JP4299732B2 - Multilayer film made of hydrophilic porous film - Google Patents

Description

The present invention relates Ranaru multilayer film or a hydrophilic porous fill beam. Specifically, a multilayer film that shows normal white color before wetting with water (when dry) and clearing after wetting with water (when wet) so that the pattern drawn on the surface of the hydrophilic porous film can be identified from the back side. About.

  In recent years, many porous films that are effective in preventing urine leakage and diaper rash have been used as back sheets for paper diapers. This porous film has innumerable minute pores formed therein, and light is diffusely reflected at the internal interface. Therefore, the porous film shows white opacity. For this reason, when this is used for the back sheet of a paper diaper, the inside of a diaper becomes difficult to see from the outside. In particular, light colors such as urine are difficult to distinguish, and it is difficult to visually recognize whether the wearer urinated. Therefore, it is actually necessary to remove the diaper and check it by hand, resulting in inconvenience.

  Therefore, Patent Documents 1 and 2 disclose a material in which white fine particles that become transparent when water is absorbed are fixed to a hydrophilic substrate such as paper together with a resin binder. If printing is performed on the back surface of the base material, the white fine particles on the surface and the base material become transparent when wetted with water, and the printing on the back surface can be seen through. This utilizes the physical change that the refractive index of the white fine particles is close to that of water, and that when the water is wet, the irregular reflection of light on the surface of the fine particles is reduced to make it transparent.

  However, paper that is often used as a base material has a hard feel and is not preferable for applications that directly touch the skin such as a paper diaper. Moreover, since the manufacturing cost is high, it is not preferable for disposable uses such as disposable diapers. Further, for the same reason as above, there is a problem that the display area cannot be increased and the visibility is inferior.

  Therefore, the present invention provides a film-like material having a colored portion that is white before being wet (when dry), becomes transparent when wet (when wet), and is significantly more flexible than before. It is something to try. The present invention is also intended to provide a film-like material that can be obtained at a lower cost than conventional ones.

  As a result of intensive studies, the present inventors have achieved the above object by providing a partially colored pattern on one surface of a hydrophilic porous film and providing a layer for preventing water permeation on the other surface. It has been found that the present invention can be achieved.

  That is, the film-like material of the present invention is provided with a layer for preventing water permeation on the other surface of a hydrophilic porous film mainly composed of a thermoplastic resin having a colored portion on one surface. It consists of a multilayer film.

Further, the hydrophilic porous film of the present invention has 25 to 80 parts by mass of a thermoplastic resin, 75 to 20 parts by mass of a filler, 100 parts by mass of the total of the thermoplastic resin and the filler, and further has a hydrophilicity imparting agent of 0.0. The thermoplastic resin composition having 1 to 10 parts by mass is formed into a film shape and then stretched in at least one axial direction. The obtained multilayer film has a total light transmittance of less than 50% and a total light transmittance of 50% or more when wet.

  The multilayer film of the present invention has improved flexibility, is less expensive, and has a function of detecting moisture such as urine that is equivalent to a conventional product.

Hereinafter, the present invention will be described in detail.
The multilayer film of the present invention is a multilayer film in which a layer for preventing water permeation is provided on the other surface of a hydrophilic porous film mainly composed of a thermoplastic resin having a colored portion on one surface. It is.

  Examples of the thermoplastic resin include a polyester resin, a polyamide resin, and a polyolefin resin. Examples of the polyester resin include polyethylene terephthalate and polybutylene terephthalate. Examples of the polyamide resin include nylon 6, nylon 66, and the like. Can do. Of these, polyolefin resins are preferred because of their excellent flexibility.

