WO2020087686A1 - Method for manufacturing seamless filter bag in one operation - Google Patents

Abstract

A method for manufacturing a seamless filter bag in one operation. The method comprises: (1) mixing a gel precursor, absolute ethanol and distilled water at a mass ratio of 50-80: 10-50: 20-40, adding an acid catalyst to adjust the pH of the mixture to pH 1-3, and thoroughly stirring the mixture until a settled solution is obtained; using a basic catalyst to adjust the pH of the mixture to pH 6-7, continuously stirring the same for 10 minutes, adding a high-temperature-resistant fiber, performing stirring, sealing, aging and standing, removing a supernatant, adding an organic solvent, and performing substitution therewith at 60℃ to obtain a gel; and (2) placing the gel in a mold, pressing the same until a moisture content reaches 5-30%, standing for 12 hours, refilling the mold with the gel, standing for 5-24 hours, removing a resulting product, and drying the same.

Description

Method for preparing one-time forming seamless filter bag Technical field

The invention belongs to the field of filter materials, and relates to a preparation method of a once-formed seamless filter bag.

Background technique

With the progress of society and the development of industry, the requirements for filtration technology in fields such as mining, chemical, food, environmental protection, etc. are getting higher and higher, and the requirements for filter cloths are also getting higher and higher. Processing technology puts forward higher requirements. At present, the tubular filter bags used in the market are first woven out of the base fabric with a loom, the non-woven web is laid flat on the base fabric, reinforced with needle punching or spunlace, and then butted to be sewn into a tubular structure. Not only the processing is time-consuming and laborious, but also the structural performance is not good. At the same time, due to the corrosion of acid gas for a long time, the connection of the filter bag will crack, which will cause the filter bag to fail.

Summary of the invention

The purpose of the present invention is to solve the problem of frequent cracking at the joints of the existing ordinary filter bags, and a method for preparing a once-formed seamless filter bag with high strength, high temperature resistance and not easy to crack under special circumstances .

The object of the present invention is achieved in the following manner:

The preparation method of the once-formed seamless filter bag of the present invention mainly includes the following steps:

(1) The gel precursor, absolute ethanol and water are mixed according to the volume ratio of 55-80: 10-50: 20-40, acidic catalyst is added to adjust the pH = 1-3, and the mixture is evenly mixed to a clear solution; Adjust the pH of the basic catalyst to 7.6-8.5, continue stirring for 8-10 minutes, add high temperature resistant fiber (preferably 3-5g fiber per 100ml of solution), stir until the mixture is uniform, seal, aging for 3-7 days, let stand, Decant the supernatant, add organic solvent, and perform solvent replacement at 60 ℃ -80 ℃ to obtain a gel;

(2) Put the gel in the mold, squeeze it to reach a water content of 5-30%, let stand for 10-12h, and fill the gel again until it fills up the mold, let it stand for 5-24h, and dry.

The above uses acids to catalyze the hydrolysis of the silane precursor, and catalyzes (basifies) the hydrolyzed silane to form a gel. The invention can accelerate hydrolysis in the acidic range of specific PH value; accelerate the gelation speed in the alkaline range of specific pH value.

Preferably, the gel precursor, absolute ethanol and water are mixed in a volume ratio of 55-80: 50: 40.

The steps (1) The gel precursor includes tetraethyl orthosilicate, trimethoxyvinylsilane, and water glass.

The step (1) acidic catalyst is preferably one or more of hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid and the like.

In the step (1), the alkaline catalyst is preferably one or more of ammonia water, sodium hydroxide, sodium carbonate, sodium bicarbonate and the like.

The high temperature resistant fiber includes one or more of high temperature resistant fiber such as polytetrafluoroethylene fiber, polyphenylene sulfide fiber, polyimide fiber, basalt fiber, and alkali-free glass fiber.

