JP2018083863A - Resin molding and manufacturing method of resin molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a resin molding to be used for a display material with an easy production process or display method, capable of repeated display of writing or deleting information, and a manufacturing method thereof.SOLUTION: A resin molding 10 at least includes a synthetic resin 4 having at least one of an aqueous dispersion component and an aqueous emulsion component, and a hydrophilic fiber 3. If a haze of the resin molding 10 is HZwhen a moisture content of the resin molding 10 is 25% or more and a haze of a resin molding 10 with a moisture content of 8% or less is HZ, HZand HZsatisfy following expressions (1) and (2): HZ-HZ≥15(%)...(1); and HZ≤5(%)...(2).SELECTED DRAWING: Figure 1

Description

  The present invention relates to a resin molded body and a method for producing the resin molded body.

  In recent years, many display materials capable of repeatedly displaying and erasing information have been developed, and heat, magnetism, and light are mainly used as the display method. Such display materials are designed precisely by controlling, for example, the crystallinity of a low molecular material, the orientation of a liquid crystal material, and the molecular skeleton. Such display materials are often displayed on a card, and are used for point cards, ID cards, and the like, and are widely used. However, a dedicated device is necessary to utilize them. For this reason, there is a demand for a display material that can be used in a simpler manner and is inexpensive and highly visible.

  In recent years, the use of environmentally friendly materials (biomass materials) has attracted attention against the background of global warming, environmental pollution, waste problems, etc. due to depletion of resources and an increase in atmospheric carbon dioxide concentration. This biomass material has features such that the amount of fossil resources used at the time of manufacture is small, and that it can be processed with low energy at the time of disposal and emits less carbon dioxide. Among biomass materials, cellulose, which accounts for about half of its production, is expected to be used effectively due to its large production. Furthermore, cellulose has a high strength, a high elastic modulus, and an extremely low thermal expansion coefficient, and has no glass transition point with respect to heat resistance, and exhibits a high thermal decomposition temperature of 230 degrees. On the other hand, it cannot be said that cellulose is often used as a material for its large production. One of the reasons is low solubility and dispersibility in aqueous and non-aqueous solvents. Cellulose is a homopolysaccharide in which D-glucopyranose, which is a 6-membered ring of glucose, is Β- (1 → 4) glucoside-bonded, and has hydroxyl groups at the C2, C3 and C6 positions. Therefore, a strong hydrogen bond is formed in and between the molecules and does not dissolve in water or a general solvent.

  However, when cellulose is treated using an oxidation reaction catalyzed by N-oxyl compounds such as 2,2,6,6-tetramethyl-1-piperidinyloxy radical (TEMPO), the degree of treatment is adjusted. A homogeneous dispersion can be obtained by mild dispersion treatment in water. At this time, the cellulose is defibrated to the microfibril level and exists as a cellulose fiber dispersion in which the fiber width is dispersed to several nm to several hundred nm. Furthermore, this TEMPO oxidation reaction is extremely adaptable to the environment of the reaction process, such as using only water as a reaction medium without using an organic solvent, and completing the reaction in a short time under mild conditions at normal temperature and normal pressure.

The mechanism by which the oxidized cellulose obtained by the TEMPO oxidation reaction is dispersed to the nano level by a mild mechanical treatment is known as follows. First, the hydroxyl group at the C6 position on the surface of cellulose microfibrils is selectively oxidized by an oxidation reaction, and a carboxyl group is introduced via an aldehyde group. And this carboxyl group repels charge as an anion, and shows an osmotic pressure effect in a dispersion medium. For this reason, nano-order microfibrils are easily isolated, and a homogeneous cellulose fiber dispersion can be obtained.
Furthermore, cellulose modified products having different characteristics can be obtained by forming various salts having a cationic property as a counter ion by utilizing the electrostatic action of a carboxyl group introduced into cellulose. In this treatment, since the crystallinity of the raw material cellulose can be maintained without breaking, it has high physical properties.

As described above, cellulose that can be used as a nano-dispersion, liquid state, or modified substance has a low environmental load and has higher physical properties. Therefore, the treatment and oxide by the TEMPO oxidation reaction are a new use of cellulose. Expected as a form.
One example that is being actively developed for industrial use is compounding with resin. By mixing a cellulose dispersion in the resin, it is intended to enhance the functionality of the resin utilizing the light weight, high strength, high elastic modulus, low linear thermal expansion coefficient, and high heat resistance of cellulose.
In this case, the dispersibility of the cellulose fibers in the resin is mentioned as an important factor for improving the functionality. It is known that when the cellulose fibers are unevenly distributed or aggregated, the effect of mixing the cellulose fibers is significantly reduced.

  Therefore, in order to increase the affinity with a hydrophobic resin and improve the dispersibility, a method of forming a composite using an aqueous emulsion as a resin has been developed. In the case of an aqueous emulsion, water having high compatibility with cellulose fibers is mainly used as a dispersion medium, and even if it has a high molecular weight, it is dispersed as fine resin particles in the dispersion medium. For this reason, the thickening at the time of mixing with a cellulose fiber can be suppressed, and handling becomes easy. On the other hand, a mixture of cellulose fibers and an aqueous emulsion has a low solid content, and water having a high boiling point is used as a dispersion medium. For this reason, much energy and time are required for removing the dispersion medium. As a result, the productivity of materials using cellulose was generally low.

  As a technique for improving the productivity of materials using cellulose, for example, there is one disclosed in Patent Document 1. This patent document describes a technique in which a mixture of an aqueous emulsion and cellulose fibers is gelled using a cellulose coagulant, filtered on a porous substrate, and then dried.

Japanese Patent No. 5747818

As described above, technologies for improving the productivity of materials using cellulose have been disclosed so far, but cellulose is used as a display material capable of repeatedly displaying and erasing information. No technology was disclosed.
The present invention provides a resin molded body used for a display material that has a simple manufacturing process and a display method, and that can repeatedly display and write information, and a method for manufacturing the same.
In addition, the resin molded body mentioned here refers to various forms such as a film shape, a sheet shape, and a structure formed by using a composition in which a synthetic resin having an aqueous dispersion or aqueous emulsion and a hydrophilic fiber are mixed. Point to. The composition is a mixture of synthetic resin and hydrophilic fiber, and refers to a state before the structure formation or reaction by heating or light.

In order to solve the above problems, a resin molded body according to an aspect of the present invention includes at least a synthetic resin having at least one of an aqueous dispersion component and an aqueous emulsion component, and a hydrophilic fiber. The average fiber width is in the range of 3 nm to 200 nm, and the content of the hydrophilic fiber is in the range of 5 parts by weight to 200 parts by weight with respect to 100 parts by weight of the synthetic resin. The resin molded body according to another aspect of the present invention includes at least a synthetic resin having at least one of an aqueous dispersion component and an aqueous emulsion component, and a hydrophilic fiber, and the water content of the resin molded body is 25% or more. the haze of the shaped body and HZ _1, the haze of the water content of 8% or less of the resin molded body when a HZ _2, HZ ₁ and HZ ₂ is less than (1 It satisfies the formula and (2) below.
HZ ₁ −HZ ₂ ≧ 15 (%) (1)
HZ ₂ ≦ 5 (%) (2)

  According to each aspect of the present invention, it is possible to provide a resin molded body used for a display material which can be simply displayed in a manufacturing process and a display method and can be repeatedly written and erased, and a method for manufacturing the same.

