JP2002060633A - Anti-fogging agent, resin sheet and molded article prepared from the sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an anti-fogging agent which can impart more excellent anti-fogging properties and appearance than eve to transparent thermoplastic resin sheets and molded articles, a resin sheet treated with the anti-fogging agent, and a molded article obtained by thermoforming the sheet. SOLUTION: There are provided an anti-fogging agent containing a sucrose fatty acid ester and a polymer, a resin sheet on at least one side of which the anti-fogging agent is coated, and a molded article obtained by thermoforming the sheet.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an antifogging agent, a resin sheet surface-treated with the antifogging agent, and a molded product obtained by thermoforming the resin sheet. More specifically, an anti-fogging agent capable of imparting superior anti-fogging properties and appearance to a transparent thermoplastic resin sheet or a molded product, and a resin sheet and a sheet treated with the anti-fogging agent are heated. It relates to a molded product obtained by molding.

[0002]

2. Description of the Related Art Containers using transparent resin sheets are widely used in the field of packaging materials and industrial materials because the inside can be seen. However, since the transparent resin sheet generally has high hydrophobicity, when water vapor condenses, water adheres in a granular state on the sheet surface, scatters light, and appears cloudy.
In particular, when a prepared dish or the like is placed in a thermoformed container and sealed, the food is liable to fog because of water vapor released from food. Such a fogging phenomenon makes the contents difficult to see, lowering the commercial value, which is not preferable.

Heretofore, in order to prevent such a fogging phenomenon, a method of applying a surfactant having a hydrophilic group to a sheet surface as an antifogging agent has been generally used. For example,
Sorbitan esters as antifogging agents (JP-A-53-115)
No. 781), sucrose fatty acid esters (Japanese Unexamined Patent Publication No.
No. 78272, Japanese Patent Publication No. 61-36864),
Glycerin fatty acid esters and polyglycerin fatty acid esters (JP-A-10-060420) have been generally used.

Further, two or more surfactants have been used in combination to improve the anti-fogging property (JP-A-53-78272, JP-B-61-368).
No. 64, JP-A-10-060420).

However, even if these methods are used, if the antifogging agent is applied to the sheet and the sheet is wound into a roll, the antifogging layer peels off and adheres to the opposite surface of the sheet. It becomes uniform and partial antifogging failure occurs. In addition, the mixture with the silicone applied to the opposite surface of the sheet for blocking prevention causes stain-like fogging, resulting in a problem of poor appearance.

Further, the conventionally used anti-fogging agents have satisfactory anti-fogging performance when applied to a sheet, but the anti-fogging performance can be suddenly lowered by thermoforming. Did not. For example, if the heating temperature of the sheet is too high during thermoforming, the anti-fog performance will drop sharply, or if a deep-drawn container is thermoformed, the anti-fog agent will not follow the elongation of the sheet. However, there was a problem that the film was peeled off from the sheet to cause a remarkable decrease in antifogging property.

[0007]

The present inventors have made intensive studies in order to solve such a conventional problem, and as a result, have reached the present invention. Another object of the present invention is to provide an anti-fogging agent capable of forming an anti-fogging layer excellent in heat resistance and stretchability without impairing the anti-fogging layer, and to provide a deep-drawn container having anti-fogging properties which has been impossible in the past.

[0008]

That is, the present invention provides an antifogging agent characterized by containing a sucrose fatty acid ester and a polymer, a resin sheet coated on at least one side of the sheet with the antifogging agent, and a resin sheet. A molded product obtained by thermoforming a resin sheet.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION A sucrose fatty acid ester, which is the first constituent element of the present invention, is a surfactant in which a fatty acid is ester-linked to at least one of eight hydroxyl groups of sucrose. It is used mainly for imparting anti-fog performance. Although there are other antifogging agents with high antifogging performance, sucrose fatty acid esters were evaluated as a result of evaluating the transparency at the time of application, the antifogging performance after thermoforming and heating, and the ability to follow the resin sheet at the time of heating and stretching. Confirmed the highest synergistic effect when used together.

