JP5616056B2 - Method for producing film-shaped molded body - Google Patents

Description

  The present invention relates to a gas barrier material from which a film or the like capable of suppressing permeation of various gases such as water vapor, oxygen, carbon dioxide and nitrogen, a gas barrier molded article using the same, and a method for producing the same.

  Since current gas barrier materials such as oxygen and water vapor are mainly produced from fossil resources, they are non-biodegradable and must be incinerated. Therefore, it has been studied to produce a biodegradable oxygen barrier material using reproducible biomass as a raw material.

  Patent Document 1 is an invention relating to a coating agent containing microcrystalline cellulose and a laminated material in which the coating agent is applied to a substrate. It is described that the microcrystalline cellulose powder as a raw material preferably has an average particle size of 100 μm or less, and in the examples, only those having an average particle size of 3 μm and 100 μm are used. There is no description about the miniaturization treatment, and there is room for improvement in the denseness and film strength of the applied coating agent layer and the adhesion to the substrate.

  Furthermore, Patent Document 1 describes that the moisture resistance of the obtained coating film can be improved by adding an additive to the coating material. However, the disclosed method blends the additive into the coating liquid. It is limited to the case where it is applied on the substrate.

  Patent Document 2 discloses an invention relating to fine cellulose fibers, which describes the possibility of being used as a coating material. However, it does not describe a use for which a specific effect has been shown, and a moisture-proofing agent is not used. There is no description about the method of adding.

  Non-Patent Document 1 does not disclose any gas barrier properties such as a water vapor barrier.

JP 2002-348522 A JP 2008-1728 A

Bio MACROMOLECULES Volume7, Number6, June 2006, Published by the American Chemical Society

  It is an object of the present invention to provide a gas barrier material capable of obtaining a film having excellent water vapor barrier properties and oxygen barrier properties, a gas barrier molded article using the same, and a method for producing the same. .

The present invention provides the following inventions as means for solving the problems.
(1) A step of forming a film-like material on a substrate or a base material using a suspension containing cellulose fibers,
Attaching a cross-linking agent aqueous solution having a reactive functional group to the film-like material;
Then, a method for producing a film-shaped molded article having a step of crosslinking reaction,
The method for producing a film-shaped molded article, wherein the cellulose fibers include those having an average fiber diameter of 200 nm or less, and the cellulose constituting the cellulose fibers has a carboxyl group content of 0.1 to 2 mmol / g.
(2) A step of forming a film-like material on a substrate or a base material using a suspension containing cellulose fibers,
Then, the step of drying,
A step of attaching an aqueous solution of a crosslinking agent having a reactive functional group to the dried film-like material,
Then, a method for producing a film-shaped molded article having a step of crosslinking reaction,
The method for producing a film-shaped molded article, wherein the cellulose fibers include those having an average fiber diameter of 200 nm or less, and the cellulose constituting the cellulose fibers has a carboxyl group content of 0.1 to 2 mmol / g.
(3) The manufacturing method of the film-shaped molded object of Claim 1 or 2 whose density | concentration of a crosslinking agent aqueous solution is 1-30 mass% in the process of attaching the said crosslinking agent aqueous solution.
(4) The method for producing a film-shaped molded article according to claim 1 or 2, wherein the crosslinking reaction is a step of heating at 30 to 300 ° C for 1 to 300 minutes.
(5) The crosslinking agent having the reactive functional group is an epoxy group, an aldehyde group, an amino group, a carboxyl group, an isocyanate group, a hydrazide group, an oxazoline group, a carbodiimide group, an azetidinium group, an alkoxide group, a methylol group, a silanol group, The method for producing a film-shaped molded article according to any one of claims 1 to 4, wherein the functional group is selected from a hydroxyl group, and the crosslinking agent is a compound containing two or more reactive functional groups.
(6) The method for producing a film-shaped molded article according to any one of claims 1 to 5, wherein the crosslinking agent having a reactive functional group has a molecular weight of 500 or less.
(7) The crosslinking agent having a reactive functional group has a molecular weight of 500 or less and is a compound containing two or more aldehyde groups, carboxyl groups, and hydrazide groups. The manufacturing method of the film-shaped molded object of description.
(8) The method for producing a film-shaped molded article according to any one of claims 1 to 7, wherein the crosslinking agent is selected from adipic acid dihydrazide, glyoxal, butanetetracarboxylic acid, glutaraldehyde, and citric acid. .

  The gas barrier referred to in the present invention refers to a shielding function against various gases such as oxygen, nitrogen, carbon dioxide, organic vapor, and water vapor, and aroma substances such as limonene and menthol. The film-shaped molded product according to the present invention is not limited to the purpose of improving the barrier property with respect to all the various gases in the previous period, but may be one that improves the barrier property only with respect to a specific gas. For example, a film-like molded article that has an improved oxygen barrier property but an improved water vapor barrier property is a gas barrier material that selectively inhibits the permeation of water vapor, and is included in the present invention. The gas for which the barrier property is improved is appropriately selected depending on the application.

  The present invention provides a gas barrier material as a material for a gas barrier molded article such as a film excellent in water vapor barrier property and / or oxygen barrier property in a humidity environment.

<Manufacture of specific cellulose fiber used as manufacturing raw material>
The cellulose fiber used in the present invention has an average fiber diameter of 200 nm or less, preferably 1 to 200 nm, more preferably 1 to 100 nm, and still more preferably 1 to 50 nm. An average fiber diameter is calculated | required by the measuring method as described in an Example.