It is a figure which shows typically a part of resin molding which concerns on embodiment of this invention. It is a figure which shows typically the manufacturing process of the resin molding which concerns on embodiment of this invention.

  Below, with reference to drawings, the resin fabrication object and its manufacturing method concerning the embodiment of the present invention are explained. Here, the drawings are schematic, and the relationship between the thickness and the planar dimensions, the ratio of the thickness of each layer, and the like are different from the actual ones. Further, the embodiment described below exemplifies a configuration for embodying the technical idea of the present invention, and the technical idea of the present invention is that the material, shape, structure, etc. of the component parts are as follows. It is not something specific. The technical idea of the present invention can be variously modified within the technical scope defined by the claims described in the claims.

(Configuration of resin molded body 10)
FIG. 1 is a diagram schematically showing a part of a resin molded body according to an embodiment of the present invention. More specifically, FIG. 1 (a) is a view showing the appearance of a resin molded body in a dry state (normal temperature and humidity), and FIG. 1 (b) is a resin molded body in a wet state (water content is saturated). It is a figure which shows the external appearance of a body. Moreover, FIG.1 (c) is a figure which shows the cross section of the resin molding in a dry state (normal temperature normal humidity), and FIG.1 (d) is a figure of the resin molding in a wet state (water content is saturated). It is a figure which shows a cross section. In addition, the shaded portion shown in FIGS. 1C and 1D is a cross section.

  As shown in FIG. 1, the resin molded body 10 according to the present embodiment is formed by aggregating a plurality of resin units 1. Each resin unit 1 includes at least a synthetic resin aggregate 2 and hydrophilic fibers 3 that exist so as to cover the surface of the synthetic resin aggregate 2. Furthermore, as shown in FIG. 1, the synthetic resin aggregate 2 is formed by agglomerating several to several tens of synthetic resins 4. In other words, the resin molded body 10 according to this embodiment includes a synthetic resin aggregate 2 formed by aggregating the synthetic resin 4 and a hydrophilic fiber 3 formed so as to cover the surface of the synthetic resin aggregate 2. The resin unit 1 containing these is provided. The above-mentioned “room temperature and humidity” means “23 ° C., 50% RH”, and “room temperature and humidity” means “23 ° C., 50% RH environment”.

Hereinafter, the detail of the synthetic resin 4 and the hydrophilic fiber 3 mentioned above is demonstrated.
<Synthetic resin 4>
The resin molding 10 according to the present embodiment includes a synthetic resin 4 having at least one of an aqueous dispersion component and an aqueous emulsion component. Here, the aqueous dispersion and the aqueous emulsion are sometimes referred to as an aqueous dispersion and an aqueous emulsion, respectively, and any aqueous resin dispersed in an aqueous dispersion medium containing water is included in this embodiment. In addition, as an expression to be paired with the hydrophilic fiber 3, an expression of a synthetic resin 4 is used as a general term as a resin of an aqueous dispersion and an aqueous emulsion.
These aqueous dispersions and aqueous emulsions are those in which water is used as a main dispersion medium and a polymer is dispersed to a particle size of submicron to several microns. By volatilizing these dispersion media, the polymers are deformed and fused to form a continuous structure.

Aqueous dispersions and aqueous emulsions have the advantage that the degree of freedom in design is higher than that of water-soluble monomers and water-soluble oligomers as a resin, and materials can be selected according to the intended performance and function. Furthermore, the dispersion stability in the dispersion medium is imparted by the addition of an emulsifier or the introduction of a hydrophilic group into the resin, but the synthetic resin 4 itself is hydrophobic and has high water resistance and moisture resistance. . Therefore, it is difficult to be influenced by the external humidity environment, and when the moisture content of the resin molded body 10 is changed, there is no significant deformation, and the structure as the resin molded body 10 can be maintained.
In addition, although the aqueous dispersion and the aqueous emulsion have a high degree of polymerization of the synthetic resin 4, since the synthetic resin 4 forms individual fine particles, the viscosity as a coating liquid is low. Therefore, even if the hydrophilic fiber 3 which is a constituent material of the present embodiment has a high viscosity, good mixing properties can be obtained.

  As described above, the aqueous dispersion and aqueous emulsion in the present embodiment are dispersed as resin particles in an aqueous dispersion medium containing water. And the resin particle has distribution to some extent in particle diameter. When the resin molded body 10 is coated and molded before molding, the interaction with the hydrophilic fibers 3 and other components to be mixed, the melting temperature, and the like affect the agglomeration form of the resin particles when deformed and fused. For this reason, the particle diameter of the synthetic resin 4 does not correspond to an element that uniquely determines the size of the hydrophobic region made of the synthetic resin 4 in the structure of the resin molded body 10. However, if the particle diameter of the synthetic resin 4 is too small, the specific surface area is large, and the interaction with the hydrophilic fibers 3 and other components to be mixed due to the electric action on the surface of the resin particles is likely to increase, The fusion between the resins 4 is less likely to occur. As a result, the size of the hydrophobic region made of the synthetic resin 4 is reduced. In this case, since there are a large number of interfaces between the hydrophobic region and the hydrophilic region, scattering by the light interface occurs regardless of the moisture content, and the haze of the resin molded body 10 increases. On the other hand, when the particle diameter of the synthetic resin 4 is too large, it becomes difficult to uniformly disperse the synthetic resin 4 and other components including the hydrophilic fibers 3 when the resin molded body 10 is molded. Therefore, the particle diameter of the aqueous dispersion or aqueous emulsion is preferably within the range of 0.01 μm or more and 10 μm or less, which is an appropriate size for the purpose of this embodiment.

Aqueous dispersions and aqueous emulsions are roughly classified into anionic, cationic and nonionic properties depending on ionicity. In the present embodiment, any use is not limited. However, when the hydrophilic fiber 3 to be mixed is anionic, mixing with the cationic synthetic resin 4 may inhibit the charge, so anionic or nonionic Is preferred.
Examples of the synthetic resin 4 made of an aqueous dispersion or an aqueous emulsion include vinyl acetate, urethane, acrylic, styrene, phenol, amino, amide, polyester, ethylene, and polyvinyl alcohol. . These may be used alone, or may be copolymerized or used in combination of two or more. A reactive synthetic resin 4 may also be used. In that case, for example, a curing agent, a curing catalyst, a photopolymerization initiator, a chain transfer agent, and the like can be used in combination. Here, in order to improve the brittleness caused by the phase separation between the synthetic resin 4 and the hydrophilic fiber 3 constituting the resin molded body 10, the synthetic resin 4 preferably has flexibility, and a urethane type is used. More preferred. In the urethane system, a polyester system, a polyether system, a polycarbonate system, and the like have been developed depending on the kind of polyol constituting the urethane structure, and any of them can be used.

