JPS6044012A - Clarifying filtering method of slurry containing fine particles and filter material for clarifying filtration - Google Patents

Abstract

PURPOSE:To facilitate the filtering of a slurry containing extremely fine particles and to facilitate the release of a cake from a filter material, by using a porous film which is formed by impregnating or coating a fibrous substrate with a specific polyurethane compositional solution, and subjecting the treated substrate to wet coagulation. CONSTITUTION:30pts.wt. of dimethylformamide and 25pts.wt. of various void forming agents are further added to 45pts.wt. of a polyurethane solution, which is prepared by dissolving polyurethane formed of a stock material consisting of polyester polyol, ethylene glycol, P,P'-diphenylemethane diisocyanate, in dimethylformamide and the resulting mixture is stirred for 30min by a stirrer and subjected to defoaming treatment to form a polyurethane compositional solution. This solution is applied to a substrate comprising a spun fabric in a thickness of 0.3mm.. The coated fabric is immersed in a 30% aqueous dimethylformamide solution at 25 deg.C to coagulate polyurethane and washed with water and dried to obtain a filter material. This filter material is good in releasability from a filter cake and enables the filtering of a slurry containing fine particles with a particle size of 0.05-5mum.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a clarifying filtration method for eliminating fine particles from a slurry containing fine particles, particularly fine particles having a particle size of 0.05 to 5 microns.

Conventionally, filter paper, densified needle-punched felt, calendered furnace cloth, etc. have been used as furnace materials to filter IJ-total slurry containing ff&f1 particles. Filter paper is made from short fibers made from wood, and is swollen and densified with water or an alkaline dispersion medium, so it is extremely effective in capturing all 7β particles, but the bonds between the fibers are extremely weak. Therefore, when making products from fine particles, i.e. solids separated by furnace, short fibers may be peeled off from the surface of the filter paper and mixed into the product, and the ability to maintain the shredded sheet form is small, and it may be necessary to It was damaged after being used for ~3 times, so the paper sound could not be reused after the cake was peeled off. High-density needle-punched felt and Zodofu, which is made by calendering a densely woven fabric, have fibers that are about 10 microns thick at most, so even if the fibers Mt are 100% laminated. However, it is impossible to distribute the pores uniformly enough to capture all of the fine particles of about 1 micron, which are formed by agglomeration of single particles or a plurality of particles.

Recently, with the development of foamed synthetic resins, LRI materials that utilize foamed synthetic resins have been proposed. For example, a urethane foam fabric with open air cells is impregnated with a glue-like substance such as Kazemono Soyaku or starch in a solution of 1-1, then pre-dried, and the primary urethane foam is heated and pressurized to lose its restoring power. FRZ materials are known that include urethane foam that is finally washed with water to remove the paste-like material from the urethane foam (see Japanese Patent Publication No. 1983-44.766).
. In fact, the above-mentioned known Zotsuki material is impregnated with a different type of glue-like polymer gel, the solvent is scattered and evaporated at an early stage, and the pore shape is flattened and fixed by heating and pressure. This is because it removes polymer particles.

The size of the formed pores σ) is not miniaturized, but it is completely impossible to classify the size of the pores, which are microscopic particles such as 0.05 to 5 microns, which is the object of the present invention. .

On the other hand, a mixed solution of polyurethane in an organic solvent and a powder is impregnated or applied onto a sheet-like substrate, and the sheet is treated with a liquid or its vapor that is compatible with the organic solvent but not a solvent with polyurethane. A so-called polyurethane wet coagulation method 1 is known in which a porous polyurethane film is formed by coagulating polyurethane and then removing all remaining organic solvent. The above polyurethane? The mixed powder contains anhydrous calcium pyrophosphate, boric acid, urea, thiourea, and sodium carbonate.

Powders that are soluble in coagulation 11, such as sodium bicarbonate, sodium chloride, sodium chloride, and sodium sulfate,
Alumina, silica, magnesia, calcium carbonate, magnesium carbonate, and graphite powder are known to be insoluble in any coagulant. In the polyurethane porous coating produced by the above-mentioned wet coagulation method, pores are generated in the coating during polyurethane coagulation, and pores are also generated due to the incorporation of powder. In other words, if the powder is soluble, pores will be created by elution into the coagulant when the polyurethane coagulates, and since the particle size of the powder to be mixed is at most about 200 mesh, the size of the pores created by the elution of the powder is It cannot be smaller than the particle size of the powder. In addition, if the powder is insoluble, the powder remains in the porous film, and it is thought that the powder itself is porous, and small cracks between the polyurethane and the powder form holes, making it porous. However, the pore diameter produced in this case is I
If this porous sheet is used to pass through a fine particle-containing slurry IJ-27rl, there is a great possibility that the particles remaining in the porous film will fall off and mix with the cake or 7N liquid, resulting in contamination. As mentioned above, conventional porous polyurethane sheets made by the powder mixed polyurethane wet coagulation process are still insufficient for filtering slurries containing fine particles of 0.05 to 5 microns.