  The carboxyl group content of cellulose constituting the cellulose fiber used in the present invention is 0.1 to 2 mmol / g, preferably 0.4 to 2 mmol / g, more preferably from the viewpoint of obtaining high gas barrier properties. Is 0.6 to 1.8 mmol / g, more preferably 0.6 to 1.6 mmol / g. Carboxyl group content is calculated | required by the measuring method as described in an Example. When the carboxyl group content is less than 0.1 mmol / g, the average fiber diameter of the cellulose fibers is not refined to 200 nm or less even when the fiber refinement process described below is performed.

  The cellulose fiber used in the present invention has a content of carboxyl group of cellulose constituting the cellulose fiber in the above range, but depending on the control state such as oxidation treatment in the actual production process, the cellulose fiber after oxidation treatment What exceeds the said range may be contained in it as an impurity.

  The cellulose fibers used in the present invention have an average aspect ratio of 10 to 1,000, more preferably 10 to 500, and still more preferably 100 to 350. An average aspect ratio is calculated | required by the measuring method as described in an Example.

  The cellulose fiber used by this invention can be manufactured by the following method, for example. First, about 10 to 1000 times the amount (mass basis) of water is added to the raw natural fiber (absolute dry basis), and processed with a mixer or the like to form a slurry.

  Examples of natural fibers that can be used as raw materials include wood pulp, non-wood pulp, cotton, and bacterial cellulose.

  Next, the natural fiber is oxidized using 2,2,6,6, -tetramethyl-1-piperidine-N-oxyl (TEMPO) as a catalyst. In addition, 4-acetamido-TEMPO, 4-carboxy-TEMPO, 4-phosphonooxy-TEMPO and the like, which are derivatives of TEMPO, can be used as the catalyst.

  The amount of TEMPO used is in a range of 0.1 to 10% by mass with respect to natural fibers (absolute dry standard) used as a raw material.

  During the oxidation treatment, an oxidant such as sodium hypochlorite and a bromide such as sodium bromide are used in combination with TEMPO as a co-oxidant.

  As the oxidizing agent, hypohalous acid or a salt thereof, hypohalous acid or a salt thereof, perhalogenic acid or a salt thereof, hydrogen peroxide, a perorganic acid, or the like can be used. Alkali metal hypohalites such as sodium bromite. The amount of the oxidizing agent used is in a range of about 1 to 100% by mass with respect to the natural fiber (absolute dry standard) used as a raw material.

  As a co-oxidant, it is preferable to use an alkali metal bromide such as sodium bromide. The usage-amount of a co-oxidant is the range used as about 1-30 mass% with respect to the natural fiber (absolute dry standard) used as a raw material.

  The pH of the slurry is desirably maintained in the range of 9 to 12 from the viewpoint of allowing the oxidation reaction to proceed efficiently.

  The temperature of the oxidation treatment (temperature of the slurry) is arbitrary at 1 to 50 ° C., but the reaction is possible at room temperature, and temperature control is not particularly required. The reaction time is preferably 1 to 240 minutes.

  After the oxidation treatment, the used catalyst or the like is removed by washing with water or the like. At this stage, since the reaction fiber is not refined, it can be performed by a purification method in which washing and filtration are repeated. If necessary, a dried or fibrous oxidized cellulose can be obtained.

  Thereafter, the oxidized cellulose is dispersed in a solvent such as water and refined. Refinement treatment is performed by a disaggregator, a beater, a low-pressure homogenizer, a high-pressure homogenizer, a grinder, a cutter mill, a ball mill, a jet mill, a short-axis extruder, a twin-screw extruder, an ultrasonic stirrer, and a domestic juicer mixer. And can be adjusted to length. The solid concentration in this step is preferably 50% by mass or less. Beyond that, it is not preferable because very high energy is required for dispersion.

  By such refinement treatment, cellulose fibers having an average fiber diameter of 200 nm or less can be obtained, and the average aspect ratio is 10 to 1,000, more preferably 10 to 500, and still more preferably 100 to 350. A certain cellulose fiber can be obtained.

  Thereafter, a solid (concentrated, transparent or opaque liquid) with a solid content adjusted as necessary, or a powder that is dried as necessary (however, it is a powder in which cellulose fibers are aggregated, Cellulose particles are not meant). In addition, when making into suspension, what used only water may be used, and the mixed solvent of water, other organic solvents (for example, alcohol, such as ethanol), surfactant, an acid, a base, etc. was used. It may be a thing.

  By such oxidation treatment and refinement treatment, the hydroxyl group at the C6 position of the cellulose structural unit is selectively oxidized to a carboxyl group via an aldehyde group, and the carboxyl group content is 0.1 to 2 mmol / g. Highly crystalline cellulose fibers that are made of cellulose and have an average fiber diameter of 200 nm or less can be obtained.

  This highly crystalline cellulose fiber has a cellulose I-type crystal structure. This means that the cellulose fiber is a fiber that is refined by surface oxidation of a naturally-derived cellulose solid raw material having an I-type crystal structure. In other words, natural cellulose fibers have a high-order solid structure built up by bundling fine fibers called microfibrils produced in the process of biosynthesis. The fine cellulose fiber is obtained by weakening the hydrogen bond) by introducing an aldehyde group or a carboxyl group, and further through a refinement treatment.

