JP2010201414A - Method of manufacturing filmy molded article - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a filmy molded article which is suitable as an oxygen-barrier film having a high oxygen-barrier property even in a high humidity atmosphere, and to provide a filmy molded article. <P>SOLUTION: The method of manufacturing the filmy molded article includes a process of forming a film of suspension containing cellulose fibers and a process of drying the article by heating subsequently. The cellulose fibers contain fibers of an average fiber diameter ≤200 nm, wherein cellulose that composes the cellulose fibers has a carboxyl group content of 0.1-2 mmol/g. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for producing a film-like molded article suitable as a method for producing a film having a gas barrier property capable of suppressing permeation of various gases such as oxygen, water vapor, carbon dioxide, and nitrogen, and a film obtained by the method. Relates to a molded article.

  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. In the examples, only those having an average particle size of 3 μm and 100 μm are used. There is no description about the refinement 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.

  Further, Patent Document 1 describes that the moisture resistance of the obtained coating film can be improved by adding an additive to the coating material.

  Patent Document 2 discloses an invention related to fine cellulose fibers, and describes the possibility of being used as a coating material, but does not describe the use for which a specific effect has been shown, and describes moisture resistance. Nor.

Non-Patent Document 1 does not disclose any gas barrier properties such as an oxygen barrier.
JP 2002-348522 A JP 2008-1728 A Bio MACROMOLECULES Volume7, Number6, June 2006, Published by the American Chemical Society

  The present invention provides a method for producing a molded body capable of obtaining a film-shaped molded body suitable as an oxygen barrier film having a high oxygen barrier property even in a high humidity atmosphere, and a film-shaped molded body obtained by the method. This is the issue.

The present invention provides the following inventions as means for solving the problems.
(1) A method for producing a film-shaped formed body having a step of forming a film-like product of a suspension containing cellulose fibers, and then a drying step by heating,
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) The manufacturing method according to claim 1, wherein in the drying step by heating, the moisture content of the film-shaped molded body is dried to 1 to 90% of the equilibrium moisture content at 23 ° C. and 60% RH.
(3) The manufacturing method of the film-shaped molded object of Claim 1 or 2 whose heating temperature is 50-250 degreeC in the drying process by the said heating.
(4) Between the step of forming a film of the suspension containing the cellulose fibers and the drying step by heating, the water content of the film is 20 ° C. ± 15 ° C. and the humidity is 45 to 85% RH. The manufacturing method of the film-shaped molded object of any one of Claims 1-3 which has the process hold | maintained in the state dried to the equilibrium moisture content of.

  The film-like molded body obtained by the production method of the present invention can be used as an oxygen barrier film having a high oxygen barrier property even in a high humidity atmosphere.

<Manufacture of specific cellulose fiber used as manufacturing raw material>
The cellulose fibers used in the present invention include those having 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.

  When a film-like molded product is obtained by applying the production method of the present invention, it is preferable that the carboxyl group content is larger within the above range because the oxygen barrier property can be increased. From the viewpoint of enhancing the oxygen barrier property, the carboxyl group content is preferably 1.0 mmol / g or more, more preferably 1.4 mmol / g or more within the above range.

  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, still more preferably 100 to 350, and still more preferably 100 to 235. 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, dry-treated fibrous or powdered oxidized cellulose fibers 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, still more preferably 100 to 350, and still more preferably. Can obtain cellulose fibers of 100-235. When the production method of the present invention is applied, a smaller aspect ratio, that is, a shorter average fiber length is preferable because the oxygen barrier property can be increased. From the viewpoint of enhancing the oxygen barrier property, when the average fiber diameter is in the range of the average aspect ratio, the average aspect ratio is preferably 350 or less, and more preferably 235 or less.

  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. In the oxidation reaction, unreacted hydroxyl groups and aldehyde groups remain. The residual amount of aldehyde groups is 0.1 to 0.6 mmol / g when the carboxyl group content is 0.1 to 2 mmol / g.

  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.

  And by adjusting the oxidation treatment conditions, the carboxyl group content is increased or decreased within a predetermined range, the polarity is changed, or the carboxyl group is subjected to electrostatic repulsion or the above-described refinement treatment. The average fiber diameter, average fiber length, average aspect ratio and the like of the cellulose fiber 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 cellulose fibers 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.