[0010] Sucrose fatty acid esters include monoesters, diesters, triesters, and other esters, and any of them may be used, and a mixture thereof may be used. It is preferably at least 65%, more preferably at least 65%. When the proportion of the monoester is 50% or more, or when the proportion of the diester or triester is 50% or less, the HLB (Hydrophile Lipophile Balance) is large, and the anti-fog performance and the transparency when applied are improved. .

The fatty acid used in the esterification of sucrose preferably has 70% or more of the constituent fatty acids having 6 or more carbon atoms, more preferably 10 or more, and particularly preferably 12 lauric acids. This is because the larger the carbon number, the better the anti-fogging property. Further, 70% or more of the constituent fatty acids preferably have 18 or less carbon atoms, more preferably 14 or less, and particularly preferably 12 lauric acids. This is because when the number of carbon atoms is 18 or less, transparency when applied to a sheet is particularly excellent.

Accordingly, the number of carbon atoms can be appropriately selected from the viewpoints of both antifogging property and transparency, and in order to achieve both of them, the number of carbon atoms is preferably 6 to 18, more preferably 10 to 10.
14, particularly preferably 12 lauric acids.

It is also possible to improve antifogging performance by using sucrose esters composed of different fatty acids in combination.

The polymer which is the second component of the present invention improves the strength of the anti-fogging agent layer, improves the anti-fogging property of the sucrose fatty acid ester after heating at a high temperature, and improves the anti-fogging layer at the time of thermoforming. It is essential to improve stretchability.

As the polymer used in the present invention, those having a softening temperature adapted to the thermoforming temperature of each resin sheet are preferable. Here, the softening temperature means a temperature at which the modulus of elasticity is 10 MPa or less at which molding is possible by ordinary vacuum molding or pressure molding, and substantially matches the glass transition temperature of the amorphous polymer. When the softening temperature is 35 ° C. or higher, it is preferable in that the transfer phenomenon to the reverse surface of the sheet hardly occurs when the film is wound into a roll. Further, when the softening temperature is 180 ° C. or lower, it is preferred in that the sucrose fatty acid ester used in combination does not cause a reduction in antifogging property due to thermal decomposition or a coloring phenomenon. Therefore, 35 to 180
When the temperature is in the range of ° C., the phenomenon of transfer to the reverse side of the sheet, thermal decomposition, and the like can both be prevented, so that it is more preferable.

Examples of the polymer having a softening temperature of 35 to 180 ° C. include acrylic polymers represented by poly (alkyl) methacrylates having 1 to 4 carbon atoms, poly (alkyl) acrylates, or copolymers of both. . The above-mentioned polymer can be made into an aqueous solution having low viscosity, so that it can be easily adjusted with the anti-fogging agent solution. Further, the softening temperature and the elastic modulus at the time of heating can be adjusted by the copolymerization ratio. The softening temperature can be adjusted according to resins having different thermoforming temperatures, such as resin, polystyrene and polycarbonate.

Further, the polymer used in the present invention includes:
Other polymers that can be applied to form a strong solid layer and be thermoformed can also be used preferably. For example, a water-soluble polyester soluble in water, a high molecular weight polymer made into a solution using a solvent, or the like can be used.

The use of a surfactant having an antifogging property imparted to the polymer itself among the acrylic polymers described above further improves the performance of the antifogging agent. For example, a polymer type surfactant based on an acrylic polymer to which a quaternary ammonium ion is added has a particularly excellent effect.

In the present invention, a conventionally used antifogging agent can be used in combination. For example, sorbitan fatty acid ester, glycerin fatty acid ester, polyglycerin fatty acid ester, polyethylene glycol fatty acid ester,
Nonionic surfactants such as polyoxyethylene sorbitan fatty acid esters and polyethylene glycol fatty acid esters, cationic surfactants such as alkyl sulfates and alkyl ether sulfates, and anions such as metal salts of dodecyl sulfonic acid and metal salts of dodecyl benzene sulfonic acid A system surfactant or the like can also be used within a range that does not impair set-off or the sheet appearance. In some cases, a plurality of combinations may be performed.

