Manufacturing method of thermoformed product, and thermoformed product with liquid-repellent film

Abstract

To provide a method for manufacturing a thermoformed article that keeps a liquid repellent characteristic even when a resin base material applied with a liquid repellent film on a surface is thermoformed, and the thermoformed article with the liquid repellent film.SOLUTION: A method for manufacturing a thermoformed article 100 includes following steps (1) and (2). Step (1) is a liquid repellent film formation step for forming a liquid repellent film 4 having an aggregate 6 of fine particles and a binder 8 on a surface of a base material 2 so that the difference between a surface tension of a resin constituting the surface of the base material 2 and a surface tension of the film of a resin constituting the binder 8 is 10 mJ / m2 or less. Step (2) is a thermoforming step for thermoforming the base material 2 with the liquid repellent film obtained in the step (1), including stretching the base material 2 with the liquid repellent film so that, in the case where a thickness of the base material 2 with the liquid repellent film before the thermoforming is defined 100%, the thickness falls within a range of maximum 60%.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for producing a thermoformed article, and to a thermoformed article provided with a liquid-repellent coating. [Background technology]

[0002] When thermoformed products are used as daily necessities or industrial products, they are required to have various functions on their surfaces. In particular, the liquid repellency of the surface has been emphasized because it prevents the contents from adhering to the container and reduces the amount of the contents remaining. For example, if a food container has poor liquid repellency, it is likely to be discarded with food still attached to its surface, which hinders food loss and the promotion of plastic recycling. In addition, when food is taken out of the container, the food attached to the container easily stains the hands, clothes, and surrounding objects. Furthermore, if a container with food remaining therein is left, various problems will occur, such as spoilage, unpleasant odors, and insects gathering.

[0003] Patent Document 1 discloses a method for imparting water repellency to a resin substrate by applying a coating material containing fine particles onto the substrate and forming a minute uneven structure on the surface of the substrate by a large number of fine particles. By using this method, a water-repellent film showing a water contact angle of 150 degrees or more can be obtained. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2018-62660 A [Patent Document 2] Patent No. 6336287 Summary of the Invention [Problem to be solved by the invention]

[0005] However, while it is acceptable if the resin substrate on which the water-repellent film has been formed is used as is in sheet form or in bag form, when the resin substrate is thermoformed into a three-dimensional shape such as a container, there is a problem that the liquid-repellent film cannot keep up with the stretching of the resin substrate that accompanies thermoforming and is damaged.

[0006] The water-repellent film of Patent Document 1 exhibits water-repellency by having an uneven structure of numerous fine particles called the Cassie-Baxter model. If this uneven structure is damaged by thermoforming, the film will no longer exhibit water-repellency.

[0007] On the other hand, there is a method (post-coating) in which a resin substrate is thermoformed in advance and a water-repellent film is formed on the surface of the thermoformed product, as described in Patent Document 2. However, post-coating generally uses a spray, and thus has many problems, such as coating processing capacity, loss of coating agent, cost of coating equipment, replacement of molds due to differences in the shapes of thermoformed products, and the need for dedicated equipment for each shape of thermoformed product.

[0008] The present invention has been made in consideration of the above problems, and aims to provide a method for producing a thermoformed product in which the liquid repellency (water contact angle of 150° or more) is maintained even when a resin substrate having a liquid repellent film on its surface is thermoformed, and to provide a thermoformed product with a liquid repellent film. [Means for solving the problem]

[0009] The inventors have been developing a method for forming a liquid-repellent film using a paint containing fine particles, a binder, and a solvent, and have discovered that if the resins constituting the substrate and the binder have good adhesion to each other, the function of the liquid-repellent film will be maintained even after thermoforming, which led to the completion of the present invention. The difference between the surface tension of the substrate and the surface tension of a film containing only the binder was used as a parameter indicating adhesion.

[0010] That is, the method for producing a thermoformed product according to the present invention is characterized in that a thermoformed product is obtained by the following steps (1) and (2). Step (1) is a liquid-repellent film formation step for forming a liquid-repellent film having fine particles and a binder on the surface of a substrate, the liquid-repellent film being formed by a resin that constitutes the surface of the substrate. Thermoplastic resin The difference between the surface tension of the binder and the surface tension of the resin film is 10 mJ / m 2 Below The resin constituting the binder is a mixture of an acrylic resin and a copolymer resin of vinyl chloride and vinyl acetate, or a chlorinated polyolefin. and Step (2) is a thermoforming step in which the substrate with the liquid-repellent film obtained in step (1) is thermoformed, and the substrate with the liquid-repellent film is stretched so that the thickness of the substrate with the liquid-repellent film before thermoforming is 100% and the thickness of the substrate with the liquid-repellent film before thermoforming is within the range of up to 60% (preferably within the range of 80% to 60%).

[0011] By producing a thermoformed product by such a method, the liquid-repellent film on the surface of the substrate can maintain liquid-repellency (contact angle of water is 150° or more) even after thermoforming.

[0012] Here, in the thermoforming step, pressure forming or vacuum pressure forming may be performed.

