JP6915261B2 - Resin molded body and manufacturing method of resin molded body - Google Patents

Description

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

In recent years, many display materials capable of repeatedly displaying information by writing and erasing have been developed, and heat, magnetism, and light are mainly used as the display method. Such a display material is precisely designed by, for example, controlling the crystallinity of the small molecule material, the orientation of the liquid crystal material, and the molecular skeleton. Further, such a display material is often displayed on a card, and is widely used for point cards, ID cards, and the like. However, a dedicated device is required to utilize these. Therefore, there is a demand for a display material that can be used by a simpler method, is inexpensive, and has high visibility.

In recent years, the use of environment-friendly materials (biomass materials) has been attracting attention against the background of global warming due to resource depletion and an increase in the concentration of carbon dioxide in the atmosphere, environmental pollution, and waste problems. This biomass material has the characteristics that the amount of fossil resources used during production is small, it can be processed with low energy at the time of disposal, and carbon dioxide emissions are small. Cellulose, which accounts for about half of the production of biomass materials, is expected to be effectively used due to its large production. Furthermore, cellulose has high strength, high elastic modulus, and extremely low coefficient of thermal expansion, and has no glass transition point in terms of 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 amount. 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) glucosidic bonded, and has hydroxyl groups at the C2, C3, and C6 positions. Therefore, strong hydrogen bonds are formed in the molecule and between the molecules, and they are insoluble in water and general solvents.

However, when cellulose is treated using an oxidation reaction catalyzed by an N-oxyl compound such as 2,2,6,6-tetramethyl-1-piperidinyloxy radical (TEMPO) to adjust the degree of treatment. A homogeneous dispersion can be obtained by a light dispersion treatment in water. At this time, cellulose is defibrated to the microfibril level and exists as a cellulose fiber dispersion having a fiber width of several nm to several hundred nm. Further, this TEMPO oxidation reaction uses only water as a reaction medium without using an organic solvent, and the reaction is completed in a short time under mild conditions at normal temperature and pressure, and the environmental adaptability of the reaction process is extremely high.

The mechanism by which the oxidized cellulose obtained by the TEMPO oxidation reaction is dispersed to the nano level by a light mechanical treatment is known as follows. First, the hydroxyl group at the C6 position on the surface of the microfibrils of cellulose is selectively oxidized by the oxidation reaction, and the carboxyl group is introduced via the aldehyde group. Then, this carboxyl group is charged and repelled as an anion, and exhibits an osmotic effect in the dispersion medium. Therefore, nano-order microfibrils are easily isolated, and a homogeneous cellulose fiber dispersion can be obtained.
Furthermore, by utilizing the electrostatic action of the carboxyl group introduced into cellulose to form various salts having cations as counterions, cellulose modified products having different characteristics can be obtained. Since this treatment can retain the crystallinity of the raw material cellulose without destroying it, it has high physical characteristics.

As described above, cellulose that can be used as a nano-dispersion, a liquid state, or a modified product has a low environmental load and has high physical characteristics. Therefore, the treatment by the TEMPO oxidation reaction and the oxide are new uses of cellulose. Expected as a form.
One example of active development for industrial use is compounding with resin. By mixing a cellulose dispersion in the resin, the purpose is to enhance the functionality of the resin by utilizing the light weight, high strength, high elastic modulus, low coefficient of linear thermal expansion, and high heat resistance of cellulose.
As an important factor for improving the functionality at this time, the dispersibility of the cellulose fibers in the resin is mentioned. 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 enhance the affinity with the hydrophobic resin and improve the dispersibility, a method of forming a composite using an aqueous emulsion as the 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. Therefore, thickening when mixed with cellulose fibers can be suppressed, and handling becomes easy. On the other hand, the mixture of cellulose fiber and aqueous emulsion has a low solid content concentration and uses water having a high boiling point as a dispersion medium. Therefore, a large amount of energy and time are required to remove the dispersion medium. As a result, the productivity of materials using cellulose was generally low.

As a technique for improving the productivity of a material 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 a cellulose fiber is gelled using a cellulose coagulant, filtered on a porous substrate, and then dried.

Japanese Patent No. 5747818

As described above, although some techniques for improving the productivity of materials using cellulose have been disclosed so far, cellulose is used as a display material capable of repeatedly displaying information by writing and erasing it. No technology was disclosed.
The present invention provides a resin molded product and a manufacturing method thereof, which have a simple manufacturing process and a display method, and can be repeatedly displayed by writing and erasing information.
The resin molded product referred to here refers to various forms such as a film-like, a sheet-like, and a structure formed by using a composition obtained by mixing a synthetic resin having an aqueous dispersion or an aqueous emulsion and a hydrophilic fiber. Point to. The composition is a mixture of a synthetic resin and hydrophilic fibers, and refers to a state before structure formation or reaction by heating or light.

In order to solve the above problems, the resin molded product according to one aspect of the present invention contains at least a synthetic resin having at least one of an aqueous dispersion component and an aqueous emulsion component and hydrophilic fibers, and the hydrophilic fibers. The average fiber width is in the range of 3 nm or more and 200 nm or less, and the content of the hydrophilic fiber is in the 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. The resin molded body according to another embodiment contains at least a synthetic resin having at least one of an aqueous dispersion component and an aqueous emulsion component and hydrophilic fibers, and the resin molded body has a water content of 25% or more. When the haze of the molded body is HZ ₁ and the haze of the resin molded body having a water content of 8% or less is HZ ₂ , HZ ₁ and HZ ₂ satisfy the following equations (1) and (2).
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 product used as a display material capable of repeatedly displaying information by writing and erasing information, and a method for producing the same, because the manufacturing process and the display method are simple.

