JP2888743B2 - Silica gel aggregate and its production method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a silica gel aggregate in which silica gel is bonded to each other.

[0002]

2. Description of the Related Art As is well known, silica gel has an infinite number of pores and is excellent in the property of adsorbing and desorbing various substances including water, and therefore, absorbs a carrier such as a desiccant or an aromatic agent. It is used as a desorbing agent.

Conventionally, when silica gel is used as a desiccant, for example, granular silica gel has been put in a container such as a bag or box to prevent dispersion of the silica gel. Further, in order to eliminate such a means for preventing dispersion, it has been proposed to bond and mold silica gel in powder form with an adhesive.

[0004]

However, in the above-mentioned molded article, since the surface of the silica gel is covered with a binder for binding the silica gel to each other and pores of the silica gel are closed (FIG. 1 (b)). ), The adsorption / desorption performance of silica gel was sometimes reduced.

[0005]

According to a first aspect of the present invention, there is provided a method for producing a silica gel aggregate comprising the steps of :
Dry mix silica gel and powdery binder,
Add the binder solvent to the mixture of Rica gel and binder
Mixed or kneaded, and the above mixed or kneaded
A method for producing a silica gel aggregate to be converted, wherein the solvent is
In addition, in the step of mixing or kneading the above binder
By keeping fine particles without completely dissolving,
The silica gel particles are bonded via the granular binder.
It is characterized by Silica gel assembly according to claim 2
The method for producing the body is the same as the method for producing the silica gel aggregate according to claim 1.
The above-mentioned binder is used for 80 parts by weight of the above silica gel.
The weight is set to 20 parts by weight or less. Claim 3
The method for producing the silica gel aggregate according to claim 1 or 2
In the method for producing the silica gel aggregate described above,
It is characterized by being water-soluble.

[0006] The silica gel aggregate according to claim 4 is characterized in that
It was manufactured by the manufacturing method according to any one of Items 1 to 3.
By this, a large number of silica gel particles
And the surface of the silica gel particles
Having an area not covered by the binder
It is characterized by the following. The silica gel aggregate according to claim 5.
Is the surface of the silica gel aggregate according to claim 4,
Characterized by partially disposing cobalt chloride-containing silica gel
And

[0007]

The silica gel aggregate according to claim 4 is first described.
To explain, in this silica gel aggregate, many silica gel particles are bonded to each other via a binder.
Because the binder is in a fine granular form, there is a region on the surface of the silica gel particles that is not covered by the binder.
In this region, the openings of the pores of the silica gel particles are not closed by the binder. Therefore, the adsorption / desorption function is maintained in the above-mentioned region of each silica gel particle, and the silica gel aggregate can exhibit a sufficient adsorption / desorption function.

Further, when the silica gel containing cobalt chloride is disposed on a part of the surface, the discoloration of the cobalt chloride caused by the well-known moisture absorption can indicate the moisture absorption of the silica gel aggregate. The shape and size of the cobalt chloride-containing silica gel and the distribution on the surface of the silica gel aggregate are not particularly limited. For example, 2mm to 10m in diameter
The visibility becomes good when it is a polyhedron such as a bead shape or a dice shape of about m. Also, even if dispersed over the entire surface,
One or more can be concentrated on a specific portion.

Next, a silica gel assembly according to any one of claims 1 to 3.
The body manufacturing method will be described in detail. The silica gel used in this production method is not particularly limited as long as it is in a powder form. The shape of each silica gel is not particularly limited, and it can be used in a well-shaped shape such as a spherical shape or in an irregular shape by crushing or the like. The particle size of the powdered silica gel may be appropriately selected depending on the use of the silica gel aggregate and the like. The same applies to the pore volume. The smaller the particle size of the silica gel, the better the moldability of the kneaded material described later,
The particle size of the silica gel is preferably 1 mm or less, more preferably 100 μm or less.

The binder that can be used in the present invention is not particularly limited as long as it is soluble in a solvent such as water or alcohol and becomes viscous when dissolved. Examples of such a binder include polyvinyl alcohol, partially saponified polyvinyl acetate, and water-soluble cellulose esters. These are all water-soluble and soluble in alcohol. Note that, in consideration of kneading and molding described below, a binder having a high solvent retention performance and a shape retention property that is good enough not to lose its shape by extrusion or the like is preferable.
From these points, the above-mentioned polyvinyl alcohol, partially saponified polyvinyl acetate, and water-soluble cellulose esters are also excellent.

