JPS6334791B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for coating a parison, and more particularly to an apparatus for forming a gas barrier coating on the inner surface of a plastic bottomed parison.

Rather than bottomed plastic parisons, bottles formed by stretch molding or stretch-blow molding, such as polyethylene terephthalate bottles, have excellent container properties such as gas barrier properties, transparency, and impact resistance, and have recently been used for various contents. It is being put into practical use for storage. However, when filling and sealing contents containing pressurized carbon dioxide such as beer or carbonated drinks,
Over time, some carbon dioxide gas is lost through the walls, while some oxygen is likely to enter through the walls, spoiling the flavor of the contents.

As a countermeasure, a method has been proposed to form a coating film with excellent barrier properties against carbon dioxide gas and oxygen, such as a coating film made of vinylidene chloride copolymer, on the inner and/or outer surface of the bottle, but this method depends on the shape of the bottle. In some cases (for example, when embossing or beads are formed), there may be uncoated areas or very thin areas of the coating, resulting in insufficient barrier properties for the bottle as a whole or poor adhesion of the coating. This is not satisfactory, and the problem arises that the coating film tends to swell and crack as time passes after filling and sealing.

When forming the above-mentioned coating film on a parison, the shape of the parison is generally monotonous, and the adhesion is improved by heating to, for example, close to 100°C (in the case of polyethylene terephthalate) before blow molding or stretch-blow molding. Although it is presumed that this is due to the improvement in the above, the above problem is unlikely to occur.

The technique for forming a paint film on the inner surface of a bottomed parison is to invert the parison so that the opening faces downward, insert a nozzle inside the parison, spray the paint, and then leave it for a while to adhere to the inner surface. A method has been proposed in which the paint is discharged by flowing down and then heated air is blown into the inside of the parison to dry the film of paint remaining on the inner surface. However, in this case, the paint that has flowed down is near the mouth, especially on the end surface of the mouth.
It remains in a wavy shape, that is, thick and thin parts, and even after drying, it causes unevenness near the mouth, especially on the end surface of the mouth, which tends to impair the sealing performance after sealing the cap. This causes a problem.

It is an object of the present invention to solve the problems of the prior art described above.

To achieve the above object, the present invention provides an apparatus for forming a gas barrier coating on the inner surface of a plastic bottomed parison for forming a blow-molded or stretch-blow-molded bottle. , having a hole through which the body of the parison is inserted;
a holder that engages with a support ring of the parison and holds the parison with the mouth of the parison facing upward; a water holder whose dry coating film has gas barrier properties; a filling nozzle for filling emulsion paint at least up to the level of the support ring; a first discharge nozzle for discharging most of the filled paint; a second discharge nozzle for discharging the paint remaining at the bottom of the parison after the discharge; A discharge nozzle, a heating air nozzle for drying a film of paint remaining on the inner surface of the parison, and a device for circulating and transporting the holder so that the mouth of the parison is located directly below each nozzle. The present invention provides an apparatus for coating a plastic parison with a coating film.

The present invention will be described below with reference to the drawings which are examples.

In the coating film coating apparatus 1 shown in FIG. 1, 2 is a parison charging station, 3 is a paint filling station, 4 is a primary paint discharge station, 5 is a secondary paint discharge station, 6 is a primary paint film drying station, 7 is a secondary paint film drying station, 8
is the parison delivery station.

Multiple pieces (5 in the figure) were transported in the direction of arrow A.
At the charging station 2, the parisons 9 are simultaneously loaded from above into a holder 10 having a rectangular planar shape. The holder 10 is shown in Figures 2 and 3.
As shown in Figures 4 and 5, holes 11 are attached to a main part 10a made of a rectangular metal (for example, stainless steel) through holes formed at equal intervals along the longitudinal direction. plastics (e.g. fluoropolymers) with
A holding ring body 10b is provided.

