JP2013063376A - Filling method for filter cloth used in filter press - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a filling method for a filter cloth used in filter press with excellent filtration performance and durability.SOLUTION: In the filling method, to a peripheral edge of one side or both sides of a filter cloth 2 comprising either of polypropylene, polyester and nylon, a nonwoven fabric 1 composed of a thermoplastic resin of either of ethylene vinyl alcohol, polyethylene, polypropylene, polyester and nylon is mounted in a manner that the amount of the nonwoven fabric is 40-200 g/mfor a unit area in one face. Then, the nonwoven sheet is heated at 80-180 °C and pressurized to be heat-sealed to the filter cloth.

Description

  The present invention relates to a method for sealing a filter cloth for a filter press, and relates to a method for sealing a filter cloth for a filter press for preventing liquid from seeping out when a solid-liquid mixture is filtered with the filter cloth. .

A general filter press is a device that separates a solid-liquid mixture (raw solution) into a solid and a liquid using a filter cloth, but part of the filtered liquid may ooze out through the mesh of the filter cloth. If the exuded liquid evaporates into the atmosphere, such as liquor after filtering the sake lees and solvent after filtering the printer ink, the product yield may decrease, causing a foul odor or fire. There is a case.
Conventionally, a method of forming a seal has been used in which a silicone resin is applied to the periphery of a filter cloth to prevent liquid from seeping out. However, after applying the silicone resin, it takes time to dry until the solvent volatilizes, and in order to sufficiently impregnate, it is necessary to apply repeatedly, and there is a problem that it takes time and effort to manufacture. Further, when solvent-based materials are filtered, the silicone resin seals are dissolved and mixed into the filtered liquid, or the sealability is lowered.

In Patent Document 1, instead of a silicone resin sealing material, a synthetic resin belt-like fabric is heat-sealed to the periphery of the filter cloth to form a liquid-impermeable heat-sealing zone (sealing). The technology is described.
Inventors performed the sealing of the filter cloth using the synthetic resin strip-shaped fabric (film-like sheet) according to the technique of Patent Document 1, and as shown in FIG. When the belt-shaped dough having a thickness of 1 is heated and pressed by the heating platen 3, only the surface layer portion of the sheet 12 is first softened and melted locally, while the lower layer portion in contact with the filter cloth 2 is sufficiently heated. In this state, even if the softened / melted sheet 12 is pressed by the hot platen 3, the softened / molten resin in the surface layer is blocked by the unmelted lower layer. In rare cases, the filter cloth 2 did not reach and only dripped around. As a result, it was found that the filter cloth 2 could not be sufficiently impregnated with the molten resin.

  In order to solve such problems, the inventors set the heating temperature higher and accelerated the softening / melting of the belt-shaped dough. It was noticed that the other problem of lowering the filtration performance due to the decrease in the pressure also occurred.

Japanese Patent No. 3431689

  The present invention was made in order to solve the above problems related to filter cloth sealing, impregnating the filter cloth while avoiding dripping of the cloth for sealing, and having excellent filtration performance and durability. It aims at providing the sealing method of the filter cloth for filter presses which is excellent in property.

  When the inventors use a belt-shaped dough for heating and heat it, there is a time difference in the softening and melting of the surface layer portion and the lower layer portion, so that the above-mentioned problems may occur. Thinking about a fabric called a nonwoven fabric (web-like fabric) that melts quickly even at relatively low temperatures, and using this as a sealing material, the experiment was repeated. Even if some unmelted non-woven fabric is softened and melted, the liquefied non-woven fabric passes through the voids of the unmelted non-woven fabric to reach the filter cloth and penetrates. The present inventors have obtained the knowledge that the above problems can be solved, and have reached the present invention.

That is, the present invention is as follows.
(1) A filter cloth for filter press characterized by placing a nonwoven fabric on the periphery of a filter cloth for filter press, heating and pressurizing the nonwoven cloth, impregnating the filter cloth, and heat-sealing the filter cloth. Method.
(2) The material of the filter cloth is any one of polypropylene, polyester, and nylon, and the material of the non-woven fabric is any thermoplastic resin of ethylene vinyl alcohol, polyethylene, polypropylene, polyester, or nylon. The method for sealing a filter cloth for filter press according to (1).
(3) The method for sealing a filter cloth for filter press according to (1) or (2), wherein the non-woven fabric is placed on one side or both sides of a filter cloth.
(4) The method for sealing a filter cloth for a filter press according to any one of (1) to (3), wherein the nonwoven fabric is placed at 40 to 200 g / m ² per unit area on one side.
(5) The method for sealing a filter cloth for a filter press according to any one of (1) to (4), wherein the nonwoven fabric is heated and pressurized at 80 to 180 ° C.