  The polyolefin resin used in the present invention is preferably a polymer mainly composed of an olefin polymer such as ethylene, propylene, butene, pentene, hexene, vinyl acetate, or a copolymer thereof, specifically, a low density. Polyethylene, linear low density polyethylene (ethylene-α-olefin copolymer), polyethylene resin such as medium density polyethylene and high density polyethylene, polypropylene resin such as polypropylene and ethylene-propylene copolymer, poly-4-methylpentene, Examples include polybutene, ethylene-vinyl acetate copolymer, ethylene-butene copolymer, and mixtures thereof. These polyolefin resins may be a resin produced using a Ziegler catalyst or a resin produced using a single site catalyst such as a metallocene catalyst.

Of these, polyethylene resins are more preferable, and linear low density polyethylene resins and low density polyethylene, which are ethylene-α-olefin copolymers, are most preferable. The melt index of the polyolefin resin is preferably about 0.1 to 30 g / 10 min, more preferably about 0.5 to 10 g / 10 min in consideration of the moldability and stretchability of the film. The density of the polyolefin resin is preferably 0.910 to 0.940 g / cm ³ considering the flexibility of the film.

  The hydrophilic porous film used for the multilayer film of the present invention is obtained by forming a thermoplastic resin composition comprising 25 to 80 parts by mass of a thermoplastic resin and 75 to 20 parts by mass of a filler into a film and then stretching the film. Is preferred.

  As the filler, an inorganic filler or an organic filler can be used. Examples of the inorganic filler include calcium carbonate, barium sulfate, calcium sulfate, barium carbonate, magnesium hydroxide, aluminum hydroxide, zinc oxide, magnesium oxide, titanium oxide, silica, talc, and glass beads. Of these, barium sulfate and calcium carbonate are preferred. Furthermore, calcium carbonate is more preferable in consideration of inexpensiveness. As the organic filler, resin beads such as polystyrene, polymethyl methacrylate, and phenol resin are preferable.

  The composition ratio between the thermoplastic resin and the filler affects the moldability and stretchability of the film, the light transmittance when the resulting film is dry and wet, and the like. If the amount of the filler is small, the number of minute holes obtained by interfacial peeling between the thermoplastic resin and the filler is reduced, and the light transmittance during drying is increased, which is not preferable. On the other hand, if the amount of the filler is large, it is not preferable because a film is formed with poor molding or the stretchability is lowered, and sufficient stretching cannot be performed. From this viewpoint, the composition ratio of the thermoplastic resin to the filler is preferably 25 to 80% by weight for the thermoplastic resin and 75 to 20% by weight for the filler. More preferably, the thermoplastic resin is 30 to 70% by weight and the filler is 70 to 30% by weight. The average particle diameter of the filler is preferably 20 μm or less, more preferably 10 μm or less, and most preferably 0.5 to 5 μm.

  The filler may be subjected to a surface treatment to improve dispersibility with the thermoplastic resin. As the surface treatment agent, those capable of hydrophobizing the surface by coating the surface of the filler are preferable, and examples thereof include higher fatty acids such as stearic acid and lauric acid, or metal salts thereof.

  The hydrophilic porous film used for the multilayer film of the present invention is further imparted with hydrophilicity, with 25 to 80 parts by mass of thermoplastic resin and 75 to 20 parts by mass of filler, and 100 parts by mass of the total of the thermoplastic resin and filler. A thermoplastic resin composition having 0.1 to 10 parts by mass of an agent is preferably formed into a film and then stretched.

  The hydrophilic porous film is characterized in that the resin composition containing a thermoplastic resin and a filler contains a specific amount of a hydrophilicity-imparting agent, and the amount of the hydrophilicity-imparting agent depends on the light transmittance when wet. affect.

  When the addition amount of the hydrophilicity-imparting agent is small, it becomes difficult for water to penetrate into the internal pores when wetted with water, and the light transmittance when wet is lowered, which is not preferable. On the other hand, when the amount of the hydrophilicity-imparting agent added is large, the light transmittance when wet is increased, but the hydrophilicity-imparting agent bleeds out during storage or the extrusion performance is inferior. Considering this point, the hydrophilicity imparting agent addition amount is preferably 0.1 to 10 parts by weight, more preferably 0.5 to 5 parts by weight with respect to 100 parts by weight of the resin composition containing the thermoplastic resin and the filler. It is.