The inventors of the present invention have accomplished the present invention as a result of intensive research into a method for clarifying and filtering a slurry containing fine particles of 0.05 to 5 microns, and a furnace material used for the above-mentioned filtration.

This application includes two inventions.
A second invention is a method for clarifying a slurry containing fine particles, which is characterized in that the slurry '17i containing micron fine particles is separated.

A polyurethane composition containing a pore-forming agent that is soluble in polyurethane or a good polyurethane solvent and also soluble in a polyurethane non-solvent is impregnated or applied onto a fiber base material and has a porous film formed by wet coagulation. This is a furnace material for clarifying and filtering slurry containing fine particles.

The furnace material used in this invention is one in which a polyurethane porous coating is entirely formed on a fiber base material.

This porous film consists of continuous pores, and pores with a pore diameter of 0.01 to 1 micron are concentrated and scattered in a surface layer with a thickness of 0.1 micron from the surface of the porous film, Due to the thickness of the layer, pores having a diameter larger than that of the surface layer are scattered in the inner layer.

Particle size 0.05~
Slurry k'JT containing 5 micron fine particles
``If the slurry is washed, the fine particles in the slurry will become single particles.

Irrespective of the grain size, the lrI material's thin surface capture type allows it to be squeezed from the early stages of recitation to obtain a clear n-liquid. Even if fine particles of 0.01 micron or less enter the pores of the FRR material, the particles will either flow out or adhere to the walls of the pores in the furnace material, resulting in clogging. Don't let it happen. Another effect of this full moon is that the cake adhering to the FP material can be easily peeled off. Generally, the cake formed by trapping fine particles is very viscous and has a
If the cake is not dehydrated at high pressure after filtration, the cake will be soft and difficult to peel off. If the degree of high-pressure deliquification of the cake is large, the cake becomes extremely hard and bites into the furnace material, but according to this invention, a thin microporous layer is formed on the surface layer of the square wood, and the Because pores with a slightly larger pore size were formed inside, immediately after the high-pressure deliquification was completed, the liquid inside the quencher moved to the surface of the furnace material due to the capillary action of the fine pores, causing the surface of the furnace material to become It becomes wet and adheres to the furnace material.

- Since the surface of the square material is also in a wet state, the bonding force between the cake and the layer material is weak, and the cake is very easily peeled off from the surface of the square material.

To produce the short material used in this invention, a polyurethane that is compatible with polyurethane, is soluble in the good solvent of polyurethane, and is compatible with the above-mentioned good solvent is added to a polyurethane solution. A porous polyurethane film is formed by wet coagulation after impregnating or coating a substrate with a polyurethane composition containing a non-soluble coagulant and a soluble pore-forming agent.

Weir construction method for furnace materials To explain in more detail, the polyol for producing polyurethane has an average molecular weight of 200 to 6.
000. Preferably, the molecular weight is 600 to 4000, and the m
evaporated ethylene glycol, diethylene glycol, ■
, 4-bucung glycol, propylene glycol, 1,
Examples include monomers such as 6-hexanediol and neopentyl glycol, lactone polyols, polytetramethylene gelicol, polyethylene glycol, and polypropylene glycol. Diisocyanates for the above polyol include 2,4- or 2,6-tolylene diisocyanate, p, p'-diphenylmethane diisocyanate, naphthylene diisocyanate, phenylene diisocyanate, 4-chloro-1,8-phenylene diisocyanate 1 to and hexamethylene diisocyanate. Chain extenders include ethylene glycol, triethylene glycol, propylene glycol,
Examples include trimethylolpropane, hexanetriol, and glycerin.

Proper amounts of the above polyol, diisocyanate, and chain extender are blended, and a polyurethane is produced by a known method. Suitable good solvents for polyurethane include dimethylformamide, dimethyl nulphoxide, acetone, dioxane, methyl cellosolve tate, and tetrahydrofuran.

Pore generating agents to be mixed into the polyurethane good solvent solution include polyvinyl fluorol, polyethylene oxide, carboxymethyl cellulose, alginic acid, sodium polyacrylate, ethylene glycol, and polyethylene.
Examples include polysaccharides that are soluble in polyurethane good solvents such as Recoll, diethylene glycol, monoethylene ether, and pullulan.

It is appropriately selected depending on the type of organic solvent and coagulant. Further, the above-mentioned pore-forming agents may be used alone or in combination of two or more.

The amount of the pore forming agent mixed is 1 to 65% by weight, preferably 8 to 30% by weight, based on the total amount of the polyurethane composition. The ring porosity becomes so small that it can hardly be called a porous film, and on the other hand, if the mixing amount exceeds 65% by weight.