  And the film-like molded object containing the cellulose fiber obtained by said oxidation process and refinement | miniaturization process produces the hydrogen bond between fine cellulose fibers, and a strong cross-linking interaction, suppresses melt | dissolution and diffusion of gas, and is high It is considered that gas barrier properties such as oxygen barrier properties can be expressed. In addition, since the pore size and pore distribution between the molded cellulose fibers can be changed depending on the width and length of the cellulose fibers (that is, the molecular sieve effect can be changed), a molecular selective barrier. We can expect sex.

  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.

<Step of forming a film-like material>
This step is a step of preparing a suspension containing the cellulose fiber obtained by the above method and forming a film-like product (wet and fluid) of the suspension containing the cellulose fiber.

In this process, for example,
(I) using a suspension containing cellulose fibers to form a film on the substrate; and
(Ii) forming a film-like material on a substrate such as a resin film using a suspension containing cellulose fibers;
Either method can be applied.

[Forming method (i)]
A cellulose fiber suspension having a viscosity of about 10 to 5000 mPa · s is cast-coated on a substrate such as a glass plate to produce a film-like material. When this method is applied, a film-like molded body can be obtained by heating and drying later and then peeling off from the substrate. By controlling the carboxyl group amount and aspect ratio of the cellulose fiber contained in the cellulose fiber suspension to be used and the thickness of the film-shaped molded body, a film-shaped molded body corresponding to the specifications (high barrier property, transparency, etc.) is obtained. be able to.

[Forming method (ii)]
A cellulose fiber suspension is adhered to one or both surfaces of a substrate such as a resin film by a known method such as a coating method, a spraying method, or a dipping method, preferably by a coating method or a spraying method. To form a film. When this method is applied, a composite molded body in which a film-shaped molded body is laminated on a substrate after heating and drying is obtained.

  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, polybutylene succinate, cellophane such as cellulose, cellulose triacetate (TAC), and the like 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.

<Drying process by heating>
The drying step by heating is a step of drying while heating after forming a film of the cellulose fiber suspension on a substrate or base material. When the membrane of cellulose fiber suspension is wet and fluid, it may be dried while heating, or once dried, the membrane of suspension is lost until it loses fluidity. You may dry, heating after obtaining a molded object.

  Specifically, the loss of fluidity of the film-like material means that when the molding method (I) is applied, the film-like molded product can be peeled off from the substrate (II ), The film-like molded product on the substrate is not wrinkled or torn when a light external force is applied (for example, when pinched with a finger). More specifically, the membrane is dried to an equilibrium moisture content at a temperature of 20 ° C. ± 15 ° C. and a humidity of 45 to 85% RH. Once the film-shaped molded body is held at the equilibrium water content in the temperature and humidity ranges, it becomes easier to store as an intermediate product and process according to the purpose such as printing or protective layer lamination. preferable.

  In order to obtain a good gas barrier property for the film-shaped molded body, the moisture content of the film-shaped molded body is higher than the equilibrium moisture content at a temperature of 23 ° C. and a relative humidity of 60% RH in the drying step by heating. It is preferable to dry to 90% or less, more preferably to 75% or less, more preferably to 50% or less, further preferably to 10% or less. The lower limit of the moisture content of the film-shaped molded body in the drying step by heating is 1% or more of the equilibrium moisture content, more preferably 2% or more, and even more preferably 5% or more. Equilibrium moisture content at a temperature of 23 ° C. and a relative humidity of 60% RH is measured after the film-like molded body after drying by heating is stored in an environment of 23 ° C. and 60% RH until the equilibrium moisture content is reached. It is the value. The moisture content and the equilibrium moisture content of the film-like molded product are obtained by the method described in the examples.

  50-250 degreeC is preferable, as for the upper limit of the temperature of the drying process by heating, 100-160 degreeC is more preferable, and 120-160 degreeC is still more preferable. When the temperature is 50 ° C. or higher, the time required to reach the target moisture content can be shortened, and when the temperature is 250 ° C. or lower, the film-like molded body of cellulose fibers and the substrate are damaged by heat. Occurrence can be suppressed. The drying time, the pressure in the drying furnace, the convection conditions, and the like can be appropriately adjusted so as to reach the target moisture content.

  As an apparatus for drying while heating, a known method can be used, such as an electric drying furnace (natural convection type or forced convection type), a hot air circulation type drying furnace, a drying furnace using both heating by far infrared rays and hot air circulation. And a vacuum drying furnace capable of reducing pressure while heating.

