JPH0558469B2 - - Google Patents

Description

[Detailed description of the invention]

[Objective of the Invention] (Industrial Application Field) The present invention relates to a water-based adhesive can primer, and more specifically, it is applied to a can material, and in the side seam part, the primer coat is applied to a polyamide adhesive and to the can material. The invention relates to water-based primers that can be utilized to function as primers. (Prior Art) A so-called adhesive can is a general term for three-piece cans whose can bodies are seamed by adhesive. The reason behind the increasing importance of adhesive cans in metal containers in recent years is that instead of the traditional tin-plated tin, we are using stain-free steel such as chrome-plated steel sheets and chromic acid-treated steel sheets, as well as nickel-plated steel sheets, aluminium-plated steel sheets, and aluminum. Various can materials such as boards have been developed and supplied. In other words, unlike tinplate, these materials cannot be soldered, so when making a three-piece can body, the side seams must be joined by welding or adhesive, unlike conventional methods. When forming side seams with adhesive, a primer is usually applied to the can material such as stain-free steel and baked, and then hot melt bonding is performed using a polyamide adhesive. Therefore, the properties required of the undercoat are strong adhesion to the can material and adhesive, and at the same time, it is also required to have various physical properties such as corrosion resistance and processability as a can inner surface coating. From this point of view, epoxy-phenol solvent-based paints have conventionally been used as primer coats for adhesive cans. However, in recent years, with the problem of air pollution caused by organic solvents and growing social interest in saving petroleum resources, it has become necessary to stop using organic solvents in the coating and container industries.
Alternatively, active efforts are being made to shift to paints that contain as little organic solvent as possible. In particular, primer coats for adhesive cans are paints that are used in large quantities in the manufacture of adhesive cans, and have a large effect on the performance of adhesive cans. As the production volume of adhesive cans increases, the amount used also increases, which is why water-based cans are strongly desired. Up to now, epoxy resin-based water-based paints have been mainly studied as water-based can paints, and various methods have been proposed for dispersing epoxy resins in water. For example, methods using anionic and nonionic surfactants are known as methods for dispersing epoxy resins using surfactants, but they are inferior in storage stability, hygiene, chemical and mechanical performance. It is unsuitable as a paint for cans. As a solution to this problem, various self-emulsifying epoxy resins have been proposed in which epoxy resins are modified with acrylic resins and segments with emulsifying power are introduced into the molecules. Since such a self-emulsifying epoxy resin does not contain a surfactant in the coating film, a strong coating film itself can be obtained. Additionally, water-soluble amino resins and phenolic resins are added to these paints when a faster curing speed is required. However, when such prior art is used as an undercoat for adhesive cans, sufficient adhesion to the base can material and polyamide adhesive could not be obtained. (Problems to be Solved by the Invention) As a result of intensive studies in view of the above-mentioned circumstances, the present researchers have found that the performance of conventional epoxy-phenol solvent-based undercoating, that is, the performance of the base material and polyamide adhesive By maintaining strong adhesive strength, we have guaranteed the sealability of the can body, and succeeded in reducing or virtually eliminating organic solvents without impairing the function of the base material as a protective layer from the contents. It is something. [Structure of the Invention] (Means for Solving the Problems) That is, the present invention provides the following (a), (b), or (c) for 100 parts by weight of bisphenol type epoxy resin.
At least one resol resin selected from 10~
After precondensing 60 parts of the precondensate, a potentially self-emulsifying composite resin composition obtained by reacting the precondensate with a carboxyl group-containing acrylic resin in the presence of an esterification catalyst is prepared using amine or ammonia. The present invention relates to an aqueous adhesive can primer which is at least partially neutralized and dispersed in an aqueous catalyst. (a) A resol resin having a weight average molecular weight of 800 or more and less than 3,000, which is obtained by reacting a mixed phenol of trifunctional or higher functional phenol and difunctional phenol with formaldehyde in the presence of an alkali catalyst. (b) A resol resin in which a resol resin having a weight average molecular weight of 800 or more and less than 3,000 is obtained by reacting a trifunctional or higher functional phenol and a bifunctional phenol with formaldehyde in the presence of an alkali catalyst. (c) A weight average molecular weight of 800 obtained by reacting a bifunctional phenol in the presence of a resol resin obtained by reacting a trifunctional or higher functional phenol with formaldehyde in the presence of an alkali catalyst.