  Examples of the hydrophilicity-imparting agent include nonionic surfactants, anionic surfactants, and cationic surfactants. Specifically, examples of the nonionic surfactant include polyoxyethylene alkyl ethers. , Glycerin fatty acid ester, polyethylene glycol fatty acid ester, polyoxyethylene fatty acid ester, sorbitan fatty acid ester, anionic surfactant, alkyl sulfate ester salt, polyoxyethylene alkyl ether sulfate ester, cationic surfactant , Alkylamine salts and the like can be used. Among these, nonionic surfactants are preferable because they are not easily affected by other ionic substances. Furthermore, it is preferably at least one compound selected from fatty acid ester compounds in terms of easy control of hydrophilicity.

  Examples of fatty acid esters include polyhydric alcohols or esters of polypolyhydric alcohols and fatty acids. Examples of the polyhydric alcohol and polypolyhydric alcohol include glycerin, polyglycerin, sorbitan, ethylene glycol, polyethylene glycol, propylene glycol, and polypropylene glycol. Examples of the fatty acid include coconut fatty acid, beef tallow fatty acid, caprylic acid, lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, oleic acid and the like. Among the hydrophilicity imparting agents comprising the above fatty acid esters, polyethylene glycol fatty acid esters are most preferred in consideration of bleeding out of the hydrophilicity imparting agent during storage, transfer of the hydrophilicity imparting agent during use, and film formability.

  The average molecular weight of polyethylene glycol constituting the polyethylene glycol fatty acid ester affects the bleed-out of the hydrophilicity imparting agent during storage, the migration of the hydrophilicity imparting agent during use, and the film moldability. When the average molecular weight of polyethylene glycol is too low, the hydrophilicity-imparting agent tends to bleed out during storage and is not preferable because it denatures over time. In addition, the hydrophilicity imparting agent tends to migrate during use, and the hydrophilicity imparting agent is particularly washed away by moisture, and the hydrophilic agent diffuses to the surroundings. Furthermore, smoke is increased during melt extrusion, which is not preferable.

  On the other hand, when the average molecular weight of polyethylene glycol is too high, the amount of extrusion decreases and film productivity decreases, which is not preferable. Therefore, the average molecular weight of polyethylene glycol constituting the hydrophilicity-imparting agent is preferably 150 to 750, more preferably 300 to 500. The average molecular weight in the present invention can be measured by a usual method using gel permeation chromatography.

  The carbon number of the hydrocarbon group of the fatty acid constituting the polyethylene glycol fatty acid ester also affects the bleeding out of the hydrophilicity imparting agent during storage, the transfer of the hydrophilicity imparting agent during use, and the film formability. When the number of carbon atoms of the fatty acid is too small, the hydrophilicity-imparting agent tends to bleed out during storage and denatures over time, which is not preferable. In addition, the hydrophilicity imparting agent easily migrates during use, and the hydrophilicity imparting agent is washed away by moisture, and the hydrophilicity imparting agent diffuses around, which is not preferable. Furthermore, the extrusion performance is also inferior, which is not preferable. If the fatty acid has too many carbon atoms, the hydrophilicity is lowered and the wet transmittance of the present invention cannot be increased. Therefore, it is preferable that it is 12-16 as carbon number of a fatty acid, More preferably, it is 12-14.

  Specific examples of the fatty acid ester include Matsumoto Yushi Seiyaku Co., Ltd. trade names “TB-202” and “TB1259”, Riken Vitamin Co., Ltd. trade name “Riquemar O-71-DE”, and the like. If the said content is satisfy | filled, it will not be limited to these.

  The hydrophilic porous film used for the multilayer film of the present invention is not limited to the purpose of the present invention, and other stretching aids, stabilizers, antioxidants, colorants, ultraviolet absorbers, dispersants, etc. Additives may be added.