The mixing ratio of the sucrose fatty acid ester to the polymer is preferably at least 0.1 part by weight of the polymer to 1 part by weight of the sucrose fatty acid ester in order to sufficiently bring out the antifogging effect of the sucrose fatty acid ester. And more preferably 0.3 parts by weight or more. Further, in order to maintain the ratio of the sucrose fatty acid ester in the antifogging agent and suppress the application amount of the whole antifogging agent, it is preferable that the amount of the polymer is 5 parts by weight or less based on 1 part by weight of the sucrose fatty acid ester, It is more preferably at most 3 parts by weight. Therefore, if both the anti-fogging effect and economical efficiency are satisfied, the polymer is preferably 0.1 to 5 parts by weight, more preferably 0.3 to 3 parts by weight, per 1 part by weight of the sucrose fatty acid ester. Department.

A mixture of a sucrose fatty acid ester and a polymer-type anti-fog agent has sufficient anti-fog performance, and in particular, in order to ensure anti-fog performance in a deep drawn product, at least one side of a resin sheet. It is preferable to uniformly adhere to the surface at a rate of 10 mg / m ² or more, and particularly preferably 15 mg / m ² or more. On the other hand, 2000 mg /
m ² or less, more preferably 20
0 mg / m ² or less.

Therefore, if both the anti-fogging effect and the economy are satisfied, the coating amount on one side is 10 to 2000 mg / m 2.
² , more preferably 15 to 20
0 mg / m ² .

In the present invention, it is generally said that by increasing the wettability index of the sheet surface to improve the coating property, it is effective in preventing the antifogging agent from peeling and improving the long-term antifogging property. The corona discharge treatment described above can be used in combination, and the treatment may be performed immediately before the application of the antifogging agent. However, since the antifogging agent of the present invention has a large coating strength of the antifogging layer when applied to a sheet and is excellent in stretchability during thermoforming, it can impart excellent antifogging performance without corona discharge treatment. Can be.

In the present invention, it is possible to apply silicone which is usually used as a release agent. In general, it is applied to the reverse side with anti-fogging properties, but conventionally, if the amount of silicone applied is large when wound up into a roll, it mixes with the anti-fogging agent as described above, resulting in poor appearance There was fear. However, in the present invention, the antifogging layer is formed of a completely solid layer, and there is no risk of appearance failure due to mixing, so that the amount of silicone required for release can be arbitrarily applied. In some cases, it is also possible to apply after forming an antifogging layer.

The method of applying the antifogging agent of the present invention does not require the use of any special apparatus or method, and the antifogging liquid diluted with water and / or alcohol is usually used as a spray type coating machine, brush coating, or roll. All coating methods such as a coater, a reverse roll coater, a gravure coater, a knife coater, and a dipping method in which a sheet is immersed in a coating solution once can be used. In order to impart efficient anti-fogging properties with a small amount of anti-fogging agent, it is preferable to form a continuous anti-fog layer having a uniform thickness by attaching and drying as uniformly as possible.

The thermoforming may be performed by vacuum forming, air forming, hot plate forming, plug assist forming, reverse draw forming, air slip forming, or a combination thereof.

The antifogging agent of the present invention can provide good antifogging performance even when used for any transparent resin sheet. Examples include polyester sheet (A-PET), polystyrene, polycarbonate, polymethyl methacrylate, polyvinyl chloride, and the like.

[0028]

When the antifogging agent of the present invention is applied to a transparent resin sheet, excellent antifogging properties can be imparted while maintaining the appearance. The sheet subjected to the coating treatment can maintain excellent anti-fog performance even when subjected to high-temperature thermoforming or high-stretching thermoforming in which a decrease in anti-fog performance has conventionally been observed. Also, the container obtained by thermoforming the coated sheet has excellent anti-fogging properties, and in particular, the deep drawing container which has been difficult to impart conventionally has excellent anti-fogging properties. In addition, the antifogging agent of the present invention forms a strong antifogging layer when applied to the surface of the sheet, so that it does not adhere to and peel off from the opposite surface of the sheet even when wound into a roll, so that the antifogging agent is applied to both sides of the sheet The property can also be given.

