JPS6325036B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an undercoat for adhesive cans, and more particularly, to an undercoat used to improve the adhesiveness of the bonded portion of an adhesive can where the side seam of the can body is dynamically bonded with an adhesive. Conventionally, metal cans for packaging soft drinks and foods are made by rolling metal plates into a cylindrical shape, stacking their ends and joining them with adhesive, or by soldering, welding, etc. to form the can body. Cans with top and bottom lid plates attached to the can body are widely known as adhesive cans, solder cans, welded cans, etc. The front and back surfaces of these metal cans are coated with a resin film so that the metal material does not adversely affect the contents, and conversely, so that the metal material is not adversely affected. By the way, some of the metal cans mentioned above are made from tin-plated steel plates, in which the side seams of the can body are joined by soldering or welding, but metal cans such as those made from chrome-plated steel plates or chromic acid-treated steel plates In order to join the can body joints of metal cans made of so-called tain-free steel (TFS) plates, conventional methods have been used to interpose a polyamide adhesive in the overlapping parts and melt and bond the can. There is. In the case of a method using such a polyamide adhesive, an undercoat that also serves as a protection for the inner surface of the can is applied to enhance the adhesiveness. For example, when the content of such adhesive cans is fruit juice, coffee, or other processed foods, heat sterilization, retort sterilization, or hot filling of the contents is performed from the viewpoint of preservation. Since the joints of the side seams will be exposed to hot water, if the adhesive part of the adhesive can is not resistant to hot water, it may break during heat sterilization, or the airtightness of the contents may be compromised during storage. This causes an inconvenience. If even one out of 10,000 such things occurs, there is not only the problem of contaminating the production line or sterilization equipment, but also problems with handling and food hygiene at the distribution and consumption stages. For this reason, research has been carried out on primers to improve adhesion with polyamide adhesives and TFS boards, and an epoxy-phenol basecoat was developed. This is described, for example, in Japanese Patent Application Laid-open No. 100823/1983. However, when these primers were applied using conventional painting methods, there was a problem with the adhesive strength of the can body joint. That is, as shown in FIG. 1, the method for applying this undercoat is generally such that a ten-free steel sheet metal material 1 is continuously conveyed at regular intervals, and the undercoat is sequentially applied to the surface thereof using a roll coater 2.
Next, metal material 1 coated with this primer is coated with a second metal material.
As shown in the figure, each sheet is lifted up one by one using wickets (a metal frame that can be raised and lowered and installed at regular intervals on the conveyor) and then transported to the oven 4 for heating treatment. (drying and baking the paint film), then turn over the metal material that has been coated and baked with primer on one side in the above process, and apply primer on the back side in the same way as on the front side, Heat treatment is performed through an oven,
A primer is applied to at least the part corresponding to the edge joint of the adhesive can, but the adhesive can obtained by joining the can body joint using the metal material coated with the primer in this method is as described above. Hot filling or e.g.
