx. 40%, lower SUS plate thickness 0.1mm (Li)〃 10 meshes on both upper and lower sides,
Wire diameter 0.7mm, porosity approximately 50
% (NU)〃 300 mesh for both upper and lower sides,
Wire diameter 0.03mm, porosity approx. 42
% The properties of the nonwoven fabrics obtained under each condition were as follows. In (e), the state of fuzz generation was different on both sides of the nonwoven fabric, and the fuzz on the suction side surface was as low as about 0.5 grade. The spout side surface was well bonded. Tensile strength (vertical) is 8.3Kg, tear strength is 1.15
It indicated Kg (horizontal). In (f), both surfaces of the nonwoven fabric were adhered to almost the same degree, and the fluff was grade 4. Tensile strength (vertical)
was 8.9 kg, and tear strength (horizontal) was 0.83 kg. (G) is also grade 4 fluff on both surfaces, tensile strength (vertical) is 9.2Kg, tear strength (horizontal) is 0.71Kg
It was hot. (H) The SUS plate side surface was not bonded at all.
On the other hand, the surface on the spout side was in good condition. (li) Both surfaces of the nonwoven fabric were well bonded by heat, and the fluff was grade 4. Both surfaces had a clear pattern of wire mesh and were uneven. Tensile strength (vertical)
The tear strength (horizontal) was 9.1Kg and 0.68Kg. (nu)
The surface of the nonwoven fabric from which the heated gas is blown out is
The heat bonding is relatively good, with some fuzz coming out when you rub it with your fingers (fuzz grade 3), but the surface on the suction side is very fluffy when rubbed (fuzz grade 2).
class).

[Brief explanation of drawings]

FIG. 1 is a side explanatory view showing one example of the device of the present invention;
FIG. 2 is an explanatory plan view taken along the line A-A in FIG. 1, and FIG. 3 is a vertical side view showing an example of a heated gas supply pipe.
FIG. 4 is a longitudinal sectional front view of the same, and FIG. 5 is a schematic diagram of the suction box. 1... heated gas supply pipe, 2... suction box, 3,
4... Net conveyor, 5... Drive roll, 6... Presser roll.

Claims (1)

[Claims] 1. A nonwoven web containing thermoplastic fibers is gripped from both sides by a moving porous support member, and a heated gas flow is applied to the porous support from at least one side of the porous support member. When spraying and thermally bonding a nonwoven web through a member, a long fiber nonwoven web consisting of single fibers made of at least two or more polymers with different melting points, or a mixture of them, is used to increase the speed. A method for producing a nonwoven fabric, characterized by passing a heated gas flow of 100 m/sec or more through it and thermally bonding it. 2. The method for manufacturing a nonwoven fabric according to claim 1, wherein the ejected heated gas flow is sucked through the nonwoven web. 3. The method for manufacturing a nonwoven fabric according to claim 1, wherein the flow rate of ejected gas/flow rate of suction gas is 5 or more. 4 A porous member that supports the nonwoven web from both sides and is moved while being gripped by a pair of presser rolls has a slit adjacent to at least one side of the porous member for ejecting a high-speed heated gas flow onto the nonwoven web. A nonwoven fabric manufacturing apparatus characterized in that a heated gas ejection pipe is provided, a suction duct is provided on one side opposite to the suction duct for sucking and removing the heated gas flow, and the pair of presser rolls are close to the front and rear of the heated gas ejection pipe. . 5. The nonwoven fabric manufacturing apparatus according to claim 4, wherein the slit spacing is 1 mm or less. 6 The porous member has a wire diameter of 0.05 to 0.46 mm, mesh 20
5. The apparatus for manufacturing a nonwoven fabric according to claim 4, comprising a wire mesh conveyor or a drum having a porosity of 30 to 60%.