Thermoplastic film capable of changing color when encountering water as well as preparation method and application of thermoplastic film

Abstract

The invention particularly discloses a thermoplastic film capable of changing color when encountering water as well as a preparation method and application thereof. The thermoplastic film capable of changing color when encountering water comprises a base film, and a color developing layer and a disappearance layer which are respectively arranged on two opposite sides of the base film, the thickness ratio of the color developing layer to the base film to the disappearing layer is (1-10): (100-200): (1-20); the base membrane is prepared from the following raw materials in percentage by weight: 30 to 95 percent of polyolefin and 1 to 10 percent of hydrophilic agent; the hydrophilic agent comprises a first hydrophilic compound and a second hydrophilic compound; the first hydrophilic compound comprises at least one of a polyether-polyolefin copolymer, a polyvinyl alcohol-polyolefin copolymer and polyvinyl alcohol; the second hydrophilic compound comprises at least one of polyacrylic acid and a modifier thereof, polyacrylate and a modifier polyamide thereof, and a modifier thereof. The disposable water-absorbing product has the advantages that the storage stability of the disappearance layer of the disposable water-absorbing product is improved, the adhesion stability between the disappearance layer and the base film is improved, and the color can be changed thoroughly when encountering water.

Description

Technical Field

[0001] The invention relates to the technical field of waterproof thermoplastic films, in particular to a thermoplastic film that changes color when in contact with water, and a preparation method and application thereof. Background Art

[0002] It is difficult for users or caregivers of disposable absorbent products to judge the use of disposable absorbent products during use, and it is also difficult to confirm whether the absorbent core in the disposable absorbent products is in a state of absorption saturation in a timely manner. In order for users to use health care products more effectively, a means should be designed to convey the use, relative level or degree of disposable absorbent products to users or caregivers during the use of disposable absorbent products, such as a color indicator that causes the product to change color.

[0003] In the prior art, a color indicator is often coated on the surface of a base film to form a color change area to prepare a disposable absorbent product; when in use, the color change area on one side of the base film coated with the color indicator comes into contact with the liquid, thereby causing a color change, and the use of the disposable absorbent product is judged by the color change effect.

[0004] The color change effect of the commonly used color indicators is mainly achieved by changing the pH value or adjusting the physical water content; some problems are gradually exposed during use; first, the color indicator based on the pH color change mechanism is easily affected by the environmental humidity. When the storage environment before use is not appropriate, it is easy to change color in advance, and the color change is irreversible, making the product unable to be used normally; second, the color indicator based on the pH color change mechanism cannot be personalized with the design of pattern or shape, and can only be made into a specific shape (generally a rectangle), and the specific color change effect makes it impossible to personalize the color design; third, the color indicator is generally combined with hydrophilic ink to form a hydrophilic slurry coated on the surface of the base film, and the base film of the disposable absorbent product has a strong water repellency. In actual use, it will also cause the liquid to be unable to penetrate to the location of the color indicator in time after contacting the base film, so that the color change of the area where the color indicator is located is not complete, reducing the accuracy of the user's judgment of the use of the disposable absorbent product; fourth, the hydrophilic slurry made by the color indicator generally combined with the hydrophilic ink has poor spreading performance on the surface of the water-repellent base film, and the degree of adhesion between the base film and the base film after molding is poor. The disposable absorbent products currently available on the market cannot solve the above problems well. Summary of the invention

[0005] In order to improve the adhesion stability between the color indicator and the base film in disposable absorbent products and the thoroughness of the color change when exposed to water, the present application provides a water-changing thermoplastic film and a preparation method and application thereof.

[0006] In a first aspect, the present application provides a water-discoloring thermoplastic film, which adopts the following technical solution:

[0007] A water-discoloring thermoplastic film comprises a base film and a color-developing layer and a disappearing layer respectively arranged on opposite sides of the base film; the thickness ratio of the color-developing layer, the base film and the disappearing layer is 5-20:50-100:10-20;

[0008] The base film comprises the following raw materials according to weight percentage: 30%-95% of polyolefin and 1%-10% of hydrophilic agent;

[0009] The hydrophilic agent comprises a first hydrophilic compound and a second hydrophilic compound, and the mass ratio of the first hydrophilic compound to the second hydrophilic compound is 1-3:1;

[0010] The first hydrophilic compound includes at least one of polyether-polyolefin copolymers, polyvinyl alcohol-polyolefin copolymers, and polyvinyl alcohol; the second hydrophilic compound includes at least one of polyacrylic acid and its modified products, polyacrylate and its modified products.

