JP3638312B2 - Phosphate-modified epoxy resin composition and water-based coating composition using the same - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a novel phosphoric acid-modified epoxy resin composition and a coating composition using the same, and in particular, has water resistance that can withstand the heat treatment step of beverage cans and food can sterilization treatment, particularly retort treatment. A water-based coating composition that is less likely to be damaged during the transportation of the can, can be formed into various can forms, has excellent processability, and has a low organic solvent content, and a phosphoric acid-modified epoxy resin composition used therefor About.
[0002]
[Prior art]
The outer surface of beverage cans containing soft drinks and food cans for packaging foods is coated with a solvent-based can coating material to prevent corrosion of the can material and increase the aesthetic product value. Conventionally, as these paints, an organic solvent solution such as epoxy / amino resin, acrylic / amino resin, polyester / amino resin or the like is applied with a roll coater and baked and cured in a gas oven. . However, since these paints cause a large amount of solvent volatilization during baking and cause air pollution, water-based systems with a low content of organic solvents are progressing from the viewpoint of resource and low pollution. There are two types of water-based paints, water-dispersible and water-soluble, and many water-dispersible paint resins used for water-dispersible paints are usually synthesized by emulsion polymerization using a surfactant. The water-soluble coating resin contains about 10% by weight of an organic solvent in order to improve the storage stability of the coating composition and the leveling in forming the coating film.
[0003]
[Problems to be solved by the invention]
In the case of a water-dispersible coating resin, the surfactant to be used remains in the coating film even after the coating film is formed. There is also a method of synthesizing a resin containing an acidic group such as a carboxyl group in an organic solvent system without using a surfactant, and neutralizing with a volatile base to form a dispersion. In the resin structure to be obtained, an acid group having an acid value of 20 or more is required, and there is a disadvantage that performances such as water resistance and alkali resistance are inferior. In order to improve these disadvantages, there is a method of mixing a large amount of aqueous amino resin such as hexamethoxymethylmelamine and methylated benzoguanamine, but the processability is greatly reduced. On the other hand, if the aqueous amino resin is reduced in order to improve the workability, the coating film hardness tends to decrease, and it becomes difficult to balance water resistance, coating film hardness, and processability. In addition, in the method of mixing phosphoric acid as another method, since the compatibility with the acrylic resin is poor, there is a problem in the storage stability of the paint and the leveling in the coating film formation. It appears especially prominently.
[0004]
On the other hand, conventional water-soluble paints contain about 10% by weight of an organic solvent for improving the storage stability of paints and leveling in the formation of coating films. Is not enough. Furthermore, conventional water-soluble paints have been obtained with no abnormality even when subjected to treatment with boiling water as water resistance, but when subjected to treatment with pressurized boiling water at 120 ° C. or higher, the coating film blisters. It cannot wake up, dissolve or whiten to maintain aesthetic value. Therefore, development of a water-based paint resin and a water-based paint composition using the same are desired.
[0005]
[Means for Solving the Problems]
The present inventors have found that a resin composition containing a phosphoric acid modified product in which ε-caprolactone is added to a specific hydroxyl group of a specific bis-phenol diglycidyl ether type epoxy group can solve such a problem. It came to complete.
[0006]
That is, the present invention is obtained by reacting a phosphoric acid compound of the following general formula (2) in the range of 1 to 2 moles of phosphorus with respect to 1 mol of an epoxy group of the epoxy compound of the following general formula (1). The phosphoric acid-modified epoxy resin composition is provided.
[0007]
[Chemical 3]
[Formula 4]
[0008]
Furthermore, 20-80 weight% of aqueous | water-based acrylic resins, 20-50 weight% of aqueous | water-based amino resins, 5-30 weight% of the phosphoric acid modification epoxy resin composition of Claim 1 (the total of the three contains 100 weight%). A water-based coating composition is provided.
