JP2024130814A - Laminate - Google Patents

Abstract

To provide a functional material which has a good film-forming property and can change a wettability of a surface of a material by using an external stimulus as a trigger.SOLUTION: A laminate of the present invention comprises a base layer and a functional layer containing a silane-modified nano-cellulose having a tertiary amine structure, wherein a water contact angle of a surface of the functional layer is 70 degrees or more when measured with water of pH 7, and the water contact angle of the surface of the functional layer is 30 degrees or less when measured with water of pH 2.SELECTED DRAWING: None

Description

The present invention relates to a laminate.

In recent years, from the perspective of circular economy and a sustainable society, high-performance materials made from plant-derived materials have been attracting attention. Cellulose nanomaterials, which are made by defibrating plant fibers and nano-sizing them, are being considered for use in functional materials.
There are many hydroxyl groups on the surface of cellulose nanomaterials. It has been proposed to impart not only hydrophilicity but also various surface functionalities by utilizing these hydroxyl groups themselves or by imparting functionality through chemical modification (for example, Patent Documents 1 to 3 and Non-Patent Document 1).

Patent Document 1 discloses a hydrophilic coating composition containing an alkoxysilane, a lower alcohol having 1 to 4 carbon atoms, and cellulose nanofibers.
Patent Document 2 discloses a sheet having a fiber layer and a coating layer on the fiber layer, the surface of which is provided with water repellency.
Patent Document 3 discloses a hydrophilic coating agent containing a tin oxide sol and a hydrophilic sol. Titanium oxide and cellulose nanofibers are disclosed as components of the hydrophilizing agent of the hydrophilic sol.
In Non-Patent Document 1, chemical modification of cellulose nanofibers with tertiary amino group-containing acrylic monomers is proposed. Application of wettability control technology triggered by _CO2 to oil-water separation membranes is being investigated.

JP 2018-119073 A JP 2021-46658 A JP 2020-105274 A

ACS Appl. Mater. Interfaces 2019, 11, 9367-9373.

In the functional materials disclosed in Patent Documents 1 to 3, it is not possible to change the wettability of the surface of the material by using an external stimulus as a trigger.
Non-Patent Document 1 suggests that wettability switching triggered by CO ₂ can be expected by chemically modifying cellulose nanofibers with a tertiary amino group-containing acrylic monomer. However, according to the inventor's investigation, the modification scheme with a tertiary amine is complicated, and there is a problem with the film formability when a coating film is actually formed on a substrate.

The present invention provides a functional material that has good film-forming properties and can change the wettability of its surface by using an external stimulus as a trigger.

The present invention has the following aspects.
[1] A laminate having a base layer and a functional layer containing silane-modified nanocellulose having a tertiary amine structure, wherein the water contact angle of the surface of the functional layer is 70 degrees or more when measured in water of pH 7, and the water contact angle of the surface of the functional layer is 30 degrees or less when measured in water of pH 2.
[2] The laminate described in [1], wherein the silane-modified nanocellulose is a reaction product of nanocellulose and two or more types of alkoxysilanes.
[3] The laminate according to [2], wherein the two or more kinds of alkoxysilanes include a silane compound (A) having a tertiary amine structure and a silane compound (B) having an alkyl group and not having a tertiary amine structure.
[4] The laminate according to [3], wherein the silane compound (A) is at least one selected from the group consisting of (N,N-dimethylaminopropyl)trimethoxysilane and (N,N-diethylaminopropyl)trimethoxysilane.
[5] The laminate according to [3] or [4], wherein the silane compound (B) has an alkyl group having 6 to 12 carbon atoms.
[6] The laminate according to any one of [3] to [5], wherein a molar ratio M _A /M _B of the silane compound (A) to the silane compound (B) is 1.5 or more.
[7] The laminate according to any one of [1] to [6], wherein the nanocellulose is a cellulose nanocrystal.
[8] The laminate according to any one of [1] to [7], wherein the functional layer has a thickness of 10 to 1,000 nm.
[9] The laminate according to any one of [1] to [8], wherein the substrate layer is a resin film, a fibrous substrate, or a glass substrate.

The present invention provides a functional material that has good film-forming properties and can change the wettability of its surface by using an external stimulus as a trigger.

The meaning of the terms is as follows:
"Nanocellulose" is cellulose that has been mechanically or chemically broken down to the nano level. The presence of "nanocellulose" can be determined by observation with an electron microscope, IR spectroscopy, etc.
"Silane-modified nanocellulose" refers to a reaction product between nanocellulose and silane, for example, a dehydration condensation reaction product. The presence of "silane-modified nanocellulose" can be determined by XPS elemental analysis or the like.
The use of "to" indicating a range of numerical values means that the numerical values before and after it are included as the lower limit and upper limit.
The numerical ranges disclosed in this specification can be combined in any manner to form new numerical ranges.

<Laminate>
The laminate of the present invention has a substrate layer and a functional layer. The functional layer contains silane-modified nanocellulose having a tertiary amine structure. In the laminate of the present invention, the water contact angle of the surface of the functional layer is 70 degrees or more when measured with water of pH 7. And, the water contact angle of the surface of the functional layer is 30 degrees or less when measured with water of pH 2. Therefore, according to the laminate of the present invention, the wettability of the surface can be changed by using an external stimulus as a trigger. In addition, the film-forming property of the functional layer of the laminate is good.

