JP7606687B2 - Water vapor adsorbent, dehumidifier, and dew condensation prevention agent - Google Patents

Description

The present invention relates to water vapor adsorbents, dehumidifiers, and condensation prevention agents.

Porous inorganic materials with nano-sized pores can adsorb various substances based on their unique microstructure. In particular, because porous inorganic materials have the ability to adsorb water vapor, they are expected to be used in applications such as dehumidifiers, condensation prevention agents, and autonomous humidity control materials.

To prevent condensation, the dew point temperature of the air around the cold/warm part must be lower than the cold/warm part temperature, since condensation occurs around the cold/warm part. For this reason, there was a demand for an adsorbent material to be used to prevent condensation that can exhibit sufficient water vapor adsorption performance in high humidity conditions, from medium to high humidity.

In the above context, the inventor of the present invention (the present inventor) has been developing a high-performance water vapor adsorbent capable of absorbing and releasing moisture over a wide range of humidity levels in order to improve its performance as a dehumidifier, and has discovered, for example, a material made of a complex of amorphous aluminum silicate and low-crystalline layered clay (see Patent Document 1), or a material made of amorphous aluminum silicate (see Patent Document 2).

Specifically, the substances containing amorphous aluminum silicate described in Patent Documents 1 and 2 are inorganic materials that have a moisture absorption and desorption amount of about 30 wt% at a relative humidity of 10-60%, and show a linear relationship between the relative humidity and the amount of water vapor adsorption in the water vapor adsorption isotherm.

Meanwhile, another method for improving water vapor adsorption capacity has been proposed, which involves supporting hygroscopic salts such as lithium chloride, magnesium chloride, and calcium chloride on porous water vapor adsorbents such as silica gel, mesoporous silica, and zeolite (see Patent Document 3).

A technology has also been proposed in which amorphous aluminum silicate is supported with a hygroscopic salt. Since amorphous aluminum silicate does not suffer from performance degradation even when a hygroscopic salt is supported, a moisture absorbing and releasing structure has been proposed in which the material is supported on a non-flammable sheet to form a honeycomb structure (see Patent Document 4). In addition, a powder has been proposed in which a composite of amorphous aluminum silicate and a low-crystalline layered clay mineral is supported with a hygroscopic salt to improve the adsorption performance (see Patent Document 5).

In the field of air conditioners, the addition of substances to improve comfort to the air supplied indoors has been considered, and examples of substances that can be added include phytoncide components found in trees, vitamin C, vitamin E, and hyaluronic acid (see Patent Document 6). In the air conditioner described in Patent Document 6, active ingredients including hyaluronic acid are blown into the room, and the moisturizing and beauty effects of hyaluronic acid create a comfortable feeling in the room.

Furthermore, a moisture absorbent has been proposed in which a stimuli-responsive polymer, whose affinity for water changes reversibly in response to an external stimuli, and a hydrophilic polymer form an interpenetrating polymer network structure or a semi-interpenetrating polymer network structure, and examples of the hydrophilic polymer include alginic acid, hyaluronic acid, and chitosan (see Patent Document 7). The moisture absorbent described in Patent Document 7 forms a network structure of a stimuli-responsive polymer and a hydrophilic polymer, and the structure is complex.

In addition, organic binders are used in the field of inorganic fiber products and granules to improve shape retention. For example, phenol resin, epoxy resin, polyvinyl alcohol resin, etc. are used in the field of inorganic fiber products (see Patent Document 8), and polyvinyl alcohol or polyvinylpyrrolidone is used in the field of granules (see Patent Document 9).

JP 2019-026487 A JP 2017-128499 A JP 2003-201113 A JP 2010-240554 A JP 2011-255331 A JP 2004-239594 A International Publication No. 2016/068129 JP 2021-161596 A JP 2017-002358 A

As described above, the aluminum silicates described in Patent Documents 1 and 2 can provide moisture absorbents capable of absorbing and releasing moisture over a wide range of humidity. In addition, Patent Documents 4 and 5 disclose that the adsorption performance of aluminum silicate can be improved by supporting a hygroscopic salt (hygroscopic salt).

In this situation, there was a need to further improve the adsorption performance of aluminum silicate.

The present invention was made in consideration of the above situation, and aims to provide a water vapor adsorbent that uses aluminum silicate and is capable of absorbing and releasing moisture over a wide range of humidity, and has particularly high adsorption performance in the medium to high humidity range.