[0011] The present invention can introduce hydrophilic hydroxyl and carboxyl groups into the base film by introducing a hydrophilic agent into the base film, thereby realizing hydrophilic modification of the base film. On the one hand, when the base film on one side of the disappearing layer contacts urine (water), the improved hydrophilicity of the base film helps to increase the diffusion degree of water in urine on the surface of the base film, so that the water can quickly diffuse to the position of the disappearing layer, improve the thoroughness of the disappearance of the disappearing layer, and enable the user to timely discover the color change effect produced by the cooperation of the color-developing layer and the disappearing layer; on the other hand, in the present invention, the first hydrophilic compound and the second hydrophilic compound work together to improve the hydrophilicity of the base film without affecting the adhesion and bonding strength between the color-developing layer and the base film; this is because the addition of the first hydrophilic compound also introduces a -CH2 group into the base film, and the water repellency of the -CH2 group enables the slurry forming the color-developing layer to maintain a good brushing and leveling effect on the surface of the base film, thereby ensuring the bonding stability between the base film and the disappearing layer and the color-developing layer.

[0012] In addition, since the base film itself has a certain degree of whiteness, it may affect the user's observation of the color change effect of the thermoplastic film before and after it comes into contact with water; the hydrophilic agent added in the present invention can improve the pore structure of the base film to reduce the whiteness of the base film, thereby improving the user's intuitive observation of the color change of the water-changing thermoplastic film before and after it comes into contact with water; and, by controlling the ratio of the thickness of the color-developing layer, the base film and the disappearing layer, the user can timely observe the intuitive visual effect of the sudden color change of the thermoplastic film before and after it comes into contact with water.

[0013] Preferably, the shapes of the disappearing layer and the color developing layer in the base film include circle, star, triangle, heart and the like.

[0014] Preferably, the base film further comprises the following raw materials in terms of weight percentage: 0.1%-0.5% antioxidant and 0.1%-5% desiccant.

[0015] Preferably, the base film further comprises the following raw materials in terms of weight percentage: 3%-65% of inorganic particles.

[0016] Preferably, the base film further comprises the following raw materials in terms of weight percentage: 15%-55% of inorganic particles.

[0017] On the one hand, hydrogen bonds are formed between the inorganic particles and the hydrophilic agent. The existence of hydrogen bonds can not only improve the adhesion between the disappearing layer and the base film, but also improve the flexibility and strength of the base film. On the other hand, the inorganic particles can promote the formation of tiny holes in the base film, increase the light transmittance of the base film, that is, improve the transparency of the base film, making it easier for users to observe the color change of the disappearing layer and the color layer in the base film.

[0018] Preferably, the inorganic particles include at least one of glass microspheres, silicon dioxide, wollastonite powder and modified products thereof; and the particle size of the inorganic particles is 0.3-5 μm.

[0019] Preferably, a wax layer is provided between the base film and the color development layer, the wax layer comprises a wax-like substance, and the mass proportion of the wax-like substance in the wax layer is 20%-45%.

[0020] Preferably, the wax layer also includes varnish.

[0021] The present invention arranges a wax layer between the color-developing layer and the base film. On the one hand, the molecular weight of the wax-like substance in the wax layer is relatively small and has a certain penetration effect. After the wax layer is applied on the base film, it can penetrate through the micropores in the base film. When the micropores of the base film are penetrated by small molecular substances, the light transmittance of the base film can be improved to improve the transparency of the base film, which helps users observe the color changes of the disappearing layer and the color-developing layer before and after they meet water. On the other hand, the wax layer can also improve the fluidity of the color-developing slurry and improve the flatness of the color-developing layer.

[0022] Preferably, the ratio of the thickness of the wax layer to the thickness of the base film is 5-10:50-100.

[0023] By controlling the thickness of the wax layer, a sufficient amount of wax can penetrate into the base film, thereby improving the light transmittance of the base film. In addition, the setting of the wax layer will not have too much impact on the setting of the subsequent color development layer, thereby avoiding the wax layer being too thick to affect the bonding degree between the color development layer and the base film, thereby improving the storage stability of the color development layer and preventing it from being scratched, thereby affecting the color change effect during subsequent use.

[0024] Preferably, the waxy substance comprises at least one of fatty acid, fatty acid salt, polyethylene wax, polypropylene wax, polyoxyethylene wax, maleic anhydride-modified polyethylene, and maleic anhydride-modified polypropylene.

