JP2023007055A - Nanocellulose-containing laminate, and method of producing the same - Google Patents

Abstract

To provide a nanocellulose-containing laminate having good productivity and water repellency, and a method of producing the same.SOLUTION: A nanocellulose-containing laminate pertaining to one embodiment of the present invention includes: a functional layer containing a silane-modified cellulose; and a substrate layer, where the water drop contact angle of the functional layer is 90° or more. A method of producing a nanocellulose laminate pertaining to one embodiment of the present invention includes: a coating liquid-preparing process of preparing a coating liquid composed of a composition for forming a functional layer including nanocelulose, and at least one alkoxysilane selected from the group consisting of monoalkoxysilane, dialkoxysilane, trialkoxysilane, and tetraethoxysilane; a coated film-forming process of applying the coating liquid onto the substrate layer to form a coated film; and a heat treatment process of subjecting the coated film to heat treatment to obtain the functional layer containing the silane-modified nanocellulose, where the water drop contact angle of the surface of the functional layer is 90° or more.SELECTED DRAWING: None

Description

TECHNICAL FIELD The present invention relates to a nanocellulose-containing laminate and a method for producing the same.

In recent years, from the perspective of a circular economy (sustainable society), high-performance materials using plant-derived materials have been attracting attention. A proposal is made.

Chemically modified nanocellulose materials, which are obtained by chemically modifying the surface of cellulose nanomaterials, are being studied for application to various uses because they are excellent in transparency and functionality.
For example, Patent Literature 1 discloses a technique of applying a coating liquid containing cellulose nanofibers and inorganic fine particles onto a base film to improve the mechanical strength.
In addition, Patent Document 2 discloses a functional material using silica xerogel or silica airgel and cellulose nanofibers, which are chemically bonded, as a heat insulating material.
Furthermore, in Non-Patent Document 1, a study is made on applying a silylation treatment by dipping to a cellulose nanofiber aerogel prepared by freeze-drying and applying it as an oil-water separation membrane.

JP 2010-155427 A JP 2014-237910 A

S.Zhou et al.,ACS Sustainable Chem.Eng.2016,4,6409-6416

In the technique described in Patent Document 1, it is assumed that the water repellency is inferior due to the influence of hydroxyl groups abundantly present on the surface of nano-sized cellulose. For example, in applications exposed to water, such as exterior materials, if the water repellency is poor, problems arise in terms of durability and the like.
In addition, the techniques described in Patent Document 2 and Non-Patent Document 1 include processes such as freeze-drying and dipping, which are difficult to achieve continuous production with batch processes or general-purpose equipment, and are not suitable for high-efficiency production. It is assumed that there is.

Therefore, an object of the present invention is to provide a nanocellulose-containing laminate with good productivity and good water repellency, and a method for producing the same.

The present invention has the following aspects.

[1] A nanocellulose-containing laminate having a functional layer containing silane-modified nanocellulose and a substrate layer, wherein the functional layer has a water droplet contact angle of 90 degrees or more.
[2] The nanocellulose-containing laminate according to [1] above, wherein the functional layer has a surface roughness Sa of 5 nm or more.
[3] The nanocellulose-containing laminate according to [1] or [2] above, wherein the functional layer has a total light transmittance of 85% or more.

[4] The above [ 1] The nanocellulose-containing laminate according to any one of [3].

[5] The nanocellulose-containing laminate according to [4] above, wherein the monoalkoxysilane is at least one selected from the group consisting of trimethylmethoxysilane and trimethylethoxysilane.

[6] The nanocellulose-containing laminate according to [4] or [5] above, wherein the dialkoxysilane is a compound represented by the following general formula (1).

Here, in formula (1) above, R ¹ and R ³ are alkyl groups having 1 to 8 carbon atoms, and R ¹ and R ³ may be the same or different. R ² and R ⁴ are alkyl groups having 1 to 3 carbon atoms, and R ² and R ⁴ may be the same or different.

[7] The nanocellulose-containing laminate according to [6] above, wherein the dialkoxysilane is at least one selected from the group consisting of dimethyldimethoxysilane and dimethyldiethoxysilane.

[8] The nanocellulose-containing laminate according to any one of [4] to [7] above, wherein the trialkoxysilane is a compound represented by the following general formula (2).

Here, in the above formula (2), R ⁵ is an alkyl group having 1 to 8 carbon atoms. R ⁶ to R ⁸ are alkyl groups having 1 to 3 carbon atoms, and R ⁶ to R ⁸ may be the same or different.

[9] The trialkoxysilane is selected from the group consisting of methyltrimethoxysilane, methyltriethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, n-hexyltrimethoxysilane and n-hexyltriethoxysilane. The nanocellulose-containing laminate according to [8] above, which is at least one selected.
[10] The nanocellulose-containing laminate according to any one of [4] to [9] above, wherein the tetraalkoxysilane is at least one selected from the group consisting of tetramethoxysilane and tetraethoxysilane.
[11] The above, wherein the molar ratio A/B of the total content (A) of the monoalkoxysilane, the dialkoxysilane and the trialkoxysilane to the content (B) of the tetraalkoxysilane exceeds 1.0. [4] The nanocellulose-containing laminate according to any one of [10].

[12] The nanocellulose-containing laminate according to any one of [1] to [11] above, wherein the functional layer has a thickness of 10 to 1,000 nm.
[13] The nanocellulose-containing laminate according to any one of [1] to [12] above, wherein the substrate layer is a resin film, fibrous substrate or glass.