The following describes in detail some embodiments of the present invention. However, the present invention is not limited to the embodiments disclosed in this specification, and can be modified as appropriate without departing from the gist of the invention. The embodiments disclosed in this specification can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the gist of the invention.

<Base layer>
The material of the substrate layer is not particularly limited. In one example, the substrate layer may be a resin film, a fibrous substrate, or a glass substrate.

Non-limiting examples of the resin film include films made of thermoplastic resins, such as polyolefin resins (polyethylene, polypropylene, etc.), polyester resins (polyethylene terephthalate, polyethylene isophthalate, polyethylene naphthalate, polybutylene terephthalate, etc.), polylactic acid, polyurethane, polyvinyl acetate, polyacrylonitrile, polyvinyl chloride, and polycarbonate resins.
The resin film may be a porous film that has been subjected to a porosity treatment such as chemical foaming, physical foaming, stretching porosity, etc. The resin film may be a stretched film that has been subjected to a uniaxial stretching treatment or a biaxial stretching treatment.

Non-limiting examples of fibrous substrates include nonwoven fabrics, woven fabrics, and knitted fabrics. Non-limiting examples of fibers include chemical fibers such as polyester fibers, nylon fibers, acrylic fibers, polyurethane fibers, acetate fibers, rayon fibers, and polylactic acid fibers; cotton, hemp, silk, wool, and blends thereof.

The substrate layer may have a single layer structure or a multilayer structure. When the substrate layer has a multilayer structure, the layer structure may be a two-layer structure, a three-layer structure, or a four-layer structure or more, as long as it does not deviate from the gist of the present invention, and the number of layers is not particularly limited. When the substrate layer has a multilayer structure consisting of multiple layers, the multiple layers may be composed of the same resin or different resins.

The substrate layer may contain additives as necessary. For example, an ultraviolet absorber may be added to the substrate layer in order to impart weather resistance. In addition, particles may be added to impart slipperiness and prevent scratches during each process. If necessary, at least one additive selected from the group consisting of conventionally known antioxidants, antistatic agents, heat stabilizers, lubricants, dyes, and pigments may be added to the substrate layer.
The surface of the substrate layer on which the functional layer is formed may be subjected to a surface treatment such as a corona treatment, a plasma treatment, or a coating treatment for adjusting wettability, as required.

The thickness of the substrate layer is not particularly limited, but can be, for example, 10 to 1,000 nm, 20 to 900 nm, 50 to 500 nm, etc.

<Functional layer>
The functional layer contains silane-modified nanocellulose having a tertiary amine structure as a main material. Here, "main material" means the material having the highest mass ratio among the materials constituting the functional layer. For example, the ratio of the main material to the materials constituting the functional layer is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, even more preferably 80% by mass or more, even more preferably 90% by mass or more, and may be 100% by mass.

The silane-modified nanocellulose can be confirmed to have a tertiary amine structure by analysis with FT-IR (Thermo Fisher Scientific's "Ge-ATR"). By comparing with nanocellulose before modification with a tertiary amine structure, it can be confirmed by a peak derived from the tertiary amine structure in the region around 2,780 cm ^-1 in the infrared absorption spectrum.

The functional layer may further contain at least one type of nanocellulose selected from the group consisting of silane-modified nanocellulose and unmodified nanocellulose that do not have a tertiary amine structure. In this case, the mass proportion of the silane-modified nanocellulose having a tertiary amine structure in the material constituting the functional layer is preferably higher than the mass proportion of the at least one type of nanocellulose selected from the group consisting of silane-modified nanocellulose and unmodified nanocellulose that do not have a tertiary amine structure in the material constituting the functional layer.

As the silane-modified nanocellulose in the functional layer, a reaction product of nanocellulose and two or more types of alkoxysilanes is preferred. A functional layer that is suitable in terms of film-forming properties can be formed from a functional layer-forming composition that contains nanocellulose and two or more types of alkoxysilanes.

(Nanocellulose)
Non-limiting examples of nanocellulose include, for example, long fibrous cellulose nanofibers (CNF) and highly crystalline cellulose nanocrystals (CNC).
As the nanocellulose, cellulose nanocrystal is preferred from the viewpoint that its addition does not increase the viscosity of the composition for forming the functional layer and improves the handleability when applied to the base layer.

The average fiber diameter of the nanocellulose is not particularly limited, but from the viewpoint of improving the transparency of the functional layer, it is preferably 0.1 to 100 nm, more preferably 0.5 to 50 nm, and even more preferably 1 to 20 nm.
In addition, the average fiber length of the nanocellulose is not particularly limited, but from the viewpoint of improving the transparency of the functional layer, it is preferably 1 to 1000 nm, more preferably 5 to 500 nm, and even more preferably 10 to 200 nm.
The average aspect ratio (fiber length/fiber diameter) of nanocellulose is not particularly limited, but is preferably 1 to 500, more preferably 10 to 200, and even more preferably 20 to 100. When the average aspect ratio is within the above numerical range, the composition for forming a functional layer is less likely to thicken and has good handleability.
The average fiber diameter, average fiber length, and average aspect ratio of nanocellulose are determined by observing the fibers dispersed in an aqueous dispersion of nanocellulose or in a coating liquid for forming a functional layer using a scanning electron microscope or the like, and measuring 10, preferably 100, selected fibers. The average values can be determined.