  Then, by adjusting the oxidation treatment conditions, the carboxyl group content is increased or decreased within a predetermined range, the polarity is changed, the electrostatic repulsion of the carboxyl group or the above-mentioned fine processing, The average fiber diameter, average fiber length, average aspect ratio, etc. can be controlled.

Cellulose fibers obtained by the above oxidation treatment and refinement treatment can satisfy the following requirements (I), (II), and (III).
(I): The mass fraction of cellulose fibers that can pass through a glass filter having an aperture of 16 μm is 5% or more with respect to the mass of cellulose fibers in the cellulose fiber suspension diluted to a solid content of 0.1 mass%. To obtain a gas barrier material with good performance.
(II): The cellulose fiber suspension diluted to a solid content of 1% by mass does not contain cellulose granules having a particle size of 1 μm or more.
(III): The light transmittance of the cellulose fiber suspension diluted to a solid content of 1% by mass is 0.5% or more.

  Requirement (I): When the suspension having a solid content of 0.1% by mass obtained by the above oxidation treatment and refinement treatment is passed through a glass filter having an aperture of 16 μm, the suspension before passing through the glass filter is suspended. A mass fraction of 5% or more with respect to the total amount of cellulose fibers contained in the suspension can pass through the glass filter (the mass fraction of fine cellulose fibers that can pass through the glass filter is defined as the content of fine cellulose fibers). To do). From the viewpoint of gas barrier properties, the fine cellulose fiber content is preferably 30% or more, more preferably 90% or more.

  Requirement (II): The suspension having a solid content of 1% by mass obtained by the above-described oxidation treatment and refinement treatment has a refined natural fiber used as a raw material, and is a cellulose granule having a particle diameter of 1 μm or more. What does not contain a body is preferable. Here, the granular material is substantially spherical, and the ratio of the major axis to the minor axis (major axis / minor axis) of the rectangle surrounding the projected shape obtained by projecting the shape onto a plane is 3 or less at the maximum. . The particle diameter of the granular material is an arithmetic average value of the lengths of the major axis and the minor axis. The presence / absence of the granular material was determined by observation with an optical microscope described later.

  Requirement (III): The cellulose fiber suspension having a solid content of 1% by mass obtained by the above oxidation treatment and refinement treatment preferably has a light transmittance of 0.5% or more, from the viewpoint of gas barrier properties. More preferably, it is 40% or more, and further preferably 60% or more.

  What is necessary is just to adjust solid content concentration so that the shaping | molding according to the objective can perform the cellulose fiber suspension of this invention, for example, solid content concentration can be made into the range of 0.05-30 mass%. Other components that may be contained in the cellulose fiber suspension include known fillers, colorants such as pigments, ultraviolet absorbers, antistatic agents, clay minerals (montmorillonite, etc.), metal salts, colloidal silica, Alumina sol, titanium oxide or the like can be blended.

<Process for forming a film-like material on a substrate or a substrate>
In this step, from the cellulose fiber obtained by the above method, a suspension containing it is prepared, or a suspension containing cellulose fiber is obtained by the above production method, and then the desired film-shaped molded body is formed. It is a process to make.

In this process, for example,
(I) using a suspension containing cellulose fibers to form a film on the substrate;
(Ii) using a suspension containing cellulose fibers to form a film on a substrate to obtain a composite film;
Either method can be applied.

[Forming method (i)]
A cellulose fiber suspension having a viscosity of about 10 to 5000 mPa · s is cast-applied on a substrate such as a hard surface such as glass or metal to form a film-like molded body. In this method, by controlling the carboxyl group amount and aspect ratio of the cellulose fiber contained in the cellulose fiber suspension and the thickness of the gas barrier molding, a film-like molding according to the specifications (high barrier properties, transparency, etc.) Can be obtained.

[Forming method (ii)]
A cellulose fiber suspension is attached to one or both surfaces of the substrate by a known method such as a coating method, spraying method, dipping method, or preferably by a coating method or a spraying method to form a film-shaped molded body. .

  Moreover, the method of bonding and laminating | stacking the film-form molded object which consists of a cellulose fiber suspension previously shape | molded with the shaping | molding method of (I) etc. with respect to a base material is applicable. As a bonding method, a known method such as a method using an adhesive or a heat-sealing method can be applied.

  The thickness of the layer made of cellulose fibers can be appropriately set depending on the application, but when used as a gas barrier material, it is preferably 20 to 900 nm, more preferably 50 to 700 nm, and still more preferably 100 to 500 nm.

  As the molded body serving as the base material, a thin film such as a film, a sheet, a woven fabric, and a non-woven fabric having a desired shape and size, and a three-dimensional container such as a box or bottle having various shapes and sizes can be used. These molded products may be made of paper, paperboard, plastic, metal (a material having a large number of holes or a wire mesh, which is mainly used as a reinforcing material), or a composite of these. Among them, it is preferable to use plant-derived materials such as paper and paperboard, biodegradable materials such as biodegradable plastics, or biomass-derived materials. The molded body serving as the base material can have a multilayer structure made of a combination of the same or different materials (for example, adhesiveness and wettability improver).

  The plastic used as the base material can be appropriately selected according to the application, but polyolefins such as polyethylene and polypropylene, polyamides such as nylon 6, 66, 6/10, and 6/12, polyethylene terephthalate (PET), and polybutylene. One or more selected from polyesters such as terephthalate, aliphatic polyester, polylactic acid (PLA), polycaprolactone, and polybutylene succinate, cellophane such as cellulose, and cellulose triacetate (TAC) can be used.