The step ⑶ solvent replacement uses solvents including ethanol, n-hexane, acetone, methanol, isooctane and one or more common organic solvents, the appropriate time for each replacement is 1h-12h, preferably 3h-8h, more preferably 5h-7h, the appropriate number of replacements is 1-6 times, preferably 2-5 times, more preferably 3-4 times

The suitable water content of the gel is 5% -30%, preferably 10% -20%, more preferably 15% -16%.

The suitable standing time of the gel is 5h-24h, preferably 10h-15h, more preferably 12h-15h.

The drying methods include drying, freeze drying, supercritical drying and the like.

The suitable temperature for drying is 30 ° C-110 ° C, preferably 50 ° C-90 ° C, more preferably 60 ° C-80 ° C. The suitable drying time is 4h-24h. The freeze-drying time is preferably 20-24 hours.

Compared with the prior art, the beneficial effects of the present invention: most of the tubular filter bags used in the current market first use a loom to weave out the base fabric, lay the nonwoven web formed on the base fabric, and use needle punching Or spunlace reinforcement, and then sew the joint into a tubular structure, the processing process is time-consuming and laborious, and the structural performance is poor. At the same time, because the connection seam of the filter bag is not the same as the fabric, it is particularly susceptible to corrosion by acid or alkaline gas in the exhaust gas. Therefore, the seam is particularly prone to cracking and damage, causing partial damage to the filter bag and failure. . However, the seamless filter bag prepared by the specific material used in the present invention does not have this problem. All materials are uniformly mixed, formed by a mold at one time, and the gel is extruded to a certain range of water content. The material has no joints, can resist the corrosion of external gas, and has a small grammage and high strength. The filter bag has a long service life and is not easily damaged. It can be used normally for more than one year under the working condition of 300 ℃.

BRIEF DESCRIPTION

Figure 1 is a diagram of the mold used in the present invention.

detailed description

The following further describes the present invention through specific embodiments:

Example 1

Add 55 ml of tetraethylorthosilicate to a 250 ml beaker, then weigh 50 ml of absolute ethanol and 40 ml of water with a 100 ml graduated cylinder, mix well, and use a pipette to draw 100 μl of hydrochloric acid to adjust the pH of the solution to 1 -3, cover the above solution with plastic wrap, magnetically stir at 350 rpm for 8 hours to a clear solution, use a pipette to suck 120 microliters of ammonia water, add to the solution, adjust the pH of the solution to 7.6-8.5, continue the magnetic force After stirring for about 8 minutes, the solution becomes viscous, add 3g of polytetrafluoroethylene fiber, mechanically stir until the mixture is uniform, seal the mixed gel with plastic wrap, let it stand in a cool place for 3 days, and clear the supernatant after standing Pour out the liquid, add 100 ml of n-hexane, put it in an oven, and perform solvent replacement at 60 ° C, about 6 hours each time, so that the replacement is repeated 3 times; place the replaced gel in the mold and squeeze the gel in the mold , To reach a moisture content of about 15%, put the product in a cool place and let it stand for 12h; fill the gel again until it fills the mold, without obvious cracks and cracks, put it in a cool place and let it stand for 12h; put the product in the oven, Dry for 12 hours under normal pressure at 60 ℃ Thing.

Example product performance:

Gram weight: 120g / ㎡, thickness: 0.8㎝, longitudinal strength 540N, transverse strength 500N, high temperature resistance 300 ± 20 ℃.