[14] A coating solution is prepared from a composition for forming a functional layer containing nanocellulose and at least one alkoxysilane selected from the group consisting of monoalkoxysilane, dialkoxysilane, trialkoxysilane and tetraethoxysilane. , a coating liquid preparation step;
A coating film forming step of applying the coating liquid to a base material layer to form a coating film;
A heat treatment step of heat-treating the coating film to obtain a functional layer containing silane-modified nanocellulose,
A method for producing a nanocellulose-containing laminate, wherein the functional layer surface has a water droplet contact angle of 90 degrees or more.

[15] A first coating step of applying a first coating liquid containing nanocellulose to the substrate layer;
A second coating liquid containing at least one alkoxysilane selected from the group consisting of monoalkoxysilane, dialkoxysilane, trialkoxysilane and tetraethoxysilane is applied to the substrate layer surface coated with the first coating liquid. a second application step of applying to
A heat treatment step of heat-treating the coating film to obtain a functional layer containing silane-modified nanocellulose,
A method for producing a nanocellulose-containing laminate, wherein the functional layer surface has a water droplet contact angle of 90 degrees or more.

The nanocellulose-containing laminate of the present invention has good water repellency because the water droplet contact angle on the surface of the functional layer is 90 degrees or more. In addition, since the nanocellulose-containing laminate of the present invention can be produced by applying a coating liquid composed of a composition for forming a functional layer to a substrate and heat-treating the substrate, continuous production is possible and productivity is high.

Next, an example of an embodiment of the invention will be described in detail. However, the present invention is not limited to the following embodiments, and various modifications can be made within the scope of the gist of the present invention.

<Nanocellulose-containing laminate>
A nanocellulose-containing laminate (hereinafter also referred to as "this laminate") according to an example of the embodiment of the present invention includes a functional layer containing silane-modified nanocellulose (hereinafter also referred to as "this functional layer") and a substrate. and a material layer.

In the present invention, "nanocellulose" is cellulose crushed to nano level by mechanical or chemical treatment. Containment of "nanocellulose" can be determined by observation with an electron microscope, IR spectroscopy, or the like.
"Silane-modified nanocellulose" means a reaction product of nanocellulose and silane, for example, a dehydration condensation reaction product, and the content of "silane-modified nanocellulose" can be determined by XPS elemental analysis or the like.

Each layer constituting the laminate will be described below.

1. Present Functional Layer The present functional layer of the present laminate contains silane-modified nanocellulose as a main material.
In this case, the main material means a material having the highest mass ratio among the materials constituting the functional layer. It may account for 70% by mass or more, more than 80% by mass, and more than 90% by mass (including 100% by mass).
The functional layer may contain unmodified nanocellulose. In that case, the amount of silane-modified nanocellulose is preferably greater than the amount of unmodified nanocellulose.

The silane-modified nanocellulose of the functional layer is a reaction product of nanocellulose and at least one alkoxysilane selected from the group consisting of monoalkoxysilane, dialkoxysilane, trialkoxysilane and tetraethoxysilane, such as a dehydration condensation reaction. It is preferably an object.

From the viewpoint of water repellency, the functional layer preferably has a water droplet contact angle of 90 degrees or more, more preferably 95 degrees or more. The upper limit of the water droplet contact angle is not particularly limited, and may be, for example, 150 degrees or less.
The water droplet contact angle can be measured with a contact angle meter (Drop Master 500, manufactured by Kyowa Kagaku Co., Ltd.).

The surface roughness Sa (ISO 25178) of this functional layer is preferably 5 nm or more, more preferably 10 nm or more. Although the upper limit of the surface roughness Sa is not particularly limited, it is preferably 1000 nm or less, more preferably 500 nm or less.
If the surface roughness Sa of the present functional layer is within the above range, the water droplet contact angle on the surface of the functional layer can be increased, and the water repellency can be improved.
The uneven surface structure of this functional layer can be formed, for example, by the sol-gel reaction and phase separation described below.
The surface roughness Sa (ISO 25178) represents the arithmetic average height, that is, the average of the absolute values of the difference in height of each point with respect to the average plane of the surface. It can be measured using "VertScan (registered trademark)" manufactured by Kagaku System Co., Ltd.).

The total light transmittance of this functional layer is preferably 85% or more, more preferably 90% or more, with an upper limit of 100%.
The haze of the functional layer is preferably 0% or more and 30% or less, more preferably 1% or more or 25% or less, more preferably 5% or more or 22% or less, and more preferably 10% or more or 20% or less. is even more preferable.

When the total light transmittance and haze of the functional layer are within the above ranges, the transparency of the laminate can be improved while the contact angle of water droplets can be further increased by the uneven structure of the surface, and visibility is required. It can also be applied to other applications.
The total light transmittance and haze can be measured according to JIS K 7136 with a haze meter "HM-150" manufactured by Murakami Color Laboratory.

The thickness of the functional layer is preferably 10 to 1,000 nm, more preferably 50 nm or more or 500 nm or less, and even more preferably 100 nm or more or 300 nm or less, from the viewpoint of improving the strength of the coating film and preventing cracks.

[Composition for forming functional layer]
The functional layer of the laminate is a composition for forming a functional layer containing nanocellulose and at least one alkoxysilane selected from the group consisting of monoalkoxysilane, dialkoxysilane, trialkoxysilane, and tetraethoxysilane ( Hereinafter, it is also referred to as "this functional layer-forming composition").

