JP2024173250A - Anti-fogging resin sheet and its secondary molded product - Google Patents

Abstract

To provide an antifogging resin sheet that is excellent in adhesion between an antifogging layer and a thermoplastic resin sheet while exhibiting a good antifogging property, and in which the antifogging layer is hardly peeled from the thermoplastic resin sheet.SOLUTION: There is provided an antifogging resin sheet in which an antifogging layer formed of an antifogging agent that contains at least one kind (A) selected from sodium oleate and potassium oleate and at least one kind (B) selected from polyvinyl alcohol and polyvinyl pyrrolidone, and does not contain sucrose fatty acid ester is formed on at least one surface of a thermoplastic resin sheet.SELECTED DRAWING: None

Description

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

Resin sheets extruded using various thermoplastic resins are then heated and molded using a vacuum forming machine, compressed air vacuum forming machine, hot plate compressed air forming machine, etc., and the resulting secondary molded products 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, containers for side dishes, etc., due to their transparency. However, these lid materials have the problem that the inside of the lid material becomes cloudy due to water vapor generated from the contents.

As a means for solving the above problems, for example, an anti-fogging styrene-based resin sheet has been proposed in which an anti-fogging agent consisting of sucrose fatty acid ester, polyvinyl alcohol, and fatty acid salt is applied to a styrene-based resin sheet (see, for example, Patent Document 1).

JP 2008-222868 A

The present inventors have evaluated anti-fog resin sheets formed by applying an anti-fog agent to a thermoplastic resin sheet, such as a styrene-based resin sheet as described in the above Patent Document 1. As a result, as shown in the comparative example below, it was found that an anti-fog resin sheet in which an anti-fog layer made of an anti-fog agent containing a sucrose fatty acid ester, polyvinyl alcohol, and a fatty acid salt having 12 to 17 carbon atoms is formed on a thermoplastic resin sheet has poor adhesion between the anti-fog layer and the thermoplastic resin sheet, and the anti-fog layer is easily peeled off from the thermoplastic resin sheet.

Therefore, the present invention aims to provide an anti-fog resin sheet that exhibits good anti-fog properties, has excellent adhesion between the anti-fog layer and the thermoplastic resin sheet, and is unlikely to peel off from the thermoplastic resin sheet.

As a result of intensive research conducted by the present inventors to solve the above problems, it was discovered that when an anti-fogging resin sheet is formed using an anti-fogging agent that contains at least one (A) selected from sodium oleate and potassium oleate, and at least one (B) selected from polyvinyl alcohol and polyvinylpyrrolidone, but does not contain a sucrose fatty acid ester, an anti-fogging resin sheet can be obtained that exhibits good anti-fogging properties, has excellent adhesion between the anti-fogging layer and the thermoplastic resin sheet, and is unlikely to peel off from the thermoplastic resin sheet, thereby completing the present invention.

That is, the present invention includes the following aspects.
[1] At least one surface of a thermoplastic resin sheet,
The anti-fogging resin sheet has an anti-fogging layer formed thereon, the anti-fogging agent comprising at least one (A) selected from sodium oleate and potassium oleate, and at least one (B) selected from polyvinyl alcohol and polyvinylpyrrolidone, but not containing a sucrose fatty acid ester.
[2] The anti-fog resin sheet according to [1], wherein the polyvinyl alcohol (B) has a saponification degree of 65 to 90 mol %.
[3] The anti-fog resin sheet according to [1], wherein a release layer made of silicone oil (E) is formed on the other surface of the thermoplastic resin sheet opposite to the surface on which the anti-fog layer is provided.
[4] The anti-fog resin sheet according to [1], wherein the thermoplastic resin sheet is a styrene-based resin sheet.
[5] A secondary molded product obtained by molding the anti-fog resin sheet according to any one of [1] to [4].

The present invention makes it possible to provide an anti-fog resin sheet that exhibits good anti-fog properties, has excellent adhesion between the anti-fog layer and the thermoplastic resin sheet, and is unlikely to peel off from the thermoplastic resin sheet.

The present invention will be described in detail below. Note that the explanation of the components described below is merely an example for explaining the present invention, and the present invention is not limited to these contents.

(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.

<Thermoplastic resin sheet>
The resin type of the thermoplastic resin sheet serving as the substrate of the anti-fogging resin sheet of the present invention is not particularly limited, but is preferably transparent. For example, 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.

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.