  ADVANTAGE OF THE INVENTION According to this invention, the filter cloth can be impregnated by impregnating the filter cloth while preventing dripping of the dough for sealing, and the filter cloth for filter press can be provided with a superior filter performance and durability.

It is a perspective view for demonstrating typically the sealing method of the filter cloth for filter presses of this invention. It is explanatory drawing of embodiment which heats and pressurizes the nonwoven fabric 1 with the hot platen. It is explanatory drawing of embodiment which impregnates the nonwoven fabric 1 from the front and back both surfaces of the filter cloth 2, and heat-seal | fuses. It is explanatory drawing about the Example of this invention. It is explanatory drawing about the evaluation method of the degree of the thermal contraction rate of a filter cloth, and the degree of the oozing-out of a liquid. It is explanatory drawing about the problem at the time of heating and pressurizing and impregnating a filter cloth with a film-form resin sheet.

FIG. 1 schematically shows a state in which a nonwoven fabric 1 is placed on the periphery of a filter cloth 2 as a dough for sealing. In the present invention, a nonwoven fabric entangled with short fibers as shown in FIG. 1 is used as a fabric for sealing. First, the material of the nonwoven fabric used in the present invention and the manufacturing method thereof will be described.
(Nonwoven fabric material)
The material of the nonwoven fabric 1 of the present invention is, for example, polyolefin such as polypropylene, synthetic rubber, polyamide, polyester, or other thermoplastic resin, preferably ethylene vinyl alcohol, polyethylene, polypropylene, polyester, nylon. It is. Polyolefin-based polypropylene is particularly preferred for uses that require chemical resistance, such as solvent-based materials that do not dissolve even when filtered.

The nonwoven fabric 1 is made of a material having a melting point lower than that of the filter cloth 2. Since the nonwoven fabric 1 is in a laminated state in which short fibers are entangled, the nonwoven fabric 1 is characterized in that it softens and melts at a relatively low temperature as compared with a conventional belt-like fabric. Moreover, when the nonwoven fabric 1 is heated, it softens and melts in a short time, and the liquefied nonwoven fabric passes through the voids of the unmelted nonwoven fabric and reaches and penetrates the filter cloth. The problem that the thickness of the film becomes thin is less likely to occur.
(Nonwoven fabric manufacturing method)
Typical methods for producing the nonwoven fabric 1 include a wet method and a dry method (including a melt blow method), but are not limited to these methods. In the wet method, it is possible to manufacture a nonwoven fabric in a laminated state in which short fibers are suspended in water and rolled up with a net to entangle the short fibers called a web. Also, in the dry method, the resin chip is called a melt blow method, and the resin chips are heated and melted, extruded from a nozzle group onto a belt conveyor with high-temperature air to form short fibers, and the short fibers are peeled off to sandwich the short fibers with a hot roll. A laminated nonwoven fabric in which short fibers are entangled with each other can be produced.
(Filter cloth material, compatibility)
The filter cloth 2 used in the present invention is a woven cloth-like cloth having an average thickness of 0.5 to 2 mm that is usually used in filter presses. Examples of the material of the filter cloth 2 include polypropylene, polyester, and nylon.

It is best to impregnate the filter cloth 2 with a nonwoven fabric 1 made of the same material. For example, a polypropylene nonwoven cloth 1 for a polypropylene filter cloth 2 and a polyester cloth for a polyester filter cloth 2. The nonwoven fabric 1 is most compatible, but a polyethylene or polyester nonwoven fabric 1 can be used for the polypropylene filter cloth 2.
(Closing method)
Next, an embodiment of the sealing method of the present invention will be specifically described.

  FIG. 2 shows an embodiment in which the nonwoven fabric 1 placed on the periphery of the filter cloth 2 is heated and pressurized with a hot platen 3. The non-woven fabric 1 is placed with a certain thickness and width on a seal forming portion at the periphery of the filter cloth 2 provided on the lower plate 6, and is heated and pressurized between the lower plate 6 and the hot platen 3. . At this time, the non-woven fabric 1 heated by the heat from the hot platen 3 is softened and melted, and the non-woven fabric 1 liquefied by pressurization of the hot platen 3 is impregnated in the filter cloth 2 and heat-fused to form the filter cloth 2. Seals can be formed around the periphery.

