JP7657625B2 - Film-like composition and method for producing same - Google Patents

Description

The present invention relates to a film-like composition that contains a moisture absorbent and is applied to a substrate, a method for producing the film-like composition, and a coating liquid used to produce the film-like composition.

This type of film-like composition exhibits moisture absorption properties by containing a moisture-absorbing material. When using such a film-like composition as a coating for a moisture-absorbing part, the higher the moisture absorption amount per unit weight of the coating, the more compact the size of the product containing the composition can be, which contributes to reducing the weight of the product. For example, when used as a coating for a desiccant element of a desiccant-type dehumidifier, the volume occupied by the desiccant element accounts for more than half of the product size, and if the moisture absorption amount of the film-like composition used as a coating for the desiccant element is increased, such a product can be made significantly more compact.

In recent years, metal organic frameworks (MOFs) have been attracting attention as materials with high adsorption capacity. In particular, a metal organic framework material with chromium as the central metal (hereinafter also referred to as MIL-101(Cr)) is known to have a moisture absorption capacity more than twice as high as that of materials conventionally used as moisture absorbents (silica gel, zeolite, calcium chloride, polymeric sorption materials, etc.) and to have high resistance to water deterioration.
The present inventors have proposed that when a coating liquid obtained by dispersing a metal-organic framework MIL-101(Cr) having chromium as a central metal as a moisture absorbent in a solvent such as water is applied to a substrate such as polyethylene terephthalate (PET) to produce a film-like composition, an acrylic polymer material is used as an adhesive curing agent (binder) and a urethane polymer material is added as a thickener to ensure the coatability of the coating liquid, thereby achieving good moisture absorption performance while obtaining a coating film having good film strength in which cracking, peeling, and the like are suppressed (see, for example, Patent Document 1).

JP 2019-171259 A

However, in a film-like composition containing the metal organic framework MIL-101(Cr) having chromium as the central metal as a moisture absorbent, the addition of a urethane-based polymer material as a thickener is a cause of a decrease in moisture absorption performance, so it is desirable to avoid the addition of such a urethane-based polymer material as much as possible. However, if a urethane-based polymer material is not added, a problem occurs in that the adhesion of the coating liquid to the substrate decreases, and the coatability deteriorates.
In view of this situation, a main object of the present invention is to provide a technique for obtaining a film-like composition having excellent coatability while maintaining good film strength and moisture absorption performance, when producing a film-like composition containing a metal organic framework MIL-101(Cr) having chromium as a central metal as a moisture absorbent.

A first characteristic configuration of the present invention is a film-like composition containing a moisture absorbent and applied onto a substrate,
The moisture absorbent contains a metal organic framework MIL-101(Cr) having chromium as a central metal,
The adhesive hardener contains maleic anhydride modified polyolefin.
In the present invention, the film-like composition refers to a film-like composition that contains a moisture-absorbing material and is in a state of being applied to a substrate, and the film-like composition itself has moisture absorption properties due to the moisture-absorbing property of the moisture-absorbing material.

In other words, as a result of intensive research, the inventors have found that when a coating liquid containing metal-organic framework MIL-101(Cr) with chromium as the central metal as a moisture absorbent is applied to a substrate to produce a film-like composition, if a maleic anhydride-modified polyolefin is used as an adhesive curing agent, a film-like composition with excellent coatability can be obtained without adding a urethane-based polymer material as a thickener, while maintaining good film strength with reduced cracking, peeling, etc., and good moisture absorption performance.

The second characteristic feature of the present invention is that the adhesive hardener contains an acrylic polymer material.

According to this configuration, by containing an acrylic polymer material in addition to the maleic anhydride-modified polyolefin as an adhesive hardener, it is possible to suppress the decrease in film strength and moisture absorption performance while limiting the amount of decrease in the maleic anhydride-modified polyolefin and improving moisture absorption performance.

The third characteristic feature of the present invention is that the substrate is any one selected from the group consisting of nonwoven fabric, paper, aluminum, copper, and stainless steel.

According to this configuration, by selecting the substrate to be coated as any one of nonwoven fabric, paper, aluminum, copper, and stainless steel, it is possible to obtain a film-like composition having good coating film strength without cracking, peeling, etc.
Furthermore, if the substrate is any one selected from the group consisting of nonwoven fabric, paper, and copper, the adhesion of the coating liquid to the substrate can be improved.

A fourth characteristic configuration of the present invention is a method for producing a film-like composition having the first to third characteristic configurations described above,
A metal organic framework MIL-101(Cr) having chromium as a central metal as the moisture absorbent and a maleic anhydride modified polyolefin as the adhesive curing agent are dispersed in a solvent obtained by mixing one or more selected from water, acetone, ethanol, and isopropyl alcohol to prepare a coating liquid;
The coating liquid is applied onto a substrate and then dried.

