JPH0217666B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for displacing liquids from a fibrous sheet. More specifically, a fibrous sheet impregnated with a solution or dispersion of a polymeric substance is treated with a liquid that is a non-solvent for the polymeric substance but is compatible with the solvent or dispersion medium to remove the fibrous sheet from the fibrous sheet. The present invention relates to a method for removing a solvent or dispersion medium.

Traditionally, woven fabric is brought into contact with the surface of a rotating drum suspended in a solvent, and the solvent is absorbed into the rotating drum through the woven fabric, thereby dissolving and removing the glue, dye, etc. contained in the woven fabric. Methods are known. For example, Japanese Patent Publication No. 30-8539 proposes an apparatus using the above-mentioned principle as an apparatus for washing or dyeing woven fabric. however,
Although this type of device can be used for fibrous sheets with extremely good liquid permeability, such as woven fabrics, it cannot be used for fibrous sheets with poor liquid permeability, that is, thick fibrous sheets with dense internal structures. It has the disadvantage that it cannot. This is because when a fibrous sheet with poor liquid permeability is processed using a rotating drum method, the liquid enters only from areas where no resistance is encountered, that is, from the drum surface that is not covered by the fibrous sheet, and the liquid flows inside the fibrous sheet. This is because almost no water passes through the fiber sheet, and the fibrous sheet receives almost no cleaning action.

In recent years, fabrics such as nonwoven fabrics, woven fabrics, and knitted fabrics to which polyurethane elastomer is applied in a porous manner have been used as substrates for artificial leather.

The method for producing these artificial leather substrates is generally to impregnate a nonwoven fabric, woven fabric, knitted fabric, or other fabric with a solution of a polymeric substance such as polyurethane elastomer or polyvinyl chloride, and then impregnate it with a nonsolvent of the polymeric substance. However, a method is used in which the polymer substance is immersed in a liquid that is compatible with the solvent constituting the solution to coagulate it into a porous state, and the solvent contained in the fabric is replaced and removed with a non-solvent. It is being In addition, as a method for manufacturing artificial leather, a multicomponent mixed fiber obtained by mixed spinning or composite spinning of non-polar polymeric substances such as polystyrene and polyethylene and polar polymeric substances such as polyethylene terephthalate and polyamide is used. A fabric is formed, impregnated with a polyurethane elastomer solution or dispersion, and coagulated into a porous state. A method is used in which the solvent remaining in the fabric after removal with a solvent is removed with a non-solvent.

However, when the above-mentioned rotating drum method is used as a means for removing the solvent in these methods, the solvent is difficult to remove because the artificial leather substrate is usually thick and has a dense internal structure.

Conventional methods for removing solvent from artificial leather substrates include immersing the artificial leather substrate in a non-solvent, squeezing the substrate between Nitpro rolls, and dipping the substrate again in the non-solvent over and over again. has been done. Using this method, it is true that the solvent can be almost completely removed, but on the other hand, the artificial leather base passes between multiple stages of nip rolls, and is subject to excessive tension between the rolls, causing distortion. Become. Furthermore, since multiple stages of nip rolls and non-solvent tanks are required, the process becomes longer and the equipment becomes larger.

If it is possible to use a rotating drum instead of the multi-stage nip roll, which is generally used as a device to remove solvents from fibrous sheets with extremely poor liquid permeability, such as artificial leather substrates, and the solvent removal efficiency is sufficient. If it is high, excessive tension will not be applied to the fibrous sheet and the process can be extremely shortened, making it extremely useful.

An object of the present invention is to provide a rotating drum type solvent removal treatment method suitable for treating fibrous sheets with poor liquid permeability.

In other words, an object of the present invention is that in the case of a conventional rotating drum system that processes fabrics such as woven fabrics with low liquid flow resistance, the lower the liquid flow resistance of the drum itself, the more efficiently the fabric can be processed. In the case of a fibrous sheet such as an artificial leather substrate that has a high liquid resistance, most of the non-solvent absorbed into the drum flows through the fibrous sheet through the surface that is not covered with fabric at both ends of the drum, which has a low resistance. The objective is to solve the disadvantages that the amount of liquid used is small and the solvent is not easily removed.