(Alkoxysilane)
In a preferred embodiment of the composition for forming a functional layer, the two or more types of alkoxysilanes include a silane compound (A) having a tertiary amine structure and a silane compound (B) having an alkyl group and not having a tertiary amine structure.

Silane compound (A) has a tertiary amine structure. Silane compound (A) is not particularly limited as long as it is a compound having a tertiary amine structure and an alkoxysilane group. Silane compound (A) may be any one of monoalkoxysilane, dialkoxysilane, and trialkoxysilane, but is preferably at least one selected from the group consisting of dialkoxysilane and trialkoxysilane, and more preferably trialkoxysilane from the viewpoint of film forming property.
Non-limiting examples of the alkoxysilane group of the silane compound (A) include, for example, a methoxy group, an ethoxy group, a propyl group, and an isopropyl group.

The tertiary amine structure of the silane compound (A) can be represented by N( ^{R1A R2A R3A} ), where ^R1A , ^R2A and ^R3A are each independently the same or different alkyl groups or aryl groups.
Non-limiting examples of R ^1A _, R ^2A , and R ^3A include, for example, a linear or branched alkyl group having 1 to 4 carbon atoms, and a phenyl group. Non-limiting examples of the alkyl group include, for example, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, an i-butyl group, and a t-butyl group. Of these, a methyl group and an ethyl group are preferred, and a methyl group is more preferred.

Non-limiting examples of the silane compound (A) include, for example, (N,N-dimethylaminopropyl)trimethoxysilane, (N,N-diethylaminopropyl)trimethoxysilane, dimethyloctadecyl[3-(trimethoxysilyl)propyl]ammonium chloride, triethoxy-3-(2-imidazolin-1-yl)propylsilane, and N,N-dimethyl-3-(triethoxysilyl)propan-1-amine.

The silane compound (A) may be used alone or in combination of two or more types.

The silane compound (B) is not particularly limited as long as it does not have a tertiary amine structure and has an alkoxysilane group. The silane compound (B) may be any of monoalkoxysilane, dialkoxysilane, trialkoxysilane, and tetraalkoxysilane, but is preferably at least one selected from the group consisting of dialkoxysilane and trialkoxysilane.

Non-limiting examples of the alkoxysilane group of silane compound (B) include, for example, a methoxy group, an ethoxy group, a propyl group, and an isopropyl group. However, it is preferable that the number of carbon atoms of the alkoxysilane group of silane compound (B) is the same as the number of carbon atoms of the alkoxysilane group of silane compound (A). If these carbon numbers are the same, there is less difference in the rate of hydrolysis between silane compound (A) and silane compound (B). This leads to even better film-forming properties.

As the dialkoxysilane in the silane compound (B), a compound represented by the following general formula (1) is preferred.

In formula (1), ^R1 and ^R3 are each independently an alkyl group having 1 to 12 carbon atoms, and ^R1 and ^R3 may be the same or different. ^R2 and ^R4 are each independently an alkyl group having 1 to 3 carbon atoms, and ^R2 and ^R4 may be the same or different.

Non-limiting examples of dialkoxysilanes in the silane compound (B) include dimethyldimethoxysilane, dimethyldiethoxysilane, dimethyldiethoxysilane, diethyldiethoxysilane, diisobutyldimethoxysilane, and dimethoxymethyl-n-octylsilane.

The dialkoxysilane in the silane compound (B) is preferably at least one selected from the group consisting of dimethyldimethoxysilane, dimethyldiethoxysilane, dimethyldiethoxysilane, diethyldiethoxysilane, diisobutyldimethoxysilane and dimethoxymethyl-n-octylsilane.
The dialkoxysilane in the silane compound (B) may be used alone or in combination of two or more kinds.

As the trialkoxysilane in the silane compound (B), a compound represented by the following general formula (2) is preferred.

In formula (2), R ⁵ is an alkyl group having 1 to 12 carbon atoms. R ⁶ to R ⁸ are each independently an alkyl group having 1 to 3 carbon atoms, and R ⁶ to R ⁸ may be the same or different.

Non-limiting examples of trialkoxysilanes in the silane compound (B) include methyltrimethoxysilane, methyltriethoxysilane, methyltrippropoxysilane, methyltriisopropoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, ethyltrippropoxysilane, ethyltriisopropoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, n-propyltrippropoxysilane, n-propyltriisopropoxysilane, isopropyl Examples of the silane include n-butyltrimethoxysilane, isopropyltrimethoxysilane, isopropyltripropoxysilane, n-butyltriethoxysilane, isobutyltrimethoxysilane, isobutyltriethoxysilane, n-hexyltrimethoxysilane, n-hexyltriethoxysilane, n-octyltrimethoxysilane, n-octyltriethoxysilane, allyltrimethoxysilane, dodecyltrimethoxysilane, dodecyltriethoxysilane, hexadecyltrimethoxysilane, hexadecyltriethoxysilane, and allyltriethoxysilane.

