KR800001613B1 - Paint composition for inner tube - Google Patents

Abstract

Polar group-contg. polyolefins ard dispersed in hydrocarbon solvents having b.p. higher than the softening temp. of the polyolefin and other solvents to give coating material for inside surface of cans. Thus 10 parts CMP L900X(grafted PE) and 40 parts xylene were heated to 850C, and the soln. was added. to 50 parts cold xylene and dild. with 50 parts iso-prOH to give a stable coating material. An Al can was spray-coated with the above coating soln. with 70g/m2 and baked 5 min at 180oC. When iso-prOH was omitted a similar dispersion in xylene agglomerated and clogged. the spray gun after 7 days of storage.

Description

Inner Paint Composition

The accompanying drawings are cross-sectional views of the apparatus provided for the energization test.

The present invention relates to an inner surface coating composition in which a polar group-containing polyolefin is dispersed in a solid granular state in a hydrocarbon solvent alone or in a mixed solvent of a hydrocarbon solvent and a non-hydrocarbon solvent.

Conventionally, epoxy phenol type, epoxy urea type, or vinyl chloride type paints have been used as inner coatings for steel pipes. However, these paints may cause problems in terms of hygiene, especially when used for inner tube paints for canning, especially when used in food pipes. Therefore, it is worth considering that the polyolefin, which is not concerned with hygiene, is coated on the inner surface of the pipe by the powder coating method.

However, this method makes it difficult for powder to adhere to the corners of the tube, so that the coating film of the portion is thinned, so that the contents protection function cannot be sufficiently achieved, and the powder coating method is applied to a metal tube treated with ordinary undercoat. There is a major flaw that it cannot.

In addition, the powder coating method forms a resin coating film with a thickness larger than necessary, which is not a preferable method for saving resources. Moreover, since conventional coating equipment for inner coating of pipes cannot be used, a large-scale investment in new equipment is required. It is very disadvantageous industrially in the present state.

There is also a so-called hot melt method in which a polyolefin is melted and coated, and a coating film is formed even when it is solidified by cooling. However, even in this method, the problem that the coating film becomes very thick is not solved. In addition, since the polyolefin does not adhere to the metal surface and the epoxy base, and also has a high melting point, an ethylene vinyl acetate copolymer (abbreviation EVA) is usually added. Use it.

As the amount of EVA increases, the adhesiveness is improved, but there is a problem that the taste of the contents becomes poor due to impurities eluted from the coating film, which has not been put to practical use.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, wherein the polar inner-containing polyolefin is dispersed in a solid granular state in a solvent alone or in a mixed solvent of a hydrocarbon solvent and a non-hydrocarbon solvent, in the form of a tube inner coating composition. To provide.

The polar group-containing polyolefin in the present invention is a polyunsaturated unsaturated monomer containing a polar group such as a hydroxyl group, an epoxy group, or a carboxylic acid group in polyethylene or polypropylene, for example, 2 hydroxyethyl (meth) acrylate and 2 hydroxy. Graft polymerization of propyl (meth) acrylate, glycidyl (meth) acrylate, (meth) acrylic acid, maleic anhydride and the like is used.

Graft is a method known per se, in which a polyolefin interpolymer is subjected to strong mechanical mixing such as a kneader or a Banbury mixer in the coexistence of the polymerizable unsaturated monomer, a radical is generated by kneading, and the graft polymerization is performed at the active site thereof. The so-called mechanical chemistry or the radiation graft polymerization method to carry out graft polymerization by radioactive irradiation is mentioned.

Commercially available products are Zaikthen-F (trade name) of Seidetsu Kagugokyo Kabushi Kaisha, and Too Nenyo Kogyo Kabushi Kaisha. CMPC-902X-MA, C-802X-MA, and L-900X (trade name) of KKK.

Among these polar group-containing polyolefins, a carboxyl group-containing unsaturated monomer such as maleic acid, maleic anhydride, fumaric acid, acrylic acid, methacrylic acid, or the like is 0.01 to 6.0 wt%, preferably 0.05 to 1.5 wt% graft polymerized in a graft ratio. And stability of the dispersion is good.