In the present invention, the reason why the present functional layer has good water repellency is not clear, but the following may be considered, for example.
Both the dehydration condensation reaction of nanocellulose and alkoxysilane and the condensation reaction between hydrolyzed alkoxysilanes, the so-called sol-gel reaction, which occur when forming the functional layer, improve the surface roughness of the functional layer. is thought to contribute to For example, after a dehydration condensation reaction occurs between nanocellulose and alkoxysilane, phase separation occurs within the functional layer coating film due to hydrophobic interactions derived from alkyl groups, and a structure is formed in which the alkyl groups aggregate. At this time, since this structure is coarser than the sol-gel reaction simply occurs, it can be considered that the surface becomes rough and the water droplet contact angle increases.
In addition, the dehydration condensation reaction between nanocellulose and alkoxysilane reduces the proportion of hydroxyl groups in nanocellulose, ie, polar groups in the functional layer, and thus may contribute to the improvement of water repellency as a functional layer.

The functional layer-forming composition will be described below.

(Nanocellulose)
Examples of nanocellulose contained in the functional layer-forming composition include long fibrous cellulose nanofibers (CNF) and highly crystalline cellulose nanocrystals (CNC). Cellulose nanocrystals are preferable from the viewpoint that the viscosity of the composition does not easily increase even when added, and the handling properties when applied to the base material layer are improved.

From the viewpoint of improving the transparency of the functional layer, the average fiber diameter of nanocellulose is preferably 0.1 nm or more and 100 nm or less, more preferably 0.5 nm or more or 50 nm or less, and more preferably 1 nm or more or 20 nm or less. preferable.
The average fiber length of nanocellulose is preferably 1 nm or more and 1000 nm or less, more preferably 5 nm or more and 500 nm or less, and even more preferably 10 nm or more and 200 nm or less, from the viewpoint of improving the transparency of the functional layer.
The average aspect ratio (fiber length/fiber diameter) of nanocellulose is preferably 1 or more and 500 or less, more preferably 10 or more or 200 or less, and even more preferably 20 or more or 100 or less. When the average aspect ratio is within the above range, the composition for forming a functional layer is less likely to thicken and has good handleability.
In addition, the average fiber diameter, average fiber length and average aspect ratio of nanocellulose are obtained by observing fibers dispersed in the nanocellulose aqueous dispersion or the functional layer forming coating liquid with a scanning electron microscope or the like. Preferably, it can be obtained from the average value of 100 selected and measured.

(Alkoxysilane)
The alkoxysilane contained in the functional layer-forming composition may be at least one selected from the group consisting of monoalkoxysilane, dialkoxysilane, trialkoxysilane, and tetraethoxysilane. Two or more of these may be used.

Examples of the monoalkoxysilane include at least one selected from the group consisting of trimethylmethoxysilane and trimethylethoxysilane. One or more of these may be used.

As the dialkoxysilane, a compound represented by the following general formula (1) is preferable.

Here, in formula (1), R ¹ and R ³ are alkyl groups having 1 to 8 carbon atoms, and R ¹ and R ³ may be the same or different. R ² and R ⁴ are alkyl groups having 1 to 3 carbon atoms, and R ² and R ⁴ may be the same or different.

Specific examples of the dialkoxysilane include dimethyldimethoxysilane, dimethyldiethoxysilane, dimethyldiethoxysilane, diethyldiethoxysilane, diisobutyldimethoxysilane, dimethoxymethyl-n-octylsilane, and the like. One or more of these may be used.
Among them, at least one selected from the group consisting of dimethyldimethoxysilane and dimethyldiethoxysilane is preferable. One or more of these may be used.

As the trialkoxysilane, a compound represented by the following general formula (2) is preferable.

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

Specific examples of the trialkoxysilane include methyltrimethoxysilane, methyltriethoxysilane, methyltripropoxysilane, methyltriisopropoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, ethyltripropoxysilane, ethyl triisopropoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, n-propyltripropoxysilane, n-propyltriisopropoxysilane, isopropyltrimethoxysilane, isopropyltrimethoxysilane, isopropyltripropoxysilane, n -butyltriethoxysilane, isobutyltrimethoxysilane, isobutyltriethoxysilane, n-hexyltrimethoxysilane, n-hexyltriethoxysilane, n-octyltriethoxysilane, allyltrimethoxysilane, allyltriethoxysilane, etc. can be done. One or more of these may be used.
Among them, the trialkoxysilane is selected from the group consisting of methyltrimethoxysilane, methyltriethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, n-hexyltrimethoxysilane and n-hexyltriethoxysilane. At least one is preferred. One or more of these may be used.

Examples of the tetraalkoxysilane include tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, and the like. One or more of these may be used.
Among them, the tetraalkoxysilane preferably contains at least one selected from the group consisting of tetraethoxysilane and tetramethoxysilane. One or more of these may be used.

