JPH1060465A - Surface-treating agent for metal can - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject treating agent which can lower the friction of the outer surface of a can without adverse effect on the adhesion of paint, lacquer and the like and exhibit high safety to human body by using a specific polyglycerol mono fatty acid ester. SOLUTION: This metallic can surface-treating agent contains a polyglycerol fatty acid ester which contains a compound of the formula (R is a 6-21C alkyl, an alkenyl or an OH-substituted alkyl; (n) is an average oligomerization number and is >=4) whose peak area occupies by >=70% of the whole area in the column chromatography when detected with an ultraviolet absorption detector, for example, prepared by reaction of a carboxylic acid of the formula: RCOOH with glycidol in the presence of a phosphoric acid catalyst, typically octaglycerol monolaurate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface treatment agent for metal cans for reducing friction on the surface of metal cans and improving the handling in the can making process, and more particularly, has an adverse effect on the adhesion of paint and lacquer. The present invention relates to a surface treatment agent for metal cans that reduces the friction on the outer surface of metal cans, particularly aluminum cans, and improves mobility on a belt conveyor without imparting water.

[0002]

2. Description of the Related Art Metal cans are used as containers for various products, and aluminum cans are particularly frequently used as the most common metal cans. Hereinafter, a description will be given of an aluminum can as a representative. After manufacturing the main body of the aluminum can, the aluminum can is washed with an acidic cleaner or the like to remove aluminum fine powder and other contaminants attached in the can making process. Here, alkali cleaning is desired instead of acid cleaner because of recent environmental problems and residual acid liquid remaining on the can after acid cleaning adversely affects the odor of the contents of the can.

[0003]

However, when the alkali cleaning is performed, the outer surface of the can is roughened, and the can does not move smoothly on a belt conveyor in a filling process into the can or a printing process on the can surface. As a result, problems such as erroneous distribution, a decrease in productivity, and an increase in the loss rate of cans may occur. For this reason, it is desired to reduce friction on the outer surface of the can without adversely affecting the adhesion of paint, lacquer, etc. on the outer surface of the can.

For example, as surface treatment agents for metal cans, JP-A-64-85292 discloses phosphate esters, fatty acid ethylene oxide adducts, higher alcohol ethylene oxide adducts, and the like. However, aluminum cans are often used for foodstuffs, and the above compounds are problematic in terms of safety to the human body, and thus are difficult to use as general-purpose surface treatment agents for metal cans. Also, JP-A-6-220472 discloses a metal can surface treatment agent that reduces friction on the outer surface of a can without adversely affecting the adhesion of paint, lacquer, and the like, and that is highly safe for human bodies. It discloses the use of polyglycerin fatty acid esters and the like that are approved as food additives. However, when polyglycerin fatty acid ester is used as the non-electrolyte surfactant, the reduction of the friction on the outer surface of the can is not sufficient. Specifically, the polyglycerin fatty acid ester of the publication is produced by an esterification reaction of polyglycerin and a fatty acid. In this method, the esterification rate is distributed for each molecule, and the molecules having a high esterification rate and the molecules having a low esterification rate are low. Molecules, and in some cases, molecules that have not been esterified are often present, and not only the target monoester but also unreacted polyglycerol, diester, triester, tetraester, and other polysubstituted esterified compounds remain. Therefore, when used as a surface treatment agent for metal cans, poorly water-soluble components remain and remain on the can surface, which is not preferable. In addition, unreacted polyglycerin remains, and the reduction of friction on the outer surface of the can is not sufficient.

The present invention reduces the friction of the outer surface of a can without adversely affecting the adhesion of paint, lacquer, etc.,
It is another object of the present invention to provide a surface treatment agent for metal cans that is highly safe for the human body.

[0006]

The present inventors have studied the polyglycerin fatty acid ester in detail to solve the above-mentioned problems. As a result, the present inventors have found that polyglycerol fatty acid monoester synthesized from fatty acid and glycidol has a high content of polyester. The inventors have found that the above problems can be solved by using glycerin monofatty acid ester, and have completed the present invention.

That is, according to the present invention, the peak area of the polyglycerol monofatty acid ester represented by the following general formula (1), which is eluted by column chromatography and detected using an ultraviolet absorption detector, is 70% or more of the total area. It is intended to provide a surface treatment agent for metal cans, characterized by containing a polyglycerin fatty acid ester. Further, the present invention provides the surface treatment agent for a metal can, wherein the column chromatography analysis is high performance liquid chromatography using an octadecylsilyl group-bonded silica gel column using an alcohol solvent and / or distilled water as an eluent. It is. Further, the surface treatment for a metal can, wherein the polyglycerin monofatty acid ester is obtained by reacting a fatty acid represented by the following general formula (2) with glycidol in the presence of a phosphoric acid acidic catalyst. The agent is provided. In addition, the present invention provides the metal can surface treating agent, wherein the phosphoric acid-based acidic catalyst is phosphoric acid or an acidic phosphoric acid ester. Hereinafter, the present invention will be described in detail.