  The thickness of the molded body serving as the base material is not particularly limited, and may be appropriately selected so that strength according to the application can be obtained. For example, the thickness can be in the range of 1 to 1000 μm.

<Step of drying>
The film-like product formed in the previous step may be transferred to the step of attaching the aqueous crosslinking agent solution as it is, but a drying step may be added before that.

  A drying process is a process of drying a film-shaped molded object naturally or by ventilation drying at room temperature (about 20-25 degreeC), or heat-drying.

  The degree of drying is such that, for example, when the film-like product is formed by applying the molding method (I) described above, the film-like molded product can be peeled off from the substrate (in addition, the crosslinking reaction). Until the process is completed, it does not have to be peeled off from the substrate.) When the film-like material is formed by applying the molding method (II) described above, a light external force is applied (for example, finger In the case where the film-like molded body on the substrate is not wrinkled or torn.

<Step of attaching an aqueous solution of a crosslinking agent to an undried (wet state) or dried film-like material>
As a method of attaching an aqueous solution of a crosslinking agent having a reactive functional group to a film-like material,
(A) a method of spraying an aqueous solution of a crosslinking agent on the surface of a film-like material,
(B) A method of applying an aqueous crosslinking agent solution to the surface of the film-like material,
(C) A method of casting an aqueous crosslinking agent solution on the surface of a film-like material,
(D) A method of immersing the film-like material in the aqueous solution of the crosslinking agent together with the substrate or the substrate,
Etc. can be applied.

  In this step, after the cross-linking agent aqueous solution is attached to the film-like material, the cross-linking agent is allowed to permeate the inside of the film-like material, so that it can be left at room temperature for a while, and in a pressurized atmosphere as necessary Can be left unattended. In addition, when the aqueous solution of the crosslinking agent is applied to the undried film-like material, the crosslinking agent easily penetrates into the film-like material, and when the aqueous solution of the crosslinking agent is applied to the film-like material in the dry state, The cross-linking agent tends to stay on the surface of the film-like product or in the vicinity of the surface.

  When a method of forming a film-like material on a substrate using a cellulose fiber suspension to which a crosslinking agent has been added in advance, depending on the crosslinking agent (for example, butanetetracarboxylic acid), aggregation occurs, As a result of not being uniformly mixed in the film-forming raw material, the cross-linking reaction becomes non-uniform and a coating film can be formed, but the target film-shaped molded article may not be obtained. However, by applying the method of this step, it is possible to prevent the occurrence of the above problems regardless of the type and supply amount of the cross-linking agent, and it is possible to obtain a target film-shaped molded body.

When the method of (a) is applied, for example, when the area of the film-like material is 500 cm ² , 0.1 to 10 ml of the cross-linking agent aqueous solution having a concentration of 1 to 30% by mass is applied to the surface of the film-like material. Spraying methods can be applied.

  The oxidized cellulose fiber surface has a hydroxyl group, an aldehyde group, and a carboxyl group, and a crosslinked structure can be formed between the cellulose fibers by a crosslinking agent having a functional group capable of reacting with these.

  As the crosslinking agent used in this step, as a reactive functional group, epoxy group, aldehyde group, amino group, carboxyl group, isocyanate group, hydrazide group, oxazoline group, carbodiimide group, azetidinium group, alkoxide group, methylol group, silanol group A compound containing two or more functional groups of a hydroxyl group. The cross-linking agent may contain two or more of the same functional groups selected from the functional groups, or may contain two or more different functional groups selected from the functional groups. Those containing two or more are preferred. Examples of the crosslinking agent used in this step include polyamide epichlorohydrin resin (azetidinium group), polyacrylic acid (carboxyl group), polyisocyanate (isocyanate group) and the like.

  The crosslinking agent used in this step is preferably one having a low molecular weight because it can easily penetrate into a film-like material. For example, one having a molecular weight of 500 or less is preferable, and one having a molecular weight of 250 or less is more preferable. As the reactive functional group, a compound containing two or more aldehyde groups, carboxyl groups, and hydrazide groups is preferable.

  Preferred cross-linking agents include adipic acid dihydrazide (molecular weight 174), glyoxal (ethane dial) (molecular weight 58), butanetetracarboxylic acid (molecular weight 234), glutaraldehyde (1,5-pentane dial) (molecular weight 100), citric acid (Molecular weight 192). In addition, since a crosslinking agent having a carbodiimide group having a molecular weight of 500 or less significantly reduces oxygen barrier properties, it is not preferable as a crosslinking agent used in the present invention.

  After adhering the aqueous solution of the crosslinking agent, it is dried at room temperature (20 to 25 ° C.) for 2 hours or more to obtain a film-like molded product.

  The adhesion amount of the crosslinking agent in the film-shaped molded product is appropriately selected depending on the functional group amount of the cellulose fiber and the crosslinking agent and the permeability of the crosslinking agent into the film-like material, but with respect to the cellulose solid content per area. 0.1 to 200% by mass is preferable, and 10 to 100% by mass is more preferable. The adhesion amount of the cross-linking agent can be qualitatively and quantitatively analyzed from calorimetry, infrared absorption spectrum, etc., in addition to mass change after adhesion.