  Next, the manufacturing method of the multilayer film of this invention is illustrated. First, in order to produce a hydrophilic porous film, for example, the above-mentioned thermoplastic resin, filler, hydrophilicity-imparting agent, and other additives, if necessary, a Henschel mixer, a super mixer, a tumbler mixer, etc. After mixing, the mixture is kneaded and pelletized using a single or twin screw extruder. Next, the pellets are known at a temperature higher than the melting point of the thermoplastic resin, preferably at a melting point + 20 ° C. or higher and lower than the decomposition temperature, such as an extrusion molding machine equipped with a T die or the like, an inflation molding machine equipped with a circular die, etc. Melting and film formation using a molding machine. In some cases, the film can be formed directly with a molding machine without being pelletized.

  The formed film is formed at a temperature ranging from room temperature to the softening point of the resin (measured by a method defined in JIS K-6760) by a known method such as a roll method, a tenter method, or a gear method. A porous film is produced by stretching in at least a uniaxial direction and causing interfacial peeling between the thermoplastic resin and the filler. Stretching may be performed in one stage or may be performed in multiple stages.

  Since the draw ratio is related to the film breakage at the time of drawing and the light transmittance at the time of drying of the obtained film, it is not preferable that the draw ratio is too high or too low. From such a viewpoint, the draw ratio is preferably 1.2 to 6 times in at least one axial direction. More preferably, it is 1.4 to 5 times. In the case of biaxial stretching, a method of first stretching uniaxially in the machine direction or a direction perpendicular to the machine direction and then stretching the second axis in a direction perpendicular to the direction, or the machine direction and the direction perpendicular thereto. There is a method of performing biaxial stretching simultaneously in the forming direction. Either method is applicable.

  Moreover, after extending | stretching, in order to stabilize the form of the aperture | opening obtained as needed, you may perform a heat setting process. Examples of the heat setting treatment include a method of heat treatment for 0.1 to 100 seconds at a temperature not lower than the softening point of the resin and lower than the melting point. Further, the film may be subjected to corona treatment so that the film can be easily colored by printing or the like, and water can easily penetrate.

  The multilayer film of the present invention is partially colored on one side for visual recognition. The coloring means is not particularly limited as long as the object of the present invention can be achieved. However, it is preferably a printing process in which an increase in weight due to coloring is small. By performing the printing process on one surface, the printed pattern cannot be seen from the other side of the film when dry, but the printed pattern can be seen through when wet. Printing is not particularly limited such as flexographic printing and gravure printing, and the ink used is not limited such as solvent or water-based. The color of printing is not particularly limited, and may be a single color or multiple colors. Although there is no particular limitation on the print pattern, the solid print portion has a tendency that it is difficult for water to soak into the holes in the film from the print portion, and it takes time for transparency when wet. On the other hand, the dot printing part easily permeates water into the hole in the film even from the printing part and becomes transparent in a short time. It is preferable to adjust the solid print portion and the dot print portion according to the application. Moreover, it is also possible to give double-sided printing according to a use, and to give the functional difference with respect to water on the surface and a back surface.

  It is also effective to provide a layer made of a polymer absorber such as a polymer-absorbing polymer on the printed colored portion so that the entire surface of the film can be easily wet. The layer may be the entire surface of the film or may be partial. The layer of the polymer absorber can be provided on the printed pattern by a method of further printing using a printing machine. In that case, the entire surface may be overcoated or may be partially coated with dots. There is no particular limitation on the thickness of the layer, but when it is extremely thin, it cannot absorb water effectively, and when it is extremely thick, it is inferior in flexibility and inexpensiveness. Taking these into consideration, it is usually about 0.1 μm to 50 μm.

The multilayer film of the present invention, the colored alms surface for viewing Ru provided with a layer for preventing permeation of water on the opposite face. By providing a layer for preventing water permeation, elution of the hydrophilicity imparting agent in the film by urine can be prevented when used for visual recognition of urine and the like. When the hydrophilicity-imparting agent is eluted by urine, the urine touches a moisture-permeable porous film often used for a leak-proof film such as a diaper, and the leak-proof film is hydrophilized. There is a risk of leaking.

