Antifogging resin sheet and secondary molding thereof

Abstract

To provide an antifogging resin sheet difficult to cause whitening of an appearance while showing excellent antifogging property in an antifogging resin sheet in which a sucrose stearic acid ester and a sucrose palmitic acid ester are used.SOLUTION: On at least one surface of a thermoplastic resin sheet, an antifogging layer made of a sucrose stearic acid ester of 80% or more of a monoester and a sucrose palmitic acid ester of 80% or more of a monoester is formed.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to an anti-fogging resin sheet for use in food packaging containers and various other containers, and to a secondary molded product thereof. [Background technology]

[0002] Resin sheets extruded from various thermoplastic resins are heated and molded into secondary forms using a vacuum forming machine, a compressed air vacuum forming machine, a hot plate compressed air forming machine, etc., and the secondary molded products obtained are widely used for packaging lightweight food packaging containers and other items. Among these resin sheets, transparent resin sheets such as polystyrene, polyethylene terephthalate, polypropylene, etc. are widely used as lid materials for lunch boxes, side dish containers, etc., due to their transparency. However, these lid materials have a problem in that the inner surface of the lid material becomes cloudy due to water vapor generated from the contents.

[0003] As a means for solving the above problems, for example, an anti-fog agent containing a nonionic surfactant (A) having an HLB value of 10 to 18 and dextrin and / or a derivative thereof (B), and an anti-fog resin sheet having a coating film of this anti-fog agent on a thermoplastic resin sheet have been proposed (see, for example, Patent Document 1). In addition, an anti-fogging agent for agricultural plastic films has been proposed, which is a sucrose fatty acid ester consisting of 60% or more behenic acid and which has 60% or more sucrose fatty acid ester as its main component (see, for example, Patent Document 2). Also, a surface treatment method has been proposed for a styrene-based resin sheet, in which sucrose laurate containing 70% or more of monoester is combined with coconut oil diethanolamide (see, for example, Patent Document 3). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2003-119451 A [Patent Document 2] Japanese Patent Application Publication No. 10-130511 [Patent Document 3] Japanese Patent Application Publication No. 59-51922 Summary of the Invention [Problem to be solved by the invention]

[0005] When an anti-fog resin sheet is whitened, the transparency decreases, resulting in an anti-fog resin sheet with poor appearance. Therefore, there is a demand for an anti-fog resin sheet which exhibits good anti-fog properties, is free from whitening of the sheet, has excellent transparency, and has a good appearance. The present inventors have studied the anti-fog resin sheet described in the above Patent Document 1, and have found that in some anti-fog resin sheets formed using sucrose fatty acid esters having an HLB value specified in Patent Document 1, whitening of the sheet occurs, resulting in an anti-fog resin sheet with poor transparency. In other words, from the viewpoint of obtaining an anti-fog resin sheet that exhibits good anti-fog properties, does not whiten in appearance, and has excellent transparency, which is the object of the present invention, the anti-fog resin sheet described in Patent Document 1 is not satisfactory and there is room for further study. Furthermore, the sucrose fatty acid ester of behenic acid described in Patent Document 2 above has poor water solubility and is therefore unsuitable as a water-based paint-type anti-fogging agent. Furthermore, the method of Patent Document 3 is limited to sucrose fatty acid esters mainly composed of lauric acid esters, and it is unclear as to the surface treatment of sucrose fatty acid esters of other fatty acids, for example, sucrose stearate or sucrose palmitate.

[0006] The present invention aims to provide an anti-fogging resin sheet using sucrose stearate or sucrose palmitate, which exhibits good anti-fogging properties, does not whiten in appearance, and has excellent transparency. [Means for solving the problem]

[0007] As a result of extensive research to solve the above problems, the inventors discovered that by specifying the amount of monoester of sucrose stearate or sucrose palmitate contained in an anti-fogging agent within a specific range, an anti-fogging resin sheet can be obtained that exhibits good anti-fogging properties while being resistant to whitening in appearance, and thus completed the present invention.

