JP7139121B2 - Sustained-release sheet and manufacturing method thereof - Google Patents

Description

TECHNICAL FIELD The present invention relates to a sustained-release sheet that slowly releases a liquid component and a method for producing the same.

Conventionally, many functional liquid ingredients such as insecticides, insect repellents, fungicides, and fragrances have been used. These liquid components obtain the intended effects by volatilizing and releasing effective components. As a method of using a liquid component, there is a method of directly applying the liquid component, such as applying the liquid or spraying the liquid component. be able to. However, this method is only effective for a short period of time because the liquid component easily runs off. These liquid ingredients may be required to have a longer lasting effect.

When it is intended to prolong the effect of the liquid component, a simple method is to impregnate the nonwoven fabric with the liquid component. A method of kneading a liquid component into a synthetic resin has also been proposed as a method of slowly and gradually releasing the effect to prolong its effect. For example, Patent Literature 1 describes a method of adsorbing a liquid perfume to porous silica and dispersing it in a thermoplastic resin.

JP 2003-094569 A

In the method of impregnating a nonwoven fabric with a liquid component, it is possible to support a large amount of the liquid component, but the amount of the liquid component released decreases significantly with the passage of time, and the effect does not last for a long time. In addition, in the method of impregnating the nonwoven fabric, the liquid component is difficult to stay in the nonwoven fabric, and the liquid component moves to the nonwoven fabric, which may cause adverse effects such as staining on the contacting object.

In the method of kneading the liquid component into the inside of the synthetic resin, it is required that the liquid component should not be degraded by heat even at a considerably high temperature because it is passed through an extruder. Even if it passes through an extruder, it cannot be formed into a proper shape unless it is properly dispersed and the extrusion state is stable. For this reason, a large limitation arises in the range in which it can be used. In addition, since the liquid component is kneaded into the resin, it seems that the effect will last for a long time, but the liquid component may seep out to the surface earlier than expected and the effect may not last for a long time.

An object of the present invention is to provide a sustained-release sheet in which a liquid component is supported by a porous layer and the effect of the liquid component is maintained, and a method for producing the same.

The present invention is based on findings obtained from the results of studies on a sustained-release sheet and its manufacturing method, that is, the voids around the filler in the stretched body provided with a porous layer made of a resin composition containing a low-crystalline polyolefin and a filler. This is based on the knowledge that it is suitable for a sustained-release sheet to carry a liquid component in the . That is, the present invention is as follows.

(1) It has a porous layer made of a resin composition containing a low-crystalline polyolefin and a filler, the porous layer is an elongated body having voids around the filler, and the voids are filled with a room temperature of 25°C. A sustained-release sheet carrying a liquid component having a vapor pressure of 1×10 ⁻⁴ to 10 ⁴ Pa at .
(2) The sustained-release sheet according to (1) above, wherein an adhesive layer is laminated on the stretched body.
(3) The sustained-release sheet according to (1) or (2) above, wherein the stretched body is a laminated stretched body in which a protective layer made of a highly crystalline resin is laminated on a porous layer.
(4) The unstretched body of the first resin layer made of a resin composition containing a low-crystalline polyolefin and a filler is stretched while being brought into contact with at least a part of the liquid component, and the liquid is formed in the voids formed around the filler. A method for producing a sustained-release sheet that forms a porous layer in which components are supported.
(5) The unstretched body obtained by co-extrusion of the first resin layer and the second resin layer made of the crystalline resin composition is subjected to the stretching, and the porous layer is made of the crystalline resin composition. The method for producing a sustained-release sheet according to (4) above, wherein a protective layer is laminated.
(6) The method for producing a sustained-release sheet according to (4) or (5) above, wherein the unstretched body is in the form of a cylindrical film.
(7) The sustained-release property according to any one of (4) to (6) above, wherein after forming a porous layer in which a liquid component is supported in the voids by the stretching, the porous layer is further stretched and/or subjected to thermal relaxation treatment. Sheet manufacturing method.

According to the present invention, it is possible to provide a sustained-release sheet in which a liquid component is supported by a porous layer and the effect of the liquid component is maintained, and a method for producing the same.

FIG. 4 is a schematic diagram showing how a liquid component is supported in voids of a porous layer by stretching. (a) the unstretched state, (b) the state in which the film is stretched while being brought into contact with the liquid component, and (c) the state after stretching. The graph which shows the evaluation result of the volatilization time in each Example and a comparative example.

Preferred embodiments for carrying out the present invention are described below.