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

Hereinafter, the resin molded product and the manufacturing method thereof according to the embodiment of the present invention will be described with reference to the drawings. Here, the drawings are schematic, and the relationship between the thickness and the plane dimensions, the ratio of the thickness of each layer, and the like are different from the actual ones. Further, the embodiments shown below exemplify a configuration for embodying the technical idea of the present invention, and the technical idea of the present invention describes the material, shape, structure, etc. of the constituent parts as follows. It is not specific to the thing. The technical idea of the present invention may be modified in various ways within the technical scope specified by the claims stated in the claims.

(Structure of Resin Mold 10)
FIG. 1 is a diagram schematically showing a part of a resin molded product according to an embodiment of the present invention. More specifically, FIG. 1A is a diagram showing the appearance of a resin molded body in a dry state (normal temperature and humidity), and FIG. 1B is a diagram showing resin molding in a wet state (moisture content is saturated). It is a figure which shows the appearance of a body. Further, FIG. 1 (c) is a diagram showing a cross section of the resin molded product in a dry state (normal temperature and humidity), and FIG. 1 (d) is a diagram of the resin molded product in a wet state (moisture content is saturated). It is a figure which shows the cross section. The shaded areas shown in FIGS. 1 (c) and 1 (d) are cross sections.

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. Then, each resin unit 1 contains at least a synthetic resin agglomerate 2 and a hydrophilic fiber 3 existing so as to cover the surface of the synthetic resin agglomerate 2. Further, as shown in FIG. 1, the synthetic resin agglomerate 2 is formed by aggregating several to several tens of synthetic resin 4. In other words, the resin molded body 10 according to the present embodiment includes a synthetic resin agglomerate 2 formed by aggregating the synthetic resin 4 and a hydrophilic fiber 3 formed so as to cover the surface of the synthetic resin agglomerate 2. The resin unit 1 including the above is provided. The above-mentioned "normal temperature and humidity" means "23 ° C. and 50% RH", and the "normal temperature and humidity environment" means "an environment of 23 ° C. and 50% RH".

Hereinafter, the details of the synthetic resin 4 and the hydrophilic fiber 3 described above will be described.
<Synthetic resin 4>
The resin molded product 10 according to the present embodiment contains 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 may be 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 the present embodiment. Further, as an expression paired with the hydrophilic fiber 3, the expression synthetic resin 4 is used as a general term for the resin of the aqueous dispersion and the aqueous emulsion.
In this aqueous dispersion or aqueous emulsion, water is used as the main dispersion medium, and the polymer is dispersed in 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 a higher degree of freedom in design than water-soluble monomers and water-soluble oligomers as resins, and therefore have the advantage that materials can be selected according to the desired performance and function. Further, although dispersion stability in the dispersion medium is imparted by adding an emulsifier or introducing a hydrophilic group into the resin, the synthetic resin 4 itself is hydrophobic and has high water resistance and moisture resistance. .. Therefore, it is not easily affected by the external humidity environment, and there is no significant deformation even when the water content of the resin molded body 10 is changed, and the structure of the resin molded body 10 can be maintained.
Further, in the aqueous dispersion and the aqueous emulsion, the degree of polymerization of the synthetic resin 4 is high, but the viscosity of the coating liquid is low because the synthetic resin 4 individually forms independent fine particles. Therefore, good mixing properties can be obtained even if the hydrophilic fiber 3 which is the constituent material of the present embodiment has a high viscosity.

As described above, the aqueous dispersion and the aqueous emulsion in the present embodiment are dispersed as resin particles in the aqueous dispersion medium containing water. The resin particles have a certain distribution in particle size. During the liquid coating stage before molding or during molding of the resin molded body 10, the interaction with the hydrophilic fibers 3 to be mixed and other components, the melting temperature, and the like affect the aggregated form of the resin particles at the time of deformation and fusion. Therefore, the particle size 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 product 10. However, if the particle size of the synthetic resin 4 is too small, the specific surface area of the synthetic resin 4 is large, so that the interaction with the hydrophilic fibers 3 and other components mixed by the electrical action of the surface of the resin particles tends to be large, and the synthetic resin 4 is synthesized. Fusion of the resins 4 is less likely to occur. As a result, the size of the hydrophobic region made of the synthetic resin 4 becomes smaller. In this case, since there are many interfaces between the hydrophobic region and the hydrophilic region, scattering occurs at the interface of light regardless of the water content, and the haze of the resin molded product 10 increases. On the other hand, if the particle size 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 size of the aqueous dispersion or the aqueous emulsion is preferably in the range of 0.01 μm or more and 10 μm or less, which is an appropriate size suitable for the purpose of the present embodiment.

In addition, aqueous dispersions and aqueous emulsions are roughly classified into anionic, cationic and nonionic according to ionicity. In the present embodiment, the use of any of them is not limited, but when the hydrophilic fiber 3 to be mixed is anionic, mixing the cationic synthetic resin 4 may inhibit the charge thereof, and thus is anionic or nonionic. Is preferable.
As the synthetic resin 4 composed of an aqueous dispersion or an aqueous emulsion, for example, vinyl acetate-based, urethane-based, acrylic-based, styrene-based, phenol-based, amino-based, amide-based, polyester-based, ethylene-based, and polyvinyl alcohol-based are used. .. In addition, these may be used alone, copolymerized, or used in combination of two or more. Further, the reactive synthetic resin 4 may be used. In that case, for example, a curing agent, a curing catalyst, a photopolymerization initiator, a chain transfer agent, or 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, it is preferable that the synthetic resin 4 has flexibility, and the urethane type is used. More preferred. As for urethane type, polyester type, polyether type, polycarbonate type and the like have been developed depending on the type of polyol constituting the urethane structure, and any of them can be used.

