JPH1060420A - Antifogging agent and resin sheet treated with the antifogging agent - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an anti-fogging agent containing a specific polyglycerin fatty acid ester as a main component, particularly to provide a transparent thermoplastic resin sheet with a more excellent anti-fogging effect than before. . SOLUTION: 70% by weight or more of the constituent fatty acids has 1 carbon atom.
An anti-fogging agent comprising a polyglycerol fatty acid ester having 2 to 16 saturated fatty acids and having an average esterification rate of 25% or less as an active ingredient, and optionally containing an anionic surfactant; Treated resin sheet.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an antifogging agent and a resin sheet treated with the antifogging agent. More specifically, an antifogging agent for a thermoplastic resin sheet, which imparts a superior antifogging effect to a transparent thermoplastic resin sheet widely used in the field of food packaging materials and agricultural covering materials, and the antifogging agent. It relates to a resin sheet treated with a fogging agent. In the present specification, the sheet is usually a sheet or a film used as it is as a packaging material or a coating material, and is further formed into a sheet, and then heated and formed by a direct heating method or an indirect heating method to obtain a desired container shape. And the like.

[0002]

2. Description of the Related Art A thermoplastic resin sheet having excellent transparency is advantageous in that products shielded by the sheet can be easily distinguished and that moisture is hardly permeated and the moisture content of the products is retained. It is widely used for packaging materials for various foods, agricultural covering materials, and the like. However, since the surface of the resin sheet is extremely hydrophobic, water (water vapor) that condenses in response to changes in temperature and humidity forms an aggregate of minute water droplets without uniformly wetting the resin surface, and causes so-called clouding. Often occurs. The occurrence of such fogging makes it difficult to identify stored items in the field of food packaging materials, so not only reduces the commercial value of various containers formed from resin sheets, but also the quality of stored food. Causes deterioration and corruption. Further, in the field of agricultural covering materials, the penetration of sunlight is reduced, which has an unfavorable effect on growing crops.

Heretofore, sucrose fatty acid esters (hereinafter abbreviated as SE) have been widely used as a highly safe antifogging agent in order to prevent such a fogging phenomenon (Japanese Unexamined Patent Publication No. Sho 56).
166234, JP-A-57-80431, JP-B-61
There is a problem that the antifogging performance is lowered after molding or the sheet is colored. That is, most of the thermoplastic resin sheet is heated by a direct heating method or an indirect heating method or the like after sheeting and molded into a container having a desired shape, but when the molding temperature is relatively high at 120 ° C. or higher, When the sheet surface that has been subjected to anti-fogging treatment by SE is heated, the anti-fogging performance of the molded product is lowered due to peeling or decomposition of the anti-fogging agent, or in some cases, it shows completely anti-fogging property Some things have not happened.

As antifoggants for food packaging materials, besides SE, (1) glycerin fatty acid esters (JP-B-38-414)
7, JP-B-52-26532), (2) polyethylene glycol fatty acid ester (JP-B-39-211)
No. 12) and (3) polyglycerin fatty acid esters (Japanese Patent Application Laid-Open Nos. 59-71352 and 61-15755).
8, JP-A-6-212095) and the like, and these are good antifogging agents that hardly cause decomposition or coloring even at a relatively high molding temperature. However, in any case, these are methods in which a resin is blended with an anti-fogging agent and kneaded to form a sheet. Therefore, in order to obtain sufficient anti-fogging performance, a large amount of these must be added. There is a problem that a phenomenon such as whitening due to blooming of the container after molding and stickiness due to bleed-out occur.

[0005]

Therefore, an operation for maintaining excellent antifogging performance corresponding to a thermoplastic resin sheet and a container formed by heating the resin sheet, and for imparting the antifogging property to the resin sheet. There is also a need for a simple antifogging agent.

[0006]