As a result of various studies, the present inventors determined that the viscosity of the liquid, the liquid absorption speed, and the resistance of the rotating drum should be adjusted such that the ratio of the liquid passing resistance of the rotating drum and the liquid passing resistance of the fibrous sheet per unit area was 0.1 to 0.3. The present invention was achieved by discovering that the solvent in the fibrous sheet can be removed uniformly and efficiently by adjusting the body.

If this ratio is less than 0.1, the non-solvent will be absorbed into the drum mainly through the parts not covered by the fibrous sheet at both ends of the drum, so the removal rate of the fibrous sheet solvent will be low, and if the ratio is less than 3.0, the removal rate of the fibrous sheet solvent will be lower. If it is large, the liquid flow resistance increases as a whole, which increases the load on the liquid suction pump, which is uneconomical and tends to cause cavitation, which is not preferable.

Next, a specific example of an apparatus capable of carrying out the method of the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a longitudinal sectional view of the entire processing apparatus. In the figure, a rotary drum 4 is rotatably mounted on a shaft within a processing tank 1 filled with a solvent 2 submerged in the liquid. The fibrous sheet 3 is guided into the liquid from the guide roller 5, passes through the guide roller 6, and comes into contact with the circumferential surface of the rotating drum. It exits the tank through steps 8 and 8. The fibrous sheet 3 undergoes a liquid removal process while in contact with the circumferential surface of the rotating drum 4, and at least a portion of the circumferential surface of the rotating drum absorbs the solvent into the drum through the fibrous sheet. This structure allows the liquid to be removed by displacement. In the case of FIG. 1, the upper half of the rotating drum 4 has a structure that can absorb liquid, and the solvent containing the liquid sucked into the rotating drum is pumped into the pump 1.
0, it is taken out from the rotating drum through the pipe 9 and returned to the processing tank 1 through the pipe 11. Of course tank 2
The concentration of the liquid in the tank will only increase as the process continues, so some of the liquid in the tank can be taken out while replenishing some of the solvent through another pipe (not shown). The liquid concentration is prevented from exceeding a certain value. Further, the lower part of the rotating drum 4 is structured to allow backwashing. That is, after removing foreign substances such as polymer debris from the liquid 2 inside the processing tank 1, it is press-fitted into the rotating drum through the pipe 15, and the press-fitted liquid is discharged from the lower part of the rotating drum 4 to the outside of the drum. The structure is such that foreign matter adhering to the surface of the rotating drum 4 is dispersed.

FIG. 2 is a diagram showing the structure of the rotating drum 4. As shown in FIG.
The rotating drum 4 has both ends 16 and 17 of the shaft supported by bearings provided outside or inside the tank, and is rotationally driven. A large number of liquid suction ports 21 are provided on the surface of the rotating drum 4 so that the solvent can enter the drum from outside. However, in the case of a fibrous sheet with poor liquid permeability, the solvent may enter the drum exclusively from areas not covered by the fibrous sheet, or may flow unevenly within the fibrous sheet, causing the liquid to be removed. However, in the present invention, the equipment and processing conditions are adjusted so that the liquid passage resistance of the resistance plate on the surface of the rotating drum is in the range of 10 to 300% of the liquid passage resistance of the fibrous sheet.
To explain in more detail, the resistance of the fibrous sheet is represented by the pressure loss △P ₁ when liquid passes through it, and the resistance of the rotating drum resistor is also represented by the pressure loss △P ₂ . Regarding the average liquid passing speed v, the following relationship holds true.

△P ₁ αv ……(1) △P ₂ αv ² ……(2) From the relationship (1) and (2), △P ₂ ／△P ₁ αv ……(3) Then, △P ₂ / △P ₁ = Kv ……(3)′, where K is the resistance coefficient of the fibrous sheet, the rotating drum,
It was found that it is a constant value determined by the diameter, length, porosity of the liquid suction port, roughness of the liquid suction port wall surface, etc. The method of the present invention determines △
The solvent is uniformly removed from the fibrous sheet by passing the liquid through with the value of P ₂ /ΔP ₁ in the range of 0.1 to 3.0.