<Step of cross-linking reaction>
In this step, a cross-linking reaction is performed between the cellulose fibers by heating as necessary, but it is preferable to select the optimum heating conditions as appropriate according to the type and amount of the cross-linking agent used.

  For example, when a low molecular weight crosslinking agent such as adipic acid dihydrazide, glyoxal, butanetetracarboxylic acid, glutaraldehyde, citric acid is used, it is 30 to 300 ° C., more preferably 60 to 200 ° C., still more preferably 100 It can be heated at ˜160 ° C. for 1 to 300 minutes, more preferably 5 to 60 minutes.

  By forming a cross-linked structure with a cross-linking agent having a reactive functional group between cellulose fibers, a film-like molded body made of cellulose fibers can exhibit high gas barrier properties.

  Since the membrane-like molded product obtained by this production method is moisture-resistant (strength and barrier properties) by forming a crosslinked structure, in addition to the gas barrier material, a water purification separation membrane, an alcohol separation membrane, a polarized light It can also be used as a film, a polarizing plate protective film, a flexible transparent substrate for display, a fuel cell separator, a dew condensation prevention sheet, an antireflection sheet, an ultraviolet shielding sheet, an infrared shielding sheet, and the like.

  In the production method of the present invention, after the crosslinking reaction, if necessary, a moisture-proof layer can be further formed to further improve the moisture-proof property.

As a method of laminating the moisture-proof layer, a known method such as a method using an adhesive, a method of bonding by a thermal fusion method, a coating method, a spraying method, or a dipping method can be applied. Here, the base material and the moisture-proof layer having high moisture-proof performance are plastics such as polyolefin and polyester, those obtained by vapor-depositing inorganic oxides (aluminum oxide, silicon oxide, etc.), those laminated on paperboard, wax, For example, paper coated with wax can be used. The substrate or moisture-proof layer having high moisture-proof performance has a water vapor permeability of 0.1 to 600 g / m ² · day, preferably 0.1 to 300 g / m ² · day, more preferably 0.1 to 100 g / m. It is preferable to use ² · day. By forming the molded body having a base material or a moisture-proof layer having the above-mentioned high moisture-proof performance, the dissolution and diffusion of water vapor into the gas barrier layer can be suppressed, so that the gas barrier property can be further enhanced.

(1) Average fiber diameter and average aspect ratio of cellulose fiber The average fiber diameter of the cellulose fiber was measured by dropping an aqueous suspension diluted to 0.0001% by mass onto mica and drying it as an observation sample. The fiber height was measured with Nanoscope III Tapping mode AFM, manufactured by Digital instrument, and the probe used Point Probe (NCH) manufactured by Nano Sensors. In an image in which cellulose fibers can be confirmed, five or more were extracted, and the average fiber diameter was determined from the fiber height.

  The average aspect ratio was calculated from the viscosity of a diluted suspension (0.005 to 0.04% by mass) obtained by diluting cellulose fibers with water. The viscosity was measured at 20 ° C. using a rheometer (MCR300, DG42 (double cylinder), manufactured by PHYSICA). From the relationship between the mass concentration of the cellulose fiber and the specific viscosity of the cellulose fiber suspension with respect to water, the aspect ratio of the cellulose fiber was calculated by the following formula to obtain the average aspect ratio of the cellulose fiber.

(The theory of Polymer Dynamics, M.DOI and DFEDWARDS, CLARENDON PRESS / OXFORD, 1986, P312) The viscosity formula (8.138) of a rigid rod-like molecule was used (here, rigid rod-like molecule = cellulose fiber) ). (8.138) equation and _{^{Lb 2 × ρ 0 = M /}} N equation 1 from the relation of _a is derived. here, eta _sp is specific viscosity, [pi is circle ratio, ln is natural logarithm, P Is the aspect ratio (L / b), γ = 0.8, ρ _s is the density of the dispersion medium (kg / m ³ ), ρ ₀ is the density of cellulose crystals (kg / m ³ ), and C is the mass concentration of cellulose (C = ρ / ρ _s), L is the fiber length, b is the fiber width (cellulose fiber cross section is a square), [rho is the concentration of cellulose fibers (kg / m ^3), M is the molecular weight, the N _a represents Avogadro's number) .

(2) Carboxyl fiber carboxyl group content (mmol / g)
About 0.5 g of the dry weight of oxidized pulp is put in a 100 ml beaker, and ion exchange water is added to make a total of 55 ml. Then, 5 ml of 0.01 M sodium chloride aqueous solution is added to prepare a pulp suspension. Stir with a stirrer until dispersed. Then, after adding 0.1M hydrochloric acid to adjust the pH to 2.5-3.0, using an automatic titrator (AUT-501, manufactured by Toa DKK Co., Ltd.), 0.05M sodium hydroxide aqueous solution was injected under a waiting time of 60 seconds. Then, the electric conductivity and pH value of the pulp suspension every minute were measured, and the measurement was continued until the pH reached about 11. And the sodium hydroxide titration amount was calculated | required from the obtained electrical conductivity curve, and carboxyl group content was computed.

  Natural cellulose fibers exist as aggregates of highly crystalline microfibrils formed by collecting about 20 to 1500 cellulose molecules. In the TEMPO oxidation reaction employed in the present invention, a carboxyl group can be selectively introduced onto the surface of the crystalline microfibril. Therefore, in reality, carboxyl groups are introduced only on the crystal surface, but the carboxyl group content defined by the measurement method is an average value per cellulose weight.