<Hydrophilic fiber 3>
As the main role of the hydrophilic fiber 3 used in the present embodiment, the hydrophobic region of the synthetic resin 4 made of an aqueous dispersion or aqueous emulsion and the swelling ratio due to water content are different, so that incident light is incident on the interface between the hydrophobic regions. To cause scattering. Another role is to adjust the aggregate size of the particles of the synthetic resin 4 or to sufficiently bond the aggregated interfaces of the synthetic resin 4 by having an appropriate interaction with the synthetic resin 4. . In addition, if the fiber width of the hydrophilic fiber 3 is too large, scattering due to the light interface occurs regardless of the water content, and the haze of the resin molded body 10 increases, so that the fiber width of the hydrophilic fiber 3 is sufficiently small. There is a need. In view of the above, the hydrophilic fiber 3 can be used as long as it satisfies the present embodiment in at least the swelling ratio in water, ionicity, strength, and fiber width.

  As the hydrophilic fiber 3 satisfying the above requirements, for example, a cellulose fiber obtained by performing mechanical treatment after oxidizing cellulose by a TEMPO oxidation reaction and defibrating the fiber width to a nano level can be suitably used. By subjecting cellulose to a TEMPO oxidation reaction, the hydroxyl group at the C6 position on the microfibril surface of cellulose is selectively oxidized, and a carboxyl group is introduced via an aldehyde group. This charge repulsion of the carboxyl group enables defibration down to the nano level. Moreover, since cellulose maintains I-type crystals and there is almost no decrease in crystallinity, the inherent high elastic modulus of cellulose can be maintained. In addition, since the ionicity can be controlled by the amount of carboxyl groups introduced by the TEMPO oxidation reaction conditions, and the amount of carboxyl groups introduced by the TEMPO oxidation reaction conditions can be controlled, it depends on the synthetic resin applied to the resin molding. Thus, it is possible to adjust the amount of charge derived from the carboxyl group. Cellulose has three hydroxyl groups per glucose unit, and has a high hydrophilicity because it has a structure in which a number of hydroxyl groups are exposed on the microfibril surface by being fibrillated to the nano level. The swelling rate of becomes extremely high.

  The cellulose fibers used in the present embodiment preferably have an average fiber width of 3 nm to 200 nm. When the fiber having a fiber width larger than 200 nm is included, the fiber width approaches the wavelength of visible light, leading to a decrease in transparency of the resin molded body 10 and a decrease in surface area and a decrease in fiber entanglement. Causes a drop. Further, in the case of fibers having a fiber width of less than 3 nm, it is difficult to produce a fiber having characteristics excellent in mechanical strength and uniformity. Therefore, the fiber width is preferably 3 nm or more. Further, the longer the fiber length, the more likely the fibers are entangled with each other. Therefore, the effect is easily exhibited at a low content. However, if the length is too long, the energy required for dispersion and generation increases and dispersion becomes difficult. Therefore, the fiber length is preferably 10 nm or more and 10,000 nm or less.

Although the measuring method is not specifically limited about the fiber width of the cellulose fiber used by this embodiment, For example, it can measure with the following method. A product in which cellulose fibers are dispersed in water so that the solid content concentration is in the range of 0.001 wt% or more and 0.01 wt% or less is spread on mica and dried naturally. Then, the fiber width of the cellulose fiber can be confirmed (measured) by observing the cellulose fiber with a transmission electron microscope. In some cases, a good solvent may be added to the composition 20 for dilution, followed by drying and curing steps after development into mica.
Moreover, the measuring method of the fiber width of the cellulose fiber in the resin molding 10 using other than a transmission electron microscope is a method using an atomic force microscope, for example. Specifically, when the phase mode of the atomic force microscope is used, the phase of the cantilever vibration is shifted due to the difference in characteristics between the cellulose fiber and the synthetic resin, so the cellulose fiber is detected from the phase shift and the width is measured. can do.

  For example, natural cellulose or chemically modified cellulose can be used as a material starting from cellulose used in the present embodiment. Specifically, pulp made from wood such as bleached and unbleached kraft wood pulp, prehydrolyzed kraft wood pulp, sulfite wood pulp, or non-wood pulp such as cotton and bacterial cellulose, and mixtures thereof Can do. In addition, any of materials obtained by physically or chemically treating these may be used. Preferably, natural cellulose having crystalline form I is desirable because of its high material properties such as mechanical properties, thermal properties and chemical resistance.

As the cellulose used in the present embodiment, for example, cellulose in which a part of the hydroxyl group of cellulose is substituted with a carboxyl group is used. There is no restriction | limiting in particular as a method to introduce | transduce a carboxyl group into the cellulose used as a raw material, According to the objective, it selects suitably. For example, it can be appropriately selected from the generally known methods of oxidizing from a hydroxyl group to a carboxylic acid via an aldehyde. Among them, a method using an N-oxyl compound as a catalyst and using a hypohalite or a halite as a co-oxidant is preferable. In particular, 2,2,6,6-tetramethyl-1-pipedinyloxy radical (TEMPO) is used as a catalyst, and an oxidizing agent such as sodium hypochlorite and bromide such as sodium bromide while adjusting pH. The TEMPO oxidation method in which the reaction is carried out using a chemical compound is preferable from the standpoint of complete reaction in water without using an organic solvent as a reaction medium, availability of reagents, cost, and reaction stability.
In this TEMPO oxidation method, only the surface of crystalline cellulose microfibrils is oxidized, and no oxidation occurs inside the crystal, so that the crystal structure can be maintained. For this reason, the product has the inherent high strength, high elastic modulus, low linear thermal expansion coefficient, and high heat resistance characteristics of cellulose.

(Oxidation treatment by TEMPO oxidation method)
In the present embodiment, the oxidation treatment by the TEMPO oxidation method described above was performed according to the following procedure.
The cellulose is oxidized by adding an N-oxyl compound and an oxidizing agent or a co-oxidizing agent to cellulose dispersed in water. Sodium hydroxide is added during the oxidation reaction to control the pH in the reaction system from 9 to 11. The reaction temperature is preferably 0 ° C. or higher and 40 ° C. or lower. At this time, the hydroxyl group at the C6 position on the surface of the cellulose fiber is oxidized to a carboxyl group. After completion of the reaction, it is sufficiently washed and collected, and can be used as a constituent material (hydrophilic fiber 3) in the present embodiment.