Furthermore, biaxially oriented polystyrene resin sheets are often heat-molded using a hot plate compressed air molding machine. In this case, when a conventional anti-fog agent is used, the anti-fog properties of the molded product tend to decrease significantly during heat molding. However, with the anti-fog resin sheet of the present invention, a secondary molded product having excellent anti-fog properties can be obtained even when a biaxially oriented polystyrene resin sheet is used as the substrate. From the viewpoint of compatibility with general-purpose hot plate compressed air molding machines, a polystyrene resin sheet is preferred as the substrate for the anti-fog resin sheet of the present invention, and a biaxially oriented polystyrene resin sheet is most preferred.

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-fog resin sheet is secondary molded.

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. As the rubber fine particles, a method of using a rubber-containing resin in combination is exemplified, and 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).

<Anti-fogging layer>
The anti-fogging layer is formed using an anti-fogging agent.
The antifogging agent contains at least one (A) selected from sodium oleate and potassium oleate, and at least one (B) selected from polyvinyl alcohol and polyvinylpyrrolidone, but does not contain a sucrose fatty acid ester.

<<Sodium oleate (A) and/or potassium oleate (A)>>
Sodium oleate and potassium oleate (A) are known as anionic surfactants, and in the present invention, commercially available products can be used.

<<Polyvinyl alcohol (B) and/or polyvinylpyrrolidone (B)>>
<<<Polyvinyl alcohol (B)>>>
The polyvinyl alcohol (also referred to as 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.
As the polyvinyl alcohol (B), a partial saponification reaction product of polyvinyl acetate is preferred, and one having a saponification degree of 65 to 90 mol % is preferred, one having a saponification degree of 70 to 90 mol % is more preferred, and one having a saponification degree of 80 to 90 mol % is even more preferred.
The preferred saponification degree is determined from the viewpoint of obtaining a significant antifogging effect without 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 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.

<<<Polyvinylpyrrolidone (B)>>>
The weight average molecular weight (Mw) of polyvinylpyrrolidone (B) is not particularly limited, but is preferably within the range of 8,000 to 3,000,000, more preferably within the range of 20,000 to 2,000,000, even more preferably within the range of 40,000 to 2,000,000, even more preferably within the range of 500,000 to 2,000,000, and particularly preferably within the range of 500,000 to 1,500,000. Within the range of 8,000 to 3,000,000, the smaller the weight average molecular weight of polyvinylpyrrolidone is, the easier it is to mix with an oleate salt, and the larger the weight average molecular weight is, the higher the heat resistance can be obtained.

Commercially available polyvinylpyrrolidone may be used, and the commercially available polyvinylpyrrolidone may be in powder form or in solution form. In addition, for example, two or more types of polyvinylpyrrolidone having different weight average molecular weights may be used in combination.

Polyvinylpyrrolidone is typically a polymer composed of vinylpyrrolidone alone, but may be a copolymer of vinylpyrrolidone and other monomers as long as the effects of the present invention are not impaired. Examples of other monomers include acrylic acid esters, acrylic acid, methacrylic acid esters, methacrylic acid, styrene, and vinyl acetate. Polyvinylpyrrolidone may also be a block polymer of a vinylpyrrolidone block and a polyvinyl alcohol block of another monomer, or a graft polymer.

<<Non-containing sucrose fatty acid ester>>
As shown in the comparative examples below, in an anti-fog resin sheet in which an anti-fog layer made of an anti-fog agent containing a sucrose fatty acid ester, polyvinyl alcohol, and a fatty acid salt having 12 to 17 carbon atoms is formed on a thermoplastic resin sheet, the adhesion between the anti-fog layer and the thermoplastic resin sheet is poor, and the anti-fog layer is prone to peeling off from the thermoplastic resin sheet.
Therefore, the antifogging agent of the present invention does not contain or substantially does not contain sucrose fatty acid esters. The term "substantially does not contain" specifically means that the content of sucrose fatty acid esters is less than 10 ppm, which is the lower limit of general measurement, for example, when the content of sucrose fatty acid esters is measured using a (high performance liquid chromatography) measurement method.
Here, the sucrose fatty acid ester includes those obtained by transesterification of sucrose with a lower alcohol ester of a fatty acid, such as a fatty acid methyl ester. Specific examples include sucrose stearate, sucrose palmitate, sucrose laurate, and sucrose oleate.