The body part 15 of the parison 9 is inserted into the hole 11 with the mouth part 12 of the parison 9 facing upward, that is, in an upright position, and the support ring 14 of the parison 9 is inserted into the holding ring 1.
The parison 9 is held in the holder 10 by engaging the upper surface 10b ₁ of the holder 0b (see FIG. 5). The reason why the plastic holding ring 10b is provided is to prevent the outer surface of the parison 9 from coming into contact with hard metal during loading and unloading, and to prevent it from being damaged. For example, in case 2), if the paint is highly corrosive, the paint 30 should spill out of the parison opening 12 from the filling nozzle 28, etc. (described later) (although it is normally designed to prevent it from spilling).
This is to prevent the holder 10 from being corroded.

As shown in FIG. 3, a protrusion 10a ₁ is formed at the top of the short side end of the holder 10, and the protrusion 10a ₁ is formed on the top surface of the end of the frame 18 extending in the short side direction of the holder 10. recess 1 with a shape corresponding to
By engaging with 8a, the holder 10 is held, and by sliding the protrusion _10a1 along the recess 18a, the holder 10 is moved in the direction of its short side.

Further, as shown in FIG. 2, a recess 10a ₂ having a U-shaped cross section is formed on one long side end surface of the holder 10.
A convex portion 10a ₃ having a shape corresponding to the concave portion 10a ₂ is formed on the end face of the other long side, and adjacent holders 10 are engaged with each other through their respective concave portions 10a ₂ and convex portions 10a ₃ , and They are able to slide against each other. Further, among the frames 19 extending along the long side of the holder 10, a convex portion 19a ₁ having a shape corresponding to the concave portion 10a 2 is formed on the inner end surface of the frame 19a on the side of the concave portion 10a ₂ , and a convex portion 19 a ₁ having a shape corresponding to the concave portion 10 a ₂ is formed. side frame 1
A recess 19b ₁ having a shape corresponding to the protrusion 10a ₃ is formed on the inner end surface of the holder 9b, and the holder 10 is held by the frame 19 and can slide along the frame 19. .

The holder 10 is transferred to each station using air cylinders 20a, 20b, 20d, 20e,
20f, 20g, 20h, 20i and a hydraulic cylinder 20c (only the cylinder 20c is hydraulically operated in order to prevent the filled paint from spilling from the parison, which will be described later). , push the holding ring 10b closest to the plunger one pitch at a time (the length of the short side of the holder 10 if it is along the frame 18, the length of the long side of the holder 10 if it is along the frame 19). , frames 18, 19
Each holder 10 is moved intermittently while sliding along the
This is done by sending.

That is, in FIG. 1, charging station 2
After loading the parison 9 into the holder 10, when the holder 10 is moved one pitch in the direction of arrow B by the air cylinder 20a, the station 22a facing the air cylinder 20b is moved.
Since the holder 10 is a vacant space, the three holders 10 downstream of the holder 10 are also transferred one pitch in the direction of arrow B, and the holder 10 is placed in the station 22a.
enters. At the same time, the hydraulic cylinder 20c and the air cylinders 20e and 20g operate, and the holder 10 moves one pitch in the directions of arrows D, F and H, respectively, to the vacant stations 22b and 22c.
The holder 10 is inserted into 22d.

Next, air cylinders 20b, 20d, 20f,
When operating 20h and 20i, station 2
The holders 10 placed in the holders 2a, 22b, 22c, and 22d are moved by one pitch in the directions of arrows C, E, and G, respectively, to the stations 23a, 23b, 23c, and 23d, which were empty spaces from the previous transfer, and the charging stations. Enter station 2. This process is repeated at regular intervals, and each holder 10 is transferred from the charging station 2 to the filling, discharging, drying stations 3, 4,
5, 6, and 7 to form a coating film on the inner surface, the parison 9 is sent to a delivery station 8, where it is pulled up from a holder 10 by a lifting device (not shown) and moved in the direction of arrow K. It is transported and sent to the next process.

The parison 9 is made of saturated polyester such as polyethylene terephthalate, polypropylene, etc., and is usually formed by injection molding. 12 is a mouth portion, 13 is a screw portion, and 14 is a support ring, which are formed into a bottle (not shown) by blow molding or stretch-blow molding.
It retains its original shape and thickness even after being formed. Note that the support ring 14 engages with a support (not shown) when plugging the cap into the threaded portion 13.
This is usually provided in order to prevent the axial force caused by the stopper from acting on the relatively weak body and bottom of the bottle.