When retort sterilization was performed at 125°C, there was a problem that the ten-free steel plate and the undercoat would peel near the interface and the contents would leak. Furthermore, during long-term storage after hot filling and retort sterilization, the adhesive strength of the can body joints decreases, and eventually peeling occurs near the interface between the ten-free steel plate and the undercoat. There was also the problem that the contents leaked from the peeled area. In addition, with the above-mentioned primer coating method,
In addition to the solvent, the undercoat evaporates during the heat treatment process, as well as hume components (components that are non-volatile at room temperature, different from the originally formulated solvent that evaporates when the undercoat is heat-treated), and this is transferred to the back side of the ten-free steel plate. or adhere to the wicket and inner walls of the oven. Such deposits on the wicket and the inner walls of the oven gradually accumulate as the primer is applied and baked repeatedly, and in the high temperature atmosphere of the oven, this becomes a hard film and eventually cracks. The powder contaminated the oven, and could also adhere to painted metal materials passing through the oven. Such deposits lack uniformity on the painted surface and cause pinholes and repellency in the paint film. In addition, packing food into metal cans made of metal materials that have such deposits is a big food hygiene problem, so to prevent such foreign matter from entering, make sure that there are no deposits on the wick or the inner walls of the oven. It was necessary to periodically remove the existing ones. However, the removal of this deposit must be done manually from every corner of the oven, and it is hard because it not only has good adhesion to the oven surface but also contains materials that have undergone a curing reaction. It adheres and is difficult to remove, requiring a lot of effort and time to remove, which impairs productivity. Also, Special Publication No. 54-34410 (Utility Model Publication No. 53-34410)
No. 55342) discloses an undercoat consisting of a resol type bisphenol formaldehyde resin and a bisphenol A type epoxy resin using a mixed phenol of monovalent phenol and divalent phenol. This is because monohydric phenol is used as an essential component in the phenol component of resol type phenol formaldehyde resin, so the amount of fume caused by this monovalent phenol increases, which not only causes oven contamination as described above, but also There was a problem in that the adhesion of the component to the back surface of the painted board increased the deterioration over time of the adhesiveness of the can seam through the primer coat applied thereon. This is because when the molecular weight of the resol-type phenol-formaldehyde resin obtained by reacting a mixed phenol of monovalent phenol and divalent phenol with formaldehyde is reduced, the amount of low-molecular-weight substances resulting from the monovalent phenol increases relatively. This will increase the amount of fume and contaminate the oven. In addition, if the molecular weight of the resin using the above mixed phenol is increased in order to reduce the amount of fume, the molecular weight of the resin component containing divalent phenol will be too large, and there will be less unreacted bisphenol, which will result in less amount of unreacted bisphenol being contained in the fume component. Since the proportion of soft bisphenols is reduced, the fume build-up becomes hard and brittle and scatters as powder, causing the problems described above. As mentioned above, when applying the primer to a metal material using the conventional method, conventional epoxy-phenol primers are used to remove dirt from the oven, etc., which occurs when the primer is applied to the metal material, and the resulting adhesive container. There are problems with adhesive strength immediately after hot filling and retort processing and after long-term storage. There has been a need for an undercoat that has durable adhesive properties, is less likely to contaminate an oven or the like due to fumes generated during heat treatment of an undercoat film, and can be easily removed even if this contamination occurs. As a result of intensive research to improve the conventional problems as described above, the inventor of the present invention has discovered that epoxy-phenol primers can be used together with solvents when they are applied to metal materials and baked. Volatizes different low molecular weight components (hue components),
For example, when this fume component is transported through an oven by a wicket as shown in the figure, it adheres to the back side of the metal material, and when the primer is directly applied and baked on the back side with this adhered material, the coating film on the back side is formed. It was discovered that the adhesiveness of the fume was problematic, and that the fume component contaminated ovens, wickets, etc., making it difficult to remove. This fume component especially contains low molecular weight components of phenolic resin or decomposition products during heating, and components such as bisphenol have no adverse effect on the adhesive properties of the filled adhesive can during retort or after long-term storage. , found that these reactive components have adverse effects. Furthermore, the above-mentioned problems can be improved by suppressing the amount of fume generated below a certain amount and applying an undercoat that suppresses the reactive components in this fume to below a certain percentage, and the problems described above can be improved. The present invention was developed based on the finding that even when used as is, it is possible to provide an undercoat that requires less frequent cleaning and allows for easy removal of adhered components. Therefore, the present invention provides a number average molecular weight of 2000 to
5500 bisphenol type epoxy resin and 15 to 25 weight% of a resol type bisphenol formaldehyde resin with a number average molecular weight of 600 to 900 and an alkyl etherification rate of less than 10%. The present invention provides an adhesive can undercoat characterized by containing: Next, the present invention will be explained in detail. The adhesive can undercoat of the present invention has a bisphenol type epoxy resin and a resol type bisphenol formaldehyde resin as its main components. A material with adhesive properties is used, but together with this, the amount of fume component generated, which is different from the above-mentioned solvents and which evaporates especially when these resins are baked, is 1.5% of the total solid content.
