JPS6111674B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the coating of container bodies using two or more coatings, at least the first of which is a crosslinked material in a solvent.

Containers made from stretched sheet metal into a thin-walled/cylindrical shape with one end closed are well known. By ironing the container, the container is passed through a mold to reduce its wall thickness and is subjected to stresses which can cause the surface coating on the container to fracture. Therefore, it is common practice for such containers to be coated after molding.

This coating can take the form of a base coat and a printed coat thereon. It is common practice to dry each coating in an oven to fully cure each coating before applying the next coating.

A feature of the present invention is that the first coating is applied to the container body and the coating is sufficiently dried to be able to receive a second coating thereon, but only partially cured; Provided is a method of coating a container body with at least two layers of coating, wherein the coating is applied to the container body over at least a portion of the first coating, and then the first and second coatings are fully cured. do.

As used herein, the term "cured" is used in reference to cross-linked coatings and indicates a state in which further cross-linking of the coating material is not possible; therefore, "partial cure" refers to further cross-linking of the coating material. It means a state in which there is room for action. The term "dry" is also used for solvent-containing coatings, indicating that the solvent has been removed.

In an embodiment of the method according to the invention, the first coating is a base coating material and the second coating is a printing ink. The composite layers of these coatings are further dried to a fully cured state.

Another feature of the invention is to provide an apparatus for drying or partially curing a coating on a container, the apparatus including a curing means for drying or partially curing the coating, and a curing means for drying or partially curing the coating on the container. and means for moving the container for exposure to the means.

One embodiment of the curing means includes a gas flame. The container moving means are arranged to effect mechanical, pneumatic or electrical movement of the container along a straight or curved path.

The invention will be described below with reference to various embodiments by way of illustration and with reference to the accompanying drawings.

In a typical manufacturing step for wall ironed cans in FIG. 1, the can is first coated with a base coating material and then passed through an oven where the coating is cured. The second coating is then applied to the top surface of the base coating and the can is then coated with the second coating before any subsequent coatings are applied or any additional operations are performed as desired. Passed through a second oven for curing.

A typical gas-fired furnace for such known drying operations includes a thermally insulated tunnel of oblong cross-section. A chain with horizontal hooks, one for each can, passes through the furnace. Such furnaces have a large volume and require a considerable amount of energy to heat them. A typical drying cycle for can coating or painting requires about 2 minutes at 205°C, with the speed of the running line determining the time to raise and lower the temperature of the can in the oven for up to 6 minutes total. Such an extended drying operation yields a fully crosslinked and fully cured coating.

It has been found that the coating only needs to be dried or partially cured before applying other coatings to it.
In the method illustrated in the illustration of FIG. 2, a first coating is applied to the can and then dried or cured to create a sufficiently stable surface to allow attachment of a second coating.

The drying or curing action of the first coating is induced by the heat from the gas flame. The second coating may be dried or cured whether or not it receives another coating (as shown in solid lines), or alternatively a combination of the first and second coatings may be combined with both coatings. It can also be heated (as shown by the dashed line) to completely dry or harden.

Suitable conditions for achieving the desired degree of drying or curing depend on the properties of the coating material used (eg, basecoat, printing ink, or varnish or lacquer).

However, by using the method of FIG. 2, the required drying or curing time can be reduced from the minutes required with prior art methods to the seconds. With suitable coating materials, it takes less than 10 seconds.

The flame intensity used to produce the desired degree of drying or partial curing is high and the coated surface of the can is passed rapidly in front of the flame to prevent scorching or ignition of the coating.

Ideally, less heat is required than for prior art methods where the entire can is heated, since it is necessary to heat the coating and not the can.