  Furthermore, by providing a layer that prevents permeation of water, drying of water such as urine soaked into the porous film can be prevented. When moisture is removed from the porous film by drying, the light transmittance returns to the dry state, and the printed pattern is not seen through.

  The layer that does not transmit water may form a multilayer film by a multilayer extrusion process. For example, a film made of a thermoplastic resin layer containing a filler and a hydrophilicity imparting agent and a thermoplastic resin not containing a filler in a multi-layer extrusion film forming apparatus comprising two extruders and one T-die. For example, there may be mentioned a method in which a film comprising the above layer is melt-cast and then uniaxially stretched in the machine direction between a preheating roll and a stretching roll. Further, a waterproof material may be coated on the film. For example, the method of coat | covering an acrylic resin using a roll coater etc. are mentioned.

  In addition, it is easy and inexpensive to provide a layer for printing on the entire surface of the porous film using a transparent printing ink excluding the colorant and drying to prevent water permeation. Printing is not particularly limited, such as flexographic printing or gravure printing, and the ink used is not limited, such as solvent-based or water-based. The thickness of the layer that prevents water permeation is not particularly limited, but if it is extremely thin, water permeation cannot be effectively prevented, and if it is extremely thick, it is inferior in flexibility and low cost. Taking these into consideration, the normal thickness is about 0.1 μm to 50 μm.

  The thickness of the multilayer film of the present invention is not particularly limited. However, when it is extremely thick, the light transmittance during wet operation is lowered and the flexibility and the cost are inferior. In addition, an extremely thin film is not preferable because a tear occurs when the film is formed. Taking these into consideration, the normal thickness is about 5 to 100 μm. Preferably it is 7-70 micrometers. More preferably, it is 8-50 micrometers.

The multilayer film of the present invention which is prepared as described above, the total light transmittance is less than 50% of the dry, total light transmittance in the wet is Ru near the range of 50% or more. When the light transmittance during dry is 50% or more, the difference in light transmittance between dry and wet is reduced, and it becomes difficult to perceive the difference caused by getting wet with water. Is not preferred. If the total light transmittance when wet is less than 50%, the printed pattern is difficult to see through from the back side, so it is not preferable for use for water detection. More preferably, the total light transmittance when dry is less than 45%, and the total light transmittance when wet is 55% or more. Further, the difference in total light transmittance between dry and wet is preferably 15% or more, more preferably 20% or more.

  The rigidity of the multilayer film of the present invention is 80 mm or less, and has appropriate flexibility. Therefore, it is suitably used as an application requiring flexibility, for example, a urine detection film for disposable diapers. The lower limit of rigidity is not particularly specified, but is usually about 10 mm.

  A multilayer film having such characteristics has a low total light transmittance when dry, a high total light transmittance when wet, and can be suitably used as a water detection film. Moreover, since it is highly flexible and inexpensive, it is suitable as a urine detection film such as disposable disposable diapers.

  In order to describe the present invention more specifically, examples are shown below. The present invention is not limited to these examples.

  The melt index (hereinafter referred to as MI) shown in the examples, the total light transmittance at the time of drying, the total light transmittance at the time of wetness, the film thickness, the rigidity, the transferability of the hydrophilicity imparting agent, and the drying resistance are as follows. It is the value measured and evaluated by the method.

(1) Melt index (g / 10min)
The measurement was performed under the conditions of a temperature of 190 ° C. and a load of 2160 g by the method defined in ASTM D-1238-57T (E).

(2) Total light transmittance when dry (%)
Based on the method prescribed | regulated to JISK-7105, it measured using the penetrometer (Nippon Denshoku Industries make, model | model: NDH-300A). Measure two points other than the printed pattern on one sample of the multilayer film in the machine direction (hereinafter referred to as MD direction) 50 mm and the direction perpendicular to the machine direction (hereinafter referred to as TD direction) 100 mm. The average value was calculated.