  When drying by heating, cooling to room temperature and applying the molding method (I), it can be peeled off from the substrate to obtain a film-like molded product, and when the molding method (II) is applied Can obtain a composite molded body having a laminated structure of a substrate and a film-shaped molded body (cellulose fiber layer). At this time, the moisture content of the film-shaped molded product returns to the parallel moisture content under the temperature and humidity conditions, but in the drying process by heating, the moisture content is higher than the equilibrium moisture content at a temperature of 23 ° C. and a relative humidity of 60% RH. Good gas barrier properties can be obtained by drying to a small extent. In the drying process by heating, chemical or physical changes occur in the structure of the film-shaped molded product (structure of the cellulose fiber layer), resulting in a dense structure, which is maintained even when there is a change in temperature and humidity. It is thought to be done.

  The moisture content in the cellulose fiber layer can be qualitatively and quantitatively analyzed from calorimetry, infrared absorption spectrum, etc., as well as weight changes before and after heating and drying.

  In the production method of the present invention, 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 making the composite molded body having a substrate and a moisture-proof layer having the above-mentioned high moisture-proof performance, it is possible to suppress the dissolution and diffusion of water vapor into the cellulose fiber layer, thereby further improving the oxygen barrier property under high humidity conditions. Can be increased.

  The measurement method for each item is as follows.

(1) Cellulose fiber (1-1) Average fiber diameter, average aspect ratio The average fiber diameter of the cellulose fiber was measured by adding a suspension diluted to 0.001% by mass onto mica and drying it as an observation sample. The fiber height was measured with an atomic force microscope (Nanoscope III Tapping mode AFM, manufactured by Digital instrument, using a probe made by Nano Sensors, Point Probe (NCH)). 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) .

(1-2) 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, 0.1M hydrochloric acid is added to adjust the pH to 2.5 to 3.0, and then 0.05M sodium hydroxide aqueous solution is injected under the condition of a waiting time of 60 seconds using an automatic titrator (AUT-501, manufactured by Toa DK Corporation). Then, the electric conductivity and the pH value of the pulp suspension every minute were measured, and the measurement was continued until the pH became about pH11. 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.

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

(3) 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 (%).

(4) 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.

(5) Moisture content (%) of membrane-shaped molded product (cellulose fiber layer)
First, the weight of the film-shaped molded body is measured (this weight is a). Next, the weight of the film-shaped molded body after drying under reduced pressure at 105 ° C. and 360 mmHg for 24 hours is measured (this weight is defined as the absolute dry weight b). The water content was calculated as a percentage (%) of the amount of water in the film-shaped molded body (weight a minus b) with respect to the weight (a) of the film-shaped molded body ((ab) / ax). 100). In addition, the moisture content after the drying process by heating is a moisture content 3 minutes after taking out from a heating-drying furnace.

(6) Equilibrium water content (%) of membrane-like molded product (cellulose fiber layer)
This is a value obtained by measuring the moisture content of the film-shaped molded body after storing the film-shaped molded body after the drying step by heating in an environment of 23 ° C. and 60% RH for 24 hours or more.

(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%. Further, some examples and comparative examples were measured under conditions of 23 ° C. and humidity 0% RH. Specifically, the measurement was performed in an environment of oxygen gas at 23 ° C. and humidity 0% RH and nitrogen gas (carrier gas) at 23 ° C. and humidity 0%. Further, some examples and comparative examples were measured under conditions of 23 ° C. and humidity 70% RH. Specifically, the measurement was performed in an environment of oxygen gas at 23 ° C. and humidity 70% RH and nitrogen gas (carrier gas) at 23 ° C. and humidity 70%.

  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.

Example 1
(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.), thereby performing fiber refinement treatment and suspension. A liquid was obtained. 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%.

  To 100 g of the cellulose fiber suspension, 30 g of ion-exchanged water and 39 g of isopropanol were added and stirred well. The solid content concentration of the obtained cellulose fiber suspension was 0.77%.

(Formation of film-like material)
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 cellulosic fiber suspension produced by the above method is applied to a bar coater (# 50). It was applied with.

[Drying process by heating]
Next, it was dried at room temperature (23 ° C.) for 120 minutes. Furthermore, it was heated and dried at 110 ° C. for 30 minutes in an electric drying furnace (natural convection type) to obtain a composite molded body having a laminated structure. Table 1 shows the measurement results of the moisture content, the equilibrium moisture content at 23 ° C. and 60% RH, and the oxygen permeability before and after the drying step treatment by heating.