[0013] The thermoformed product with a liquid-repellent film according to the present invention is The present invention comprises a substrate and a liquid-repellent film formed on a surface of the substrate, the liquid-repellent film includes fine particles and a binder; The difference between the surface tension of the resin constituting the surface of the substrate and the surface tension of the resin film constituting the binder is 10 mJ / m 2 is as follows: The substrate with the liquid-repellent film is stretched by thermoforming so that the thickness falls within a range of up to 60% (preferably within a range of 80% to 60%), with the thickness of the substrate with the liquid-repellent film before thermoforming being 100%.

[0014] Here, the liquid-repellent film is After the thermoforming It is preferable that the substrate has an exposed region that exposes the surface of the substrate and satisfies the following conditions (1) and (2). Condition (1) The length of each shape of the exposed region is less than 50 μm; and Condition (2): The individual shapes of the exposed regions do not include a circle having a diameter of 12 μm. The shape of the exposed area is determined by analyzing microscopic images of the peeling of the liquid-repellent film, etc.

[0015] The binder is preferably an acrylic resin. and salt Vinyl chloride and vinyl acetate copolymer resins , or chlorinated polyolefin It is also possible to use the following.

[0016] Moreover, the materials of the fine particles and the binder may be selected such that the difference in solubility parameter (SP value) between them is not less than 1 and not more than 4. Moreover, the fine particles may be hydrophobic silica particles, and the binder may be a thermoplastic resin.

[0017] The thermoformed article with a liquid-repellent film according to the present invention is characterized in that it is a container packaging material, i.e., the thermoformed article according to the present invention is suitable for packaging or containers for food, cosmetics, medicines, etc. [Brief description of the drawings]

[0018] [Figure 1] FIG. 1 is a schematic diagram for explaining a method for manufacturing a thermoformed product according to one embodiment, in which (A) shows the state of a liquid-repellent paint, (B) shows the cross-sectional structure of a resin member for thermoforming, and (C) shows the cross-sectional structure of a thermoformed product with a liquid-repellent film. [Diagram 2] FIG. 1 is a diagram showing a cross-sectional structure of a thermoformed product in which the liquid-repellent film contains coarse particles. [Diagram 3] 1A and 1B are explanatory diagrams of a manufacturing example using a vacuum and pressure molding device, in which (A) shows the process of heating a resin member for thermoforming, and (B) shows the process of vacuum suction using a vacuum pump and a plug. [Figure 4] FIG. 11 is an explanatory diagram of a manufacturing example using a vacuum and pressure molding device, and (C) shows a step of completing the vacuum suction by further using compressed air. [Diagram 5](A) is a schematic diagram of the cross-sectional structure of a thermoformed product with a liquid-repellent film, showing cracks, peeling, and falling off that occur in the thermoformed product, (B) is a schematic diagram of a void that occurs in the liquid-repellent film, and (C) is a schematic diagram of a cross-section of a long, narrow void caused by the rapid growth of a crack. [Figure 6] FIG. 2 is a front view of three types of thermoformed products (lids) used in the examples. [Figure 7] FIG. 2 is a diagram showing positions for measuring the thickness of a thermoformed product (lid) in the examples. [Figure 8] 4 shows microscopic images of the surfaces of thermoformed articles of Example 1 and Comparative Example 2 before and after molding. [Figure 9] 3 is a microscopic image of the surfaces of the thermoformed articles of Example 1 and Comparative Example 2 after molding. [Figure 10] 4 shows microscopic images of the surfaces of thermoformed articles of Example 2 and Comparative Example 1 before and after molding. [Figure 11] 4 is a microscopic image of the surfaces of the thermoformed articles of Example 2 and Comparative Example 1 after molding. [Figure 12] Enlarged images of each microscopic image in Figure 8. [Figure 13] Enlarged images of each microscopic image in Figure 9. [Figure 14] Enlarged images of each microscopic image in Figure 10. [Figure 15] Enlarged images of each microscopic image in Figure 11. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] One embodiment of a thermoformed product according to the present invention will be described in order with reference to FIG. 1 showing the manufacturing process thereof.

[0020] 1. Liquid repellent paint Liquid-repellent paint consists of fine particles, a binder, and a solvent, as shown in Figure 1(A). The fine particles may be either organic or inorganic, but it is preferable that the surface is hydrophobic. In the case of organic fine particles, acrylic beads, olefin beads, etc. can be used. In the case of inorganic fine particles, silica, alumina, titania, zirconia, etc. can be used. Silica fine particles are particularly suitable.

[0021] The average primary particle size of the fine particles is not particularly limited, but is preferably within the range of 5 nm to 300 nm, and more preferably within the range of 10 nm to 200 nm. The fine particles moderately aggregate in the coating material to form secondary particles (aggregates), and have a fine uneven structure of nano-order in which a plurality of fine particles are linked. By coating, these aggregates are distributed on the surface of the substrate, and an uneven structure with excellent liquid repellency is formed. The average particle size of the aggregates of the fine particles is also preferably within the range of 5 nm to 300 nm, and more preferably within the range of 10 nm to 200 nm.

[0022] These average particle sizes were determined by analyzing images of the fine particles observed under an electron microscope, measuring the equivalent circle diameter, and calculating the number-based average particle size.