In addition, as an oxidizing agent, hypohalous acid or its salt, a halous acid or its salt can be used, for example, Sodium hypochlorite is preferable. Examples of the co-oxidant include lithium bromide, potassium bromide, sodium bromide and the like, and sodium bromide is preferable because of easy handling.
Content of the carboxyl group introduce | transduced into a cellulose can be adjusted by setting reaction conditions suitably. Cellulose introduced with a carboxyl group is dispersed in the dispersion medium by the charge repulsion of the carboxyl group through a dispersion step described later. Therefore, if the content of carboxyl groups in the cellulose is too small, the cellulose is stably dispersed in the dispersion medium. I can't let you. Moreover, when there is too much content of the carboxyl group in a cellulose, the affinity to a dispersion medium will increase and water resistance will fall.

From these viewpoints, the content of the carboxyl group introduced into the cellulose is preferably in the range of 0.5 mmol or more and 3 mmol or less per dry weight. Furthermore, the range of 0.8 mmol or more and 2.5 mmol or less is more preferable.
In addition, the amount of carboxyl groups contained in cellulose is calculated by the following method, for example. 0.2 g of dry weight conversion of oxidized cellulose is put in a beaker, and 80 ml of ion exchange water is added. Thereto is added 5 ml of 0.01 M sodium chloride aqueous solution, and 0.1 M hydrochloric acid is added while stirring to adjust the whole to pH 2.0.

Here, 0.1M sodium hydroxide aqueous solution was injected at 0.05 ml / 30 seconds using an automatic titrator (AUT-701, manufactured by Toa DKK Co.), and the conductivity and pH value were measured every 30 seconds. Continue to measure. The carboxyl group content can be calculated by obtaining a titration amount of sodium hydroxide from the obtained conductivity curve.
After stopping the oxidation reaction, the product is recovered from the reaction solution by filtration. After completion of the reaction, the carboxyl group introduced into the cellulose forms a salt having a metal ion derived from a cation present in the reaction medium as a counter ion.

As a method for recovering cellulose after oxidation treatment, for example,
(A) a method in which the carboxyl group is filtered off while forming a salt;
(B) A method of adjusting the inside of the system under acidity by adding an acid to the reaction solution and filtering it off as a carboxylic acid,
(C) The method of filtering after adding an organic solvent and making it aggregate is mentioned.
Among these, from the viewpoint of handling properties, recovery efficiency, and waste liquid treatment, (B) a method of recovering as carboxylic acid is preferable. Moreover, since the direction which does not contain a metal ion as a counter ion can suppress the production | generation of a by-product and is excellent in substitution efficiency, the method collect | recovered as (B) carboxylic acid is preferable.

In addition, the metal ion content in the cellulose after the oxidation reaction can be examined by various analysis methods. For example, it can be simply examined by elemental analysis such as EPMA method or X-ray fluorescence analysis method using an electron beam microanalyzer. be able to. (A) When recovered using a method of filtering while forming a salt, the content of metal ions is 5 wt% or more, whereas when recovered by a method of filtering (B) as carboxylic acid, 1 wt. % Or less.
Furthermore, the recovered cellulose can be purified by repeated washing, and the catalyst and by-products can be removed. At this time, the amount of remaining metal ions and salts can be reduced by repeating washing with pure water after washing with a cleaning solution prepared using hydrochloric acid or the like under acidic conditions of pH 3 or lower.

By adding a hydroxide containing an alkali metal or alkaline earth metal to a suspension of cellulose into which a carboxyl group has been introduced, a part or all of the carboxyl group is converted into an alkali metal salt type or an alkaline earth metal salt type. Replaced. Cellulose exhibits an osmotic effect in the dispersion medium due to the charge of the carboxyl group, and can be dispersed in the nano-order. The addition amount of the alkali metal or alkaline earth metal hydroxide is preferably within the range of 0.8 equivalents or more and 2 equivalents or less with respect to the carboxyl group introduced into the cellulose.
In particular, the range of 1 equivalent to 1.8 equivalents is more preferable because the counter ion exchange can be performed without adding an excessive amount of alkali metal or alkaline earth metal hydroxide. It is also possible to remove an excessive amount of alkali metal or alkaline earth metal hydroxide by washing the cellulose again after adding an excessive amount of alkali metal or alkaline earth metal hydroxide. By removing excess alkali, it is possible to suppress deterioration of materials such as cellulose over time.
Here, the alkali metal species or alkaline earth metal species is not particularly limited as long as cellulose is dispersed in the nano order, but sodium is preferable from the viewpoint of dispersibility.

(Manufacturing method of the resin molding 10)
Hereinafter, the manufacturing method of the resin molding 10 which concerns on this embodiment is demonstrated. FIG. 2 is a diagram schematically showing a manufacturing process of the resin molded body 10 according to the present embodiment.
The resin molded body 10 in the present embodiment is formed by a composition 20 in which a synthetic resin 4 made of an aqueous dispersion or an aqueous emulsion and a hydrophilic fiber 3 are mixed. At this time, the miscibility with the synthetic resin 4 can be improved by dispersing the hydrophilic fiber 3 in advance with water or an aqueous solvent. For the purpose of not lowering the solid content concentration of the coating liquid in wet coating, the undispersed hydrophilic fiber 3 may be subjected to a dispersion treatment in the synthetic resin 4. As a dispersion treatment method, various known dispersion treatments are possible in the case where there is no problem in the dispersion of the resin particles of the aqueous dispersion or aqueous emulsion in the dispersion medium or the subsequent formation of the resin molded body 10. It is. For example, homomixer processing, mixer processing with rotary blade, high pressure homogenizer processing, ultra high pressure homogenizer processing, ultrasonic homogenizer processing, nanogenizer processing, disc type refiner processing, conical type refiner processing, double disc type refiner processing, grinder processing, ball mill processing , Kneading treatment with a biaxial kneader, underwater facing treatment, and the like. Among these, the mixer treatment with a rotary blade, the high-pressure homogenizer treatment, the ultra-high pressure homogenizer treatment, and the ultrasonic homogenizer treatment are preferable from the viewpoint of miniaturization efficiency. Of these processes, two or more processing methods can be combined and distributed.

  Here, the hydrophilic fiber 3 to be mixed with the synthetic resin 4 is preferably 5 parts by weight or more and 200 parts by weight or less with respect to 100 parts by weight of the synthetic resin 4. When the amount is less than 5 parts by weight, swelling due to the water content of the hydrophilic fibers 3 in the resin molded body 10 hardly occurs, and as a result, the cloudiness and opacity may be lowered. When the amount exceeds 200 parts by weight, the hydrophobic region of the synthetic resin 4 is dispersed in the matrix of the hydrophilic fiber 3, and it becomes difficult to control the moisture content of the resin molded body 10 itself. Since it decreases relatively, it may result in a decrease in cloudiness and opaqueness as a result.