EXAMPLE The principles of the invention can be illustrated by a simple device (not shown) in which a rotating mandrel or fixed hanger to which a container can be attached is used to expose the container in front of a gas combustor. Wet base coating (e.g. acrylic coating material No. W758 marketed in the United Kingdom by Ault and Wiborg Ltd)
The can is attached to a mandrel and rotated at a high speed, for example 900 rpm. The combustor flame array is allowed to touch the surface of the underlying coating for 1.3 seconds to dry or partially cure the coating. The coating formed in this way is coated with placemark ink (e.g. Edward's).
Edward Marsden Limited
Ltd) in the red printing ink No. GP25) marketed in the United Kingdom. The following coatings could be accepted.

Figures 3A, 3B, 4A, 4B, 5A and 5B are devices illustrating a non-limiting manner in which the coating on the can body may be exposed to flame.

In FIG. 3A, the device is capable of transporting can transport mandrels (as shown at 1) each carried on an arm 2 of a chain link 3. The linear motion of the chain 4 moves the can transport mandrel along and above the combustor 5. A guide 6 is provided to control the spacing of the can transport mandrel above the rod combustor, as shown clearly in FIG. 3B.

Each can transport mandrel 1 is rotated about its axis substantially parallel to the rod-shaped combustor 5. This rotational movement is obtained from a stationary rack 7 and a pinion such as 8 attached to the shaft 9 of each arm 2. A suitable bevel gear mounted on shaft 9 is used to rotate each can transport mandrel 1. The temperature at which the coating is heated is determined by the characteristics of the flame emanating from the combustor 5 and the contact time. The contact time is determined by the linear velocity of the can transport mandrel passing over the combustor or the length of the combustor.
or controlled by any combination of these factors.

In FIGS. 4A and 4B, can bodies 10 are shown being transported on a conveyor 12. In FIGS. Such conveyors are known in which cans are conveyed by air emanating from an elongated orifice 11 above a high pressure chamber of the conveyor 12. This conveyor can be suitably adapted to transport each can not only along the conveyor, but also to rotate in front of the contact flame from the combustor 5, thereby making it possible to carry out the invention according to the invention as already mentioned. Conditions can be provided for the required degree of drying or partial curing. Aside from this,
Hot air can also be used to dry or partially cure the coating as well as transport the can. The degree of cure is controlled by adjusting the temperature of the flame or hot air and the time the coating is exposed to this heat.

In FIG. 5A, a rotating device is shown in which a plurality of axles, such as the two axles represented here by 14, are attached to a rotating hub 15 attached to an axle 16 driven by known devices. Rotatably mounted. As the hub rotates, as shown in FIG. 5B, each mandrel passes through the feed position F, where the coated can bodies are delivered. Since the hub 15 continues to rotate, each can is therefore carried and passed;
At the same time, it rotates around its own axis at the front of the combustor, which has a plurality of flame rods 5. In FIG. 5B, the combustor includes a main feed pipe 17 through which the combustor flame rods, such as those indicated at 5, are fed.

This provides certain advantages in the cyclical heating and cooling applied to the coating applied to the can as the can passes sequentially from flame bar to flame bar. As mentioned above, factors such as temperature and exposure time are controlled to obtain partial cure.

After being heated to effect the desired degree of drying or partial curing of the coating, the can body is suitably conveyed through a cooling station where hot and cold air is blown from nozzles 18 towards the surface of the can body.

Each can is then removed from the mandrel and placed in position E.
It is then ejected from the machine, applied with one or more additional coatings, and dried or fully cured as described for the method of FIG.

In FIG. 5A, each axle 14 has an axle 29 attached to a hub 15 and carrying a pinion 28 cooperating with a gear 19 attached to the machine frame 20.
Since the hub 15 rotates,
Each mandrel rotates continuously to rotationally expose the entire surface coverage of each can carried on the mandrel to the combustor. A flue 21 is provided to exhaust combustion gases out of the machine if necessary.

The coating material used can be any of the known materials, or alternatively a large amount of lubricant may be applied to the coating to give it a high degree of lubricity in order to facilitate the subsequent transport of the can. It can also be modified by addition.