[0023] It is also preferable to use hydrophobic silica formed by subjecting the surfaces of silica fine particles to a hydrophobic treatment, for example, a method of coating the surfaces of silica fine particles with polydimethylsiloxane.

[0024] In order to reinforce the liquid repellency due to the aggregates of fine particles, it is preferable to include coarse particles with a larger average particle size. There is no limitation on the average particle size, but it is preferably within the range of 1 μm to 20 μm, and more preferably within the range of 3 μm to 7 μm. The average particle size of the coarse particles is calculated by analyzing the images of the fine particles observed under an optical microscope, measuring the circle equivalent diameter, and calculating the average particle size based on the number.

[0025] The binder serves to connect the aggregates of fine particles to the surface of the substrate, and is preferably a thermoplastic resin. Examples of thermoplastic resins that can be used include polystyrene resin, polyester resin, modified polyolefin (chlorinated polypropylene resin, etc.), acrylic resin, urethane resin, amino resin, cellulose resin, vinyl chloride resin, and polyamide. In particular, a blend resin of acrylic and vinyl chloride-vinyl acetate copolymer is preferable.

[0026] The solvent is not particularly limited as long as it can dissolve the binder and disperse the fine particles. For example, water, alcohols such as ethanol, isopropyl alcohol, and n-butyl alcohol, ethyl acetate, toluene, and methyl ethyl ketone can be used as the solvent.

[0027] In preparing the coating material, the ratio of the fine particles to the binder is not particularly limited, but is preferably 25:75% by mass to 55:45% by mass, and more preferably 35:65% by mass to 45:55% by mass. When coarse particles are mixed into the coating material, the ratio of the coarse particles is preferably 30 to 100 parts by mass per 100 parts by mass of the binder.

[0028] 2. Resin components for thermoforming 1(B) shows, as an example, a cross-sectional view of a resin member 10 provided with a liquid-repellent film 4. This resin member 10 has a laminated structure consisting of a resin base material 2 and a liquid-repellent film 4 formed by coating on the surface thereof, and is characterized by its excellent thermoforming properties and the ability to retain liquid repellency even after thermoforming.

[0029] The substrate 2 is not particularly limited, but in consideration of productivity, it is preferable that the substrate 2 has a shape with a flat surface, such as a film, a sheet, or a plate-like member. Depending on the thickness of the substrate 2, the substrate 2 is classified into a film (1 to 200 μm), a sheet (200 μm to 1 mm), and a plate-like member (1 mm or more). When the substrate is a film or a sheet, it is not limited to a single layer, and may be a laminate of multiple layers.

[0030] The surface of the substrate 2 is preferably made of a resin composition containing a thermoplastic resin. The thermoplastic resin is not particularly limited, but one or more of polyester, polyolefin, polystyrene, nylon, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, acrylonitrile butadiene styrene copolymer, ethylene vinyl acetate copolymer, polyacetal, polymethyl methacrylate, methacrylic styrene copolymer, cellulose acetate, polyurethane, polycarbonate, polyethylene terephthalate (PET), etc. are used.

[0031] This embodiment is characterized in that the adhesion between the substrate 2 and the binder 8 contained in the liquid-repellent film 4 is specified. That is, the difference between the surface tension of the resin constituting at least the surface of the substrate 2 and the surface tension of the film consisting only of the resin constituting the binder 8 is 10 mJ / m 2 It is preferable that:

[0032] In this embodiment, the difference in solubility parameter (SP value) between the fine particles and the binder may be 1 or more and 4 or less.

[0033] The liquid-repellent film 4 is formed by applying the above-mentioned liquid-repellent paint to the surface of the substrate 2 by a general application method. For example, by using roll coating such as a gravure printing machine, the paint can be applied to the sheet-like substrate in a manner similar to continuous printing, which is highly productive. After the paint is applied, the paint is dried to volatilize the solvent in the paint, forming the liquid-repellent film. The drying method may be a general method. For example, heated drying using hot air or the like is highly productive.

[0034] The coating thickness of the paint is not particularly limited, but it is preferable that the liquid-repellent film 4 after drying has a thickness of 0.1 to 20 μm, and more preferably 1 to 5 μm.

[0035] 1(B), the liquid-repellent film 4 includes aggregates 6 of a plurality of fine particles and a binder 8 connecting these aggregates 6 to the surface of the substrate 2. The projection-like aggregates 6 are distributed on the surface of the substrate 2, forming a fine uneven structure, which can exhibit liquid repellency.

[0036] In order to improve the adhesion between the substrate 2 and the liquid-repellent film 4, the coating may be divided into two steps. For example, a paint containing no fine or coarse particles but a binder may be applied to the substrate as a base coat, and then a liquid-repellent paint may be applied to the surface of the base coat to form the liquid-repellent film 4. Alternatively, the base coat paint may contain coarse particles so that the base coat layer forms a large uneven structure due to the coarse particles, and a small uneven structure due to aggregates 6 of fine particles may be formed on the surface. When the coating is divided into two steps, the binder of the base coat paint is usually the same as that of the liquid-repellent paint, but a different binder may be used. However, if the difference between the surface tension of the resin of the substrate and the surface tension of the binder of the base coat paint is less than 10 mJ / m 2 The following shall be used: Do.