[0008] That is, the present invention includes the following aspects. [1] At least one surface of a thermoplastic resin sheet, An anti-fogging resin sheet having an anti-fogging layer formed thereon, the anti-fogging agent containing at least one selected from the group consisting of sucrose stearate ester containing 80% or more of monoester and sucrose palmitate ester containing 80% or more of monoester. [2] The anti-fogging resin sheet according to [1], wherein the anti-fogging agent further contains polyvinyl alcohol. [3] The anti-fog resin sheet according to [2], wherein the polyvinyl alcohol (B) has a saponification degree of 65 to 90 mol %. [4] The anti-fogging resin sheet according to [1], wherein the anti-fogging agent does not contain sucrose laurate. [5] The anti-fog resin sheet according to [1], wherein a release layer made of silicone oil (E) is formed on the other side of the thermoplastic resin sheet opposite to the side on which the anti-fog layer is provided. [6] The anti-fog resin sheet according to [1], wherein the thermoplastic resin sheet is a styrene-based resin sheet. [7] A secondary molded product obtained by molding the anti-fog resin sheet according to any one of [1] to [6]. Effect of the Invention

[0009] According to the present invention, it is possible to provide an anti-fogging resin sheet using sucrose stearate or sucrose palmitate, which exhibits good anti-fogging properties and is resistant to whitening in appearance. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] The present invention will be described in detail below. Note that the following description of the constituent elements is merely an example for explaining the present invention, and the present invention is not limited to these contents.

[0011] (Anti-fogging resin sheet) The anti-fog resin sheet of the present invention has a thermoplastic resin sheet and an anti-fog layer. The anti-fogging layer is formed on at least one surface of the thermoplastic resin sheet. The anti-fogging layer is formed using an anti-fogging agent. The anti-fogging resin sheet of the present invention may further have a release layer. The release layer is preferably formed on the other surface of the thermoplastic resin sheet opposite to the surface on which the anti-fogging layer is provided.

[0012] <Thermoplastic resin sheet> The type of resin for the thermoplastic resin sheet serving as the substrate of the anti-fog resin sheet of the present invention is not particularly limited, but is preferably transparent, and examples thereof include styrene-based resins such as polystyrene, crystalline polystyrene, styrene-butadiene copolymer, styrene-isoprene-styrene copolymer, styrene-isoprene-butadiene-styrene copolymer, styrene-ethylene-butadiene-styrene copolymer, transparent styrene-butadiene-(meth)acrylic acid alkyl ester copolymer, styrene-(meth)acrylic acid copolymer, styrene-maleic anhydride copolymer, and styrene-(meth)acrylic acid alkyl ester copolymer; propylene-based resins such as polypropylene, propylene-butadiene copolymer, and ethylene-propylene copolymer; polycarbonate, polyvinyl chloride, polyvinylidene chloride, polyamide resins such as nylon 6, and polyester resins such as polyethylene terephthalate are preferred.

[0013] In addition, two or more of these resins may be mixed and used as long as the transparency of the anti-fog resin sheet of the present invention is not impaired. Furthermore, these thermoplastic resin sheets may be multi-layered sheets of two or more layers using one or more of these resins. Furthermore, these thermoplastic resin sheets may be subjected to uniaxial or biaxial stretching treatment.

[0014] Furthermore, biaxially oriented polystyrene resin sheets are often heated and molded using a hot plate compressed air molding machine, and in this case, when a conventional antifogging agent is used, the antifogging property of the molded body during heating and molding tends to decrease significantly. However, in the antifogging resin sheet of the present invention, even when a biaxially oriented polystyrene resin sheet is used as the substrate, a secondary molded product having excellent antifogging property can be obtained. From the viewpoint of compatibility with a general-purpose hot plate compressed air molding machine, a polystyrene resin sheet is preferred as the substrate for the antifogging resin sheet of the present invention, and a biaxially oriented polystyrene resin sheet is most preferred.

[0015] The thickness of these thermoplastic resin sheets is not particularly limited, but is preferably 0.05 to 1.0 mm from the viewpoint of the rigidity and strength of the secondary molded product when the anti-fogging resin sheet is secondary molded.

[0016] In the resins used for these thermoplastic resin sheets, various types of fine particles for producing protrusions on the surface of the resin sheet can be added to prevent blocking of the anti-fog resin sheet, within a range that does not impair the transparency of the resin sheet. Examples of the fine particles include resin crosslinked beads such as styrene-based resin crosslinked beads, (meth)acrylic acid ester-based resin crosslinked beads, and polyurethane-based resin crosslinked beads, inorganic fine particles such as silica, hydrophobized silica, spherical silica, soft calcium carbonate, titanium oxide, and talc, and rubber fine particles. For rubber fine particles, a method of using a rubber-containing resin in combination is exemplified. The rubber-containing resin used here is different from the thermoplastic resin that is the base material of the anti-fogging resin sheet, and examples of the rubber-containing resin include high impact polystyrene (HIPS), styrene-acrylonitrile-butadiene copolymer (ABS), styrene-ethylene-butadiene-styrene copolymer (SEBS), styrene-butadiene-(meth)acrylic acid ester copolymer (MBS), and high impact (meth)acrylic acid ester (HI-PMMA).