Among the above, the functional layer-forming composition preferably contains at least one selected from the group consisting of alkyl group-containing monoalkoxysilanes, dialkoxysilanes and trialkoxysilanes, and contains an alkyl group. It is more preferable to contain dialkoxysilane and/or trialkoxysilane, and contain dialkoxysilane represented by the general formula (1) and/or trialkoxysilane represented by the general formula (2). is more preferred.
By containing monoalkoxysilanes, dialkoxysilanes and trialkoxysilanes containing alkyl groups, the ratio of hydrophobic groups in the functional layer is increased, so that the hydrophilicity of the functional layer is lowered and the water repellency is improved. Become.
In addition, when the monoalkoxysilane, dialkoxysilane and trialkoxysilane containing the alkyl group are contained, after the dehydration condensation reaction between nanocellulose and alkoxysilane occurs, the hydrophobic interaction derived from the alkyl group causes functional layer coating. Phase separation occurs within the film and structures are formed such that the alkyl groups aggregate. After that, when the solvent is removed, it becomes porous, so the surface roughness increases and the water droplet contact angle increases. Since the structure produced by this phase separation is coarser than the sol-gel reaction described above, it is thought that the water droplet contact angle is also higher.

Furthermore, it preferably contains at least one selected from the group consisting of monoalkoxysilanes, dialkoxysilanes and trialkoxysilanes containing alkyl groups, and tetraalkoxysilanes, and dialkoxysilanes containing alkyl groups and / or it is more preferable to contain a trialkoxysilane and a tetraalkoxysilane, and the dialkoxysilane represented by the above general formula (1) and / or the trialkoxysilane represented by the above general formula (2), It is more preferable to contain tetraalkoxysilane.
By using at least one selected from the group consisting of alkyl group-containing monoalkoxysilanes, dialkoxysilanes and trialkoxysilanes together with tetraalkoxysilane, condensation and phase separation with nanocellulose progress stepwise. As a result, a complex uneven structure is formed and the water droplet contact angle increases.

In the functional layer forming composition, the molar ratio A/B of the total content (A) of monoalkoxysilane, dialkoxysilane and trialkoxysilane to the content (B) of tetraalkoxysilane is 1.0. It is preferable to exceed, and 1.2 or more is preferable. Although the upper limit is not particularly limited, it is preferably 10 or less, more preferably 5 or less, and even more preferably 3 or less.
When the molar ratio A/B is within the above range, condensation with nanocellulose and phase separation can be progressed step by step, a complex uneven structure can be formed, and the amount of alkyl groups in the functional layer increases. , the water repellency is improved.

(solvent)
The functional layer-forming composition may contain a solvent.
As the solvent, for example, in order to improve the reactivity between nanocellulose and alkoxysilane and the coatability to the substrate layer, water, alcohol, or a mixture thereof (hereinafter collectively referred to as "water/alcohol Also referred to as "system") is preferred.

When a water/alcohol solvent is used as the solvent, the water content in 100% by mass of the solvent is preferably 15% by mass or more and 75% by mass or less, and more preferably 30% by mass or more or 50% by mass or less.
When the water content is at least the above lower limit value, the dispersibility of nanocellulose is improved and it becomes difficult to agglomerate. On the other hand, when the water content is equal to or less than the above upper limit, it becomes easier to control the condensation reaction of silane.

(Other ingredients)
The functional layer-forming composition may contain a basic substance for pH adjustment. Examples of basic substances include ammonia and the like.
From the point of view of safety in handling, the functional layer-forming composition preferably has a pH of 7 to 12.

(Content of each component)
The content of nanocellulose in the functional layer-forming composition is preferably 0.1% by mass or more and 5% by mass or less, and more preferably 0.2% by mass or more or 3% by mass or less. When the content of nanocellulose is within the above range, the coating amount can be easily controlled, and the viscosity is less likely to increase, resulting in good handleability during coating on the substrate layer.

In addition, the content of silane in the functional layer-forming composition is preferably 1% by mass or more and 20% by mass or less, and more preferably 2% by mass or more or 10% by mass or less. When the silane content is within the above range, the pot life and the selectivity of the coating method are improved.

The content ratio of nanocellulose to alkoxysilane (nanocellulose/alkoxysilane) in the functional layer-forming composition is preferably 5/95 to 40/60, more preferably 10/90 to 30/70. When the content mass ratio is within the above range, gelation due to the condensation reaction between alkoxysilanes hardly occurs, and the dehydration condensation reaction between nanocellulose and alkoxysilane proceeds favorably, resulting in good water repellency.

2. Base Material Layer Although the material of the base material layer of the present invention is not particularly limited, it is preferably a resin film, a fibrous base material, or glass.

Examples of resin films include polyolefin resins such as polyethylene and polypropylene; polyester resins such as polyethylene terephthalate, polyethylene isophthalate, polyethylene naphthalate, and polybutylene terephthalate; polylactic acid; polyurethane; polyvinyl acetate; Vinyl: Films made of thermoplastic resins such as polycarbonate resins can be mentioned. The resin film may be a porous film subjected to a porosification treatment such as chemical foaming, physical foaming, stretching, or the like, or a stretched film subjected to a uniaxial or biaxial stretching treatment.

Examples of fibrous substrates include chemical fibers such as polyester fiber, nylon fiber, acrylic fiber, polyurethane fiber, acetate fiber, rayon fiber, and polylactic acid fiber; cotton, hemp, silk, wool, and blended fibers thereof. nonwoven fabrics, woven fabrics, knitted fabrics, and the like.

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

Additives may be added to the base material as needed. can also be blended. If necessary, conventionally known antioxidants, antistatic agents, heat stabilizers, lubricants, dyes, pigments, etc. can be added.

The substrate may be subjected to surface treatment such as corona treatment, plasma treatment, or coating treatment for adjusting wettability on the surface on which the functional layer is formed.