The sustained-release sheet has at least a porous layer formed by stretching a resin composition containing low-crystalline polyolefin and a filler as a first resin layer. This low-crystalline polyolefin is a polyolefin with low crystallinity, and includes low-density polyethylene, low-stereoregular polypropylene, ethylene-vinyl acetate copolymer, ethylene-alkyl acrylate copolymer, ethylene-propylene copolymer, and the like. It refers to a single substance or a mixture of multiple types. The reason for using polyolefin is that it has excellent chemical resistance and does not readily react with liquid components. From this point of view, it is preferable to use low density polyethylene, low stereoregularity polypropylene, and ethylene-propylene copolymer. Since it involves stretching, it is more preferable to contain linear low-density polyethylene.

The reason for using a polyolefin with low crystallinity is that the amount of released liquid component changes depending on the crystallinity. The lower the crystallinity, the easier it is for the liquid component to be released through the resin. If the crystallinity is too high, the liquid component is hardly released. In other words, it is possible to control the release of the liquid component by combining a low-crystalline polyolefin with a highly-crystalline polyolefin, or by combining a low-crystalline polyolefin with a more amorphous polyolefin. When low-density polyethylene is used as the low-crystalline polyolefin, the lower the density, the lower the crystallinity tends to be, and it is preferable to include one having a density of 0.895 to 0.925 g/cm ³ . In addition, when drawing is involved and the influence of liquid components in processing is considered, it is preferable that the drawing process can be performed at a low temperature, and the melting point of low-density polyethylene is preferably 80 to 135 ° C., and the softening point is 45 to 90 ° C. is preferred. In addition, high-crystalline polyolefin to be combined with low-crystalline polyolefin is typically isotactic polypropylene, high-density polyethylene, etc. When mixed with low-density polyethylene, high-density polyethylene is used in consideration of dispersibility. preferably.

Fillers mainly refer to inorganic fillers such as calcium carbonate, talc, silica, mica, zinc oxide, barium sulfate, titanium oxide, and aluminum, but are incompatible with low-crystalline polyolefins such as polystyrene, methacrylic resin, and polyester. It may be an organic material that exhibits a hard property at room temperature. The filler is for forming countless voids by stretching, and the liquid component is carried in the voids. Therefore, it is preferable that the filler is not easily affected by the liquid component, and the inorganic filler is relatively stable. Moreover, it is preferable that the voids are stably distributed, and this can be easily achieved by using an inorganic filler with a uniform particle size. It is preferable to use calcium carbonate from the viewpoint that it is inexpensive and can be easily obtained to meet these conditions. The particle size is not particularly limited, but it is preferable that the plurality of voids formed by stretching are connected, that is, it is preferable that the pores are continuous pores, so the particle size is selected in consideration of the thickness of the porous layer after stretching. preferably between 0.1 and 40% of the thickness of the porous layer. The individual particle size is preferably from 1.0 to 15 μm, because it facilitates uniform dispersion.

The filler is preferably added to the extent that it occupies 40% by mass or more of the mass of the first resin layer. More preferably, it ranges from 40 to 70 mass % of the weight of the first resin layer. By adding the filler in this range, a plurality of voids formed by stretching are connected, and the liquid component can be included even inside the porous layer, and a large amount of the liquid component can be supported. If the filler content is less than 40% by mass or more of the weight of the first resin layer, voids will be sparsely generated, and there is a possibility that the liquid component can be carried only near the surface of the layer. Moreover, when the filler exceeds 70% of the weight of the first resin layer, the weight of the resin is less than 30% by mass, and the sheet may become brittle and difficult to handle.

The first resin layer can form a film-like unstretched body using a known extruder. This film-like unstretched body may be molded by a general method for producing a film. After being molded into a film, it is cooled without being stretched and is once solidified. After solidification, it is drawn while being contacted with and exposed to liquid components. FIG. 1 is a schematic diagram showing how the liquid component is carried in the voids after being stretched. This drawing may be a known drawing that draws according to the speed ratio between rolls. In the stretching process, as shown in FIG. 1(b), voids are formed around the filler in the first resin layer. The voids formed here are formed in a vacuum state, and when the film is stretched while being exposed to the liquid component, the liquid component is sucked up and carried around the filler. In order to support the liquid component around the filler, it is extremely important that the filler is stretched while being exposed to the liquid component. If this is done, air will enter around the filler, and the amount of the liquid component that can be carried will decrease. Considering that the unstretched body is evenly exposed to many liquid components, it is preferable to immerse the entire unstretched body in the liquid component.