[0025] Preferably, the molecular weight of the wax is 2000-4000 Da.

[0026] By selecting waxes with the above molecular weight, the wax molecules can penetrate into the micropores generated during the stretching process of the base film as much as possible, significantly improving the light transmittance enhancement effect of the wax on the base film, and improving the water retention performance of the base film, which helps to improve the thoroughness of the disappearing layer disappearing when exposed to water.

[0027] Preferably, the surface tension of the side of the base film on which the wax layer is disposed is 36-56 N / m.

[0028] By adjusting the dyne value of the surface of the base film on the side where the wax layer contacts the color-developing layer, the negative impact of the wax layer coating on the bonding strength between the base film and the color-developing layer can be reduced, and the color-developing layer can be prevented from peeling off from the surface of the wax layer, thereby significantly improving the adhesion of the color-developing layer to the surface of the base film coated with the wax layer.

[0029] In a second aspect, the present application provides a method for preparing a water-discoloring thermoplastic film, which adopts the following technical solution:

[0030] A method for preparing a water-discoloring thermoplastic film comprises the following steps:

[0031] S1, blending raw materials constituting the base film to obtain plastic particles;

[0032] S2, extruding the plastic particles and subjecting them to steps including preheating, stretching, shaping, and cooling to obtain the base film;

[0033] S3, printing the slurry for forming the disappearing layer on the surface of the base film, and forming the disappearing layer after drying; applying the slurry for forming the wax layer on the surface of the base film, and performing corona treatment on the surface of the base film coated with the wax layer after drying;

[0034] S4, printing the slurry for forming the disappearing layer on the surface of the base film opposite to the disappearing layer, and forming the color developing layer after drying, so as to obtain the water-discoloring thermoplastic film.

[0035] Preferably, the slurry forming the color development layer is at least one of solvent-based ink and UV ink.

[0036] Preferably, the slurry for forming the vanishing layer comprises the following raw materials by mass percentage: 10%-70% water-soluble acrylic resin, 1%-30% water-soluble color powder, 20%-40% water, 0.1%-1% leveling agent, and 0.1%-1% antibacterial agent.

[0037] Preferably, during the corona treatment process, the output power is controlled to be 4-8 kW.

[0038] By controlling the output power during the corona treatment, on the one hand, the chemical bonds of the plastic molecules are broken and degraded, increasing the surface roughness and contact surface area of ​​the base film; and the discharge operation during the corona treatment will also produce a large amount of ozone, which is a strong oxidant that can oxidize plastic molecules and produce carbonyl and peroxide groups with strong polarity, thereby increasing the surface energy of the base film, which is helpful to improve the firmness of the disappearing layer and the color developing layer to the base film. On the other hand, corona treatment under this condition can reduce the embrittlement effect of corona treatment on the base film, so that the base film can maintain good flexibility; and when the base film is corona treated under this condition, since the base film contains hydrogen bonds formed by the action of inorganic particles and hydrophilic agents, hydrogen bonds can improve the flexibility and strength of the base film to a certain extent, the embrittlement effect of corona treatment on the base film under this condition can be weakened by the hydrogen bonds in the base film, thereby ensuring the flexibility of the base film after corona treatment.

[0039] In a third aspect, the present application provides an application of a water-discoloring thermoplastic film in a disposable absorbent product, using the following technical solution:

[0040] The invention discloses an application of a water-discoloring thermoplastic film in disposable absorbent products.

[0041] Preferably, the disposable absorbent products include diapers, diapers, diaper pads and the like. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 It is a schematic structural diagram of the thermoplastic film that changes color when exposed to water according to the present invention.

[0043] Explanation of the accompanying reference numerals: 1. water-discoloring thermoplastic film; 2. base film; 3. disappearing layer; 4. color developing layer. DETAILED DESCRIPTION

[0044] For better understanding and implementation, the technical solution of the present invention will be clearly and completely described below in conjunction with embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments.

[0045] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0046] Unless otherwise indicated, all numerical values ​​expressing quantities of ingredients, reaction conditions, and so forth used in the specification and claims are to be understood as modified by the term “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth herein are approximations that can vary depending upon the desired properties desired to be obtained.

[0047] As used herein, "and / or" means one or all of the mentioned elements.

[0048] As used herein, “including” and “comprising” encompasses the case where only the stated elements are present as well as the case where there are other elements other than the stated elements.

[0049] All percentages in the present invention are by weight, unless otherwise specified.