(3) Total light transmittance when wet (%)
A sample was collected in the same manner as in (2) above, and after immersing the film in pure water for 1 minute, water droplets on the surface were wiped off, and two points were measured using a densitometer. The above operation was repeated for each sample, a total of 20 points were measured, and the average value was measured.

(4) Film thickness Ten samples [MD direction: 10 cm, CD direction: 10 cm] were collected from the multilayer film, and a total of 50 measurement points in each sample were measured with respect to a total of 50 measurement points (manufactured by PEACOCK, UPRIIGHT DIAL GUAGE). No. 25) was used to measure the thickness, and the average thickness was calculated as the film thickness.

(5) Rigidity (mm)
It measured based on the method (cantilever method) prescribed | regulated to JIS-L1096. The sample used for the measurement was a film having a width of 200 mm and a length of 300 mm, wound on a 25 mm width metal scale, then withdrawing the metal scale, and the resulting flat roll (width 25 mm, length 300 mm) weighed 1 kg. It was prepared by pressing one reciprocating with a roller.

(6) Transfer of hydrophilicity imparting agent A 200 mm square porous film, a 200 mm square multilayer film of the present invention, and two 100 mm square filter papers were prepared in this order except that the hydrophilicity imparting agent was not used. Over and 5 ml of ink-colored water was dropped onto the filter paper. Then, a 10 mm square of 100 mm square was placed on the filter paper, and after 5 minutes, the bottom surface (the back surface of the porous film without a hydrophilicity-imparting agent) was visually inspected within a 100 mm square to visually observe the following: It was evaluated as follows.
○: No bleeding at all
Δ: Exudation within half of 100 mm square area,
X: Exudation over the entire surface exceeding half of a 100 mm square area.

(7) Drying resistance A transparent acrylic plate was placed on a black cardboard of A4 size, and 0.1 cc of water was dropped on it. On top of this, the surface on which the multilayer film of the present invention was printed 3 cm × 4 cm square was placed gently. The appearance of the printed pattern after 1 minute, 15 minutes, and 30 minutes was visually observed. For comparison, the multilayer film in a dry state was also observed and evaluated as follows. The temperature was 23 ° C. and the relative humidity was 50%.
○: Visible clearly
△: Vaguely seen,
X: Almost no visible.

(8) Formability Line speed of 20 m / min after stretching between a preheating roll and a stretching roll heated to 70 ° C. after melt film formation at 240 ° C. using an extruder equipped with a T-die. The situation of uniaxial stretching in the machine direction at a stretching ratio of 4.0 times was observed at, and was evaluated as follows.
○: Stable molding without film breakage or significant decrease in extrusion rate
X: Film breakage and a significant decrease in the amount of extrusion are observed, and stable molding is not possible.

[ Production Example 1]
Linear low density polyethylene LLDPE1 (manufactured by Mitsui Chemicals, Inc., trade name: Ultzex 2)
021 L, density: 0.920 g / cm ³ , melt index (MI): 2.1 g / 10
min) 38 parts by weight, branched low density polyethylene LDPE (manufactured by Mitsui Chemicals, trade name: Mirason 27, density: 0.918 g / cm ³ , MI: 2.0 g / 10 min), 2 parts by weight of filler Calcium carbonate CaCO ₃ (manufactured by Dowa Calfine Co., Ltd., trade name: SST)
−40, average particle size: 1.1 μm) 60 parts by weight, hydrophilicity imparting agent A (manufactured by Matsumoto Yushi Co., Ltd., trade name: TB-202, polyethylene glycol fatty acid ester) was mixed in a tumbler mixer. Thereafter, the mixture was uniformly kneaded at 200 ° C. using a tandem extruder and processed into a pellet. This pellet was melt-formed at 240 ° C. using an extruder equipped with a T-die, and then in the machine direction at a draw ratio of 4.0 times between a preheating roll heated to 70 ° C. and a drawing roll. Uniaxial stretching was performed to obtain a hydrophilic porous film having a thickness of 25 μm. On the one side of the film, Daiichi Seika Co., Ltd. Hydrick SK293C Blue (H) was used as ink by a center impression type flexographic printing machine, and Daiichi Seika Co., Ltd. ink solvent Hydrick SK No. 2 was used to adjust the viscosity to 20 seconds with a # 3 Zaan cup, and the printed pattern (halftone printing, 50 lines / inch, 50%) as shown in FIG. 1 was applied. The obtained porous film was measured and evaluated by the above methods for the total light transmittance when dry, the total light transmittance when wet, the rigidity, the migration of the hydrophilicity-imparting agent, the drying resistance, and the moldability. The obtained results are shown in Table 1.