Resol resin with a rating of more than 3000 and less than 3000. As the trifunctional or higher functional phenol used in the resol resin of the present invention, all trifunctional or higher functional phenols conventionally used in the production of resol resins can be used, but examples of the trifunctional phenol include phenol (carbolic acid), m- Cresol, m-ethylphenol, 3,5-xylenol, m-methoxyphenol, etc. can be used;
As the functional phenol, bisphenol A, bisphenol B, bisphenol F, 1,1-bis(4-hydroxyphenyl)ethane, etc. can be used. Furthermore, all of the bifunctional phenols conventionally used in the production of resol resins can be used, such as o-cresol, p-cresol, p-tert-butylphenol, p-ethylphenol, 2, 2 such as 3-xylenol, 2,5-xylenol, p-tert aminophenol, p-nonylphenol, p-phenylphenol, p-cyclohexylphenol, etc.
Most preferred is one or a combination of two or more functional phenols. In addition, the alkaline catalysts used for resol resin production include sodium hydroxide, potassium hydroxide,
Preferred are alkali catalysts such as magnesium hydroxide, basic metal salts, ammonia, hexamethylenetetramine, triethylamine, trimethylamine, pyridine, and the like. Phenol and alkali catalysts such as those mentioned above,
In addition, there are various conditions for producing resol resin using formaldehyde, but in particular, when using it as a component of a water-based adhesive can primer, the following conditions (a), (b), or (c) must be met. It is important that the product be manufactured in That is, (a) it is a resol resin obtained by reacting a mixed phenol of trifunctional or higher functional phenol and bifunctional phenol with formaldehyde in the presence of an alkali catalyst so that the weight average molecular weight becomes 800 or more and less than 3000; (b)3
A resol resin obtained by reacting a functional or higher functional phenol and a difunctional phenol individually with formaldehyde in the presence of an alkali catalyst and having a weight average molecular weight of 800 or more and less than 3000, (iii) a trifunctional resol resin; A resol resin obtained by reacting the above phenol and formaldehyde in the presence of an alkali catalyst and having a weight average molecular weight of 800 or more and less than 3,000, which is obtained by reacting a bifunctional phenol in the presence of the resol resin. In such resol resins (a), (b), or (c), it is preferable that the weight ratio of trifunctional or higher-functional phenol to bifunctional phenol is 50-95/50-5. In such a resol resin, trifunctional or higher functional phenols provide content resistance and corrosion resistance, and bifunctional phenols provide flexibility to the resin. Considering the structure of the resin, it is thought that the crosslinking density is adjusted by the trifunctional or higher functional phenol, and the average distance between the crosslinking points is adjusted by the difunctional phenol. and (a), (b) or (c) above.
According to each resol resin manufacturing method, polyfunctional phenols and bifunctional phenols can be connected randomly or in a block shape through methylene bonds. The resol resin obtained in this way has a good balance between processability and adhesion, especially when the weight average molecular weight is 800 or more and less than 3,000. In structures made of steel plates such as free steel) - Primer - Polyamide adhesive, sufficient adhesive strength is maintained not only in the initial adhesive strength but also even after processing strain and aging tests in hot water. A product with excellent properties as a primer can be obtained. Here, high performance liquid chromatography was used to measure the weight average molecular weight. Tetrahydrofuran was used as the solvent, and Shodex GPC A- was used as the column.