Examples of the trialkoxysilane in the silane compound (B) include methyltrimethoxysilane, methyltriethoxysilane, methyltrippropoxysilane, methyltriisopropoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, ethyltrippropoxysilane, ethyltriisopropoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, n-propyltrippropoxysilane, n-propyltriisopropoxysilane, isopropyltrimethoxysilane, isopropyltriisopropoxysilane, and isopropyltrimethoxysilane. At least one selected from the group consisting of trimethoxysilane, isopropyltripropoxysilane, n-butyltriethoxysilane, isobutyltrimethoxysilane, isobutyltriethoxysilane, n-hexyltrimethoxysilane, n-hexyltriethoxysilane, n-octyltriethoxysilane, allyltrimethoxysilane, dodecyltrimethoxysilane, dodecyltriethoxysilane, hexadecyltrimethoxysilane, hexadecyltriethoxysilane, and allyltriethoxysilane is preferred.
The trialkoxysilane in the silane compound (B) may be used alone or in combination of two or more kinds.

Non-limiting examples of the tetraalkoxysilane in the silane compound (B) include tetramethoxysilane, tetraethoxysilane, and tetrapropoxysilane.
The tetraalkoxysilane in the silane compound (B) is preferably at least one selected from the group consisting of tetramethoxysilane, tetraethoxysilane and tetrapropoxysilane.
The tetraalkoxysilane in the silane compound (B) may be used alone or in combination of two or more kinds.

The composition for forming a functional layer preferably contains a tetraalkoxysilane as the silane compound (B), and more preferably contains at least one selected from the group consisting of tetraethoxysilane and tetramethoxysilane.
By including tetraalkoxysilane as the silane compound (B), the proportion of hydrophilic groups in the functional layer increases, so that the hydrophilicity of the functional layer can be improved.

The silane compound (B) includes a silane compound (B1) having an alkyl group with 6 to 12 carbon atoms and a silane compound (B2) having an alkyl group with 1 to 5 carbon atoms. Of these, the silane compound (B1) is preferred from the viewpoint of ease of imparting hydrophobicity. The silane compound (B2) can be used appropriately and as necessary to adjust the balance between hydrophilicity and hydrophobicity of the surface of the functional layer.

When the carbon number of the alkyl group of the silane compound (B1) is equal to or greater than the lower limit of the above-mentioned range, it is easy to impart hydrophobicity to the surface of the functional layer. When the carbon number is equal to or less than the upper limit of the above-mentioned range, the tertiary amine structure based on the silane compound (A) is not easily affected by the steric hindrance of the silane compound (B) and the coating. Therefore, it is easy to obtain a laminate that can change the wettability of the surface of the functional layer.
When the number of carbon atoms in the alkyl group of the silane compound (B2) is within the above range, hydrophilicity can be easily imparted to the surface of the functional layer.

As the silane compound (B1), at least one selected from the group consisting of dimethoxymethyl-n-octylsilane, n-hexyltrimethoxysilane, n-hexyltriethoxysilane, n-octyltrimethoxysilane, n-octyltriethoxysilane, allyltrimethoxysilane, dodecyltrimethoxysilane, dodecyltriethoxysilane, hexadecyltrimethoxysilane, hexadecyltriethoxysilane, and allyltriethoxysilane is preferred.

As the silane compound (B2), at least one selected from the group consisting of dimethyldimethoxysilane, dimethyldiethoxysilane, dimethyldiethoxysilane, diethyldiethoxysilane, diisobutyldimethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, methyltrippropoxysilane, methyltriisopropoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, ethyltrippropoxysilane, ethyltriisopropoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, n-propyltrippropoxysilane, n-propyltriisopropoxysilane, isopropyltrimethoxysilane, isopropyltrimethoxysilane, isopropyltrippropoxysilane, n-butyltriethoxysilane, isobutyltrimethoxysilane, and isobutyltriethoxysilane is preferred.

The silane compound (B) may be used alone or in combination of two or more.

(solvent)
The composition for forming a functional layer may further contain a solvent.
As a solvent, from the viewpoint of the reactivity between nanocellulose and alkoxysilane and the applicability of the composition for forming a functional layer to the substrate layer, water, alcohol, or a mixture thereof (hereinafter, these are collectively referred to as "water / alcohol system"). Is preferable.

When a water/alcohol system is used as the solvent, the proportion of water is preferably 15 to 75 mass %, more preferably 30 to 50 mass %, based on 100 mass % of the solvent.
When the proportion of water is equal to or greater than the lower limit of the above-mentioned range, the dispersibility of nanocellulose in the composition for forming a functional layer is improved and the composition is less likely to aggregate. When the proportion of water is equal to or less than the upper limit of the above-mentioned range, the condensation reaction of alkoxysilane in the composition for forming a functional layer is more easily controlled.

The composition for forming a functional layer may further include a basic substance for adjusting the pH. A non-limiting example of the basic substance is ammonia.
The pH of the composition for forming a functional layer is preferably from 7 to 12 from the viewpoint of ease of handling.

