JP2021011442A - Liquid component sustained-release sheet with indicator function and manufacturing method thereof - Google Patents

Abstract

To provide a liquid component sustained-release sheet with an indicator function having small error between an actual residual amount of a liquid component carried by a porous part and expiration date display.SOLUTION: A liquid component sustained-release sheet with an indicator function which is made of a stretched body of a resin composition containing a filler, the stretched body is provided with a porous part constituted by gaps formed in the surrounding of the filler, and the porous part has a shape where the gaps are communicated. The porous part carries a liquid component, and when the liquid component vaporizes, diffuse reflectance of visible light in the porous part increases, and the residual amount of the liquid component can be recognized.SELECTED DRAWING: Figure 1

Description

The present invention relates to a sustained-release sheet that discolors as the liquid component volatilizes, and a method for producing the same.

Conventionally, many functional liquid components such as insecticides, insect repellents, fungicides, and air fresheners have been used. These liquid components are obtained by volatilizing and releasing the active components to obtain the desired effect. These liquid components may be used by a method of direct coating or the like, and as shown in Patent Document 1, a sheet-like base material containing a liquid component is also known.

A sheet containing a liquid component has a time limit until the effect derived from the liquid component expires. Therefore, an indicator function that makes it easy to understand and visually judge whether or not the effect has expired may be required. In the sheet of Patent Document 1 described above, a display portion containing fine powder having a low refractive index with respect to light is arranged on a sheet-like base material impregnated with a volatile pest repellent.

Japanese Unexamined Patent Publication No. 2008-100932

In Patent Document 1, it is said that a display portion is formed on a sheet-like base material by using a forming material in which fine powder particles such as amorphous silica and a binder are mixed. The display unit is said to be transparent when the display unit is in contact with the liquid repellent, and opaque when the liquid repellent is volatilized. In such a display part, the display part becomes opaque even if the repellent on the surface of the base material is slightly reduced, and the period between the period until the visual change and the period until the effect actually expires There was a problem that differences were likely to occur. In addition, there is also a problem that a special printing device must be prepared for printing the forming material containing fine powder particles.

An object of the present invention is to provide a liquid component sustained-release sheet with an indicator function and a method for producing the same, in which there is little error between the actual remaining amount of the liquid component supported on the porous portion and the expiration date display.

The present invention solves the above problems by the means shown below. It is composed of a stretched body of a resin composition containing a filler, and the stretched body has a porous portion composed of voids formed around the filler, and the porous portion has a shape in which the voids communicate with each other. A liquid component is supported in the porous part, and when the liquid component volatilizes, the diffuse reflection of visible light in the porous part increases, and the liquid component with an indicator function that makes the remaining amount of the liquid component recognizable is sustained release. It is a sex sheet.

Further, it is a method for producing a liquid component sustained-release sheet with an indicator function, and is a porous material having a shape in which voids are communicated with each other by stretching an unstretched film made of a resin composition containing a filler while exposing it to the liquid component. This is a method for manufacturing a liquid component sustained-release sheet with an indicator function, which comprises a step of supporting a liquid component on the portion and a step of forming a fixed display portion.

In the above sheet and the method for producing the same, the stretched body is provided with a fixed display portion, and a color difference between the porous portion and the fixed display portion appears due to an increase in diffuse reflection of the porous portion, or the porous portion and the porous portion. It is preferable that the remaining amount of the liquid component can be recognized by eliminating the color difference from the fixed display unit.

In the above sheet and the method for producing the same, it is preferable that the fixed display portion is formed by heat processing or printing using ink.

In the method for producing the sheet, it is preferable that the fixed display portion is formed by a method by thermal processing selected from any of laser processing, embossing processing, and hot stamping.

According to the present invention, it is possible to provide a liquid component sustained-release sheet with an indicator function having a small error between the actual remaining amount of the liquid component supported on the porous portion and the expiration date display, and a method for producing the same.