Two 80M (product name: manufactured by Showa Denko Co., Ltd.) connected together were used. Sample concentration 0.15%, injection volume
Measurement was carried out under the following conditions: 100μ, flow rate 1ml/min, and differential refractometer detector. Styrene monomer and standard polystyrene A-500, A-
1000, A-2500, A-5000, F-1, F-2, F
-4, F-10, F-20, F-40, and F-80 (manufactured by Toyo Soda Kogyo Co., Ltd.), and the weight average molecular weight was determined as a value in terms of polystyrene. The amount of resol resin in the composite resin composition needs to be 10 to 60 parts by weight based on 100 parts by weight of unmodified bisphenol type epoxy resin,
If the amount is less than 10 parts by weight, the curing properties of the coating film will be poor, and sufficient adhesive strength to the base material and polyamide adhesive will not be obtained. Moreover, if it exceeds 60 parts by weight, physical properties such as processability of the coating film will deteriorate. In the present invention, the bisphenol type epoxy resin used is a commercially available epoxy resin made by reacting bisphenols such as bisphenol A, bisphenol B, and bisphenol F with epichlorohydrin in the presence of an alkali catalyst. The product is Epicoat from Ciel Chemical Co., Ltd.
828, Epicote 1001, Epicote 1004, Epicote 1007, Epicote 1009, Epicote 1010, etc. It is also possible to use a modified epoxy resin in which the epoxy group or hydroxyl group of the bisphenol type epoxy resin is reacted with a vegetable oil fatty acid such as dehydrated castor oil fatty acid, soybean oil fatty acid, or coconut oil fatty acid, or a modifier such as bisphenol A. . The precondensation of the epoxy resin and resol resin is carried out in order to further increase the uniformity of the formed coating film. The precondensation reaction conditions are 90 to 130°C for 1 to 7 hours. In the present invention, the carboxyl group-containing acrylic resin is prepared by adding a monomer mixture consisting of monobasic carboxylic acid monomers such as acrylic acid and methacrylic acid and other copolymerizable monomers to a conventional resin such as azobisisobutyronitrile in an organic solution. It can be obtained by copolymerization using a radical polymerization initiator. The copolymerizable monomers include methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, n-amyl acrylate, isoamyl acrylate, n-hexyl acrylate,
2-ethylhexyl acrylate, n-acrylate
Acrylic esters such as octyl, decyl acrylate, dodecyl acrylate, methyl methacrylate, propyl methacrylate, n-methacrylate
Methacrylic acid esters such as butyl, isobutyl methacrylate, n-amyl methacrylate, n-hexyl methacrylate, n-octyl methacrylate, 2-ethylhexyl methacrylate, decyl methacrylate, dodecyl methacrylate, styrene,
Styrenic monomers such as vinyltoluene, 2-methylstyrene, t-butylstyrene, chlorstyrene, hydroxy group-containing monomers such as hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, N-methylol One or more of N-substituted (meth)acrylic monomers such as (meth)acrylamide and N-butoxymethyl (meth)acrylamide, epoxy group-containing monomers such as glycidyl acrylate and glycidyl methacrylate, and acrylonitrile. You can choose. The amount of monobasic carboxylic acid monomer used is preferably 12 to 70% by weight based on the total monomers; if it is less than 12% by weight, the dispersion stability of the composite resin in an aqueous medium will deteriorate, and if it is more than 70% by weight. When the precondensate is reacted with the precondensate, the temperature of the reaction system becomes extremely high, which is not preferable. Further, the weight average molecular weight of the acrylic resin is preferably in the range of 3,000 to 80,000. In the present invention, the composite resin composition is an epoxy resin that is a precondensation product of an epoxy resin and a resol resin.
10 to 90 parts by weight of acrylic resin to 100 parts by weight in the presence of an esterification catalyst at 60°C to 130°C.
