JPS6150492B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing an absorbent sheet. More specifically, by holding the powder of an adsorbent material (hereinafter referred to as "adsorbent") such as activated zeolite on a porous sheet with an adhesive without reducing its adsorption performance, the adsorbent powder The purpose of the present invention is to provide a new method for manufacturing an excellent adsorbent sheet that can fully exhibit the adsorption performance of the above. Adsorbents such as activated zeolite, activated carbon, activated alumina, acid clay, and diatomaceous earth have extremely fine porous structures on their surfaces, so they have excellent adsorption ability, and are used in various industries, including the chemical industry. It is widely used for industrial and household purposes.
For industrial use, adsorbents are mainly used in the form of powder or granules, and are adsorbed and regenerated using large-scale adsorption towers, treatment tanks, or filters. On the other hand, when used in fields that do not require such large-scale processing, such as gas absorption filters for air conditioning, gas absorption masks, or deodorizing insoles for shoes, it is inconvenient to handle in powder or granular form. Since this is not practical, it is known to retain a powdered or granular adsorbent on or within a porous sheet such as a nonwoven fabric or a foam sheet and use it as an adsorbent sheet. The method for obtaining such an adsorbent sheet is as follows: (a) The adsorbent powder is sandwiched between the fibrous sheets and needle punched to entangle the fibrous sheets to hold the adsorbent powder. (b) A method of retaining the absorbent powder by encapsulating the absorbent powder in a fibrous sheet containing low melting point fibers and heat treating the surface of the low melting point fibers to melt the surface of the low melting point fibers; Conventionally, methods have been known in which absorbent powder is dispersed in an aqueous solution of a water-soluble polymer such as methyl cellulose or PVA (polyvinyl alcohol), and a porous sheet is impregnated with this aqueous solution to retain the absorbent powder in the porous sheet. However, with these methods, the fixation of the absorbent powder in the porous sheet is insufficient, the powder may fall off due to bending or vibration, or the absorbent powder may be washed away by water, etc. It was difficult to use under conditions where it was bent or exposed to water, and it also had the disadvantage of poor durability.Also, it was difficult to hold a large amount of absorbent powder firmly in a porous sheet. As a method for manufacturing a flexible absorbent sheet with excellent flexibility and flexibility, a method is known in which adsorbent powder is dispersed in an adhesive such as latex, and this dispersion is impregnated into a porous sheet and hardened. However, this method has the disadvantage that the adhesive partially covers the surface of the adsorbent and blocks many of its micropores, resulting in a significant drop in adsorption performance. The inventors have studied various methods of manufacturing an absorbent sheet that take advantage of the advantages of the adhesive fixing method while at the same time hardly reducing the original adsorption performance of the absorbent sheet. By pre-coating the surface of the adsorbent powder with a water-soluble polymer aqueous solution, it is possible to avoid substantial contact with the adsorbent surface of the adhesive that will be mixed later, thereby preventing the adsorbent from coming into contact with the adsorbent surface. It was discovered that the surface of the powder is no longer directly covered with adhesive, and therefore the adsorbent powder can be firmly held on the porous sheet without reducing the adsorption performance of the adsorbent, and the present invention has been developed based on this finding. That is, in the present invention, the surface of an adsorbent powder is coated in advance with a water-soluble polymer aqueous solution, the adsorbent powder is mixed with an adhesive, and this mixed solution is applied or impregnated onto a porous sheet. This is a method for producing an adsorbent sheet, characterized in that adsorbent powder is adhered to and supported on a porous sheet by, for example, drying.The adsorbent used in the present invention includes activated zeolite, activated carbon, There are activated alumina, acid clay, diatomaceous earth, etc., and these have active surfaces, fine porous structures, and extremely large surface areas. These adsorbents can be used alone or in combination of two or several types. Further, the particle size of the adsorbent powder is not particularly limited, but the smaller the particle size, the higher the adsorption capacity per unit weight, so the particle size is preferably smaller than 60 mesh. In the form of an aqueous solution, the water-soluble polymer used in the present invention functions as a dispersion medium for the adsorbent powder and as a protective colloid that coats the surface. Any material that does not impair the air permeability of the surface of the powder may be used. Examples of such water-soluble polymers include cellulose-based water-soluble polymers such as carboxymethyl cellulose, alkyl cellulose, hydroxyalkyl cellulose, and sodium salt of carboxymethyl cellulose. Examples include polymers and water-soluble polymers such as sodium alginate, starch and its derivatives, and polyvinyl alcohol. The amount of water-soluble polymer added to the adsorbent powder varies depending on the type of water-soluble polymer, but it is 0.2