FIG. 1A is a cross-sectional view showing the structure of an unstretched film which is a raw material of a sustained-release sheet. FIG. 1B is a cross-sectional view showing a state in which the unstretched film of FIG. 1 is stretched in the direction of the arrow. FIG. 1 (c) is a cross-sectional view showing a state in which a fixed display portion is printed on the surface of the stretched body obtained in FIG. 1 (b). FIG. 1 (d) is a cross-sectional view showing a state in which a fixed display portion is formed on the surface of the stretched body obtained in FIG. 1 (b) by laser processing. FIG. 2A shows an example in which the stretched body and the fixed display portion have the same color, and the stretched body becomes cloudy when the liquid component volatilizes. In FIG. 2B, the fixed display portion is composed of a white character string, the stretched body is colored in a dark color, and when the liquid component volatilizes, the stretched body becomes cloudy and the visibility of the white fixed display portion is lost. This is an example configured in. FIG. 3A is a cross-sectional view showing an example of a sustained-release sheet composed of a plurality of layers. FIG. 3B is a cross-sectional view showing a second example of a sustained-release sheet composed of a plurality of layers. It is sectional drawing which shows the 3rd example of the sustained-release sheet composed of a plurality of layers. It is a graph which shows the relationship between the residual amount of the liquid component in Test 2 and the elapsed days.

Hereinafter, one embodiment of the present invention will be described, but the technical scope of the present invention is not limited to this embodiment, and the configuration thereof may be appropriately changed according to the type of the target content and the like. it can.

The liquid component sustained-release sheet with an indicator function of the present invention (hereinafter, may be simply referred to as a sustained-release sheet or sheet) comprises a resin composition containing a filler. This resin is not particularly limited, but since the sustained-release sheet carries a liquid component, it is preferably a resin that does not easily react with the liquid component. For example, when the liquid component is a chemical, it is preferably a polyolefin resin having excellent chemical resistance.

The amount of liquid components volatilized and released may depend on the crystallinity of the resin. Therefore, among the polyolefin resins, those containing low crystalline polyolefin are preferable. Low crystallinity polyolefins are low crystallinity polyolefins, such as low density polyethylene, low stereoregular polypropylene, ethylene-vinyl acetate copolymers, ethylene-alkyl acrylate copolymers, and ethylene-propylene copolymers. One or more kinds of polyolefins selected from the group consisting of the above can be used. Since the resin containing a polar group easily reacts with a polar liquid component, it is preferable to use low density polyethylene, low stereoregular polypropylene, or ethylene-propylene copolymer. Since the sustained-release sheet is stretchable, it is more preferable to contain linear low-density polyethylene.

As the filler, an inorganic filler such as calcium carbonate, talc, silica, mica, zinc oxide, barium sulfate, titanium oxide, or aluminum can be used. It may be an organic substance that is incompatible with the resin that is the main raw material and exhibits hard properties at room temperature. When the main raw material is polyolefin, for example, an organic substance such as polystyrene, methacrylic resin, or polyester can be used as the filler.

The filler is for forming innumerable voids by stretching, and a liquid component is supported in the voids. Therefore, the filler is preferably one that is not easily attacked by liquid components, and the inorganic filler is relatively stable. Further, it is preferable that the voids are stably distributed, and this can be easily realized by using an inorganic filler having a uniform particle size. It is preferable to use calcium carbonate from the viewpoint that it is inexpensive and easily available to meet these conditions.

The particle size of the filler is not particularly limited, but it is selected in consideration of the thickness of the sheet after stretching from the viewpoint that a plurality of voids formed by stretching are connected, that is, it is preferable that the filler is a communication hole. It is preferable to do so. For example, the particle size of the filler is preferably in the range of 0.1 to 40% of the thickness of the sheet. Further, it is preferable that the average particle size of the filler is 1.0 to 15 μm because it is easy to disperse uniformly. The average particle size is measured by the air permeation method.

The amount of the filler added varies depending on the type of filler, but it is preferable that the filler is added so that the voids formed after stretching the sheet occupy 20% by volume or more of the sheet volume. It is more preferable to form a void of 30 to 70% by volume. The voids are connected to each other even inside the sheet, and the liquid component can be contained even inside the sheet. If the voids are less than 20% by volume of the sheet volume, the voids are sparsely generated inside the sheet, and the liquid component may be supported only near the surface of the layer. Further, when the volume of the voids exceeds 70% by volume of the sheet, the volume of the resin is less than 30% by volume, so that the sheet may be brittle and difficult to handle.

The step of manufacturing the sustained-release sheet includes a step of molding the resin composition containing the filler into a film and stretching the resin composition. In the porous portion, the filler is less likely to extend when stretched than the resin, so that voids are generated around the filler. This void becomes a porous portion.