[0017] <Anti-fogging layer> The anti-fogging layer is formed using an anti-fogging agent. The anti-fogging agent contains at least one type (A) selected from sucrose stearate ester having 80% or more monoester and sucrose palmitate ester having 80% or more monoester (hereinafter also referred to as the specific sucrose fatty acid ester represented by (A)). The antifogging agent may further contain polyvinyl alcohol. The antifogging agent preferably contains water (C). The antifogging agent may contain other additives such as surfactants having antistatic effects and lubricants in addition to the specific sucrose fatty acid ester represented by (A) above, polyvinyl alcohol, and water.

[0018] <<Sucrose stearate ester with 80% or more monoester and / or sucrose palmitate ester with 80% or more monoester>> Sucrose stearate and sucrose palmitate are known as nonionic surfactants, and commercially available products can be used in the present invention. As shown in the following examples, the monoester content of sucrose stearate and sucrose palmitate must be 80% or more. By incorporating sucrose stearate or sucrose palmitate with a monoester content of 80% or more, an anti-fogging resin sheet that satisfies both good anti-fogging properties and prevention of whitening of the appearance can be obtained.

[0019] <<Polyvinyl alcohol (B)>> The antifogging agent may further contain polyvinyl alcohol. When the anti-fogging agent contains polyvinyl alcohol, the anti-fogging performance can be improved while ensuring prevention of whitening of the sheet, compared to a system that does not contain polyvinyl alcohol. The polyvinyl alcohol (also called PVA) (B) is a homopolymer consisting of vinyl alcohol units or a copolymer consisting of vinyl alcohol units and vinyl acetate units, and the content of vinyl alcohol units is 50% by mass or more. The polyvinyl alcohol (B) is preferably a partial saponification reaction product of polyvinyl acetate, preferably having a saponification degree of 65 to 90 mol%, more preferably having a saponification degree of 70 to 90 mol%, and even more preferably having a saponification degree of 80 to 90 mol%. The preferred saponification degree is determined from the viewpoint of obtaining a significant antifogging improvement effect and not deteriorating the appearance of the antifogging resin sheet, and for example, by making the saponification degree 65 mol% or more, the water solubility is improved, and when the antifogging agent coating is formed by coating an aqueous solution, the dispersion uniformity of polyvinyl alcohol in the coating can be improved. Also, by making the saponification degree 90 mol% or less, the antifogging property becomes good. The viscosity of a 4% by mass aqueous solution of polyvinyl alcohol (B) at 20° C. is preferably 2 to 30 mPa·s, more preferably 2 to 25 mPa·s, even more preferably 4 to 15 mPa·s, even more preferably 4 to 9 mPa·s, particularly preferably 4 to 8 mPa·s, and particularly more preferably 4.5 to 6.0 mPa·s. From the viewpoints of obtaining an anti-fogging property improving effect and ease of mixing with an oleate, the viscosity of polyvinyl alcohol is preferably 2 mPa·s or more and 30 mPa·s or less, as described above.

[0020] <<Other sucrose fatty acid esters>> The antifogging agent of the present invention may or may not contain other sucrose fatty acid esters as long as it contains sucrose stearate and / or sucrose palmitate with a monoester content of 80% or more. For example, it may be an embodiment that does not contain sucrose laurate. An antifogging agent that does not contain or substantially does not contain sucrose laurate refers to an antifogging agent that has a sucrose laurate content of less than 10 ppm, which is the lower limit of general measurement, when the content of sucrose laurate is measured using a measurement method such as high performance liquid chromatography.