When considering laminating or printing a pressure-sensitive adhesive layer or the like on one side of a sheet-like stretched body obtained by stretching, if liquid components remain on the surface of the stretched body, adhesion of these will be hindered. work in the direction. As a countermeasure against this, it is desirable to expose the liquid component only on one side. However, as a suitable method for producing a sustained-release sheet, a first resin layer made of a resin composition containing a low-crystalline polyolefin and a filler is formed into a cylindrical film, and a portion of the unstretched body obtained by forming a cylindrical film is added with a liquid component. There is a method of forming a porous layer in which a liquid component is supported in voids formed around the filler by stretching while contacting the filler. For example, if an unstretched body is formed in the shape of a cylindrical film by a tubular method, both ends of the diameter are bent, and the film is stretched in a double-layered state, the liquid component does not come into contact with the inner surface of the cylinder, and the outer surface of the cylinder is sufficiently covered. And it can reliably expose to the liquid component. When obtaining a cylindrical film-like unstretched body by this method, stretching will occur during molding if it is molded in a so-called inflation state with a large blow ratio, so the blow ratio should be in the range of 0.5 to 1.2 times. It is desirable to keep

The porosity of the porous layer made of the stretched body obtained by stretching the unstretched body is preferably in the range of 20 to 60%. By forming the porous layer within this range, the amount of the liquid component that can be supported and the shape retention of the porous layer are well balanced. The thickness of the porous layer is preferably 50 to 2,000 μm.

The liquid component releases components exhibiting biological activities and physical and chemical actions, such as insecticides/insect repellents, bactericides, fragrances, rust inhibitors, and aroma oils. A liquid component having a vapor pressure of 1×10 ⁻⁴ to 10 ⁴ Pa at room temperature of 25° C. is supported on the sustained-release sheet. Those in this vapor pressure range are the highly volatile class of liquid components. In the present invention, even such a liquid component can be effective over a long period of time.

In the sustained-release sheet, the voids formed by stretching hold the liquid component in the voids due to the suction force. However, if the interfacial tension between the porous layer and the liquid component is large, the liquid component is less likely to be absorbed into the voids against the suction force. Therefore, the film is generally stretched in a state of being exposed to water, but the film hardly carries water by the above method. Interfacial tension can be adjusted by diluting the liquid component. When the interfacial tension of the component to be used is large, for example, by dispersing a diluted solvent such as liquid paraffin, isopropyl alcohol, or n-heptane to obtain a diluted liquid component, a large amount of the liquid component can be absorbed into the voids of the porous layer. can be included. The diluting solvent can also prevent deterioration of the sheet by adjusting the concentration of the liquid component. This deterioration of the sheet can also be suppressed by adding highly crystalline polyolefin to the first resin layer.

The porous layer supporting the liquid component preferably contains the liquid component in a range of 5 to 90% with respect to the pores. When this content is small, it means that the liquid component is not contained so much. It can be said that a higher content is more preferable, but even if the content is small, the liquid component stays in the porous layer for a long time due to the structure, and the effect is exhibited over a long period of time. If the content is too high, the liquid component may seep out onto the surface of the porous layer. Therefore, it is more preferable to set the content of the liquid component to 5 to 50%.

The porous layer supporting the liquid component may be used alone as a sustained-release sheet, but other layers may be laminated on the first resin layer and/or the porous layer obtained by stretching it. .

The stretching causes the liquid component to be sucked into the voids, and the porous layer supporting the liquid component is brought to a state in which there is almost no exudation on the surface. In the state where the liquid component seeps out to the surface, the presence of the liquid component makes lamination difficult, but if the liquid component is sufficiently supported inside the porous layer, the first resin layer and the / Or, it becomes possible to laminate other layers on the porous layer obtained by stretching this. For example, if a pressure-sensitive adhesive layer is laminated, it can be attached to any place such as clothes, furniture, fittings, electric appliances, etc., and it becomes a sustained release sheet that can easily obtain insect repellent effect, fragrance effect, etc.