It can be obtained by reacting at ℃ for 30 minutes to 3 hours. Esterification catalysts include inorganic salts such as sodium hydroxide and potassium hydroxide, aluminum amines such as trimethylamine, triethylamine, and butylamine, and polyvalent amines such as 2-dimethylaminoethanol, diethanolamamine, triethanolamine, and aminomethylbrobanol. morpholine, ammonia, etc. In the present invention, the aqueous resin dispersion can be prepared by adding ammonia or amine in an amount such that the final composition has a pH of 4 to 11 and dispersing it in an aqueous medium. When high boiling point solvents are used, it is preferable to remove these solvents in advance under reduced pressure. Examples of the above amines include alkyl amines such as trimethylamine, triethylamine, and butylamine;
Alcohol amines such as 2-dimethylaminoethanol, diethanolamine, triethanolamine, and aminomethylpropanol, morpholine, and the like are used. Polyvalent amines such as ethylenediamine and diethylenetriamine can also be used. In the present invention, the aqueous medium refers to a mixture of water and a hydrophilic organic solvent in which at least 50% by weight or more, preferably 80% or more, more preferably 90% by weight is water, and methanol is used as the hydrophilic organic solvent. , ethanol, n-propanol, isopropanol, n-butanol, sec-butanol,
Alkyl alcohols such as tert-butanol and isobutanol, methyl cellosolve, ethyl cellosolve, propyl cellosolve, butyl cellosolve,
Ether alcohols such as methyl carbitol and ethyl carbitol, ether esters such as methyl cellosolve acetate and ethyl cellosolve acetate, and dioxane, dimethylformamide, diacetone alcohol, etc. are used. The aqueous resin dispersion according to the present invention can be used as a paint by adding a surfactant, an antifoaming agent, etc. to improve coating properties, if necessary. Suitable can materials include untreated steel sheets, treated steel sheets, galvanized iron sheets, tin plates, chrome-plated steel sheets, chromic acid-treated steel sheets, and other stain-free steels, as well as metal sheets such as nickel-plated steel sheets, aluminized steel sheets, and aluminum sheets. As a coating method, roll coater coating is preferred, but spray coating, dipping coating, electrodeposition coating, etc. are also possible. The baking conditions can be selected from the range of temperature 150°C to 230°C and time 2 to 30 minutes. The present invention will be explained below using examples. In addition,
In the examples, "parts" and "%" indicate "parts by weight" and "% by weight," respectively. (Example) Preparation of acrylic resin solution Styrene 130 parts Ethyl acrylate 130 parts Methacrylic acid 140 parts Butyl cellosolve 588 parts Benzoyl peroxide 12 parts A four-necked flask in which the above composition was mixed and one-third of the mixture was replaced with nitrogen gas. The mixture is heated to 80-90℃, and the remaining amount is gradually added dropwise over 2 hours while maintaining this temperature. After the dropwise addition was completed, the reaction was further carried out at that temperature for 2 hours, and then cooled to determine the weight average molecular weight.
17200, a carboxyl group-containing acrylic resin solution with a solid content of 40% was obtained. Preparation of resol resin (A) Bisphenol A 126 parts o-cresol 54 parts 37% formaldehyde aqueous solution 213 parts 25% aqueous ammonia 14.3 parts The above composition was charged into a four-necked flask purged with nitrogen gas, and heated to 95 to 100°C. After reacting for 50 minutes under reflux, a mixed solvent of 30% methyl isobutyl ketone (MIBK), 30% xylene, and 40% butyl cellosolve
Extracted to 350 parts, washed with water, heated at a temperature of 95 to 110°C for about 2 hours, and evaporated water was separated. Further diluted with 240 parts of butyl cellosolve, weight average molecular weight 1830, solid content
A 27% resol resin (A) solution was obtained. Preparation of resol resin (B) In the preparation of the resol resin (A) solution, o-cresol in the composition was changed to p-cresol, and the rest was the same except that the weight average molecular weight was 1290 and the solid content was 27.
% resol resin (B) solution was obtained. Preparation of resol resin (C) 144 parts of carbolic acid 314 parts of 37% formaldehyde aqueous solution 21.1 parts of 25% ammonia water A resin (C) solution was obtained. Preparation of resol resin (D) - Cresol 178 parts 37% formaldehyde aqueous solution 222 parts 25% aqueous ammonia 22.4 parts The above composition was reacted in the same manner as in the preparation of resol resin (A) solution to give a weight average molecular weight of 1320 and a solid content of 27%. A resol resin (D) solution was obtained. Preparation of resol resin (E) Bisphenol A 126 parts 37% formaldehyde aqueous solution 213 parts 25% aqueous ammonia 24.3 parts The above composition was charged into a four-neck flask purged with nitrogen gas, reacted at 65°C for 180 minutes, and then o Add 54 parts of cresol and under reflux at 95°C to 100°C.