(Composition of Functional Layer-Forming Composition)
The content of nanocellulose in the composition for forming a functional layer is preferably 10 to 90% by mass, more preferably 20 to 80% by mass, of the total amount of the composition for forming a functional layer. When the content of nanocellulose in the composition for forming a functional layer is within the above numerical range, it is easy to control the amount of the composition for forming a functional layer to be applied, and the viscosity is less likely to become high. Therefore, the handling property during application to the base layer is improved.

The content of alkoxysilane in the composition for forming a functional layer (the total amount of silane compound (A) and silane compound (B) if they are contained) is preferably 10 to 90 mass % of the total amount of the composition for forming a functional layer, and more preferably 20 to 80 mass %. When the content of alkoxysilane is within the above numerical range, the pot life and coating method selectivity of the composition for forming a functional layer are improved.

When the composition for forming a functional layer contains a silane compound (A) and a silane compound (B), it is preferable that the total content of the tertiary amine structure-containing silane compound (A) is greater than the total content of the silane compound (B). This is because it is easy to obtain a laminate whose surface wettability can be changed by using an external stimulus as a trigger.

In the composition for forming a functional layer, the molar ratio M _A /M _B of the silane compound (A) and the silane compound (B) is not particularly limited, but the lower limit is preferably 1.5 or more, more preferably 2.0 or more, and even more preferably 2.5 or more. The upper limit of the molar ratio M _A /M _B is preferably 20 or less, more preferably 10 or less, and even more preferably 5.0 or less. M _A is the number of moles of the silane compound (A) contained in the two or more alkoxysilanes, and M _B is the number of moles of the silane compound (B) contained in the two or more alkoxysilanes.

When the molar ratio M _A /M _B is equal to or greater than the lower limit, a tertiary amine structure can be sufficiently introduced into the nanocellulose, making it easier to obtain a laminate whose surface wettability can be changed by triggering an external stimulus.
When the molar ratio M _A /M _B is equal to or less than the upper limit, the condensation and phase separation of two or more types of alkoxysilane and nanocellulose can be sufficiently promoted. Therefore, the film formability of the functional layer is improved.

The mass ratio of nanocellulose to alkoxysilane in the composition for forming the functional layer (alkoxysilane/nanocellulose) is not particularly limited, but is preferably 0.1 to 5.0, and more preferably 0.2 to 2.5. When the mass ratio is within the above numerical range, the tertiary amine structure can be sufficiently introduced into the nanocellulose. Therefore, it is easy to obtain a laminate whose surface wettability can be changed by using an external stimulus as a trigger. In addition, gelation due to a condensation reaction between alkoxysilanes is less likely to occur, and the dehydration condensation reaction between nanocellulose and alkoxysilane proceeds more smoothly, resulting in better film formability.

The water contact angle of the surface of the functional layer is 70 degrees or more when measured in water of pH 7, and 30 degrees or less when measured in water of pH 2. From the viewpoint of imparting hydrophobicity, the water contact angle measured in water of pH 7 is preferably 75 degrees or more, more preferably 90 degrees or more, and even more preferably 120 degrees or more. From the viewpoint of imparting hydrophilicity, the water contact angle measured in water of pH 2 is preferably 25 degrees or less, more preferably 20 degrees or less, and even more preferably 10 degrees or less.
The water contact angle of the surface of the functional layer is determined by the method described in the Examples.

The water contact angle after the surface of the functional layer is treated with carbon dioxide is preferably 50 degrees or less, more preferably 40 degrees or less, even more preferably 30 degrees or less, and even more preferably 25 degrees or less.
The water contact angle after the surface of the functional layer is treated with carbon dioxide is determined by the method described in the Examples.

The thickness of the functional layer is not particularly limited, but from the viewpoint of improving the strength of the coating film and preventing cracks, it is preferably 10 to 1,000 nm, more preferably 50 to 500 nm, and even more preferably 100 to 300 nm.

<Other layers>
The laminate may further include layers other than the substrate layer and the functional layer. The other layers may be located, for example, between the functional layer and the substrate layer, on the opposite side of the substrate layer to the functional layer, etc.
Non-limiting examples of the other layers include a primer layer, a stress relief layer, and a layer that improves adhesion between the substrate and the functional layer.

<Method of manufacturing laminate>
A typical example of the method for producing the laminate will be described below.
A typical method for manufacturing a laminate includes a coating liquid preparation step of preparing a coating liquid consisting of a functional layer-forming composition containing nanocellulose and alkoxysilane, a coating film formation step of applying the coating liquid to a substrate layer to form a coating film, and a heat treatment step of heat-treating the coating film to obtain a functional layer containing silane-modified nanocellulose.
In the production of the laminate, it is possible to optionally add other treatments or steps in addition to the above.

A "process" may or may not be performed in a single manufacturing line. Furthermore, processing in one process may be performed intermittently, with time gaps, different equipment, or different locations. A process may also be performed in a single manufacturing line with other processes. In other words, multiple processes may be performed in the same equipment.

In the coating solution preparation step, nanocellulose and alkoxysilane are mixed in a solvent to prepare a coating solution consisting of a functional layer forming composition.
The details and preferred embodiments of the composition for forming a functional layer are as described above.

From the viewpoint of increasing the dispersibility of nanocellulose in the coating solution, it is preferable to disperse nanocellulose in a solvent and then add alkoxysilane. If pH adjustment is required, it is preferable to add a basic substance in this step.