[0050] Unless otherwise indicated, "a", "an", "an" and "the" used in this specification are intended to include "at least one" or "one or more". For example, "a component" means one or more components, so more than one component may be considered and may be employed or used in the implementation of the embodiment.

[0051] Example 1

[0052] A water-discoloring thermoplastic film comprises a base film and a color developing layer and a disappearing layer respectively arranged on two opposite sides of the base film; the thickness ratio of the color developing layer, the base film and the disappearing layer is 1:160:1.

[0053] The base film comprises the following raw materials by weight percentage: 95% of polyolefin, 1% of hydrophilic agent (polyvinyl alcohol-polyolefin copolymer and polyacrylate and modified products thereof in a mass ratio of 2:1), 0.1% of antioxidant, and 3.9% of desiccant;

[0054] The color developing layer is obtained by drying the color developing slurry, and the color developing slurry is a solvent-based ink;

[0055] The disappearing layer is obtained by drying the aqueous slurry, and the aqueous slurry includes the following raw materials by weight: 50% of water-soluble acrylic resin, 26% of water-soluble color powder, 22% of water, 1% of leveling agent, and 1% of antibacterial agent;

[0056] A water-discoloring thermoplastic film is prepared by the following steps:

[0057] S1, blending raw materials constituting the base film to obtain plastic particles;

[0058] S2, after extruding the plastic particles, preheating and stretching at 80° C. (stretching ratio is 5 times), shaping at 90° C., and cooling at 30° C. to obtain a base film;

[0059] S3, printing the aqueous slurry on the surface of the base film to form a vanishing layer after drying;

[0060] S4, printing a color developing paste on the surface of the base film opposite to the disappearing layer, and forming a color developing layer after drying, that is, obtaining a water-discoloring thermoplastic film.

[0061] The water-chromic thermoplastic film of the present embodiment is applied in diapers; specifically, the urine-displaying color-changing process of the water-chromic thermoplastic film of the present embodiment is as follows: before urine-wetting, the vanishing layer is yellow, the color-developing layer is blue, and the visual pattern effect presented by the superposition of yellow and blue of the vanishing layer and the color-developing layer is green; after urine-wetting, the water-soluble color powder in the vanishing layer contacts with urine and is dissolved by urine, and the yellow element gradually disappears as it diffuses in water, leaving only the blue color of the color-developing layer, that is, the color change before and after urine-wetting is from green to blue, which visually produces a color-changing effect and serves as a reminder for replacement.

[0062] Example 2

[0063] A water-discoloring thermoplastic film comprises a base film and a color developing layer and a disappearing layer respectively arranged on two opposite sides of the base film; the thickness ratio of the color developing layer, the base film and the disappearing layer is 10:200:10.

[0064] The base film comprises the following raw materials by weight percentage: 86% of polyolefin, 10% of hydrophilic agent (polyvinyl alcohol-polyolefin copolymer and polyacrylate and modified products thereof in a mass ratio of 3:1), 0.1% of antioxidant, and 3.9% of desiccant;

[0065] The color developing layer is obtained by drying the color developing slurry, and the color developing slurry is a solvent-based ink;

[0066] The disappearing layer is obtained by drying the aqueous slurry, and the aqueous slurry includes the following raw materials by weight: 50% of water-soluble acrylic resin, 20% of water-soluble color powder, 29% of water, 0.5% of leveling agent, and 0.5% of antibacterial agent;

[0067] A water-discoloring thermoplastic film is prepared by the following steps:

[0068] S1, blending raw materials constituting the base film to obtain plastic particles;

[0069] S2, after extruding the plastic particles, preheating and stretching at 80° C. (stretching ratio is 5 times), shaping at 90° C., and cooling at 30° C. to obtain a base film;

[0070] S3, printing the aqueous slurry on the surface of the base film to form a vanishing layer after drying;

[0071] S4, printing a color developing paste on the surface of the base film opposite to the disappearing layer, and forming a color developing layer after drying, that is, obtaining a water-discoloring thermoplastic film.

[0072] The water-chromic thermoplastic film of the present embodiment is applied in diapers; specifically, the urine-displaying color-changing process of the water-chromic thermoplastic film of the present embodiment is as follows: before being wetted with urine, the vanishing layer is yellow, the color-developing layer is red, and the visual pattern effect presented by the superposition of yellow and red of the vanishing layer and the color-developing layer is orange; after being wetted with urine, the water-soluble color powder in the vanishing layer contacts with urine and is dissolved by urine, and the yellow element gradually disappears as the urine diffuses, leaving only the red color of the color-developing layer, that is, the color change before and after being wetted with urine is from orange to red, which visually produces a color-changing effect and serves as a reminder for replacement.