According to this configuration, water, acetone, ethanol, and isopropyl alcohol, which are easy to use, can be used as a solvent for dispersing the metal-organic framework MIL-101(Cr) and the maleic anhydride-modified polyolefin to prepare a coating liquid. Then, by applying the coating liquid thus prepared to a substrate and drying it, the film-like composition according to the present invention can be easily produced.

FIG. 1 is a diagram illustrating the film-like composition and the method for producing the same according to the present embodiment. Photograph showing the surface state of the film-like composition of Comparative Example 1 Photograph showing the surface state of the film-like composition of Example 1 Photograph showing the surface state of the film-like composition of Example 2 Photograph showing the surface state of the film-like composition of Example 3 Photograph showing the surface state of the film-like composition of Example 4 Photograph showing the surface state of the film-like composition of Example 5 Photograph showing the surface state of the film-like composition of Example 6 Photograph showing the surface state of the film-like composition of Example 7 Photograph showing the surface state of the film-like composition of Example 8 Photograph showing the surface state of the film-like composition of Example 9 Photograph showing the surface state of the film-like composition of Example 10 Photograph showing the surface state of the film-like composition of Example 11 Graph showing evaluation results of moisture absorption performance of film-like compositions of Examples 1 to 6 and Comparative Example 1

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings.
As shown in FIG. 1, the film-like composition E of this embodiment contains a moisture-absorbing material A and is a film-like composition applied onto a substrate X, and is used, for example, as a coating film for a desiccant element of a desiccant-type dehumidifier.
The film-like composition E contains, as the moisture absorbent A, a metal organic framework MIL-101(Cr) having chromium as a central metal, and contains, as the adhesive curing material B, a maleic anhydride-modified polyolefin.
In the method for producing such a film-like composition E, a metal-organic framework MIL-101(Cr) having chromium as a central metal as a moisture absorbent A and a maleic anhydride-modified polyolefin as an adhesive curing material B are dispersed in a solvent C obtained by mixing one or more selected from water, acetone, ethanol, and isopropyl alcohol to produce a coating liquid D. Then, the coating liquid D is applied onto a substrate X formed into a flat plate shape, for example, using a coater (coating machine) and dried at a predetermined temperature for a predetermined time, thereby producing a film-like composition E.
The film-like composition E produced in this manner has excellent coatability while maintaining good film strength with reduced cracking, peeling, and the like, and good moisture absorption performance, even without the addition of a urethane-based polymer material as a thickener.

When preparing coating solution D by dispersing moisture absorbent A and adhesive curing material B in solvent C, the viscosity needs to be adjusted depending on the type of coater (applicator) used, and the degree of dilution is appropriately set accordingly.
The ratio of the maleic anhydride modified polyolefin as the adhesive curing material B to the metal organic framework MIL-101(Cr) as the moisture absorbent A is not particularly limited as long as it is within the range of 1 wt % to 40 wt %, but is preferably within the range of 5 wt % to 35 wt %, and more preferably 10 wt % to 20 wt %.

The adhesive curing material B contains an acrylic polymer material in addition to the maleic anhydride modified polyolefin, thereby making it possible to suppress the deterioration of the film strength and moisture absorption performance while limiting the amount of deterioration of the maleic anhydride modified polyolefin and improving the moisture absorption performance.
The ratio of the acrylic polymer material as the adhesive curing material B to the metal-organic framework MIL-101 (Cr) as the moisture absorbent A is not particularly limited as long as it is within the range of 5% by weight to 40% by weight, but is preferably within the range of 15% by weight to 30% by weight, and more preferably 20% by weight to 30% by weight.

Any material can be used as the substrate X, but by using one selected from nonwoven fabric, paper, aluminum, copper, and stainless steel, a film-like composition E can be obtained that has good coating strength and is free from cracks, peeling, etc.

[Performance evaluation test]
The results of the performance evaluation test of the film-like composition will be described below.
First, the configurations of the film-like composition samples of Comparative Example 1 and Examples 1 to 11 used in this evaluation test will be described.
In this evaluation test, the metal organic framework MIL-101(Cr) was synthesized with reference to a non-patent document (G.Fery et al., SCIENCE, vol. 309, (2005) 2040-2042.). As the maleic anhydride polyolefin, "Hardlen (registered trademark) NZ1015" manufactured by Toyobo Co., Ltd. was used. As the acrylic polymer material, "Bonlon (registered trademark) PS-002" manufactured by Mitsui Chemicals, Inc. was used. In the film-like composition of this embodiment, the maleic anhydride polyolefin and the acrylic polymer material may be different from those exemplified above.

