JPS6246680B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing an absorbent sheet. Its purpose is to have excellent adsorption performance, heat resistance, solvent resistance, and flame retardancy, as well as to be suitable for processing such as fluting, and to be easy to regenerate adsorption capacity and recover adsorbed substances. An object of the present invention is to provide a very useful method for producing an adsorbent sheet. Another object of the present invention is to provide a sheet that has excellent performance without using asbestos, which has been commonly used in conventional adsorptive sheets of this type, and thereby overcomes the serious drawbacks of asbestos. The aim was to solve various sanitary problems that had arisen. Conventionally, adsorbent sheets made by mixing activated carbon fiber with pulp, rayon, etc. are known, but since these mixed sheets use flammable fibers such as pulp and rayon, there are problems with heat resistance and flame retardancy. In addition, pulp and rayon are highly hygroscopic and require careful attention to drying to remove moisture, making them inconvenient to handle. Furthermore, this mixed sheet had very low strength and poor processability such as fluting, and its uses were limited. As a means of solving this problem, a method of adding a binder to improve processability is commonly used, but this method also has its limitations as described below. There are two types of binders; one is a liquid binder such as a solution type such as polyvinyl alcohol or an emulsion type such as latex, and the other is a fibrous binder such as vinylon fiber. It's a binder. Although high strength can be obtained in the case of a liquid binder, there is a very high probability that the binder will block the pores of the activated carbon fibers, and therefore it is difficult to obtain a high adsorption capacity. In addition, fibrous binders have a lower probability of clogging the pores of activated carbon fibers than liquid binders, making it easier to obtain relatively high adsorption capacity, but there are only a few types of binders, such as the most commonly used fibrous binders. Vinylon fiber is used as a binder, but it has extremely poor hot water resistance, making it impossible to use water vapor to recover the solvent, and methods for recovering it are also limited.
As a result, it was concluded that it is inappropriate as a binder for adsorbent sheets. In addition, cationic inorganic fibers such as asbestos fibers have very small fiber diameters and large surface areas, so it is being developed to take advantage of this and combine them with activated carbon to make adsorption sheets. It has the disadvantage of being unhygienic, so it is desirable to avoid using it as much as possible. With the above points in mind, the present inventor conducted extensive research to obtain an absorbent sheet that has high adsorption performance, excellent heat resistance and processability, and can be used with a small amount of binder.As a result, the present inventor has developed the present invention. It was reached. i.e. 90-50% activated carbon fiber and 10-50%
A dispersion slurry containing a heat-resistant synthetic pulp as an essential component and 50 parts by weight or less of an agglomerated binder per 100 parts by weight of fibers as the essential component is mixed into a paper by a wet paper-making method. This led to the invention of a method for manufacturing sheets. The present invention will be explained in detail below. Activated carbon fiber, which is one of the essential components in the present invention, is made from natural cellulose fibers such as silk, hemp, and ramie, polyvinyl alcohol fibers, acrylic fibers, aromatic polyamide fibers, etc., and is carbonized and activated. It is something. Heat-resistant synthetic pulp, which is another essential component in the present invention, is made by dissolving a so-called heat-resistant polymer, such as aromatic polyamide or wholly aromatic polyester, in a suitable solvent, and then combining the solvent and water. It is a fine pulp-like particle obtained by injecting it into a mixed solution while stirring. In general, synthetic pulps are broadly classified into polyolefin-based pulps such as polyethylene and polypropylene, and heat-resistant pulps such as the above-mentioned aromatic polyamides and wholly aromatic polyesters. However, since the former has a melting point in a low temperature range, it has poor heat resistance and flame retardancy, and when used in the present invention,
When the temperature rises above this melting point, the olefinic polymer melts and solidifies, closing the pores of the activated carbon fibers and impairing the high adsorption capacity. Therefore, in the present invention, polyolefin-based synthetic pulps are excluded, and only heat-resistant synthetic pulps are suitable essential components. Currently, this heat-resistant synthetic pulp is only used as heat-resistant synthetic insulating paper by mixing it with heat-resistant synthetic fibers, mica, etc., taking advantage of its excellent heat resistance and electrical insulation properties. It's not being used in any way. The present invention focuses on the fact that this heat-resistant synthetic pulp has excellent heat resistance, solvent resistance, and flame retardancy, and that the heat-resistant synthetic pulp itself is strongly intertwined with each other or with other fibers. However, various experiments were conducted with the idea of mixing this with the activated carbon fiber. The blending ratio of activated carbon fiber and heat-resistant synthetic pulp, which are essential components, is required to be 90-50% for the former and 10-50% for the latter. In other words, if the total of essential components is 100 parts by weight, the activated carbon fiber will be 90 to 50 parts by weight, and the remaining 10 to 50 parts by weight will be the heat-resistant synthetic pulp. If the ratio of activated carbon fiber exceeds 90%, the strength of the obtained sheet will be weak and it will be difficult to maintain the shape, making it unsuitable.
If the ratio is less than that, the adsorption performance will deteriorate, which is not preferable. In the production method of the present invention, activated carbon fibers are first added to water in the above ratio and dispersed by disintegrating and stirring, then heat-resistant synthetic pulp is added in the above ratio and stirred, and other additives are added and mixed. A 3% dispersion slurry is obtained. Then, this dispersed slurry is mixed and paper-made using a wet paper-making method, for example, by hand, a Fourdrinier paper machine, a circular wire paper machine, etc., and then dried to obtain a sheet. In addition to the cohesive binder described below, these additives include the addition of agents to obtain uniform dispersion, such as polyethylene oxide, sodium polyacrylate, etc., and the addition of agents to increase the dimensional stability of the obtained sheet. 2-4% of essential ingredients
Contamination with glass fiber, etc. In the present invention, the agglomerated binder refers to water-soluble cationic polymers, polyvalent metal salts, etc. added to anionic polymer emulsion such as rubber latex while stirring.
Or, it is an aggregate with a particle size of about 10μ or more obtained by adding an inorganic binder or the like. This kind of agglomerated binder with a relatively large particle size is completely different from ordinary emulsion-type or solution-type binders, and even if used in a fairly large amount, the probability of blocking the pores of activated carbon fibers is small, so it is possible to obtain a good profit. The resulting sheet maintains excellent adsorption capacity. In addition, this cohesive binder is not limited in type like ordinary fibrous binders; for example, vinylon fibers have the disadvantage of poor hot water resistance, but this cohesive binder can be used with various binders. A combination of these is also possible, and one with excellent hot water resistance can also be selected. In particular, the advantage obtained by using this agglomerated binder is that the product sheet has extremely high bending resistance, and therefore has excellent processing suitability for fluting and the like. The amount of this agglomerated binder added is 50 parts by weight or less per 100 parts by weight of the activated carbon fiber and heat-resistant synthetic pulp, which are essential components. The ratio becomes smaller, and the probability of blocking the pores of activated carbon fibers by this agglomerated binder also increases.
The adsorption performance deteriorates, making it unsuitable. Next, in the production method of the present invention, if the dispersed slurry is mixed into paper by a wet paper-making method, and then dried and then subjected to heat and pressure treatment, a sheet with even better strength can be obtained. For example, by setting the mixed paper according to the present invention at a temperature higher than the glass transition point of heat-resistant synthetic pulp and further applying pressure, the entanglement with the heat-resistant synthetic pulp itself and activated carbon fibers becomes strong, impairing the adsorption performance. Excellent strength can be obtained without any problems. As described above, the present invention provides a method for producing an adsorbent sheet containing activated carbon fibers and heat-resistant synthetic pulp as essential components, adding an agglomerated binder with a relatively large particle size, and mixing the mixture into paper by a wet paper-making method. The resulting product sheet has excellent adsorption performance, heat resistance, solvent resistance, flame retardancy, and processing suitability, making it suitable for steam regeneration treatment and recovery of adsorbed substances. It is easy to flute and is an extremely useful adsorbent sheet. Furthermore, since the method of the present invention does not use asbestos, there are no hygiene problems, and since it can be manufactured with a small amount of binder, it is possible to provide flame retardance close to non-combustibility. Examples will be described below, but the present invention is not limited to these examples in any way. Example 1 70 parts by weight of activated carbon fibers were stirred and disintegrated in water,
Heat-resistant synthetic pulp (Cornetx manufactured by Teijin Ltd.)
30 parts by weight was added to adjust the total slurry concentration to about 2.5%, and a sheet was hand-sheeted and dried. However, this Example 1 was conducted in order to obtain comparative data when no agglomerated binder was contained. Example 2 After dispersing the essential components with the same composition as in Example 1, 10 parts by weight of the following cohesive binder was added,
A slurry dispersion of approximately 2.5% was prepared, and a sheet was hand-printed and dried. Agglomerated binder...5% by weight of 10% by weight acrylic resin emulsion liquid while stirring at 2000rpm
The aggregates were adjusted by gradually adding sulfuric acid solution. Example 3 After dispersing the essential components having the same composition as in Example 1, 20 parts by weight of the same agglomerated binder as in Example 2 was added, and the sheet was hand-sheeted and dried in the same manner. Example 4 After dispersing the essential components with the same composition as in Example 1, 40 parts by weight of the following cohesive binder was added,
A dispersion slurry of approximately 2.5% was prepared, hand-sheeted and dried to obtain a sheet. Agglomerated binder...5% by weight of 10% by weight vinyl chloride emulsion liquid while stirring at 2000 rpm.
The agglomerates were adjusted by gradual addition of sulfuric acid. Comparative example 70 parts by weight of activated carbon fibers were stirred and disintegrated in water.
Add 30 parts by weight of beaten NBKP to SR12°,
Furthermore, vinylon fiber is added to 100 parts by weight of the above base material.
Add 10 parts by weight and mix and disperse to reduce the wet paper moisture to 60 parts by weight.
% and press dried to obtain a handmade sheet. When various data were measured for the above Examples 1 to 4 and Comparative Examples, the results shown in the following table were obtained.

