JPH09194655A - Antifogging agent for styrenic resin film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an antifogging agent which, when added to a styrene resin, can impart an excellent antifogging property to a film particularly at a low temp. by compounding a polyglycerin fatty acid ester having a high degree of monoesterification and synthesized from a fatty acid compd. with glycidol. SOLUTION: This antifogging agent comprises a polyglycerin fatty acid ester having a high degree of monoesterification and synthesized from a fatty acid or a glycerol fatty acid ester and glycidol. The fatty acid ester is prepd. by addition polymn. of glycidol an a fatty acid compd. in the presence of an acidic catalyst based on phosphoric acid and has a monofaty acid ester content of not less than 70% in terms of the ration of peak area detected with an ultravioled absorption detector by column chromatography. The starting fatty acid may be any of 7-22C satd., unsatd., straight-chain and branched fatty acids and hydroxyl-substd. fatty acids. The antifogging agent can impart a persistent and excellent antifogging property at a low temp. to a styrenic resin film.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an antifogging agent for a styrene resin film, and more specifically, it is more durable than a styrene resin film used for food packaging by adding a smaller amount than before. The present invention relates to an antifog agent for a styrene-based resin film, which can impart an antifog effect.

[0002]

BACKGROUND OF THE INVENTION Styrenic resins are excellent in transparency, tasteless, odorless, nontoxic and highly water resistant. However, although it has strength but has a problem in brittleness, it has been improved to have impact resistance and has been widely used as a film for food packaging.

Since the styrene resin film is hydrophobic, it has various problems when used as a food packaging film. When used for food packaging, when moisture-containing foods such as vegetables and meat are packaged and stored at low temperature, the moisture condenses on the inner surface of the film to form water droplets.

The generation of water droplets impairs the transparency of the film, makes it impossible to see through the contents, is not preferable in appearance, and deteriorates the image of the product. As a method for solving such problems, there is a method of improving the properties of the film surface.

As a method for improving the properties of the film surface, there can be mentioned a method of applying an antifogging agent on the surface or a method of blending a resin with an antifogging agent to form a film. It has excellent properties and has the drawback that the antifogging agent is washed away by the water condensed on the film and its effect is lost. On the other hand, the method of blending with a resin and kneading to form a film is excellent in that a stable antifogging effect can be obtained over time.

As the anti-fogging agent used for the styrene resin by such a method, (1) glycerin fatty acid ester (Japanese Patent Publication No. 38-4147, Japanese Patent Publication No. 52-26532),
(2) Polyethylene glycol fatty acid (Japanese Patent Publication No. 39-2
1112), and (3) polyglycerin monofatty acid ester (JP-A-61-157558) are known.

However, when the glycerin fatty acid ester (1) and the polyethylene glycol fatty acid ester (2) are used in the styrene resin, it is necessary to add a large amount thereof in order to obtain the desired antifogging effect. However, if the addition amount is large, there is a problem in that kneading becomes difficult.

Further, the polyglycerin fatty acid ester of (3) does not specify a fatty acid and contains 60% or more of a monoester, but when used in a styrene resin film, it has good antifogging property at room temperature. , Low temperature anti-fog property, poor compatibility and transparency, not suitable for food packaging under refrigeration.

[0009]

The anti-fogging property required for a styrene resin film used for food packaging must be excellent in terms of low-temperature characteristics, high-temperature characteristics, recoverability, sustainability and the like. Especially, the fog resistance when packaging food and storing it in a cool place for a long time is important.

In order to exhibit a long-lasting antifogging property at a low temperature, the antifogging agent to be blended must have an appropriate compatibility with the resin at a low temperature. When the compatibility is poor, the migration speed (bleeding property) of the antifogging agent to the surface of the styrene resin film is high, and although there is an antifogging effect, sticking of the films occurs due to stickiness on the film surface.
On the other hand, if the compatibility is too good, the amount of the antifogging agent transferred to the film surface will be small, and the antifogging effect will not be exhibited. Therefore,
The antifogging agent should have a good bleeding property and compatibility with the synthetic resin.

The internal addition type antifog agent used in the conventional polystyrene resin has a good compatibility with the resin and is therefore included therein, requiring a large amount of 7 to 8% to be added. However, addition of a large amount of antifogging agent causes problems such as poor workability and handleability during film processing, and also impairs transparency of the film itself.