Although there is no restriction | limiting in particular as a method of forming the resin molding 10 using the composition 20 which mixed the synthetic resin 4 and the hydrophilic fiber 3 which were prepared in this way, The composition 20 has fluidity | liquidity. Therefore, the resin molded body 10 can be obtained by wet-coating and curing on the support 40 such as a resin base or a glass base.
As a coating method, a known method can be used. Specifically, bar coating, dip coating, spin coating, flow coating, spray coating, roll coating, gravure roll coating, air doctor coating, blade coating, wire doctor coating, knife coating Methods, reverse coating method, transfer roll coating method, micro gravure coating method, kiss coating method, cast coating method, slot orifice coating method, calendar coating method, die coating method and the like can be used.

2A schematically shows that the composition 20 is wet-coated on the support 40 using the bar coater 30. FIG.
For the purpose of improving the wettability and adhesion of the substrate on which the composition 20 in which the synthetic resin 4 and the hydrophilic fiber 3 are mixed is applied, the substrate may be pretreated. The pretreatment method is not particularly limited. For example, an anchor layer may be formed in advance, or corona treatment, plasma treatment, flame treatment, or the like may be performed.
The resin molded body 10 can be formed by drying the composition 20 coated on the support 40, that is, by removing excess dispersion medium in the system. Furthermore, after the resin molded body 10 is manufactured, the resin molded body 10 may be additionally heated for the purpose of reaction progress of the resin and other characteristics improvement. Moreover, when using a photoreactive material, you may irradiate the resin molding 10 with the light of the wavelength which advances reaction.
The resin molded body 10 formed in this way is shown in FIG.

The thickness T of the resin molded body 10 obtained in the present embodiment is preferably in the range of 1 μm to 500 μm, and particularly preferably in the range of 10 μm to 200 μm. When the thickness T is less than 1 μm, the strength of the resin molded body 10 becomes extremely weak and unsuitable for production. On the other hand, if the thickness exceeds 500 μm, the drying speed is very long, and the productivity is extremely lowered, and excessive moisture remains in the resin molded body 10, which is not preferable.
The light transmittance at 660 nm when converted to 20 mm thickness of the obtained resin molded body 10 is preferably 70% or more when the resin molded body 10 is dried. Furthermore, 80% or more is particularly preferable. The resin molded body 10 according to the present embodiment utilizes reversibility of transparency due to moisture content, and improves visibility by contrast with a cloudy and opaque state by increasing transparency at least visually in the transparent state. can do. Here, “the state where the resin molded body 10 is dried” refers to a state where the moisture content of the resin molded body 10 is 8% or less. Alternatively, it means a state where the moisture content of the resin molded body 10 has reached equilibrium in a humidity environment lower than room temperature and normal humidity.

As the support 40 that forms the resin molded body 10, for the purpose of improving the visibility, a layer having a metallic luster or a layer having various colors may be used. These layers having metallic luster and various colors can be formed in advance on the side of the support 40 on which the resin molded body 10 is formed, or when the support 40 is transparent. It is also possible to form the support 40 on the surface opposite to the side on which the resin molded body 10 is formed.
As the other support 40 that forms the resin molded body 10, a laminate in which a moisture retention layer having moisture retention is laminated may be used for controlling the water absorption speed and transparency. The moisturizing agent constituting the moisturizing layer is not particularly limited. For example, cellulose, cellulose derivative, chitin, chitosan derivative, starch, hyaluronic acid, alginic acid, gelatin, kaolin, dextrin, glycerin, polyglycerin, D-sorbitol, PVA, etc. In particular, glycerin and sorbitol are preferable. Moreover, only one type of moisturizing agent used for the moisturizing layer may be used, and two or more types may be used in combination.

<Various additive materials>
In the present embodiment, a thermosetting resin may be further added to the resin molded body 10. When the thermosetting resin is used, the step of removing the dispersion medium such as water contained in the coated composition 20 and the molding step of fusing the particles of the synthetic resin 4 can proceed simultaneously. Further, since the resin can be selectively cured by irradiating the resin molding 10 with active energy rays such as ultraviolet rays and electron beams, a photo-curable resin may be further added. . In addition, you may insert a heating process for the purpose of removing a solvent or improving the reactivity in the process of hardening reaction.

By adding these thermosetting resins and photocurable resins to the resin molded body 10, the binding property between the hydrophobic regions of the synthetic resin 4 made of an aqueous dispersion or an aqueous emulsion can be improved, Adjustments suitable for various purposes such as controlling the physical properties and the water absorption speed of the hydrophilic fiber 3 can be made.
Moreover, in order to form a crosslinked structure for the purpose of improving water resistance and abrasion resistance, the resin molded body 10 may contain various crosslinking agents. Although it does not limit as a crosslinking agent which forms a crosslinked structure by heating, For example, an oxazoline, a divinyl sulfone, a carbodiimide, a dihydrazine, a dihydrazide, an epichlorohydrin, a glyoxal, an organic titanium compound, an organic zirconium compound etc. can be used. Moreover, it is also possible to mix and use two or more of them. Among these, carbodiimide is preferable because it can efficiently form a crosslinked structure without applying large energy.

Furthermore, when the resin molding 10 is irradiated with active energy rays such as ultraviolet rays or electron beams to cure the resin, a photocrosslinking agent, a photopolymerization initiator, or the like may be used. These types are not particularly limited, and examples thereof include acetophenone photopolymerization initiators, benzoin photopolymerization initiators, benzophenone photopolymerization initiators, thioxanthone photopolymerization initiators, and thioxanthone photopolymerization initiators. it can.
In addition, a function to be added for the purpose of adjusting the viscosity, adjusting the drying speed, improving the affinity with different materials, and the like within a range in which aggregation or precipitation does not occur in the composition 20 in which the synthetic resin 4 and the hydrophilic fiber 3 are mixed. Depending on the situation, various organic solvents including water can be mixed.

At this time, in order to relieve shock caused by mixing different solvents, for example, the addition rate, pH adjustment, stirring method, temperature, and the like can be appropriately selected.
Moreover, the resin molding 10 may contain a metal etc. Examples of the metal contained in the resin molded body 10 include gold, silver, platinum, palladium, ruthenium, iridium, rhodium, osmium, platinum group elements, iron, lead, copper, chromium, cobalt, nickel, manganese, vanadium. Further, metals such as molybdenum, gallium, and aluminum, alloys thereof, oxides, double oxides, carbides, and the like can be used.