[0037] 3.Thermoformed products FIG. 1(C) shows an example of a thermoformed product 100 produced by thermoforming a resin member 10. This is a schematic diagram showing a case where the substrate 2 is stretched by thermoforming and the thickness of the resin member 10 is reduced to 60 to 70%. The liquid-repellent film 4 is deformed with the stretching of the substrate 2, and the intervals between the aggregates 6 of the fine particles are uniformly expanded. With such deformation, the intervals between the aggregates 6 do not become too large. Even if an area where the surface of the substrate 2 is exposed occurs in the intervals between the aggregates 6, the intervals can be small, and the liquid repellency of the liquid-repellent film 4 is maintained. FIG. 2 shows a schematic cross section of a thermoformed product 102 in which the liquid-repellent film 14 contains coarse particles 12 as another embodiment.

[0038] There are many methods for thermoforming, but the resin member 10 having the liquid-repellent film 4 of this embodiment is particularly suitable for a method in which it is softened by heating, then compressed air is applied to a mold, or in addition, it is molded by vacuum suction. The softening process is generally performed by heating the resin member 10 to a temperature range equal to or higher than the glass transition temperature (Tg) and lower than the melting point (Tm) of the resin of the base material 2.

[0039] As a thermoforming method, pressure forming and vacuum pressure forming are preferred in terms of mold reproduction accuracy. Pressure forming is a molding method in which compressed air is sent to the opposite side of the sheet to pressurize the heated and softened sheet-like resin member 10 so that it adheres closely to the mold, thereby forming the resin member 10 into a three-dimensional shape corresponding to the shape of the mold. Vacuum pressure forming is almost the same as pressure forming, but it is a molding method in which the sheet is vacuum-suctioned at the same time as pressure forming, making it possible to form more complex shapes. Vacuum pressure forming methods include the plug assist-pressure method and the vacuum snapback method.

[0040] 3 and 4 show schematic diagrams of a plug-assist type vacuum / pressure molding device as an example. Based on these figures, the molding process of a cup-shaped thermoformed product 100 will be described. First, as shown in FIG. 3(A), Process 1 A continuous sheet-like resin member 10 is inserted between the upper and lower electric heaters 20 with the liquid-repellent film facing upward, and is heated to soften it. Process 2 The softened portion of the resin member 10 is fed to a position between the mold 30 and the plug 60. Process 3 The resin member 10 is clamped by the mold 30 and the clamp member 40.

[0041] Next, as shown in Figure 3(B), Process 4 The vacuum pump 50 exhausts the air from the recess of the mold 30 and suctions the resin member 10. The recess of the mold 30 has many fine vacuum holes, and the resin member 10 deforms so as to be recessed toward the surface of the recess of the mold 30. At the same time, a convex plug 60 is lowered to push the resin member 10 downward. This plug 60 functions as an auxiliary mold.

[0042] Next, as shown in Figure 4(C), Process 5 Compressed air is sent into the gap between the plug 60 and the resin member 10 to assist the vacuum suction. The surface of the protruding part of the plug 60 has many fine holes for the compressed air, from which the compressed air is ejected. Through these operations, the resin member 10 is brought into close contact with the recessed part of the mold 30, and is molded into a three-dimensional shape according to the shape of the mold. Process 6 After molding, the plug 60 is raised, and after the molded product 100 has cooled, air is sent into the recess using the vacuum holes in the mold 30 to release the molded product 100. Finally, unnecessary portions are cut off, and the molded product 100 is removed.

[0043] During steps 3 to 6, the next part to be molded is softened by the electric heater 20 and sent to a position between the mold 30 and the plug 60, whereby the thermoformed product 100 can be repeatedly manufactured.

[0044] As described above, the thermoformed product 100 of this embodiment is formed by forming a liquid-repellent film 4 on the substrate 2 using a liquid-repellent paint (FIG. 1(A)), and then thermoforming the resin member 10 (FIG. 1(B)). As described above, the substrate 2 stretches in a softened state due to thermoforming, so ideally, the liquid-repellent film 4 also stretches in the same manner following the stretching of the substrate 2 (FIG. 1(C)).

[0045] In reality, however, the liquid-repellent film 4 on the surface of the thermoformed product cannot completely follow the stretching of the substrate 2, and as shown in Figure 5(A), cracks occur in the binder 8, peeling occurs between the binder 8 and the fine particle agglomerates 6, and the fine particle agglomerates 6 fall off (including the fall off of the coarse particles 12 in Figure 2).

[0046] If the degree of cracking, peeling, or falling off is small, the liquid repellency of the surface of the thermoformed product will be maintained, but if the range of each crack, peeling, or falling off becomes large, the presence rate of fine particles per unit area of ​​the surface of the thermoformed product will decrease significantly, resulting in voids in the liquid repellent film. Here, areas that have grown to the extent that they cause a discontinuance in liquid repellency are called voids in the liquid repellent film.