[0012]

Means for Solving the Problems The present invention has been made in view of the above points, and by using a polyglycerol fatty acid ester having a high monoesterification rate synthesized from a fatty acid or glycerin fatty acid ester and glycidol, The present inventors have found an anti-fogging agent for a styrene resin film, which can impart excellent anti-fogging property with a smaller addition amount than before. That is, the present invention is an antifog agent for a styrene resin film comprising a polyglycerin fatty acid ester having a high monoesterification rate, which is synthesized from a fatty acid or a glycerin fatty acid ester and glycidol.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Conventionally, as a method for producing a polyglycerin fatty acid ester, (1) an esterification reaction between polyglycerin and a fatty acid {JAOCS (Journal of Ameri
can Oil Chemists' Society) 58, 878 (1981
Year), refer to JP-A-6-41007, etc.}, (2)
Transesterification reaction of polyglycerin with fatty acid ester, (3) transesterification reaction of polyglycerin with oil and fat, (4) addition polymerization reaction of glycidol with fatty acid monoglyceride {see USP 4,515,775},
(5) Addition polymerization reaction of glycidol and fatty acids (see JP-A-51-65705) is known.

The "polyglycerin fatty acid ester synthesized from fatty acid or glycerin fatty acid ester and glycidol and having a high monoesterification rate" in the present invention is produced by the method (5).

Examples of the raw material fatty acid used include fatty acids having 7 to 22 carbon atoms. The fatty acid may be a saturated fatty acid or an unsaturated fatty acid, may be a linear fatty acid or a fatty acid having a side chain, and may be a substituted fatty acid having a carbon chain substituted with a hydroxyl group. Specific examples of these fatty acids include caproic acid, caprylic acid, 2-ethylhexanoic acid, capric acid, lauric acid, isotridecanoic acid, myristic acid, palmitic acid, palmitoleic acid, stearic acid, isostearic acid, oleic acid, linoleic acid, Examples thereof include behenic acid, erucic acid, ricinoleic acid, hydroxystearic acid and the like. These may be used alone or in any combination of two or more.

The molar ratio of glycidol to fatty acid in the addition polymerization reaction of glycidol and the above fatty acid is
1-100, preferably 1-50, more preferably 1
It is good to choose in the range of ~ 10.

If the molar ratio is less than 1, anti-fogging property cannot be imparted to the styrene resin, and conversely, the molar ratio is 100.
With the above, in polyglycerin fatty acid ester,
The ratio of the hydrophilic group to the hydrophobic group becomes too high, and the compatibility with the styrene resin decreases, which is not preferable.

The addition polymerization reaction of the above fatty acid and glycidol is preferably carried out in the presence of a phosphoric acid-based acidic catalyst, if necessary, in the presence of a solvent. The phosphoric acid-based acidic catalyst used here is phosphoric acid or phosphoric acid ester. Specifically, phosphoric acid, phosphoric anhydride, polyphosphoric acid, orthophosphoric acid, metaphosphoric acid, pyrophosphoric acid, phosphoric acid such as triphosphoric acid, tetraphosphoric acid, methyl acid phosphate, ethyl acid phosphate, isopropyl acid phosphate, butyl acid. Phosphate, 2-
Examples thereof include acidic phosphoric acid esters such as ethylhexyl acid phosphate. The acidic phosphoric acid ester may be a monoester body, a diester body or a mixture thereof. Among the catalysts listed above, phosphoric acid and acidic phosphoric acid esters are particularly preferable.

The above catalysts may be used alone or in admixture of two or more. The amount of the catalyst used was 0.
It is preferable to select in the range of 01 to 10% by weight. If it is less than 0.01% by weight, the reaction rate is too slow, and if it exceeds 10% by weight, the effect is not reached even if a large amount of the catalyst is used, and an addition polymer of glycidol is by-produced. Absent. In the above range of the amount of catalyst used, 0.1-5
% By weight is particularly preferred. The addition polymerization reaction can be carried out without a solvent, but a solvent may be used. As the solvent that can be used, aromatic hydrocarbons having 6 to 9 carbon atoms, particularly halogenated toluene such as benzene, toluene and trifluorotoluene, aliphatic ketones having 3 to 9 carbon atoms, especially methyl isopropyl ketone , Methyl isobutyl ketone, diethyl ketone, di-isobutyl ketone, and the like. Besides, ethers such as diisopropyl ether are also suitable. These solvents may be used alone or as a mixture of two or more kinds. When a solvent is used, the amount used is preferably as small as possible from the viewpoint of recovery operation after completion of the reaction, and particularly preferably twice the total amount of the reaction raw materials.

The reaction temperature varies depending on the presence or absence of a solvent, the type and amount of catalyst, and the like, but it is preferably selected in the range of 50 to 180 ° C. If the temperature is lower than 50 ° C, the reaction rate is too slow, and if it exceeds 180 ° C, not only the coloring of the product becomes severe, but also glycidol is decomposed to cause a side reaction, which is not preferable. In the above temperature range, 70 to 160 ° C is preferable, and 140 to 160 ° C is particularly preferable.