% by weight, and the proportion of other components other than bisphenol in the hume component is less than 60% by weight. The undercoat of the present invention contains a bisphenol type epoxy resin and a resol type bisphenol formaldehyde resin, and when the undercoat is applied and baked, for example, by the above method, these resins react and harden. The baking conditions are, for example, in an oven at 190 to 210°C for about 10 minutes, so at that time, fume components that are different from the initially blended solvent contained in the resin are generated, and these fumes may adhere to the back side of the metal material. Adheres to the inner wall of the oven. The components of this hume are mainly those derived from resol type bisphenol formaldehyde resin. The details of the production of this resin will be described later, but the molecular weight is adjusted by converting bisphenol into methylol with formaldehyde, converting the phenol nucleus into a polynuclear form by condensation between the methylols, and alkyl etherification reaction. In addition to remaining unreacted raw materials such as , a final product with a different molecular weight distribution is produced, and some of these include low molecular weight products that volatilize during baking under the above conditions. Furthermore, not only those with low molecular weights but also those with high molecular weights may decompose and volatilize under the above baking conditions. These include, for example, bisphenol, which is the main component of this resin,
Examples thereof include bisphenol decomposition products, methylolated products, alkyl etherified products, and aldehyde adducts of these phenol components or decomposed products. Among these, if a primer is applied and baked while a reactive component such as a phenol derivative other than bisphenol is attached to the back side of the metal material, it will cause problems during retort and long-term storage of the adhesive can filled with the contents. This will impair paint film adhesion. In addition, when these reactive fumes adhere to the inner wall of the oven and are heated, they react and harden as the process is repeated, eventually cracking occurs and the fine powder adheres to the painted surface of the metal material, causing food damage in the form of metal cans. Creates hygiene problems. Furthermore, due to the high temperature atmosphere within the oven, unreacted components may also form droplets and fall from the inner wall of the oven, which is undesirable as it contaminates various parts of the oven. For these reasons, in order to maintain adhesive strength during retorting after filling the adhesive can and after long-term storage, and to obtain an undercoat with improved oven contamination, the total amount of fume generated during baking of the undercoat must be The problem is the ratio of the reactive components in the reaction mixture. Therefore, in the present invention, the amount of hume is set to no more than 1.5% based on the solid content of the primer, and the proportion of other components other than bisphenol in the fume is set to be less than 60%. The amount of this fume is preferably 1.0% or less based on the total solid content of the primer, and if it exceeds 1.5%, the oven will have to be cleaned frequently. In addition, the proportion of other components other than bisphenol in hume is preferably 50% or less,
If this exceeds 60%, the adhesive strength of the adhesive can and its adhesion over time will decrease, and the fume that adheres to the oven will harden and become tar, and this tar will further harden, producing fine powder as described above. . The above-mentioned amount of hume and the amount of bisphenol and other components in this hume component can be specifically measured using a thermogravimetric spectrometer and liquid chromatography. In this case, the fume generation condition is a heating rate of 15~
Raise the temperature to 200-210℃ at 20℃/min, then increase the temperature to 200-210℃
Hold at 210°C for 8-12 minutes. In the undercoat comprising the bisphenol type epoxy resin and bisphenol formaldehyde resin of the present invention, the amount of the hume component and the proportion of other components other than bisphenol in the hume component are set to 1.5% and 60% or less as described above. Although it is conceivable to limit the molecular weight distribution, etc., this can also be achieved by limiting the structure, blending ratio, and number average molecular weight of the bisphenol type epoxy resin and the resol type bisphenol formaldehyde resin. From this latter point of view, bisphenol A type epoxy resin is preferred as the bisphenol type epoxy resin, but bisphenol F type epoxy resin can also be used. When using bisphenol A type epoxy resin, its number average molecular weight is 2000~
5500 is preferred. Specifically, the bisphenol A type epoxy resin includes the trade name Epicote 1007,
1009 etc. (manufactured by Yuka Ciel Epoxy), Araldite 6097, 6099 (manufactured by Ciba, Switzerland), Epicron
7050, 9050 (manufactured by Dainippon Ink and Chemicals),
Examples include AER667 and 669 (manufactured by Asahi Kasei Industries, Ltd.), but those with a number average molecular weight of 2,500 to 2,500 are particularly preferable in terms of adhesion to metal materials and rigidity of the coating film.