As a result of extensive research aimed at achieving the above object, the inventors discovered that by adding hyaluronic acid and/or a hyaluronic acid derivative to aluminum silicate, a water vapor adsorbent can be obtained that is capable of absorbing and releasing moisture over a wide range of humidity, and that has improved adsorption performance in the medium to high humidity range in particular, and thus completed the present invention.

That is, the present invention includes the following aspects.
[1]
A water vapor adsorbent comprising an aluminum silicate and hyaluronic acid and/or a hyaluronic acid derivative.
[2]
The water vapor adsorbent according to aspect [1], wherein the aluminum silicate is at least one selected from the group consisting of tubular aluminum silicate, amorphous aluminum silicate, and an aluminum silicate complex composed of a low-crystalline layered clay mineral and an amorphous aluminum silicate.
[3]
The water vapor adsorbent according to aspect [1] or [2], further comprising a water-soluble binder resin.
[4]
The water vapor adsorbent according to aspect [3], wherein the water-soluble binder resin is polyvinyl alcohol.
[5]
A desiccant comprising, as a main component, the water vapor adsorbent according to any one of [1] to [4].
[6]
A dew condensation prevention agent comprising, as a main component, the water vapor adsorbent according to any one of [1] to [4].

The present invention makes it possible to realize a water vapor adsorbent that is capable of absorbing and releasing moisture over a wide range of humidity levels, and that has particularly high adsorption performance in the medium to high humidity range.

1 shows the results of measuring the water vapor adsorption isotherms of the water vapor adsorbents obtained in Examples 4 to 6 and Comparative Example 2. 1 is a photograph showing the appearance of the water vapor adsorbent obtained in Example 4 when applied to a plate.

The following describes embodiments of the present invention, but the present invention is not limited to the following embodiments. In addition, among the components in the following embodiments, components that are not described in the claims that indicate the highest concept are described as optional components.

<Water vapor adsorbent>
The water vapor adsorbent of the present invention contains an aluminum silicate and hyaluronic acid or a hyaluronic acid derivative.

<Aluminum Silicate>
The aluminum silicate used in the water vapor adsorbent of the present invention is a hydrated aluminum silicate whose constituent elements are silicon (Si), aluminum (Al), oxygen (O) and hydrogen (H) and which is assembled through a large number of Si-O-Al bonds.

Specifically, the aluminum silicate used in the present invention is at least one selected from the group consisting of tubular aluminum silicate, amorphous aluminum silicate, and an aluminum silicate complex consisting of a low-crystalline layered clay mineral and amorphous aluminum silicate.

(Method of producing aluminum silicate)
The aluminum silicate used in the water vapor adsorbent of the present invention can be artificially obtained by mixing and stirring an aqueous solution or aqueous dispersion of an inorganic silicon compound as the raw material for the silicon source and an inorganic aluminum compound as the raw material for the aluminum source, and then desalting (washing) and heating the resulting precursor.

The inorganic silicon compound used as the silicon source may be water-soluble or water-dispersible. For example, in addition to water-soluble silicates such as sodium orthosilicate and sodium metasilicate, colloidal silica such as amorphous colloidal silicon dioxide (e.g., Aerosil) is suitable. Colloidal silica can be dispersed in water and used as a silicon source as a dispersion. In addition, a sodium silicate aqueous solution called "water glass", which is a concentrated aqueous solution of sodium silicate, can also be used as a silicon source. This water glass is, for example, easily available on the market. In the following, aqueous solutions or aqueous dispersions that can be used as silicon sources may be collectively referred to as "aqueous solutions" or "solutions". Note that the silicon source is not limited to the above compounds, and any other compounds that have the same effect as them can be used in the same way.

The inorganic aluminum compound used as the aluminum source may be any compound that generates aluminum ions, and examples of such compounds include aluminum chloride, aluminum nitrate, aluminum sulfate, and sodium aluminate. The aluminum source is not limited to the above compounds, and any compound that has the same effect as the above compounds may be used.

An inorganic silicon compound as the silicon source and an inorganic aluminum compound as the aluminum source are dissolved in an appropriate aqueous solution to prepare a solution of a specified concentration. In order to synthesize an aluminum silicate that exhibits excellent adsorption behavior, it is necessary to mix them with a silicon/aluminum molar ratio (Si/Al molar ratio) in the range of 0.8 to 1.2.

The concentration of the inorganic silicon compound in the solution is preferably 1 to 2000 mmol/L in terms of Si, and the concentration of the inorganic aluminum compound solution is preferably 1 to 2000 mmol/L in terms of Al, but a more suitable concentration is to mix an inorganic silicon compound solution of 1 to 700 mmol/L in terms of Si with an aluminum compound solution of 1 to 1000 mmol/L in terms of Al.