<Hydrophilic fiber 3>
The main role of the hydrophilic fiber 3 used in the present embodiment is that the swelling rate due to water content differs from that of the hydrophobic region of the synthetic resin 4 composed of an aqueous dispersion or an aqueous emulsion, so that incident light is emitted on the interface between the hydrophobic regions. It is to cause scattering. Another role is to adjust the aggregation size of the particles of the synthetic resin 4 and to sufficiently bind the aggregation interfaces of the synthetic resin 4 to each other by having an appropriate interaction with the synthetic resin 4. .. Further, if the fiber width of the hydrophilic fiber 3 is too large, scattering occurs at the interface of light 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 at least the swelling rate in water, ionicity, strength, and fiber width of the present embodiment.

As the hydrophilic fiber 3 satisfying the above requirements, for example, a cellulose fiber obtained by oxidizing cellulose by a TEMPO oxidation reaction and then performing a mechanical treatment to defibrate the fiber width to the nano level can be preferably used. By TEMPO-oxidizing cellulose, the hydroxyl group at the C6 position on the surface of the microfibrils of cellulose is selectively oxidized, and a carboxyl group is introduced via an aldehyde group. The charge repulsion of this carboxyl group enables defibration up to the nano level. In addition, since cellulose maintains type I crystals and there is almost no decrease in crystallinity, the original high elastic modulus of cellulose can be maintained. Further, 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 molded body. It is possible to adjust the amount of charge derived from the carboxyl group. In addition, cellulose has three hydroxyl groups per glucose unit, and since it has a structure in which a large number of hydroxyl groups are exposed on the surface of microfibrils by being defibrated to the nano level, it has high hydrophilicity, and therefore it becomes water. The swelling rate of is extremely high.

The cellulose fibers used in the present embodiment preferably have an average fiber width of 3 nm or more and 200 nm or less. If the fiber width is wider than 200 nm, the fiber width approaches the wavelength of visible light, which causes the transparency of the resin molded body 10 to decrease, and the surface area and the entanglement of the fibers to decrease. Causes a decline. Further, in the fiber having a fiber width of less than 3 nm, it is difficult to produce a fiber having excellent mechanical strength and uniformity, so that the fiber width is preferably 3 nm or more. Further, the longer the fiber length, the more easily the fibers are entangled with each other, so that the effect is likely to be exhibited at a low content. However, if it is too long, the energy required for dispersion and formation increases and dispersion becomes difficult. Therefore, the fiber length is preferably 10 nm or more and 10000 nm or less.

The measuring method is not particularly limited with respect to the fiber width of the cellulose fiber used in the present embodiment, but it can be measured by, for example, the following method. Cellulose fibers 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 are developed on mica and air-dried. After that, the fiber width of the cellulose fiber can be confirmed (measured) by observing the cellulose fiber with a transmission electron microscope. In some cases, the composition 20 may be diluted with a good solvent, developed into mica, and then dried and cured.
Further, the method for measuring the fiber width of the cellulose fibers in the resin molded body 10 using a method other than a transmission electron microscope is, for example, a method using an atomic force microscope. 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 the characteristics of the cellulose fiber and the synthetic resin. Therefore, the cellulose fiber is detected from the phase shift and the width is measured. can do.

As the material using the cellulose used in the present embodiment as a starting material, for example, natural cellulose or chemically modified cellulose can be used. Specifically, wood-based pulp such as bleached and unbleached kraft wood pulp, pre-hydrogenated kraft wood pulp, sulfite wood pulp, non-wood pulp such as cotton and bacterial cellulose, and mixtures thereof shall be used. Can be done. Further, any substance obtained by physically or chemically treating these may be used. Preferably, natural cellulose having a crystalline form I is desirable because it has high material properties such as mechanical properties, thermal properties, and chemical resistance.

As the cellulose used in the present embodiment, for example, one in which a part of the hydroxyl groups of the cellulose is replaced with a carboxyl group is used. The method for introducing a carboxyl group into cellulose as a raw material is not particularly limited, and is appropriately selected depending on the intended purpose. For example, it can be appropriately selected from a generally known method of oxidizing a hydroxyl group to a carboxylic acid via an aldehyde. Among them, a method using an N-oxyl compound as a catalyst and a hypohalogenate, a subhalogenate or the like as an oxidizer 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 a bromide such as sodium bromide are used while adjusting the pH. The TEMPO oxidation method treated with the above is suitable from the viewpoints that the reaction is completely in water without using an organic solvent as a reaction medium, the availability of reagents, the cost, and the stability of the reaction.
In this TEMPO oxidation method, only the surface of the crystalline cellulose microfibrils is oxidized, and the inside of the crystal is not oxidized, so that the crystal structure can be maintained. Therefore, the product has the characteristics of high strength, high elastic modulus, low coefficient of linear thermal expansion, and high heat resistance inherent in cellulose.

(Oxidation treatment by TEMPO oxidation method)
In this embodiment, the oxidation treatment by the above-mentioned TEMPO oxidation method was carried out by the following procedure.
An N-oxyl compound and an oxidizing agent or a copolymer are added to the cellulose dispersed in water to oxidize the cellulose. 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 can be thoroughly washed with water and recovered, and used as the constituent material (hydrophilic fiber 3) in the present embodiment.