The substantially depending portion of the parison 9 below the support ring 14, ie the body 15, constitutes primarily the relatively thin shoulder and body of the bottle formed. The bottom 16 of the parison 9 will also primarily be the bottom of the bottle formed. Therefore, in order to improve the gas barrier properties of the formed bottle,
The inner surfaces (and the outer surfaces, if necessary) of the body 15 and bottom 16 of the parison 9 may be coated with a gas barrier coating.

Since the portion above the support ring 14 remains thick (for example, about 1 to 4 mm) even after the bottle is formed, it does not necessarily need to be coated with a gas barrier coating. On the contrary, during this coating operation, the paint often adheres non-uniformly to the end surface 12a of the mouth portion 12, which tends to result in poor sealing as described above, so it is preferable not to cover the above-mentioned upper portion.

In the paint filling station 3 3a, five filling devices 24 shown in FIG. 5 are arranged in one row.

The filling device 24 includes a valve mechanism 25 having a flexible tube 25a, a filling nozzle 28 located below the valve mechanism 25 and hanging down, and a floodlight 29.
A photoelectric filling level detection device 29 having a light receiver 29a and a light receiver 29b is provided.

The flexible tube 25a of the valve mechanism 25 is made of plastic or elastomer, preferably silicone rubber, so as not to be corroded even when the pH of the water emulsion paint 30 (hereinafter referred to as paint) passing through it is low (for example, PH2). It is made of Teflon or the like, and is attached to a support (not shown).

A cylindrical fixed body 31 is provided on one side of the portion 25a ₁ of the flexible tube 25a, and a presser 32 is provided opposite the fixed body 31 so as to be able to pinch the portion 25a ₁ . The presser 32 is connected to a piston rod of an air cylinder (not shown), and is configured to reciprocate in the horizontal direction by the operation of the air cylinder.

When the presser 32 moves to the right (hereinafter this state is referred to as pinch-on) until the opposing inner surfaces of the flexible tube portion _25a1 come into contact (the state shown in FIG. 5), the valve mechanism 25 is closed, and conversely, when the presser 32 moves to the left and the portion _25a1 in contact with the presser 32 becomes almost straight (hereinafter this state is referred to as pinch-off), the valve closes. The mechanism 25 is fully opened. The valve mechanism 25 is normally pinched on.

The filling nozzle 28 is made of a tube made of hard-to-flex plastic or stainless steel, and its lower end 28a is bent so that the upper tip _28a1 of the lower end 28a is in close contact with the inner surface 9a of the parison 9 during filling. 24, and thus a filling nozzle 28 is arranged relative to the filling station 3a.

The inner diameter of the nozzle 28 and the flexible tube 25a and the length from the portion 25a ₁ to the lower tip 28a ₂ of the lower end 28a of the nozzle 28 are
In the on state, the paint 30 inside is determined not to fall freely (due to surface tension). Therefore, the above dimensions are controlled by the specific gravity, viscosity, surface tension, etc. of the paint, but usually the above conditions are satisfied when the inner diameter is about 6 mm or less and the length is about 300 mm or less. In order to increase the filling speed and increase productivity, it is desirable that the inner diameter be as large as possible (at least 1 mm or more) within the range that satisfies the above conditions. Further, the length is desirably at least 100 mm in order to operate the valve mechanism 25 and enable charging of the parison to a predetermined position.

A photoelectric filling level detection device 29 is also mounted on the aforementioned support (not shown), and its optical axis 29
c is located at a slightly lower level than the lower tip 28a ₂ of the nozzle. During filling, when the light receiver is receiving light, the valve mechanism 25 is in a pinch-off state, but when the light receiver 29b is blocked, the aforementioned air cylinder is activated by a control mechanism (not shown). , the presser foot 32 immediately moves to the right,
The valve mechanism 25 is configured to pinch on.

Filling is performed as follows.