When highly lubricious base coatings are dried by prior art methods, the lubricant remaining on the surface after the relatively low temperature curing action interferes with the adhesion of other coatings. However, if you use the method shown in Figure 2,
Any residual lubricant in or near the surface of the base coating is removed from and removed from the surface.

Although the invention has been described using a rotating mandrel format for transporting coated articles, known hangers for transporting articles in front of a flame may be used where rotation is not necessarily required. Chains can also be used.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a coating method according to the prior art; FIG. 2 is a first diagram of an embodiment of the present invention.
Figure 3A is a side view of a first apparatus arranged for carrying out the method of Figure 2, the covered container being conveyed along a straight path; Figure 3B is Figure 3A; FIG. 4A is a side view of a second device according to the invention, the coated container being conveyed along a straight path; FIG. 4B is a side view of the second device according to the invention; 4A is an end view of the device taken along the line B-B' in FIG. 5A; FIG. 5A is a side view of a third device according to the invention in which the coated container is conveyed along a curved path; FIG. 5B The figure shows line C- in Figure 5A.
Front view of the device taken along C'. 1st
Fig. 1st coating - 1st drying chamber for curing the 1st coating, 2nd
Coating - Second drying chamber for curing the second coating, Figure 2 (from above)

[Table] 1...Can transport mandrel, 2...Arm, 3...Chain link, 4...Chain, 5...Combustor, 6...
Guide, 7... Stationary rack, 8... Pinion, 9...
...shaft, 10...can body, 11...orifice, 12
... Conveyor, 14 ... Mandrel, 15 ... Rotating hub, 16 ... Shaft, 17 ... Main supply pipe, 18 ...
... Nozzle, 19 ... Gear, 20 ... Machine frame, 21 ... Flue, 28 ... Pinion, 29 ...
shaft.

Claims (1)

[Claims] 1. Applying a first coating made of an organic coating material to the container body, and curing the first coating to a degree that is sufficient to apply a second coating but only partially. applying a second coating made of an organic coating material to the only partially cured first coating; A method of coating a container body with two or more coatings, which includes a step of completely curing the two coatings. 2. The method of claim 1, wherein the first coating is exposed to the gas flame for a time period of seconds rather than minutes. 3. The method of claim 2, wherein the flames are simultaneously applied to the first coating for less than 10 seconds. 4. A method according to any one of the preceding claims, in which the container body is rotated to expose the entire container body to the flame of a fixed combustor. 5. Any of the preceding claims, wherein the first coating includes a lubricant, at least a portion of which is removed from the surface of the first coating by the flame, and the second coating also includes a lubricant. The method described in Section 1. 6. The method of claim 1, wherein the first coating is a base coating and the second coating is a printing ink. 7. A method according to any one of the claims, wherein the first coating and the second coating are fully cured after the second coating is applied, and then the next coating is applied. 8 A first coating means for applying a first coating to the container body, a flame source, and a flame to be applied directly to partially cure the first coating; a second coating means for applying a second coating to the only partially cured first coating; and simultaneously applying the first coating and the second coating. Apparatus for coating container bodies with two or more layers of coating having means for complete curing. 9. Apparatus according to claim 8, wherein the holding means has a rotatable can transport mandrel and means for driving said rotating can transport mandrel. 10. Apparatus according to claim 9, in which the can transport mandrel is held on the chain link and is mounted on a shaft in the chain link and driven in rotation by a pinion cooperating with a stationary rack. 11 The flame source consists of a plurality of combustors arranged adjacent to each other, and the holding means includes one or more shafts passing through the combustors, and a can rotatably assembled to the shafts. Claim 8, comprising a hub assembled for rotation with a transport mandrel, and means for imparting rotation to the can transport mandrel.
The equipment described in section. 12. The apparatus of claim 11, wherein the combustors are spaced apart. 13. The apparatus of claim 8, wherein the holding means is an air conveyor and has a combustor extending along the air conveyor and directing the flame from there into the container body.