As a method for supporting the metal, for example, in addition to a method of mixing fine particles such as metal or metal oxide, a cellulose fiber having a carboxyl group forms a metal or metal oxide complex, and a reducing agent is added to form a metal. There is a method of precipitating as particles. When this method is used, fine metal particles are uniformly immobilized on the surface of the cellulose fiber, so that the effect can be efficiently exhibited with a small amount of metal.
In the range where aggregation and precipitation are not generated, various additives including water-soluble polysaccharides and various resins may be included for the purpose of increasing the charge repulsion in the composition 20 and controlling the viscosity of the dispersion. Good. For example, chemically modified cellulose, carrageenan, xanthan gum, guar gum, gum arabic, sodium alginate, agar, solubilized starch, glycerin, sorbitol, antifoaming agent, water-soluble polymer, synthetic polymer and the like can be included. Alternatively, various solvents may be included for imparting functionality such as coatability and wettability. For example, alcohols, cell solves, glycols and the like can be included. Furthermore, various dyes, pigments, organic fillers, inorganic fillers and the like may be included for the purpose of imparting design properties. Further, for the purpose of improving the reactivity, the pH can be adjusted by adding an acid or an alkali.

About control of the transparency of the resin molding 10 by this embodiment, it is possible to use the moisture content of the resin molding 10 as a parameter | index. The water content of the resin molded body 10 can be changed, for example, by immersing the resin molded body 10 in a dry state in water. When the haze of the surface when the moisture content of the resin molded body 10 reaches saturation when sufficiently immersed in water is HZ ₁ , the moisture content is dehumidified and the moisture content shows a moisture content in an equilibrium state with normal temperature and normal humidity. when the haze was HZ _2, it is preferable to satisfy HZ 1 -HZ ₂ ≧ 15 (%) of. In order to ensure visibility, it is preferable to have a difference of 15% or more as haze due to a change in moisture content, and it is more preferable to have a difference of 30% or more. Furthermore, the haze of the resin molded body 10 can be generally used as the resin molded body 10 having transparency at normal temperature and humidity by setting HZ ₂ ≦ 5 (%). In other words, when the haze when the moisture content of the resin molded body 10 is 25% or more is HZ ₁ and the haze when the moisture content of the resin molded body 10 is 8% or less is HZ ₂ , HZ ₁ − It is preferable to satisfy HZ ₂ ≧ 15 (%).

(Effect of this embodiment)
(1) The resin molded body 10 according to an embodiment of the present embodiment includes at least a synthetic resin 4 having at least one of an aqueous dispersion component and an aqueous emulsion component, and a hydrophilic fiber 3, and includes the water content of the resin molded body 10. When the haze of the resin molded body 10 in a state where the rate is 25% or more is HZ ₁ and the haze of the resin molded body 10 in the state where the moisture content is 8% or less is HZ ₂ , HZ ₁ and HZ ₂ are The following expressions (3) and (4) are satisfied.
HZ ₁ −HZ ₂ ≧ 15 (%) (3)
HZ ₂ ≦ 5 (%) (4)
With such a configuration, it is possible to repeatedly write and erase various types of visible information by using reversible changes in transparency due to changes in moisture content.

  More specifically, with such a configuration, the transparency is reversibly changed from a transparent state to a cloudy and opaque state only by changing the moisture content. The difference between the transparent state and the cloudy opaque state is estimated as follows. That is, in the case of a transparent state (that is, when the resin molded body 10 is in a dry state), the hydrophobic region by the synthetic resin 4 including at least one of the aqueous dispersion component and the aqueous emulsion component, and the hydrophilic fiber 3 The hydrophilic region is distributed in phase separation. Here, since the refractive index of the synthetic resin 4 and the hydrophilic fiber 3 is close and the fiber width of the hydrophilic fiber 3 is smaller than the wavelength of visible light, light incident from one side is transmitted to the opposite side without being scattered. So it looks transparent. On the other hand, in the case of a cloudy opaque state (that is, when the resin molded body 10 is in a wet state), the hydrophilic fibers 3 swell so that the refractive index at the interface between the particles of the synthetic resin 4 and the hydrophilic fibers 3. This is due to the fact that there is a difference, and it is refracted and scattered many times at the interface, so that it appears cloudy. The swelling behavior of the hydrophilic fiber 3 is controlled only by the moisture uptake of the hydrophilic fiber 3, that is, the moisture content of the hydrophilic fiber 3, so that the transparency can be controlled by controlling this moisture content. It becomes possible. As shown in FIGS. 1A and 1C, when the resin molded body 10 is in a dry state, the hydrophobic region due to the synthetic resin 4 and the hydrophilic region due to the hydrophilic fiber 3 are phase-separated. . Further, as shown in FIGS. 1B and 1D, when the hydrophilic fiber 3 is swollen, a difference in refractive index is generated at the interface between the synthetic resin 4 and the hydrophilic fiber 3.

(2) The resin molded body 10 according to another aspect of the present embodiment includes a water content of the resin molded body 10 including at least the synthetic resin 4 having at least one of an aqueous dispersion component and an aqueous emulsion component and the hydrophilic fiber 3. When the haze of the resin molded body 10 in a state where the rate reaches saturation is HZ ₁ and the haze of the resin molded body 10 in a state where the moisture content reaches equilibrium in an environment of normal temperature and normal humidity is HZ ₂ , HZ ₁ and HZ ₂ satisfy the following expressions (5) and (6).
HZ ₁ −HZ ₂ ≧ 15 (%) (5)
HZ ₂ ≦ 5 (%) (6)
With such a configuration, it is possible to repeatedly write and erase various visible information using reversible changes in transparency due to changes in moisture content.

(3) The resin molded body 10 according to another aspect of the present embodiment includes at least a synthetic resin 4 having at least one of an aqueous dispersion component and an aqueous emulsion component, and a hydrophilic fiber 3. The average fiber width is in the range of 3 nm to 200 nm.
With such a configuration, the resin molded body 10 can be used as a display material capable of repeatedly displaying and erasing information.
(4) Moreover, the hydrophilic fiber 3 contained in the resin molding 10 which concerns on this embodiment may exist in the range of 5 to 200 weight part with respect to 100 weight part synthetic resin 4. FIG.
With such a configuration, repeated display of writing and erasing of information can be ensured.

(5) The light transmittance of 660 nm when the water content of the resin molded body 10 according to the present embodiment is 8% or less may be 70% or more in terms of a film thickness of 20 nm.
With such a configuration, sufficient transparency can be imparted to the resin molded body 10.
(6) The light transmittance at 660 nm in a state where the moisture content of the resin molded body 10 according to the present embodiment has reached equilibrium in an environment having a humidity lower than normal temperature and normal humidity is 70% or more in terms of a film thickness of 20 nm. May be.
With such a configuration, sufficient transparency can be imparted to the resin molded body 10.

(7) Moreover, the average fiber width of the hydrophilic fiber 3 contained in the resin molding 10 which concerns on this embodiment may be in the range of 3 nm or more and 200 nm or less.
With such a configuration, repeated display of writing and erasing information can be made clearer.
(8) Moreover, the hydrophilic fiber 3 contained in the resin molding 10 which concerns on this embodiment may be a cellulose.
With such a configuration, repeated display of writing and erasing information can be made more reliable.

