JPS6410029B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an adhesive primer for metal containers that is applied to metal and used for adhesion with a copolyester adhesive. , relates to an adhesive primer used for manufacturing bottle-shaped metal containers by bonding them at their circumferential ends with a copolyester adhesive. The upper body and the lower body, which are cup-shaped molded bodies formed by drawing or drawing and ironing of metal materials, are lap-joined at the circumferential open ends, and the circumferential side seams are joined. The formed bottle-shaped metal containers have many advantages over so-called can-shaped metal containers. Among conventional metal containers for packaging, those called three-piece cans have a can lid double-sealed to the top and bottom of the can body, which has side seams, to form a sealed part, and those called two-piece cans In this case, a sealed portion is formed by double seaming between the open end of a cup-shaped can body formed by drawing or drawing-ironing a metal material and the can lid. However, such a double-sealed metal container is subject to major limitations in terms of pressure resistance of the secret area and in terms of saving the metal material. That is,
In double-sealed joints, the material that makes up the joint deforms first due to the load applied to the joint, and this deformation causes joint leakage and joint failure to occur with relatively small loads. . In order to prevent this, the material itself must be considerably thicker. In addition, in packaging containers, it is always required to make the metal material used thinner, both from the standpoint of economy and from the standpoint of reducing the weight of the container, but when making the container body wall thinner, there are two There is a problem in that buckling is likely to occur due to loads applied in the axial direction of the container during heavy seaming processes or preparatory processes such as flange processing. A bottle-shaped metal container, which is formed by lap-joining an upper body and a lower body each made of a cup-shaped molded body at their open ends, will not deform the material at the joint even if the material forming the joint is extremely thin. It has the advantage of being able to withstand up to the shear strength of the seam, which is unrelated to the thickness of the material, and because it does not require a seaming process, the side wall of the container can be made thinner without the risk of buckling. There is. However, when the lower body and the upper body are lap-joined at their circumferential open ends to form a circumferential side seam, the adhesive primer interposed between the adhesive layer and the metal material is most severely damaged. conditions will be required. In other words, in the case of a straight lap joint of the can body, both ends of the joint are mechanically fixed by seaming to the can lid, but in the case of the circumferential side joint described above, the joint is secured all around the entire circumference. There is no mechanical fixation across the joint, and the seam itself is easily subject to dimensional deformation or shear stress in the seam. Furthermore, since the diameter of the open end tends to change due to temperature changes, stress is likely to occur at the joint. Furthermore, the open ends forming the joints are often thinned, and the joints tend to be easily deformed by external forces. Even if the metal material or thermoplastic adhesive present at this joint can absorb or withstand such stress, the adhesive primer interposed between the metal material and the adhesive will not be able to withstand this stress. There is a tendency for adhesion or adhesion to deteriorate significantly. Furthermore, since the lower body and upper body are formed through advanced drawing and drawing-iron processing, the coating film that serves as an adhesive primer and protective layer must withstand these forming processes and has excellent corrosion resistance. Must. According to the present invention, (A) degree of polymerization is 800 on a solid content basis.
10 to 80% by weight of vinyl chloride resin particles of 4000 to 4000, (B) 5 to 80% by weight of carboxyl groups and/or hydroxyl groups
Solvent-soluble vinyl chloride-vinyl acetate-carboxyl group- or hydroxyl group-containing vinyl unit copolymer 10 to 80 containing at a concentration of 500 mmol/100 g polymer
Weight% and (C) Solvent-soluble thermosetting resin 2 having reactivity with carboxy groups and/or hydroxyl groups
The copolymer (B) and the thermosetting resin (C) are contained in a continuous phase as a dispersion medium, and the vinyl chloride resin particles (A) are present in the continuous phase as a dispersion medium. An adhesive primer for metal containers is provided for application to metal and for use in bonding with copolyester adhesives, characterized in that it is present in the form of dispersed dispersoids. The invention will be explained in detail below. In FIGS. 1 to 3 showing an example of a bottle-shaped metal container, this container has a lower body 1 made of a seamless cup-shaped molded body made of, for example, painted metal, and an upper part made of a seamless cup-shaped molded body made of painted metal. These cup-shaped molded bodies are integrated into the shape of a container by overlapping and joining open ends 3 and 4 to form a circumferential side seam 5. has been done. In this specific example, the lower body 1 is a cup consisting of a side wall portion 6 and a bottom portion 7 formed by drawing a painted metal material, and the upper body 2 also has a side wall portion 8 formed by drawing a painted metal material. It is a cup consisting of an upper wall 9. The side walls 6 of the lower body 1 and the side walls 8 of the upper body 2 have approximately the same diameter and, in this embodiment, their heights are also approximately the same, with the seam 5 at approximately the mid-height of the container. positioned. The upper wall 9 of the upper body 2 has an upwardly convex tapered surface, and a spout 10 for filling or taking out the contents is formed in the center thereof. It will thus be clear that the upper body 2 is joined onto the lower body in the form of a so-called shoulder, neck and torso half of a bottle. In the specific example shown in FIG. 1, the open end 3 of the lower body 1 is narrowed to a smaller diameter than the rest of the body wall by neck-in processing in the vicinity of the open end 3. It is inserted into the open end 4 of the lower body of the diameter. As shown in an enlarged view in FIG. 3, the painted metal materials constituting the lower body and the upper body include a metal substrate 11 such as surface-treated aluminum and a coating film 12 applied to the surface as an adhesive primer and protective layer.