[0047] Figures 5(B) and (C) show examples where the liquid repellency is interrupted after thermoforming. Figure 5(B) shows a state where the cracks, peeling, and falling off have become large, resulting in the formation of voids 6A. In voids 6A, the surface of substrate 2 no longer retains the liquid repellent film, and the surface of substrate 2 is exposed. Note that the example in Figure 5(C) shows a case where there is an unevenness in the retention of the liquid repellent film by substrate 2, and even if the degree of stretching of substrate 2 is small, cracks and peeling suddenly become large, resulting in the formation of elongated voids 6B.

[0048] The inventors considered that even when a resin member 10 having a liquid-repellent film 4 applied to the surface of a substrate 2 is thermoformed to produce a three-dimensional thermoformed product 100, in order to maintain the liquid-repellent properties of the surface, the following requirements (1) to (3) are important. (1) Strong adhesion between the substrate and binder (2) The binder has high deformability when softened. (3) Strong affinity between the binder and the fine particles

[0049] In this embodiment, focusing on the requirement (1), the difference between the surface tension of the resin of the substrate 2 and the surface tension of the film of only the resin constituting the binder 8 is 10 mJ / m 2 The materials are selected as follows, so that the adhesion between the two is strong and the liquid repellency of the liquid repellent film 4 is maintained even after thermoforming.

[0050] In addition, regarding requirement (2), by using for the binder 8 a resin (thermoplastic resin) that has good extensibility in a softened state, cracks are less likely to occur when the liquid-repellent film 4 follows the stretching of the substrate 2, which has a positive effect on maintaining the liquid repellency of the liquid-repellent film 4.

[0051] Regarding requirement (3), by selecting the materials of the binder 8 and the microparticles 6 so that the difference in SP value between them is 1 or more and 4 or less, it is possible to prevent the microparticles 6 from falling off the binder 8 due to the stretching during thermoforming, and this has a positive effect on maintaining the liquid repellency of the liquid-repellent film 4. EXAMPLES

[0052] Example 1 <Preparation of liquid-repellent paint> Hydrophobic silica particles (average primary particle size 10 nm, average secondary particle size 100-200 nm) were used as the fine particles. A blend resin of acrylic and vinyl chloride-vinyl acetate copolymer, which are thermoplastic resins, was used as the binder. Coarse silica particles with an average particle size of 6 μm were used as the coarse particles. Methyl ethyl ketone and ethyl acetate were used as the solvent in a ratio of 40:60-45:55. The fine particles were mixed in a ratio of 5 mass %, binder 6.3 mass %, coarse particles 3.8 mass %, and solvent 85 mass %, and the mixture was stirred to uniformly dissolve and disperse, producing a liquid-repellent paint.

[0053] Here, the blend resin of acrylic and vinyl chloride-vinyl acetate copolymer was prepared in such amounts that the solubility parameter (SP value) measured by the following measurement method was 10.2. That is, the SP value (δ) was calculated by turbidity point titration according to SUH, CLARKE et al. [Reference: SUH, CLARKE, JPSA-1, 5, 1671-1681 (1967)]. The formula for calculating the SP value is shown in the following formula. Here, Vmh is the volume of the good solvent, δmh is the SP value of the good solvent, Vml is the volume of the poor solvent, and δml is the SP value of the poor solvent.

[0054]

number

[0055] <Preparation of resin parts for thermoforming> A-PET sheet (thickness 400 μm) manufactured by OJK Corporation was used as the resin substrate. A liquid-repellent paint was applied to this resin substrate using a bar coater so that the dry film thickness was 1 μm (application amount 1.00 g / m 2 ) and then dried at 50°C for 1 minute to produce a resin member with a liquid-repellent film.

[0056] <Making thermoformed products> The shapes of the thermoformed products to be produced are three types of countertop beverage lids as shown in Figure 6. They all have the same circular frame diameter of 92.5 mm at the bottom, but different heights of 19 mm, 40 mm, and 60 mm.

[0057] A vacuum and compressed air molding machine is used for thermoforming. First, the resin part with the liquid-repellent film is softened by radiant heating until it can be thermoformed. Radiant heating is a method of heating the resin part with infrared rays radiated by a heater. Next, the softened resin part is subjected to vacuum and compressed air molding using a mold and plug to obtain a thermoformed product. By changing the depth of the mold, covers with three different heights were formed. The set temperatures of the upper and lower heaters and the sheet surface temperature for each shape are shown in Table 1.

[0058] [Table 1]

[0059] Comparative Example 1 As in Example 1, the substrate was a PET sheet, and the liquid-repellent coating contained hydrophobic silica particles and coarse silica particles. However, chlorinated polyolefin, a thermoplastic resin, was used as the binder, and methyl ethyl ketone and toluene were used in a specified ratio as the solvent. The liquid-repellent coating was produced by mixing 5.4% by mass of fine particles, 5.4% by mass of binder, 3.2% by mass of coarse particles, and 86% by mass of solvent, and dissolving and dispersing them uniformly by stirring. The coating amount was 1.14 g / m 2 Let us assume that.

[0060] Example 2 A CPP sheet (thickness 400 μm) was used as the resin substrate. The liquid-repellent paint was prepared with the same blending amount as in Comparative Example 1, and the coating amount was 1.14 g / m 2 In Comparative Example 1 and Example 2, the set temperatures of the upper and lower heaters and the sheet surface temperature for each shape are shown in Table 2.