After mixing nanocellulose and alkoxysilane, heating may be performed to increase reactivity. Although a reaction occurs when nanocellulose and alkoxysilane are simply mixed, heating can promote the reaction between nanocellulose and alkoxysilane.

The heating temperature and heating time during the reaction of nanocellulose with alkoxysilane are not particularly limited as long as the reaction between nanocellulose and alkoxysilane proceeds. The heating temperature is preferably 30 to 80°C, more preferably 40 to 70°C. The heating time is preferably 30 seconds to 2 hours, more preferably 30 minutes to 1.5 hours, and even more preferably 30 minutes to 1 hour.
After the reaction of nanocellulose with alkoxysilane, the mixture may be left to cure at room temperature for 1 to 7 days to further react with any unreacted silanes.

When using two or more types of silane compounds (B), it is preferable to react two or more types of silane compounds (B) with nanocellulose first, and then mix in the silane compound (A) having a tertiary amine structure. By reacting the silane compound (A) having a tertiary amine structure with nanocellulose after reacting the two or more types of silane compounds (B), the tertiary amine structure based on the silane compound (A) is less susceptible to the influence of the coating caused by the steric hindrance of the two or more types of silane compounds (B). Therefore, it is easy to obtain a laminate that can change the wettability of the surface of the functional layer.

In the coating film forming step, a coating liquid is applied to a substrate layer to form a coating film.
The method for applying the coating liquid to the substrate layer may be a known method, such as a comma coating method, a gravure coating method, a reverse coating method, a knife coating method, a dip coating method, a spray coating method, an air knife coating method, a spin coating method, a roll coating method, a printing method, a dip method, a slide coating method, a curtain coating method, a die coating method, a casting method, a bar coating method, or an extrusion coating method.

The thickness of the coating film is not particularly limited, but is preferably 10 to 1,000 nm, more preferably 50 to 500 nm, and even more preferably 100 to 300 nm. If the thickness of the coating film is equal to or greater than the lower limit of the above numerical range, control during application becomes easier. If the thickness of the coating film is equal to or less than the upper limit of the above numerical range, cracks due to shrinkage during drying and alkoxysilane condensation are less likely to occur.

In the heat treatment process, the coating is dried by heat treatment to form a functional layer containing silane-modified nanocellulose.

The drying method is not particularly limited, and may be heat drying or natural drying.
The drying temperature and drying time are not particularly limited as long as the solvent is removed from the coating film and the dehydration condensation of the alkoxysilane proceeds satisfactorily. The drying temperature is preferably 60 to 150° C., and more preferably 80 to 120° C. The drying time is preferably 30 seconds to 5 hours, more preferably 30 minutes to 3 hours, and even more preferably 30 minutes to 2 hours.

<Action and effect>
In the laminate described above, the water contact angle of the surface of the functional layer is 70 degrees or more when measured in water of pH 7, and is 30 degrees or less when measured in water of pH 2, so that the wettability of the surface can be changed by triggering an external stimulus.

Since the functional layer contains silane-modified nanocellulose with a tertiary amine structure, it is possible to switch the wettability triggered by external stimuli such as carbon dioxide and pH. Since carbon dioxide can be used as a resource for switching, it can be applied to various carbon dioxide-related processes.
According to the laminate of the present invention, cellulose, which is a renewable natural resource, can be effectively utilized. In addition, a functional layer can be formed by silylation modification of nanocellulose and a general-purpose coating process.

<Applications>
Since the laminate has a tertiary amine structure in the functional layer, the wettability of the surface can be changed by using an external stimulus as a trigger.
The water contact angle of the surface of the functional layer is 70 degrees or more when measured with water of pH 7. Therefore, the wettability of the surface of the functional layer can be made more hydrophobic as the surface of the functional layer is relatively brought closer to basic conditions by an external stimulus. In this case, low protein adsorption, oil-water separation, etc. can be imparted to the laminate.

On the other hand, the water contact angle of the surface of the functional layer is 30 degrees or less when measured with water of pH 2. Therefore, the wettability of the surface of the functional layer can be made more hydrophilic as the surface of the functional layer is brought closer to relatively acidic conditions by an external stimulus. In this case, ion adsorption properties, etc. can be imparted to the laminate. Such a laminate is suitable for glass surfaces and resin sheets that require self-cleaning.

The laminate can also change its wettability when triggered by carbon dioxide. This makes it suitable for use in oil-water separation membranes, sensing, patterning, and in combination with separation and purification processes that use supercritical carbon dioxide.

Non-limiting examples of applications of the laminate include glass for various panels, full panels for solar panels, and lighting construction materials.

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following description.