[0008]

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[0009]

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[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The polyglycerol fatty acid ester used in the present invention contains at least 70% of a monofatty acid ester represented by the above general formula (1), and is produced by an addition polymerization reaction of glycidol and a fatty acid. can do. The fatty acid may be a saturated fatty acid or an unsaturated fatty acid as long as it has 6 to 22 carbon atoms, and may be a linear fatty acid, a fatty acid having a side chain, or a hydroxyl-substituted fatty acid. Specifically, 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, behenic acid, erucic acid, ricinoleic acid, hydroxystearic acid and the like can be exemplified. These can be used alone or in combination of two or more.

The reaction between the fatty acid and glycidol is preferably carried out in the presence of an acidic catalyst. Examples of the acidic catalyst include phosphoric acids and esters of phosphoric acid. Specific examples thereof include phosphoric acid, phosphoric anhydride, polyphosphoric acid, orthophosphoric acid, metaphosphoric acid, pyrophosphoric acid, triphosphoric acid, and tetraphosphoric acid. Acids or acid phosphates such as methyl acid phosphate, ethyl acid phosphate, isopropyl acid phosphate, butyl acid phosphate, and 2-ethylhexyl acid phosphate can be used. In addition, as these acidic phosphates, any of a monoester body, a diester body, and a mixture thereof can be used. Further, one kind of the above-mentioned acidic catalyst may be used alone, or two or more kinds may be used in combination.

The amount of the catalyst added is 0.01 to
It is preferably 10% by weight, more preferably 0.1 to 5% by weight. If the amount is less than 0.01% by weight, the reaction rate is low. On the other hand, if the amount exceeds 10% by weight, the effect cannot be expected to be improved. This is because a large number may be generated.

[0013] The addition polymerization reaction is carried out by taking a fatty acid in a reaction vessel, adding the above-mentioned catalyst thereto, and adding glycidol little by little. The reaction temperature is 50 to 180 ° C, preferably 70 to 160 ° C, more preferably 120 to 140 ° C.
° C. If the temperature is lower than 50 ° C., the reaction rate is low.
If the temperature exceeds 0 ° C., coloring becomes severe. Particularly, at 230 ° C. or higher, glycidol is decomposed to cause a side reaction, which is not preferable. A low-boiling compound that does not react with glycidol may be added to the addition polymerization reaction in order to prevent an increase in the reaction temperature. The reaction is desirably performed in a nitrogen gas atmosphere, and may be pressurized if necessary.

Water is added to the obtained reaction solution containing the polyglycerol fatty acid ester, followed by heating and dehydration, whereby unreacted glycidol contained in the reaction solution and oxirane group-containing compounds considered as by-products are removed. The derived oxirane group concentration can be reduced. The amount of water to be added is preferably selected in the range of 0.1 to 20% by weight, particularly preferably in the range of 1 to 10% by weight, based on the polyglycerin fatty acid ester contained. If the amount of water is less than 0.1% by weight, unreacted glycidol cannot be sufficiently reduced, while if it exceeds 20% by weight, the post-treatment operation becomes complicated, which is not preferable. Unreacted glycidol can be converted to glycerin by heating. The heating temperature is preferably in the range of 60 to 200 ° C, particularly preferably in the range of 80 to 160 ° C. If the heating temperature is lower than 60 ° C., the concentration of unreacted glycidol and remaining oxirane groups cannot be sufficiently reduced, while if it exceeds 200 ° C., the product polyglycerin fatty acid ester is colored. The heating time is 0.5 to 15 hours, particularly preferably 1 to 7 hours, depending on the temperature. Dehydration can be performed by distillation, azeotropic distillation, vacuum distillation, or the like. The heating temperature during the distillation is preferably selected in the range of 100 to 200 ° C, particularly preferably in the range of 110 to 160 ° C. If the heating temperature is lower than 100 ° C., it is not sufficient to remove water contained in the polyglycerin fatty acid ester of the product, while if it exceeds 200 ° C., the product polyglycerin fatty acid ester is undesirably colored. . The time for dehydration depends on the temperature and the degree of pressure reduction, but is preferably in the range of 1 to 10 hours, and particularly preferably in the range of 1 to 6 hours. When a solvent is used, it can be removed by this dehydration operation, but may be removed by another operation.