[0021] <<Water(C)>> The antifogging agent preferably contains water (C). Water (C) is a medium whose main component is water, such as ion-exchanged water, distilled water, or industrial water. The amount of water (C) is preferably 5 parts by mass or more per part by mass of the sucrose stearate and / or sucrose palmitate (A). For example, the amount of water in 100 parts by mass of water containing the sucrose stearate and / or sucrose palmitate (A) is preferably 83 parts by mass or more, more preferably 85 parts by mass or more. In addition, from the viewpoint of reducing the viscosity of the antifogging agent composition and improving coating workability, the amount of water (C) is preferably 5 parts by mass or more per part by mass of the sucrose stearate and / or sucrose palmitate (A), and from the viewpoint of maintaining an appropriate viscosity of the antifogging agent composition and improving coating workability, the amount of water (C) is preferably 1,000 parts by mass or less.

[0022] The content ratio of the sucrose stearate and / or sucrose palmitate (A) according to the present invention is preferably 0.1 to 15 parts by mass, and more preferably 0.1 to 5 parts by mass, per 100 parts by mass of the aqueous solution containing the anti-fogging agent of the present invention. When the antifogging agent of the present invention contains polyvinyl alcohol (B), the content of polyvinyl alcohol (B) is preferably 0.1 to 15 parts by mass, and more preferably 0.1 to 5 parts by mass, per 100 parts by mass of the aqueous solution containing the antifogging agent of the present invention.

[0023] Furthermore, the content ratio of sucrose stearate and / or sucrose palmitate (A) to polyvinyl alcohol (B) in the anti-fogging agent of the present invention is preferably sucrose stearate and / or sucrose palmitate (A) (parts by mass):polyvinyl alcohol (B) (parts by mass) = 85:15 to 10:90, more preferably 80:20 to 10:90, even more preferably 80:20 to 15:85, even more preferably 75:25 to 15:85, and particularly preferably 70:30 to 15:85. In the present invention, when both sucrose stearate and sucrose palmitate are contained as component (A), the content of component (A) is the total amount of both of them added together.

[0024] <Release layer> In the present invention, a release layer can be formed by applying a release agent to the surface of the thermoplastic resin sheet opposite to the surface on which the anti-fogging layer is provided. As the release agent, silicone oil (E) can be used. From the viewpoints of safety and economy, this silicone oil (E) has a viscosity of 1,000,000 to 500,000 mm at 25°C. 2 Dimethylpolysiloxanes in the range of 1 / s are preferred.

[0025] In addition, when applying the silicone oil (E) to the surface of the thermoplastic resin sheet, it is preferable to use it in the form of a silicone emulsion. The average particle size of the silicone oil (E) in the silicone emulsion is preferably 1 μm or less. That is, if the average particle size exceeds 1 μm, it is difficult to apply the silicone oil uniformly, and the appearance of the anti-fog resin sheet is deteriorated.

[0026] In addition, the silicone oil (E) used in the present invention is preferably applied to the other side of the surface coated with the antifogging agent, since the appearance of the sheet or secondary molded product is improved. That is, when the silicone oil (E) is mixed and applied in the antifogging agent, there is a problem that the appearance of the sheet or secondary molded product is deteriorated, so the amount of silicone oil (E) needs to be 10.0 parts by mass or less for 100 parts by mass of the aqueous solution containing the antifogging agent of the present invention. Furthermore, it is preferable to make it 5.0 parts by mass or less, and it is particularly preferable that the antifogging agent does not contain silicone oil.

[0027] Furthermore, it is also possible to add a surfactant having an antistatic effect, a lubricant, etc. to the silicone emulsion liquid containing the silicone oil (E) used in the present invention.

[0028] <Method for manufacturing anti-fogging resin sheet> The method for producing the anti-fogging resin sheet of the present invention is, for example, to coat at least one surface of a thermoplastic resin sheet with a solution-like anti-fogging agent (anti-fogging composition) containing at least one selected from sucrose stearate and sucrose palmitate (A) and, if necessary, polyvinyl alcohol (B), and then drying the solvent to form an anti-fogging layer. The anti-fogging agent (anti-fogging composition) may be an anti-fogging agent (anti-fogging composition) that does not contain sucrose laurate.

[0029] The method for producing the anti-fog resin sheet of the present invention is not particularly limited, but it is preferable to apply an anti-fog agent consisting of an aqueous solution to at least one surface of a thermoplastic resin sheet obtained by forming a film from a thermoplastic resin by a known method. Specifically, there can be mentioned a method in which one surface of a thermoplastic resin sheet is subjected to a hydrophilization treatment, and then the anti-fog agent of the present invention is applied to this treated surface, and the solvent is dried to form an anti-fog layer.