[0029]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the present invention is limited thereto.
In addition, each characteristic value was measured according to the following method.

(1) Softening temperature DMA (Dynamic Mechanical Analyze manufactured by DuPont)
The elastic modulus of the antifogging agent was measured using r). A sample in the form of a film was prepared, and measured at a temperature rising rate of 2 K / min and a resonance frequency.

(2) Sheet appearance The haze (haze value) of the sheet was measured using a haze meter NDH-20D manufactured by Nippon Denshoku Co., Ltd. in accordance with a method according to JIS-K-7105, and evaluated according to the following criteria. went. Sheet haze of 1.5% or less: ○ Larger than 1.5 and 3.0% or less Δ: Greater than 3.0% ×

(3) Polyester Sheet Viscosity Measurement was carried out at a concentration of 1.0 g / dl and a temperature of 20 ° C. using a mixed solvent of phenol and tetrachloroethane in a weight ratio of 6: 4.

(4) Evaluation of antifogging property 100 ml of hot water at 50 ° C. was poured into a cup-shaped container body having a diameter of 100 mm and a depth of 55 mm, and the thermoformed product of the present invention shown in (9) Was completely sealed. After being left for 5 minutes in an environment of 20 ° C., visual confirmation was performed, and the evaluation was made according to the following criteria. Those with no fogging ○ Those with a large number of water droplets or those with very slight fogging △ Those with fogging ×

(5) Evaluation of long-term antifogging property The antifogging property after standing for 60 minutes was evaluated in the same manner as in the above antifogging property. The evaluation was performed based on the same criteria.

(6) Adhesion amount of silicone and antifogging agent The adhesion amount of silicone was determined by attaching an extract extracted from a sheet using normal heptane to a KRS plate, and applying FT-IR
Measured the absorption intensity at 800 cm ^-1 . The absorption intensity was measured at 800 cm ^-1 while changing the amount of silicone in advance, and a calibration curve was prepared. The amount of adhesion per unit area was determined by quantification from the value of the absorption intensity. The amount of the antifogging agent attached was extracted in the same manner as in the measurement of silicone, and the amount of sucrose fatty acid ester was determined from the absorption intensity of the hydroxyl group at 3380 cm ^-1 . With respect to the mixed polymer, calculation was performed based on the mixing ratio in advance, and the amount of adhesion was estimated.

(7) Sheet Surface Temperature The sheet surface temperature during thermoforming was measured using an infrared radiation thermometer manufactured by Minolta.

(8) Stretching ratio The thickness of the molded product was measured with a micrometer and compared with the original thickness of the sheet to determine the stretching ratio. Stretch ratio = (original thickness of sheet / measured thickness of molded product)

(9) Production of Molded Article A-PET sheet having a thickness of 500 μm
V = 0.70) The antifogging agent aqueous solution adjusted to various compositions, and the silicone oil on the reverse side, respectively, were applied and dried using a spray type applicator, and the sheet was applied with the adhesion amount shown in Table 1 and wound up. Was. Further, the sheet subjected to the surface treatment was vacuum-molded to produce molded articles having various draw ratios (cup shape having a diameter of 100 mm, and a lid having a container depth of 30 to 70 mm).

The stretching ratio of the top plate portion of the obtained molded product is 1.6 to 2.0 times when the container depth of the lid is 30 mm (1.8 times on average) when the container depth of the lid is 40 mm. 2.5 to 2.9 times (2.7 times on average) when the container depth of the lid is 50 mm 3.3 to 3.9 times (3.6 times on average) When the container depth of the lid is 60 mm The time was 4.2 to 4.8 times (4.5 times on average).