(3) Light transmittance Using a spectrophotometer (UV-2550, manufactured by Shimadzu Corporation), the light transmittance (%) at a wavelength of 660 nm and an optical path length of 1 cm of a suspension having a concentration of 1% by mass was measured.

(4) Mass fraction of fine cellulose fibers in cellulose fiber suspension (fine cellulose fiber content) (%)
A cellulose fiber suspension was prepared to 0.1% by mass, and its solid content concentration was measured. Subsequently, the cellulose fiber suspension was subjected to suction filtration with a glass filter having a mesh size of 16 μm (25GP16, manufactured by SHIBATA), and then the solid content concentration of the filtrate was measured. The (C1 / C2) value obtained by dividing the solid content concentration (C1) of the filtrate by the solid content concentration (C2) of the suspension before filtration was calculated as the fine cellulose fiber content (%).

(5) Observation of suspension One drop of the suspension diluted to a solid content of 1% by mass was dropped on a slide glass, and a cover glass was placed on it to prepare an observation sample. Arbitrary five places of this observation sample were observed with an optical microscope (manufactured by ECLIPSE E600 POL NIKON) at a magnification of 400 times to confirm the presence or absence of cellulose granules having a particle diameter of 1 μm or more. The granular material is substantially spherical, and the ratio of the major axis to the minor axis (major axis / minor axis) of the rectangle surrounding the projected shape obtained by projecting the shape onto a plane is 3 or less at the maximum. The particle diameter of the granular material is an arithmetic average value of the lengths of the major axis and the minor axis. At this time, it can be confirmed more clearly by crossed Nicols observation.

(6) Water vapor permeability (g / m ² · day)
Based on JIS Z0208, the measurement was performed under conditions of an environment of 40 ° C. and 90% RH using a cup method.
(7) Oxygen permeability (isobaric method) (cm ³ / m ² · day · Pa)
Based on the measurement method of JIS K7126-2 appendix A, it measured on 23 degreeC and humidity 50% RH conditions using oxygen permeability measuring apparatus OX-TRAN2 / 21 (model ML & SL, MODERN CONTROL). Specifically, the measurement was performed in an environment of oxygen gas at 23 ° C. and humidity 50% RH and nitrogen gas (carrier gas) at 23 ° C. and humidity 50%. The oxygen permeability was measured by leaving the film-like molded body and leaving it in an environment of 23 ° C. and 50% RH for 24 hours or more.

Examples 1-3
(Preparation of cellulose fiber suspension)
(1) Raw material, catalyst, oxidizing agent, co-oxidizing agent Natural fiber: Bleached kraft pulp of conifers (Manufacturer: Fletcher Challenge Canada, trade name “Machenzie”, CSF 650 ml)
TEMPO: Commercial product (Manufacturer: ALDRICH, Free radical, 98%)
Sodium hypochlorite: Commercial product (Manufacturer: Wako Pure Chemical Industries, Ltd. Cl: 5%)
Sodium bromide: Commercial product (manufacturer: Wako Pure Chemical Industries, Ltd.).

(2) Production procedure First, 100 g of bleached kraft pulp fiber of the above-mentioned coniferous tree was sufficiently stirred with 9900 g of ion-exchanged water, and then TEMPO 1.25% by mass, sodium bromide 12.5% by mass, hypoxia with respect to 100 g of pulp mass. Sodium chlorate (28.4% by mass) was added in this order, and a pH stud was used to maintain the pH at 10.5 by dropwise addition of 0.5M sodium hydroxide to carry out an oxidation reaction.

  Next, dripping was stopped at an oxidation time of 120 minutes to obtain oxidized pulp. The oxidized pulp was sufficiently washed with ion exchange water and dehydrated. Thereafter, 3.9 g of oxidized pulp and 296.1 g of ion-exchanged water are stirred for 120 minutes with a mixer (Vita-Mix-Blender ABSOLUTE, manufactured by Osaka Chemical Co., Ltd.), so that the fiber is refined and suspended. A liquid was obtained. The solid content concentration in the obtained cellulose fiber suspension was 1.3% by mass. Cellulose fibers had an average fiber diameter of 3.1 nm, an average aspect ratio of 240, and a carboxyl group content of 1.2 mmol / g, and there were no cellulose granules having a particle diameter of 1 μm or more. The light transmittance of the cellulose fiber suspension was 97.1%, and the content of fine cellulose fibers was 90.9%.

[Membrane formation process]
Using the cellulose fiber suspension obtained in the previous step, obtained in the previous step on one side of a polyethylene terephthalate (PET) sheet (trade name: Lumirror, manufactured by Toray Industries, Inc., sheet thickness 25 μm) as a base sheet. The obtained cellulose fiber suspension was applied with a bar coater (# 50).

[Crosslinking agent aqueous solution adhesion process]
An aqueous solution of adipic acid dihydrazide having a concentration shown in Table 1 was sprayed on the film-like material obtained in the previous step by a commercially available spray. Spraying was performed so that about 0.06 g (dry weight) of the crosslinking agent was contained per 500 cm ^{2 of} the film-like product obtained in the previous step. In Examples 1 and 2, the cellulose fiber layer was in a wet state (within 3 minutes after application), and in Example 3, the aqueous crosslinking agent solution was sprayed after drying at room temperature (23 ° C.) for 120 minutes.