As the oxidizing agent, for example, hypochlorous acid or a salt thereof, hypochlorous acid or a salt thereof can be used, and sodium hypochlorite is preferable. Examples of the copolymerizer include lithium bromide, potassium bromide, sodium bromide, and the like, but sodium bromide is preferable because of its ease of handling.
The content of the carboxyl group introduced into the cellulose can be adjusted by appropriately setting the reaction conditions. Cellulose into which a carboxyl group has been introduced is dispersed in a dispersion medium due to charge repulsion of the carboxyl group through a dispersion step described later. Therefore, if the content of the carboxyl group in the cellulose is too small, the cellulose is stably dispersed in the dispersion medium. I can't let you. Further, if the content of the carboxyl group in the cellulose is too large, the affinity for the dispersion medium is increased and the water resistance is lowered.

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. Further, it is more preferably in the range of 0.8 mmol or more and 2.5 mmol or less.
The amount of carboxyl groups contained in cellulose is calculated by, for example, the following method. Take 0.2 g of the oxidized cellulose in terms of dry weight in a beaker and add 80 ml of ion-exchanged water. 5 ml of a 0.01 M sodium chloride aqueous solution is added thereto, and 0.1 M hydrochloric acid is added while stirring to adjust the pH to 2.0 as a whole.

Using an automatic titrator (AUT-701 manufactured by DKK-TOA CORPORATION), a 0.1 M aqueous sodium hydroxide solution was injected at 0.05 ml / 30 seconds, and the conductivity and pH value were measured every 30 seconds to measure pH11. Continue measurement until. The carboxyl group content can be calculated by obtaining the titration amount of sodium hydroxide from the obtained conductivity curve.
After stopping the oxidation reaction, the product is collected 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 for separating the carboxyl groups while forming a salt,
(B) A method of adding an acid to the reaction solution to adjust the inside of the system under acidic conditions and filtering it as a carboxylic acid.
(C) Examples thereof include a method in which an organic solvent is added to aggregate the sol, and then the sol is separated.
Among them, the method of recovering as (B) carboxylic acid is preferable from the viewpoint of handleability, recovery efficiency, and waste liquid treatment. Further, when a metal ion is not contained as a counter ion, the formation of a by-product can be suppressed and the substitution efficiency is excellent. Therefore, the method of recovering as (B) carboxylic acid is preferable.

The metal ion content in cellulose after the oxidation reaction can be examined by various analytical methods. For example, it is simply examined by elemental analysis of EPMA method and fluorescent X-ray analysis method using an electron probe microanalyzer. be able to. When recovered by the method of (A) filtering while forming a salt, the content of metal ions is 5 wt% or more, whereas when recovered by the method of (B) filtering as carboxylic acid, 1 wt. It will be less than%.
Further, the recovered cellulose can be purified by repeating washing, and the catalyst and by-products can be removed. At this time, the amount of residual metal ions and salts can be reduced by repeating the washing with a washing liquid prepared under acidic conditions of pH 3 or less using hydrochloric acid or the like and then repeating the washing with pure water.

By adding a hydroxide containing an alkali metal or an alkaline earth metal to a suspension of cellulose having a carboxyl group introduced, a part or all of the carboxyl groups becomes an alkali metal salt type or an alkaline earth metal salt type. Will be replaced. Due to the charge of the carboxyl group, cellulose exhibits an osmotic effect in the dispersion medium and can be dispersed to the nano-order. The amount of hydroxide added to the alkali metal or alkaline earth metal is preferably in 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, when the amount is in the range of 1 equivalent or more and 1.8 equivalents or less, counter ion exchange can be performed without adding an excessive amount of alkali metal or alkaline earth metal hydroxide, which is more preferable. It is also possible to remove the excess amount of alkali metal or alkaline earth metal hydroxide by washing the cellulose with water again after adding an excess amount of alkali metal or alkaline earth metal hydroxide. By removing the excess alkali, it becomes possible to suppress the deterioration of the material 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 resin molded body 10)
Hereinafter, a method for producing the resin molded product 10 according to the present embodiment will be described. FIG. 2 is a diagram schematically showing a manufacturing process of the resin molded product 10 according to the present embodiment.
The resin molded product 10 in the present embodiment is formed of 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, by dispersing the hydrophilic fibers 3 in advance with water or an aqueous solvent, the mixability with the synthetic resin 4 can be improved. The undispersed hydrophilic fiber 3 may be dispersed in the synthetic resin 4 for the purpose of not reducing the solid content concentration of the coating liquid in the wet coating. As a dispersion treatment method, various already known dispersion treatments are possible when there is no problem in the dispersibility of the resin particles of the aqueous dispersion or the aqueous emulsion in the dispersion medium and the subsequent formation of the resin molded product 10. Is. For example, homomixer processing, mixer processing with rotary blade, high pressure homogenizer processing, ultrahigh pressure homogenizer processing, ultrasonic homogenizer processing, nanogenizer processing, disc type refiner processing, conical type refiner processing, double disc type refiner processing, grinding processing, ball mill processing. , Kneading process with a twin-screw kneader, underwater facing process, etc. Among these, a mixer treatment with a rotary blade, a high-pressure homogenizer treatment, an ultra-high pressure homogenizer treatment, and an ultrasonic homogenizer treatment are preferable from the viewpoint of miniaturization efficiency. Of these processes, it is also possible to perform dispersion by combining two or more processing methods.

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. If it is less than 5 parts by weight, swelling due to water content of the hydrophilic fibers 3 in the resin molded product 10 is unlikely to occur, and as a result, cloudiness and opacity may decrease. Further, when the amount exceeds 200 parts by weight, the hydrophobic region formed by the synthetic resin 4 is dispersed in the matrix of the hydrophilic fibers 3, making it difficult to control the water content of the resin molded product 10 itself, and the interface of the hydrophobic region becomes difficult. Since it decreases relatively, it may result in a decrease in cloudiness and opacity.