Means for Solving the Problems The present inventors have intensively studied an antifogging agent which has excellent antifogging performance even after molding and does not impair the transparency of a resin sheet. Polyglycerin fatty acid ester (hereinafter, Po
Abbreviated as GE. Has been found to exhibit a remarkable anti-fogging effect by a simple processing method such as coating, and has completed the present invention. That is, one of the gist of the present invention is to provide an anti-fogging agent which provides an anti-fogging effect superior to conventional ones, particularly to a transparent thermoplastic resin sheet, which is present in the present invention. 70% by weight or more of the fatty acid is a saturated fatty acid having 12 to 16 carbon atoms, and is present in an anti-fogging agent containing PoGE as an active ingredient and having an average esterification rate of 25% or less. Another aspect of the present invention resides in a resin sheet surface-treated with the antifogging agent.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
In PoGE which is an active ingredient of the antifogging agent of the present invention, PGE
More than 70% by weight of the constituent fatty acids of oGE have 12 carbon atoms.
To 16 saturated fatty acids, and specifically, lauric acid, myristic acid, and palmitic acid can be used alone or in combination of two or more at any ratio. If the saturated fatty acid has less than 12 carbon atoms, the affinity for the resin sheet may be undesirably reduced. Further, when the number of carbon atoms exceeds 16, the solubility of the coating agent in water decreases, it becomes difficult to prepare an aqueous solution as a surface treatment agent, and further, the transparency of an object to be treated such as a resin sheet may be significantly reduced. It is not preferable. PoGE may be contained as a constituent fatty acid,
As fatty acids other than saturated fatty acids having 12 to 16 carbon atoms,
Any of saturated fatty acids and unsaturated fatty acids may be used.
0-18 fatty acids are preferred. Specifically, capric acid,
Stearic acid, oleic acid and the like can be mentioned.

The average esterification rate of the PoGE of the present invention is 25
%, Particularly preferably 5 to 25%. If it is less than 5%, the antifogging performance may decrease. If it exceeds 25%, the solubility of the coating agent in water decreases, making it difficult to prepare an aqueous solution as a surface treatment agent. This is not preferable because the transparency of the object to be treated may significantly decrease.

The average esterification rate of PoGE was calculated by the following method. Polyglycerin (hereinafter PoG)
May be abbreviated. ) Is obtained from the amount of fatty acid and PoG obtained by saponifying the PoGE obtained by the reaction between the fatty acid and the fatty acid. When the sample contains unreacted PoG, the unreacted PoG content in the sample is determined in advance,
This needs to be deducted.

[0010] The average degree of esterification (%) = [(moles of constituent fatty acids) / (Configuration total hydroxyl number of moles of PoG)] × 100 = _{[(FA / M FA) / [} (PoG E / M PoG) × (n + 2)]] × 100 FA: samples saponification, recovered fatty acid weight (g) M _FA: molecular weight of the fatty acid PoG _E: samples saponification, recovered PoG weight (g) M _PoG: molecular weight of PoG (M _PoG = 74n + 18) n: average degree of polymerization of PoG

[0011] PoG constituting PoGE is produced by any known method. In general, a method in which a small amount of an acid or an alkali is added to glycerin as a catalyst and heated at a high temperature of 180 ° C. or more under normal pressure or reduced pressure. If necessary, after completion of the reaction, treatments such as neutralization and desalting may be performed. The degree of polycondensation of PoG is not limited and may be any value, but is usually 4 or more, and particularly preferably 4 to 20, particularly 6 to 6 in view of safety as a food additive of its esterified product PoGE. A range of 12 is preferred.

PoGE is produced by an esterification reaction between PoG and a fatty acid or a transesterification reaction with a fatty acid ester, and is usually carried out at a high temperature of 130 ° C. or higher in the presence of an alkali catalyst. As the reaction system, any of a reduced pressure system and a normal pressure system can be used. If necessary, neutralize after completion of the reaction,
Processing such as desalination is performed. Alternatively, esterification may be performed enzymatically using lipase or the like. The obtained PoGE may contain unreacted PoG, or may be subjected to purification treatment such as removal of coloring components and odor components by steam distillation or the like. Furthermore, a mixture obtained by appropriately mixing PoGE obtained under different reaction conditions can also be provided.

The PoGE used in the present invention needs to have an average esterification rate of 25% or less.
In the esterification reaction, the esterification rate can be controlled by adjusting the charge ratio of the raw material fatty acid and PoG, and in some cases, a high esterification rate of P
It can also be obtained by partially saponifying oGE.

[0014] In addition to PoGE, various anionic surfactants may be added to the antifogging agent of the present invention. Examples of the anionic surfactant include fatty acid salts, fatty acid sulfonic acid salts, fatty acid lactic acid ester salts, and organic acid monoglyceride salts. Fatty acids constituting these fatty acid salts, fatty acid sulfonic acid salts and fatty acid lactic acid ester salts have 8 to 8 carbon atoms.
22, saturated, unsaturated, branched-chain ones, specifically, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid,
Oleic acid, elaidic acid, ricinoleic acid, 2-butyloctanoic acid, 2-hydroxydecanoic acid and the like can be mentioned. These fatty acids may be a mixture of two or more kinds having an arbitrary ratio. The organic acid monoglyceride is specifically acetic acid monoglyceride, succinic acid monoglyceride,
Citric acid monoglyceride and lactic acid monoglyceride.