As a method of supporting the liquid component on the porous portion, there are a method in which the resin composition and the liquid component are mixed in advance and then charged into an extruder to be molded and then stretched, and a method of unstretched molded into the liquid component. Examples thereof include a method of stretching while exposing the resin composition. Either method may be adopted, but the method of charging the liquid component into the extruder has a restriction that the liquid component to be supported requires heat resistance. In addition, the liquid component to be supported may affect the dispersion of the resin composition. As described above, in the method of charging the liquid component into the extruder, there may be restrictions on the liquid component that can be adopted. Therefore, a method of stretching the molded unstretched resin composition while exposing it to a liquid component is preferable.

In the sustained-release sheet, when the liquid component of the porous portion volatilizes, the diffuse reflection of the stretched body increases. As a result, the appearance of the sustained-release sheet changes, and it is possible to know when the remaining amount of the liquid component decreases and the utility expires. More specifically, in a state where the porous portion carries a liquid component, the difference between the refractive index of the resin and the refractive index of the liquid component is small. On the other hand, when the liquid component volatilizes, the porous portion is filled with air, and the difference in refractive index becomes large. Since a large number of voids exist at various positions inside the sheet, the light entering each void is diffusely reflected and the stretched body appears cloudy. The state of diffuse reflection can also be confirmed by measuring the reflection of visible light with a spectrophotometer. The reflectance tends to increase as the liquid component is carried and then volatilized. Since the remaining amount of the liquid component supported on the stretched body can be determined from the degree of cloudiness of the stretched body, the sustained-release sheet of the present invention can serve as an indicator.

In order to clarify the indicator function, it is preferable to color the stretched body. It is easier to perceive the color change when the colored stretched body becomes cloudy than when the uncolored transparent stretched body turns white. This is because the color attributes change significantly. Hue, saturation, and lightness are the three attributes of color. Hue indicates the direction (type) of a color such as red or blue, saturation indicates the vividness of the color, and lightness indicates the brightness of the color. Since transparency is colorless, it does not have any of the three attributes. White is called an achromatic color, which is a color that consists only of lightness and has no saturation and hue. On the other hand, red and the like consist of a combination of all three attributes. That is, the change from colorless to white is only the change in lightness, but the change from red or the like to white also changes the saturation and hue, so that the consumer can more easily recognize that the color has changed.

As a method of coloring, the resin composition may contain a colorant, or the liquid component may contain a colorant. Since it is desirable that the porous portion contains a large amount of the liquid component in order to maintain the effect of the liquid component for a longer period of time, it is preferable that the proportion of the colorant in the porous portion is small, rather than including the colorant in the liquid component. It is also preferable that the resin composition contains a colorant in advance. Above all, a method of mixing the pigment masterbatch with the resin composition is desirable.

When the stretched material is colored, the base reflectance differs depending on the color, but if the difference in reflectance between the state in which the liquid component is carried and the state in which the liquid component is volatilized is 5% or more, the color of the sheet changes. It is preferable that you can visually recognize what you have done. A difference of 10% is more preferable because the color change can be recognized more clearly.

The reflectance is also affected by the thickness of the sheet. If the thickness is too small, a difference in reflectance is unlikely to occur. Therefore, the thickness of the sheet is preferably 50 to 2,000 μm.

In the sustained-release sheet, since the voids in the porous portion form communication holes, even if the liquid component on the surface of the stretched body volatilizes, the liquid component on the inside moves to the vicinity of the surface. As a result, the liquid component can always be released with a constant amount of volatilization. That is, air is filled in the porous portion near the surface only after the liquid component inside the sheet becomes extremely small, and the stretched body becomes cloudy. Therefore, the difference between the period until the indicator changes visually and the period until the liquid component actually runs out and the effect expires is small. When the sustained-release sheet of the present invention is used at home, for example, as an insect repellent sheet, a replacement label is displayed even though the liquid component still remains and the insect repellent effect remains. It leads to reduction of waste such as replacement.