3. Other Layers The laminate may include layers other than the functional layer and the substrate layer. For example, another layer may be provided between the functional layer and the substrate layer, or on the side of the substrate layer opposite to the functional layer.
Other layers include, for example, a primer layer, a stress relaxation layer, and the like, which improve the adhesion between the substrate and the functional layer.

<Method for producing nanocellulose-containing laminate>
Next, a method for producing a nanocellulose-containing laminate according to an example of the embodiment of the present invention will be described.

[First manufacturing method]
A first method for producing the present laminate is for forming the present functional layer containing nanocellulose and at least one alkoxysilane selected from the group consisting of monoalkoxysilane, dialkoxysilane, trialkoxysilane, and tetraethoxysilane. A coating liquid preparation step of preparing a coating liquid composed of a composition, a coating film forming step of applying the coating liquid to a base layer to form a coating film, and a heat treatment of the coating film to silane-modified and a heat treatment step to obtain a functional layer containing nanocellulose.
In addition, if the first manufacturing method of the present laminate includes the above steps, it is possible to optionally add other treatments or steps.

Further, in the present invention, the "process" may or may not be performed in a series of production lines. Moreover, the treatment in one step may be performed intermittently, and in that case, it may be performed intermittently by setting a time interval, changing the apparatus, or changing the location. Alternatively, it may be carried out in a series of production lines with other processes. That is, a plurality of steps may be performed using the same device.

1. Coating Liquid Preparing Step In the coating liquid preparing step, nanocellulose and alkoxysilane are mixed in a solvent to prepare a coating liquid composed of the functional layer-forming composition.
The functional layer-forming composition and its components are as described above.

From the viewpoint of increasing the dispersibility of nanocellulose in the coating liquid, a method of dispersing nanocellulose in a solvent and then adding alkoxysilane is preferred. When adjusting the pH, it is preferable to add a basic substance in this step.
After mixing the nanocellulose and alkoxysilane, heating may be performed to increase reactivity. Although nanocellulose and alkoxysilane are reacted by simply mixing them, the reaction can be accelerated by heating.
The heating temperature and heating time may be any conditions as long as the reaction between nanocellulose and alkoxysilane proceeds. is more preferred. The heating time is preferably 30 seconds to 2 hours, more preferably 30 minutes or longer or about 1 hour.
After the heating, the substrate may be cured at room temperature for 1 to 7 days in order to promote the unreacted silane reaction.

The mass ratio of the amount of nanocellulose and alkoxysilane added (nanocellulose/alkoxysilane) is preferably 5/95 to 40/60, more preferably 10/90 to 30/70. Within the above range, gelling due to the condensation reaction between alkoxysilanes hardly occurs, and the dehydration condensation reaction between nanocellulose and alkoxysilane proceeds favorably, resulting in good water repellency of the surface of the functional layer.

2. Coating Film Forming Step In the coating film forming step, the coating liquid is applied to the substrate layer to form a coating film.
The method of applying the coating liquid to the substrate layer may be a known method, for example, comma coating method, gravure coating method, reverse coating method, knife coating method, dip coating method, spray coating method, air knife coating method, A spin coating method, a roll coating method, a printing method, a dipping method, a slide coating method, a curtain coating method, a die coating method, a casting method, a bar coating method, and an extrusion coating method can be used.
The thickness of the coating film is preferably 10 to 1,000 nm. When the thickness of the coating film is equal to or greater than the above lower limit, control during coating is facilitated. When the thickness of the coating film is equal to or less than the above upper limit, cracks due to shrinkage during drying and silane condensation are less likely to occur.

3. Heat Treatment Step In the heat treatment step, the coating film is dried by heat treatment to form the present functional layer containing silane-modified nanocellulose.

The drying method may be a known method.
The drying temperature and drying time may be any conditions as long as the solvent is removed from the coating film and the dehydration condensation of the alkoxysilane proceeds well. For example, the drying temperature is preferably 60 to 150 ° C., especially More preferably, the temperature is 80°C or higher or 120°C or lower. The drying time is preferably 30 seconds to 5 hours, more preferably 30 minutes or more or 2 hours or less.

[Second manufacturing method]
The second method for producing the laminate includes a first coating step of coating a base material layer with a first coating liquid containing nanocellulose, and monoalkoxysilane, dialkoxysilane, trialkoxysilane, and tetraethoxysilane. A second coating step of applying a second coating liquid containing at least one alkoxysilane selected from the group consisting of the first coating liquid to the substrate layer surface coated with the first coating liquid, and heating the coating film a heat treatment step to obtain a functional layer containing silane-modified nanocellulose.
In addition, in the second manufacturing method of the laminate, the order of the first coating step and the second coating step may be reversed, but the above order is preferable from the viewpoint of water repellency.
Further, if the above steps are provided, it is possible to optionally add other processing or steps.

Even if the coating liquid containing nanocellulose and the coating liquid containing alkoxysilane are separately applied as in the second manufacturing method, if the two are in contact with each other during the heat treatment, the contact portion A reaction between nanocellulose and alkoxysilane, for example, a sol-gel reaction proceeds to form silane-modified nanocellulose.

1. First Coating Step In the first coating step, a first coating liquid in which nanocellulose is dispersed in a solvent is coated on the substrate layer.
The method of applying the first 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, and an air knife. A coating method, a spin coating method, a roll coating method, a printing method, a dipping method, a slide coating method, a curtain coating method, a die coating method, a casting method, a bar coating method, an extrusion coating method, and the like can be mentioned.
Drying may be performed after applying the first coating liquid to the substrate layer. The drying temperature and drying time may be any conditions as long as the solvent is removed from the coating film. For example, the drying temperature is preferably 60 to 150 ° C., more preferably 80 ° C. or higher or 120 ° C. or lower. preferable. The drying time is preferably 10 seconds to 1 hour, more preferably 30 seconds or more or 30 minutes or less.