Example 2

Add 80 ml of trimethoxyvinylsilane to a 250 ml beaker, then weigh 50 ml of ethanol and 40 ml of water with a 100 ml measuring cylinder, mix well, and use a pipette to suck up 100 μl of hydrochloric acid to adjust the pH of the solution 1-3, Cover the above solution with plastic wrap, and stir magnetically at 350 rpm for 10 hours; use a pipette to suck up 120 μl of 15% sodium hydroxide, add it to the prepared solution, adjust the pH of the solution to 7.6-8.5, continue Magnetic stirring, after about 10 minutes, the solution becomes viscous, add 3g of basalt fiber, and stir mechanically until the mixture is uniform; seal the mixed gel with plastic wrap and let it stand in a cool place for 3 days; the supernatant after standing Pour out, add about 100 ml of acetone, put it in an oven, and perform solvent replacement at 60 ° C, about 6 hours at a time, so that the replacement is repeated 4 times; place the replaced gel in the mold and squeeze the gel in the mold, When the water content reaches about 15%, the product is placed in a cool place and allowed to stand for 12 hours; the gel is filled again until there are no obvious cracks or gaps in the mold. After placing it in a cool place for 13 hours, it is frozen with liquid nitrogen for 20 minutes. Then put it in the freeze dryer 2 After 4 hours, the mold is released, and the product is obtained.

Example product performance:

Weight: 115g / ㎡, thickness: 0.8㎝, longitudinal strength 550N, lateral strength 500N, high temperature resistance 300 ± 20 ℃.

Example 3

Add 60 ml of water glass to a 250 ml beaker, then weigh 50 ml of ethanol and 40 ml of water with a 100 ml graduated cylinder, mix well, use a pipette to suck up 100 μl of sulfuric acid to adjust the pH value of the solution = 1-3, add the above solution Cover with plastic wrap and stir magnetically at 350 rpm for 10 hours; use a pipette to absorb 120 microliters of ammonia and add it to the prepared solution. Adjust the pH of the solution to 7.6-8.5 and continue magnetic stirring for about 10 minutes After the solution becomes viscous, add 3g of polyphenylene sulfide fiber and stir mechanically until the mixture is uniform; seal the mixed gel with plastic wrap and let it stand for 7 days in a cool place; pour out the supernatant after standing, Add about 100 ml of n-hexane, put it in an oven, and perform solvent replacement at 60 ° C, about 6 hours at a time, so that the replacement is repeated 3 times; place the replaced gel in the designated mold and squeeze the gel in the mold to achieve 16% water content, put the product in a cool place and let it stand for 12h; fill the gel again until it fills up the mold, without obvious cracks, cracks, put it in a cool place and let it stand for 12h, freeze with liquid nitrogen for 20min, and then put Freeze-dry in a freeze dryer for 24 hours, take off , To give the product.

Example product performance:

Weight: 115g / ㎡, thickness: 0.8㎝, longitudinal strength 550N, lateral strength 500N, high temperature resistance 300 ± 20 ℃.

Example 4

Add 55 ml of tetraethylorthosilicate to a 250 ml beaker, then weigh 50 ml of ethanol and 40 ml of water with a 100 ml measuring cylinder, mix well, and use a pipette to draw 100 μl of hydrochloric acid to adjust the pH of the solution = 1-3 , Cover the above solution with plastic wrap, and stir magnetically at 350 rpm for 10 hours; use a pipette to suck up 120 microliters of ammonia water, add it to the prepared solution, adjust the solution pH = 7.6-8.5, continue magnetic stirring After about 10 minutes, the solution becomes viscous, add 3g of alkali-free glass fiber, and stir mechanically until the mixture is uniform; seal the mixed gel with plastic wrap and let it stand for 3 days in a cool place; the supernatant after standing Pour out, add about 100 ml of methanol, put it in an oven, and perform solvent replacement at 60 ° C, about 6 hours at a time, so that the replacement is repeated 3 times; place the replaced gel in the designated mold and squeeze the gel in the mold To reach a water content of about 10%, put the product in a cool place and let it stand for 12h; fill the gel again until it fills up the mold, without obvious cracks and cracks, and put it in a cool place for 14h, then freeze with liquid nitrogen for 20min , And then put into a freeze dryer for freeze drying for 20 hours , Release, i.e. to give the product.

Example product performance:

Weight: 115g / ㎡, thickness: 1㎝, longitudinal strength 550N, lateral strength 500N, high temperature resistance 300 ± 20 ℃.