  In addition, the thickness of the cellulose fiber layer in Table 1 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.

Examples 2-4
Using the same cellulose fiber suspension as in Example 1, on one side of a polyethylene terephthalate (PET) sheet (trade name: Lumirror, manufactured by Toray Industries, Inc., sheet thickness 25 μm) as a substrate sheet, the cellulose fiber suspension The liquid was applied with a bar coater (# 50).

  Next, it was dried at room temperature (23 ° C.) for 120 minutes in the same manner as in Example 1. Furthermore, it heat-dried at the temperature and time which are shown in Table 1 with an electric drying furnace (natural convection type), and obtained the composite molded object which has a laminated structure. Table 1 shows the measurement results of the moisture content of the cellulose fiber layer before and after the drying step by heating, the equilibrium moisture content at 23 ° C. and 60% RH, and the oxygen permeability.

Examples 5 and 6
Using the same cellulose fiber suspension as in Example 1, on one side of a polyethylene terephthalate (PET) sheet (trade name: Lumirror, manufactured by Toray Industries, Inc., sheet thickness 25 μm) as a substrate sheet, the cellulose fiber suspension The liquid was applied with a bar coater (# 50).

  Next, while the film of cellulose fiber suspension is in a wet and fluid state (within 5 minutes after application), heat treatment is carried out at the temperature and time shown in Table 1 in an electric drying oven (natural convection type). A composite molded body having a laminated structure was obtained. Table 1 shows the measurement results of the moisture content of the cellulose fiber layer before and after the drying step by heating, the equilibrium moisture content at 23 ° C. and 60% RH, and the oxygen permeability.

Comparative Example 1
Using the same cellulose fiber suspension as in Example 1, on one side of a polyethylene terephthalate (PET) sheet (trade name: Lumirror, manufactured by Toray Industries, Inc., sheet thickness 25 μm) as a substrate sheet, the cellulose fiber suspension The liquid was applied with a bar coater (# 50).

  Next, after drying at room temperature (23 ° C.) for 120 minutes in the same manner as in Example 1, a composite molded body having a laminated structure was obtained without drying by heating. Table 1 shows the measurement results of the moisture content of the cellulose fiber layer after drying at room temperature for 120 minutes, the equilibrium moisture content at 23 ° C. and 60% RH, and the oxygen permeability.

Comparative Examples 2 and 3
Carboxymethylcellulose sodium salt (CMC) (trade name HE1500F, manufactured by Daicel Industries, Ltd.) 10 g was added 90 g of ion-exchanged water and 30 g of isopropanol to prepare a 0.7 mass% CMC solution.

  Next, a 0.7% by mass CMC solution was applied 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 in the same manner as in Example 1. The cellulose fiber suspension was applied with a bar coater (# 50).

  Thereafter, in Comparative Example 2, after drying at room temperature (23 ° C.) for 120 minutes, a composite molded body having a laminated structure was obtained without performing drying by heating. Table 1 shows the measurement results of oxygen permeability.

  In Comparative Example 3, the composite molded body obtained in Comparative Example 2 was heat-dried at 110 ° C. for 30 minutes in an electric drying furnace (natural convection type) to obtain a composite molded body having a laminated structure. Table 1 shows the measurement results of oxygen permeability.

Comparative Example 4
Table 1 shows the measurement results of oxygen permeability of a polyethylene terephthalate (PET) sheet (trade name: Lumirror, manufactured by Toray Industries, Inc., sheet thickness: 25 μm).

  As is clear from Examples 1 to 6 and Comparative Examples 1 and 4, the film-like molded body obtained by the production method of the present invention is better than the case where the drying by heating is not performed (Comparative Example 1). In particular, the oxygen barrier property under the measurement condition of 50% RH is good. It became clear that the oxygen barrier property was maintained even in a high humidity environment by drying by heating. Further, Example 2 and Example 5 which were heat-dried to 50% or less of the equilibrium water content at 23 ° C. and 60% RH exhibited higher oxygen barrier properties under the measurement conditions of 50% RH. In Example 2, which was heat-dried to 10% or less of the equilibrium water content at 23 ° C. and 60% RH, higher oxygen barrier properties were obtained under the measurement conditions of 0% RH and 50% RH.