These polar group-containing polyolefins also exhibit excellent performance in terms of adhesion to treated or untreated metal and undercoat surfaces. In addition, these polar group-containing polyolefins have an average molecular weight of about 1,000 or more and are selected from those having a softening point in the range of about 100 ° C to 180 ° C in order to maintain boiling resistance during sterilization. Good to do.

As a solvent used for this invention, a hydrocarbon solvent is made into one of essential components. Only solvents of ester, ketone or ether solvents, not hydrocarbons, are observed to whiten due to precipitation of the resin immediately after coating or before softening of the resin particles in the initial stage of baking. When baked with such whitening phenomenon, it cannot form uniform and smooth coating film.

In the practice of the present invention, in the case of a hydrocarbon solvent alone as the solvent, the boiling point is preferably selected from the range of not more than the softening point of the polar group-containing polyolefin to be used and not higher than 50 ° C. above the baking temperature after coating.

Even in the case of using a hydrocarbon solvent having a softening point of less than or equal to the polar group-containing polyolefin, the above-described whitening phenomenon is observed, and a good coating film cannot be formed. Moreover, when using the hydrocarbon solvent which has a boiling point of 50 degreeC or more than the temperature at the time of baking, there exists a possibility that a solvent may remain in a formation coating film, and it is not good.

Specifically, aromatic hydrocarbons such as toluene, xylene, aliphatic hydrocarbons such as isooctane, nonane, decane, alicyclic hydrocarbons such as methylcyclohexane, ethylcyclohexane, decahydronaphthalin, or solvent naphtha Or a mixture of two or more kinds thereof.

However, in the coating composition using a hydrocarbon solvent having a boiling point equal to or higher than the softening point of the polar group-containing polyolefin as described above, depending on the type of the polar group-containing polyolefin, the suspended solids are excessively swollen, resulting in a large particle size, which is then applied by spraying. When spraying, the spray port may be clogged, resulting in a difficult coating, and further improvement in terms of sagging and uniformity.

In such a case, a mixed solvent of one or two or more hydrocarbon solvents having a boiling point at a temperature higher than or equal to the softening point of the polar group-containing polyolefin and one or two or more organic solvents other than the hydrocarbon solvent may be used.

That is, the hydrocarbon solvent having a boiling point equal to or higher than the softening point of the polar group-containing polyolefin has been described above, and other solvents include hydrocarbon solvents having a boiling point below the softening point of the polar group-containing polybenlepin such as benzene, hexane and heptane, ethanol, Alcohol solvents such as methanol, propanol, isopropanol, butanol, octanol, cetyl alcohol, diacetone alcohol, ester solvents such as ethyl acetate, butyl acetate and cellosol acetate, petyl ethyl ketone, methyl isobutyl ketone, cyclohexane, Ketone solvents such as isopron, ether solvents such as ethyl ether, ethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, and halogenated hydrocarbon solvents such as carbon tetrachloride and trichloroethylene Etc., and one or two or more of these may be used. There.

The ratio of both solvents is about 5 / 95-95 / 5 (weight), Preferably it is about 30 / 70-70 / 30, and it selects suitably according to the kind of each solvent, the kind of polar group containing polyolefin, etc.

In the practice of the present invention, when a hydrocarbon solvent having a boiling point above the softening point of the polar group-containing polyolefin as described above is used, the following drawbacks may occur. That is, since the boiling point of a hydrocarbon solvent is relatively high, the odor resulting from a residual solvent will become a problem if it does not give sufficient temperature and time to bake.

In addition, it is not possible to shorten the baking time in this regard. In order to eliminate this drawback, if the paint composition using a hydrocarbon solvent having a low boiling point is dried immediately after application, the problem of residual solvent (film) is small.However, if dried after time, it can be visually identified. Pore formation may occur, but in this case, current flow is detected by the energization test described later.

In this case, there is a fear that heavy metal may be mixed into the contents of the tube from the pores. In order to solve these problems, a small amount of wax may be dispersed in the solvent together with the polar group-containing polyolefin.

As the wax, a softening point is selected from the range of about 50 to 120 ° C., preferably 70 to 120 ° C., but if a wax having a softening temperature that is too lower than the boiling point of water is used in a large amount, the whitening and air bubbles may be caused by boiling the coating film in water. It is not good to be concerned about it.