FIG. 3 is an example of a cross-sectional view of the surface of the rotating drum. The outermost peripheral surface of the rotating drum in contact with the fibrous sheet is covered with a net-like material 18, and below it is a plate 20 having a liquid suction port (hereinafter referred to as liquid suction port plate) and a surface of this liquid suction port plate. There is a partition plate 19 for dividing into a plurality of small sections, and each section separated by the partition plate 19 is provided with at least one liquid suction port 21 communicating with the inside of the rotating drum. Particularly, the part where both ends of the fibrous sheet touch is the partition plate 1.
Since the fibrous sheet covers the sections divided by 9, the liquid does not flow through the sheet, but instead passes exclusively through the areas not covered by the fibrous sheet.
Although the liquid removal process becomes insufficient, by sufficiently narrowing the distance between the partition plates (in the drum axis direction) at this location, it is possible to reduce the proportion of the untreated portion. In addition, by sufficiently reducing the diameter of the liquid suction ports 21 provided in each section separated by the partition plate 19 to increase liquid resistance, the amount of liquid that enters from areas not covered with the fibrous sheet can be relatively reduced. can be reduced. Furthermore, the compartments partitioned by the partition plate 19 are completely separated by the mesh 18, the partition plate 19, and the liquid suction port plate 20, and the liquid that enters the compartment is absorbed by the fibers that are in contact with the compartment. Preferably, only liquid enters through the sheet, and at the same time the flow of liquid between the compartments through the mesh 18 is almost negligible, so that the mesh 18 is placed on the partition plate 19. It is preferable that it be integrated with the partition plate without any gaps. In this regard, it is most preferred to use a punched wire mesh having an appropriate pore size and pitch as the mesh. Note that a punched wire mesh is a perforated plate with a porosity of about 10 to 50%, in which round holes or square holes are regularly arranged in a thin metal plate. In addition to the above-mentioned punched wire mesh, the net-like material referred to in the present invention refers to materials used as so-called materials such as cloth, felt, metal or plastic mesh, sintered metal, etc., depending on the processing purpose. It is a generic term.

In addition, if the liquid suction port 21 is blocked by fiber waste, polymer waste, etc., the fibrous sheet that is in contact with the section leading to the liquid suction port will not be subjected to the liquid removal process, and the liquid will be removed from the liquid inside the fibrous sheet. There will be spots where the liquid is not absorbed, but in order to prevent this from happening, it is effective to make the mesh diameter of the mesh provided on the surface of the rotating drum smaller than the diameter of the liquid suction port. It is.

The size of the rotating drum, the mesh diameter of the net-like material 18, the diameter of the liquid suction port 21, the size of the compartments divided by the partition plate 19, etc. will depend on the processing speed, the required liquid flow rate, and the flow rate of the fibrous sheet to be processed. It varies depending on the liquid quality etc. Generally, the appropriate diameter of the rotating drum is 30 to 100 cm from a production standpoint. When a punched wire mesh is used, the mesh diameter of the mesh material 18 is 0.5 to 1.5 mm, and the porosity is 10 to 1.5 mm.
30%, the diameter of the liquid suction port 21 is preferably 2 to 4 mm, the size of each section divided by the partition plate 19 is preferably about 2 to 8 cm in length in the drum axis direction, and about 20 to 80 cm ² in area.

FIG. 4 is a longitudinal cross-sectional view of part A of the rotating drum 4 shown in FIG. One end of the inside of the drum is sealed, and the other end is provided with holes 23 in each section by a partition plate 22, as shown in FIG.
It has a bright smooth surface. The interior of the fixed box 24, which has a smooth surface with holes 25 and 26 shown in FIG. is discharged from the pipe 2.
The liquid that entered the fixed box 24 from the hole 26
These liquids are press-fitted into the rotating drum from the inside of the fixed box 24, and the structure is such that these liquids do not mix inside the fixed box 24.