The reaction was carried out for 30 minutes, and the rest was carried out in the same manner as in the preparation of resol resin (A), with a weight average molecular weight of 1650 and a solid content of 27.
% resol resin (C) solution was obtained. Preparation of resol resin (F) The same composition as in the preparation of resol resin (A) was prepared at 95°C.
After reacting at 100℃ for 35 minutes, it was washed with water in the same way as the resol resin (A) solution, and heated at 95 to 110℃ for about 80 minutes to separate the water that evaporated.The weight average molecular weight was 690, and the solid content was 27.
% resol resin (F) solution was obtained. The weight average molecular weight of each of the above resol resins was measured using high performance liquid chromatography. Two columns of Syodex GPCA-80M (manufactured by Showa Denko K.K.) were used in series, and the mobile phase was tetrahydrofuran. The sample was diluted with tetrahydrofuran to have a solid content of 0.15%, the injection volume was 100 μ, the mobile phase flow rate was 1 ml/min, and the detector was a differential refractometer. The weight average molecular weight was determined by dividing the obtained chart into minute portions and using the following formula. Here, Hi: magnitude of response of category i _〓 Hi: total of all responses Mi: molecular weight of category i The calibration curve used to determine the molecular weight of each category i is the standard polystyrene equivalent value manufactured by Toyo Soda Kogyo Co., Ltd. It is. Example 1 Resol resin (A) solution 150 parts Epikote 1009 100 parts Acrylic resin solution 50 parts 25% ammonia water 2.7 parts The above composition was placed in a 4-neck flask purged with nitrogen gas and dissolved at 90°C for 3 hours. The temperature was raised to .degree. C. and precondensation was carried out for 3 hours. After cooling to 80°C, the mixture was added to the mixture, reacted at that temperature for 30 minutes, and cooled. The reaction between the resol resin (A), the precondensate of the epoxy resin, and the acrylic resin was confirmed by GPC. Furthermore, ion-exchanged water was gradually added to increase the solid content to 22%.
It was made into an aqueous resin dispersion with a viscosity of 405 cps. In this example, the resol resin content was calculated based on 100 parts of epoxy resin.
40.5 parts were used. Example 2 The resol resin (A) solution of Example 1 was converted into a resol resin.
(B) Solution was used, and the other operations were the same as in Example 1 to obtain an aqueous resin dispersion having a solid content of 22% and a viscosity of 391 cps. Example 3 Instead of the resol resin (A) solution in Example 1, 150 parts of a resol resin solution was used, which was obtained by mixing 105 parts of a resol resin (C) solution and 45 parts of a resol resin (D) solution, and the rest was the same as in Example 3. An aqueous resin dispersion having a solid content of 22% and a viscosity of 443 cps was obtained in the same manner as in 1. Example 4 The resol resin (A) solution of Example 1 was converted into a resol resin.
(E) Solid content 22 in the same manner as in Example 1 except that it was made into a solution.
% and a viscosity of 443 cps was obtained. Example 5 150 parts of the resol resin (A) solution in Example 1 was changed to 75 parts, and the other operations were the same as in Example 1 to reduce the solid content to 22
%, an aqueous resin dispersion with a viscosity of 330 cpc was obtained. In this example, the resol resin content is 20.3 parts per 100 parts of epoxy resin. Example 6 An aqueous resin dispersion having a solid content of 22% and a viscosity of 482 cpc was obtained in the same manner as in Example 1, except that the acrylic resin solution in Example 1 was changed from 50 parts to 100 parts. Comparative Example 1 The resol resin (A) solution of Example 1 was used as a resol resin.
(C) An aqueous resin dispersion having a solid content of 22% and a viscosity of 457 cps was obtained in the same manner as in Example 1 except that it was used as a solution. Comparative Example 2 The resol resin (A) solution of Example 1 was used as a resol resin.
(B) An aqueous resin dispersion having a solid content of 22% and a viscosity of 393 cpc was obtained in the same manner as in Example 1 except that it was used as a solution. Comparative Example 3 The resol resin (A) solution of Example 1 was used as a resol resin.