Examples of the basic substance forming the salt include alkali metal salts such as sodium and potassium or alkaline earth metal salts such as magnesium, alkanolamines such as ethanolamine, and lower alkylamines such as tributylamine. Among these, lauric acid, myristic acid, palmitic acid and oleic acid are preferred as constituent fatty acids. Further, as the basic substance, an alkali metal is preferable, and potassium is particularly preferable.

These anionic surfactants are PoGE
Is preferably added in an amount of 0.01 to 10% by weight. If the amount of the anionic surfactant is less than 0.01% by weight, the solution may become cloudy even if the antifogging agent is applied as a solution or the like to a resin sheet or the like. The appearance such as transparency may be deteriorated. Even if the content exceeds 10% by weight, the effect reaches a plateau and may be economically disadvantageous.

The resin sheet of the present invention includes not only sheets and films which are usually used as they are as packaging materials or coating materials, but also those which are further molded and used as containers. The resin sheet generally has a thickness of about 10 μm to 10 mm. For example, a sheet having a thickness of about 10 to 100 μm is used as it is as a packaging material, and a sheet having a thickness of about 0.01 to 10 mm is molded and used as a container. As an example of molding, for example, a thickness of 0.0
After forming into a sheet of 1 to 10 mm, the sheet is heated by a direct heating method or an indirect heating method, and then formed into a target shape.

The resin sheet of the present invention is a sheet made of a thermoplastic resin. Specifically, the resin sheet is made of polystyrene, polyvinyl chloride, polyvinylidene chloride, polyethylene, polypropylene, polyethylene terephthalate, polycarbonate, etc. Transparent resin sheets used in the field of coating materials for automobiles.

The surface treatment method of the antifogging agent containing PoGE as an active ingredient on the resin sheet is optional. For example, a simple method of coating the surface of the resin sheet with a roll coater, a knife coater, a gravure roll coater or the like can be mentioned. In some cases, techniques such as spraying and dipping may be employed. When applying to the surface, it is preferable to apply it as a 0.01 to 5% by weight antifogging agent solution and then dry it. Examples of the solvent used for the antifogging agent solution include, for example,
A solvent that dissolves an anti-fogging agent such as water or alcohol and does not dissolve the resin sheet, and furthermore, depending on the application field, it is preferable to appropriately select and use a solvent that satisfies safety. On the surface of the resin sheet, an antifogging agent having a solid content of 0.005 to
It is preferable to apply 0.5 g / m ² . If the treatment amount of the antifogging agent is less than these, the antifogging effect may be reduced, and if the treatment amount is exceeded, blocking of the sheets due to stickiness and a decrease in transparency may cause surface whitening. There is.

In the antifogging agent of the present invention, various plasticizers, various stabilizers, lubricants, pigments, antiblocking agents,
A viscosity modifier, an antifoaming agent, an ultraviolet absorber, a coloring inhibitor and the like can be appropriately used in a conventional manner. The resin sheet thus obtained is further heated and formed into a desired container shape, and the resin sheet is directly heated by a metal plate that also functions as a molding die heated to 120 to 150 ° C. A container having a desired shape can be obtained by a heating method or a heating molding method such as an indirect heating method in which a resin sheet slightly softened by heating with a heater is molded with a relatively low temperature mold.

[0021]

The present invention will be described below in detail with reference to examples.
The present invention is not limited in any way by these examples unless exceeding the gist. The evaluation in the examples was performed as follows.

(A) Transparency of antifogging agent coating liquid The transparency of the 0.4% by weight aqueous solution of the antifogging agent was measured using a spectrophotometer (UV-1200, manufactured by Shimadzu Corporation) at a wavelength of 650 n.
The transmittance was measured in m. Evaluation criteria ◎: transmittance is 95% or more 以上: transmittance is 90% or more and less than 95% Δ: transmittance is 80% or more and less than 90% ×: transmittance is less than 80%

(B) Antifogging property A sample sheet was prepared by placing 500 cc of 90 ° C. hot water in 300 cc.
A beaker of cc (diameter: 90 mmΦ) was placed on the mouth of the beaker, and heated at 90 ° C., and the adhesion state of water droplets on the inner surface of the sheet was visually observed. Evaluation criteria A: No fogging is observed. ：: No clouding is observed, but many large water droplets are observed. Δ: Less than 20% of the anti-fogging treated surface is clouded by minute water droplets and exhibits an opaque state. ×: 20% or more of the anti-fog treatment surface is clouded by minute water droplets, and exhibits an opaque state.