2. Second Coating Step In the second coating step, a second coating liquid obtained by adding alkoxysilane to a solvent is coated on the surface of the substrate layer coated with the first coating liquid. When adjusting the pH, it is preferable to add a basic substance to the second coating liquid.
The method of applying the second coating liquid to the substrate layer surface may be the same as the first coating step.

In addition, after preparing the second coating liquid, heating may be performed in order to increase the reactivity. Nanocellulose and alkoxysilane react even when they come into contact with each other, but the reaction can be accelerated by heating.
The heating temperature and the heating time may be any conditions as long as the reaction proceeds. For example, the heating temperature is preferably 30 to 80°C, more preferably 40°C or higher or 70°C or lower. The heating time is preferably 30 seconds to 2 hours, more preferably 30 minutes or more or 1 hour or less.
After the heating, the substrate may be cured at room temperature for 1 to 7 days in order to promote the unreacted silane reaction.

3. Heat Treatment Step In the heat treatment step, the coating film is dried by heat treatment to form the present functional layer.
The drying method, drying temperature and drying time may be the same as in the heat treatment step in the first production method.

<Application>
Since this laminate is excellent in water repellency, it can be suitably used for various exterior materials, interior materials, separation membranes, and the like. Examples thereof include building materials such as walls and roofs of building structures such as general residences and public facilities; interior and exterior parts for vehicles such as cars, trains, ships and airplanes; members for home electric appliances;
In addition, since the laminate exhibits high water repellency in raw materials based on non-exhaustible resource raw materials, it can be applied as various functional materials. In addition, it is known that by selecting the optimum composition, high transparency can be obtained, and it can be applied to applications where visibility and the like are required.

<Explanation of terms>
In the present invention, when expressing “X to Y” (X and Y are arbitrary numbers), unless otherwise specified, “X or more and Y or less” and “preferably larger than X” or “preferably larger than Y” It also includes the meaning of "small".
In addition, when expressed as "X or more" (X is an arbitrary number) or "Y or less" (Y is an arbitrary number), "preferably larger than X" or "preferably less than Y" It also includes intent.

EXAMPLES Hereinafter, the nanocellulose-containing laminate of the present invention will be described in more detail based on examples. In addition, the nanocellulose-containing laminate of the present invention is not limited at all by the following examples and comparative examples.

<Evaluation method>
(Thickness of functional layer)
Each cellulose-containing laminate obtained in Examples and Comparative Examples was cut in the thickness direction, and the cut surface was observed using a scanning white interference microscope (“VertScan (registered trademark)” manufactured by Ryoka System Co., Ltd.), The thickness of the functional layer was measured.

(water droplet contact angle)
For each cellulose-containing laminate obtained in Examples and Comparative Examples, the water droplet contact angle on the surface of the functional layer was measured using a contact angle meter (Kyowa Kagaku Co., Ltd., Drop Master 500).

(Surface roughness Sa)
The surface roughness Sa (ISO 25178) of the functional layer of each cellulose-containing laminate obtained in Examples and Comparative Examples was measured using a scanning white light interference microscope ("VertScan (registered trademark)" manufactured by Ryoka Systems Co., Ltd.). bottom.

(total light transmittance, haze)
According to JIS K 7136, the total light transmittance and haze of each cellulose-containing laminate obtained in Examples and Comparative Examples were measured using a haze meter "HM-150" manufactured by Murakami Color Laboratory.

<Preparation of composition for forming functional layer>
Functional layer-forming compositions (A-1) to (A-5), (a-1), (a-2), (A-101) and (A-102) were prepared according to Preparation Examples 1 to 8 below. prepared.

[Preparation Example 1]
Disperse 1.00 g of nanocellulose (“NCV-100” manufactured by Celluforce, CNC in the table) in 70.00 g of ion-exchanged water, and use “LUH300” manufactured by Yamato Scientific Co., Ltd. under the conditions of 30% output for 3 minutes. Ultrasonic treatment was performed to obtain an aqueous dispersion. To this aqueous dispersion, 130 g of ethanol, 5.00 g of methyltriethoxysilane (MTES), and 0.67 g of an aqueous ammonia solution (25 wt %) as a pH adjuster were added to adjust the pH to 10.5. ° C.) for 1 hour at 300 rpm using a magnetic stirrer. Next, after stirring at 300 rpm for 1 hour at 60° C., curing at room temperature (25° C.) for 4 days, silane modification treatment of nanocellulose is performed, and functional layer forming composition containing silane-modified nanocellulose. A product (A-1) was obtained.

Nanocellulose (“NCV-100” manufactured by Celluforce) is a cellulose nanocrystal (CNC) with an average fiber diameter of 3 nm, an average fiber length of 76 nm, and an average aspect ratio (fiber length/fiber diameter) of 25.
Even when nanocellulose is modified with silane, it is expected that the average fiber diameter, average fiber length, and average aspect ratio (fiber length/fiber diameter) do not change before and after silane modification. The same applies to other embodiments.