Example 5

Add 70 ml of tetraethylorthosilicate to a 250 ml beaker, then weigh 50 ml of ethanol and 40 ml of water with a 100 ml graduated cylinder, mix well, and use a pipette to draw 100 μl of hydrochloric acid to adjust the pH of the solution = 1-3 , Cover the above solution with plastic wrap, and stir magnetically at 350 rpm for 10 hours; use a pipette to suck up 120 μl of 15% sodium hydroxide aqueous ammonia, add it to the prepared solution, and adjust the pH of the solution to 7.6- 8.5 Continue magnetic stirring. After about 10 minutes, the solution becomes viscous. Add 3g of polyimide fiber and stir mechanically until the mixture is uniform; seal the mixed gel with plastic wrap and let it stand in a cool place for 3 days; The supernatant after placement was poured out, about 100 ml of methanol was added, placed in an oven, and the solvent was replaced at 60 ° C, about 6 hours at a time, so that the replacement was repeated 3 times; place the replaced gel in the designated mold and squeeze Press the gel in the mold to reach a moisture content of about 15%. Put the product in a cool place and let it stand for 12 hours; fill the gel again until it fills the mold, without obvious cracks or gaps, and put it in a cool place for 12 hours , Freeze with liquid nitrogen for 20min, and then put it into the freeze dryer Freeze dried for 24 hours, demolded, i.e. to give the product.

Example product performance:

Gram weight: 115g / ㎡, thickness: 1㎝, longitudinal strength 500N, lateral strength 450N, high temperature resistance 300 ± 20 ℃.

Claims (9)

1. A method for preparing a once-formed seamless filter bag, characterized in that the method includes the following steps:

   (1) The gel precursor, absolute ethanol and water are mixed according to the volume ratio of 55-80: 10-50: 20-40, add acidic catalyst to adjust the pH = 1-3, stir evenly to a clear solution; use Adjust the pH of the basic catalyst to 7.6-8.5, continue stirring for 8-10 minutes, add high temperature resistant fiber, stir until the mixture is uniform, seal, aging for 3-7 days, let stand, the supernatant is decanted, add organic solvent, at 60 Perform solvent substitution at ℃ -80 ℃ to obtain gel;

   (2) Put the gel into the mold, squeeze to reach a water content of 5-30%, let stand for 10-12h, and fill the gel again until the mold is filled, let stand for 5-24h, and dry.
2. The method for preparing a once-formed seamless filter bag according to claim 1, wherein the gel precursor in step (1) is tetraethyl orthosilicate, trimethoxyvinylsilane, and water glass.
3. The method for preparing a once-formed seamless filter bag according to claim 1, wherein the acidic catalyst in step (1) is one or more of hydrochloric acid, sulfuric acid, nitric acid, and phosphoric acid.
4. The method for preparing a once-formed seamless filter bag according to claim 1, wherein the alkaline catalyst in step (1) is one or more of ammonia water, sodium hydroxide, sodium carbonate, and sodium bicarbonate.
5. The method for preparing a once-formed seamless filter bag according to claim 1, wherein the high temperature resistant fiber is polytetrafluoroethylene fiber, polyphenylene sulfide fiber, polyimide fiber, basalt fiber, alkali-free glass One or more of fibers.
6. The method for preparing a once-formed seamless filter bag according to claim 1, wherein the organic solvent is one or more of ethanol, n-hexane, acetone, methanol, and isooctane, and each replacement time is 1h-12h.
7. A method of preparing a seamless filter bag according to claim 1, characterized in that the water content is 10% -20%, preferably 15% -16%.
8. The method for preparing a once-formed seamless filter bag according to claim 1, characterized in that the rest time is 10h-15h, preferably 12h-14h.
9. The method for preparing a once-formed seamless filter bag according to claim 1, wherein the drying method includes drying, freeze drying, and supercritical drying.

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