The coating agents used are as follows. Sucrose laurate ester: LWA-1570 manufactured by Mitsubishi Chemical Foods Co., Ltd. (monoester: di-triester = 70:30) Acrylic polymer 1: Jurimer SP-50-TF (polymer type manufactured by Nippon Pure Chemical Co., Ltd.) Surfactant softening temperature 55 ° C) Acrylic polymer 2: Julimer SPO-600 (manufactured by Nippon Pure Chemical Co., Ltd.) (polymeric surfactant softening temperature 80 ° C) Silicone oil: KM-787 manufactured by Shin-Etsu Silicone Co., Ltd.

Comparative Examples 1 to 4 Even if sucrose laurate alone is used, good antifogging performance can be imparted by performing low-temperature thermoforming at a low sheet surface temperature so that the stretching ratio does not exceed 2 times. It is possible. However, when the thermoforming temperature is high or when the stretching ratio is high, the anti-fogging performance rapidly decreases, and the anti-fogging property is not improved even if the amount of adhesion is increased. Further, when the amount of the anti-fogging agent is large, the anti-fogging agent is mixed with the silicone coated on the opposite surface, and causes poor appearance.

Examples 1 to 7 On the other hand, when sucrose laurate and an acrylic polymer are used in combination, excellent antifogging properties can be imparted without impairing the appearance. Since the anti-fog layer constitutes a flexible layer that can be stretched during thermoforming, it can be seen that there is a remarkable effect of improving the anti-fogging property at the time of high stretching, which is a drawback of sucrose laurate. Since the antifogging agent forms a solid layer, even when the amount of adhesion of the antifogging agent or silicone is increased, the appearance is extremely excellent because the two do not mix with each other. Also, conventionally, when thermoformed at a high temperature, there has been a problem that the anti-fog performance sharply decreases,
It can be seen that the antifogging performance does not decrease even when high-temperature thermoforming is performed by the combined use. Furthermore, the combined use of the polymer makes it difficult for the antifogging agent to be washed away by water vapor, thereby improving the long-term antifogging performance.

[0043]

[Table 1]

Continuation of the front page (51) Int.Cl. ⁷ Identification code FI Theme coat II (reference) C08K 5/103 C08K 5/103 C08L 33/00 C08L 33/00 // B29K 101: 12 B29K 101: 12 105: 32 105 : 32 B29L 7:00 B29L 7:00 9:00 9:00 (72) Inventor Koji Kutama 4-1 Kanebo-cho, Hofu-shi, Yamaguchi Prefecture Inside Kanebo Goden Co., Ltd. (72) Yoshio Yasumura Hofu, Yamaguchi Prefecture No. 4-1 Kanebo Go-Fen Co., Ltd. (72) Inventor Tsukasa Kitazono No. 4-1 Kanebo Go-Fen, Hofu-shi, Yamaguchi F-term (reference) 4F006 AA15 AA17 AA22 AA35 AA36 AB64 BA10 CA07 4F100 AJ03B AJ03C AJ03H AK01A AK01B AK01C AK25B AL06B AL06C AL06H BA02 BA03 BA06 BA10A BA10B BA10C CA10B CA10C CC00B CC00C DA01 GB16 JL01 JN01 4F208 AA13 AA15 AA21B03 AB011B02 AB01 AB02 AB19 AB12 AB12 AB12 AB12 GG01 GG02

Claims (6)

[Claims] 1. An anti-fogging agent comprising a sucrose fatty acid ester and a polymer. 2. The antifogging agent according to claim 1, wherein the polymer has a softening temperature of 35 to 180 ° C. 3. The antifogging agent according to claim 1, wherein the polymer is an acrylic polymer. 4. The antifogging agent according to claim 1, wherein the polymer is an acrylic polymer type surfactant. 5. A resin sheet on which at least one surface is coated with the anti-fogging agent according to claim 1. 6. A molded article obtained by thermoforming a sheet, wherein the sheet is the resin sheet according to claim 5.