[0073] Example 3

[0074] A water-discoloring thermoplastic film comprises a base film and a color developing layer and a disappearing layer respectively arranged on two opposite sides of the base film; the thickness ratio of the color developing layer, the base film and the disappearing layer is 5:100:20.

[0075] The base film comprises the following raw materials by weight percentage: 89.5% of polyolefin, 6% of hydrophilic agent (polyvinyl alcohol-polyolefin copolymer and polyacrylate and modified product thereof in a mass ratio of 1:1), 0.5% of antioxidant and 4% of desiccant;

[0076] The color developing layer is obtained by drying the color developing slurry, and the color developing slurry is a solvent-based ink;

[0077] The disappearing layer is obtained by drying the aqueous slurry, and the aqueous slurry includes the following raw materials by weight: 60% of water-soluble acrylic resin, 9% of water-soluble color powder, 30% of water, 0.5% of leveling agent, and 0.5% of antibacterial agent;

[0078] A water-discoloring thermoplastic film is prepared by the following steps:

[0079] S1, blending raw materials constituting the base film to obtain plastic particles;

[0080] S2, after extruding the plastic particles, preheating and stretching at 80° C. (stretching ratio is 5 times), shaping at 90° C., and cooling at 30° C. to obtain a base film;

[0081] S3, printing the aqueous slurry on the surface of the base film to form a vanishing layer after drying;

[0082] S4, printing a color developing paste on the surface of the base film opposite to the disappearing layer, and forming a color developing layer after drying, that is, obtaining a water-discoloring thermoplastic film.

[0083] The water-chromic thermoplastic film of the present embodiment is applied in diapers; specifically, the urine-displaying color-changing process of the water-chromic thermoplastic film of the present embodiment is as follows: before being wetted with urine, the vanishing layer is red, the color-developing layer is blue, and the visual pattern effect presented by the superposition of red and blue of the vanishing layer and the color-developing layer is purple; after being wetted with urine, the water-soluble color powder in the vanishing layer contacts with urine and is dissolved by urine, and the red element gradually disappears as the urine diffuses, leaving only the blue color of the color-developing layer, that is, the color change before and after being wetted with urine is from purple to blue, which visually produces a color-changing effect and serves as a reminder for replacement.

[0084] Example 4

[0085] The difference between this embodiment and embodiment 1 is that the base film further includes inorganic particles; in terms of weight percentage, the base film includes the following raw materials: 43% polyolefin, 55% inorganic particles (silicon dioxide with a particle size of 0.3-5 μm), 1% hydrophilic agent, 0.1% antioxidant, and 0.9% desiccant;

[0086] The other steps and conditions are the same as those in Example 1.

[0087] Example 5

[0088] The difference between this embodiment and embodiment 2 is that the base film further includes inorganic particles; in terms of weight percentage, the base film includes the following raw materials: 71% polyolefin, 15% inorganic particles (glass microbeads with a particle size of 0.3-5 μm), 10% hydrophilic agent, 0.1% antioxidant, and 3.9% desiccant;

[0089] The other steps and conditions are the same as those in Example 2.

[0090] Example 6

[0091] The difference between this embodiment and embodiment 3 is that the base film further includes inorganic particles; in terms of weight percentage, the base film includes the following raw materials: 60% polyolefin, 29.5% inorganic particles (silicon dioxide with a particle size of 0.3-5 μm), 6% hydrophilic agent, 0.5% antioxidant, and 4% desiccant;

[0092] The other steps and conditions are the same as those in Example 3.

[0093] Example 7

[0094] The difference between this embodiment and embodiment 4 is that a wax layer is further provided between the base film and the color development layer of the thermoplastic film. The wax layer comprises the following raw materials in terms of weight percentage: 65% varnish and 35% wax (fatty acid with a molecular weight of 2000-3000Da); the ratio of the thickness of the wax layer to the thickness of the base film is 8:70;

[0095] A water-discoloring thermoplastic film is prepared by the following steps:

[0096] S1, blending raw materials constituting the base film to obtain plastic particles;

[0097] S2, after extruding the plastic particles, preheating and stretching at 80° C. (stretching ratio is 5 times), shaping at 90° C., and cooling at 30° C. to obtain a base film;

[0098] S3, printing an aqueous slurry on the surface of the base film to form a vanishing layer after drying; applying a slurry to form a wax layer on the surface of the base film, and after drying, performing a corona treatment on the surface of the base film coated with the wax layer (the output power during the corona treatment process is 4.5 kW), so that the surface tension of the side of the base film on which the wax layer is provided is 45 N / m;

[0099] S4, printing a color developing paste on the surface of the base film opposite to the disappearing layer, and forming a color developing layer after drying, that is, obtaining a water-discoloring thermoplastic film.