A silicon compound solution and an aluminum compound solution are mixed so that the silicon/aluminum molar ratio (Si/Al molar ratio) and respective concentrations are within the above ranges, and an acid or alkali is added to adjust the pH to 5 to 9 to form a precursor. The resulting suspension containing the precursor material is then heated at about 95°C for a predetermined time, and then washed and dried to obtain an aluminum silicate powder. The particle size of the resulting powder is 0.1 to 100 μm, preferably 1 to 10 μm. If necessary, the powder may be pulverized or classified to adjust the particle size.

<Hyaluronic acid and/or hyaluronic acid derivative>
The water vapor adsorbent of the present invention contains hyaluronic acid and/or a hyaluronic acid derivative as an essential component.

The water vapor adsorbent of the present invention contains hyaluronic acid and/or a hyaluronic acid derivative together with aluminum silicate, thereby significantly improving the performance of aluminum silicate. Specifically, the moisture absorption and desorption performance over a wide range of humidity is further improved, resulting in a water vapor adsorbent that exhibits high-performance adsorption performance in the medium to high humidity range.

The hyaluronic acid and/or hyaluronic acid derivatives used in the water vapor adsorbent of the present invention are hydrophilic polymers with hygroscopic properties. Examples of hyaluronic acid derivatives include hyaluronic acid having hydrophilic groups such as sulfonic acid groups, phosphate groups, and amino groups on the side chains or main chains, hyaluronic acid with additional hydroxyl groups or carboxyl groups, and hyaluronic acid in which the carboxyl groups contained in the hyaluronic acid have been converted into hyaluronate salts by sodium ions, potassium ions, or the like. Among these, hyaluronic acid and/or hyaluronic acid derivatives used in the water vapor adsorbent of the present invention are preferably hyaluronate salts, and such hyaluronate salts are readily available on the market.

The hyaluronic acid used in the water vapor adsorbent of the present invention is not particularly limited, but may be, for example, a disaccharide polymer consisting of glucuronic acid and N-acetylglucosamine, with an average molecular weight of 50,000 to 10,000,000 daltons. Hyaluronic acid can be produced by known methods, or the hyaluronic acid itself can be purchased from the market.

In the present invention, free hyaluronic acid or its salt may be used. The salt of hyaluronic acid used in the present invention is not particularly limited, but examples include sodium salt, potassium salt, calcium salt, aluminum salt, zinc salt, iron salt, ammonium salt, and tetrabutylammonium salt. As described above, such hyaluronic acid salts are easily available on the market. Hyaluronic acid salts can also be prepared by converting commercially available hyaluronic acid into a salt using a well-known method.

As described above, the hyaluronic acid derivatives that can be used in the present invention may be those having hydrophilic groups introduced into the molecule, as well as substances having a hyaluronic acid skeleton derived from hyaluronic acid. Examples of such hyaluronic acid derivatives include, but are not limited to, substances in which one or more carboxyl groups in hyaluronic acid are esterified, substances in which hyaluronic acid is partially crosslinked with formaldehyde and further polymerized, and acetylated hyaluronic acid in which one or more hydroxyl groups in hyaluronic acid are acetylated.

In the present invention, at least one type of hyaluronic acid or at least one type of hyaluronic acid derivative may be used, or at least one type of hyaluronic acid and at least one type of hyaluronic acid derivative may be used in combination.

<Content of aluminum silicate and hyaluronic acid and/or hyaluronic acid derivative>
When the water vapor adsorbent of the present invention is composed of aluminum silicate and hyaluronic acid and/or hyaluronic acid derivative, the content of aluminum silicate in the entire water vapor adsorbent is 90 to 99.99 weight percent, and the content of hyaluronic acid and/or hyaluronic acid derivative is 0.01 to 10 weight percent. More preferably, the content of aluminum silicate is 99.9 to 99.99 weight percent, and the content of hyaluronic acid and/or hyaluronic acid derivative is 0.01 to 0.1 weight percent.

The water vapor adsorbent of the present invention significantly improves the performance of aluminum silicate by using aluminum silicate in combination with hyaluronic acid and/or a hyaluronic acid derivative, but as described above, the amount of hyaluronic acid and/or a hyaluronic acid derivative may be small relative to the amount of aluminum silicate. Surprisingly, in the present invention, even when the amount of hyaluronic acid and/or a hyaluronic acid derivative is extremely small, sufficient effect is exhibited and the performance of aluminum silicate can be dramatically improved.

<Water-soluble binder resin>
The water vapor adsorbent of the present invention may further contain a water-soluble binder resin as an optional component.