A fixed display unit may be further provided on the surface of the sustained-release sheet. The fixed display unit is arranged on the surface of the stretched body, and is a display unit whose appearance does not change even if the liquid component of the porous portion volatilizes. When the liquid component volatilizes in the porous portion, diffuse reflection increases and the color changes. On the other hand, the fixed display unit retains the originally formed shape and color even if the liquid component volatilizes. The fixed display unit is used to more clearly indicate the effective time of the liquid component by utilizing the color difference between the porous portion and the fixed display unit. For example, as a fixed display unit, characters such as "Please replace" are formed on the surface of the stretched body. When the liquid component of the porous portion volatilizes, the porous portion becomes cloudy, but the character portion retains the originally formed shape and color. Characters can be visually recognized by increasing the difference in reflectance between the cloudy porous portion and the fixed display portion. The user can recognize that the remaining amount of the liquid component has decreased by visually recognizing the characters. As a result, appropriate actions such as replacement of the sustained-release sheet can be taken.

The fixed display unit may be formed, for example, by processing using heat (hereinafter referred to as heat processing) or by printing using ink. Examples of the thermal processing include laser processing, embossing, hot stamping, and the like, which will be described later.

A step of supporting the liquid component in a porous portion having a shape in which voids communicate with each other by stretching an unstretched film made of a resin composition containing a filler while exposing the liquid component, and a step of forming a fixed display portion. Can't do any of the steps first. However, it is preferable to carry out the step of supporting the liquid component and then the step of forming the fixed display portion because the fixed display portion does not need to be stretched. When the fixed display unit is stretched, the fixed display unit may be distorted due to the stretching. If the execution order is as described above, it is possible to avoid distortion of the fixed display unit. This is especially effective when the fixed display unit contains a character string.

When the fixed display portion is formed by heat processing, the surface of the stretched body is heated to form a shape, so that it is not necessary to consider the affinity with the supported liquid component. When the fixed display unit is formed by printing with ink, the range of color selection is widened, and a color with higher visibility can be appropriately adopted. In either case, since no special equipment is required for forming the fixed display portion, there is an advantage in the manufacturing process.

An example of the manufacturing process of the sustained-release sheet will be described with reference to the drawings. FIG. 1A shows the structure of the unstretched film which is the raw material of the sustained-release sheet 1. In the unstretched film, the filler 3 is solidified in a dispersed state in the synthetic resin 2. Such an unstretched film containing a filler is obtained by extruding a resin composition containing the filler from an extruder, molding it into a film, and then cooling it without stretching to obtain a solidified film. can get. In the state of the unstretched film, the porous portion has not yet been formed. The extruder, die, and cooling device for forming the unstretched film may be known.

FIG. 1B is a diagram showing a state in which the unstretched film is stretched in a state where the unstretched film and the liquid component 4 are in contact with each other. By stretching the unstretched film in contact with the liquid component 4, voids are formed around the filler, and the liquid component enters the voids, that is, the porous portion 5 and is supported. The stretching may be a known stretching that stretches according to the speed ratio between the rolls. However, note the following points. That is, when the film is exposed to the liquid component after the film is stretched in air, the liquid component is not supported in the void because air has already entered the void. Therefore, the unstretched film needs to be stretched in a state of being exposed to the liquid component 4 before being stretched.

After the step of FIG. 1 (b), the step of FIG. 1 (c) or FIG. 1 (d) is carried out. FIG. 1C is a diagram showing a state in which the fixed display unit 6 is formed by printing with ink. FIG. 1D is a diagram showing a state in which the fixed display unit 6 is formed by laser processing. In printing using ink, a layer of ink is printed on the surface of the stretched body to cover and close the gap. In the laser processing method, the surface of the stretched body is irradiated with laser light to burn the vicinity of the surface of the stretched body and close the voids.

According to the above method, the volatilization of the liquid component is inhibited in the fixed display unit, and the liquid component volatilizes in the portion other than the fixed display unit. Therefore, even if the liquid component supported on the stretched body volatilizes and the entire stretched body becomes cloudy, the original shape and color are maintained on the fixed display portion.

FIG. 2A shows an example in which the character string "Please replace" is formed as a fixed display portion on the surface of the stretched body. In this example, the stretched body and the character string are formed as the same color. While the liquid component is supported on the porous portion of the stretched body and the effect of the liquid component is exhibited, the entire sheet including the stretched body and the fixed display portion has the same color. When the amount of the liquid component decreases, the portion of the stretched body other than the character string becomes cloudy. As a result, a color difference between the stretched body and the character string which is the fixed display unit appears, and the character string becomes visible.