[0009]
The phosphoric acid-modified epoxy resin composition of the present invention is a modified product in which phosphoric acid is added to the epoxy group of an epoxy resin obtained by ring-opening addition of ε-caprolactone to a secondary hydroxyl group of a bisphenol diglycidyl ether type epoxy resin. JP-A-61-47771 uses Epicoat 828 and orthophosphoric acid manufactured by Shell Chemical Co., Ltd. as bisphenol diglycidyl ether, and ε is added to the secondary hydroxyl group of the bis-phenol diglycidyl ether type epoxy resin . -Nothing is disclosed about phosphoric acid-modified products in which caprolactone is subjected to ring-opening addition.
As the bisphenol diglycidyl ether type epoxy resin represented by the general formula (1) obtained by ring-opening addition of ε-caprolactone, n in the formula is 1 or more, preferably 1 to 20, and m is 1 to 1 100, preferably in the range of 1-20. These can improve compatibility with an acrylic resin, a polyester resin, or the like. This is presumably because polycaprolactone is introduced into the side chain of the bisphenol skeleton, and these have the property of being easily compatible with acrylic resins and polyester resins. Moreover, by introducing polycaprolactone into the secondary hydroxyl group of the bisphenol diglycidyl ether type epoxy resin , it can be converted to the primary hydroxyl group and the reactivity with the melamine resin or the like can be improved. In addition, other lactones such as trimethylcaprolactone and valerolactone may be used together with ε-caprolactone as long as the effects of the present invention are not inhibited.
[0010]
As the epoxy resin, bisphenol diglycidyl ether type epoxy resin, for example, Araldide 6071, Araldide 6084, Araldide 6097, etc. manufactured by Ciba Geigy Corporation can be used. In these, n in the formula corresponding to the general formula (1) is in the range of about 2 to 10.
[0011]
Examples of the phosphoric acid compound represented by the general formula (2) used in the present invention include orthophosphoric acid and a monoester of orthophosphoric acid, and the latter includes, for example, monobutyl phosphate and monoamyl phosphate in which R ′ is an alkyl group. Monononyl phosphate such as monophenyl phosphate where R ′ is an aryl group, monobenzyl phosphate where R ′ is an alkyl group-substituted aryl group, monocyclohexyl phosphate where R ′ is a cycloalkyl group, R ′ is complex A cyclic group such as monopyridine phosphate can be used. The mixing ratio of the phosphoric acid compound and the epoxy compound can be selected at an arbitrary ratio, but the number of moles of phosphorus of the phosphoric acid compound per mole of epoxy group is about 1 to about 2. If it exists in this range, the produced | generated phosphoric acid modified epoxy resin composition is stable, and control of reaction is not difficult.
[0012]
The reaction temperature is preferably in the range of about 25 ° C to about 150 ° C, particularly preferably in the range of about 50 ° C to about 100 ° C. If the reaction temperature is less than 25 ° C, the reaction is slow, and if it exceeds 150 ° C, it is difficult to control the reaction. This reaction is usually performed in the presence of an inert solvent. Solvents used include aromatic solvents such as benzene, toluene and xylene, ketone solvents such as methyl ethyl ketone, cyclohexanone, methyl isobutyl ketone and isophorone, hydrocarbon solvents such as hexane, heptane and cyclohexane, diethyl ether, tetrahydrofuran and dioxane. And ether solvents such as propylene glycol monopropyl ether, ester solvents such as ethyl acetate, isopropyl acetate and butyl diglycol acetate, and solvents such as halogen solvents. The amount of these solvents used is 0.1 to 20 times, preferably 0.5 to 2 times that of the epoxy resin. If the amount used is less than 0.1 times, the substrate concentration is high and it becomes difficult to control the reaction. On the other hand, if it exceeds 20 times, it is uneconomical to use for paints, which is not preferable. Although there is no restriction | limiting in the preparation order at the time of performing reaction, Preferably, an epoxy compound is dripped at a phosphoric acid compound, and it heats up to the said temperature. The end point of the reaction can be confirmed, for example, by quantifying oxirane oxygen by titration.