<Abbreviation>
(Nanocellulose)
・CNC: Cellulose nanocrystal (Cellufocé product "NCV-100")

(Silane Compound (A))
DMAP: (N,N-dimethylaminopropyl)trimethoxysilane

(Silane Compound (B))
MTMS: Methyltrimethoxysilane PTMS: Propyltrimethoxysilane HTMS: n-Hexyltrimethoxysilane DDTMS: Dodecyltrimethoxysilane HDTMS: Hexadecyltrimethoxysilane HTES: Hexyltriethoxysilane TEOS: Tetraethoxysilane

Example 1
1.00 g of CNC was dispersed in 70.00 g of ion-exchanged water, and then ultrasonic treatment was performed using Yamato Scientific's "LUH300" at 30% output for 3 minutes to obtain an aqueous dispersion. 130 g of ethanol, 0.97 g of DMAP, and 0.34 g of DDTMS were added to the aqueous dispersion. The molar ratio of DMAP/DDTMS was 4.0.
Then, 0.17 g of a 25% by mass aqueous ammonia solution was added as a pH adjuster to adjust the pH to 10.5. The mixture was stirred at room temperature (25°C) for 1 hour at 300 rpm using a magnetic stirrer. The mixture was then aged at room temperature (25°C) for 1 day to carry out a silane modification treatment of the nanocellulose, thereby obtaining a functional layer-forming resin composition (A-1) containing silane-modified nanocellulose.
Next, 2 mL of the functional layer-forming composition (A-1) was dropped onto the glass substrate and coated with a spin coater (ACT-400A II manufactured by Active Co., Ltd.) at 400 rpm for 1 minute. The resulting coating film was dried by heat treatment at 100° C. for 2 hours to obtain a cellulose-containing laminate 1 having a functional layer with a thickness of 127 nm.

Example 2
A functional layer-forming composition (A-2) containing silane-modified nanocellulose was obtained by carrying out the silane modification treatment of nanocellulose in the same manner as in Example 1, except that the amount of DMAPS used in Example 1 was changed to 1.05 g and HTMS: 0.26 g was added to the aqueous dispersion instead of DDTMS. The molar ratio of DMAPS/HTMS was 4.0.
Next, a cellulose-containing laminate 2 was obtained in the same manner as in Example 1, except that the functional layer-forming composition (A-2) was used.

Example 3
A functional layer-forming composition (A-3) containing silane-modified nanocellulose was obtained by carrying out the silane modification treatment of nanocellulose in the same manner as in Example 1, except that the amount of DMAP S used in Example 2 was changed to 0.69 g and the amount of HTMS used was changed to 0.46 g. The molar ratio of DMAP S / HTMS was 1.5.
Next, a cellulose-containing laminate 3 was obtained in the same manner as in Example 1, except that the functional layer-forming composition (A-3) was used.

<Comparative Example 1>
A functional layer-forming composition (A-4) containing silane-modified nanocellulose was obtained by carrying out the silane modification treatment of nanocellulose in the same manner as in Example 1, except that the amount of DMAPS used in Example 1 was changed to 1.12 g and 0.18 g of MTMS was added to the aqueous dispersion instead of DDTMS. The molar ratio of DMAPS/MTMS was 4.0.
Next, a cellulose-containing laminate 4 was obtained in the same manner as in Example 1, except that the functional layer-forming composition (A-4) was used.

<Comparative Example 2>
A functional layer-forming composition (A-5) containing silane-modified nanocellulose was obtained by carrying out the silane modification treatment of nanocellulose in the same manner as in Example 1, except that the amount of DMAPS used in Example 1 was changed to 1.09 g and 0.22 g of PTMS was added to the aqueous dispersion instead of DDTMS. The molar ratio of DMAPS/PTMS was 4.0.
Next, a cellulose-containing laminate 5 was obtained in the same manner as in Example 1, except that the functional layer-forming composition (A-5) was used.

<Comparative Example 3>
A functional layer-forming composition (A-6) containing silane-modified nanocellulose was obtained by carrying out the silane modification treatment of nanocellulose in the same manner as in Example 1, except that the amount of DMAPS used in Example 1 was changed to 0.92 g and 0.18 g of HDTMS was added to the aqueous dispersion instead of DDTMS. The molar ratio of DMAPS/HDTMS was 4.0.
Next, a cellulose-containing laminate 6 was obtained in the same manner as in Example 1, except that the functional layer-forming composition (A-6) was used.

<Comparative Example 4>
A functional layer-forming composition (A-7) containing silane-modified nanocellulose was obtained by carrying out the silane-modified treatment of nanocellulose in the same manner as in Example 1, except that the amount of DMAPS used in Example 1 was changed to 0.46 g and 0.69 g of HTMS was added to the aqueous dispersion. The molar ratio of DMAPS/HTMS was 0.7.
Next, a cellulose-containing laminate 7 was obtained in the same manner as in Example 1, except that the functional layer-forming composition (A-7) was used.

Example 4
1.00 g of CNC was dispersed in 70.00 g of ion-exchanged water, and ultrasonic treatment was performed using Yamato Scientific's "LUH300" at 30% output for 3 minutes to obtain an aqueous dispersion. 130 g of ethanol, 0.26 g of TEOS, and 0.24 g of HTES were added to the aqueous dispersion. The molar ratio of HTES/TEOS was 0.8.
Thereafter, 0.17 g of a 25% by mass aqueous ammonia solution was added as a pH adjuster to adjust the pH to 10.5. The mixture was stirred at room temperature (25 ° C.) for 1 hour at 300 rpm using a magnetic stirrer. After aging at room temperature (25 ° C.) for 1 day, 0.46 g of DMAP was added to the solution, and the mixture was stirred again at 300 rpm for 2 hours using a magnetic stirrer to obtain a functional layer-forming resin composition (A-8) containing silane-modified nanocellulose.
Next, a cellulose-containing laminate 8 was obtained in the same manner as in Example 1, except that the functional layer-forming composition (A-8) was used.