The method for forming the resin molded product 10 using the composition 20 obtained by mixing the synthetic resin 4 and the hydrophilic fibers 3 prepared in this manner is not particularly limited, but the composition 20 has fluidity. Therefore, the resin molded product 10 can be obtained by wet-coating and curing the support 40 on a resin base material or a glass base material.
A known method can be used as the coating method. Specifically, bar coating method, dip coating method, spin coating method, flow coating method, spray coating method, roll coating method, gravure roll coating method, air doctor coating method, plaid coating method, wire doctor coating method, knife coating. A method, a reverse coating method, a transfer roll coating method, a microgravure coating method, a kiss coating method, a cast coating method, a slot orifice coating method, a calendar coating method, a die coating method and the like can be used.

Note that FIG. 2A schematically shows how the composition 20 is wet-coated on the support 40 using the bar coater 30.
The base material may be pretreated for the purpose of improving the wettability and adhesion of the base material to which the composition 20 in which the synthetic resin 4 and the hydrophilic fiber 3 are mixed is applied. The pretreatment method is not particularly limited, and for example, an anchor layer may be formed in advance, or corona treatment, plasma treatment, frame treatment, or the like may be performed.
The resin molded product 10 can be formed by drying the composition 20 coated on the support 40, that is, removing the excess dispersion medium in the system. Further, after the resin molded body 10 is manufactured, the resin molded body 10 may be additionally heated for the purpose of advancing the reaction of the resin and improving other characteristics. When a photoreactive material is used, the resin molded body 10 may be irradiated with light having a wavelength at which the reaction proceeds.
The resin molded body 10 thus formed is shown in FIG. 2 (b).

The thickness T of the resin molded product 10 obtained in the present embodiment is preferably in the range of 1 μm or more and 500 μm or less, and particularly preferably in the range of 10 μm or more and 200 μm or less. If the thickness T is less than 1 μm, the strength of the resin molded product 10 becomes extremely weak, which makes it unsuitable for production. On the other hand, if it exceeds 500 μm, the drying speed takes a very long time, the productivity is extremely lowered, and excess water remains inside the resin molded product 10, which is not preferable.
The light transmittance at 660 nm when converted to a thickness of 20 mm of the obtained resin molded product 10 is preferably 70% or more in a dry state of the resin molded product 10. Further, 80% or more is particularly preferable. The resin molded product 10 according to the present embodiment utilizes the reversibility of transparency due to the water content, and in the transparent state, at least visually enhances the transparency, thereby improving the visibility by contrast with the cloudy opaque state. can do. Here, the "state in which the resin molded body 10 is dried" means a state in which the water content of the resin molded body 10 is 8% or less. Alternatively, it refers to a state in which the water content of the resin molded product 10 has reached equilibrium in an environment of humidity lower than normal temperature and humidity.

As the support 40 forming the resin molded body 10, for the purpose of improving visibility or the like, a layer having a metallic luster or a layer having various colors may be laminated. These layers having metallic luster and layers having 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 forming the resin molded body 10, a moisturizing layer having a moisturizing property may be laminated in order to control the water absorption rate and the transparency. The moisturizer constituting the moisturizing layer is not particularly limited, and for example, cellulose, cellulose derivative, chitin, chitosan derivative, starch, hyaluronic acid, alginic acid, gelatin, kaolin, dextrin, glycerin, polyglycerin, D-sorbitol, PVA and the like. Glycerin and sorbitol are particularly preferable. Further, only one type of moisturizer may be used for the moisturizing layer, 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 product 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 at the same time. Further, since it is possible to selectively advance the curing of the resin by irradiating the resin molded body 10 with active energy rays such as ultraviolet rays and electron beams, a photocurable resin may be further added. .. A heating step may be added in the process of the curing reaction for the purpose of removing the solvent and improving the reactivity.

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 enhanced, or the binding property of the resin molded body 10 can be enhanced. Adjustments can be made according to various purposes, such as controlling the mechanical properties and the water absorption rate of the hydrophilic fiber 3.
Further, 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. Examples of the cross-linking agent that forms a cross-linked structure by heating include, but are not limited to, oxazoline, divinyl sulfone, carbodiimide, dihydrazine, dihydrazide, epichlorohydrin, glioxal, organic titanium compound, and organic zirconium compound. It is also possible to mix and use two or more of them. Of these, carbodiimide is preferable because it can efficiently form a crosslinked structure without applying a large amount of energy.

Further, when the resin molded body 10 is irradiated with active energy rays such as ultraviolet rays or electron beams to promote the curing of the resin, a photocrosslinking agent, a photopolymerization initiator or the like may be used. These types are not particularly limited, and examples thereof include an acetophenone-based photopolymerization initiator, a benzoin-based photopolymerization initiator, a benzophenone-based photopolymerization initiator, a thioxanthone-based photopolymerization initiator, and a thioxanthone-based photopolymerization initiator. can.
Further, a function to be added for the purpose of adjusting the viscosity, adjusting the drying rate, improving the affinity with different materials, etc. within the range where 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 such as water can be mixed.

At this time, in order to alleviate the shock caused by mixing different solvents, for example, the addition rate, pH adjustment, stirring method, temperature and the like can be appropriately selected.
Further, the resin molded body 10 may contain a metal or the like. Examples of the metal contained in the resin molded body 10 include platinum group elements of gold, silver, platinum, palladium, ruthenium, iridium, rhodium, and osmium, as well as iron, lead, copper, chromium, cobalt, nickel, manganese, and vanadium. , Metals such as molybdenum, gallium, aluminum or alloys thereof, or oxides, compound 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 complex of metal or metal oxide, and a reducing agent is added to the 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 exerted by a small amount of metal.
In the range where aggregation and precipitation do not occur, various additives including water-soluble polysaccharides and various resins may be contained for the purpose of further 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 contained in order to impart functionality such as coatability and wettability. For example, alcohols, cellsolves, glycols and the like can be included. Further, various dyes, pigments, organic fillers, inorganic fillers and the like may be contained for the purpose of imparting design. Further, the pH can be adjusted by adding an acid or an alkali for the purpose of improving the reactivity.