Heating the nonwoven fabric 1 through the heat transfer plate 4 is preferable because the nonwoven fabric 1 can be heated and pressurized intensively, and pressure applied to portions other than the portion of the filter cloth 2 that forms the seal can be reduced.
Further, when a spacer 5 having a thickness equal to the total thickness of the filter cloth 2 and the heat transfer plate 4 is interposed between the lower board 6 provided with the filter cloth 2 and the heat board 3, the lowering of the heat board 3 is caused. Since it blocks, it is preferable because the pressure applied to the portion other than the portion of the filter cloth 2 that forms the seal can be reduced. Although omitted in FIG. 2, the nonwoven fabric 1, the heat transfer plate 4, and the spacer 5 are also present at the right end.

FIG. 3 shows an embodiment in which the nonwoven fabric 1 is impregnated from both the front and back surfaces of the filter cloth 2. By impregnating the nonwoven fabric 1 from both the front and back surfaces of the filter cloth 2, a stronger seal can be formed on the filter cloth 2. Further, even when the filter cloth 2 is thick, it is possible to easily form a strong seal by impregnating the nonwoven fabric 1 from both the front and back surfaces.
The thickness of the filter cloth 2 is preferably 0.5 to 1.5 mm. Thinners thinner than 0.5mm are not practical because they have to be finely crafted, while those exceeding 1.5mm require more nonwoven fabric 1 to be impregnated and the heating temperature and heating time must be increased. There arises a problem that the filter cloth 2 is thermally contracted and the gap is reduced.

The material of the lower board 6 used in the embodiment of the present invention may be any material such as metal, glass, resin, and wood as long as it is not softened by the heat from the hot board 3. Moreover, the shape of the lower board | substrate 6 should just be a flat surface of the grade which can provide the filter cloth 2. FIG. Or it is also preferable to heat the lower board | substrate 6 and to heat from both surfaces, and can impregnate the nonwoven fabric 1 in a shorter time.
In the present invention, the nonwoven fabric 1 needs to be softened and melted for the purpose of impregnating the nonwoven fabric 1 into the filter cloth 2, and the heating temperature of the nonwoven fabric 1 for that purpose is preferably in the range of 80 to 180 ° C. If the temperature is higher than this range, heat shrinkage of the filter cloth 2 may occur, and if the temperature is lower than this range, there is a problem that the nonwoven fabric 1 is not sufficiently softened and melted. For example, when the material of the nonwoven fabric 1 is polypropylene, the heating temperature of the nonwoven fabric 1 is preferably 80 to 130 ° C., 100 to 160 ° C. for polyester, and 140 to 180 ° C. for nylon.

The pressurizing force of the hot platen 3 may be any pressure that allows the filter cloth 2 to be impregnated with the softened and melted nonwoven fabric 1, but the applied pressure per unit area of the nonwoven fabric 1 is 0.3 to 10.0 MPa. A range is sufficient. If the applied pressure is larger than this, there is a problem that the softened and melted nonwoven fabric 1 leaks to the surroundings before impregnating the filter cloth 2.
Next, the amount of the nonwoven fabric 1 will be described. As the amount of the nonwoven fabric 1, it is necessary to ensure an amount sufficient to completely prevent the liquid from seeping out from the filter cloth 2, but the nonwoven fabric 1 of the present invention. In this case, the amount can be increased up to about 3 times compared to the conventional fabric, so that a more complete seal can be formed on the periphery of the filter cloth 2. The specific amount of the nonwoven fabric 1 is preferably 40 to 200 g / m ² per unit area of the nonwoven fabric 1 placed on one side of the filter cloth 2. In this case, the thickness is approximately 20 to 80 μm. If it is less than 40 g / m ² , the sealing may be insufficient, and if it exceeds 200 g / m ² , the ooze out to the surroundings will increase and the filtration area will be reduced. Particularly preferred is 150 to 200 g / m ² .