a, 12b. Lower body open end 3
An adhesive layer 13 is provided between the outer surface of the upper body and the inner surface of the open end 4 of the upper body, and the bonding between the lower body and the upper body,
Fixation is taking place. A portion of the adhesive 13 is attached to the seam 5
From the viewpoint of corrosion resistance, it is desirable to form a coating layer 15 on the cut edge 14 of the metal material located inside the seam so as to protrude from the seam. In the present invention, the coating films 12a and 12b have the following composition, that is, on a solid content basis, (A) a degree of polymerization of 800 to 4000;
10 to 80% by weight of vinyl chloride resin particles, (B) a solvent-soluble vinyl chloride-vinyl acetate-carboxyl group or hydroxyl group containing carboxyl groups and/or hydroxyl groups at a concentration of 5 to 500 mmol/100 g of polymer. Consisting of a composition containing 10 to 80% by weight of a copolymer containing vinyl units and (C) 2 to 30% by weight of a solvent-soluble thermosetting resin that is reactive with carboxy groups and/or hydroxyl groups. It is unique in that it uses paint. The vinyl chloride resin coating film with the specific composition mentioned above is
It has sufficient adhesion to metal substrates not only under normal bonding conditions, but also after filling with corrosive substances or after heat sterilization, and also improves the workability of the coating film and as a protective coating. offers significant advantages in terms of corrosion resistance. As will be detailed later, this composition provides a coating film with excellent adhesion to metal substrates, mechanical properties, and workability, and metal materials with this coating film can be subjected to advanced drawing processes, such as drawing-redrawing. Even when subjected to drawing processing, etc., coating film defects such as peeling cracks, pinholes, and wrinkles do not occur. In addition, vinyl chloride resin has excellent water resistance even though it has relatively strong polarity, and also exhibits excellent barrier properties against metal corrosive components contained in the contents of the container. In the paint of the present invention, vinyl chloride resin particles
(A) acts to increase the amount or concentration of vinyl chloride units in the coating film, thereby increasing the barrier properties of the coating film against corrosive components. In addition, vinyl chloride resin particles (A) significantly improve the workability of the paint film compared to paints that do not contain these particles, and can be used to draw painted metal sheets without causing the aforementioned paint film defects. This enables deep drawing processing, etc. Furthermore, the vinyl chloride resin particles have the advantage of improving coating workability and enabling thick coating on metal materials. Furthermore, the vinyl chloride resin particles (A) increase the amount or concentration of vinyl chloride units in the coating film, thereby increasing the adhesiveness with the copolyester adhesive. This utilizes the phenomenon that a vinyl chloride resin coating and a copolyester adhesive form a strong adhesive bond when heated. That is, according to the research conducted by the present inventors, when a copolyester adhesive is heat-sealed to a vinyl chloride resin coating, the two resins are mixed extremely well at the bonding interface between the two. This is thought to be the reason why strong adhesion is possible. Despite the fact that these two resins have completely different chemical structures, their good mixing under heat fusion conditions is related to the fact that the solubility indices of both resins are quite close. It is recognized that Solubility index (Solubility Parameter, Sp value)
For example, J. BRANDRUP et al.
Handbook” Chapter 4 (Johm Wiley & Soons,
Inc., 1967), it is defined as the 1/2 power of the cohesive energy density (cal/cc). This solubility index is closely related to the strength of hydrogen bonds in thermoplastic resins, and
Thermoplastic polymers containing polar groups such as amide groups, ester groups, nitrile groups, or chlorine atoms in the polymer main chain or side chains generally have 9 It shows a high solubility index. Table A below shows polyvinyl chloride, polyethylene terephthalate, and polybutylene terephthalate.
Indicates S _P value.

[Paint adjustment]

The paint used in the following examples contains the following components (1) to (5) in the proportions shown in Table 1, and has a non-volatile content.