[Preparation Example 2]
Instead of 5.00 g of methyltriethoxysilane (MTES), 2.19 g of tetraethoxysilane (TEOS) and 2.81 g of methyltriethoxysilane (MTES) were added to the aqueous dispersion (MTES/TEOS molar ratio=1. Except for 5), nanocellulose was subjected to silane modification treatment in the same manner as in Preparation Example 1 to obtain a functional layer-forming composition (A-2) containing silane-modified nanocellulose.

[Preparation Example 3]
Nanocellulose was produced in the same manner as in Preparation Example 2, except that propyltriethoxysilane (PTES) was used instead of methyltriethoxysilane (MTES) and the PTES/TEOS molar ratio was 1.5. A silane-modified treatment was performed to obtain a composition for forming a functional layer (A-3) containing silane-modified nanocellulose.

[Preparation Example 4]
Nanoparticles were prepared in the same manner as in Preparation Example 2, except that instead of methyltriethoxysilane (MTES), n-hexyltriethoxysilane (HTES) was used so that the molar ratio of HTES/TEOS was 1.5. Silane modification treatment of cellulose was performed to obtain a functional layer-forming composition (A-4) containing silane-modified nanocellulose.

[Preparation Example 5]
Nanocellulose was produced in the same manner as in Preparation Example 2, except that dimethyldiethoxysilane (DMDES) was used instead of methyltriethoxysilane (MTES) so that the DMDES/TEOS molar ratio was 1.5. A silane-modified treatment was performed to obtain a functional layer-forming composition (A-5) containing silane-modified nanocellulose.

[Preparation Example 6]
0.50 g of nanocellulose was dispersed in 100.00 g of ion-exchanged water and subjected to ultrasonic treatment at 30% output for 3 minutes to obtain a first coating liquid (a-1) containing nanocellulose.
As the functional layer forming coating liquid for the second coating step, 100.00 g of ethanol, 3.38 g of ion-exchanged water, 1.54 g of methyltriethoxysilane (MTES), 1.20 g of tetraethoxysilane (TEOS) (MTES/ TEOS molar ratio = 1.5) and 0.67 g of an aqueous ammonia solution (25 wt%) as a pH adjuster were added to adjust the pH to 10.5, and the mixture was stirred at room temperature (25°C) for 1 hour with a magnetic stirrer at 300 rpm. was stirred using Then, it was cured at room temperature (25° C.) for 15 days to obtain a second coating liquid (a-2).

[Preparation Example 7]
Disperse 1.00 g of nanocellulose (“NCV-100” manufactured by Celluforce) in 70.00 g of ion-exchanged water, and perform ultrasonic treatment using “LUH300” manufactured by Yamato Scientific Co., Ltd. under the conditions of 30% output for 3 minutes. to obtain an aqueous dispersion. 130 g of ethanol was added to this aqueous dispersion and mixed to obtain a composition for forming a functional layer (A-101).

[Preparation Example 8]
Nanocellulose ("NCV-100" manufactured by Celluforce) 0.5% by mass aqueous dispersion, colloidal silica ("Snowtech ST-N" manufactured by Nissan Chemical Industries, Ltd.) is added to the solid content so that the mass ratio is CNC: colloidal silica. = 90:10 to obtain a composition for forming a functional layer (A-102).

<Production of nanocellulose-containing laminate>
[Example 1]
2 mL of the composition for forming a functional layer (A-1) obtained in Preparation Example 1 was dropped onto a glass substrate, and a spin coater ("ACT-400AII" manufactured by Active Co., Ltd.) was used at 400 rpm for 1 minute. applied. The obtained coating film was dried and heat-treated at 100° C. for 2 hours to obtain a cellulose-containing laminate 1 having a functional layer with a thickness of 50 nm.

[Example 2]
A cellulose-containing laminate 2 was obtained in the same manner as in Example 1, except that the functional layer-forming composition (A-2) obtained in Preparation Example 2 was used.

[Example 3]
A cellulose-containing laminate 3 was obtained in the same manner as in Example 1, except that the functional layer-forming composition (A-3) obtained in Preparation Example 3 was used.

[Example 4]
A cellulose-containing laminate 4 was obtained in the same manner as in Example 1, except that the functional layer-forming composition (A-4) obtained in Preparation Example 4 was used.

[Example 5]
A cellulose-containing laminate 5 was obtained in the same manner as in Example 1, except that the functional layer-forming composition (A-5) obtained in Preparation Example 5 was used.

[Example 6]
2 mL of the first coating liquid (a-1) obtained in Preparation Example 6 was dropped onto a glass substrate, and was applied using a spin coater under the conditions of 400 rpm×1 minute. The resulting coating film was dried at 100° C. for 1 minute.
Next, 2 mL of the second coating liquid (a-2) was dropped on the same side as the layer coated with the nanocellulose, and coated under the same conditions using a spin coater. The obtained coating film was dried and heat-treated at 100° C. for 2 hours to obtain a cellulose-containing laminate 6 .

[Comparative Example 1]
A cellulose-containing laminate 101 was obtained in the same manner as in Example 1, except that the functional layer-forming composition (A-101) obtained in Preparation Example 7 was used.

[Comparative Example 2]
A cellulose-containing laminate 102 was obtained in the same manner as in Example 1, except that the functional layer-forming composition (A-102) obtained in Preparation Example 8 was used.

Table 1 shows the materials and evaluation results of the nanocellulose-containing laminates of Examples 1 to 6 and Comparative Examples 1 and 2.