[Crosslinking process]
After adhering the aqueous crosslinking agent solution, it was dried at room temperature (23 ° C.) for 120 minutes. Thereafter, Examples 2 and 3 were heat-treated at 110 ° C. for 30 minutes in a thermostatic bath, and then radiated to obtain a film-like molded body. The film thickness of the obtained cellulose fiber layer was 800 nm. This is a value calculated from the wet film thickness and the solid content concentration of the cellulose fiber suspension with the specific gravity of the cellulose fiber being 1.5. This value was in good agreement with the film thickness measured with an atomic force microscope. Table 1 shows the measurement results of water vapor permeability.

Examples 4-6
In the same manner as in Examples 1 to 3, after the film-like product was formed, the glyoxal aqueous solution was attached and heated under the conditions shown in Table 1 to obtain a film-like molded body. Table 1 shows the measurement results of water vapor permeability.

Examples 7-9
In the same manner as in Examples 1 to 3, after the film-like product was formed, the butanetetracarboxylic acid aqueous solution was attached and heated under the conditions shown in Table 1 to obtain a film-like molded body. Table 1 shows the measurement results of water vapor permeability.

Examples 10-13
In the same manner as in Examples 1 and 2, after the film-like material was formed, the cellulose fiber layer was kept in a wet state (within 3 minutes), and the aqueous solution of the crosslinking agent was attached and heated under the conditions shown in Table 1 to form a film-like material. A molded body was obtained. Table 1 shows the measurement results of the water vapor permeability of the obtained film-shaped molded product.

Comparative Example 1
Table 2 shows the measurement results of the water vapor permeability of the PET sheet (film thickness: 25 μm) used as the substrate.

Comparative Example 2
Table 2 shows the measurement results of the water vapor permeability of the film-shaped molded body that was dried at room temperature (23 ° C.) for 120 minutes without forming the aqueous solution of the crosslinking agent after forming the film-like material in the same manner as in Example 1. .

Comparative Example 3
100 g of the cellulose fiber suspension obtained in the same manner as in Example 1 was collected, and 1.3 g of a BTC aqueous solution diluted to 5% by mass as a crosslinking agent (the BTC amount with respect to 100 parts by mass of cellulose fiber solids was 5). Part by mass) and well stirred. Although it apply | coated to the PET sheet similarly to Example 1, it produced aggregation and the uniform application | coating surface was not made.

CSNF: Cellulose fiber produced in the example
ADH: adipic acid dihydrazide, manufactured by Otsuka Chemical Co., Ltd. (molecular weight 174)
Gly: Glyoxal, Wako Pure Chemical Industries, Ltd. (molecular weight 58)
BTC: Butanetetracarboxylic acid, manufactured by Wako Pure Chemical Industries, Ltd. (molecular weight 234)
APA-P280: Acrylamide-acrylic acid hydrazide copolymer, manufactured by Otsuka Chemical Co., Ltd. (molecular weight about 20,000, see manufacturer catalog)
PAE: Product name WS4030, polyamide epichlorohydrin resin, manufactured by Seiko PMC Co., Ltd. (molecular weight hundreds of thousands)
As shown in Tables 1 and 2, in Examples 1 to 11 to which an aqueous solution of a crosslinking agent was attached, the water vapor barrier property was improved as compared with Comparative Examples 1 to 3. This indicates that a crosslinked structure is formed while the adhered crosslinking agent penetrates between fine cellulose fibers. Particularly in Examples 1 to 9 where a low molecular weight crosslinking agent was applied, the water vapor permeability was less than 20 g / m ² · day. The application of the low molecular weight cross-linking agent is better from the viewpoint of water vapor barrier property compared with Examples 10 to 11 to which a resin type cross-linking agent aqueous solution is adhered. The permeability to fine cellulose fibers is higher than that of the high molecular weight cross-linking agent. This is considered to be because it is high and a crosslinked structure is easily formed.

  Examples 3, 6, and 9 are film-shaped molded articles in which an aqueous solution of a crosslinking agent is adhered after drying the applied cellulose suspension. As is clear from Table 1, in Examples 3, 6, and 9, the improvement of the water vapor barrier property was confirmed. Since the adhered cross-linking agent is an aqueous solution, the cellulose fiber layer after drying is swollen by water, indicating that the cross-linking agent component has permeated.

  Examples 1 to 9 clearly show higher water vapor barrier properties than Comparative Example 3 obtained by applying a cellulose fiber suspension to which a crosslinking agent has been added in advance to a substrate. In particular, in Comparative Example 3, the cellulose fiber suspension aggregates and a uniform coating surface cannot be applied. Thus, even if it is preferable in terms of cross-linking reactivity, a kind and an added amount of a cross-linking agent that cannot maintain the fluidity that can be applied when added to the cellulose suspension are supplied to the film-shaped molded body. be able to. Also from this, it can be seen that the production process in which a cross-linking agent is adhered after forming a film-like molded body from a cellulose fiber suspension is suitable as a production method for a film having a water vapor barrier property.

Example 14
As a cross-linking step, a film-like molded body was obtained in the same manner as in Example 4 except that heat treatment was performed at 150 ° C. for 30 minutes in a thermostatic bath. Table 3 shows the measurement results of water vapor permeability and oxygen permeability.