The content of the monofatty acid ester in the obtained polyglycerin fatty acid ester is measured according to the following analysis conditions. Reversed-phase partition column analysis using silica gel bonded with octadecylsilyl group (ODS group), octylsilyl group, butylsilyl group, trimethylsilyl group, and phenylsilyl group as a carrier, silica gel having aminopropyl group and cyanopropyl group as a carrier A normal phase distribution column analysis method includes an ion exchange column analysis method using silica gel having a quaternary ammonium group and a phenylsulfonic acid group as a carrier, and an adsorption column analysis method using porous silica gel as a carrier. Among these, a reversed-phase partition column analysis method using silica gel to which an octadecylsilyl group is bonded as a carrier is preferable. Also,
The column size is 4.6mmφ to improve the resolution
250 mm or more is preferable, and connecting columns in series is more preferable because the separation capacity can be improved.

The case of analysis by the reversed phase distribution column analysis method will be described below. Since the developing solvent varies depending on the type of the fatty acid of the polyglycerin fatty acid ester and the number of moles of glycidol added, it is preferable to determine the developing solvent from the solubility and separation properties of the test sample. Specifically, as a specific developing solvent having excellent solubility and separability of an analyte, an alcohol-based solvent and / or distilled water is preferable. Specifically, methanol is used for polyglycerol laurate. It is preferable to use ethanol for the polyglycerol stearate.

The flow rate of the developing solvent is selected according to the pressure resistance of the column used and the degree of separation of the obtained chromatogram.
Usually, it is in the range of 0.05 to 1.0 ml / min, more preferably in the range of 0.1 to 0.8 ml / min. The column temperature is preferably in the range 30-60 ° C. The wavelength of the ultraviolet absorption detector is 210 nm.

For a sample to be subjected to HPLC, it is preferable to use a developing solution to be used as a solvent, and a concentration and an injection amount are selected so as to be excellent in solubility and separation of an analyte. Specifically, the sample concentration is preferably 1 to 50%, and the injection volume is preferably 0.1 to 20 μl.

The content is measured according to the following. In HPLC analysis using an ODS column, elution is generally performed in the order of polarity. Therefore, in the case of polyglycerins, unsubstituted polyglycerol having high polarity is eluted first, and then polyglycerin monofatty acid ester and polyglycerin difatty acid ester are detected. On the other hand, in the case of glycerin monofatty acid esters, polyglycerin monoester having high polarity is eluted first, and glycerin monoester is eluted last. Therefore, the standard products of polyglycerin and glycerin monofatty acid were analyzed by HPLC under the same conditions, the retention times of the standard products and the samples were compared and examined, and those eluted after the glycerin monoester was eluted were replaced with polyesters of diester or higher. And The content (%) of the polyglycerol monofatty acid ester was represented by the peak area ratio according to the following. From the analysis chart, the peak area of polyglycerin, the peak area of polyglycerin monofatty acid ester (referred to as “polyglycerin, but in the present invention, the glycerin portion includes from polyglycerin to monoglycerin), and the peak area of diester or more. The peak area of the substituted ester component was determined. Then, it was calculated according to the following equation.
In addition, the solvent whose peak position did not overlap with any of the peaks of polyglycerin, monofatty acid ester, and polysubstituted ester of diester or higher was selected. The following formula assumes that the retention time of the solvent is after the elution of the diester.

[0020]

## EQU1 ## Formula: Content (%) of polyglycerin monofatty acid ester
= ｛Peak area of polyglycerol monofatty acid ester /
(Peak area of polyglycerin + peak area of polyglycerin monofatty acid ester + peak area of polysubstituted ester of diester or more) エ ス テ ル × 100 (%)

The amount of the surface treatment agent for a metal can of the present invention used is:
It is preferable to apply an amount such that the static friction coefficient of the outer surface of the metal can becomes 1.5 or less. Specifically, for example, approximately 3 to 60 mg (as pure polyglycerin fatty acid ester) is used per 1 m ^{2 of the} outer surface of the metal can. In use, all conventionally known methods can be used. For example, it can be diluted with water or a water-soluble solvent (preferably water from the viewpoint of environmental hygiene), and applied, sprayed, or the like using a spray, a roller, or the like. In addition, the surface treatment agent for metal cans of the present invention can be used in any step before and after the production of metal cans, and can be used after production of metal cans before the filling step or printing step of metal cans. can do.

The surface treatment agent for metal cans of the present invention can be used together with other lubricants, stabilizers, antibacterial agents and the like, if desired.