[0011] The binder needs to be in the form of powder like silica gel in order to uniformly dry mix the powder with silica gel. When the particle size of the binder is increased, the ratio of the interface of the silica gel covered with the binder increases, and therefore, the smaller the particle size of the binder is, the better the particle size of the silica gel is.

When the mixing ratio of the binder is increased, the mechanical strength of the silica gel aggregate is increased, but the ratio of the interface of the silica gel covered with the binder is also increased. Therefore, the mixing ratio of the binder is 50 parts by weight of the silica gel. Is preferably 50 parts by weight or less (50% or less of the weight of the mixture). 2 binders per 80 parts by weight of silica gel
When the content is 0 part by weight or less (20% or less of the weight of the mixture), the adsorption and desorption performance of the silica gel aggregate becomes particularly good. However, just because the mixing ratio of the binder slightly exceeds 20% does not mean that the adsorption / desorption performance of the silica gel aggregate is suddenly reduced.

The method of dry-mixing the silica gel and the binder is not particularly limited, and any well-known powder / powder mixer can be used, and if it is a small amount, it can be mixed using a container such as a mortar. . The solvent to be added to the mixture of the silica gel and the binder may be selected according to the binder, and is not particularly limited. Solvents applicable to a wide range of binders include water and alcohol. Alcohols having a high molecular weight are difficult to penetrate into the pores of silica gel and are preferable in this respect, but the solubility of the binder may be reduced. For this reason, methyl alcohol, ethyl alcohol, isopropyl alcohol and the like are preferable. In consideration of safety, ease of handling, cost, and the like, the combination of a water-soluble binder and water is excellent.

By mixing or kneading the mixture to which the above-mentioned solvent has been added, the solvent is homogeneous throughout the entire mixture. The mixing or kneading may be performed as long as the entire mixture is substantially homogeneous, and the method may be appropriately selected. For kneading, it is convenient to use, for example, a roll kneader. Also, when screw extrusion molding is employed in molding to be described later, a kneading effect can be obtained by pushing with the screw, so that only mixing is sufficient.

The proportion of the solvent varies depending on the kind of the binder, etc., but if the amount of the solvent is large, the viscosity of the kneaded mixture is reduced to deteriorate the moldability, or the silica gel aggregate becomes insufficient in strength. There is. If the amount of the solvent is small, the viscosity of the kneaded material may be increased to lower the moldability, or the silica gel aggregate may become brittle. In addition,
When the solvent is added and mixed or kneaded, the binder does not completely dissolve and keeps fine particles, and the silica gel particles are bonded via the granular binder, so the surface of the silica gel is coated with the binder It is considered that an area that has not been set is secured (see FIG. 1C).
Therefore, when mixing or kneading by adding a solvent,
It is necessary to keep fine particles without completely dissolving the
And is essential. Therefore, the proportion of the solvent
Need to be appropriate depending on the nature of the binder
Yes, it is desirable to be determined by experiments and the like.

A mixture or kneaded mixture of silica gel, a binder and a solvent is solidified to form a silica gel aggregate. This solidification is achieved by drying the kneaded material, but it can be formed into an arbitrary shape, for example, a plate, a column, a ring, a honeycomb, or the like, before drying. As a molding method, for example, press molding, extrusion molding, injection molding, or the like can be adopted, but it is not limited thereto. After the silica gel aggregate is solidified, it can be formed into a desired shape by press punching or cutting.

Since the solubility of water-soluble cellulose increases below 20 ° C., when the temperature of the mixture or kneaded material is maintained at 20 ° C. or lower, preferably 16 ° C. or lower when the water-soluble cellulose is used as a binder, the above-mentioned moldability is improved. I do.
In addition, silica gel containing cobalt chloride is mixed in powdery silica gel as a raw material, and a silica gel aggregate having cobalt chloride-containing silica gel disposed on the surface can be produced. Also, after molding as described above, bead-like or polyhedral-containing cobalt chloride-containing silica gel is pressed into the surface portion and then solidified, whereby a silica gel aggregate having bead-like or polyhedral-like cobalt chloride-containing silica gel disposed on the surface is obtained. Can be manufactured.