5500 bisphenol A type epoxy resin. Further, as the resol type bisphenol formaldehyde resin, one using bisphenol A as the bisphenol is preferable, but bisphenol F can also be used. This resol type bisphenol formaldehyde resin is, for example, bisphenol
After reacting 1 mole of A with 1 to 3 moles of formaldehyde in the presence of a basic catalyst, a small amount of ketone, a hydrocarbon solvent, and optionally an alcohol (preferably an alcohol having 4 to 8 carbon atoms) is added and dissolved.
It can be produced by simultaneously carrying out dehydration, alkyl etherification reaction, and phenol polynuclearization reaction using a solvent azeotropic method. In this case, basic catalysts include ammonia, sodium hydroxide, magnesium hydroxide, triethylamine, etc., and these are 0.01 to 0.8 mol per mole of bisphenol A.
molar added. Also, the reaction conditions for this reaction are 50
~100°C for 1 to 15 hours is exemplified. The resol type bisphenol formaldehyde resin does not need to be alkyl etherified, but when it is alkyl etherified, for example, in the case of a resol type bisphenol A formaldehyde resin, the alkyl etherification rate is preferably lower than 10%. If the alkyl etherification rate is too high, exceeding 10%, the amount of reactive components in the fume component that volatilizes during baking increases. These components adhere to metal materials and the inner walls of the oven, causing a curing reaction. Therefore, if the alkyl etherification rate is too high, the initial adhesive strength of the coating film will be high when the undercoat containing resol-type bisphenol A formaldehyde resin and the above-mentioned epoxy resin is applied and baked on the back side of the metal material to which the fume is attached. However, when an adhesive can is filled with contents and stored for a long period of time, the adhesive strength of the joints is significantly reduced, making it easier for the contents to leak. Furthermore, as described above, the oven is likely to be contaminated, and the coated metal material is likely to be contaminated by the powder of the cured product. In addition, the number average molecular weight of the resol type bisphenol A formaldehyde resin used in the present invention is
600-900 is preferred. If this is less than 600, the undercoat film combined with the above-mentioned epoxy resin will have poor curability and the rigidity of the film will be insufficient. Furthermore, if the number average molecular weight exceeds 900, the undercoat film mixed with the epoxy resin becomes hard, and a broken can is likely to occur during retort processing, which is unsuitable. The suitable molecular weight distribution of such a resol type bisphenol formaldehyde resin is such that the weight average molecular weight/number average molecular weight ratio is 4 or less, preferably 2.5 or less. The above-mentioned bisphenol type epoxy resin and resol type bisphenol formaldehyde resin may be simply mixed and used as an undercoating agent, or they may be precondensed by causing some reaction between the two. In these cases, the mixing ratio of both is 75 to 75 for the former.
85% by weight, the latter 15-25% by weight. The latter is 25
If it exceeds % by weight, the coating film becomes hard and tends to be easily broken during retort treatment, and the amount of fume increases, which may make it unsuitable as an undercoat. If the latter is less than 15% by weight, the amount of fume will be small, but the adhesive strength of the coating will be low. The amount of formaldehyde per mole of bisphenol in the resol type bisphenol formaldehyde resin is preferably 1 to 3 moles, more preferably 1.5 to 2.5 moles. If the amount is less than 1 mol, the undercoat film made of the above-mentioned bisphenol type epoxy resin will be insufficiently cured and its adhesive strength to metal materials will be low. Further, the amount of unreacted bisphenol increases, the amount of fume increases, and the tar of the fume that adheres to the oven etc. becomes soft. In the above, if the formaldehyde content is more than 3 moles, the coating film will be cured too much. In addition, there are many reactive components other than bisphenol as a hume component,