From the viewpoint of forming a sustained-release sheet that can be easily attached by laminating pressure-sensitive adhesive layers, it is also required to be easily peelable. Considering ease of peeling, it is natural that a pressure-sensitive adhesive having a strong adhesive force cannot be used, and a pressure-sensitive adhesive represented by an acrylic pressure-sensitive adhesive is used. At this time, if the liquid component slightly intervenes on the surface of the porous layer, the adhesive force between the pressure-sensitive adhesive layer and the porous layer is reduced, which causes adhesive residue. Therefore, when forming the porous layer, it is preferable that the surface on which the pressure-sensitive adhesive layer is to be laminated is as free of the liquid component as possible, such as by forming an unstretched body in the shape of a cylindrical film and then stretching the film by bringing it into contact with the liquid component. desirable. In addition, when the unstretched body is formed in the shape of a cylindrical film and then stretched by contacting the liquid component, it is possible to wind up by bringing the surfaces that are in contact with the liquid component into contact with each other. Even if the liquid component oozes out, it is possible to prevent the oozed liquid component from coming into contact with the surface that is not in contact with the liquid component.

From the viewpoint of more reliably laminating the adhesive layer, it is preferable to laminate a protective layer made of a crystalline resin on one side of the porous layer, and laminate the adhesive layer on the protective layer. In addition, if a protective layer made of a crystalline resin is provided, regardless of whether or not an adhesive layer is provided, the release of the liquid component from the protective layer side is suppressed, and the effect is more sustained and the release It can be expected that the effect will be enhanced by limiting the direction in which the protective layer is applied, and the possibility that the liquid component will react with the substance that contacts the protective layer and the component released by the liquid component will reduce the possibility that this contact substance will change in quality. can be done. In other words, it is also possible to reduce the possibility of adhesive residue or the like caused by the component released by the liquid component reacting with the pressure-sensitive adhesive to cause the pressure-sensitive adhesive to change in quality.

The protective layer made of highly crystalline resin can be laminated by any method such as using a strong adhesive. From the viewpoint of laminating with more reliable interlayer adhesion strength, when molding the first resin layer that will become the porous layer, the second resin layer that will become the protective layer after stretching is formed in a laminated state in advance by co-extrusion, This unstretched body is stretched while bringing the liquid component into contact with at least the first resin layer, thereby simultaneously forming a porous layer in which the liquid component is carried in the voids formed around the filler and a protective layer. is preferred.

The resin composition for the protective layer is not particularly limited as long as it is a resin having high crystallinity. Examples include high-density polyethylene, isotactic polypropylene, polyamide 6, polyethylene terephthalate, and polybutylene terephthalate. These are selected in consideration of the properties of the liquid component. If only the adhesiveness to the porous layer is important, it is preferable to use highly crystalline polyolefin such as high density polyethylene and isotactic polypropylene.

The layer ratio of the protective layer and the porous layer is not particularly limited, but when stretching the unstretched body obtained by co-extrusion of the first resin layer and the second resin layer as described above, the protective layer and the porous layer It is preferable that the layer ratio of the organic layers is 95:5 to 50:50. Since the drawing for obtaining the porous layer is performed at a relatively low temperature, it is difficult to draw at a high temperature. If the thickness of the second resin layer is too thick, a large stress is applied during stretching, making stretching difficult. Therefore, in order to improve stretchability, a flexible synthetic resin may be blended with the crystalline resin of the second resin layer.

When the unstretched body obtained by coextrusion of the first resin layer and the second resin layer is stretched, or when the liquid component is exposed only on one side and stretched, the liquid component is concentrated on one side, and the viscosity is low. In addition to being stretched at a temperature, the stretched body tends to curl. This curl tends to be larger and more likely to warp when the unstretched body obtained by coextrusion of the first resin layer and the second resin layer is stretched because the front and back are made of different resins. Therefore, it is preferable to perform the second stretching and/or thermal relaxation treatment after the stretching for supporting the liquid component. By performing these treatments, it is possible to straighten curls and greatly suppress warpage. In addition, if the first stretching is the stretching for supporting the liquid component, the second stretching has the effect of reabsorbing the liquid component adhering to the surface of the porous layer that cannot be completely sucked up by the first stretching. The thermal relaxation treatment has the effect of slightly filling the voids and the effect of preventing stretching back due to being stretched at a low temperature. These treatments more reliably prevent the liquid component from seeping out of the sustained-release sheet, and the effect of the liquid component continues to be exerted over a longer period of time. The second stretching or thermal relaxation treatment may be performed by heating with a hot plate, hot rolls, or the like, and stretching or thermal relaxation treatment depending on the speed ratio between the rolls. As for the heating conditions at this time, it is preferable to carry out at a temperature higher than that of the first stretching, and the temperature difference may be within 20°C.