[0061] [Table 2]

[0062] Comparative Example 2 A CPP sheet (thickness 400 μm) was used as the resin substrate. The liquid-repellent paint was prepared with the same blending amount as in Example 1, and the coating amount was 1.00 g / m 2 Let us assume that.

[0063] Example 3 The procedure was the same as in Example 1, except that a blend resin of acrylic and vinyl chloride-vinyl acetate copolymer prepared in such amounts that the SP value was 10.0 was used as the binder.

[0064] Comparative Example 3 The resin substrate was changed from a PET sheet to a CPP sheet, but the rest was the same as in Example 3.

[0065] <Evaluation method> The properties of the thermoformed products obtained were evaluated according to the following methods, and the results are shown in Tables 3 and 4.

[0066] Residual thickness of resin material The thickness (I1) of the side of the lid after thermoforming was measured. The measurement points are indicated by symbols 7-A and 7-B in FIG. 7. The residual ratio (I1 / I0×100) was calculated based on the thickness (I0) before thermoforming. For Comparative Example 1, the flat part indicated by symbol 7-C in FIG. 7 was also added to the measurement points. The residual ratio of the thickness of the flat part is larger than that of the side, making it possible to evaluate in a range where the residual ratio is high. The thickness before and after thermoforming was measured using a micrometer.

[0067] Liquid repellency Using a contact angle meter CA-DT (Kyowa Interface Science Co., Ltd.), a 10 microliter (μL) drop of pure water was dropped onto the surface of the liquid-repellent film on the inside of the side of the lid-shaped molded product, and the contact angle was measured immediately after. Contact angles of 150 degrees or more were evaluated as having liquid repellency (○), and those less than 150 degrees were evaluated as not having liquid repellency (×).

[0068] <Overall Judgment> A rating of "◯" indicates that the liquid repellency was maintained even when the thickness was reduced to approximately 60% by thermoforming, with the thickness before thermoforming being taken as 100%.

[0069] In addition, Examples 1 and 2 are thermoformed products that can exhibit liquid repellency even when the residual thickness rate is low (60 to 70%), but the thermoformed products of the present invention also include thermoformed products that can maintain liquid repellency when the residual thickness rate is 70 to 80%.

[0070] Considering the degree of freedom in the shape of the thermoformed product, it is preferable for the thermoformed product to be able to maintain liquid repellency even when the remaining thickness is at least 70 to 80%. Therefore, the judgment "x" indicates that the product could not maintain liquid repellency under the condition that the remaining thickness is 70 to 80%.

[0071] [Table 3]

[0072] [Table 4]

[0073] As shown in Tables 3 and 4, in Example 1, even when the resin member was thermoformed to a 60 mm high thermoformed product with a thickness residual rate of 64.3%, the water contact angle was 150 degrees or more, and the excellent liquid repellency before thermoforming was maintained. Similarly, in Example 2, excellent liquid repellency was maintained in a 60 mm high thermoformed product with a thickness residual rate of 60.8%. Similarly, in Example 3, excellent liquid repellency was maintained in a 60 mm high thermoformed product with a thickness residual rate of 74.0%.

[0074] On the other hand, in Comparative Example 1, even in a thermoformed product having a height of 19 mm and a thickness remaining rate of 82.5%, the water contact angle was less than 150 degrees, and the liquid repellency before thermoforming was not maintained. In a thermoformed product having a height of 60 mm and a thickness remaining rate of 60.8%, the water contact angle decreased to 143 degrees. Similarly, in Comparative Example 2, in a thermoformed product having a height of 19 mm and a thickness remaining rate of 72.3%, the water contact angle was 147 degrees, and the liquid repellency was not maintained. In a thermoformed product having a height of 60 mm and a thickness remaining rate of 61.5%, the water contact angle decreased to 138 degrees. Similarly, in Comparative Example 3, in a thermoformed product having a height of 19 mm and a thickness remaining rate of 88.5%, the water contact angle was 148 degrees, and the liquid repellency was not maintained. In a thermoformed product having a height of 60 mm and a thickness remaining rate of 73.0%, the water contact angle decreased to 142 degrees.

[0075] [Table 5]

[0076] Table 5 shows the residual rate calculated from the thickness of flat portion 7-C in Fig. 7 and the water contact angle at that portion for the thermoformed product of Comparative Example 1. The residual rate of the thickness of the flat portion is 86 to 88%, and in this range where stretching due to thermoforming is small, the water contact angle is 150 degrees or more, and the excellent liquid repellency before thermoforming is maintained.

[0077] The surface tension of the resin constituting the substrate surface and the surface tension of a film consisting only of the resin constituting the binder were measured by the following method.

[0078] Here, we adopt a method based on Kitahara-Hata theory to measure the surface free energy, i.e., surface tension, of a solid (resin film) using three types of liquids with known surface free energies. According to Kitahara-Hata theory, the surface tension γ of liquids and solids is expressed as the sum of three surface free energy components (dispersion, polarity, and hydrogen bonding) as shown in formula (2). Table 6 also shows the surface free energy components (γ d ,γ p ,γ h ) are known values. γ = γ d +γ p +γ h (2)

[0079] [Table 6]

[0080] From the Kitahara-Hata and extended Foulkes equations, the interfacial free energy γ SL is the surface free energy component of the solid (γ S d ,γ S p ,γ S h ) and surface tension γ S and the surface free energy component of the liquid (γ L d ,γ L p ,γ L h ) and surface tension γ L Furthermore, the Young-Dupre equation leads to equation (4). θ is the contact angle when a drop of liquid is placed on the surface of a solid.