When an adhesive can is filled with contents and stored for a long period of time, the adhesive strength tends to decrease over time. Further, the fume cured product adhering to the oven or the like becomes hard, causing the problem that the cracked powder is scattered as described above. As mentioned above, by appropriately selecting a bisphenol type epoxy resin and a resol type bisphenol formaldehyde resin, it is possible to provide an undercoat for adhesive cans that improves oven stains and has adhesive properties that can withstand retort processing. become. In addition to the above-mentioned undercoating agent of the present invention, a resol type bisphenol formaldehyde resin using monovalent phenol as the phenol component and other phenolic resins may be used in combination to the extent that no fume generation is caused. In this way, when a resol-type bisphenol formaldehyde resin of monovalent phenol is used in combination, it is preferable for a resol-type bisphenol formaldehyde resin using only monovalent phenol, compared to a case where a mixed phenol of monovalent phenol and divalent phenol is used. It is possible to select a compound having a molecular weight, thereby reducing the source of low molecular weight substances, that is, fumes caused by monovalent phenols. Further, auxiliary agents, colorants, waxes, etc. commonly used in undercoating agents may be added. The primer of the present invention is manufactured by a conventional method, and when used, it is applied and baked using, for example, the illustrated apparatus. The can making machine then glues the joints of the can body with, for example, polyamide adhesive to create a bonded can.The metal materials for such bonded cans include iron plates, aluminum plates, and zinc, chromium, aluminum, etc. plated on the surface of the iron plate. Examples include steel sheets whose surfaces have been chemically treated with chromic acid or phosphoric acid, or whose surfaces have been subjected to cathodic electrolytic treatment. After optionally cleaning these metal materials with a degreasing solvent such as 1,1,1-trichloroethane, the surface can be coated using conventional methods, such as brush coating, roller coating, spray coating, dip coating, electrostatic coating, or electrodeposition coating. After the primer is applied so that the baked coating layer has a thickness of 1 to 15μ, it is baked at 180℃ to 250℃ for 1 to 20μ
A cured coating film for adhesive cans is formed by heating and baking with hot air or infrared rays for minutes. The adhesive bonding conditions for the can body joint vary depending on the type of polyamide adhesive used, but since the melting point of the adhesive is usually around 100 to 240℃, the bonding temperature should be in the range of 120 to 300℃. You can do it as you like. Such polyamide adhesives include sheets,
Various materials such as pellets, films, powders, solutions or dispersions can be used as desired. According to the present invention, the adhesive container contains a resol-type bisphenol formaldehyde resin in which bisphenol, which is a divalent phenol, is used as a phenol component and an epoxy resin, and the molecular weight and blending amount of each resin are limited. It not only shows excellent adhesion as an undercoat and can withstand hot filling and retort sterilization, but also reduces the fume when heat-treated to less than 1.5% of the solid content of the undercoat. 60% of the other components except bisphenol that occupy this hume component
It can be less than %. Since the hum can be controlled in this way, it is possible to
-55342 publication) using a mixed phenol of monohydric phenol and divalent phenol, and resol type with an alkyl etherification rate of 10% or more described in Utility Model Application Publication No. 56-100823. It does not have a large amount of fume like bisphenol formaldehyde resin. If the amount of fume is not large like this, the metal material coated with primer by the coating equipment will be transferred to the oven and baked, and then the back side of the baked metal material will be coated with primer again in the same way and baked. By using it, it is possible to reduce the decrease in the economic adhesive strength of the side seam of the adhesive can, and there is also less fume component adhering to ovens, etc., so the number of regular cleanings can be reduced, and the adhering components can be removed. Since the reactivity is low, it has the advantage that it can be easily removed. Next, examples of the present invention will be described, but the present invention is not limited thereto. In the following description, "part" and "%" indicate weight unless otherwise specified. In addition, in the following description, "", "N ₁ ",