(Comparative Example 1)
The film-like composition of Comparative Example 1 was prepared by mixing the metal-organic framework MIL-101 (Cr) as the moisture absorbent with only an acrylic polymer material as the adhesive curing agent in a predetermined mixing ratio (see Table 1 below), dispersing the resulting precursor in isopropyl alcohol as a solvent to prepare a coating liquid, applying the coating liquid to a nonwoven fabric as a substrate, and drying at 90° C. or higher for 10 minutes or more.

(Examples 1 to 5)
The film-like compositions of Examples 1 to 5 were prepared by mixing the metal-organic framework MIL-101 (Cr) as a moisture absorbent with a maleic anhydride-modified polyolefin and an acrylic polymer material as adhesive curing agents in predetermined blending parts (see Table 1 below), dispersing the precursor in isopropyl alcohol as a solvent to prepare a coating liquid, applying the coating liquid to a nonwoven fabric as a substrate, and drying at 90° C. or higher for 10 minutes or more.

Example 6
The film-like composition of Example 6 was prepared by mixing the metal-organic framework MIL-101 (Cr) as the moisture absorbent with only maleic anhydride-modified polyolefin as the adhesive curing agent in a predetermined mixing ratio (see Table 1 below), dispersing the precursor in isopropyl alcohol as a solvent to prepare a coating liquid, applying the coating liquid to a nonwoven fabric as a substrate, and drying at 90° C. or higher for 10 minutes or more.

(Examples 7 to 11)
The film-like compositions of Examples 7 to 11 were prepared by mixing the metal-organic framework MIL-101 (Cr) as a moisture absorbent with the maleic anhydride-modified polyolefin and the acrylic polymer material as adhesive curing agents in the same predetermined mixing ratios (see Table 2 below) as in Example 4, dispersing the precursor in isopropyl alcohol as a solvent to prepare a coating liquid, applying the coating liquid to different substrates (see Table 2 below) and drying at 90° C. or higher for 10 minutes or longer.

Next, we will explain the methods used in this evaluation for appearance, adhesion, and moisture absorption performance.

(Appearance Evaluation)
Appearance evaluation was performed on the samples of the film-like composition of Comparative Example 1 and Examples 1 to 11. In this appearance evaluation, the surface of the film-like composition (see Figures 2 to 13) was visually observed to determine the presence or absence of cracks and peeling. The results are shown in Tables 1 and 2 below.
In the "Cracks" column in Tables 1 and 2 below, those with cracks are marked with "X" and those without cracks are marked with "O". In the "Peeling" column in Tables 1 and 2 below, those with peeling are marked with "X", those with slight peeling are marked with "△", and those without peeling are marked with "O".

(Adhesion Evaluation)
Adhesion evaluation was performed on the samples of the film-like composition of Comparative Example 1 and Examples 1 to 11. In this adhesion evaluation, cellophane tape was applied to the surface of the film-like composition, and the surface of the film-like composition after the applied cellophane tape was peeled off was visually observed to determine whether or not the film-like composition peeled off when the cellophane tape was peeled off. The results are shown in Tables 1 and 2 below.
In the "Adhesion" column of Tables 1 and 2 below, a film-like composition in which the entire film-like composition peeled off when the cellophane tape was peeled off is marked with "X", a film-like composition in which only a part of the film-like composition peeled off when the cellophane tape was peeled off is marked with "△", and a film-like composition in which almost no or only a small amount of the film-like composition peeled off when the cellophane tape was peeled off is marked with "○".

(Evaluation of Hygroscopicity)
A moisture absorption evaluation was carried out on the film-like composition samples of Comparative Example 1 and Examples 1 to 6 formed by applying the composition to a nonwoven fabric measuring 10 cm x 10 cm square. In this moisture absorption evaluation, the film-like composition samples formed by applying the composition to a substrate were kept in a thermo-hygrostat at a temperature of 30°C and a relative humidity of 60% for a predetermined time, and the ratio of the weight increase of each sample to the initial weight of the film-like composition after the predetermined time had elapsed was measured as moisture absorption performance (g/g). The results are shown in the graph of Figure 14, and the moisture absorption performance after 3 minutes and 30 minutes are shown in Table 1 below.

(Evaluation result 1)
With reference to Table 1 and the graph of FIG. 14, the film-like compositions of Comparative Example 1 and Examples 1 to 6 using nonwoven fabric as a substrate are evaluated.
It can be seen that the film-like compositions of Examples 1, 2, 3, and 4 have high moisture absorption performance from the start. This can be understood as being because adjusting the compounding ratio of the maleic anhydride modified polyolefin and the acrylic polymer material as the adhesive curing agent makes it easier for the metal organic framework MIL-101(Cr) as the moisture absorbent to be applied onto the nonwoven fabric substrate.