When the nonwoven fabric 1 is impregnated from both the front and back sides of the filter cloth 2, 40 to 200 g / m ² per unit area can be placed on each side of the front and back sides, so 80 to 400 g / m ^{2 on} both sides. By impregnating a large amount of the non-woven fabric 1, even when the filter cloth is thick and coarse, a tight seal can be formed.
When preparing a nonwoven fabric in the range of 40 to 200 g / m ² , it is usual to produce a single nonwoven sheet having a thickness that is the weight of the nonwoven fabric. It can also be weight.

  As shown in FIG. 4, the seal 11 is formed on the periphery of the filter cloth 2, and the effects of preventing the filter cloth 2 from being clogged and preventing the liquid to be filtered out from being filtered are verified. The peripheral edge of the filter cloth 2 refers to a portion that is sandwiched between the frame portions 10a of the filter plate 10 when the filter cloth 2 is folded and covered on a plurality of filter plates 10 and then press-contacted. FIG. 1 described above shows a state in which the filter cloth 2 shown in FIG. 4 is spread. In FIG. 6 described above, a film-like sheet (fabric 12) is placed on the filter cloth 2 seen in the AA cross section of FIG. 4, and the hot platen 3 is contacted, heated and pressurized to be impregnated. , Shows the heat fusion.

  As shown in Table 1, in the case of the nonwoven fabric 1 made of polypropylene as an example and the case of a film-like sheet (fabric 12) as a comparative example, each case No. is brought into contact with the hot platen 3 and heated and pressurized. Thus, the filter cloth 2 was impregnated with the nonwoven fabric 1 and the film-like sheet (fabric 12), respectively, and heat-sealed.

Example 1
Example 1 is a case where a non-woven fabric is placed on one side of a filter cloth, and is the case of cases No. 1 and 2 in Table 1. The amount of non-woven fabric is 80g / m ² and 150g / m ² respectively, and the thickness is 0.53mm and 1.0mm respectively. Polypropylene (melting point 100 ° C) non-woven fabric 1 and 0.5mm thick polypropylene (melting point 165 ° C) filter cloth 2, the nonwoven fabric 1 was heated at 110 ° C. for 60 seconds through the heat transfer plate 4 through the heat transfer plate 4 and pressurized at 1.0 MPa to impregnate the filter cloth 2.

(Example 2)
Example 2 is a case where a nonwoven fabric is mounted on both sides of a filter cloth, and is a case of cases No. 3 to 7 in Table 1. The amount of non-woven fabric is 80-200 g / m ^{2 for} each side of the filter cloth 2, the thickness is 0.53-2.0 mm of polypropylene (melting point 100 ° C.), and the thickness is 1.0 mm of polypropylene (melting point 165 ° C.). It is placed on both front and back sides of the filter cloth 2, sandwiched between the nonwoven fabric 1 and the nonwoven fabric 1 is heated on a heating plate 3 through a heat transfer plate 4 at 110 ° C. for 60 seconds and pressurized at 1.0 MPa to impregnate the filter cloth 2. I let you.

(Comparative Example 1)
Comparative Example 1 is a case where a film-like sheet is placed on one side of a filter cloth, and is the case of Case No. 8 in Table 1. A film-like sheet (fabric 12) of thermoplastic adhesive polyethylene having an amount of 100 g / m ² and a thickness of 120 μm is placed on one side of a polypropylene filter cloth 2 having a thickness of 0.5 mm, and a film-like sheet ( The dough 12) was heated on a heating plate 3 at 110 ° C. for 60 seconds and pressurized at 10 MPa to impregnate the filter cloth 2.

(Comparative Example 2)
Comparative Example 2 is a case where the amount of non-woven fabric is too small, and is the case No. 9 in Table 1. A non-woven fabric 1 of polypropylene (melting point 100 ° C.) having an amount of 30 g / m ² and a thickness of 0.2 mm is placed on one side of a filter cloth 2 of polypropylene having a thickness of 0.5 mm (melting point 165 ° C.). The nonwoven fabric 1 was heated at 110 ° C. for 60 seconds with a heating plate 3 and pressurized at 1.0 MPa to impregnate the filter cloth 2.