(F) An aqueous resin dispersion with a solid content of 22% and a viscosity of 339 cpc was obtained in the same manner as in Example 1 except that it was used as a solution. Comparative Example 4 The same procedure as in Example 1 was performed except that 150 parts of the resol resin (A) solution in Example 1 was changed to 20 parts, and the solid content was 22
% and a viscosity of 482 cpc was obtained. In this example, the resol resin content is 5.4 parts with respect to 100 parts of epoxy resin. Using the aqueous resin dispersion obtained in each example and comparative example as an undercoat, roller coating was performed on a chromium-treated steel plate with a thickness of 0.22 mm to a dry film thickness of 2.5 to 3 μ, and then at 210°C for 10 minutes. Baking drying was performed. A 1,2-aminolauric acid polymer was sandwiched between the coated plates, heat-pressed at 200°C for 10 seconds, cooled, and then cut into a 5 mm adhesive width sample piece. A T-shaped peel test was conducted using a tensile strength testing machine. In addition, this adhesive sample was immersed in 90℃ hot water (hot water aging test).
After cooling and drying, a T-shaped peel test was conducted at 25°C. Furthermore, the aqueous resin dispersion of each example was added to a tin plate (0.23
mm thickness, #50/50ET) after roller coating at 200℃, 10
Baking was carried out for a minute to obtain a coated board with a dry coating of 4.5 to 5. A No. 2 can is formed from the above-mentioned painted board, and the contents of a commercially available boiled salmon can are repacked into this No. 2 can.
After performing retort treatment at ℃ for 4 hours, the can was opened and the degree of sulfide blackening on the inner surface was observed. Next, using a special folding Dupont testing machine, a sample folded in half was placed at the bottom, and a 1 kg iron weight with a flat contact surface was dropped from a height of 50 cm. The length was measured, and the crack length was indicated as 0 to 10 mm...○ 10 to 20 mm...Δ 20 mm or more...×. The above test results are shown in Table 1. According to the results, the undercoat according to the present invention exhibits good adhesion both in the untreated state and after aging in hot water. On the other hand, in Comparative Example 1, the adhesion was insufficient when untreated, and in Comparative Examples 2 and 3, a significant decrease in adhesion after aging in hot water was observed, and the present invention This primer has excellent corrosion resistance and processability as a paint for the inside of cans. [Effects of the Invention] The adhesive can primer of the present invention can provide a stable resin dispersion even in an aqueous medium in which the proportion of water in the paint solvent is 90% by weight or more. Since it uses a resol resin with excellent adhesive properties, it has extremely high adhesive properties to the base material and polyamide adhesive.

[Table] * Measured values after mixing phenolic resin

Claims (1)

[Claims] 1 10 to 60 parts of at least one resol resin selected from the following (a), (b), or (c) is preliminarily condensed to 100 parts by weight of a bisphenol type epoxy resin. After that, a potentially self-emulsifying composite resin composition obtained by reacting the precondensate with a carboxyl group-containing acrylic resin in the presence of an esterification catalyst is at least partially neutralized with an amine or ammonia. A water-based primer for adhesive cans that is dispersed in an aqueous medium. (a) A resol resin having a weight average molecular weight of 800 or more and less than 3,000, which is obtained by reacting a mixed phenol of trifunctional or higher functional phenol and difunctional phenol with formaldehyde in the presence of an alkali catalyst. (b) A resol resin obtained by mixing a resol resin with a weight average molecular weight of 800 or more and less than 3,000 obtained by reacting trifunctional or higher phenols and difunctional phenols with formaldehyde in the presence of an alkali catalyst (c) Trifunctional phenols Weight average molecular weight 800 obtained by reacting a bifunctional phenol in the presence of a resol resin obtained by reacting the above phenol and formaldehyde in the presence of an alkali catalyst.
Resol resin with a rating of more than 3000 and less than 3000. 2 In resol resin (a), (b) or (c), 3
2. The water-based undercoat for adhesive cans according to claim 1, wherein the blending ratio of the functional or higher functional phenol to the difunctional phenol is 50-95/50-5 in a polymerization ratio.