The water vapor adsorbent of the present invention contains a water-soluble binder resin in addition to aluminum silicate, hyaluronic acid and/or a hyaluronic acid derivative, and can be made into a water vapor adsorbent with shape retention without affecting the moisture absorption and release performance described above. Therefore, when the water-soluble binder resin is contained, it is possible to prepare a water vapor adsorbent that is applied to a wall surface, etc.

The water-soluble binder resin used in the water vapor adsorbent of the present invention is water-soluble and does not cause dripping or the like when a solution containing aluminum silicate and hyaluronic acid and/or a hyaluronic acid derivative is applied to a wall or the like.

Examples of water-soluble binder resins include polyvinyl alcohol (PVA), sugars, phenolic resins, polycarboxylic acid resins, etc. Among these, polyvinyl alcohol (PVA) is preferred because it is inexpensive, highly safe, and easily available. Polyvinyl alcohol (PVA) may contain vinyl acetate units in addition to vinyl alcohol units.

(Water-soluble binder resin content)
When the water vapor adsorbent of the present invention contains a water-soluble binder resin in addition to aluminum silicate and hyaluronic acid and/or a hyaluronic acid derivative, the weight percentages on a dry basis are 80 to 94.9% by weight of aluminum silicate, 0.01 to 10% by weight of hyaluronic acid and/or a hyaluronic acid derivative, and 5 to 30% by weight of water-soluble binder resin. More preferably, the weight percentages on a dry basis are 89.9 to 94.99% by weight of aluminum silicate, 0.01 to 0.1% by weight of hyaluronic acid and/or a hyaluronic acid derivative, and 5 to 10% by weight of water-soluble binder resin.

<Other ingredients>
The water vapor adsorbent of the present invention may contain any other component in addition to the above-mentioned essential components and the water-soluble binder resin, which is an optional component, as long as the effect of the present invention is not impaired.

<Method of manufacturing water vapor adsorbent>
The water vapor adsorbent of the present invention can be obtained by mixing hyaluronic acid and/or hyaluronic acid derivative with aluminum silicate, adding water and mixing, and then drying.When it contains an optional water-soluble binder resin, it can be obtained by mixing hyaluronic acid and/or hyaluronic acid derivative with aluminum silicate, adding polyvinyl alcohol aqueous solution and water and mixing, and then drying.

<Applications of water vapor adsorbents>
The use of the water vapor adsorbent of the present invention is not particularly limited, and it can be used in various applications requiring water vapor adsorption performance. For example, it can be a dehumidifier, a dew condensation prevention agent, an autonomous humidity control material, etc. The water vapor adsorbent of the present invention can adsorb and release moisture in a wide range of humidity, and has high adsorption performance in the medium to high humidity range in particular, and therefore can be suitably used as a dehumidifier or a dew condensation prevention agent.

The present invention will be specifically explained below with reference to examples, but the present invention is not limited to these in any way.

<Production of Aluminum Silicate Composite>
In the examples and comparative examples, an aluminum silicate complex powder was used. The aluminum silicate complex powder was produced using 1000 mL of a water glass aqueous solution having a Si concentration of 495 mmol/L as a silicon source (Si source) and 1000 mL of an aluminum sulfate aqueous solution having an Al concentration of 450 mmol/L as an aluminum source (Al source).

The water glass aqueous solution was added to the aluminum sulfate aqueous solution and stirred for about 15 minutes. The Si/Al molar ratio at this time was 1.1. After stirring, 5N sodium hydroxide aqueous solution was added until the pH reached about 7, and a suspension was obtained. The amount of sodium hydroxide aqueous solution added was 12 mL. The resulting suspension was stirred for 1 hour to prepare a precursor suspension. The prepared 1000 mL precursor suspension was washed three times by centrifugation, and 1000 mL of precursor suspension was prepared again. 70 mL of the obtained precursor suspension was placed in a Teflon (registered trademark) container and heated at 200°C for 6 hours. Next, it was dried at 60°C for 1 day and then crushed to obtain a powder with a particle size of 1 to 50 μm.

Powder X-ray diffraction measurements were performed on the obtained powder. The powder X-ray diffraction pattern showed broad peaks near 2θ = 20°, 26°, 35°, and 40°, confirming the formation of an aluminum silicate complex. The obtained aluminum silicate complex was used in Examples 1 to 6 and Comparative Examples 1 and 2.

<Example 1>

0.01 g of sodium hyaluronate and 20 g of water were added to 10 g of the aluminum silicate complex powder obtained above, mixed well, and then dried at room temperature to obtain a water vapor adsorbent.