[0100] The other steps and conditions are the same as those in Example 4.

[0101] Example 8

[0102] The difference between this embodiment and embodiment 5 is that a wax layer is further provided between the base film and the color development layer of the thermoplastic film. The wax layer comprises the following raw materials in terms of weight percentage: 80% varnish and 20% wax (polyethylene wax with a molecular weight of 3000-4000Da); the ratio of the thickness of the wax layer to the thickness of the base film is 5:100;

[0103] A water-discoloring thermoplastic film is prepared by the following steps:

[0104] S1, blending raw materials constituting the base film to obtain plastic particles;

[0105] S2, after extruding the plastic particles, preheating and stretching at 80° C. (stretching ratio is 5 times), shaping at 90° C., and cooling at 30° C. to obtain a base film;

[0106] S3, printing an aqueous slurry on the surface of the base film to form a vanishing layer after drying; applying a slurry to form a wax layer on the surface of the base film, and after drying, performing a corona treatment on the surface of the base film coated with the wax layer (the output power during the corona treatment is 8 kW) until the surface tension of the wax layer is 56 N / m;

[0107] S4, printing a color developing paste on the surface of the base film opposite to the disappearing layer, and forming a color developing layer after drying, that is, obtaining a water-discoloring thermoplastic film.

[0108] The other steps and conditions are the same as those in Example 5.

[0109] Example 9

[0110] The difference between this embodiment and embodiment 6 is that a wax layer is further provided between the base film and the color development layer of the thermoplastic film. The wax layer comprises the following raw materials in terms of weight percentage: 60% varnish and 40% wax (polypropylene wax with a molecular weight of 2500-3500Da); the ratio of the thickness of the wax layer to the thickness of the base film is 10:50;

[0111] A water-discoloring thermoplastic film is prepared by the following steps:

[0112] S1, blending raw materials constituting the base film to obtain plastic particles;

[0113] S2, after extruding the plastic particles, preheating and stretching at 80° C. (stretching ratio is 5 times), shaping at 90° C., and cooling at 30° C. to obtain a base film;

[0114] S3, printing an aqueous slurry on the surface of the base film to form a vanishing layer after drying; applying a slurry to form a wax layer on the surface of the base film, and after drying, performing a corona treatment on the surface of the base film coated with the wax layer (the output power during the corona treatment is 6 kW) until the surface tension of the wax layer is 36 N / m;

[0115] S4, printing a color developing paste on the surface of the base film opposite to the disappearing layer, and forming a color developing layer after drying, that is, obtaining a water-discoloring thermoplastic film.

[0116] The other steps and conditions are the same as those in Example 6.

[0117] Example 10

[0118] The difference between this embodiment and embodiment 6 is that the ratio of the thickness of the wax layer to the thickness of the base film is adjusted to 1:110 while the thickness of the base film remains unchanged;

[0119] The other steps and conditions are the same as those in Example 6.

[0120] Embodiment 11

[0121] The difference between this embodiment and embodiment 6 is that the ratio of the thickness of the wax layer to the thickness of the base film is adjusted to 15:40 while the thickness of the base film remains unchanged;

[0122] The other steps and conditions are the same as those in Example 6.

[0123] Example 12

[0124] The difference between this embodiment and embodiment 6 is that the molecular weight of the wax in the wax layer is 8000Da;

[0125] The other steps and conditions are the same as those in Example 6.

[0126] Embodiment 13

[0127] The difference between this embodiment and embodiment 6 is that, in the process of preparing the water-discoloring thermoplastic film, the output power during the corona treatment in S3 is 2.5 kW;

[0128] The other steps and conditions are the same as those in Example 6.

[0129] Comparative Example 1

[0130] The difference between this comparative example and Example 1 is that an equal weight of polyolefin is used to replace the hydrophilic agent in Example 1;

[0131] The steps and conditions are consistent with those in Example 1.

[0132] Comparative Example 2

[0133] The difference between this comparative example and Example 1 is that the thickness ratio of the color developing layer, the base film and the disappearing layer is 1:300:30;

[0134] The steps and conditions are consistent with those in Example 1.