(C) Sheet Transparency The sheet appearance is HDM-2DP (manufactured by Suga Test Instruments Co., Ltd.).
The haze (haze) H (%) measured by the above method and the appearance observed with the naked eye were evaluated, and the lower evaluation result was regarded as the evaluation result of the sheet transparency. Evaluation criteria A: H <1.5 or no coating spots were observed. ：: 1.5 ≦ H <2 or very slight spots are observed. Δ: 2 ≦ H <3 or coating spots are slightly conspicuous. ×: 3 ≦ H or spots are considerably conspicuous.

Examples 1 to 16 and Comparative Examples 1 to 9 1.6% by weight of PoGE consisting of the constituent fatty acid species and the average esterification rate shown in Table 1, and optionally potassium laurate (anionic surfactant) ) Was prepared to prepare an anti-fogging agent solution. The above antifogging agent solution is applied to a polypropylene (PP) sheet (thickness: 250 μm)
After applying 0.5 g / m ² as a solid antifogging agent to one side of
It was immediately dried to obtain a resin sheet. In Comparative Example 8, a 1.6% by weight aqueous solution of sucrose laurate was prepared.
g / m ² was obtained as a resin sheet. These antifogging resin sheets were evaluated for antifogging test, and the evaluation results are shown in Table 1. Further, this resin sheet was formed into a container by a compression molding method, and an antifogging test was performed on the container. The results are shown in Table 2. In Comparative Example 5,
The resin sheet to which the antifogging agent was not applied was evaluated.

[0026]

[Table 1]

[0027]

[Table 2]

In the above table, the following fatty acid species were used. Lauric acid: NAA-122 manufactured by NOF Corporation Myristic acid: NAA-142 manufactured by NOF Corporation Palmitic acid: NAA-160 manufactured by NOF Corporation Stearic acid: ST-750 oleic acid manufactured by Kao Corporation: Nippon Oil & Fats Co., Ltd. NAA-34 Polyglycerin: Sakamoto Co., Ltd. # 750 Sucrose laurate: Mitsubishi Chemical Foods Co., Ltd. LW
A-1570 (HLB15) The PoGE used in this example and comparative example is shown in Table-
The constituent fatty acid species described in No. 1 and PoG were added at a predetermined ratio, and sodium hydroxide was added as a 10% aqueous solution, and the mixture was reacted without using a solvent.

Examples 17 to 19, Comparative Examples 10 to 12 The resin sheet was a polyethylene terephthalate (PET) sheet (thickness: 1 mm), and the antifogging agent solution was 0.4% by weight.
The procedure was performed in the same manner as in Examples 12 to 16 and Comparative Examples 6 to 9 except that an aqueous solution was applied and 0.04 g / m ² as an antifogging solid content was applied. The results are shown in Table 3.

[0030]

[Table 3]

[0031]

The anti-fogging agent of the present invention comprises a specific PoGE as an active ingredient, and by applying this anti-fogging agent to a resin sheet, a transparent heat-resistant material widely used in the field of food packaging materials and agricultural coating materials. A superior antifogging effect can be imparted to the plastic resin sheet as compared to the conventional one, and the thermoplastic resin sheet treated with this antifogging agent does not lose transparency and has excellent antifogging properties.

Claims (7)

[Claims] Claims: 1. More than 70% by weight of the constituent fatty acids have 1 carbon atom.
An anti-fogging agent comprising a polyglycerin fatty acid ester having 2 to 16 saturated fatty acids and having an average esterification rate of 25% or less as an active ingredient. 2. Polyglycerin fatty acid ester and 0.0
2. An antifogging agent according to claim 1, comprising 1 to 10% by weight of an anionic surfactant. 3. The antifogging agent according to claim 1, which is an antifogging agent for a resin sheet. 4. The antifogging agent according to claim 3, wherein the resin sheet is a resin sheet selected from the group consisting of polystyrene, polyvinyl chloride, polyvinylidene chloride, polyethylene, polypropylene, polyethylene terephthalate, and polycarbonate. 5. A resin sheet treated with the anti-fogging agent according to claim 1. 6. The resin according to claim 1, wherein the resin is polystyrene, polyvinyl chloride,
Polyvinylidene chloride, polyethylene, polypropylene,
6. A resin selected from the group consisting of polyethylene terephthalate and polycarbonate.
The resin sheet of the above. 7. The resin sheet according to claim 5, which is surface-treated with an aqueous solution containing 0.01 to 5% by weight of the antifogging agent according to any one of claims 1 to 4.