The addition polymerization reaction is preferably carried out by mixing the fatty acid, the solvent and the catalyst in a reaction vessel, heating the mixture to the reaction temperature, and then adding glycidol little by little with stirring. The reaction can be carried out continuously or batchwise. When a solvent is used and its boiling point is below the reaction temperature, it is advantageous to carry out under pressure. It is desirable to carry out the addition polymerization reaction in an inert gas atmosphere such as nitrogen gas.

By the above reaction, glycidol is addition-polymerized with the fatty acid to produce a polyglycerin fatty acid ester having a higher degree of polymerization. The product is a monofatty acid ester form,
The polyglycerin fatty acid ester is a mixture of di-fatty acid ester body and tri-fatty acid ester body, and according to the above reaction, one having a large content ratio of mono fatty acid ester body is obtained. That is, the polyglycerin fatty acid ester obtained by the present invention has a content of 70% or more represented by the peak area ratio of the monofatty acid ester body detected by an ultraviolet absorption detector by a column chromatography analysis method. .

The amount of the anti-fogging agent for a styrene resin film of the present invention added is preferably 0.5 to 8.0% by weight based on the styrene resin. If the addition amount is less than 0.5% by weight, sufficient antifogging property is not exhibited, while if it exceeds 8.0% by weight, the antifogging agent bleeds more than necessary and the film surface becomes sticky. This is not preferable because it causes workability to be significantly reduced. The more preferable addition amount of the antifogging agent of the present invention is 1 to 5 parts by weight.

In the present invention, in order to impart desired characteristics depending on the purpose, conventionally known additives such as stabilizers, lubricants, nucleating agents, mold releasing agents, organic polymer materials, inorganic or organic materials are used. It is also possible to add one or more of the fibrous, powdery, and plate-like fillers, and the like. The composition of the present invention can be prepared by equipment and a method generally known as a method for preparing a synthetic resin composition.

That is, the necessary components can be mixed, kneaded using a uniaxial or biaxial extruder, extruded into molding pellets, and then molded, and the composition can be prepared by a molding machine. It is also possible to perform at the same time as molding. or,
The compounds such as the stabilizers and additives may be added at any arbitrary stage, and it is of course possible to add and mix them just before obtaining the final molded product. Further, the resin composition according to the present invention can be molded by any of extrusion molding, injection molding, compression molding, vacuum molding, blow molding, and foam molding, and particularly in the case of extrusion molding, the effect of the present invention is remarkable. is there.

<Examples> The present invention will be described in more detail with reference to Examples and Comparative Examples below.
The present invention is not limited to these.

Reference Example 1 0.5 mol (100.1) of lauric acid was placed in a 1-liter 4-necked flask equipped with a nitrogen introduction tube, a stirrer, a cooling tube, a temperature controller, and a dropping cylinder.
6g) and 0.0622g of phosphoric acid (85% product)
Heated to 40 ° C. Then, while maintaining the reaction temperature at 140 ° C., 3.0 mol (222.24 g) of glycidol was added dropwise over 5 hours. The temperature was further maintained, and the reaction was continued for 26 hours. After cooling, the reaction product was taken out to obtain about 300 g of hexaglycerin monolaurate.

The obtained polyglycerin monolauric acid ester was subjected to the following high performance liquid chromatography (hereinafter referred to as H
Abbreviated as PLC. ), The monosubstitution rate was 87.7%.

(HPLC analysis conditions) Column: Wakosil 5C18 * 2 Developing solvent: MeOH Flow rate: 0.75 ml / min. Column oven temperature: 40 ° C Detection method: Ultraviolet absorption method (λ = 210 nm) Sample concentration: 10% Injection amount : 5 μl [Reference Example 2] 4.0 mol (296.3) of glycidol
2 g) The same operation as in Reference Example 1 was performed except that it was used, and after cooling, the reaction product was taken out to obtain about 400 g of octaglycerin monolaurate. The obtained polyglycerin monolauric acid ester was evaluated by HPLC. As a result, the monosubstitution rate was 84.5%.

Reference Example 3 5.0 mol of glycidol
(370.40 g) The same operation as in Reference Example 1 was carried out except that the mixture was used. After cooling, the reaction product was taken out to obtain about 470 g of decaglycerin monolaurate. The obtained polyglycerin monolauric acid ester was evaluated by HPLC. As a result, the monosubstitution rate was 77.2%.