Examples thereof include waxes such as polyethylene wax, polypropylene wax, paraffin, and the like. The wax is melted immediately after coating or after volatilization of the solvent in the initial baking process to form a uniform and smooth coating film. There are no pores or pores, and the base metal is filled after filling the tube with contents. The problem of eluting is improved.

The ratio of the wax to the polar group-containing polyolefin is approximately 1/99 to 20/80 (weight), preferably about 3/97 to 10/90, depending on the type of wax and the type of the polar group-containing polyolefin. do. That is, when using a wax having a relatively low melting point, a small amount is used, and when using a wax having a relatively high melting point, an appropriate amount is determined.

In the present invention, as a method of dispersing the polar group-containing polyolefin in the solid state in the solvent, a polar group-containing polyolefin and (or) wax is dissolved in a solvent by heating and dropping it while stirring in a cold solvent to disperse or disperse A method of dispersing using a disperser such as an all-mill or sand grinder can be employed. Since the polar group-containing polyolefin is dispersed in the solvent in a solid state, it becomes relatively low in viscosity and high solid content, which is advantageous in terms of workability and solvent recovery.

It may be partially swollen and dissolved to such an extent that it is not against this purpose. Moreover, additives, such as a pigment and other fillers and a dispersibility improving agent, can also be added to the piping inner surface coating composition of this invention, as long as it does not conflict with the objective. The present invention will be described in detail by way of examples. In the examples, parts and percentages indicate parts by weight and% by weight.

Example 1

10 parts of graft polypropylene [MI24, maleic anhydride graft rate 0.2% by weight, C-0902X-MA, manufactured by Toanen Ryogyo Co., Ltd.] and Solvetso 150 (aromatic petroleum-based) 90 parts of a solvent, a cell chemical agent, and a brand name) were put under a bowl, and kneaded at room temperature for 6 hours to obtain a milky white dispersion exhibiting excellent aging stability and thixotropic property with an average particle diameter of 30 µ.

Example 2

10 parts of graft polyethylene (carboxyl group-containing unsaturated monomer graft ratio 0.3% by weight, MI10, L-900X, softening point about 105 ° C, manufactured by Tooannyo Kogyo Co., Ltd.) and 40 parts of ethylcyclohexane, heated to 85 ° C while stirring To completely dissolve the resin. This was dripped while stirring and cooling in 50 parts of the same solvent, and the milky dispersion which was excellent in aging stability with an average particle diameter of 15 micrometers was obtained.

[Examples 3-7, Comparative Examples 1-5]

In Example 2, a dispersion was obtained using a solvent as shown in Table 1 instead of ethylcyclohexane. The coating material of the dispersion obtained in Examples 2-7 and Comparative Examples 1-5 was uniformly treated by a roll coater at a rate of 80 g / m 2 (8 g / m 2 as a solid content) on a tin plate, and at 200 ° C., Bake for 5 minutes. The obtained state is also shown in Table 1.

TABLE 1

Example 8

The dispersion prepared in Example 1 was uniformly treated on a tin plate at a rate of 80 g / m 2 with a roid coater, and baked at 200 ° C. for 5 minutes. As a result of the resistance test of the obtained coating, the smoothness was good as seen from the eye, the adhesion was 100/100 by the normal Go eye test, and the bending resistance was bent in a double way by impacting the coating plate with the coating film outward. And the crack in the coating film at that time was observed but it was not seen at all. For the boiling resistance of the coating soaked in boiling water for 30 minutes and the retort resistance for 90 minutes in the steam at 130 ° C, the whitening of the coatings was observed and the above-mentioned Go eye test for adhesion. , The problem did not happen.

In addition, good results were obtained even when the epoxyphenol-based and epoxy urea-based undercoatings were coated on the tin plate treated by the conventional method and the chemically treated steel sheet in the same manner.

Example 9

50 parts of ethylcyclohexane was added to 10 parts of the dispersion prepared in Example 2 to form a paint. The inner surface of the formed aluminum tube was coated with an air sprayer at a rate of 110 g / m 2, and baked at 160 ° C. for 5 minutes. As a result of various resistance tests as in Example 8 with respect to this coating film, good results were obtained except for retort resistance.

The reason for the poor retort resistance is that the softening point of the resin used is low, and there is a sufficient effect for a beverage water pipe for which no retort resistance is required.