  Between the step of forming a film of the suspension containing the cellulose fiber and the drying step by heating, the step of holding the moisture content of the membrane in a dry state up to the equilibrium moisture content at normal temperature and humidity Example 1 and Example 2 possessed are the oxygen equivalent to Example 5 and Example 6 in which there is no step of maintaining the moisture content of the film-like material in a dry state until the equilibrium moisture content at normal temperature and humidity. Barrier properties are obtained. By the process of keeping the moisture content at room temperature and humidity in a dry state, it is possible to carry out processing according to purposes such as storage as an intermediate product, printing or lamination of a protective layer.

  Comparative Example 2 and Comparative Example 3 are film-like molded bodies prepared from CMCNa aqueous solutions of similar structural substances having a carboxyl group in the cellulose molecule. In these two examples, it was not possible to confirm an improvement in oxygen barrier properties at 50% RH by heating, so in the method for producing a film-shaped molded body of the present invention, the expression of oxygen barrier properties under high humidity by heating was It is thought that it originates from the structural characteristics of the used cellulose fiber. For example, the cellulose fiber used in the present invention maintains a dense structure even in a humidity environment of 50% RH by bonding, that is, crosslinking, the aldehyde group contained on the surface with the hydroxyl group of the cellulose fiber by heating. There is a possibility.

Example 7
First, 100 g of bleached kraft pulp fiber of conifers was sufficiently stirred with 9900 g of ion-exchanged water, and then TEMPO 1.25% by mass, sodium bromide 12.5% by mass, sodium hypochlorite 28.4% by mass with respect to 100 g of pulp % Were added in this order, and a pH stud was used to maintain the pH at 10.5 by dropwise addition of 0.5 M 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 10 minutes with a mixer (Vita-Mix-Blender ABSOLUTE, manufactured by Osaka Chemical Co., Ltd.), so that the fiber is refined. A suspension was obtained. Cellulose fibers had an average fiber diameter of 3.3 nm, an average aspect ratio of 305, 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 95.5%, and the content of fine cellulose fibers was 100%. The solid content concentration of the obtained cellulose fiber suspension was 1.3%.

  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 cellulosic fiber suspension produced by the above method is applied to a bar coater (# 50). It was applied with.

  Next, it was dried at room temperature (23 ° C.) for 120 minutes. Furthermore, it was heated and dried at 110 ° C. for 30 minutes in an electric drying furnace (natural convection type) to obtain a composite molded body having a laminated structure. Table 2 shows the measurement results of the moisture content of the cellulose fiber layer before and after the drying step by heating, the equilibrium moisture content at 23 ° C. and 60% RH, and the oxygen permeability.

  The thickness of the cellulose fiber layer in Table 2 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.

Example 8
A cellulose fiber suspension was prepared in the same manner as in Example 7 except that the amount of sodium hypochlorite added was 7.1% by mass, and a composite molded body was obtained in the same manner as in Example 7. Table 2 shows the measurement results of the moisture content of the cellulose fiber layer before and after the drying step by heating, the equilibrium moisture content at 23 ° C. and 60% RH, and the oxygen permeability.

Example 9
A cellulose fiber suspension was prepared in the same manner as in Example 7 except that the amount of sodium hypochlorite added was 14.2% by mass, and a composite molded body was obtained in the same manner as in Example 7. Table 2 shows the measurement results of the moisture content of the cellulose fiber layer before and after the drying treatment by heating, the equilibrium moisture content at 23 ° C. and 60% RH, and the oxygen permeability.

Example 10
A cellulose fiber suspension was prepared in the same manner as in Example 7 except that the amount of sodium hypochlorite added was 56.4% by mass, and a composite molded body was obtained in the same manner as in Example 7. Table 2 shows the measurement results of the moisture content of the cellulose fiber layer before and after the drying step by heating, the equilibrium moisture content at 23 ° C. and 60% RH, and the oxygen permeability.

  Examples 7 to 10 are film-shaped molded articles prepared from cellulose fiber suspensions having different fiber diameters and carboxyl group contents. It can be seen that even if the carboxyl group content and the average aspect ratio of cellulose constituting the cellulose fiber are different, the production method of the present invention can provide a high oxygen barrier property.

Example 11
A cellulose fiber suspension was prepared in the same manner as in Example 10.

  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 cellulosic fiber suspension produced by the above method is applied to a bar coater (# 50). It was applied with.