The polyglycerin fatty acid ester used in the surface treatment agent for metal cans of the present invention is approved as a food additive and has high safety to the human body. Therefore, it can be safely used for metal cans for food. In addition, this metal can surface treatment agent reacts with the outer surface of metal cans, especially aluminum cans, by chemical or physical adsorption to form a thin organic film, and this film reduces the coefficient of static friction as a lubricant. Works. In addition, the surface treatment agent for metal cans of the present invention does not adversely affect the adhesion of paint or lacquer painted on the can.

[0024]

EXAMPLES The present invention will now be described specifically with reference to examples, but the present invention is not limited to these examples.

(Measurement Items) (1) Mobility The static friction coefficient of the outer surface of the can was measured using a laboratory static coefficient of friction tester HEIDON-14. (2) Paint Adhesion After the surface treatment, 4 to 6 cans that have been coated are used as a set, and the test solution A (1% Joy aqueous solution: Procter and)
Ganble's solution-type dishwashing detergent "Joy" dissolved in ion-exchanged water: tap water = 3: 1 to a concentration of 1%;
Test solution B (1% aqueous solution of Joy: P)
A solution-like dishwashing detergent "Joy" manufactured by Rocter and Gamble was dissolved in ion-exchanged water to a concentration of 1%; Next, a sharp metal object was used to draw a horizontal line on each can, allowing the aluminum lines to be visible through paint or lacquer. On top of this, a transparent tape (Scotch N manufactured by 3M)
o. 610) was firmly attached and then quickly pulled out. This test was performed on the outer side wall, inner side wall, and inner bottom of the can. The evaluation was as follows. 10: The paint is not peeled off from the can surface at all 8: There is no practical problem 0: The paint is completely peeled off with the tape width

[Synthesis Example 1] 0.5 mol of lauric acid (100.10) was placed in a 1-liter four-necked flask equipped with a nitrogen inlet 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. Then, continue to add 2% by weight of water to the same flask.
After the addition, the temperature inside the flask was heated to 140 ° C. with stirring, and the temperature was maintained at this temperature under reflux for 2 hours. Next, the temperature inside the flask was raised to 140 ° C., and while maintaining this temperature, the inside of the flask was depressurized and dehydrated by vacuum distillation. 4 vacuum distillations
The final degree of decompression after 10 hours was 10 mmHg.
When the obtained polyglycerin fatty acid ester (hexaglycerin monolaurate) was evaluated using the following HPLC analysis conditions, the monoester content was 8%.
7.7%.

(HPLC analysis conditions) Column: Wakosil II 5C18HG (manufactured by Wako Pure Chemical Industries, Ltd .: column having an octadecylsilyl group as a functional group which is a reversed-phase distribution column, size: 4.6 mm)
φ × 250 mm), developing solvent: methanol, flow rate: 0.
2 ml / min. , Column oven temperature: 40 ° C., detection method: ultraviolet absorption method (λ = 210 nm), sample concentration: 5
% (Solvent: methanol), injection volume: 10 μl, retention time of each component: polyglycerin: before 14 minutes, monoester: from 14 minutes to 16.5 minutes, diester and above: from 16.5 minutes, methanol component : 18 minutes.

[Synthesis Example 2] 4.0 mol of glycidol
(296.32 g) Except for using, the same operation as in Synthesis Example 1 was performed. After cooling, the reaction product was taken out to obtain about 400 g of octaglycerin monolaurate. The obtained polyglycerol monolaurate (octaglycerol monolaurate) was converted to H
When evaluated by PLC, the content of monoester was 8
It was 4.5%.

Synthesis Example 3 5.0 mol of glycidol
(370.40 g) Except for using, the same operation as in Synthesis Example 1 was performed. After cooling, the reaction product was taken out to obtain about 470 g of decaglycerin monolaurate. The obtained polyglycerol monolaurate (decaglycerin monolaurate) was converted to HPL in the same manner as in Synthesis Example 1.
When evaluated in C, the monoester content was 77.2.
%Met.

Reference Example 1: Reaction of Fatty Acid with Polyglycerin Polyglycerin (Daicel Chemical Industries, Ltd.) was placed in a 1-liter four-necked flask equipped with a nitrogen inlet tube, a stirrer, a cooling tube, a temperature controller, and a dropping cylinder. PGL manufactured by
06: hexaglycerin, hydroxyl value 960) 175.3
g (0.5 mol) and heated to 80 ° C., 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 mgKOH / g. After cooling to 100 ° C., the reaction product was taken out. The obtained polyglycerol monolaurate was converted to H in the same manner as in Synthesis Example 1.
When evaluated by PLC, the monoester content was 5%.
It was 5.1%.