FIG. 2B shows an example in which the character string "beginning" is printed as a fixed display portion on the surface of the stretched body. In this example, the stretched body is colored dark and the character string is printed in white. While the liquid component is supported on the porous portion of the stretched body and the effect of the liquid component is exhibited, the character string is in a visible state due to the color difference between the stretched body and the character string. When the amount of the liquid component decreases, the portion of the stretched body other than the character string becomes cloudy. As a result, the color difference between the stretched body and the character string which is the fixed display unit disappears, and the character string becomes invisible. In the example of FIG. 2B, it can be visually recognized that the liquid component remains and the effect is exhibited while the character string is visible. In FIG. 2B, the appearance of the stretched body is shown on a black background, the appearance of the stretched body that is cloudy is shown on a white background, and the white character string is shown in white.

The fixed display portion may be a line, a pattern, or a pattern, as long as the appearance or disappearance of the color difference from the stretched body having the porous portion can be identified.

When forming clearer characters, it is easier to form a fixed display portion by thermal processing. If the fixed display portion is formed by heat processing, there is less problem of weather resistance deterioration even in outdoor use, and changes in color and shape can be determined more accurately, which is preferable. When forming a fixed display portion by printing, the affinity between the liquid component and the ink must be taken into consideration. The liquid components or inks used may be limited. Further, if an ink having poor weather resistance is used, the color may fade, and the color difference from the porous portion tends to be unclear.

The sustained-release sheet may be formed of a single layer including a porous portion, may be formed of a plurality of layers, or may be formed by laminating arbitrary layers.

FIG. 3A shows an example in which a layer containing a porous portion is formed by two layers. One of the two layers is a colored layer 5a containing a pigment or the like. The other layer of the two layers is the uncolored layer 5b. By coextruding the two layers and then stretching them in the liquid component, the liquid component can be supported in the voids around the filler. The uncolored layer 5b can transmit the color of the adjacent layer. When both the colored layer 5a and the non-colored layer 5b carry a liquid component, the non-colored layer 5b transmits the color of the colored layer 5a and exhibits the color of the colored layer 5a as a sustained-release sheet. When the liquid component volatilizes, the porous portion of the non-colored layer 5b becomes cloudy, and the color of the entire sheet becomes white.

As shown in FIG. 3 (b), one of the two layers is a non-porous layer 7a to which no filler is added, and the other layer of the two layers is the same as in FIG. 3 (a). A sustained-release sheet having a non-colored layer 5b may be used.

In FIG. 3C, one of the two layers is a non-colored layer 7b to which no filler is added, and the other layer of the two layers has a porous portion as in FIG. 3A. It is a sustained-release sheet in which the colored layer 5a is included and the fixed display portion 6 is provided on the surface of the sustained-release sheet. In the sustained-release sheet of FIG. 3C, the fixed display portion 6 is provided on the uncolored layer 7b to which no filler is added and which does not have a porous portion. Since the liquid component supported on the porous portion of the colored layer 5a is separated by the non-colored layer 7b having no porous portion, even if the fixed display portion 6 is printed with ink, the liquid component is separated from the ink. It is preferable in that it is not necessary to consider the affinity with the liquid component.

The sustained-release sheet is not limited to the above-mentioned single-layer structure or the above-mentioned two-layer co-extrusion structure. For example, it is also possible to laminate an adhesive layer, a woven fabric, or a non-woven fabric on a sustained-release sheet. These can be laminated, for example, through an adhesive synthetic resin, applied with an adhesive, or by any other known method.

When a pressure-sensitive adhesive layer or the like is laminated on one side of a sheet-shaped stretched body or a fixed display portion is printed, if a liquid component remains on the surface of the stretched body, the pressure-sensitive adhesive layer or the fixed display portion is applied to the stretched body. It becomes difficult to fix. As a countermeasure for this, as described above, in addition to the method of adhering or printing through a layer not provided with a porous portion, there is a method of exposing a liquid component to only one side.