[0013]
The phosphoric acid-modified epoxy resin composition obtained by the reaction can be used as it is for a water-based coating composition or the like. It can also be isolated by washing with water and distilling off low-boiling components under reduced pressure, or distilling off low-boiling components as they are. Furthermore, in order to obtain a product having a high purity, recrystallization can be performed using a solvent insoluble at low temperatures.
[0014]
The water-based coating composition of the present invention comprises 20 to 80% by weight of an aqueous acrylic resin, 20 to 50% by weight of an aqueous amino resin, and 5 to 30% by weight of the phosphoric acid-modified epoxy resin composition based on the total resin solids as resin components. It is the water-based coating composition containing.
[0015]
Examples of the aqueous acrylic resin used in the present invention include α / β-monoethylenically unsaturated carboxylic acid monomers such as acrylic acid and fumaric acid, acrylic esters such as methyl acrylate and ethyl acrylate, and styrene such as styrene and vinyltoluene. A wide range of monomers can be used, such as those obtained by copolymerizing a suitable monomer such as a monomer based on hydroxy group, such as hydroxyethyl acrylate and hydroxypropyl acrylate. This aqueous acrylic resin is used in an amount of 20 to 80% by weight based on the resin solid content of the entire coating composition. If it is less than 20% by weight, the adhesion to the base material is lowered, the water dispersibility is inferior, the storage stability of the paint is also inferior, and the pigment dispersibility is also inferior when a pigment is added. On the other hand, if it is 80% by weight or more, the hardness is lowered and the water resistance is poor.
[0016]
The aqueous amino resin used in the present invention is an amino resin that can be dissolved or dispersed in an aqueous medium, such as a partially alkyl etherified melamine resin, a partially alkyl etherified benzoguanamine resin, or spiroguanamine alone or spiroguanamine and melamine or It is selected from spiroguanamine resins obtained by methylolizing a mixture with benzoguanamine and partially alkyl etherifying with an alcohol having 1 to 3 carbon atoms. In particular, spiroanamin resins are preferred in that the generation of tar-like low molecular weight substances generated during baking of the paint is less than that of melamine resins or benzoguanamine resins. The aqueous amino resin is used in an amount of 20 to 50% by weight based on the resin solid content of the entire coating composition. If it is less than 20% by weight, the hardness is not sufficient, and if it exceeds 50% by weight, the processability of the coating film decreases.
[0017]
The phosphoric acid-modified epoxy resin composition according to the present invention used in the water-based coating composition according to the present invention is used in an amount of 5 to 30% by weight in the resin solid content of the coating composition. If it is less than 5% by weight, the adhesion of the coating film is inferior, the water resistance is also inferior, and the processability is also inferior. If it is 30% by weight or more, the coating film tends to be too soft.
[0018]
In the water-based coating composition of the present invention, an acid catalyst blocked with an amine as a curing aid, for example, p-toluenesulfonic acid, dodecylbenzenesulfonic acid, dinonylnaphthalenedisulfonic acid, etc. is added to 100 parts of resin solid content as necessary. On the other hand, 0.1 to 2 parts can be added to form a paint. In addition, as a water-based coating resin, a commonly used water-soluble resin or water-dispersible resin such as a water-soluble polyester resin, maleated fatty acid, polyol, or the like can be mixed. Similarly, a leveling agent, an antifoaming agent, and a lubricant can be added. The pigment can be kneaded with the acrylic resin solution to prepare a pigment paste, which can be made into a paint by the same method as described above.
[0019]
The water-based coating composition of the present invention can be applied to a substrate by known means such as roll coating, spraying and brushing. As the base material, there are metal base materials such as an electric tin-plated steel plate, tin-free steel, and aluminum. Moreover, the water-based coating composition of the present invention can be cured under a wide range of baking conditions from baking at 150 to 200 ° C. for about 10 minutes to baking at 250 ° C. for about 10 seconds at high temperature. For this reason, it can sufficiently withstand the heat treatment process during food sterilization treatment.
[0020]
【Example】
EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.