[0081]

number

[0082]

number

[0083] Equation (4) contains the surface free energy components (γ L d ,γ L p ,γ L h ) and surface tension γ L By substituting the known values ​​of and the measured contact angles θ of the three types of liquids on the solid surface, we obtain a set of simultaneous linear equations with three unknowns, which give the surface free energy components of the solid (γ Sd ,γ S p ,γ S h ) is calculated, and the surface tension of the solid γ S is obtained.

[0084] Based on the above method for measuring the surface tension of a solid, the surface tension of the substrate and the surface tension of the binder in each of the examples and comparative examples were measured. The contact angles θ of the three types of liquids are shown in Table 7, and the calculated surface tension γ S are shown in Table 8.

[0085] [Table 7]

[0086] [Table 8]

[0087] In addition, for each resin of the substrate and binder, the work of adhesion W SL is shown in Table 9.

[0088]

number

[0089] [Table 9]

[0090] There is a correlation between the judgment results of the presence or absence of liquid repellency after thermoforming shown in Tables 3 and 4 and the difference in surface tension between the base material and binder based on Table 8, in that if the difference in surface tension is 10 or less, the judgment result will be ``O'' (high liquid repellency with a water contact angle of 150° or more is maintained even after thermoforming), and if the difference in surface tension exceeds 10, the judgment result will be ``X'' (Table 10).

[0091] [Table 10]

[0092] From the above, it was found that in the case of a combination of materials with good adhesion in which the difference in surface tension between the substrate and binder is 10 or less, even if a resin part with a liquid-repellent film is thermoformed so that the thickness retention rate is in the range of approximately 60 to 80%, the water contact angle will remain at 150 degrees or more, and good liquid repellency sufficient for practical use will be maintained.

[0093] 8 to 15 are microscope images of the liquid-repellent films before and after thermoforming in Examples 1 and 2 and Comparative Examples 1 and 2. The marks "◯" and "×" attached to each image indicate the evaluation results of the presence or absence of liquid repellency.

[0094] In Figures 8 and 9, images of Example 1 and Comparative Example 2, both of which use "acrylic and vinyl chloride-vinyl acetate copolymer" as the binder, are lined up. In both images A1 and B1 before thermoforming in Figure 8, it can be seen that the particles that make up the liquid-repellent film are neatly and orderly present. In contrast, comparing images A2 and B2 at a height of 19 mm after thermoforming, it can be seen that the particles are neatly and orderly present in Example 1, but crack-like voids have occurred in Comparative Example 2. Comparing images A3 and B3 at a height of 40 mm after thermoforming in Figure 9, it can be seen that particles have only fallen off in some small places in Example 1, but the width of the voids has widened and become longer in Comparative Example 2. Comparing images A4 and B4 at a height of 60 mm after thermoforming, it can be seen that the number of places where particles have fallen off in small places has increased in Example 1, while the elongated voids have become larger and longer in Comparative Example 2.

[0095] In Fig. 10 and Fig. 11, images of Example 2 and Comparative Example 1, both of which use "chlorinated polyolefin" as the binder, are arranged side by side. In Fig. 10, images C1 and D1 before thermoforming show that the particles that make up the liquid-repellent film are neatly and orderly present in both cases. In contrast, comparing images C2 and D2 at a height of 19 mm after thermoforming, it can be seen that the particles are neatly and orderly present in Example 2, but voids (slightly larger particles falling off) have occurred in some places in Comparative Example 1. Comparing images C3 and D3 at a height of 40 mm after thermoforming in Fig. 11, it can be seen that some small cracks, peeling, or falling off have occurred in Example 2, while voids (areas where large particles have fallen off and the substrate surface is exposed) have occurred like large holes in Comparative Example 1. Comparing images C4 and D4 at a height of 60 mm after thermoforming, it can be seen that there is only an increase in small cracks, peeling, or falling off in Example 2, while large and numerous voids have occurred in Comparative Example 1.

[0096] Images D1 to D4 of Comparative Example 1 were analyzed to measure the shape of the exposed area on the substrate surface. The maximum inner diameter of each opening in the exposed area (for example, the major axis length in the case of an ellipse) was measured. In the liquid-repellent film before thermoforming (Image D1), there were no openings with an inner diameter exceeding 12 μm, and the maximum inner diameter was 11.5 μm. In the liquid-repellent film with a height of 19 mm after thermoforming (Image D2), many openings had an inner diameter of 12 or more, and the maximum inner diameter was 20.1 μm.

[0097] A relatively large opening was selected from the liquid-repellent film with a height of 40 mm after thermoforming (Image D3), and the maximum and minimum inner diameters of each opening (for example, the long axis length and short axis length if elliptical) were measured. In Image D3, the maximum inner diameter was 91 μm and the minimum inner diameter was 33 μm. Similarly, for the liquid-repellent film with a height of 60 mm after thermoforming (Image D4), the maximum inner diameter was 111 μm and the minimum inner diameter was 22 μm.