<Measurement method and evaluation method>
(Functional layer film forming ability)
The uniformity of the film on the surface of each cellulose-containing laminate was visually evaluated according to the following criteria.
A: A uniform film was formed.
B: There were partial defects in the film.
C: Film defects were observed over the entire surface.

(Functional layer thickness)
The cellulose-containing laminate of each example was cut in the thickness direction, and the cut surface was observed using a scanning white light interference microscope (VertScan (registered trademark) manufactured by Ryoka Systems Co., Ltd.) to measure the thickness of the functional layer.

(Switching of Water Contact Angle by pH Change)
For each example of the cellulose-containing laminate, the water contact angle of the functional layer surface was measured using a contact angle meter (Kyowa Chemical Industry Co., Ltd. product "Drop Master 500"). The measurement conditions were 23 ° C. and 50% RH. The volume of the water droplet was 10 μL. In the measurement using a water droplet with a pH of 7, the measurement of the water contact angle was started 1 second after the water droplet was dropped, and the measured value was adopted 1 second after the start of the measurement. In the measurement using a water droplet with a pH of 2, the measurement of the water contact angle was started 1 second after the water droplet was dropped, and the measured value was adopted 60 seconds after the start of the measurement.

(Water contact angle switching by carbon dioxide treatment)
50 mL of ion-exchanged water was added to a 450 mL glass bottle, and a bubbling treatment was performed using 5 L of carbon dioxide gas. The laminate was immersed in water in which carbon dioxide gas was dissolved at room temperature for 1 hour, and then the moisture on the laminate surface was removed with carbon dioxide gas and dried. Thereafter, the water contact angle of the functional layer surface was measured using a contact angle meter (Kyowa Chemical Industry Co., Ltd. product "Drop Master 500"). The measurement conditions were 23 ° C. and 50% RH. The water droplet volume was 10 μL, the pH was 7, and the measured value was adopted 1 second after the start of measurement when the measurement was started 1 second after the water droplet was dropped.

<Results>
The results of the functional layer film-forming properties, the functional layer thickness, and the water contact angle are shown in Table 1.

In Examples 1 to 3, a laminate whose wettability can be controlled by pH was produced. In Example 2, it was confirmed that wettability can also be controlled by carbon dioxide. Examples 1 and 3 also contain silane-modified nanocellulose having a tertiary amine structure, and the tertiary amino group is difficult to cover, so it is considered that wettability can be controlled by carbon dioxide, as in Example 2.
In Comparative Examples 1 and 2, it is believed that the number of carbon atoms in the alkyl group of the silane compound (B) was small, and as a result, the surface was covered with tertiary amino groups, and as a result, the water contact angle at pH 7 did not increase.
In Comparative Example 3, it is believed that the water contact angle at pH 2 did not decrease because the number of carbon atoms in the alkyl group of the silane compound (B) was large and the tertiary amino group was covered.
In Comparative Example 4, the amount of the silane compound (B) was greater than that of the tertiary amine structure-containing silane compound (A), which is believed to have caused the low responsiveness to pH. In addition, in Comparative Example 4, the change in water contact angle due to carbon dioxide was small, and the responsiveness was low.
In Example 4, a laminate in which the wettability can be controlled by pH was produced by using a plurality of silanes and sequentially condensing the silanes. In addition, in Example 4, it was confirmed that the wettability can also be controlled by carbon dioxide.

The present invention provides a functional material that has good film-forming properties and can change the wettability of its surface by using an external stimulus as a trigger.

Claims (9)

A base layer;
A functional layer containing silane-modified nanocellulose having a tertiary amine structure;
having
the water contact angle of the surface of the functional layer is 70 degrees or more when measured in water of pH 7;
A laminate, wherein the water contact angle of the surface of the functional layer is 30 degrees or less when measured in water of pH 2. The laminate according to claim 1, wherein the silane-modified nanocellulose is a reaction product of nanocellulose and two or more types of alkoxysilanes. The two or more alkoxysilanes are
A silane compound (A) having a tertiary amine structure;
a silane compound (B) having an alkyl group and not having a tertiary amine structure;
The laminate of claim 2 comprising: The laminate according to claim 3, wherein the silane compound (A) is at least one selected from the group consisting of (N,N-dimethylaminopropyl)trimethoxysilane and (N,N-diethylaminopropyl)trimethoxysilane. The laminate according to claim 3, wherein the silane compound (B) has an alkyl group having 6 to 12 carbon atoms. The laminate according to claim 3 , wherein a molar ratio M _A /M _B of the silane compound (A) to the silane compound (B) is 1.5 or more. The laminate according to any one of claims 1 to 6, wherein the nanocellulose is cellulose nanocrystals. The laminate according to any one of claims 1 to 6, wherein the thickness of the functional layer is 10 to 1,000 nm. The laminate according to any one of claims 1 to 6, wherein the substrate layer is a resin film, a fibrous substrate, or a glass substrate.