"N ₂ " and "E" are each defined as follows. : Number average molecular weight N ₁ : Number of methylol groups added to 1 mole of bisphenol A N ₂ : Number of methylol groups converted into alkyl ether E: Alkyl etherification rate (%) calculated by (N ₂ /N ₁ +N ₂ )×100 The measurement of was carried out by gel passage chromatography, and the measurement of N ₁ and N ₂ was carried out by NMR spectrum analysis. Synthesis Example 1 41 parts of 40% formaldehyde in 1-butanol solution (water content 10%) in 100 parts of bisphenol A,
40 parts of a 41.5% formaldehyde aqueous solution and 8 parts of a 25% ammonia aqueous solution were added and reacted at 75°C for 1.5 hours. Then, 37 parts of 1-butanol and 86 parts of xylol were added to this reaction condensate, and the mixture was azeotropically dehydrated at 105-110°C. Due to this reaction = 810, N ₁ =
A solution (solid content: 43%) of resol type bisphenol A _formaldehyde resin (43%) was obtained. Synthesis Example 2 After carrying out the first stage reaction of Synthesis Example 1, a mixed solvent of 12 parts of 1-butanol, 29 parts of butyl cellosolve and 86 parts of xylol was added, and azeotropic dehydration was carried out at 105 to 110°C. Due to this reaction = 850, N ₁ = 0.80, N ₂
= 0.07, E = 8 (%) solution of resol type bisphenol A formaldehyde resin (solid content
48%). Synthesis Example 3 To 100 parts of bisphenol A were added 63 parts of a 41.5% formaldehyde aqueous solution and 6 parts of a 25% ammonia aqueous solution, and the mixture was reacted at 80°C for 2 hours. Next, a mixed solvent consisting of 90 parts of methyl isobutyl ketone, 60 parts of cyclohexanone, and 150 parts of xylol was added to this reaction condensate to dissolve it, and after washing with water, water was removed by azeotropic distillation. Due to this reaction = 690,
A solution (solid content: 30%) of resol type bisphenol A formaldehyde resin (2) with N ₁ =0.83, N ₂ =0, and E = 0 (%) was obtained. Synthesis Example 4 Same as Synthesis Example 3 except that the reaction conditions were 80°C and 1 hour, =590, N ₁ =
A solution (solid content: 29%) of resol type bisphenol A formaldehyde resin (29% ₎ was obtained. Synthesis Example 5 Same reaction conditions as Synthesis Example 3 except that 79 parts of 41.5% formaldehyde aqueous solution was used and the reaction was carried out at 80°C for 3.5 hours = 920, N ₁ = 0.85,
A solution of resol type bisphenol A formaldehyde resin () with N ₂ = 0, E = 0% (solid content 32
%) was obtained. Synthesis Example 6 90.3 parts of a 37% formalin aqueous solution and 10 parts of a 25% ammonia aqueous solution were added to a phenol mixture of 75 parts of P-cresol and 25 parts of 0-cresol, and the mixture was heated at 80°C.
Allowed time to react. Next, this was dehydrated under reduced pressure, and then dissolved in a mixed solvent of equal amounts of xylene and 1-butanol to obtain a solution (solid content: 56%) of resol type bisphenol formaldehyde resin (2). Synthesis Example 7 In Synthesis Example 6, p was substituted for O-cresol.
A solution (solid content: 53%) of resol type bisphenol formaldehyde resin (XI) was obtained in the same manner except that -t-butylphenol was used. Synthesis Example 8 49.3 parts of 40% formaldehyde in 1-butanol solution (water content 10%) in 100 parts of bisphenol,
The mixture was added to 49 parts of a 41.5% formaldehyde aqueous solution and 8 parts of a 25% ammonia aqueous solution, and reacted at 80°C for 3 hours. Next, 90 parts of 1-butanol and 20 parts of xylol were added to this reaction condensate, and the mixture was azeotropically dehydrated at 105-110°C. Due to this reaction = 940, N ₁ =
A solution (solid content: 53%) of resol type bisphenol A formaldehyde resin (') with N ₂ = 0.40, N 2 = 0.40, and E = 50 (%) was obtained. Synthesis Example 9 After performing the first stage reaction in Synthesis Example 8, 1-
A mixed solvent of 70 parts of butanol, 28 parts of butyl cellosolve, and 15 parts of xylene was added, and azeotropic dehydration was performed at 105 to 110°C. Due to this reaction = 890, N ₁ = 0.61,
A solution (solid content: 51%) of resol type bisphenol A formaldehyde resin (') with N ₂ =0.26 and E = 30 (%) was obtained. Synthesis Example 10 Add 69 parts of a 41.5% formaldehyde aqueous solution (2.0 mol/1 mol of mixed phenol) to a mixed phenol of 85 parts of bisphenol A and 15 parts of O-cresol, heat to dissolve the mixed phenol, and add a 25% ammonia aqueous solution. 3.2 parts (0.1 mol/1 mol of mixed phenol) was added and reacted at 95°C for 3 hours. Next, methyl isobutyl ketone 30 was added to this reaction condensate.