In Examples 1 to 6, the water droplet contact angle on the surface of the functional layer containing silane-modified nanocellulose was 90 degrees or more, and laminates with good water repellency were obtained.
From Examples 1 to 6, when the composition for forming a functional layer contains an alkyl group-containing dialkoxysilane or an alkyl group-containing trialkoxysilane, the surface roughness Sa of the functional layer increases, and water droplets It was confirmed that the contact angle increased.
In Example 6, a coating liquid containing nanocellulose and a coating liquid containing alkoxysilane were applied in layers, and heated while in contact with each other to produce silane-modified nanocellulose.

On the other hand, it was confirmed from Comparative Example 2 that when the composition for forming a functional layer did not contain silane-modified nanocellulose, the functional layer had a low water droplet contact angle and poor water repellency.

The reason why the water droplet contact angle is larger in Example 1 than in Examples 2 and 4, which have larger surface roughness, is that the actual water droplet contact angle is "complicated in three-dimensional structure" and "tetra In the case of Examples 2 and 4 containing tetraalkoxysilane, the hydrophobicity is weaker than in Example 1 containing only alkoxysilane having an alkyl group. From the viewpoint of the balance, it can be considered that the water droplet contact angle of Example 1 is higher.

In the above examples, there is no example using a composition for forming a functional layer containing nanocellulose and monoalkoxysilane. When silane is contained, the same effect as when dialkoxysilane is contained can be expected.
Moreover, in the above examples, only glass is used as the base material. However, since the water repellency of the functional layer is not affected by the base material, even if a resin film or a fibrous base material is used as the base material, the same effect as glass is obtained from the viewpoint of productivity and water repellency. can be assumed to be obtained.

Claims (15)

A nanocellulose-containing laminate comprising a functional layer containing silane-modified nanocellulose and a substrate layer, wherein the surface of the functional layer has a water droplet contact angle of 90 degrees or more. The nanocellulose-containing laminate according to claim 1, wherein the functional layer has a surface roughness Sa of 5 nm or more. The nanocellulose-containing laminate according to claim 1 or 2, wherein the functional layer has a total light transmittance of 85% or more. Claims 1 to 3, wherein the silane-modified nanocellulose is a reaction product of nanocellulose and at least one alkoxysilane selected from the group consisting of monoalkoxysilane, dialkoxysilane, trialkoxysilane and tetraethoxysilane. Nanocellulose-containing laminate according to any one of. The nanocellulose-containing laminate according to claim 4, wherein the monoalkoxysilane is at least one selected from the group consisting of trimethylmethoxysilane and trimethylethoxysilane. The nanocellulose-containing laminate according to claim 4 or 5, wherein the dialkoxysilane is a compound represented by the following general formula (1).

(Here, in the above formula (1), R ¹ and R ³ are alkyl groups having 1 to 8 carbon atoms, and R ¹ and R ³ may be the same or different. R ² and R ⁴ is an alkyl group having 1 to 3 carbon atoms, and R ² and R ⁴ may be the same or different.) The nanocellulose-containing laminate according to claim 6, wherein the dialkoxysilane is at least one selected from the group consisting of dimethyldimethoxysilane and dimethyldiethoxysilane. The nanocellulose-containing laminate according to any one of claims 4 to 7, wherein the trialkoxysilane is a compound represented by the following general formula (2).

(Here, in the above formula (2), R ⁵ is an alkyl group having 1 to 8 carbon atoms, R ⁶ to R ⁸ are alkyl groups having 1 to 3 carbon atoms, and R ⁶ to R ⁸ are the same may be different.) At least the trialkoxysilane is selected from the group consisting of methyltrimethoxysilane, methyltriethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, n-hexyltrimethoxysilane and n-hexyltriethoxysilane. The nanocellulose-containing laminate according to claim 8, which is one type. The nanocellulose-containing laminate according to any one of claims 4 to 9, wherein the tetraalkoxysilane is at least one selected from the group consisting of tetramethoxysilane and tetraethoxysilane. Claims 4 to 4, wherein the molar ratio A/B between the total content (A) of the monoalkoxysilane, the dialkoxysilane and the trialkoxysilane and the content (B) of the tetraalkoxysilane exceeds 1.0. 11. The nanocellulose-containing laminate according to any one of 10. The nanocellulose-containing laminate according to any one of claims 1 to 11, wherein the functional layer has a thickness of 10 to 1,000 nm. The nanocellulose-containing laminate according to any one of claims 1 to 12, wherein the substrate layer is a resin film, fibrous substrate or glass. A coating liquid comprising a composition for forming a functional layer containing nanocellulose and at least one alkoxysilane selected from the group consisting of monoalkoxysilane, dialkoxysilane, trialkoxysilane and tetraethoxysilane. a preparation step;
A coating film forming step of applying the coating liquid to a base material layer to form a coating film;
A heat treatment step of heat-treating the coating film to obtain a functional layer containing silane-modified nanocellulose,
A method for producing a nanocellulose-containing laminate, wherein the functional layer surface has a water droplet contact angle of 90 degrees or more. A first coating step of coating a base layer with a first coating liquid containing nanocellulose;
A second coating liquid containing at least one alkoxysilane selected from the group consisting of monoalkoxysilane, dialkoxysilane, trialkoxysilane and tetraethoxysilane is applied to the substrate layer surface coated with the first coating liquid. a second application step of applying to
A heat treatment step of heat-treating the coating film to obtain a functional layer containing silane-modified nanocellulose,
A method for producing a nanocellulose-containing laminate, wherein the functional layer surface has a water droplet contact angle of 90 degrees or more.