Regarding the control of the transparency of the resin molded product 10 according to the present embodiment, the water content of the resin molded product 10 can be used as an index. The water content of the resin molded product 10 can be changed, for example, by immersing the resin molded product 10 in a dry state in water. When the surface haze when the water content of the resin molded body 10 reaches saturation by being sufficiently immersed in water is set to HZ _1, and this is released to show the water content in an equilibrium state with normal temperature and humidity. When the haze of HZ is HZ ₂ , _{it is preferable to satisfy HZ 1 − HZ 2} ≧ 15 (%). In order to ensure visibility, it is preferable to have a difference of 15% or more as haze due to a change in water content, and more preferably to have a difference of 30% or more. _{Further, by setting HZ 2} ≤ 5 (%) as the haze of the resin molded body 10, it can be widely used as the resin molded body 10 having transparency at normal temperature and humidity. In other words, when the haze when the water content of the resin molded body 10 is 25% or more is HZ _1, and the haze when the water 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 product 10 according to the uniform state of the present embodiment contains 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 contains water in the resin molded product 10. When the haze of the resin molded product 10 at a rate of 25% or more is HZ _1, and the haze of the resin molded product 10 at a water content of 8% or less is HZ ₂ , HZ ₁ and HZ ₂ are The following equations (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 visible information by utilizing the reversible change in transparency due to the change in water content.

More specifically, in such a configuration, the transparency is reversibly changed from the transparent state to the cloudy opaque state only by the change of the water content. The difference between this transparent state and the cloudy opaque state is presumed as follows. That is, in the transparent state (that is, when the resin molded product 10 is in a dry state), the hydrophobic region of the synthetic resin 4 containing at least one of the aqueous dispersion component and the aqueous emulsion component and the hydrophilic fiber 3 are formed. It is distributed phase-separated from the hydrophilic region. Here, since the refractive index of the synthetic resin 4 and the hydrophilic fiber 3 are close to each other and the fiber width of the hydrophilic fiber 3 is smaller than the wavelength of visible light, the light incident from one side is transmitted to the other side without being scattered. It looks transparent because it does. On the other hand, in the case of a cloudy opaque state (that is, when the resin molded body 10 is in a damp state), the hydrophilic fibers 3 swell and have a refractive index at the interface between the particles of the synthetic resin 4 and the hydrophilic fibers 3. It is derived from the fact that there is a difference and it looks cloudy because it is refracted and scattered many times at the interface. Since it is only the amount of water taken up by the hydrophilic fiber 3, that is, the water content of the hydrophilic fiber 3 that controls the swelling behavior of the hydrophilic fiber 3, the transparency can be controlled by controlling this water content. It will be possible. As shown in FIGS. 1A and 1C, when the resin molded product 10 is dry, the hydrophobic region formed by the synthetic resin 4 and the hydrophilic region formed by the hydrophilic fiber 3 are phase-separated. .. Further, as shown in FIGS. 1 (b) and 1 (d), in a state where the hydrophilic fibers 3 are swollen, a difference in refractive index occurs at the interface between the synthetic resin 4 and the hydrophilic fibers 3.

(2) The resin molded product 10 according to another aspect of the present embodiment is a water-containing resin molded product 10 containing at least one of a synthetic resin 4 having an aqueous dispersion component and an aqueous emulsion component and a hydrophilic fiber 3. When the haze of the resin molded product 10 when the ratio reaches saturation is HZ _1, and the haze of the resin molded product 10 when the water content reaches equilibrium in an environment of normal temperature and humidity is HZ _2. , HZ ₁ and HZ ₂ satisfy the following equations (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 by utilizing the reversible change in transparency due to the change in water content.

(3) The resin molded product 10 according to another aspect of the present embodiment contains 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 is a hydrophilic fiber 3. The average fiber width is in the range of 3 nm or more and 200 nm or less.
With such a configuration, the resin molded body 10 can be used as a display material capable of repeatedly displaying information written and erased.
(4) Further, the hydrophilic fiber 3 contained in the resin molded product 10 according to the present embodiment may be in the 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 4.
With such a configuration, it is possible to ensure repeated display of writing and erasing information.

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

(7) Further, the average fiber width of the hydrophilic fibers 3 contained in the resin molded product 10 according to the present embodiment may be in the range of 3 nm or more and 200 nm or less.
With such a configuration, it is possible to clarify the repeated display of writing and erasing information.
(8) Further, the hydrophilic fiber 3 contained in the resin molded product 10 according to the present embodiment may be cellulose.
With such a configuration, it is possible to more reliably display the repeated writing and erasing of information.

(9) The resin molded product 10 according to the present embodiment may further contain 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 product 10 according to the present embodiment may further contain 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 product 10 according to the present embodiment may be in the range of 1 μm or more and 500 μm or less.
With such a configuration, strength and productivity can be imparted to the resin molded product 10.

(12) The synthetic resin 4 contained in the resin molded product 10 according to the present embodiment aggregates to form the synthetic resin aggregate 2, and the hydrophilic fibers 3 cover the surface of the synthetic resin aggregate 2. It may be arranged in.
With such a configuration, it is possible to repeatedly write and erase various visible information by utilizing the reversible change in transparency due to the change in water content.
(13) In the method for producing the resin molded body 10 according to the uniform state of the present embodiment, the above-mentioned resin molded body 10 is formed on the support 40 by wet coating.
With such a configuration, it is possible to manufacture the resin molded product 10 in which various visible information can be repeatedly written and erased by utilizing the reversible change in transparency due to the change in water content.