The anti-fogging agent of the present invention contains at least one (A) selected from sodium oleate and potassium oleate, and at least one (B) selected from polyvinyl alcohol and polyvinylpyrrolidone, and does not contain a sucrose fatty acid ester.
In a mixed system of sucrose fatty acid ester and sodium oleate, or a mixed system of sucrose fatty acid ester and potassium oleate, the adhesion between the anti-fogging layer applied to the thermoplastic resin sheet and the thermoplastic resin sheet is poor. For example, when the thermoplastic resin sheet is rolled up, the anti-fogging agent is transferred to the opposite side, causing problems such as reduced transparency and deterioration of anti-fogging properties due to surface roughness of the coating film. However, the present invention can effectively prevent such problems.
In the present invention, the composition used as the antifogging agent contains at least one selected from sodium oleate and potassium oleate, which are highly water-soluble, and therefore the handling property during coating is good and the coating layer can be formed in good condition. It is believed that the formation of the coating layer in good condition also contributes to the maintenance and improvement of the antifogging property of the antifogging resin sheet.

The content ratio of sodium oleate and/or potassium oleate (A) according to the present invention is preferably 0.01 parts by mass to 20 parts by mass, and more preferably 0.05 parts by mass to 10 parts by mass, relative to 100 parts by mass of the aqueous solution containing the antifogging agent of the present invention.
The content ratio of the polyvinyl alcohol and/or polyvinylpyrrolidone (B) according to the present invention is preferably 0.05 parts by mass to 20 parts by mass, and more preferably 0.05 parts by mass to 10 parts by mass, based on 100 parts by mass of the aqueous solution containing the antifogging agent of the present invention.

Furthermore, the content ratio of sodium oleate and/or potassium oleate (A) and polyvinyl alcohol and/or polyvinylpyrrolidone (B) in the antifogging agent according to the present invention is preferably sodium oleate and/or potassium oleate (A):polyvinyl alcohol and/or polyvinylpyrrolidone (B)=5 parts by mass to 95 parts by mass:95 parts by mass to 5 parts by mass, more preferably 15 parts by mass to 85 parts by mass:85 parts by mass to 15 parts by mass, and even more preferably 15 parts by mass to 72 parts by mass:85 parts by mass to 28 parts by mass.
In particular, in the present invention, it is more preferable from the viewpoint of improving anti-fogging properties that the composition used as the anti-fogging agent contains a relatively high proportion of a highly water-soluble oleate, and from the viewpoint of the appearance of the sheet after application, it is preferable that the composition contains a relatively low proportion of the oleate. For example, it is preferable that the ratio of sodium oleate and/or potassium oleate (A):polyvinyl alcohol and/or polyvinylpyrrolidone (B) is 15 parts by mass:85 parts by mass to 68 parts by mass:32 parts by mass.
In the present invention, when both sodium oleate and potassium oleate are contained as component (A), the content of the component (A) is the total amount of both of them added together, and when both polyvinyl alcohol and polyvinylpyrrolidone are contained as component (B), the content of the component (B) is the total amount of both of them added together.

<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) is preferably dimethylpolysiloxane having a viscosity at 25° C. in the range of 100 to 500,000 mm ² /s.

When applying the silicone oil (E) to the surface of the thermoplastic resin sheet, it is advisable 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. In other words, if the average particle size exceeds 1 μm, it will be difficult to apply the silicone oil evenly, and the appearance of the anti-fog resin sheet will deteriorate.

The silicone oil (E) used in the present invention is preferably applied to the surface other than the surface coated with the anti-fog agent, since this improves the appearance of the sheet or secondary molded product. In other words, if silicone oil (E) is mixed into the anti-fog agent and then applied, there is a problem that the appearance of the sheet or secondary molded product deteriorates, so the amount of silicone oil (E) to be blended per 100 parts by mass of the aqueous solution containing the anti-fog agent of the present invention must be 10.0 parts by mass or less. It is further preferable to make it 5.0 parts by mass or less, and it is particularly preferable that the anti-fog agent does not contain silicone oil.

In addition, surfactants or lubricants that have antistatic properties can be added to the silicone emulsion liquid containing the silicone oil (E) used in the present invention.

<Method for producing anti-fogging resin sheet>
The method for producing the anti-fogging resin sheet of the present invention involves, for example, applying to at least one surface of a thermoplastic resin sheet a solution-like anti-fogging agent (anti-fogging composition) that contains at least one type (A) selected from sodium oleate and potassium oleate, and at least one type (B) selected from polyvinyl alcohol and polyvinylpyrrolidone, but does not contain a sucrose fatty acid ester, and then drying the solvent to form an anti-fogging layer.