[0021]
(Synthesis Example 1)
An epoxy equivalent of 608 is obtained by reacting 800 g of Araldide 6071 (manufactured by Ciba Geigy Co., Ltd.), 200 g of ε-caprolactone and 0.01 g of tetrabutyl titanate at 70 ° C. in a flask equipped with a nitrogen introduction tube, a thermometer, a cooling tube, and a stirrer. A lactone-modified epoxy resin having a hydroxyl value of 282.2 was obtained. Subsequently, 800 g of butyl cellosolve was added to obtain a uniform solution (referred to as epoxy solution A).
[0022]
(Synthesis Example 2)
A lactone-modified epoxy resin having an epoxy equivalent of 1443 and a hydroxyl value of 145.9 was obtained except that 700 g of Araldide 6084 (manufactured by Ciba-Geigy Corp.) and 300 g of ε-caprolactone were added. Similarly, 800 g of butyl cellosolve was added to obtain a uniform solution (referred to as epoxy solution B).
[0023]
(Example 1)
79.0 g of orthophosphoric acid was added to a four-necked flask equipped with a thermometer, a stirrer, a reflux condenser, a dropping funnel, and a nitrogen gas blowing tube. Next, 800 g of the epoxy solution A of Synthesis Example 1 was added to the dropping funnel. After the internal temperature was 80 ° C., the epoxy solution was dropped in 2 hours. After completion of the reaction, the oxirane oxygen concentration was measured and found to be 0 ppm. A part of the obtained solution (referred to as phosphoric acid-modified epoxy resin composition solution C) was distilled off a low boiling component for 2 hours at 100 ° C. and 2 to 5 mmHg by a rotary evaporator. Was measured an infrared spectrum of the reaction product, observed absorption derived from 1014 cm ^-1 to P-0, peak considered to be derived from the epoxy 780-820Cm ^-1 disappeared. Moreover, in ¹ H-mmr, the proton on the epoxy is shifted from δ (ppm) 3.0 to 3.4 to a low magnetic field of δ (ppm) 3.3 to 3.6, and the epoxy is ring-opened. I found out that
[0024]
(Example 2)
The same procedure as in Example 1 was performed except that 800 g of the epoxy solution B synthesized in Synthesis Example 2 and 33.2 g of orthophosphoric acid were used. The oxirane oxygen concentration of the solution (referred to as phosphoric acid-modified epoxy resin composition solution D) obtained after the reaction was 0 ppm.
[0025]
(Synthesis Example 3)
A four-necked flask equipped with a thermometer, stirrer, reflux condenser, dropping funnel and nitrogen gas suction tube was charged with 1000 g of bisphenol diglycidyl ether type epoxy resin araldide (Ciba Geigy) and 804 g of butyl cellosolve and melted at 80 ° C. Then, 706 g of orthophosphoric acid was added and reacted for 4 hours. The oxygen concentration of the oxirane in this solution (phosphoric acid-modified epoxy resin composition solution E) was 0 ppm.
[0026]
(Synthesis Example 4)
The same procedure as in Synthesis Example 3 was performed except that 1000 g of Araldide 6084 (Ciba Geigy Co., Ltd.) and 103 g of orthophosphoric acid were added to the epoxy resin. The oxirane oxygen concentration of this solution (phosphoric acid-modified epoxy resin composition solution F) was 0 ppm.
[0027]
(Synthesis Example 5)
A four-necked flask equipped with a thermometer, stirrer, reflux condenser, dropping funnel, and nitrogen gas suction tube was charged with 100 parts of n-butanol, and the temperature was maintained at 105 ° C. while stirring while introducing nitrogen gas. A solution of 5 parts of benzoyl peroxide in 100 parts of a mixture of 30% styrene, 30% ethyl acrylate, 10% butyl acrylate, 10% 2-hydroxyethyl acrylate, 10% methyl methacrylate and 10% acrylic acid over 3 hours. It was dripped. Thereafter, the reaction was continued at 105 ° C. for 1 hour, 0.5 part of benzoyl peroxide was added, and the reaction was further completed for 1 hour. Then, n-butanol was distilled off at 80 ° C. under reduced pressure until the nonvolatile content became 83%, then 14.6 parts of diethanolamine and water were added, and the solution was transparent and viscous with a solid content of 50% and a residual n-butanol of 10%. An aqueous acrylic resin (referred to as an aqueous acrylic resin solution G) was obtained.