[Example 1 ]
On the opposite side of the printed surface of the film produced in Production Example 1, Osaka Printing Ink Manufacturing Co., Ltd. FPOT-NWF (Medium MT Kai) was manufactured as Osaka Printing Ink Manufacturing Co., Ltd. The viscosity was adjusted to 20 seconds with a # 3 Zahn cup using No. 3 solvent for ink, and the entire surface of the film was printed (coated) with a center impression type flexographic printing machine using a convex plate. The evaluation results of the obtained multilayer film are shown in Table 1.

[Examples 2-7, Comparative Examples 1-2]
Except for changing the blending ratio (unit: parts by weight) of linear low-density polyethylene, filler, hydrophilicity-imparting agent, stretch ratio, and film thickness as shown in Table 1 or Table 2, the same manner as in Example 1 was performed. A multilayer film was produced. Each characteristic of the obtained film was measured and evaluated in the same manner as in Example 1, and the results are shown in Tables 1 and 2.

[Example 8 ]
On the printing surface of the film produced in Example 1 , as a water-absorbing polymer type coating agent, a mixture of Osaka Printing Ink Manufacturing Co., Ltd. EXP15078 (water absorption medium) and EXP15078 (curing agent) mixed at 100: 1. The film was printed (applied) on the entire surface of the film by using a center impression type flexographic printing machine using a convex plate on the entire surface. The obtained results are shown in Table 1.

[Example 9 ]
A multilayer film was obtained in the same manner as in Example 1 except that the printed surface of the film before printing obtained in Production Example 1 was subjected to corona treatment at 1 kV using a corona treatment apparatus.
The obtained results are shown in Table 1.

  The multilayer film of the present invention has improved flexibility, is less expensive, and has a function of detecting moisture such as urine that is equivalent to a conventional product. Therefore, it can be suitably applied in the fields of sanitary materials, medical materials, clothing materials, building materials, packaging materials, etc., and in particular, it is suitably used as a urine detection film for absorbent articles such as disposable diapers. be able to.

It is the schematic of the printed pattern used in the Example of this invention.

Claims (5)

Thermoplastic resin containing 25-80 parts by mass of thermoplastic resin, 75-20 parts by mass of filler, 100 parts by mass of the total of the thermoplastic resin and filler, and 0.1-10 parts by mass of a hydrophilicity-imparting agent. A hydrophilic porous film obtained by molding the composition into a film and then stretching ;
A colored portion on one surface of the hydrophilic porous film ,
A layer for preventing permeation of water on the other surface of the hydrophilic porous film ;
Provided,
A multilayer film having a total light transmittance of less than 50% when dry and a total light transmittance of 50% or more when wet . The multilayer film according to claim 1, wherein the thermoplastic resin is a polyolefin resin and the filler is calcium carbonate.   The multilayer film according to claim 1, wherein the layer for preventing water permeation is formed by applying a printing ink excluding a colorant to a hydrophilic porous film and drying it.   The multilayer film according to claim 1, wherein a layer made of a polymer absorber is provided on the colored surface. The film for water detection which consists of a multilayer film in any one of Claims 1-4 .

Images