[0135] Test Method

[0136] 1. Test method for the disappearance time of the vanishing layer

[0137] The disappearance time of the disappearing layer on the thermoplastic film in the above-mentioned embodiment and comparative example was tested, and the specific test steps were as follows:

[0138] (1) Using the thermoplastic film in diapers;

[0139] (2) Add 250 ml of saline to the diaper core;

[0140] (3) Immediately after adding the saline solution, a 3.5 kg weight was placed on the diaper core and the sample was placed on a transparent glass table. The color change of the urine display pattern of the diaper could be observed from under the table.

[0141] (4) While placing the weight, press the stopwatch to start recording the time;

[0142] (5) Observe the process of the vanishing layer diffusing from the pattern and being absorbed by the core, and record the time when the vanishing layer completely separates from the pattern to reveal the color of the non-vanishing layer, which is the vanishing time of the vanishing layer. The test results are recorded in Table 1.

[0143] 2. Opacity Test

[0144] The opacity of the thermoplastic films in the above examples and comparative examples was tested using a Hunter ColorFlex EZ spectrophotometer. The test results are recorded in Table 1.

[0145] 3. Adhesion Test

[0146] 1.1 The adhesion test between the vanishing layer and the base film adopts the following steps:

[0147] (1) Pull open the test tape (3M#600) and stick it on the surface of the base film of the printed disappearing layer of the above-mentioned embodiment and comparative example to be tested, and press back and forth on the sticking place ten times to remove bubbles;

[0148] (2) Tear up one end of the test tape a little to make it enough to grip one end of the test tape, and then quickly pull off the tape at an angle of about 90° relative to the base film (the time from applying to tearing off the test tape must be less than one minute);

[0149] (3) Visually inspect whether the adhesive surface of the test tape is clean and transparent, and confirm the shedding area of ​​the disappearing layer;

[0150] (4) Calculate the residual rate of the disappearing layer on the surface of the base film and record the calculation results in Table 1.

[0151] 1.2 The adhesion test between the color developing layer and the base film adopts the following steps:

[0152] (1) Pull open the test tape (3M#600) and stick it on the surface of the base film of the printed color development layer of the above-mentioned embodiment and comparative example to be tested, and press back and forth on the sticking place ten times to remove bubbles;

[0153] (2), (3), and (4) are the same as in 1.1.

[0154] Table 1

[0155]

[0156] Combining Examples 1-3, Comparative Examples 1-2 and Table 1, it can be seen that the present invention can not only introduce hydrophilic carboxyl and hydroxyl groups to improve the hydrophilicity of the base film by introducing the first hydrophilic agent and the second hydrophilic agent into the base film, but also enable water to diffuse rapidly to the position of the disappearing layer, so that the disappearing layer disappears completely. At this time, the user can clearly observe the color change of the thermoplastic film; at the same time, the water repellency of the -CH2 and CH2 groups can be introduced so that the slurry forming the color developing layer can still maintain a good brushing and leveling effect on the surface of the base film, avoiding the negative impact of the introduction of the hydrophilic group on the adhesion between the color developing layer and the base film. In addition, the present invention can help users clearly observe the color change of the thermoplastic film before and after water absorption by controlling the ratio of the thickness of the disappearing layer, the color developing layer and the base film in the thermoplastic film, and shorten the time for the disappearance of the disappearing layer when it encounters water as much as possible.

[0157] In combination with Example 1, Examples 4-6 and Table 1, it can be seen that in the present invention, by adding inorganic particles to the base film, the hydrogen bonds on the surface of the inorganic particles can form hydrogen bonds with the hydrophilic compounds, which can not only improve the flexibility of the base film, but also further improve the adhesion stability between the base film and the disappearing layer; and, the introduction of inorganic particles can also generate tiny pores in the base film, which helps to improve the transparency of the base film to a certain extent.

[0158] In combination with Examples 4-6, Examples 7-9 and Table 1, it can be seen that in the present invention, by introducing a wax layer between the disappearing layer and the base film, the small molecular wax-like substances in the wax layer can gradually penetrate into the micropores of the base film, thereby improving the light transmittance of the base film, and further improving the light transmittance of the thermoplastic film under the coordinated action of the color development layer, the disappearing layer and the base film, so that the user can clearly observe the color change effect of the thermoplastic film before and after contacting water.