An example of a method of exposing a liquid component to only one side is given. First, an unstretched body is formed into a cylindrical film by a tubular method. Bend both ends of the cylindrical film in the width direction to form a double surface of the film. After that, a part of the planar unstretched body is stretched while being in contact with the liquid component, so that the liquid component is supported in the voids formed around the filler. Then, the bent portions are cut off at both ends of the planar stretched body. In this way, the liquid component can be sufficiently and surely exposed to the outer surface of the cylinder without contacting the inner surface of the cylinder with the liquid component. When an unstretched body in the form of a cylindrical film is obtained by this method, if it is molded in a so-called inflation state with a large blow ratio, stretching occurs during molding. In order to suppress such stretching, it is desirable to keep the blow ratio in the range of 0.5 to 1.2 times.

The sustained-release sheet can be manufactured by various manufacturing methods, and can also be manufactured by a method in which a fixed display unit is not arranged. However, it is preferable to provide a fixed display unit so that the function of the indicator can be easily transmitted to the consumer. If it is only a simple color change, a separate instruction such as "Please replace when the color changes" is required. For example, it is possible to give a direct instruction to a person's judgment by directly displaying "Please replace" in characters. Direct instructions are more likely to lead to specific actions after that. Further, it is easier and clearer to judge whether a specific character string or the like is "visible" or "invisible" than to judge a subtle difference in color.

The liquid component releases a component having a biological activity, a physical or chemical action, which is exemplified by an insecticide, an insect repellent, a fungicide, a fragrance, a rust preventive, or an aroma oil. As the liquid component, a liquid component having a vapor pressure of 1 × 10 ^-4 to 10 ⁴ Pa at room temperature of 25 ° C. can be supported on a sustained-release sheet. Those in this vapor pressure range are highly volatile liquid components. In the sustained-release sheet of the present invention, even such a liquid component can be effective for a long period of time.

A diluting solvent may be dispersed in the liquid component. Examples of the diluting solvent include liquid paraffin, isopropyl alcohol, n-heptane and the like. By blending a diluting solvent to dilute the liquid component, the liquid component can be supported on the porous part with an appropriate interfacial tension, a large amount of the liquid component can be contained in the voids of the porous part, and the concentration of the liquid component can be adjusted. By doing so, it is possible to prevent deterioration of the sheet. Deterioration of the sheet can also be suppressed by blending a highly crystalline polyolefin as the resin composition.

It is preferable that the porous portion on which the liquid component is supported contains the liquid component in the range of 5 to 90% based on the volume of the pores. Even if the content is small, the liquid component stays in the porous part for a long time due to its structure, and it is effective for a long period of time. If the content is too high, the liquid component may seep out onto the sheet surface. Therefore, the content of the liquid component is more preferably 5 to 50%.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the following Examples.

In order to evaluate the indicator function of the sustained-release sheet, each sheet sample was prepared with a formulation in which the effect lasted for about 90 days.

[Example 1]
Linear low density polyethylene (density 0.932 g / cm ³ , melting point 123 ° C, MFR 3.0 g / 10 min (190 ° C, 2160 g load)) 15% by mass; low density polyethylene (density 0.923 g / cm ³ , melting point 112 ° C) , MFR 1.5 g / 10 min (190 ° C, 2160 g load)) 15% by mass; ultra-low density polyethylene (density 0.900 g / cm ³ , melting point 115 ° C, MFR 2.0 g / 10 min (190 ° C, 2160 g load)) 7 mass %; Calcium carbonate (average particle size 5 μm by air permeation method) 58% by mass; and 5% by mass of black pigment were mixed, and the mixture A was extruded by the T-die method and cooled by a chill roll to obtain an unstretched film 1. ..

After passing through the nip roll, the unstretched film 1 is passed through the first roll for stretching, the constant temperature liquid tank (liquid tank temperature: 60 ° C.), and the second roll for stretching in the order described, and the intermediate stretched body 1 is passed through. Obtained. At this time, the constant temperature liquid tank is immersed with metoflutrin (vapor pressure 1.96 × 10 ^-3 Pa) as a liquid component, and the speed ratio (stretching ratio) of the first roll and the second roll is 5 times. , Stretching was performed in a state of being exposed to the liquid component.