[0028]
(Examples 3 and 4, Comparative Examples 1 and 2)
After mixing each component according to the ratio of the solid content of each component shown in Table 1, butyl cellosolve and water were added to adjust the amount of organic solvent in the paint to 10% and solid content of 35%. To this was added 0.3% of p-toluenesulfonic acid amine salt and 0.3% of a silicone leveling agent to obtain a water-based coating composition. This paint was applied on a TFS plate (chromed steel plate) with a natural roll coater and baked and cured at 190 ° C. for 10 minutes. The film thickness was 6-8 μm.
[0029]
[Table 1]
[0030]
(result)
The results of examining the stability and the physical properties of the coating materials prepared in Examples and Comparative Examples are shown in Table 2.
[0031]
[Table 2]
[0032]
Each test method is as follows.
(Paint test)
Paint stability test: After the paint was stored at room temperature for 2 months, the increase in viscosity due to gelation and separation of the resin in the paint was examined. Those having no increase in viscosity were evaluated as “good”, those having an increase in viscosity as “poor”, and those having no increase in viscosity and no change in appearance as “pass”.
(Film properties test)
The electroplating tin plate having a plate pressure of 0.23 mm was coated by roll coating so as to have a coating thickness of 7 μm after drying, and a baked coating panel was produced in a gas oven at an atmospheric temperature of 190 ° C. for 10 minutes. Scratchability was evaluated by creating a three-piece can in which a coated plate was molded such that the painted surface was the outer surface of the can.
Water resistance test: The coated panel was immersed in water and subjected to heat treatment at 100 ° C. for 30 minutes, and then the whitening state of the coating film was evaluated.
Workability test: Eriksen test; according to JISZ-2247, after extruding until the base metal plate began to crack, the state of the coating film was evaluated. A indicates that there are no cracks or scratches, A indicates that there are no cracks, and X indicates that a crack has occurred.
Impact resistance: Using a DuPont impact tester, a ½ inch diameter striker is brought into contact with the sample, and then a 500 g weight is dropped. Impact resistance was evaluated based on the height at which no cracks occurred in the coating film.
Pencil hardness test: It was performed according to a method registered in JIS standard “Pencil scratch test” (JIS No. K5400).
Adhesion test: Coban eye peel test was performed.
Scratchability: The contents were packed into a can, and the outer surface of the can was contacted in warm water at 80 ° C. to evaluate the degree of scratching of the coating film.
(Paintability test)
Flow: Immediately after painting with a roll coater, baking was performed in a gas oven, and the leveling state was evaluated. The coating film after baking was visually expressed as “good”, and the coating film after baking was not smooth as “poor”.
[0033]
【The invention's effect】
The phosphoric acid-modified epoxy resin composition of the present invention is excellent in flexibility and compatibility with acrylic resins and the like. The water-based coating composition using the phosphoric acid-modified epoxy resin composition according to the present invention exhibits excellent effects such as water resistance, retort resistance, workability, and impact resistance of the coating film.

Claims (2)

A phosphoric acid-modified epoxy resin obtained by reacting a phosphoric acid compound of the following general formula (2) in the range of 1 to 2 moles of phosphorus with respect to 1 mol of an epoxy group of the epoxy compound of the following general formula (1) Composition.
  It contains 20 to 80% by weight of an aqueous acrylic resin, 20 to 50% by weight of an aqueous amino resin, and 5 to 30% by weight of the phosphoric acid-modified epoxy resin composition according to claim 1 (the total of the three is 100% by weight). A water-based paint composition.