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, one surface of the thermoplastic resin sheet is subjected to a hydrophilic treatment, and then the anti-fog agent according to the present invention is applied to this treated surface, and the solvent is dried to form an anti-fog layer.

Methods for applying the anti-fog agent used in the manufacturing method of the anti-fog resin sheet of the present invention include known methods such as spray coater, roll coater, gravure roll coater, knife coater, air knife coater, rotor dampening coater, and applicator method, and are not particularly limited.

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 solid content after drying, i.e., the mass of the antifogging layer per unit area of the antifogging resin sheet, is preferably 5 to 1,000 mg/ ^m2 , and particularly preferably 5 to 150 mg/ ^m2 .

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

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

(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.

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

Example 1
1.3 mass % of sodium oleate and 0.6 mass % of polyvinyl alcohol (saponification degree 74 mol %, viscosity of 4% aqueous solution at 20° C. 4.7 mPa·s) were mixed and dissolved in 98.1 mass % of water to obtain an antifogging agent (1).

Next, one side of a biaxially oriented polystyrene resin sheet having a thickness of 0.21 mm ("Sandic Sheet 510" manufactured by Sandic Co., Ltd.) that had not been subjected to a coating treatment on its surface was subjected to a corona treatment with a wet tension of 50 mN/m, and an anti-fog agent (1) appropriately diluted with water was applied to the corona-treated surface using a roll coater so that the solid content coating amount of the anti-fog agent was 50 mg/ ^m2 , followed by drying with a dryer to obtain an anti-fog resin sheet (1) in which an anti-fog layer was formed on the polystyrene resin sheet.
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 prepared from standard samples with known application amounts.

The obtained anti-fog resin sheet (1) was evaluated for sheet appearance, anti-fog properties, anti-fog properties of deep-drawn molded products, and adhesion to the sheet according to the following methods.

(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 is not whitened 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 is whitened and transparency is significantly reduced.

(Evaluation of Anti-Fog 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, after which 100 mL of hot water at 90°C was poured into the base material, the top of which was covered with the secondary molded product obtained in the above example, and the material was left at 23°C for 5 minutes, and the distortion of the checkerboard pattern visible through the secondary molded product, as well as 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, and the checkerboard pattern is visible without distortion over 50% or more of the area of the secondary molded product. △: The secondary molded product is not cloudy, but the checkerboard pattern is distorted over an area larger than 15% of the secondary molded product. ×: Small water droplets adhere to the top surface or the four corners of the secondary molded product, causing cloudiness.

(Evaluation of anti-fogging properties of deep-drawn molded products)
As a deep-drawn molded product (secondary molded product), the anti-fogging resin sheet (1) was molded using a hot plate compressed air molding machine with a hot plate temperature of 125°C to obtain a molded product of the size shown below, thereby obtaining a deep-drawn secondary molded product (1).
Mold: 94mm (length) x 94mm (width) x 50mm (depth), corners: 2R
The method for evaluating the anti-fogging property is as described above in (Evaluation of anti-fogging property of secondary molded product).

(Evaluation of adhesion between anti-fogging agent and sheet)
The adhesion between the anti-fogging layer made of the anti-fogging agent and the thermoplastic resin sheet (also referred to as the adhesion of the anti-fogging agent to the sheet) was evaluated.
The surface of the anti-fogging resin sheet (1) was rubbed with a finger, and the presence or absence of peeling of the anti-fogging agent and the presence or absence of clouding of the sheet were evaluated.
[Evaluation Criteria]
◯: The anti-fog agent did not peel off, and the sheet did not become cloudy. △: The anti-fog agent peeled off slightly, but at a level that did not interfere with practical use. ×: The anti-fog agent peeled off from the sheet, and the sheet became cloudy.

The evaluation results of Example 1 are shown in Table 1-1.
The anti-fogging resin sheet (1) was excellent in all respects of sheet appearance, anti-fogging properties, anti-fogging properties of the deep-drawn molded product, and adhesion.
In Table 1-1, since the content of sodium oleate is 1.3% by mass and polyvinyl alcohol is 0.6% by mass, sodium oleate is expressed as 1.3/(1.3+0.6)=68 (mass%) and polyvinyl alcohol is expressed as 0.6/(1.3+0.6)=32 (mass%) (the same notation is used for other examples and comparative examples).