The intermediate stretched body 1 obtained above is subjected to a third roll composed of a plurality of heat roll groups (temperature: 70 ° C.) for stretching and a fourth roll composed of a plurality of heat roll groups (temperature: 70 ° C.) for heat relaxation. It was continuously passed through a roll and wound up. The final roll speed ratio (stretching ratio) of the second roll and the third roll was 1.3 times. The final roll speed ratio of the third roll to the fourth roll was 0.9 times, and the stretching was relaxed by 10%. A wound sheet body 1 was obtained. The thickness of the sheet was 180 μm.

[Example 2]
A sheet body 2 was obtained in the same manner as in Example 1 except that the pigment of the mixture A was changed to a red pigment. After that, "Please replace" was printed on the sheet body 2 with red ink to obtain the indicator sheet 2. The thickness of the sheet was 180 μm.

[Example 3]
The mixture A of Example 1 was extruded by a tubular method and cooled by an air cooling method at a blow ratio of 0.8 to obtain an unstretched film 3 made of a tubular film. The same as in Example 1 except that the unstretched film 3 is sandwiched between nip rolls, both ends in the width direction are bent to form a planar shape in which two intermediate portions in the width direction are stacked, and then stretching or the like is performed in this state. The sheet body 3 was obtained. After that, "Please replace" was printed on the surface with a laser beam to obtain an indicator sheet 3. The thickness of the sheet was 180 μm.

[Example 4]
Linear low density polyethylene (density 0.932 g / cm ³ , melting point 123 ° C, MFR 3.0 g / 10 min (190 ° C, 2160 g load)) 16% by mass; low density polyethylene (density 0.923 g / cm ³ , melting point 112 ° C) , MFR 1.5 g / 10 min (190 ° C, 2160 g load)) 16 mass%; ultra-low density polyethylene (density 0.900 g / cm ³ , melting point 115 ° C, MFR 2.0 g / 10 min (190 ° C, 2160 g load)) 8 mass % And 60% by mass of calcium carbonate (average particle size 5 μm by air permeation method) were mixed as an outer layer, and the mixture A of Example 1 was used as an inner layer, and the multilayer film was co-extruded with a three-layer T-die extruder. Then, it was cooled with a chill roll to obtain an unstretched film 4. The unstretched film 4 was stretched in a constant temperature liquid phase in the same manner as in Example 1 to obtain a sheet body 4. The thickness of the sheet was 240 μm.

[Comparative Example 1]
A non-woven fabric (grain 90 g / m ² , thickness 490 μm) is impregnated in a constant temperature liquid bath in which a black pigment is added to the same liquid component as in Example 1, and a forming material containing amorphous silica is printed on it using vinyl acetate as a binder. I got the indicator sheet 5. The thickness of the sheet was 500 μm.

[Test 1: Content]
The sheet bodies and indicator sheets obtained in Examples 1 to 4 and Comparative Example 1 were each cut into 5 cm square test pieces. After the initial weight of each test piece was measured, ultrasonic cleaning with hexane was performed at 60 ° C. for 20 minutes, and the weight after cleaning was measured. The weight difference between the initial weight and the weight after washing was determined as the content of the liquid component.

The contents of the liquid components were Example 1: 0.077 g, Example 2: 0.071 g, Example 3: 0.062 g, Example 4: 0.092 g, and Comparative Example 1: 0.18 g, respectively. It was. The reason why the content of the liquid component in the test piece of Comparative Example 1 is higher than that of the test pieces of Examples 1 to 4 is that the test piece of Comparative Example 1 has a high volatilization rate of the liquid component, so that in Example 1. This is because it is necessary to contain a larger amount of the liquid component than in Examples 1 to 4 in order to exert the effect for the same period as in.

[Test 2: Residual amount]
The sheet bodies and indicator sheets obtained in Examples 1 to 4 and Comparative Example 1 were each cut into 5 cm square test pieces. By suspending each test piece in a hot air thermostat (tank temperature 40 ° C.) and measuring the weight change thereof, the change in the residual amount of the liquid component supported on the test piece was confirmed. The obtained results are graphed and shown in FIG. The horizontal axis of FIG. 4 shows a numerical value obtained by converting the measurement time into the number of days equivalent to actual exposure.

In the test pieces of Examples 1 to 4, the weight change continues relatively slowly. From this, it can be seen that the liquid component continues to be gradually volatilized over a long period of time in any of the test pieces. On the other hand, in the test piece of Comparative Example 1, since a large weight change occurred at the initial stage, it can be seen that a large amount of the liquid component was volatilized at the initial stage.