(9) The resin molded body 10 according to the present embodiment may further include one or more types of thermosetting resins.
With such a configuration, the mechanical strength of the resin molded body 10 can be increased.
(10) The resin molded body 10 according to the present embodiment may further include one or more types of photocurable resins.
With such a configuration, the mechanical strength of the resin molded body 10 can be increased.
(11) The thickness T of the resin molded body 10 according to the present embodiment may be in the range of 1 μm to 500 μm.
With such a configuration, strength and productivity can be imparted to the resin molded body 10.

(12) The synthetic resin 4 included in the resin molded body 10 according to the present embodiment aggregates to form the synthetic resin aggregate 2, and the hydrophilic fiber 3 covers the surface of the synthetic resin aggregate 2. May be arranged.
With such a configuration, it is possible to repeatedly write and erase various visible information using reversible changes in transparency due to changes in moisture content.
(13) In the method of manufacturing the resin molded body 10 according to an embodiment of the present embodiment, the above-described resin molded body 10 is formed on the support 40 by wet coating.
If it is such a structure, the resin molding 10 which can write and erase | eliminate various visible information using the reversible transparency change by the change of a moisture content can be manufactured.

(Example)
Examples of the present invention will be described below. The following examples are examples of the present invention, and the present invention is not limited to these examples.
Example 1
According to the following procedure, the composition 20 in which the synthetic resin 4 containing at least one of the aqueous dispersion and the aqueous emulsion and the hydrophilic fiber 3 were mixed and the resin molded body 10 was produced.

<Method for producing hydrophilic fiber 3>
Cellulose fibers used as the hydrophilic fibers 3 were produced.
(1) Reagents / Materials / Cellulose: Bleached Kraft Pulp (Fletcher Challenge Canada “MACHENZIE”)
・ TEMPO: Commercial product (Tokyo Chemical Industry Co., Ltd., 98%)
Sodium hypochlorite: Commercial product (Wako Pure Chemical Industries, CL: 5%)
・ Sodium bromide: Commercial product (Wako Pure Chemical Industries, Ltd.)

(2) TEMPO oxidation treatment Bleached kraft pulp having a dry weight of 10 g was allowed to stand overnight in 500 ml of ion-exchanged water in a 2 liter glass beaker to swell the pulp. To this, 0.1 g of TEMPO and 1 g of sodium bromide were added and stirred to obtain a pulp suspension. Further, 5 mmol / g sodium hypochlorite per cellulose weight was added with stirring. At this time, about 1N sodium hydroxide aqueous solution was added to maintain the pH of the pulp suspension at about 10.5.
Then, it was made to react for 2 hours, ethanol 10g was added, reaction was stopped, and the oxidized cellulose in which the carboxyl group was introduce | transduced into the cellulose was obtained. In addition, the carboxyl group introduced at this time forms a salt having a sodium ion derived from the reaction reagent remaining in the reaction medium as a counter ion. Subsequently, 0.5N hydrochloric acid was added dropwise to lower the pH to 2.
Cellulose is filtered off using a glass filter, further washed three times with 0.05N hydrochloric acid to convert the carboxyl group to carboxylic acid, then washed five times with pure water, and wet cellulose oxide with a solid content of 20%. Got. The obtained oxidized cellulose was calculated by neutralization titration with sodium hydroxide to have a carboxyl group amount of 1.6 mmol / g per dry weight of cellulose.

(3) Alkali metal treatment Water is added to the oxidized cellulose prepared as described above so as to have a solid content concentration of 5% to form a suspension, and sodium hydroxide, which is an alkali metal hydroxide, is added as an alkali species to the oxidized cellulose. 1.0 equivalent was added with respect to the amount of carboxyl groups. After stirring for 2 hours, the oxidized cellulose was filtered off using a glass filter to obtain counterion-substituted oxidized cellulose.
(4) Dispersion treatment Oxidized cellulose substituted with solvent is added to water as a dispersion medium, and treated for 1 hour using a mixer (Osaka Chemical Co., Ltd., Absolute Mill, 14,000 rpm) to achieve a solid content concentration of 0.2%. A cellulose fiber dispersion was obtained. The obtained dispersion had a light transmittance of 94% at 660 nm. Moreover, the average fiber width of the cellulose fiber at this time was 10 nm.

<Preparation of Composition 20 and Resin Molded Body 10>
(1) Preparation of composition 20 Synthetic resin 4 (manufactured by Nikka Chemical Co., Ltd., polyurethane dispersion type, neo sticker 1200) and cellulose fiber prepared by the above-described procedure are in this order in a solid content weight ratio of 100: 40. Then, the mixture was mixed overnight with a stirrer to prepare a composition 20 of synthetic resin 4 and cellulose fiber.
(2) Production of Resin Molded Body 10 The prepared composition 20 was applied to a PET film (Lumirror T60-75 μm: Toray) with an applicator, dried in an oven at 120 ° C. for 10 minutes, and then peeled off. Thus, a resin molded body 10 having a thickness of 20 μm was produced.

(Example 2)
The synthetic resin 4 and the cellulose fiber were prepared so that the weight ratio of solids was 100: 80 in this order. Otherwise, a resin molded body 10 was produced under the same conditions as in Example 1.
(Example 3)
The synthetic resin 4 and the cellulose fiber were prepared so that the weight ratio of solids was 100: 120 in this order. Otherwise, a resin molded body 10 was produced under the same conditions as in Example 1.
Example 4
A crosslinking agent having a carbodiimide group (manufactured by Nisshinbo Chemical Co., Ltd., Carbodilite V-02-L2) was prepared so that the synthetic resin 4, the cellulose fiber, and the crosslinking agent were 100: 80: 10 in this order in terms of solid content weight ratio. did. Otherwise, a resin molded body 10 was produced under the same conditions as in Example 2.

(Example 5)
A 15 wt% aqueous solution of PVA (manufactured by Kuraray Co., Ltd., PVA105), which is a thermosetting resin by a crosslinking agent, is prepared, and the synthetic resin 4, cellulose fiber, and PVA are 100: 80: 10 in this order in terms of solid content weight ratio. It was prepared as follows. Otherwise, a resin molded body 10 was produced under the same conditions as in Example 2.
(Example 6)
Synthetic resin 4, cellulose fiber, photocurable resin (manufactured by KJ Chemicals, HEAA), and photopolymerization initiator (BASF, Irgacure 500) are in this order in a solid content weight ratio of 100: 80: 10: 0.3. It prepared so that it might become. Otherwise, a resin molded body 10 was produced under the same conditions as in Example 2.
(Example 7)
The synthetic resin 4 and the cellulose fiber were prepared so that the weight ratio of solids was 100: 250 in this order. Otherwise, a resin molded body 10 was produced under the same conditions as in Example 2.