In addition, good results were obtained with the exception of retort resistance, even when the epoxy phenol-based and epoxy urea-based undercoatings were coated on the tin plate and the chemically treated steel sheets by the conventional method.

Example 10

10 parts of graft polyethylene (Tooen Ryogyo Co., Ltd. make, L-900X, softening point about 105 degreeC) and 40 parts of xylenes are heated to 85 degreeC, stirring, and it melt | dissolves completely. This was dripped at 50 parts of cold xylenes, stirring, and the milky white dispersion liquid with an average particle diameter of 15 micrometers was obtained. 50 parts of isopropanol were added to this, stirring, and the coating material was created. This paint is stable not only immediately after making, but also after aging for 3 months, and the spray hole is not blocked at the time of coating.

On the inner surface of the molded aluminum tube, the paint was treated with an air sprayer at a rate of 70 g / m 2, and baked at 180 ° C. for 5 minutes. The smoothness of this coating was satisfactory as a result of visual observation, and the adhesion, bending resistance, and boiling resistance were sufficiently endurable for practical use.

Example 11

2,400 parts of four-necked Frascoexylene and 600 parts of low density polyethylene [F-2270, M17, manufactured by Asahi Dow Co., Ltd., density 0.922, softening point approx. 110 ° C.] were put in 110 ° C. while stirring in a nitrogen gas atmosphere. After heating to completely dissolve polyethylene, 10 parts of maleic anhydride and 2 parts of benzoyl peroxide were added, and stirring was continued at the same temperature for 1 hour.

[Refining method]

After cooling, 7500 parts of 60 degreeC water was put into the said fresco, it heated up at about 80 degreeC (about 15 minutes), stirring, and stirring was continued at that temperature for 5 minutes. When stirring stops, it separates into two layers, the upper layer is a polar group containing polyethylene-containing xylene solution, and the lower layer is water. The amount of unreacted maleic acid contained in the water of the lower layer was 5 parts as a result of the acid value measurement.

By repeating the following operation, the amount of maleic acid contained in the water was 3.1 parts in the second, 0.6 parts in the third, 0.1 parts in the fourth, 0.1 parts in the fifth, and ND (not detected) in the sixth.

As a result, 0.1 part of maleic anhydride is graft-polymerized with respect to the said polyethylene, and the graft ratio is 0.17 weight.

In this way, 3,000 parts of xylene was further added to the polar group-containing polyethylene-containing xylene solution purified by hot water, and the water contained a little by heating was evaporated to obtain a stable dispersion. Using this dispersion, the aluminum tube was coated in the same manner as in Example 9, and similarly good results were obtained.

Example 12

The reaction temperature of Example 11 was 120 ° C for polypropylene (manufactured by Mitsui Seki Oil Co., Ltd., F-630, Density 0.91, MI value 9.0, Softening Point 140 ° C). A xylene dispersion of polypropylene having a graft ratio of 0.20% by weight was obtained in the same manner as in the above, and was tested in the same manner to obtain good results in retort resistance.

Examples 13 to 24

Instead of isopropanol in Example 12, using each solvent shown in Table 2, it was confirmed that the thing excellent in each performance of a coating film and a coating material was obtained.

TABLE 2

Example 25

10 parts of graft polyethylene (L-900X like Example 1), and 110 parts of toluene are heated to 85 degreeC, stirring, and it melt | dissolves completely. This was cooled to obtain a milky white dispersion having an average particle diameter of 15 µ. 30 parts of ethanol were added thereto with stirring to obtain a coating composition having good applicability and storage stability, which was uniformly treated on a tin plate at a rate of 100 g / m 2, and baked at 160 ° C. for 5 minutes. The smoothness and resistance of this coating film were enough to endure practical use.

Example 26

Place 10 parts of graft polypropylene (C-902X-MA, manufactured by Doannene Ryogyo Kogyo Co., Ltd.) and 80 parts of Solvetso 150 (aromatic, petroleum solvents, and cell chemicals) in a bowl mill at room temperature. It knead | mixed for time and obtained the milky dispersion which is about 30 micrometers in average particle diameter. 10 parts of diethylene glycol monomethyl ethers were added to this, with stirring, to obtain a coating composition having good applicability and storage stability, and uniformly treated at a rate of 80 g / m 2 on the tin plate with a rool coater at 200 ° C. for 5 minutes. Baked.