Reference Examples 2 and 3: Evaluation Results of Commercially Available Polyglycerol Fatty Acid Esters As commercial polyglycerin fatty acid esters produced from the reaction of polyglycerin and fatty acids, two products of SY Glister (manufactured by Sakamoto Yakuhin Kogyo) ML-500, ML-750). When these polyglycerin monolaurates were evaluated by HPLC in the same manner as in Synthesis Example 1, ML-500, M
The content of the monoester of L-750 was 52.0
%, 44.3%. These are referred to as Reference Examples 2 and 3, respectively.

(Examples 1 to 8 and Comparative Example 1) The mobility and paint adhesion due to the difference in the concentration of the metal can surface treating agent were evaluated as follows. Clean the unwashed aluminum can with an acidic cleaner (Surf Cleaner NHC-Nippon Paint Co., Ltd.).
100; pH 1) for 60 seconds at 75 ° C.
For cleaning, a laboratory mini washer (a processing capacity of 14 cans) was used. At the last rinsing step of the washing, the polyglycerin fatty acid ester obtained in Synthesis Example 1 was treated in a metal can with a metal treatment agent adjusted to the concentration shown in Table 1, and then dried in an oven. After the treatment, the mobility of the can in the can production line and the paint adhesion after painting were evaluated.

[0033]

[Table 1]

(Examples 9 to 11, Comparative Examples 2 to 4) The mobility according to the type of metal can surface treatment agent and the paint adhesion after printing were evaluated. Use an aluminum can with an acidic cleaner (Surf Cleaner 124C manufactured by Nippon Paint Co., Ltd .; pH
Using 1.1), washing was performed at 50 ° C. for 60 seconds. Then
0.5 g of the components shown in Table 2 were dissolved in 1 liter of water to prepare surface treatment liquids for metal cans, and the surfaces of aluminum cans were treated with the surface treatment liquids for metal cans. The mobility of the treated can was evaluated. The cans after printing were cut open, boiled in Test Solution A (see Paint Adhesion Test) for 10 minutes, then rinsed in deionized water and dried. The paint adhesion was then evaluated.

[0035]

[Table 2]

[0036]

[Table 3]

(Results) As can be seen from Table 1, the cans subjected to the surface treatment exhibited a reduced coefficient of static friction on the outer surface of the can and improved mobility. The paint adhesion was not affected. A sufficient effect can be obtained even at a low concentration,
After 100 tests, paint adhesion was not affected. In Examples 3 and 8, the paint on the outer side wall was hardly peeled off. Also, from Table 3, the content of the monofatty acid ester was 77.2 to 87.7.
% When the polyglycerol fatty acid ester containing the polyglycerol monofatty acid ester was used as a metal can surface treatment agent, it was found that the mobility and the paint adhesion after printing were excellent. Generally, it is desirable that there be no water break on the can surface, that is, that the can surface be covered with a continuous thin film of water. This is because a water break has large water droplets, and the water film on the surface of the can becomes uneven and discontinuous. The surfaces of the cans treated with the solutions of Examples 9 to 11 and Comparative Examples 2 to 4 were completely covered with a water break, which was considered to affect printing. It was good.

[0038]

According to the surface treating agent for metal cans of the present invention, the coefficient of static friction of the outer surface of the can is reduced, so that the mobility of the can is improved and the productivity of the production of metal cans can be increased. Furthermore, the metal can surface treating agent does not adversely affect the adhesion of paint and lacquer during printing. In addition, the surface treatment agent for metal cans of the present invention is approved as a food additive, and has high safety to the human body even when used for processing metal cans for food.

Claims (4)

[Claims] 1. The peak area of a polyglycerol monofatty acid ester represented by the following general formula (1), which is eluted by column chromatography and detected using an ultraviolet absorption detector, is 70% or more of the entire area. A surface treating agent for metal cans, comprising a polyglycerin fatty acid ester characterized by the following. Embedded image 2. The method according to claim 1, wherein the column chromatography is a high performance liquid chromatography using an octadecylsilyl group-bonded silica gel column using an alcohol solvent and / or distilled water as an eluent. Surface treatment agent. 3. A polyglycerol monofatty acid ester,
The surface treating agent for metal cans according to claim 1 or 2, which is obtained by reacting a fatty acid represented by the following general formula (2) with glycidol in the presence of a phosphoric acid-based catalyst. Embedded image 4. The surface treating agent for a metal can according to claim 3, wherein the phosphoric acid-based acidic catalyst is phosphoric acid or an acidic phosphoric acid ester.