[0098] Additionally, the shapes of the exposed areas on the substrate surface were measured by image analysis of Images B1 to B4 of Comparative Example 2. The length (linear distance between both ends of the crack) and width of each crack in the exposed areas were measured, and it was found that the cracks that occurred in the liquid-repellent film before thermoforming (Image B1) were in the range of 24 to 47 μm in length and 3 to 4 μm in width.

[0099] In contrast, the liquid-repellent film with a height of 19 mm after thermoforming (Image B2) had many cracks with lengths ranging from 48 to 131 μm and widths ranging from 7 to 16 μm. The liquid-repellent film with a height of 40 mm after thermoforming (Image B3) had many cracks with lengths ranging from 74 to 142 μm and widths ranging from 12 to 24 μm. The greater the stretching caused by thermoforming, the longer and wider the cracks tended to become. Furthermore, the liquid-repellent film with a height of 60 mm after thermoforming (Image B4) had many cracks with lengths ranging from 29 to 85 μm and widths ranging from 17 to 29 μm. Elliptical cracks were also observed.

[0100] 12 to 15 are images obtained by enlarging the images (500 times) of FIG. 8 to FIG. 11 to 2000 times. For example, in the image a4 of Example 1 at a height of 60 mm in FIG. 13, multiple areas that appear to be cracks, peeling, or falling off are found, but none of the openings are large enough to fit a circle with a diameter of 12 μm. In addition, there are no areas with a length of 50 μm or more. In contrast, in the image b2 of Comparative Example 2 at a height of 19 mm in FIG. 12, the occurrence of elongated voids with a length of 50 μm or more is observed. In the images b3 and b4 of FIG. 13, the width of such voids is larger.

[0101] Also, in the image c4 of Example 2 at a height of 60 mm in FIG. 15, multiple areas that appear to be cracks, peeling, or falling off are found, but none of the openings are large enough to fit a circle with a diameter of 12 μm. Also, there are no areas with a length of 50 μm or more. In contrast, in the image d2 of Comparative Example 1 at a height of 19 mm in FIG. 14, the occurrence of voids large enough to fit a circle with a diameter of 12 μm is observed. Images d3 and d4 in FIG. 15 show that there are voids large enough to fit a circle with a diameter of more than 22 μm. [Explanation of symbols]

[0102] 2 Base material 4,14 Liquid repellent film 6. Aggregation of fine particles 8. Binder 10. Resin parts for thermoforming 12. Large silica particles 20 Electric heater 30-inch 40 Clamping member 50 Vacuum Pump 60 Plug 100,102 Thermoformed products

Claims

1. A method for producing a thermoformed product, comprising the following steps (1) and (2): Step (1) is a liquid-repellent film formation step of forming a liquid-repellent film having fine particles and a binder on the surface of a substrate, the difference between the surface tension of the thermoplastic resin constituting the surface of the substrate and the surface tension of the resin film constituting the binder being 10 mJ / m ２ The resin constituting the binder is a mixture of an acrylic resin and a copolymer resin of vinyl chloride and vinyl acetate, or a chlorinated polyolefin. Step (2) is a thermoforming step of thermoforming the substrate with the liquid-repellent film obtained in step (1), in which the substrate with the liquid-repellent film is stretched so that the thickness of the substrate with the liquid-repellent film before thermoforming falls within a range of 80% to 60%, with the thickness being taken as 100%.

2. 2. The method for producing a thermoformed product according to claim 1, wherein the thermoforming step comprises performing pressure forming or vacuum pressure forming.

3. A thermoformed product comprising a substrate and a liquid-repellent film formed on a surface of the substrate, the liquid-repellent film includes fine particles and a binder; The difference between the surface tension of the thermoplastic resin constituting the surface of the substrate and the surface tension of the resin film constituting the binder is 10 mJ / m ２ is as follows: the resin constituting the binder is a mixture of an acrylic resin and a copolymer resin of vinyl chloride and vinyl acetate, or a chlorinated polyolefin; A thermoformed product with a liquid-repellent film is characterized in that the thickness of the substrate with the liquid-repellent film before thermoforming is taken as 100%, and the substrate with the liquid-repellent film is stretched by thermoforming so that the thickness falls within the range of 80% to 60%.

4. 4. The thermoformed product with a liquid-repellent film according to claim 3, characterized in that the liquid-repellent film has an exposed area that exposes the surface of the substrate after the thermoforming, and satisfies the following conditions (1) and (2). Condition (1) The length of each shape of the exposed region is less than 50 μm. Condition (2) The shape of each of the exposed regions does not include a circle having a diameter of 12 μm.

5. 5. The thermoformed article with a liquid-repellent film according to claim 3, wherein the difference in solubility parameter between the fine particles and the resin constituting the binder is 1 or more and 4 or less.

6. 6. The thermoformed article with a liquid-repellent film according to claim 3, wherein the fine particles are hydrophobic silica particles.

7. 7. The thermoformed product with a liquid-repellent film according to claim 3, which is a container packaging material.

Images