%, 250 parts of a mixed solvent consisting of 20% cyclohexanone and 50% xylene were added, mixed uniformly, and washed with water. After this time water was removed by sedimentation. Through this reaction, a solution (solid content: 33%) of resol type bisphenol formaldehyde resin (XII) with =750 and E = 0 (%) was obtained. Synthesis Example 11 Add 89 parts of a 41.5% formaldehyde aqueous solution (2.5 mol/1 mol of mixed phenol) to a mixed phenol of 80 parts of bisphenol A and 20 parts of p-cresol, heat to dissolve the mixed phenol, and add a 25% ammonia aqueous solution. 6.7 parts (0.2 mol/1 mol of mixed phenol) were added and reacted at 80°C for 3 hours. Process this in the same way as Synthesis Example 10 = 970, E = 0
(%) of resol type bisphenol formaldehyde resin (solid content 34%) was obtained. Example (1) Preparation of primer: Epoxy resin Epicoat 1009 (=3750
manufactured by Yuka Ciel Epoxy Co., Ltd.) or Epicote 1007
(=2900, manufactured by the company) with 30% cyclohexanone,
It was dissolved in a mixed solvent consisting of 30% ethylene glycol monobutyl ether, 25% xylene, and 15% diacetone alcohol, and mixed with various phenolic resins described in the synthesis examples so that the resin composition ratio shown in Table 1 was obtained. An appropriate amount of mixed solvent was added to prepare an undercoat with a solid content of 30%. However, in Table 1, the Roman numerals . . . indicate the resol type bisphenol A formaldehyde resin in each of the above examples. The primer of Example 6 was obtained by precondensing an epoxy resin and a resol type bisphenol A formaldehyde resin at 120°C for 1 hour. Further, the undercoating agents of Comparative Examples 8 and 9 were obtained by precondensing an epoxy resin and a resol type bisphenol formaldehyde resin at 110° C. for 3 hours. (2) Painting with primer stain-free steel plate (TFS) plate (approximately 800×
1000 x 0.22 mm) with a roll coater at a speed of 100 sheets per minute so that the coating amount after baking is 55 mg/10 ^cm2 , and then coated on a conveyor at approximately 2.5 cm intervals. It was placed on a wicket attached to a wick, passed through a tunnel oven, and baked at 190°C for 10 minutes. Then, as with the previous surface, apply an undercoat on the back side with a coating amount of 25 mg/100 cm ^2.
It was coated with a roll coater so that the surface was coated, and as in the case of the above surface, it was placed on a wicket, passed through a tunnel oven, and baked at 210°C for 10 minutes. Next, on a separate line from the primer coating, apply an inner top coat to the surface except for the can body joint on both sides of the above-coated stain-free steel plate, and apply a white coat to the back surface and print. ,
Finishing varnish was applied and baked to create a painted board for testing. (3) Humidity contamination test After baking the primer coated on the front or back side of a stain-free steel plate for approximately 1 million sheets using the same wicket group and using a tunnel oven, the inlet hood of the tunnel oven, The state of adhesion of fume to the wickets (amount of adhesion, its condition) was observed, and the ease of removing the fume (ease of cleaning) was examined. The results are shown in Table 2. In Table 2, 〇 means easy to clean, △ means difficult to clean, and × means fume adheres to the inner wall of the oven in the form of a film, which cracks and scatters as small particles, contaminating the oven and painted metal materials. Show that. (4) Measurement of the amount and composition of hume components 40 mg of the sample dried by leaving the undercoat of each of the above Examples and Comparative Examples at room temperature for 24 hours.
Set in a TGA (thermogravimetric spectrometer) and raise the temperature of the sample in an air atmosphere from room temperature to 210°C at a rate of 20°C/min.