The above description of the second stretching and/or thermal relaxation treatment means that either the second stretching or the thermal relaxation treatment may be performed, but it is more preferable to perform both of them. It is more preferable to perform thermal relaxation treatment after performing the second stretching. If the stretched resin is left to stand after the first stretching and the second stretching, the stretched resin will have a large force to shrink. In addition, if the thermal relaxation treatment is performed immediately after the first stretching, the liquid component held in the voids may seep out due to the forcible shrinkage. The draw ratio in the second drawing is preferably in the range of 1.01 to 1.5 times, and the shrinkage in the thermal relaxation treatment is preferably in the range of 5 to 20%.

The sustained-release sheet obtained as described above releases the liquid component over a long period of time while maintaining a constant release amount. , furniture, electrical appliances, fittings, etc. For example, if an insect repellent is used as a liquid component, it can be easily applied to clothing or sashes around windows to obtain an insect repellent effect, and if an air freshener is used as a liquid component, clothing and living room furniture can be easily obtained. It can also be used as an alternative to a fragrance spray by sticking it to something like this.

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

[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)) 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% 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)) 8 mass % and 60% by mass of calcium carbonate (average particle size 5 μm) was extruded by a T-die method and cooled by a chill roll to obtain an unstretched film 1 .

After passing through nip rolls, the unstretched film 1 is passed through a first roll for stretching, a constant temperature liquid bath (liquid bath temperature: 60 ° C.), and a second roll for stretching in the order described, and an intermediate stretched body 1 is obtained. Obtained. At this time, metofruthrin (vapor pressure 1.96×10 ⁻³ Pa) was immersed in the constant temperature liquid bath as a liquid component, and the speed ratio (stretch ratio) between the first roll and the second roll was 5 times. , the stretching was performed while being exposed to the liquid component.

After obtaining the intermediate stretched body 1, the intermediate stretched body 1 is continuously subjected to a third roll consisting of a group of heat rolls for stretching (temperature: 70° C.) and a group of heat relaxation rolls. (temperature: 70°C) and wound up. The final roll speed ratio (stretch ratio) of the second roll and the third roll was 1.3 times. The final roll speed ratio of the third roll to the final roll speed of the fourth roll was 0.9 times, and was relaxed by 10%. The wound sheet 1 was taken as Example 1. The thickness of Example 1 was 180 μm.

[Example 2]
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 2 in the form of a tubular film.

The unstretched film 2 was sandwiched between nip rolls, and both ends in the width direction were folded to form a planar shape in which two sheets were stacked in the middle portion in the width direction. An intermediate stretched body 2 and a sheet body 2 were obtained in the same manner as above. Both ends in the width direction of the wound sheet body 2 were cut along the longitudinal direction to form one sheet body 2, which was referred to as Example 2. The thickness of Example 2 was 180 μm.

[Example 3]
High density polyethylene (density 0.956 g/cm ³ , melting point 135° C., MFR 0.8 g/10 min (190° C., 2160 g load)) 70% by mass, low density polyethylene (density 0.926 g/cm ³ , melting point 124° C., MFR 0 .8 g/10 min (190° C., 2160 g load)) 30% by mass of mixture B was coextruded with mixture A used in Example 1 in a tubular system. The extruded material was cooled by an air cooling system at a blow ratio of 0.8 to obtain an unstretched tubular film 3 in which a layer of the mixture B was arranged on the inner side of the tubular film and a layer of the mixture A was arranged on the outer side of the tubular film. Thereafter, in the same manner as in Example 2, an intermediate stretched body 3 and a sheet body 3 were obtained. One sheet body 3 obtained here was taken as Example 3. The thickness of Example 3 was 200 μm (the thickness of the layer of mixture A was about 20 μm).

[Comparative Example 1]
Mixture B obtained by mixing ethylene-vinyl acetate copolymer (vinyl acetate content 14%, melting point 89°C, MFR 1.5 g/10 min) and the liquid component metofluthrin of Example 1 was extruded by a T-die method and cooled by a chill roll. , to obtain an unstretched film 4. Ethylene vinyl acetate copolymer and metofluthrin were planned to be mixed at a mixing ratio of 80:20, but the film formation was not stable, and metofluthrin exuded violently on the surface. , the exact mixing ratio is uncertain.

The unstretched film 4 was passed through nip rolls and then passed through a first roll for stretching, a hot plate and a second roll for stretching. The speed ratio (stretch ratio) between the first roll and the second roll was 5 times. The sheet thus obtained was referred to as sheet body 4, which was referred to as comparative example 1. The thickness of Comparative Example 1 was 180 μm.