The range is preferably 10.0% by weight. To coat the surface of the adsorbent powder with a water-soluble polymer in advance, the adsorbent powder, water-soluble polymer, and water may be kneaded, or the adsorbent powder may be poured into an aqueous solution of the water-soluble polymer and coated with strong shearing force. There are methods of uniformly dispersing or spraying a water-soluble polymer aqueous solution onto the surface of the adsorbent powder, but in short, as long as the surface of the adsorbent powder is uniformly coated with the water-soluble polymer. However, any method may be used. just,
It is preferable to adjust the amount of water added so that the viscosity is 5,000 to 100,000 centipoise, since the processability in the process of coating or impregnating a porous sheet, which will be described later, is good. Adhesives used in the present invention include synthetic rubber latexes such as chloroprene, NBR, and SBR, which are generally water resistant, have high strength, and are easily flexible, and synthetic resin emulsions such as polyacrylic esters and polyurethane. It is preferable to use them alone or in a mixture, but other emulsions can also be used. The amount of adhesive added to the adsorbent is 10 to 150% by weight, preferably 30 to 100% by weight. If the amount of adhesive is less than 10% by weight, the binding force of the adsorbent powder to the porous sheet will not be sufficient, and powder will fall off due to vibration or bending, which is not practical. On the other hand, if the amount of adhesive exceeds 150% by weight, the voids in the porous sheet will decrease, impairing the air permeability and lowering the adsorption capacity, which is not preferable. Porous sheets used in the present invention include fibrous sheets, synthetic resin foams, and the like. Fibrous sheets include nonwoven fabrics, woven fabrics, knitted fabrics, etc. made of natural, recycled or synthetic fibers, or inorganic fibers.
If it is porous, it may be subjected to resin impregnation treatment or the like. Further, the synthetic resin foam is, for example, a polyurethane foam, and a foam having open cells is preferable. It is preferable that these are appropriately selected and used depending on the intended use. A mixed solution of adsorbent powder and adhesive coated in advance with a water-soluble polymer aqueous solution is applied to a porous sheet by coating, impregnating, spraying, etc., and then heated to 80 to 150°C by means such as a dryer. The adsorbent powder is firmly attached to the sheet. At this time, the water-soluble polymer aqueous solution that coats the surface of the adsorbent powder has stronger hydrophilicity and higher viscosity than the adhesive, so the water evaporation rate due to drying and the water-soluble polymer Comparing the gelatinization rate and the coagulation rate of the adhesive, it is inferred that the coagulation rate of the adhesive is faster than that of the water-soluble polymer aqueous solution. without directly coating the surface.
Since the adhesive exists with respect to the adsorbent powder through a layer of water-soluble polymer having porous voids, it is thought that the adsorption performance of the adsorbent will not be reduced. Also, the adhesive can be heated to 35~60℃
If measures are taken to solidify at temperatures as low as This can be avoided reliably, and an adsorption sheet with better adsorption performance can be obtained. Furthermore, the mixture of the adsorbent powder coated with the water-soluble polymer and the adhesive is foamed within 10 times to further increase the porosity of the mixture, and then applied to or impregnated onto the porous sheet. In this case, an adsorbent sheet with even higher air permeability can be obtained. According to the method for producing an adsorbent sheet of the present invention, one of the features is that a large amount of adsorbent powder can be fixed to the porous sheet, but the solid amount of the adsorbent powder relative to the weight of the porous sheet is is not particularly limited. For applications where bending or vibration is applied, such as air conditioning filters, shoe insoles, futon sheets, etc., it is preferable to use less than 10 times the amount, but most of the time it is used in a static state. For example, the lining of a chest of drawers or a locker,
For purposes such as closet wallpaper, there is no practical problem even if it is used at 10 times the amount or more. Hereinafter, the method for manufacturing the adsorbent sheet of the present invention will be explained with reference to Examples, and a comparison with the conventional technology will be clarified using tables. Example (1) 100 parts of activated zeolite powder (100 mesh pass) was uniformly dispersed in advance in 150 parts of a 1% sodium salt aqueous solution of carboxymethyl cellulose, and then a polyacrylic acid ester emulsion (solid content 45%) was added to this dispersion. Adjust the mixture by adding 220 parts. Needle punched felt made of polyester fiber and rayon fiber is impregnated with polyacrylic acid ester emulsion and hardened.Weight 100
g/ ^m2 dry nonwoven fabric (binder ratio 30%) was coated with the above mixture and dried at 120℃ in a dryer.