(Comparative Example 3)
Comparative example 3 is a case where there are too many cases, and it is a case of case No.10. 300g / m ² , 2.0mm polypropylene (melting point 100 ° C) is placed on one side of 0.5mm polypropylene (melting point 165 ° C), heated at 110 ° C for 90 seconds through the heat transfer plate 4, and added at 1.0MPa Pressed.
Next, for each of the examples and comparative examples, in order to see the degree of thermal contraction of the filter cloth 2 and the degree of oozing out (liquid leakage) of the liquid to be filtered, from the polypropylene filter cloth 2 described above, FIG. A sample (thickness t = 1.0 mm, width a = 220 mm, length b = 310 mm filter cloth) as shown in (a) was cut out and evaluated as follows. The formation position of the filter cloth 2 is set at a distance d = 30 mm from the outer peripheral portion (FIG. 5A), and the width e of the seal 11 is set to e = 35 mm.

  The degree of heat shrinkage of the filter cloth 2 was evaluated as follows. Three squares h with 100mm length and width on the filter cloth 2 are drawn in advance (Fig. 5 (a)), and the lengths of the vertical and horizontal sides of each square before and after thermal fusion are measured. The shrinkage rate of each side was determined, and the larger value was taken as the shrinkage rate of the square. And the shrinkage rate of each three squares was calculated | required, respectively, and those three average values were evaluated as shrinkage rate of the filter cloth 2. FIG. Specifically, the case where the shrinkage ratio of the filter cloth 2 is 1.5% or more is shown in Table 1, and the case where it exceeds 0.5% and is less than 1.5% is indicated as Δ, and the case where it is 0.5% or less is indicated as ○.

  About the degree of liquid oozing, a small sample (vertical f = 80mm, horizontal g = 15mm (Fig. 5 (a))) straddling a heat-sealing band (sealing 11) from a filter cloth that is sealed in a strip shape As shown in FIG. 5 (b), the lower short side (g = 20 mm) is immersed in colored water, and whether the colored water goes up across the heat-sealing zone (stop 11) after 12 hours. Observed and evaluated. X when the colored water crosses the heat-adhesion zone further up, Δ when it crosses the heat-adhesion zone and begins to bleed on it, did not go up above the heat-adhesion zone Cases are shown in Table 1 and shown in Table 1.

In Example 1, the heat shrinkage of the filter cloth 2 was lower than the reference value, and there was almost no heat influence on the filter cloth 2, and clogging due to the heat shrinkage could be prevented well. Further, the run-up of the colored water was suppressed, and the effect of preventing the liquid from bleeding out was also good.
In Example 2, the amount of impregnation of the nonwoven fabric 1 can be increased by the amount of impregnation of the nonwoven fabric 1 from both the front and back surfaces of the filter cloth 2, and clogging due to thermal shrinkage is prevented even for the filter cloth 2 that is thicker than in Example 1. As a result, the effect of preventing the liquid from bleeding out was obtained.

On the other hand, in Comparative Example 1 using a film-like sheet, the degree of thermal shrinkage of the filter cloth 2 is relatively large, and clogging due to the heat effect on the filter cloth 2 cannot be sufficiently prevented. Further, the run-up of the colored water is not suppressed, and the effect of preventing the liquid to be filtered out (liquid leakage) is not sufficient.
In Comparative Example 2 using the non-woven fabric 1, the amount of impregnation of the non-woven fabric 1 is too small, so that the run-up of the colored water is not suppressed. In Comparative Example 3, it is too much, so it is necessary to increase the heating time. 2 is thermally contracted.

DESCRIPTION OF SYMBOLS 1 Nonwoven fabric 2 Filter cloth 3 Heating board 4 Heat-transfer plate 5 Spacer 6 Lower board 10 Filter board 10a Frame part of filter board 10 Sealing 12 Dough

Claims (5)

  A method for sealing a filter cloth for filter press, comprising placing a nonwoven fabric on the periphery of the filter cloth for filter press, heating and pressurizing the nonwoven cloth, impregnating the filter cloth, and heat-sealing.   The material of the filter cloth is any one of polypropylene, polyester, and nylon, and the material of the nonwoven fabric is any one of thermoplastic resins of ethylene vinyl alcohol, polyethylene, polypropylene, polyester, and nylon. 2. A method for sealing a filter cloth for filter press according to 1.   The method for sealing a filter cloth for a filter press according to claim 1 or 2, wherein the nonwoven fabric is placed on one or both sides of the filter cloth. Filter press filter cloth the sealing method according to any one of claims 1 to 3, characterized in that 40~200g / m ² placed per unit area of one surface of the nonwoven fabric.   The method for sealing a filter cloth for a filter press according to any one of claims 1 to 4, wherein the nonwoven fabric is heated and pressurized at 80 to 180 ° C.

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