The viscosity of the polyurethane composition liquid becomes too high, making it difficult to handle, and the strength of the porous film is significantly reduced.

This invention will be explained in detail below.

Example 1 Manufacture of kanro materials Polyester polyol, ethylene glycol.

A polyurethane solution (solid content: 30% by weight) prepared by dissolving polyurethane made from plp/-cy enylmethane diisocyanate in dimethylformamide.

Product name Hilac 1061. To 945 parts by weight of Toyo Polymer Co., Ltd., 30 parts by weight of dimethylformamide and 25 parts by weight of various pore-forming agents were added and stirred for 20 minutes using a rotary stirrer to completely defoam the mixture to prepare a polyurethane composition. This polyurethane composition liquid is applied onto a base material made of spun fabric.

The coated material is immersed in an 80% by weight dimethylformamide aqueous solution at 25°C to coagulate the polyurethane, and then washed with a large amount of water and added.
fty+ and dried for 5 minutes.

The physical properties of the polyurethane coatings on the sheets with different pore-forming agents obtained as described above are shown in Table 1 below.

(Blank below) Table 1 The dry density in Table 1 is ASTM-D2406-Water content is J.
I5-L1096, pore size is ASTM-F316-
70.

Table 1 Experiment 1f = 2 with a polyurethane coating, and one furnace material for comparison, namely a calendered weft ribbed lubricant, and a calendered needle punched felt furnace material. The physical properties are shown in Table 2.

Table 2 haze The air permeability in Table 2 was measured by applying the Frasil method.

Its units are cc/min/cft. ′! ! : The pore diameter of the present invention (a) is the value measured in the same manner as in Table 1.
The pore diameters of comparative examples (b) and (c) are J Engineering 5-B8356-
It is a measured value of filtration particle size according to 9.12.

(b) Filtration experiment -1,781 for the lubricant in Table 2 above! Attached to +M double-filter filter platene (filtration area 210 x 2 C4, i-frame thickness 13 mm), the entire slurry containing high azo]*H lake red], titanium oxide, and magnetic iron oxide having the weight cumulative particle size distribution shown in Fig. 1 was installed. Filtration was performed under the conditions shown in Table 3 below.

Table 3: The particle size distribution of the particles in the p-liquid filtered from 0 to 30 seconds after the start of filtration was measured using a light transmission method, and the results were reported in Sections 2 and 3.4.
Shown in the figure. As shown in the graph above, in the present invention, particles larger than 0.05 to 0.1 micron do not exist in the filtrate and fine particles are captured, whereas in the case of the conventional ) cannot capture particles smaller than 5 microns in size.

(c) Practical Results Based on the above filtration experiments, the results of practical application of the lp filtration method of the present invention at the Oh Factory are as follows.

High-grade azo pigments were conventionally subjected to Fr filtration using the furnace material of Comparative Example (b), and each time a clear liquid was obtained after forming a cake after 2 hours of prefiltration, and further after 2 hours of Z filtration. The cake was manually peeled off with a spatula, but
In the 7th pass in this invention, a clear liquid was obtained immediately after the first pass, and when the cake was taken out after 2 hours, the cake fell down naturally and did not require all human effort.

Titanium oxide was conventionally sor-filtered using the furnace material of Comparative Example (c), and it took two weeks to reach the required clarity, during which one filtration had to be constantly circulated, and the The peeling of the cake was poor and the amount of processing obtained was reduced.
According to this invention, the required clearness of the quenching solution can be achieved immediately and the cake can be easily peeled off.

The throughput was therefore increased.

For magnetic iron oxide, the furnace material of Comparative Example (c) was used in Oliver filters, which caused severe clogging.

The cake had poor peeling after about 10 days, but according to this invention, the initial activity was maintained even after 30 days of use, and the amount of cake obtained increased from 72% to 88%. did.

[Brief explanation of the drawing]

Figure 1 is a graph of the particle size distribution of fine particles used in the purity experiment, Figure 2 is a high grade azo pigment, Figure 3 is titanium oxide, Figure 4 is
The figure is a graph showing the particle size distribution in each filtrate of one filtration using various types of magnetic iron oxide furnace materials. Patent applicant Shikishima Canvas Co., Ltd. Toyo Polymer Co., Ltd. representative Takeo Sakano Patent attorney Ryoji Yoshida

Claims (1)

[Scope of Claims] [1] Using a furnace material having a polyurethane porous film impregnated or applied to a fiber base material and formed by wet coagulation, a slurry containing fine particles with a particle size of 0.05 to 5 microns is delivered door to door. A method for clarifying and filtrating a slurry containing fine particles, characterized by: [2] A porous film formed by impregnating or coating a fiber base material with a polyurethane or a pore-forming agent that is soluble in a good polyurethane solvent and also soluble in a non-solvent of polyurethane, and formed by wet coagulation. A material for use in refining slurry containing fine particles.