[0030] The method for applying the anti-fog agent used in the manufacturing method of the anti-fog resin sheet of the present invention includes known methods such as a spray coater, roll coater, gravure roll coater, knife coater, air knife coater, rotor dampening coater, and applicator system, and is not particularly limited.

[0031] The coating amount of the antifogging agent in the antifogging resin sheet of the present invention is preferably adjusted to a predetermined amount in order to improve the antifogging effect and prevent poor appearance due to uneven coating. Specifically, the coating amount of the solid content after drying, that is, the mass of the antifogging layer per unit area of ​​the antifogging resin sheet, is 5 to 1,000 mg / m. 2 is preferably 5 to 150 mg / m 2 It is particularly preferred that:

[0032] Quantitative analysis of the amount of anti-fog agent applied can be performed by Fourier transform infrared spectrophotometer analysis (multiple internal reflection method) [FTIR analysis (ATR method)].

[0033] In addition, examples of the method for hydrophilizing the surface of the thermoplastic resin sheet include known methods such as acid treatment, flame treatment, and corona treatment. The surface of the thermoplastic resin sheet subjected to such hydrophilization treatment preferably has a wet tension of 38 mN / m or more, and more preferably has a wet tension of 45 to 60 mN / m in order to uniformly apply the antifogging agent and obtain a sufficient antifogging effect. Here, the wet tension is a value measured by the method described in JIS K6768-1999.

[0034] (Secondary molded product) By molding the anti-fogging resin sheet of the present invention by means of vacuum forming, compressed air vacuum forming, hot plate compressed air forming, or the like, it is possible to produce secondary molded products suitable for food containers such as lunch containers, side dish containers, sushi containers, and sashimi containers, particularly anti-fogging transparent lids for such food containers. EXAMPLES

[0035] The present invention will be described in more detail below with reference to examples, but the scope of the present invention is not limited to these examples.

[0036] Example 1 0.9% by mass of sucrose stearate (100% monoester, HLB 19) and 0.4% by mass of polyvinyl alcohol (saponification degree, viscosity of 4% aqueous solution at 20°C 4.7 mPa s) were mixed with 98.7% by mass of water and dissolved in a warm bath at 60°C to obtain anti-fogging agent (1). Anti-fogging agent (1) did not produce white precipitate even when left to stand at room temperature.

[0037] Next, one side of a 0.21 mm thick biaxially oriented polystyrene resin sheet (Sandic Sheet 510, manufactured by Sandic Co., Ltd.) that had not been subjected to any coating treatment on its surface was subjected to a corona treatment with a wetting tension of 50 mN / m, and an anti-fog agent was applied to the corona-treated surface in a solid content of 50 mg / m using a roll coater method. 2 The anti-fogging agent (1) was appropriately diluted with water so as to obtain an anti-fogging resin sheet (1) having an anti-fogging layer formed on a polystyrene resin sheet, and then dried with a dryer. The amount of anti-fog agent applied was determined by measuring the infrared absorption spectrum of the sheet surface by the multiple internal reflection method (ATR method) using a Fourier transform infrared spectrophotometer (FTIR), and performing quantitative analysis based on a calibration curve created from standard samples with known application amounts.

[0038] The obtained anti-fog resin sheet (1) was evaluated for sheet appearance and anti-fog properties according to the following methods.

[0039] (Evaluation of Appearance of Anti-Fog Resin Sheet) The sheet after application of the antifogging agent was visually observed to evaluate the presence or absence of whitening of the sheet. The lower the degree of whitening of the sheet, the better the appearance of the antifogging resin sheet. [Evaluation Criteria] ○: The sheet after application does not turn white and maintains transparency. △: The sheet after application is slightly whitened, but at a level that does not interfere with practical use. ×: The sheet after application was whitened and the transparency was significantly reduced.