(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)
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 was mixed was prepared and the resin molded product 10 was prepared by the following procedure.

<Method for producing hydrophilic fiber 3>
Cellulose fibers used as hydrophilic fibers 3 were prepared.
(1) Reagents / Materials / Cellulose: Bleached Kraft Pulp (Fletcher Challenge Canada "MACHENZIE")
・ TEMPO: Commercial product (manufactured by Tokyo Chemical Industry Co., Ltd., 98%)
Sodium hypochlorite: Commercial product (manufactured by Wako Pure Chemical Industries, Ltd., CL: 5%)
・ Sodium bromide: Commercial product (manufactured by 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 prepare a pulp suspension. Further, 5 mmol / g of sodium hypochlorite was added per weight of cellulose with stirring. At this time, about 1N of sodium hydroxide aqueous solution was added to maintain the pH of the pulp suspension at about 10.5.
Then, the reaction was carried out for 2 hours, and 10 g of ethanol was added to stop the reaction to obtain oxidized cellulose in which a carboxyl group was introduced into cellulose. 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, 0.5 N hydrochloric acid was added dropwise to lower the pH to 2.
Cellulose was filtered off using a glass filter, washed 3 times with 0.05 N hydrochloric acid to make the carboxyl group a carboxylic acid, and then washed 5 times with pure water to obtain wet cellulose oxide with a solid content concentration of 20%. Got The obtained oxidized cellulose was calculated to have a carboxyl group amount of 1.6 mmol / g per dry weight of cellulose by neutralization titration with sodium hydroxide.

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

<Preparation of composition 20 and resin molded product 10>
(1) Preparation of Composition 20 Synthetic resin 4 (manufactured by Nichika Kagaku Co., Ltd., polyurethane dispersion type, Neosticker 1200) and cellulose fibers prepared by the above procedure are 100: 40 in this order in terms of solid content weight ratio. The composition 20 of the synthetic resin 4 and the cellulose fiber was prepared by mixing overnight with a stirrer.
(2) Preparation of Resin Mold 10 The prepared composition 20 is applied to a PET film (Lumilar T60-75 μm: Toray) with an applicator, dried in an oven at 120 ° C. for 10 minutes, and then the PET film is peeled off. By doing so, a resin molded product 10 having a thickness of 20 μm was produced.

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

(Example 5)
A 15 wt% aqueous solution of PVA (PVA105 manufactured by Kuraray Co., Ltd.), which is a thermosetting resin using a cross-linking agent, is prepared, and the synthetic resin 4, cellulose fibers, and PVA are in this order in the solid content weight ratio of 100: 80: 10. Prepared as follows. Other than that, the resin molded product 10 was produced under the same conditions as in Example 2.
(Example 6)
Synthetic resin 4, cellulose fibers, photocurable resin (KJ Chemicals, HEAA), and photopolymerization initiator (BASF, Irgacare500) are in this order by solid content weight ratio of 100: 80: 10: 0.3. It was prepared so as to be. Other than that, the resin molded product 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 solid content weight ratio was 100: 250 in this order. Other than that, the resin molded product 10 was produced under the same conditions as in Example 2.

(Comparative Example 1)
A resin molded product 10 was prepared 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 product 10 was prepared 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)
The dispersion treatment time using a mixer in the preparation of the cellulose fiber was set to 10 minutes. Other than that, the resin molded product 10 was produced under the same conditions as in Example 2. The average fiber width of the cellulose fibers at this time was 500 nm.

[evaluation]
For 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]
The cellulose fibers were diluted with water so as to be 0.001 wt%, developed on mica and air-dried, and then the sample was observed with a transmission electron microscope. 100 samples were randomly taken and the average value was determined as the average fiber width (nm).

[Haze of resin molded product 10]
The obtained resin molded product 10 was immersed in water for 1 minute, and then the moisture on the surface was wiped off. Immediately after that, the haze was measured on the surface opposite to PET when the resin molded product 10 was formed. The value at this time was set to HZ ₁ . Further, the sample immersed in water was dried in an oven at 60 ° C. for 30 minutes, and then the humidity was adjusted in a constant temperature and humidity chamber at 23 ° C. and 50% RH for 2 days, and then the haze was measured in the same manner. The value at this time was set to HZ ₂ .
[Light transmittance of resin molded product 10]
For the resin molded body 10, the light transmittance (%) at a wavelength of 660 nm was measured using a UV-VIS spectrophotometer (UV3600, manufactured by Shimadzu Corporation) under the same conditions as _{when haze HZ 2 was measured.} ..

[Visibility]
With respect to the resin molded body 10 under the same conditions as the measurement of the haze HZ ₂ , writing was performed on the resin molded body 10 using a brush-shaped writing tool capable of retaining water, and sensory evaluation was performed as to whether or not the resin molded body 10 could be visually recognized. .. The one with extremely high visibility is "◎", the one with high visibility is "○", the one with high visibility is "△", and the one with low visibility is "×". Evaluated as.
[Repeat durability]
The visibility of the resin molded product 10 when immersed in water for 1 minute and dried in an oven at 60 ° C. for 30 minutes was repeated 100 times was visually evaluated. Similar to the above-mentioned evaluation of visibility, the one with extremely high visibility is "◎", the one with high visibility is "○", the one with high visibility is "△", and the one with high visibility is "△". 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 in Examples 1 to 7), they absorb and release moisture. It can be seen that the transparency and cloudiness opacity can be controlled by the humidity. By utilizing this, it is possible to produce a display material capable of repeatedly controlling the writing and erasing of information only by the moisture content. On the other hand, when the amount of the synthetic resin 4 is too large (in the case of Comparative Example 1) or the amount of the hydrophilic fibers 3 is too small (in the case of Comparative Example 2), it depends on the size of the hydrophobic portion region of the synthetic resin 4 and the hydrophilic fibers 3. The amount of water taken up cannot be sufficiently controlled in the development of cloudiness and opacity, and visibility is reduced.
Further, as shown in Examples 2 to 4, if the resin molded product 10 contains substantially equal amounts of the hydrophilic fibers 3 and the cellulose fibers, the visibility is further enhanced and the light transmittance is also high. You can see that.