This coating material was also excellent in the retort resistance left to stand in steam at 130 degreeC for 90 minutes.

Example 27

9.5 parts of graft polyethylene (Tooen Ryogyo Kogyo Co., Ltd., L-900X, softening point 105 ° C) and microcrystalline wax (Japan Stone Micro Wax 155, Nippon Seki Oil Co., Ltd.) made by Nippon Seki Oil Co., Ltd. , Melting point 70 ° C.] 0.5 part and 40 parts of methylcyclohexane are heated to 85 ° C. while stirring to dissolve completely. This was dripped in 50 parts of cold methylcyclohexanes, stirring, and the milky white dispersion of 15 micrometers of average particle diameters was obtained.

50 parts of isopropanol were added to this, stirring, and the coating material was created. This paint is stable not only immediately after it is made but also after three months have elapsed, and the spray hole is not blocked at the time of coating. The paint was treated on a tin plate with a spraying sphere at a rate of 70 g 2, and baked at 160 ° C. for 5 minutes.

This coating is smooth, and the current flow is not detected by the following method, and it is proved that there is no hole or pore. In addition, even in the boiling test, no whitening or blister was generated, and it was able to withstand practical use. In addition, the baked coating had no smell.

The accompanying drawings are sectional views of the apparatus provided for the energization test. A container 4 in which the saline solution 3 is placed on the coated film 2 treated on the metal plate 1 is installed, and the current is detected by the ammeter 5. It is.

Comparative Example 6

In Example 26, when 0.5 part of wax was added and the same coating film was formed and an electric current test was carried out, an electric current flowed and the presence of a hole and a pore was detected.

Example 28

10 parts of graft polyethylene (Tooen Ryogyo Co., Ltd., L-900X, softening point 105 ° C.) and 40 parts of Solvetso 150 (aromatic, petroleum solvent, and cell chemistry) at 85 ° C. with stirring Heat and dissolve completely. This was dripped under stirring in 50 parts of xylene to obtain a milky white dispersion having an average particle diameter of 50 µ.

50 parts of isopropanol were added to this, stirring, and the coating material was produced. The paint on the tin plate was treated with an air sprayer at a rate of 70 g / m 2 and baked at 180 ° C. for 5 minutes. When a current-carrying test was conducted to this coating film, no current flowed and no holes or pores were detected.

[Examples 29-33]

It confirmed that the thing excellent in each performance of a coating film and a coating material was obtained using each wax shown in Table 3 instead of the wax in Example 27.

TABLE 3

Example 34

9.5 parts of graft polypropylene (manufactured by Tonanen Ryogyo Co., Ltd., C-902X-MA, softening point 160 ° C) and polyethylene wax (manufactured by Mitsui Seki Oil Co., Ltd.), Hiwax 410, softening temperature 122 0.5 part and 40 parts of xylene are heated to 85 ° C. while stirring, and are completely dissolved. This was dripped with stirring in 50 parts of toluene, and the milky white dispersion of 15 micrometers of average particle diameters was obtained.

To this 50 parts of isopropanol were added with stirring to make a paint. The paint was treated on a tin plate with an air sprayer at a rate of 70 g / m 2, and baked at 200 ° C. for 5 minutes. There was no smell of residual solvent.

When the obtained coating film was subjected to an energization test, there was no current flow, and no holes or pores were detected. This coating material is left for 90 minutes in steam at 130 ° C. It was superior in retort resistance.

Claims (1)

A polar group-containing polyolefin made of polyethylene or polypropylene having a hydroxyl, epoxy or carboxyl group, and at least one hydrocarbon solvent having a boiling point at or above the softening point of the polyolefin and not higher than 50 ° C. above the baking temperature of the paint composition; And dispersed in a solid granular state in the mixed solvent for polyolefin with at least one organic solvent other than the hydrocarbon solvent, and the polar group-containing polyolefin and wax are at least one hydrocarbon solvent and at least one solvent. An inner surface coating composition which is dispersed in a solid granular state in a mixed solvent for a polyolefin and a wax with a non-hydrocarbon solvent.

Images