[0040] (Evaluation of anti-fogging properties of secondary molded products) The anti-fogging resin sheet (1) was molded using a hot plate compressed air molding machine with a hot plate temperature of 125° C. and a mold shown below to obtain a secondary molded product (1). Mold: 94mm (length) x 94mm (width) x 30mm (depth), corners: 2R Next, in order to evaluate the anti-fogging properties assuming the case where the contents are observed from the outside when used in a high-temperature food container, the high-temperature anti-fogging properties of the secondary molded product were evaluated as follows. That is, a base material (obtained by secondary molding of a thermoplastic resin sheet) having the same shape as the secondary molded product was prepared, and a paper with a 15 mm square checkerboard pattern printed thereon was placed on it. Then, 100 mL of hot water at 90°C was poured into the base material, and the top of the base material was covered with the secondary molded product obtained in the above example. The upper part of the base material was then left at 23°C for 5 minutes, and the distortion of the checkerboard pattern visible through the secondary molded product and the degree of water droplets attached to the top surface and the inside of the four corners were visually observed. The less the secondary molded product is clouded, or the less the checkerboard pattern is visually distorted, the better the anti-fogging properties of the anti-fogging resin sheet. [Evaluation Criteria] ○: The secondary molded product is not cloudy, and the checkerboard pattern is visible without distortion over 85% or more of the area of ​​the secondary molded product. △: The secondary molded product is not cloudy, but the checkerboard pattern appears distorted over an area larger than 15% of the secondary molded product. ×: Small water droplets adhere to the top surface or four corners of the secondary molded product, making it cloudy.

[0041] The evaluation results of Example 1 are shown in Table 1-1. Hereinafter, Table 1-1 and Table 1-2 are collectively referred to as Table 1. The anti-fogging resin sheet (1) had good sheet appearance and anti-fogging properties.

[0042] Example 2 An antifogging agent was obtained in the same manner as in Example 1, except that in Example 1, polyvinyl alcohol was removed, and 1.3 mass% of sucrose stearate (100% monoester, HLB19) was mixed with 98.7 mass% of water and dissolved in a warm bath at 60 degrees to obtain an antifogging agent (2). The sheet appearance and antifogging properties of the antifogging agent were evaluated in the same manner as in Example 1. The evaluation results of Example 2 are shown in Table 1. The anti-fogging resin sheet (2) had an anti-fogging property somewhat inferior to that of Example 1, but was still within a practically usable range, and whitening of the sheet could be prevented as in Example 1, and the sheet had a good appearance.

[0043] Example 3 0.9% by mass of sucrose palmitate (monoester 80%, di-triester 20%, HLB 16) and 0.4% by mass of polyvinyl alcohol were mixed with 98.7% by mass of water and dissolved in a warm bath at 60 degrees to obtain anti-fogging agent (3). Anti-fogging agent (3) did not produce a white precipitate even when left to stand at room temperature. The antifogging agent (3) was evaluated in terms of sheet appearance and antifogging properties in the same manner as in Example 1. The evaluation results of Example 3 are shown in Table 1. The anti-fogging resin sheet (3) had good sheet appearance and anti-fogging properties.

[0044] Example 4 An anti-fogging agent was obtained in the same manner as in Example 3, except that polyvinyl alcohol was removed, and 1.3 mass% of sucrose palmitate (monoester 80%, di-triester 20%, HLB 16) was mixed with 98.7 mass% of water and dissolved in a warm bath at 60 degrees to obtain anti-fogging agent (4). The sheet appearance and anti-fogging property of the obtained anti-fogging agent were evaluated in the same manner as in Example 1. The evaluation results of Example 4 are shown in Table 1. The anti-fogging resin sheet (4) had slightly inferior anti-fogging properties to that of Example 3, but was still within the range of practical use, and whitening of the sheet could be prevented as in Example 3, and the sheet had a good appearance.

[0045] (Examples 5 to 8) In Example 1, except that the content of polyvinyl alcohol was changed as shown in Table 1-1, an anti-fogging agent was obtained in the same manner as in Example 1, and the sheet appearance and anti-fogging property of the anti-fogging agent were evaluated in the same manner as in Example 1. The evaluation results of Examples 5 to 8 are shown in Table 1.

[0046] Comparative Example 1 1.3% by mass of sucrose stearate (monoester 70%, di-triester 30%, HLB 15) was mixed with 98.7% by mass of water and dissolved in a warm bath at 60 degrees to obtain comparative anti-fogging agent (1). When comparative anti-fogging agent (1) was allowed to stand at room temperature, a white precipitate was formed. The comparative antifogging agent (1) was evaluated in terms of sheet appearance and antifogging properties in the same manner as in Example 1. The evaluation results of Comparative Example 1 are shown in Table 2. The comparative anti-fogging resin sheet (1) had somewhat inferior anti-fogging properties, but was still at a level that did not pose a problem in practical use. However, the sheet was whitened and had a poor appearance.