(Example 2) to (Example 12)
Antifogging agents (2) to (12) were obtained in the same manner as in Example 1, except that the components contained in the antifogging agent were changed to the types and content ratios shown in Table 1-1 or Table 1-2. Hereinafter, Table 1-1 and Table 1-2 will be collectively referred to as "Table 1".
Next, using the obtained antifogging agents (2) to (12), antifogging resin sheets (2) to (12) and secondary molded articles (2) to (12) were obtained in the same manner as in Example 1, and evaluated in the same manner as in Example 1. The evaluation results are shown in Table 1.
In Example 6, polyvinylpyrrolidone (K value 90, number average molecular weight 360,000, weight average molecular weight 1,200,000) was used.
In Example 9, polyvinyl alcohol (saponification degree 87.5 mol %, viscosity of a 4% aqueous solution at 20° C. 23 mPa·s) was used.
In Examples 10 to 12, potassium oleate was used.

(Comparative Example 1)
A comparative antifogging agent (1) was obtained by mixing and dissolving 1.3 mass% of sucrose laurate (monoester 70%, HLB 15), 0.6 mass% of polyvinyl alcohol (saponification degree 74 mol%, viscosity of 4% aqueous solution at 20°C 4.7 mPa·s) and 1.0 mass% of sodium oleate in 97.1 mass% of water.
Next, using the obtained comparative antifogging agent (1), a comparative antifogging resin sheet (1) and a comparative secondary molded product (1) were obtained in the same manner as in Example 1, and evaluated in the same manner as in Example 1. The evaluation results are shown in Table 2.
The comparative anti-fogging resin sheet (1) had good anti-fogging properties, but poor adhesion to the sheet.
In Table 2, since the composition contains 1.3 mass% sucrose laurate, 0.6 mass% polyvinyl alcohol, and 1.0 mass% sodium oleate, the sucrose fatty acid ester (sucrose laurate) is expressed as 1.3/(1.3+0.6+1.0)=45, the polyvinyl alcohol is expressed as 0.6/(1.3+0.6+1.0)=21 (mass%), and the sodium oleate is expressed as 1.0/(1.3+0.6+1.0)=34 (mass%).

(Comparative Example 2) to (Comparative Example 6)
Comparative antifogging agents (2) to (6) were obtained in the same manner as in Comparative Example 1, except that the types and content ratios of the components contained in the antifogging agent were changed to those shown in Table 2.
Next, using the obtained comparative antifogging agents (2) to (6), comparative antifogging resin sheets (2) to (6) and comparative secondary molded articles (2) to (6) were obtained in the same manner as in Comparative Example 1, and evaluated in the same manner as in Example 1 and Comparative Example 1. The evaluation results are shown in Table 2.
Comparative Examples 2 and 3 are also given in which the sodium oleate in Comparative Example 1 was replaced with sodium laurate. Comparative Example 2 has an antifogging agent composition corresponding to Example 1 in Patent Document 1, and Comparative Example 3 has an antifogging agent composition corresponding to Example 3 in Patent Document 1.

The anti-fogging resin sheets of the Examples were all excellent in terms of sheet appearance, anti-fogging properties, anti-fogging properties of deep-drawn molded products, and adhesion.
The anti-fogging resin sheet of the comparative example had good anti-fogging properties, but poor adhesion to the sheet.

The results shown in Table 1 show that the anti-fog resin sheets obtained in the examples showed satisfactory results in all areas: good sheet appearance, good anti-fog properties, good anti-fog properties for deep-drawn molded products, and good adhesion.

Claims (5)

At least one surface of the thermoplastic resin sheet is
The anti-fogging resin sheet has an anti-fogging layer formed thereon, the anti-fogging agent comprising at least one (A) selected from sodium oleate and potassium oleate, and at least one (B) selected from polyvinyl alcohol and polyvinylpyrrolidone, but not containing a sucrose fatty acid ester. The anti-fog resin sheet according to claim 1, wherein the polyvinyl alcohol (B) has a degree of saponification of 65 to 90 mol%. The anti-fog resin sheet according to claim 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. The anti-fog resin sheet according to claim 1, wherein the thermoplastic resin sheet is a styrene-based resin sheet. A secondary molded product obtained by molding the anti-fogging resin sheet according to any one of claims 1 to 4.