In Examples 1, 2, 4, and 5, the amount of maleic anhydride-modified polyolefin and acrylic polymer material used as adhesive hardeners was gradually increased relative to the metal organic framework MIL-101 (Cr) used as a moisture absorbent, and the moisture absorption properties of the film-like compositions were evaluated. However, the moisture absorption properties tend to decrease after Example 4, especially when the retention time is 30 minutes. This is thought to be due to the increase in the amount of maleic anhydride-modified polyolefin and acrylic polymer material, which may have reduced the blending ratio of metal organic framework MIL-101 (Cr) used as a moisture absorbent per unit weight, or the possibility that the blockage of water adsorption sites in the metal organic framework MIL-101 (Cr) used as a moisture absorbent may have increased, ultimately leading to a decrease in performance.

In Example 6, when the total compounding parts of the maleic anhydride modified polyolefin and the acrylic polymer material as the adhesive hardener with respect to the metal-organic framework MIL-101 (Cr) as the moisture absorbent was set to an intermediate value between Examples 2 and 4, the moisture absorption performance was not good. Considering this, it can be considered that the use of only the acrylic polymer material alone does not result in good moisture absorption performance.
The film-like compositions of Examples 1 to 6, which are obtained by adding maleic anhydride-modified polyolefin and an acrylic polymer material as an adhesive curing agent to the metal organic framework MIL-101(Cr) as an adsorbent, have inferior adsorption performance compared to the film-like composition of Comparative Example 1, which is obtained by adding only an acrylic polymer material to the metal organic framework MIL-101(Cr), but considering the results of the appearance evaluation and adhesion evaluation described above, it can be said that Comparative Example 1 is not practical. Also, compared to conventional film-like compositions such as those obtained by adding an acrylic polymer material and a urethane polymer material as a thickener to the metal organic framework MIL-101(Cr) or those using a polymer adsorbent (sodium polyacrylate, etc.), the moisture absorption performance after 3 minutes and the moisture absorption performance after 30 minutes are both excellent.

In addition, with regard to the appearance evaluation and adhesion evaluation, the film-like composition of Comparative Example 1, which does not contain maleic anhydride-modified polyolefin, was rated as "X" in terms of cracking, peeling, and adhesion, whereas the film-like compositions of Examples 1 to 6, which contain maleic anhydride-modified polyolefin, achieved high ratings. In particular, the film-like compositions of Examples 2 to 6, in which the blending ratio of maleic anhydride-modified polyolefin to metal-organic framework MIL-101(Cr) is 5/100 or more, were rated as "○" in terms of cracking, peeling, and adhesion. This can be said to be because the inclusion of maleic anhydride-modified polyolefin results in good film strength and good coatability with cracking, peeling, etc. suppressed.

(Evaluation result 2)
With reference to Table 2, the film-like composition of Example 4 using a nonwoven fabric as a substrate and the film-like compositions of Examples 7 to 11 containing maleic anhydride modified polyolefin and an acrylic polymer material in the same ratio as in Example 4, but using paper (cardboard), copper, stainless steel, aluminum, or a PET film as a substrate other than nonwoven fabric, are evaluated.
The film-like composition of Example 11, which used a PET film as a substrate, was observed peeling off from the edges as it dried, whereas the film-like compositions of Examples 4, 7, 8, 9, and 10, which used nonwoven fabric, paper, copper, stainless steel, and aluminum as substrates, did not crack or peel off and achieved good film strength.

A Moisture absorbent B Adhesive hardener C Solvent D Coating liquid E Film-like composition X Substrate

Claims (4)

A film-like composition comprising a moisture absorbent and applied onto a substrate,
The metal organic framework MIL-101(Cr) having chromium as a central metal is contained as the moisture absorbent ,
A film-like composition containing a maleic anhydride-modified polyolefin as an adhesive curing agent. The film-like composition according to claim 1, which contains an acrylic polymer material as the adhesive curing agent. The film-like composition according to claim 1 or 2, wherein the substrate is any one selected from nonwoven fabric, paper, aluminum, copper, and stainless steel. A method for producing the film-like composition according to any one of claims 1 to 3,
The moisture absorbent , which is a metal organic framework MIL-101(Cr) having chromium as a central metal, and the maleic anhydride modified polyolefin as the adhesive curing agent are dispersed in a solvent containing one or more selected from water, acetone, ethanol, and isopropyl alcohol to prepare a coating liquid;
A method for producing a film-like composition, comprising applying the coating liquid onto a substrate and drying the applied coating liquid.

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