It is dissolved and/or dispersed in a solvent to a concentration of 40% by weight. (1) Vinyl chloride resin: In a 500ml stainless steel autoclave equipped with an electromagnetic induction stirrer and a pressure gauge, add 300ml of distilled water,
After adding 0.6 g of sodium dodecylbenzenesulfonate and 0.10 g of potassium persulfate, the lid was closed and the autoclave was placed in a dry ice-methanol bath.
After cooling to 20°C and purging with nitrogen, 100g of liquid vinyl chloride monomer was charged. Then temperature
The temperature was raised to 53°C and polymerization was carried out with stirring. After reacting for 8 hours, return to room temperature, remove residual monomer,
The interior is then purged with nitrogen. The resulting emulsion is diluted to 15% with water, and when 5% saline is added while stirring, polyvinyl chloride is precipitated. The precipitated polymer is washed with water, filtered by suction, and dried. The degree of polymerization was 1250. In the same manner, vinyl chloride resins with polymerization degrees of 730, 3640, and 4230 were synthesized. (2) Vinyl chloride copolymer resin: In an autoclave, add 300 ml of water in which 0.6 g of polyvinyl alcohol with a hydrolysis rate of 80% is dissolved, 0.15 g of azobisisobityronitrile, and 10 g of vinyl acetate monomer, and add dry ice-methanol. Cool to -20°C in a bath. Next, 90 g of liquid vinyl chloride monomer is added. The temperature was raised to 58°C and polymerization was carried out for 3 hours with stirring. The obtained polymer has a polymerization degree of 325 and a vinyl chloride/
The composition was vinyl acetate = 91/9 (wt%) (this is designated as V-1). Similarly, polymerization degree 290, vinyl chloride/vinyl acetate = 75/25 (wt%) (V-2), and polymerization degree 315, vinyl chloride/vinyl acetate = 71/29 (wt%) (V-3) A vinyl chloride-vinyl acetate copolymer was synthesized. Also, the degree of polymerization is 305, vinyl chloride/vinyl acetate/
Maleic anhydride = 91/8.8/0.2 (wt%) (V-
4), and degree of polymerization 290, vinyl chloride/vinyl acetate/maleic anhydride = 90/9.5/0.5 (wt%)
(V-5), and degree of polymerization 295, vinyl chloride/vinyl acetate/maleic anhydride = 86/11/3 (wt%)
The terpolymer (V-6) was also synthesized in the same manner. In addition, by partially saponifying the vinyl chloride-vinyl acetate copolymers V-1, V-2, and V-3 with an alkali, vinyl chloride-vinyl acetate-
A vinyl alcohol copolymer was obtained. Each,
Degree of polymerization 325, vinyl chloride/vinyl acetate/vinyl alcohol = 91/3/6 (wt%) (V-7);
Degree of polymerization 290, vinyl chloride/vinyl acetate/vinyl alcohol = 75/6/19 (wt%) (V-8);
The degree of polymerization was 315, and the composition was vinyl chloride/vinyl acetate/vinyl alcohol=71/5/24 (wt%) (V-9). (3) Epoxy resin: Epon828 (product of Ciel Chemical Co., Ltd., trade name, bisphenol A type epoxy resin, average molecular weight 380,
Epoxy equivalent: 184-194) (4) Amino resin: Betsukamine P-138 (product of Dainippon Ink Co., Ltd., butyl etherified urea resin) (5) Phenol resin: 37 mol of carbolic acid and 0.5 mol of p-cresol
% formaldehyde aqueous solution 1.5 mol,
0.15 mol of ammonia was added as a catalyst, and the mixture was reacted at 95°C for 3 hours. The reaction product is extruded using a mixed solvent consisting of ketones, alcohols, hydrocarbons, etc., washed with water, the aqueous layer is removed, a small amount of remaining water is removed using an azeotropic method, and the product is cooled to form a resol-type phenolic resin. A 30% solution was obtained. Furthermore, in the following examples, metal containers were evaluated according to the method described below. [Evaluation of metal containers] (a) Measurement of shear strength of joints The metal containers after joining and those filled with water and aged at 70℃ for 10 hours were measured at 7 cm in the height direction, respectively. A sample piece containing a 2 cm circumferential joint was cut out and subjected to a shear fracture test using Tensilon at a tensile rate of 100 mm/min at room temperature, and was expressed as shear strength taking into account the adhesive area of the lap joint. Measurements were made for each of three containers, and the arithmetic mean value was taken as the measured value. In addition, here 54-57Kg/cm ²
Items marked as above indicate that the plate has broken, and the actual strength is greater than this value. (b) Measurement of peel strength of joints The joints of the metal containers after joining and those filled with water and aged at 70°C for 10 hours were cut out in a circumferential shape and measured using a Tensilon. A T-peel fracture test was conducted at room temperature at a tensile speed of 200 mm/min.The average peel strength was determined for each of the three containers, taking into account the width of the lap joint, and the main fracture types were determined. Between the paint film and the plate. Paint film-adhesive,. glue,
．． The coating film was classified and visually observed as shown in the table above. (c) Denting test After filling each metal container with the specified contents, a weight A weighing 4 kg is placed at an angle of 22.5° horizontally from a certain height (6 mm) as shown in Figure 4. Let it fall naturally vertically to a position 0.3 mm from the edge of the external body of the metal container B joint part that is inclined at an angle. In this test, if the upper body and bottom body have separated or a gap has occurred at the joint, the body will be broken and heated at 23℃.