Comparative Reference Example 1 / In the Case of Reaction of Fatty Acid with Polyglycerin Polyglycerin [Daicel] was placed in a 1-liter four-necked flask equipped with a nitrogen introducing tube, a stirrer, a cooling tube, a temperature controller and a dropping cylinder. Chemical industry PG
L06; hexaglycerin, hydroxyl value 960] 175.
3 g (0.5 mol) was taken, heated to 80 ° C., and while maintaining the reaction temperature at 80 ° C., 0.5 mol (10 mol) of lauric acid.
0.16 g) was added and dissolved. Next, 0.75 g of sodium carbonate and 0.25 g of sodium bisulfite were added, and an esterification reaction was performed at 210 ° C. After 2 hours of reaction, the acid value became 0.89. After cooling to 100 ° C., the reaction product was taken out.

The polyglycerin monolaurate thus obtained was evaluated by HPLC. As a result, the monosubstitution rate was 55.1%.

[Comparative Reference Examples 2 and 3 / Evaluation results of commercially available polyglycerin fatty acid ester] As the commercially available polyglycerin fatty acid ester produced by the reaction of polyglycerin and fatty acid, SY Glister (manufactured by Sakamoto Yakuhin Kogyo) (ML-500, ML-750) was selected. When these polyglycerin monolauric acid esters were evaluated by HPLC, they were evaluated and found to be ML-500 and ML-750.
The mono-replacement rates of 52.0% and 44.3%, respectively. Moreover, let each be Comparative Reference Examples 2 and 3.

[Examples 1 to 3 and Comparative Examples 1 to 3] 3 parts by weight of the polyglycerin fatty acid ester antifogging agent obtained in the above Reference Examples and Comparative Reference Examples was blended, and a small mixer (die temperature 180 ° C.) was used. And pelletized with a pelletizer and dried. The pellets were molded into a film with a thickness of 30 μm by an inflation molding machine (die temperature: 180 ° C.), and the transparency and heat resistance of the obtained film were adjusted to 25
After conditioning the humidity in a thermo-hygrostat at 65 ° C and 65% Rh for 24 hours,
The antifogging property and the bleeding property after 72 hours were evaluated.

The results are shown in Table 1 and each test method is shown below.

(A) Anti-fogging evaluation test method A sample film was put in 300 cc containing 50 cc of warm water at 40 ° C.
The beaker (with a diameter of 80 mmφ) was attached to the mouth of the beaker, and the beaker was placed in a constant-humidity bath at 5 ° C., and the antifogging property and the durability were evaluated 72 hours later. The evaluation criteria are as follows.

⊚: The entire surface is uniformly wet and has good transparency.

O: Water droplets are partially attached in a drop shape, but are almost transparent.

Δ: Water droplets are considerably attached in the form of drops and are semitransparent.

X: Water droplets adhered to the entire surface and were opaque.

(B) Transparency evaluation test method The sample film of the molding machine was observed to evaluate the transparency. The evaluation criteria are as follows.

◯: The transparency of the film is good.

Δ: The film had a slight turbidity.

X: The film was considerably cloudy.

(C) Heat resistance A test piece (2 cm × 3 cm) was placed in a gear oven at 180 ° C., taken out after 30 minutes, and the discolored state was visually judged by the following evaluation criteria. The evaluation criteria are as follows.

A: Colorless to pale yellow coloring.

Δ: Colored from yellow to light yellowish brown.

X: Colored from brown to blackish brown.

(D) Bleed property After the molding, the surface of the sample film (150 mm × 150 mm) kept at 50 ° C. and 60% Rh for 30 days was placed on a degreased and dried FelloW plate, and after applying a roller from above the film,
The film was peeled off and the bleeding property was evaluated by observing traces on the Fellows plate. The evaluation criteria are as follows.

◯: The contact portion of the fellow board is slightly clouded.

Δ: There is a lot of cloudiness in the contact area of the fellow board.

X: Fogging at the contact portion of the Fellow plate is remarkable.

Table 1 Anti- fogging property Transparency Heat resistance Bleed property Actual PGLE obtained in Reference Example 1 ◎ ○ ○ ○ PGLE obtained in Reference Example 2 ◎ ○ ○ ○ ○ Example PGLE obtained in Reference Example 3 ◎ ○ ○ ○ Ratio PGLE obtained in Comparative Reference Example 1 △ △ △ △ Comparative PGLE obtained in Comparative Reference Example 2 ○ △ ○ △ Example PGLE obtained in Comparative Reference Example 3 ○ △ ○ △ Note PGLE: Polyglycerin fatty acid ester

[0054]

The antifogging agent for styrene resin film of the present invention is polyglycerin fatty acid ester synthesized by a specific production method, and the styrene resin film in which this is kneaded has little bleeding property and heat resistance. It also has the effect of providing an antifogging agent having excellent transparency and having excellent antifogging property that is durable at low temperatures. (Below margin)

Claims (1)

[Claims] 1. An antifog agent for a styrene-based resin film, which comprises a fatty acid or a polyglycerin fatty acid ester synthesized from glycerin fatty acid ester and glycidol and having a high monoesterification rate.