  Next, it was dried at room temperature (23 ° C.) for 120 minutes. Furthermore, it was heated and dried at 150 ° C. for 30 minutes in an electric drying furnace (natural convection type) to obtain a composite molded body having a laminated structure. Table 3 shows the measurement results of oxygen permeability.

  In addition, the thickness of the cellulose fiber layer in Table 3 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.

Example 12
A composite molded body was obtained in the same manner as in Example 11 except that heat drying was performed at 150 ° C. for 60 minutes in an electric drying furnace (natural convection type). Table 3 shows the measurement results of oxygen permeability.

Example 13
A composite molded body was obtained in the same manner as in Example 11 except that heat drying was performed at 150 ° C. for 180 minutes in an electric drying furnace (natural convection type). Table 3 shows the measurement results of oxygen permeability.

Example 14
A cellulose fiber suspension was prepared in the same manner as in Example 7 except that stirring was performed for 120 minutes with a mixer (Vita-Mix-Blender ABSOLUTE, Osaka Chemical Co., Ltd.). A molded body was obtained. Table 3 shows the measurement results of oxygen permeability.

Example 15
A cellulose fiber suspension was prepared in the same manner as in Example 11 except that the mixture was stirred for 120 minutes with a mixer (Vita-Mix-Blender ABSOLUTE, Osaka Chemical Co., Ltd.). A molded body was obtained. Table 3 shows the measurement results of oxygen permeability.

Example 16
A cellulose fiber suspension was prepared in the same manner as in Example 9 except that stirring was performed for 120 minutes with a mixer (Vita-Mix-Blender ABSOLUTE, manufactured by Osaka Chemical Co., Ltd.). A molded body was obtained. Table 3 shows the measurement results of oxygen permeability.

Example 17
A cellulose fiber suspension was prepared in the same manner as in Example 7, and a composite molded body was obtained in the same manner as in Example 11. Table 3 shows the measurement results of oxygen permeability.

Comparative Examples 5, 6, and 7
A composite molded body was obtained in the same manner as in Examples 14, 16, and 17 except that drying by heating was not performed. Table 3 shows the measurement results of oxygen permeability.

実施例１１〜１３は、加熱による乾燥時間の異なる膜状成形体であり、高い酸素バリア性を有していることが分かる。また１５０℃、６０分加熱した実施例１２において最も高い酸素バリア性を示したことから、加熱による脱水と膜状成形体へのダメージを制御することで、より高い酸素バリア性を得られると考えられる。

It turns out that Examples 11-13 are film-form molded objects from which the drying time by heating differs, and have a high oxygen barrier property. Moreover, since the highest oxygen barrier property was shown in Example 12 heated at 150 ° C. for 60 minutes, it is considered that higher oxygen barrier property can be obtained by controlling dehydration and damage to the film-shaped molded body by heating. It is done.

  Examples 11 and 14 to 17 are film-shaped molded articles prepared from cellulose fiber suspensions having different fiber diameters and carboxyl group contents. It can be seen that the oxygen barrier property, particularly the oxygen barrier property at 50% RH, is improved as compared with the case where heating is not performed (Comparative Examples 5 to 7). In particular, Examples 11, 14, 15, 16, and 17 in which the carboxyl group content of the cellulose fiber was 1.0 or more and the average aspect ratio was 350 or less obtained high oxygen barrier properties. In Examples 11 and 15 where the carboxyl group content of the cellulose fiber was 1.4 and the average aspect ratio was 235 and 180, higher oxygen barrier properties were obtained.

Claims (4)

A process for forming a film-like product of a suspension containing cellulose fibers, and then a method for producing a film-like molded article having a drying step by heating,
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.   The manufacturing method according to claim 1, wherein, in the drying step by heating, the moisture content of the film-shaped molded body is dried to 1 to 90% of an equilibrium moisture content at 23 ° C and 60% RH.   The manufacturing method of the film-shaped molded object of Claim 1 or 2 whose heating temperature is 50-250 degreeC in the drying process by the said heating.   Between the step of forming a film of the suspension containing the cellulose fibers and the drying step by heating, the water content of the film is balanced at a temperature of 20 ° C. ± 15 ° C. and a humidity of 45 to 85% RH. The manufacturing method of the film-shaped molded object of any one of Claims 1-3 which has the process hold | maintained in the state dried to the rate.