After 48 hours of standing, the internal pressure was measured, and if a decrease of 5% or more was observed compared to immediately after filling, or if content was observed to ooze out near the joint, it was considered a leak. In the table, the sum of the leakage and shell breakage is shown as a leakage rate (%), and the shell breakage rate (%) is shown in the box. Note that 0°C and 25°C were selected as the test conditions, and after confirming that the entire test specimen had sufficiently reached that temperature, 50 tests were conducted for each. (d) Drop test After filling a metal container with the specified contents, drop the container at room temperature from a height of 90 cm in two directions: (i) with the bottom facing downwards, and (ii) with the joint facing downwards. We dropped 25 pieces each, and found out whether or not there were any broken shells, in fact 48 pieces.
After a period of time, the presence or absence of leakage was examined. For each case, the table shows the sum of the leakage and shell breakage as a leakage rate (%), and the shell breakage rate (%) is shown in the box. (E) Aging test at 50℃ for 3 months●Volume change The total volume of the container before filling was measured in advance, and the contents were filled with the contents, and after a period of time, the total volume was measured again for containers with no leakage. ,
The difference was defined as the volume change ΔV. Ten pieces of each were measured, and their arithmetic mean value was used as the result. ●Rate of leakage and broken shells A broken shell is one in which the upper body and the bottom body have separated, or one of them has been deformed and there is a gap at the joint. Also, cases in which the internal pressure at 25°C had decreased by 5% or more compared to immediately after filling, and cases in which some content was observed to ooze out near the joint, were considered to be leaks. in some cases,
The sum of the number of leaks and the number of broken shells out of 50 is the leakage rate (%)
The shell breakage rate (%) is shown inside the box. ●Metal elution After filling a metal container with a synthetic carbonated beverage and keeping it at a predetermined temperature and time, the amount of metal eluted was measured using atomic absorption spectrometry. Ten pieces of each were measured, and their arithmetic mean value was used as the result. Examples 1 to 10, Comparative Examples 1 to 5 A paint having the composition shown in Table 1 was applied to the inner and outer surfaces of an aluminum plate (3004 material H19 chromate treatment) with a material thickness of 0.23 mm at a total coating amount of 120 mg/dm ^{2 .} , 50
After coating and baking to achieve mg/dm ²
A disk with a diameter of 250 mm was punched out and formed by normal press working to produce an upper body having an inner diameter of 110.6 mm at the edge of the joint and a spout with a diameter of 30 mm in the center. On the other hand, a disk with a diameter of 250 mm was punched out from the same painted plate and formed by press working to produce a lower body with an outer diameter of 110.6 mm at the edge of the joint. Adhesive was applied as follows over the entire edge of this lower body to a width of about 5.5 mm on the outer surface and a width of about 1.5 mm on the inner surface. That is, the film thickness is a copolyester (consisting of 10 mol% polyethylene glycol with an average molecular weight of 800 as acid components, 80 mol% terephthalic acid, 25 mol% isophthalic acid, and 90 mol% 1,4-butanediol as glycol components) film.
A piece of 80μm and 7mm width is pasted around the entire circumference of the outer edge of the lower body, which has been heated with high frequency, so that it protrudes by about 1.5mm.Then, while the edge is heated with high frequency again, this protruding part is folded back with a roll to attach it to the inner surface. A lower body was prepared which was attached to the side and whose edges were covered with adhesive. The thus obtained upper body and the lower body coated with adhesive were fitted together, and the mating part was heated with high frequency to melt the adhesive, which was then cooled and solidified to fit the upper body and the lower body together. A metal container with a capacity of approximately 2 was prepared. While evaluating the joint strength of these metal containers, after filling with beer, the spout was tightly closed and
After being sterilized for several minutes, they were kept at 50°C and observed for changes in internal volume, leakage, and the presence or absence of wave bodies. In addition, for those filled with carbonated drinks, the amount of aluminum eluted was measured. Furthermore, a deining test and a drop test were conducted to observe the presence or absence of leakage and shell damage. Table 2 shows these results as the degree of polymerization of vinyl chloride resin, and the concentration of carboxyl groups and/or hydroxyl groups in the vinyl chloride copolymer, which was determined using the calibration curve method from the infrared spectral characteristic absorption of carboxyl groups or hydroxyl groups. Also shown.