Example 15
A film-like molded body was obtained in the same manner as in Example 14 except that glutaraldehyde (manufactured by Wako Pure Chemical Industries, Ltd.) was used as a crosslinking agent. The measurement results of water vapor permeability and oxygen permeability are shown in Table 3.

Example 16
A film-like molded body was obtained in the same manner as in Example 14 except that ADH (adipic acid dihydrazide, manufactured by Otsuka Chemical Co., Ltd.) was used as a crosslinking agent. The measurement results of water vapor permeability and oxygen permeability are shown in Table 3.

Example 17
A film-like molded body was obtained in the same manner as in Example 14 except that BTC (butanetetracarboxylic acid, manufactured by Wako Pure Chemical Industries, Ltd.) was used as a crosslinking agent. The measurement results of water vapor permeability and oxygen permeability are shown in Table 3.

Example 18
A film-like molded body was obtained in the same manner as in Example 14 except that citric acid (manufactured by Wako Pure Chemical Industries, Ltd.) was used as a crosslinking agent. The measurement results of water vapor permeability and oxygen permeability are shown in Table 3.

Example 19
A film-like molded body was obtained in the same manner as in Example 14 except that APA-P280 (acrylamide-acrylic acid hydrazide copolymer, manufactured by Otsuka Chemical Co., Ltd.) was used as a crosslinking agent. The measurement results of water vapor permeability and oxygen permeability are shown in Table 3.

Example 20
A film-like molded body was obtained in the same manner as in Example 14 except that E-02 (polycarbodiimide, manufactured by Nisshinbo Co., Ltd.) was used as a crosslinking agent. The measurement results of water vapor permeability and oxygen permeability are shown in Table 3.

実施例１４〜２０は、反応性架橋剤を付着させていない比較例２に比べて、酸素バリア性、水蒸気バリア性が向上している。特に架橋剤が低分子量である実施例１４〜１８において高いバリア性の向上効果が見られた。水蒸気バリア性に関しては、反応性架橋剤の官能基がカルボキシル基である実施例１７、１８及びアルデヒド基である実施例１４において大幅な向上が見られた。酸素バリア性に関しては、反応性架橋剤の官能基がカルボキシル基である実施例１７、１８及びアルデヒド基である実施例１４、ヒドラジド基である実施例１６において大幅な向上が見られた。

In Examples 14 to 20, oxygen barrier properties and water vapor barrier properties are improved as compared with Comparative Example 2 in which no reactive crosslinking agent is attached. In particular, in Examples 14 to 18 in which the crosslinking agent has a low molecular weight, a high barrier property improving effect was observed. With respect to water vapor barrier properties, significant improvements were observed in Examples 17 and 18 where the functional group of the reactive cross-linking agent was a carboxyl group and Example 14 where the functional group was an aldehyde group. Regarding oxygen barrier properties, significant improvements were observed in Examples 17 and 18 in which the functional group of the reactive crosslinking agent is a carboxyl group, Example 14 in which the functional group is an aldehyde group, and Example 16 in which the functional group is a hydrazide group.

Claims (8)

A step of forming a film-like material on a substrate or a base material using a suspension containing cellulose fibers;
Attaching a cross-linking agent aqueous solution having a reactive functional group to the film-like material;
Then, a method for producing a film-shaped molded article having a step of crosslinking reaction,
The method for producing a film-shaped molded article, wherein the cellulose fiber has an average fiber diameter of 200 nm or less , and the cellulose constituting the cellulose fiber has a carboxyl group content of 0.1 to 2 mmol / g. A step of forming a film-like material on a substrate or a base material using a suspension containing cellulose fibers;
Then, the step of drying,
A step of attaching an aqueous solution of a crosslinking agent having a reactive functional group to the dried film-like material,
Then, a method for producing a film-shaped molded article having a step of crosslinking reaction,
The method for producing a film-shaped molded article, wherein the cellulose fiber has an average fiber diameter of 200 nm or less , and the cellulose constituting the cellulose fiber has a carboxyl group content of 0.1 to 2 mmol / g.   The manufacturing method of the film-shaped molded object of Claim 1 or 2 whose density | concentration of a crosslinking agent aqueous solution is 1-30 mass% in the process to which the said crosslinking agent aqueous solution is made to adhere.   The method for producing a film-shaped molded article according to claim 1 or 2, wherein the crosslinking reaction is a step of heating at 30 to 300 ° C for 1 to 300 minutes.   The crosslinking agent having a reactive functional group is selected from an epoxy group, an aldehyde group, an amino group, a carboxyl group, an isocyanate group, a hydrazide group, an oxazoline group, a carbodiimide group, an azetidinium group, an alkoxide group, a methylol group, a silanol group, and a hydroxyl group. The method for producing a film-shaped molded article according to any one of claims 1 to 4, wherein the crosslinking agent is a compound containing two or more reactive functional groups.   The method for producing a film-shaped molded article according to any one of claims 1 to 5, wherein the crosslinking agent having a reactive functional group has a molecular weight of 500 or less.   The film according to any one of claims 1 to 6, wherein the crosslinking agent having a reactive functional group is a compound having a molecular weight of 500 or less and containing two or more aldehyde groups, carboxyl groups, and hydrazide groups. A method for producing a shaped molded body.   The method for producing a film-shaped molded article according to any one of claims 1 to 6, wherein the crosslinking agent is selected from adipic acid dihydrazide, glyoxal, butanetetracarboxylic acid, glutaraldehyde, and citric acid.