[Evaluation Test 1: Content]
For Examples 1 to 3 and Comparative Example 1, test pieces were cut into 5 cm squares, respectively, and their initial weights were measured, followed by ultrasonic cleaning with hexane at 60° C. for 20 minutes. It was measured. After obtaining the weight difference between the initial weight and the weight after washing as the content of the liquid component, the content was divided by the initial weight to obtain a percentage, which was obtained as the content of the liquid component.

The contents of Examples 1 and 2 were both 18.5%, the contents of Example 3 were 14.7%, and the contents of Comparative Example 1 were 6.5%.

[Evaluation test 2: survival rate]
For Examples 1 to 3 and Comparative Example 1, a test piece cut into 5 cm squares was prepared, each was suspended in a hot air constant temperature chamber (chamber temperature 40 ° C.), and the weight change was measured. A change in the amount of volatilization of the liquid component carried on the piece was confirmed. The obtained results are graphed and shown in FIG. In FIG. 2, the weight change amount is divided by the content in Measurement Test 1 and expressed as a percentage, which is shown as a residual ratio on the vertical axis, and the elapsed time (hr) is shown on the horizontal axis.

In Examples 1 to 3, since the weight change continues at a constant amount, it can be said that the liquid component continues to volatilize gradually over a long period of time. Among them, Example 3 volatilizes longer. It can be said that the situation continues. On the other hand, in Comparative Example 1, a significant weight change occurred, and the residual rate quickly reached 0%. It can be said that there is

[Evaluation Test 3: Lamination property of pressure-sensitive adhesive layer]
For Examples 1 to 3 and Comparative Example 1, an acrylic pressure-sensitive adhesive was applied to one side of each (in Examples 2 and 3, the side opposite to the side exposed to the liquid component).

In Examples 1 to 3, an adhesive layer could be formed, but in Comparative Example 1, the adhesive was difficult to adhere due to the oozing of the liquid component. Examples 1 to 3, in which the pressure-sensitive adhesive layer was formed, were repeatedly attached to a hard plate and then peeled off.

Intermediate stretched bodies 1 to 3 produced in the process of producing Examples 1 to 3 were each made into a single sheet and coated with an adhesive in the same manner as in Examples 1 to 3. As a result, intermediate stretched body 1 was a liquid component. Bleeding was observed, and the formed pressure-sensitive adhesive layer was in a slightly uneven state. Exudation of the liquid component was also observed in the intermediate stretched body 2, but it occurred mainly on the surface exposed to the liquid component, and the opposite surface exuded very little, and almost no unevenness in the adhesive layer was observed. I didn't. Almost no exudation occurred in the stretched intermediate bodies 1 and 2 immediately after the intermediate stretched bodies were produced, but exudation occurred during storage until the adhesive was applied. The intermediate stretched body 3 was in a state where no exudation was observed on one side, but it was in a state of severe curling and was in a state of being very difficult to use. On the other hand, in the sheet bodies according to Examples 1, 2, and 3, curling was not observed, and no clear oozing of the liquid component was observed even after the storage period. In Example 1, the adhesive residue of the adhesive was observed, so there is a possibility that a small amount of liquid component was interposed between the adhesive layer and the sheet body, but in Examples 2 and 3, the liquid component was not It is presumed that the adhesive was applied in a state in which there was hardly any intervening material. The sheet bodies of Examples 1 to 3 not only provide the effect of the liquid component over a long period of time, but also suppresses the oozing of the liquid component, and causes stains of the liquid component on articles that come into contact with the sheet body. In addition, the adhesive layer formed on the adhesive layer can be easily attached to a desired article such as a wall.

Claims (4)

Stretching while bringing a liquid component into contact with at least part of the unstretched body of the first resin layer made of a resin composition containing low-density polyethylene having a density of 0.895 to 0.925 g/cm ³ and a filler,
A method for producing a sustained-release sheet comprising forming a porous layer in which a liquid component is supported in voids formed around a filler, stretching the porous layer, and subjecting the sheet to heat relaxation treatment after the stretching. The stretching is performed using an unstretched body obtained by co-extrusion of the first resin layer and the second resin layer made of a crystalline resin composition,
2. The method for producing a sustained-release sheet according to claim 1, wherein a protective layer made of a crystalline resin composition is laminated on the porous layer. 3. The method for producing a sustained-release sheet according to claim 1, wherein the unstretched body is in the form of a cylindrical film. 4. The method for producing a sustained-release sheet according to any one of claims 1 to 3, comprising a step of laminating an adhesive layer after thermal relaxation treatment.

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