[Table] Hot water resistance test...Does the sheet break after being immersed in hot water at 100°C for 30 minutes?How to determine the amount of adsorption...Accurately weigh approximately 0.15g of sample whose area has been determined, and measure 0.025 normal iodine-potassium iodide. After soaking in 50 ml of aqueous solution and shaking for 1 hour, 25°C
The adsorption reaction was left in a constant tank for 40 hours to reach equilibrium, and titrated using a 0.01N sodium thiosulfate aqueous solution. The adsorption amount (%) was determined from the amount of adsorbed iodine molecules and the weight and area of the sample. The adsorption amount/sample weight) and the adsorption amount (g) of iodine molecules per 1 m ² of the sample were determined. As can be seen from this table, the sheet according to the present invention has excellent adsorption performance, hot water resistance, and flame retardancy, and the sheet containing an agglomerated binder has excellent strength while maintaining the above-mentioned excellent properties. It is in good condition.

Claims (1)

[Scope of Claims] 1. 90 to 50% activated carbon fiber and 10 to 50% heat-resistant synthetic pulp as essential components;
A method for producing an adsorbent sheet, which comprises mixing and paper-making a dispersion slurry containing 50 parts by weight or less of an agglomerated binder per 100 parts by weight using a wet paper-making method. 2 Claim 1 of heating and pressurizing after paper mixing
A method for manufacturing an adsorbent sheet as described in Section 1.