[0159] In combination with Example 6, Examples 10-12 and Table 1, it can be seen that when the ratio of the thickness of the wax layer to the base film is too small, the thickness of the wax layer is too small, and the amount of wax is low. At this time, the number of wax molecules that penetrate into the micropores of the base film is not enough, and the effect of improving the light transmittance of the base film is limited; and when the ratio of the thickness of the wax layer to the base film is too large, the thickness of the wax layer is too large. Although a sufficient number of waxes can penetrate into the base film at this time, which will be beneficial to the improvement of the transparency of the base film, the excessive thickness of the wax layer will affect the adhesion of the disappearing layer on the surface of the base film, which is manifested as a decrease in the residual rate of the color developing layer on the surface of the base film; and it will also affect the transparency of the base film to a certain extent.

[0160] When the molecular weight of the wax is too high, it is not conducive to the wax molecules to play a penetrating role in the basement membrane, which will limit the improvement of the transparency of the basement membrane by the wax molecules to a certain extent.

[0161] In combination with Example 6, Example 13 and Table 1, it can be seen that by controlling the output power during the corona treatment process to remain within an appropriate range, the base film of the wax-coated layer can be adjusted to obtain a suitable surface tension, thereby reducing the effect of the wax layer setting on the adhesion strength between the color-developing layer and the base film.

[0162] The above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the protection scope of the present invention. Although the present invention is described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the technical solutions of the present invention can be modified or equivalently replaced, but these modifications or replacements are all within the protection scope of the present invention.

Claims

1. A water-discoloring thermoplastic film, characterized in that: It comprises a base film and a color developing layer and a disappearing layer respectively arranged on opposite sides of the base film; the thickness ratio of the color developing layer, the base film and the disappearing layer is 1-10:100-200:1-20; The base film comprises the following raw materials according to weight percentage: 30%-95% of polyolefin and 1%-10% of hydrophilic agent; The hydrophilic agent comprises a first hydrophilic compound and a second hydrophilic compound, and the mass ratio of the first hydrophilic compound to the second hydrophilic compound is 1-3:1; The first hydrophilic compound includes at least one of polyether-polyolefin copolymers, polyvinyl alcohol-polyolefin copolymers, and polyvinyl alcohol; the second hydrophilic compound includes at least one of polyacrylic acid and its modified products, polyacrylate and its modified products.

2. The water-discolorable thermoplastic film according to claim 1, characterized in that: The base film further comprises the following raw materials in terms of weight percentage: 3%-65% of inorganic particles.

3. The water-discolorable thermoplastic film according to claim 2, characterized in that: The inorganic particles include at least one of glass microspheres, silicon dioxide, wollastonite powder and modified products thereof; the particle size of the inorganic particles is 0.3-5 μm.

4. The water-discolorable thermoplastic film according to claim 1, characterized in that: A wax layer is arranged between the base film and the color development layer. The wax layer includes a wax-like substance, and the mass proportion of the wax-like substance in the wax layer is 20%-45%.

5. The water-discolorable thermoplastic film according to claim 4, characterized in that: The ratio of the thickness of the wax layer to the thickness of the base film is 5-10:50-100.

6. The water-discolorable thermoplastic film according to claim 4, characterized in that: The waxy substance includes at least one of fatty acid, fatty acid salt, polyethylene wax, polypropylene wax, polyoxyethylene wax, maleic anhydride modified polyethylene, and maleic anhydride modified polypropylene.

7. The water-discoloring thermoplastic film according to claim 4, characterized in that: The molecular weight of the wax is 2000-4000Da.

8. The water-discolorable thermoplastic film according to any one of claims 4 to 7, characterized in that: The surface tension of the side of the base film where the wax layer is disposed is 36-56 N / m.

9. The method for preparing a water-discolorable thermoplastic film according to any one of claims 1 to 8, characterized in that: The steps include: S1, blending raw materials constituting the base film to obtain plastic particles; S2, extruding the plastic particles and subjecting them to steps including preheating, stretching, shaping, and cooling to obtain the base film; S3, printing the slurry for forming the disappearing layer on the surface of the base film, and forming the disappearing layer after drying; applying the slurry for forming the wax layer on the surface of the base film, and performing corona treatment on the surface of the base film coated with the wax layer after drying; S4, printing the slurry for forming the disappearing layer on the surface of the base film opposite to the disappearing layer, and forming the color developing layer after drying, so as to obtain the water-discoloring thermoplastic film.

10. Use of the hydrochromic thermoplastic film according to any one of claims 1 to 8 in disposable absorbent products.

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