【table】

【table】

[Table] Example 11 Bright tin-plated steel plate with a material thickness of 0.23 mm (T-1
Paint E2 (see Table 1 for composition) was applied to the inner and outer surfaces of the material, plating amount #50/50), with a total coating amount of 150.
mg/dm ² , 60 mg/dm ² , and then punched into a 94 mm disk and formed by normal press processing, with an inner diameter of 64.48 mm at the edge of the joint.
An upper body having a spout with a diameter of 25 mm in the center was manufactured using the following methods. On the other hand, a tin-plated steel plate with a material thickness of 0.30 mm is approximately 142 mm thick.
It is punched out to a diameter of , and then formed into a tip shape with an inner diameter of approximately 85 mm between a drawing punch and a drawing die. Next, this pot-shaped molded product was subjected to a re-drawing process, and then ironed using an ironing punch and die having a diameter of about 66.1 mm. The same paint E2 as the upper body is applied to this outer surface.
was coated with a mandrel coater to a coating amount of 60 mg/dm ² and then baked. Furthermore, the inner surface was spray-coated with epoxy urea paint to a coating amount of 150 mg/dm ² and baked. Later, a net-in process was performed to produce a lower body with an outer diameter of 64.40 mm at the circumferential edge. Next, adhesive was applied around the entire edge of the lower body to a width of about 4 mm on the outer surface and a width of about 2 mm on the inner surface as described below. i.e. copolyester (75 mol% terephthalic acid and isophthalic acid as acid components)
A film (consisting of 20 mol%, sebacic acid, 5 mol%, and 100 mol% of 1,4-butanediol as a glycol component), 80 μm thick and 6 mm wide, was applied around the entire circumference to the outer edge of the lower body, which had been preheated with high frequency. It was pasted so that it protruded by 2 mm, and then, while the edge was heated again with high frequency, this protruding portion was folded back with a roll and pasted on the inner side to produce a lower body whose edges were covered with adhesive. The upper body thus obtained and the lower body coated with adhesive are fitted together, the fitted part is heated with high frequency to melt the adhesive, and then cooled and solidified to form a bonded capacity of approximately A 500ml bottle-shaped metal container was created. After filling these metal containers with synthetic carbonated beverages, the spouts are tightly closed, and the temperature is heated to 42℃ using a can warmer.
In addition to sterilizing the product and conducting a time-lapse test at 50℃,
When the strength of the pin was evaluated by performing a drop test and a denting test at 0°C and 25°C, it was found that the performance was sufficiently satisfactory for practical use.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing separately an upper body and a lower body of a metal container of the present invention, and FIG. 2 is a metal container of the present invention formed by overlapping and joining the upper body and the lower body. 3 is an enlarged view of the cross section of the joint in FIG. 2, and FIG. 4 is a diagram showing an outline of the denting test, where 1 is for the lower body and 2 is for the upper body. body, 3 and 4 are open ends, 5 is a side seam, 6 is a thin side wall, 7 is a bottom, 9 is a top wall, 10 is a spout;
11 is a metal substrate, 12a and b are coating films, 13 is an adhesive, 14 is a cut edge of a metal material, and 15 is a coating layer.

Claims (1)

[Claims] 1 Based on solid content, (A) 10 to 80% by weight of vinyl chloride resin particles with a degree of polymerization of 800 to 4000, (B) 5 to 500 mmol/100 of carboxyl groups and/or hydroxyl groups.
(g) 10 to 80% by weight of a solvent-soluble vinyl chloride-vinyl acetate-carboxyl group- or hydroxyl group-containing vinyl unit copolymer contained in the concentration of the polymer and (C) reactive toward carboxyl groups and/or hydroxyl groups. The composition contains 2 to 30% by weight of a solvent-soluble thermosetting resin having the copolymer (B) and the thermosetting resin (C) in a continuous phase as a dispersion medium, in which the vinyl chloride An adhesive primer for metal containers, which is applied to metal and used for adhesion with a copolyester adhesive, characterized in that the resin particles (A) are present in the form of a dispersoid dispersed in the continuous phase.