The apparatus of the present invention has the structure as described in detail above, but to explain the flow of the solvent again, it is sucked through the pipe 27 by the pump 10 outside the tank, so that the inside of the processing tank 1 is The solvent passes through the fibrous sheet 3 and enters the inside of the drum from the mesh 18 through the liquid suction port 21 provided in the liquid suction port plate 20, and enters the inside of the drum through the hole 23 which coincides with the hole 25 of the fixed box 24.
The liquid inside the roll, which is connected to the tank, passes through the holes 23 and 25 and is discharged from the tank through the piping 27.
On the other hand, the solvent pressurized by the pump 13 outside the tank enters the fixed box 24 from the piping 28, enters the rotating drum through the hole 23 of the rotating drum that coincides with the hole 26, and is sucked into the liquid suction port plate in that section. The liquid is discharged from the rotating drum through the liquid port. At this time, dust, fiber debris, etc. adhering to the net-like material on the surface of the rotating drum are dispersed from the drum surface, and so-called backwashing is performed. Further, as the rotary drum rotates relative to the holes 25 and 26 of the fixed box 24, the holes 23 provided in the rotary drum receive alternate flows of suction and backwashing liquid. In order to increase the liquid removal processing section of the fibrous sheet, the angle of the hole 25 of the fixed box 24 (α in FIG. 6) should be made large.
6 (β in FIG. 6) should be made larger.

In the method of the present invention, the liquid permeability of the fibrous sheet is extremely poor, and in order to suck the solvent from outside the rotating drum into the rotating drum through the fibrous sheet, it takes 1
If a suction force close to Kg/ ^cm2 is required, or if the non-solvent is heated to a temperature close to its boiling point, a rotating drum may be installed at the bottom of the tank to increase the liquid depth, or It is preferable to employ a method in which the inside of the tank is pressurized to force the liquid.

There is also a method in which the solvent is discharged from the inside of the rotating drum to the outside, contrary to the method described above. In this case, a device for pressing the fibrous sheet onto the circumferential surface of the drum is added, but the structure of the drum is basically the same.

As detailed above, by using the method of the present invention, the solvent can be sufficiently removed even from fibrous sheets with poor liquid permeability, and in addition, excessive tension is not applied to the fibrous sheets compared to the conventional multi-stage nip roll. figure,
Moreover, the process can be shortened, and the merits brought about by the present invention are extremely large.

Next, specific examples of the present invention will be given.

Example 1 A polyamide fibrous sheet was impregnated with a polyurethane dimethylformamide (hereinafter abbreviated as DMF) solution and immersed in water, which is a non-solvent, to coagulate the polyurethane into a porous state. Using the equipment described in 1 to 6, the DMF left in the fibrous sheet was removed by replacing water, which is a non-solvent, with an average flow velocity of 8.9 mm/sec and a liquid temperature of 80°C.
℃, the pressure loss due to the resistance of the fibrous sheet is △P ₁ = 652
Kg/m ² , the pressure loss △P ₂ = 648 Kg/m ² when passing through the water intake port of the rotating drum, and △P ₂ /△P ₁ = 0.993. The solvent could be removed uniformly with a flow-through amount of 46/m ² .

[Brief explanation of drawings]

Fig. 1 is a front view of the entire apparatus capable of carrying out the method of the present invention, Fig. 2 is a view of the rotating drum which is the main part thereof, and Fig. 3 is a vertical sectional view of the surface of the rotating drum. 4 to 6 are cross-sectional views of the rotary drum shown in FIG. 2 taken at sections A, B, and C, respectively.

Claims (1)

[Claims] 1. When removing a liquid from a fibrous sheet containing a liquid, a rotary drum having a liquid-permeable resistance plate is mounted on a shaft in a tank filled with a solvent that is compatible with the liquid. , the ratio of the liquid passage resistance of the rotating drum resistance plate and the liquid passage resistance of the fibrous sheet per unit area is 0.1.
A method of removing a contained liquid from a fibrous sheet by passing the solvent through the fibrous sheet under conditions such that the solvent is 3.0. 2. A patent claim using a rotating drum in which the circumferential surface of the rotating drum is covered with a net-like material or a porous material, and a plate having a large number of liquid suction ports is present below the net-like material or porous material. The method described in item 1. 3 Claim 2 in which the mesh is a punched wire mesh
The method described in section. 4. The method according to claim 2, wherein the surface of the plate having liquid suction ports is divided into a plurality of small sections by partition plates.