When the temperature is raised to 210°C and held for 10 minutes, the fume generated from the sample adheres to the quartz protection tube. Wash out this attached fume with methanol.
Perform HLC (liquid chromatography) measurement.
HLC measurements were performed using a reversed phase ODS column with water/methanol as the mobile phase. Qualitative and quantitative detection was performed using a UV detector (254 nm), and a previously prepared calibration curve was used for quantitative determination. Components without standard substances were quantified using a bisphenol A calibration curve. (4) Can manufacturing A metal material is formed by cutting the above-mentioned painted board into a size that matches the specified can body, and a 40μ thick polyamide film (Daicel Chemical
Nylon 12) made by Co., Ltd. is rolled and crimped, and then both edges to which the film is attached are heated by high-frequency heating.
Shaped into a cylindrical shape using a regular can body forming machine, with 5mm edges on both ends.
Overlapping the width, crimping for a short time and then rapidly cooling, every minute.
A can body was created at a speed of 450 cans. Next, the bottom lid was double-tightened to create a 250g empty can. (5) Physical property test After filling the above empty can with hot water at 95℃ and tightening the canopy, retort treatment at 130℃ for 60 minutes to determine the number of broken cans, the adhesive strength of the adhesive part, and the degree of vacuum inside the can. was measured. The results are shown in Table 2.

【table】

[Table] From the results in Table 2, Examples 1 to 6 are good in all measurement items, but Comparative Example 1 has a high butyl etherification rate, so oven contamination is poor, and adhesive strength deteriorates over time. This is because the amount of fume is large and its reactive components are also large. Furthermore, in Comparative Example 2, the initial adhesive strength was low because the amount of resol type bisphenol A formaldehyde resin was small. Furthermore, since Comparative Example 3 contains a large amount of resol-type bisphenol A formaldehyde resin, broken cans are likely to occur during retort processing, and there is also a problem in oven contamination. Further, in Comparative Example 4, since the molecular weight of the resol type bisphenol A formaldehyde resin is small, the amount of fume is large, and like Comparative Example 3, the oven staining property is poor. This seems to be due to an increase in low molecular weight components. Furthermore, in Comparative Example 5, the can was broken because the molecular weight of the resol-type bisphenol A formaldehyde resin was too large. In addition, in Comparative Example 6, the butyl etherification rate and the molecular weight of the resol type bisphenol A formaldehyde resin were too large, so the adhesive properties deteriorated over time and the degree of oven contamination was large. In addition, in Comparative Example 7, the butyl etherification rate was too high, resulting in a large amount of fume generation, which caused deterioration of adhesive properties over time and also caused a high degree of oven contamination. In addition, in Comparative Example 8, there was a large amount of fume due to monovalent phenol in the resol type mixed phenol formaldehyde resin, and there were problems with long-term storage of the can and oven contamination. However, although the amount of hume is slightly reduced, the tar accumulated in the oven hardens, becomes brittle, becomes powder, and scatters, contaminating the oven. In addition, this comparative example 8,
No. 9 corresponds to the resol type bisphenol formaldehyde resin using mixed phenol described in Japanese Utility Model Publication No. 54-34410.

[Brief explanation of the drawing]

FIG. 1 is an explanatory view of a part of the coating apparatus, and FIG. 2 is a front view of the wicket with a metal material loaded thereon.

Claims (1)

[Claims] 1. 75 to 85% by weight of a bisphenol type epoxy resin with a number average molecular weight of 2000 to 5500 and a number average molecular weight of 600.
~900 resol type bisphenol formaldehyde resin with alkyl etherification rate less than 10%
An undercoat for adhesive cans, characterized by containing a resin mixed or precondensed with 15 to 25% by weight. 2. Resol type bisphenol formaldehyde resin converts bisphenol A1 in the presence of a basic catalyst.
It is characterized by being a resin produced by reacting 1 to 3 moles of formaldehyde per mole, and further performing dehydration, alkyl etherification, and polynuclear reaction of the phenol component in a solvent that does not contain or contains a small amount of alcohol. An undercoat for adhesive cans according to claim 1.