After drying for 30 minutes, an adsorbent sheet with a total weight of 1100 g/m ² on which 500 g/m ² of zeolite powder was fixed was obtained. Example (2) 100 parts of activated zeolite powder (100 mesh pass) was uniformly dispersed in advance in 150 parts of a 1% sodium salt aqueous solution of carboxymethyl cellulose, and then 220 parts of a heat-sensitive emulsion of the following polyacrylic ester was added to this dispersion. to prepare a mixed solution. Then, the same nonwoven fabric sheet as in Example 1 was coated with the mixed solution,
The emulsion was thermally coagulated at 45° C. and then dried in a dryer at 120° C. for 30 minutes to obtain an adsorbent sheet with a total weight of 1100 g/m ² on which 500 g/m ² of zeolite powder was fixed. Heat-sensitive formulation Polyacrylic acid ester emulsion 45 parts (solid content 45%) Nonionic activator (cloud point 45°C) 4 parts Coagulant (magnesium chloride) 5 parts Water 46 parts Example (3) Activated carbon (60 mesh pass) 100 1% carboxymethylcellulose aqueous solution, and then 180 parts of NBR latex (solid content 45%) is added to this dispersion to prepare a mixed solution. The above mixture was soaked in a raised fabric made of 100% cotton weighing 200 g/m ² and dried at 140°C in a dryer.
After drying for 30 minutes, an adsorbent sheet with a total weight of about 900 g/m ² on which 400 g/m ² of activated carbon powder was fixed was obtained. When this sheet was cut into a standard shape and wrapped in mesh and used as a shoe insole, no powder was shed and the deodorizing effect lasted for a long time. Comparative Example (1) 100 parts of activated zeolite powder (100 mesh pass), 150 parts of a 1% sodium salt aqueous solution of carboxymethyl cellulose, and 220 parts of polyacrylic acid ester emulsion (solid content 45%) were mixed simultaneously,
This mixed solution was coated on the same nonwoven fabric sheet as in Example 1, and dried for 30 minutes in a dryer at 120°C to create an adsorbent sheet containing 500 g/m ² of zeolite powder. Comparative Example (2) 100 parts of activated zeolite powder (100 mesh pass) was mixed with polyacrylic acid ester emulsion (solid content
This dispersion was coated on the same nonwoven fabric sheet as in Example 1 and dried for 30 minutes in a dryer at 120°C.
An adsorbent sheet with zeolite powder of g//m ² fixed thereon was prepared. Among the absorbent sheets prepared in this way, those according to Examples (1) and (2) and Comparative Examples (1) and (2) were
Cut into 10×20cm squares (contains 10g of zeolite)
Pour into a 500ml Erlenmeyer flask and add concentrated ammonia water (28ml
%) was added dropwise and the Erlenmeyer flask was sealed.
After allowing the flask to stand at room temperature for a certain period of time until the ammonia was completely gasified, the adsorption performance of the adsorbent sheet was determined by comparing the amount of residual ammonia gas in the flask by smell. The results of this measurement method performed several times are summarized in the table. For reference purposes, samples containing only 10 g of zeolite powder and samples containing no adsorbent were also measured.

【table】

[Table] As is clear from the above description, according to the method for producing an adsorbent sheet of the present invention, a large amount of adsorbent can be contained in a porous sheet, and its adsorption performance is hardly reduced. This makes it possible to produce an excellent adsorbent sheet that does not cause any damage. The adsorbent sheet produced by the method of the present invention can be used for gas masks, air conditioning gas filters,
It can be used for purposes such as deodorizing insoles, deodorizing sheets for hospitals, deodorizing sheets for chests of drawers and closets, and wallpaper for closets, making it an ideal adsorbent sheet for fields that require flexibility.

Claims (1)

[Claims] 1. After the surface of the adsorbent powder is coated with a water-soluble polymer aqueous solution in advance, this adsorbent powder is mixed with an adhesive, and the mixed solution is applied or impregnated onto the porous sheet to form a porous sheet. A method for producing an adsorbent sheet, characterized in that an adsorbent powder is attached and supported on the adsorbent sheet.