[Test 3: Indicator visibility]
For the test pieces of Examples 1 to 4 and the test piece of Comparative Example 1, the visible light reflectance before the test 2 and 20 days after the test 2 was measured by an ultraviolet-visible near-infrared spectrophotometer (Shimadzu Corporation). (Made), and the average value is shown in Table 1.

At the time of 20 days of the test, almost no change in the reflectance was observed for the test pieces of Examples 1 to 4. On the other hand, the reflectance of the test piece of Comparative Example 1 increased by 10% or more. When the test piece of Comparative Example 1 was visually confirmed, it was clearly cloudy. The test pieces of Examples 1 to 4 began to become cloudy after about 90 days. After 120 days, the ground color of all the test pieces was cloudy. Regarding the test piece of Example 2 and the test piece of Example 3, the part where the characters were formed remained in the original color, and the other parts were cloudy and the visibility as an indicator was good. ..

From the results of Tests 2 and 3 above, it can be seen that in the test piece of Comparative Example 1, the liquid component inside the sheet was not simply reduced and cloudiness did not occur. In reality, the white turbidity that occurred with a sufficient amount of liquid component remaining is thought to be due to the rapid volatilization at the initial stage.

Looking at FIG. 4, it can be seen that in the test piece of Comparative Example 1, the initial slope of the curve is large, and the slope of the curves of Examples 1 to 4 is small throughout the entire period.

In the test piece of Comparative Example 1, the liquid component on the sheet surface is first released in a short period of time. This is the reason why the slope of the curve becomes large. At this time, the concentration of the liquid component on the sheet surface becomes low, so that it is considered that cloudiness occurs.

On the other hand, in the test pieces of Examples 1 to 4, the concentration of the component near the surface is constant for a long period of time by slowly releasing the liquid component through the communication holes. Since the amount of volatilization is stable, the slope of the curve becomes small. When the amount of liquid components inside the sheet decreases, the concentration of components near the surface decreases for the first time, and the porous portion is filled with air, causing cloudiness. That is, the decrease of the liquid component inside the sheet and the change of the color of the sheet occur at the same time. In other words, it can be said that there is little error between the actual remaining amount (effectiveness) and the indicator display.

When the test piece of Comparative Example 1 is used as a base material for a product such as an insect repellent, the user may replace the product earlier than the actual effective period. When the test pieces of Examples 1 to 4 are used, the replacement time can be performed at an appropriate timing. Further, in the test pieces of Examples 1 to 4, since the volatilization efficiency of the liquid component is excellent, it is not necessary to contain an extra large amount of the liquid component, which leads to the reduction of the production cost.

1 Sustained release sheet 2 Resin 3 Filler 4 Liquid component 5 Porous part 6 Fixed display part 5a Colored layer 5b Non-colored layer 7 Non-porous layer

Claims (5)

It consists of a stretched body of a resin composition containing a filler.
The stretched body has a porous portion composed of voids formed around the filler.
The porous part has a shape in which voids communicate with each other.
A liquid component is supported on the porous part,
A liquid component sustained-release sheet with an indicator function that increases the diffuse reflection of visible light in the porous part by volatilizing the liquid component and makes it possible to recognize the remaining amount of the liquid component. The stretched body has a fixed display part and
Due to the increase in diffuse reflection in the porous part, the color difference between the porous part and the fixed display part appears, or the color difference between the porous part and the fixed display part disappears.
The liquid component sustained-release sheet with an indicator function according to claim 1, which makes it possible to recognize the remaining amount of the liquid component. The liquid component sustained-release sheet with an indicator function according to claim 2, wherein the fixed display unit is formed by heat processing or printing using ink. It is a method of manufacturing a liquid component sustained-release sheet with an indicator function.
A step of supporting a liquid component in a porous portion having a shape in which voids communicate with each other by stretching an unstretched film made of a resin composition containing a filler while exposing it to the liquid component.
A method for manufacturing a liquid component sustained-release sheet with an indicator function, which comprises a step of forming a fixed display portion. The method for producing a liquid component sustained-release sheet with an indicator function according to claim 4, wherein the fixed display unit is formed by a method by thermal processing selected from any of laser processing, embossing, and hot stamping.