(Comparative Example 1)
A resin molded body 10 was produced under the same conditions as in Example 2 except that the same weight of water was used instead of the cellulose fibers.
(Comparative Example 2)
A resin molded body 10 was produced under the same conditions as in Example 2 except that the same weight of water was used instead of the synthetic resin 4.
(Comparative Example 3)
In the production of cellulose fibers, the dispersion treatment time using a mixer was 10 minutes. Otherwise, a resin molded body 10 was produced under the same conditions as in Example 2. Moreover, the average fiber width of the cellulose fiber at this time was 500 nm.

[Evaluation]
With respect to Examples 1 to 7 and Comparative Examples 1 to 3, the production conditions are shown in Table 1 described later, and the evaluation results are shown in Table 2.
[Measurement of cellulose fiber width]
After diluting with water so that the cellulose fiber was 0.001 wt%, it was developed on mica and allowed to dry naturally, and then the sample was observed with a transmission electron microscope. 100 samples were taken at random and the average value was determined as the average fiber width (nm).

[Haze of Resin Molded Body 10]
About the obtained resin molding 10, after immersing in water for 1 minute, the water | moisture content of the surface was wiped off, and immediately after forming the resin molding 10, the haze was measured about the surface on the opposite side to PET. The value of this time was the HZ _1. Furthermore, after the sample immersed in water was dried in an oven at 60 ° C. for 30 minutes and then conditioned for 2 days in a thermostatic chamber at 23 ° C. and 50% RH, the haze was measured in the same manner. The value of this time was the HZ _2.
[Light transmittance of resin molded body 10]
The resin molded body 10, in the same conditions as the haze was measured HZ _2, UV-VIS spectrophotometer (manufactured by Shimadzu Corporation, UV3600) was measured for light transmittance (%) at a wavelength of 660nm using a .

[Visibility]
For the resin molded body 10 under the same conditions as the measurement of haze HZ ₂ , writing was performed on the resin molded body 10 using a writing instrument that can retain moisture, and sensory evaluation was performed to determine whether the resin molded body 10 could be visually confirmed. . Note that “◎” indicates that the visibility was extremely high, “○” indicates that the visibility was high, “△” indicates that the visibility was high enough to be used, and “×” indicates that the visibility was low. As evaluated.
[Repeated durability]
The visibility when the resin molded body 10 was dipped in water for 1 minute and dried in a 60 ° C. oven for 30 minutes 100 times was visually evaluated. As in the case of the visibility evaluation described above, “◎” indicates that the visibility is extremely high, “○” indicates that the visibility is high, and “△” indicates that the visibility is high enough to be used. Those with low visibility were evaluated as “x”.

From the results in Table 2, the aqueous dispersion as the synthetic resin 4 and the cellulose fiber as the hydrophilic fiber 3 have a composition ratio within a certain range (if it is Example 1 to Example 7), moisture absorption and release. It can be seen that the transparency and cloudiness opacity can be controlled by humidity. By utilizing this, a display material capable of repeatedly controlling writing and erasing of information only with moisture can be manufactured. On the other hand, when there is too much synthetic resin 4 (in the case of Comparative Example 1) or when there are too few hydrophilic fibers 3 (in the case of Comparative Example 2), the size of the region of the hydrophobic portion by the synthetic resin 4 or the hydrophilic fibers 3 The amount of water taken in cannot be sufficiently controlled in the expression of cloudiness and opacity, and visibility is lowered.
Moreover, as shown in Examples 2 to 4, if the resin molded body 10 contains substantially equal amounts of the hydrophilic fiber 3 and the cellulose fiber, the visibility is further enhanced and the light transmittance is also high. I understand that.

  According to the resin molded body of the present invention, it is possible to easily and inexpensively produce a display material capable of repeatedly writing and erasing various visible information using reversible transparency change due to change in moisture content. .

DESCRIPTION OF SYMBOLS 1 ... Resin unit 2 ... Synthetic resin aggregate 3 ... Hydrophilic fiber 4 ... Synthetic resin 10 ... Resin molded object 20 ... Composition 30 ... Bar coater 40 ... Support body T ... Thickness

Claims (13)

A synthetic resin having at least one of an aqueous dispersion component and an aqueous emulsion component, and at least hydrophilic fibers,
The average fiber width of the hydrophilic fibers is in the range of 3 nm to 200 nm,
Content of the said hydrophilic fiber exists in the range of 5 to 200 weight part with respect to 100 weight part of said synthetic resins, The resin molding characterized by the above-mentioned. A synthetic resin having at least one of an aqueous dispersion component and an aqueous emulsion component, and at least hydrophilic fibers,
The haze of the resin molded body having a moisture content of 25% or more is HZ ₁ ;
When the haze of the resin molded product having a moisture content of 8% or less is HZ ₂ , HZ ₁ and HZ ₂ satisfy the following formulas (1) and (2).
HZ ₁ −HZ ₂ ≧ 15 (%) (1)
HZ ₂ ≦ 5 (%) (2) A synthetic resin having at least one of an aqueous dispersion component and an aqueous emulsion component, and at least hydrophilic fibers,
The haze of the resin molded body in a state where the water content of the resin molded body reaches saturation is HZ ₁ .
When the haze of the resin molded product in a state where the water content has reached equilibrium in an environment of normal temperature and humidity is HZ ₂ , HZ ₁ and HZ ₂ satisfy the following formulas (1) and (2): A resin molded product characterized by that.
HZ ₁ −HZ ₂ ≧ 15 (%) (1)
HZ ₂ ≦ 5 (%) (2)   The resin molded product according to claim 2, wherein the light transmittance at 660 nm when the water content is 8% or less is 70% or more in terms of a film thickness of 20 nm.   4. The resin according to claim 3, wherein the light transmittance at 660 nm is 70% or more in terms of a film thickness of 20 nm in a state where the water content has reached equilibrium in an environment of humidity lower than room temperature and normal humidity. Molded body.   6. The resin molded body according to claim 2, wherein an average fiber width of the hydrophilic fibers is in a range of 3 nm to 200 nm.   The content of the hydrophilic fiber is in a range of 5 parts by weight or more and 200 parts by weight or less with respect to 100 parts by weight of the synthetic resin. Resin molded body.   The resin molding according to claim 1, wherein the hydrophilic fiber is cellulose.   The resin molded body according to any one of claims 1 to 8, further comprising one or more types of thermosetting resins.   The resin molded body according to any one of claims 1 to 9, further comprising one or more kinds of photocurable resins.   The thickness of the said resin molding is in the range of 1 micrometer or more and 500 micrometers or less, The resin molding of any one of Claims 1-10 characterized by the above-mentioned. The synthetic resin aggregates to form a synthetic resin aggregate,
The said hydrophilic fiber is arrange | positioned so that the surface of the said synthetic resin aggregate may be covered, The resin molding of any one of Claims 1-11 characterized by the above-mentioned.   A method for producing a resin molded product, comprising forming the resin molded product according to any one of claims 1 to 12 on a support by wet coating.

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