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

1 ... Resin unit 2 ... Synthetic resin aggregate 3 ... Hydrophilic fiber 4 ... Synthetic resin 10 ... Resin molded product 20 ... Composition 30 ... Bar coater 40 ... Support T ... Thickness

Claims (14)

A synthetic resin having at least one of an aqueous dispersion component and an aqueous emulsion component , which is a resin that can be dispersed as resin particles in an aqueous dispersion medium, and a hydrophilic fiber in which the functional group at the C6 position on the surface of the cellulose fiber is a carboxyl group. , At least one of one or more types of thermosetting resins and one or more types of photocurable resins, which are different types of resins from the synthetic resin .
The average fiber width of the hydrophilic fibers is in the range of 3 nm or more and 200 nm or less.
The content of the hydrophilic fiber state, and are within the following 200 parts by weight 5 parts by weight or more with respect to the synthetic resin 100 parts by weight,
The synthetic resin aggregates to form a synthetic resin aggregate.
The hydrophilic fibers, resin moldings characterized that you have been arranged so as to cover the surface of the synthetic resin agglomerate. A synthetic resin having at least one of an aqueous dispersion component and an aqueous emulsion component , which is a resin that can be dispersed as resin particles in an aqueous dispersion medium, and a hydrophilic fiber in which the functional group at the C6 position on the surface of the cellulose fiber is a carboxyl group. , At least one of one or more types of thermosetting resins and one or more types of photocurable resins, which are different types of resins from the synthetic resin .
The haze of the resin molded product having a water content of 25% or more is defined as HZ ₁ .
If the water content was the haze of 8% or less of the resin molded body and HZ _2, HZ ₁ and HZ ₂ is meet the following formula (1) and (2),
The synthetic resin aggregates to form a synthetic resin aggregate.
A resin molded product , wherein the hydrophilic fibers are arranged so as to cover the surface of the synthetic resin aggregate.
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 , which is a resin that can be dispersed as resin particles in an aqueous dispersion medium, and a hydrophilic fiber in which the functional group at the C6 position on the surface of the cellulose fiber is a carboxyl group. , At least one of one or more types of thermosetting resins and one or more types of photocurable resins, which are different types of resins from the synthetic resin .
The haze of the resin molded product when the water content of the resin molded product has reached saturation is defined as HZ ₁ .
When the haze of the resin molded product is HZ _{2 in} a state where the water content reaches equilibrium in an environment of normal temperature and humidity (23 ° C., 50% RH) , HZ ₁ and HZ ₂ are as follows (1). meets the formula and (2),
The synthetic resin aggregates to form a synthetic resin aggregate.
A resin molded product , wherein the hydrophilic fibers are arranged so as to cover the surface of the synthetic resin aggregate.
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 in a state where the water content is 8% or less is 70% or more in terms of a film thickness of 20 nm. The feature is that the light transmittance at 660 nm in a state where the water content reaches equilibrium in an environment of humidity lower than normal temperature and humidity (23 ° C., 50% RH) is 70% or more in terms of film thickness 20 nm. The resin molded body according to claim 3. The resin molded product according to any one of claims 2 to 5, wherein the average fiber width of the hydrophilic fibers is in the range of 3 nm or more and 200 nm or less. The item according to any one of claims 2 to 6, wherein the content of the hydrophilic fiber is in the 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 molded product according to any one of claims 1 to 7, wherein the hydrophilic fiber is cellulose. The resin molded product according to any one of claims 1 to 8 , wherein the thickness of the resin molded product is within the range of 1 μm or more and 500 μm or less. The synthetic resin having at least one of the aqueous dispersion component and the aqueous emulsion component has at least one of a water-soluble monomer and a water-soluble oligomer dispersible in a dispersion medium, and the water-soluble monomer is formed by volatilizing the dispersion medium. The resin molded product according to any one of claims 1 to 9, wherein at least one of the water-soluble oligomers is deformed and fused to form a continuous structure. The synthetic resin having at least one of the aqueous dispersion component and the aqueous emulsion component is vinyl acetate-based, urethane-based, acrylic-based, styrene-based, phenol-based, amino-based, amide-based, polyester-based, ethylene-based, or polyvinyl alcohol-based. The resin molded product according to any one of claims 1 to 10, wherein the resin is the same as the above-mentioned resin. The synthetic resin having at least one of the aqueous dispersion component and the aqueous emulsion component has a particle size in the range of 0.01 μm or more and 10 μm or less, and is a resin that can be dispersed as resin particles in an aqueous dispersion medium. The resin molded product according to any one of claims 1 to 11. Any of claims 1 to 12, wherein the hydrophilic fiber has a carboxyl group content introduced into cellulose in the range of 0.5 mmol / g or more and 3 mmol or less / g per dry weight. The resin molded product according to item 1. Method for producing a resin molded article, characterized in that the resin molded article as claimed in any one of claims 1 3, formed by a wet coating on a support.

Images