Example 2
0.03 g of sodium hyaluronate and 20 g of water were added to 10 g of the aluminum silicate complex powder obtained above, mixed thoroughly, and then dried at room temperature to obtain a water vapor adsorbent.

Example 3
0.1 g of sodium hyaluronate and 20 g of water were added to 10 g of the aluminum silicate complex powder obtained above, mixed thoroughly, and then dried at room temperature to obtain a water vapor adsorbent.

<Comparative Example 1>
The aluminum silicate complex powder obtained above was used as it was in Comparative Example 1.

<Water vapor adsorption amount evaluation>
The water vapor adsorption amount was evaluated for the water vapor adsorbents obtained in Examples 1 to 3 and the aluminum silicate composite of Comparative Example 1. The results of the water vapor adsorption amount evaluation are shown in Table 1.

(Evaluation Method)
0.3 g of water vapor adsorbent or aluminum silicate complex was weighed into a weighing bottle. After drying at 100°C for 24 hours, it was cooled to room temperature and weighed, and the value obtained by subtracting the weight of the weighing bottle was taken as the dry weight. Next, it was placed in a thermohygrostat at 25°C and a relative humidity of 50%, and adsorption was performed for 24 hours. The value obtained by subtracting the weight of the weighing bottle was taken as the weight after adsorption. The adsorption rate was calculated from the dry weight and the weight after adsorption using the following formula.
Adsorption rate = (weight after adsorption - dry weight) ÷ dry weight × 100
Similarly to the above-mentioned case of 50% relative humidity, the water vapor adsorption amount was evaluated at a temperature of 25° C. and at relative humidities of 60%, 70%, 80% and 90%.

As shown in Table 1, the adsorption rates of the water vapor adsorbents of Examples 1 to 3 were greater than that of Comparative Example 1, and it was clear that the greater the amount of hyaluronic acid added, the greater the adsorption rate.

Example 4
0.4 g of sodium hyaluronate, 50 g of a 10% aqueous polyvinyl alcohol solution, and 167.5 g of water were added to 60 g of the aluminum silicate complex powder obtained above, mixed well, and then dried at room temperature to obtain a water vapor adsorbent.

Example 5
0.3 g of sodium hyaluronate, 50 g of a 10% aqueous polyvinyl alcohol solution, and 140.0 g of water were added to 60 g of the aluminum silicate complex powder obtained above, mixed well, and then dried at room temperature to obtain a water vapor adsorbent.

Example 6
0.04 g of sodium hyaluronate, 50 g of a 10% aqueous polyvinyl alcohol solution, and 140.0 g of water were added to 60 g of the aluminum silicate complex powder obtained above, mixed well, and then dried at room temperature to obtain a water vapor adsorbent.

<Comparative Example 2>
To 60 g of the aluminum silicate complex powder obtained above, 50 g of a 10% aqueous polyvinyl alcohol solution and 140.0 g of water were added and mixed well, and then dried at room temperature to obtain a water vapor adsorbent.

<Measurement of water vapor adsorption isotherm>
Water vapor adsorption isotherms were measured for the water vapor adsorbents obtained in Examples 4 to 6 and the water vapor adsorbent obtained in Comparative Example 2. The results are shown in FIG.

Figure 1 shows that the water vapor adsorption amounts of the water vapor adsorbents of Examples 4 to 6 are greater than that of the water vapor adsorbent of Comparative Example 2, indicating that the addition of hyaluronic acid increases the water vapor adsorption amount.

A photograph of the water vapor adsorbent obtained in Example 4 applied to a plate is shown in Figure 2. As shown in Figure 2, the water vapor adsorbent obtained by adding polyvinyl alcohol together with hyaluronic acid to an aluminum silicate complex does not drip even when applied to a plate or the like, and has shape retention.

Claims (6)

An autonomous moisture-regulating material comprising an aluminum silicate and hyaluronic acid and/or a hyaluronic acid derivative. The autonomous humidity control material according to claim 1, wherein the aluminum silicate is at least one selected from the group consisting of tubular aluminum silicate, amorphous aluminum silicate, and an aluminum silicate complex consisting of a low-crystalline layered clay mineral and an amorphous aluminum silicate. The autonomous humidity control material according to claim 1 , further comprising a water-soluble binder resin. The autonomous humidity control material according to claim 3 , wherein the water-soluble binder resin is polyvinyl alcohol. A dehumidifying agent comprising, as a main component, the autonomous humidity control material according to claim 1 . A dew condensation prevention agent comprising, as a main component, the autonomous humidity control material according to claim 1 .

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