As described above, in the present invention, powdery silica gel and a powdery binder are dry-mixed, a solvent is added to the mixture of the silica gel and the binder, and the mixture is mixed or kneaded. The solidified material is solidified, so that only a very small area of the silica gel interface is covered with the binder, and pores existing in other areas are not blocked. Therefore, the adsorption / desorption function is maintained at most of the interface between the silica gels, and the silica gel aggregate can exhibit a sufficient adsorption / desorption function.

[0019]

Next, embodiments of the present invention will be described. (Example) Silica gel in powder form (100 mesh pass)
100 parts by weight and 10 parts by weight of powdery methylcellulose (100 mesh pass) are charged into a mixer and sufficiently stirred.
Mix to form a mixture.

Next, 60 parts by weight of ion-exchanged water was added to the mixture and kneaded with a three-roll kneader. The roll temperature during kneading was maintained at 10 to 15 ° C. further,
The kneaded material obtained above was put into an extruder and extruded at a temperature of 10 to 20 ° C. to form a strip.

The strip was subjected to preliminary drying at 60 ° C. for 10 minutes and main drying at 120 ° C. for 30 minutes to solidify to obtain a plate-like silica gel aggregate. Comparative Example The same kind of silica gel as used in the above example was kneaded with an adhesive, molded, and then solidified to produce a plate-like silica gel aggregate similar to the example.

The raw material silica gels of the examples and the comparative examples and the silica gel aggregates of the examples and the comparative examples at 20%, 50% and 90% relative humidity were measured for the moisture absorption rate, and the moisture absorption performance was compared. It was as follows. In addition,

[0023]

(Equation 1)

[0024]

(Equation 2)

## EQU1 ##

[0026]

[Table 1]

As is clear from Table 1, the silica gel aggregate of the example shows only a slight decrease in performance as compared with the raw material silica gel, and the pores of each silica gel particle constituting the silica gel aggregate have a small pore size. It turns out that it is not blocked.

[0028]

As described above, according to claim 4 or 5,
In the described silica gel aggregate, the pores are not closed in a region that is not covered by the binder on the surface of the silica gel particles, so that the adsorption and desorption performance of the silica gel particles does not decrease in this region, and the silica gel aggregate has sufficient adsorption and desorption performance. Can be demonstrated.

Further, according to the production method of the first to third aspects, it is possible to produce a silica gel aggregate having sufficient adsorption / desorption performance.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram schematically comparing a silica gel aggregate of the present invention with a silica gel aggregate of the prior art, and FIG.
(A) Schematic diagram of silica gel as a raw material, Fig. 1 (b)
FIG. 1 is a schematic diagram of a silica gel aggregate according to the related art, and FIG. 1C is a schematic diagram of a silica gel aggregate according to the present invention.

Continuation of front page (58) Field surveyed (Int.Cl. ⁶ , DB name) C01B 33/00-33/193 B01J 20/10

Claims (5)

(57) [Claims] 1. A powdery silica gel and a powdery binder
And dry-mixing to obtain a mixture of the above silica gel and binder.
Add the binder solvent to the mixture and mix or knead.
Or production of silica gel aggregate to solidify the kneaded material
A law, in the above-described step of mixing or kneading by the addition of the solvent
It does not completely dissolve the binder and keeps fine particles.
With the above, the silica gel particles are interposed through the granular binder.
Of silica gel aggregates characterized by joining
Law. 2. The above silica gel (80 parts by weight )
Claims characterized in that the binder is not more than 20 parts by weight.
Item 4. The method for producing a silica gel aggregate according to Item 1. 3. The method according to claim 2, wherein the binder is water-soluble.
The silica gel aggregate according to claim 1 or 2,
Law. 4. The method according to claim 1, wherein
Produced by a large number of silica gel particles
Are bonded via the granular binder, and the surface of the silica gel particles is covered with the binder.
Silica gel characterized by having untreated areas
Aggregation. 5. A silica gel containing cobalt chloride on a part of the surface.
5. The silica gel according to claim 4, wherein
Aggregation.