[0047] Comparative Example 2 1.3% by mass of sucrose stearate (monoester 75%, di-triester 25%, HLB 16) was mixed with 98.7% by mass of water and dissolved in a warm bath at 60 degrees to obtain comparative anti-fogging agent (2). When comparative anti-fogging agent (2) was allowed to stand at room temperature, a white precipitate was formed. The comparative antifogging agent (2) was evaluated in terms of sheet appearance and antifogging properties in the same manner as in Example 1. The evaluation results of Comparative Example 2 are shown in Table 2. The comparative anti-fogging resin sheet (2) had somewhat inferior anti-fogging properties, but was still at a level that did not pose a problem in practical use. However, the sheet was whitened and had a poor appearance.

[0048] Comparative Example 3 1.3% by mass of sucrose palmitate (monoester 70%, di-triester 30%, HLB 15) was mixed with 98.7% by mass of water and dissolved in a 60°C warm bath to obtain comparative anti-fogging agent (3). When comparative anti-fogging agent (3) was allowed to stand at room temperature, a white precipitate was formed. The comparative antifogging agent (3) was evaluated in terms of sheet appearance and antifogging properties in the same manner as in Example 1. The evaluation results of Comparative Example 3 are shown in Table 2. The comparative anti-fogging resin sheet (3) had somewhat inferior anti-fogging properties, but was still at a level that did not pose a problem in practical use. However, the sheet was whitened and had a poor appearance.

[0049] [Table 1-1]

[0050] [Table 1-2]

[0051] [Table 2]

[0052] The anti-fogging resin sheets of the Examples had a practically usable level of anti-fogging property, did not whiten, and had good sheet appearance. In particular, when an anti-fogging agent containing polyvinyl alcohol was used, the anti-fogging resin sheets had good anti-fogging property and sheet appearance. The anti-fog resin sheet of the comparative example was whitened and had a poor appearance.

[0053] As shown in Tables 1 and 2 above, even if sucrose fatty acid esters with similar HLB values ​​are used, the performance of the anti-fog resin sheet differs depending on the number of carbon atoms and the amount of di- or triester. When sucrose stearate and sucrose palmitate are used, the monoester content must be 80%, and by using sucrose stearate and sucrose palmitate containing 80% or more of monoester, the anti-fogging agent containing them does not produce white precipitate, so that whitening of the anti-fogging resin sheet can be prevented and a sheet with good appearance can be obtained. In addition, these anti-fogging resin sheets also have good anti-fogging properties. In particular, in an anti-fogging agent containing sucrose stearate and sucrose palmitate with monoesters of 80% or more, by adding polyvinyl alcohol, a resin sheet with even better anti-fogging properties can be obtained. Among these, a resin sheet in which the ratio of sucrose stearate and / or sucrose palmitate (A) (parts by mass):polyvinyl alcohol (B) (parts by mass) is 80:20 to 10:90 can be made to have even better anti-fogging properties. As is apparent from the examples, the anti-fog resin sheet of the present invention satisfies good sheet appearance and good anti-fog properties.

Claims

1. At least one surface of the thermoplastic resin sheet is An anti-fogging resin sheet having an anti-fogging layer formed thereon, the anti-fogging agent containing at least one selected from the group consisting of sucrose stearate ester containing 80% or more of monoester and sucrose palmitate ester containing 80% or more of monoester.

2. The anti-fogging resin sheet according to claim 1 , wherein the anti-fogging agent further contains polyvinyl alcohol.

3. The anti-fogging resin sheet according to claim 2, wherein the polyvinyl alcohol (B) has a saponification degree of 65 to 90 mol %.

4. The anti-fogging resin sheet according to claim 1 , wherein the anti-fogging agent does not contain sucrose laurate.

5. 2. The anti-fogging resin sheet according to claim 1, further comprising a release layer made of silicone oil (E) formed on the other surface of said thermoplastic resin sheet opposite to the surface on which the anti-fogging layer is formed.

6. The anti-fog resin sheet according to claim 1 , wherein the thermoplastic resin sheet is a styrene-based resin sheet.

7. A secondary molded product obtained by molding the anti-fogging resin sheet according to any one of claims 1 to 6.

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