With the above-mentioned support in the raised position, each parison 9 is transferred directly below each filling nozzle 28 and stopped. Immediately, the support lowers and the filling device 24 reaches the optical axis 29 of the filling level detection device 29.
c reaches a predetermined level at which the paint 30 should be filled (in the case of FIG. 5, a level slightly lower than the lowest end of the threaded portion 13). Since the parison 9 is transparent, the light receiver 29b is not blocked from light.

Immediately thereafter, the valve mechanism 25 pinches off, and the dried coating film becomes a water emulsion paint 30 having gas (oxygen, nitrogen, carbon dioxide, etc.) barrier properties.
Filling is carried out. This type of paint includes copolymers of vinylidene chloride monomers and acrylic or methacrylic monomers, or copolymers of vinylidene chloride monomers, acrylic or methacrylic monomers, and ethylene monomers. Aqueous latexes of copolymers made of saturated monomers are preferably used. As the emulsifier, from the viewpoint of food hygiene, it is desirable to add a food-hygienically safe type (this type of emulsifier is generally poor in emulsifiers) as small as possible within the range that allows emulsification.

During filling, as shown in FIG. 5, since the upper tip _28a1 of the nozzle is almost in contact with the inner surface 9a of the parison 9, the paint 30 flows down along the inner surface 9a, causing almost no foaming. do not have. and paint 30
When the paint 30 is filled to a predetermined level, that is, to the level of the optical axis 29c, since the paint 30 is milky white,
The light receiver 29b is blocked, the valve mechanism 25 is pinched on, and the paint 30 stops flowing down. The inner diameter and length of the nozzle 28 are determined as described above, and since there is no shock in the valve mechanism 25 when opening and closing (other types of valves, such as rotary valves, are prone to shock), pinch-on Afterwards, there is no risk that the paint 30 in the nozzle 28 will fall.

Also, since the lower tip _28a2 of the nozzle is slightly above the optical axis 29c, and therefore above the filling level,
The nozzle 28 is not immersed in the filled paint. Therefore, the problem that occurs when the nozzle is immersed, such as the paint adhering to the outer surface of the nozzle falling off during transportation of the parison 9 and adhering to the opening 12 of the parison, which impairs the sealing performance, is unlikely to occur. Further, there is no risk that the tip of the nozzle 28 will directly contact the mouth portion 12 and stain the vicinity of the mouth portion 12 with paint.

Subsequently, the filling device 24 is raised to its original position. Next, the parison 9 is transferred to the primary paint discharge station 4. Note that at the upstream station 3a of the filling station 3, the parison 9 may be filled to approximately half of the predetermined filling amount, and at the downstream station 3b, the parison 9 may be filled to a predetermined level.

The primary paint discharge device 34 for discharging most of the paint filled in the parison 9 is the filling device 2.
4, a pinch-on and pinch-off type valve mechanism (not shown), a primary discharge nozzle 35 (not shown) located below and depending from the valve mechanism; 6th
), a closing device 36 (FIG. 6) that closes the opening 12 of the parison 9, and an inlet hole 37 provided in the closing device 36 to supply pressurized air 38 to the parison 9.
A pressurized air inlet device (not shown) is provided for injecting the air into the air.

The primary discharge nozzle 35 is made of a tube made of hard-to-flex plastic or stainless steel.
5 and the inner diameter of the aforementioned flexible tube and the pinch-on portion of the valve mechanism to the discharge nozzle 35.
The length to the lower end surface 35a is determined so that the paint 30 that has entered the inside does not fall freely in the pinch-on state.

The closure device 36 is made of an elastic material (for example, silicone rubber) and includes an annular packing 36a that can be engaged with the mouth end surface 12a of the parison 9.
A through hole through which the discharge nozzle 35 can be inserted is provided in the center of the packing 36a.
A through-hole portion between 5 and packing 36a serves as an inlet hole 37 for pressurized air 38. In the case of FIG. 1, five primary paint discharge devices 34 as described above are arranged along the longitudinal direction of the primary discharge station 4 so as to be located directly above the stopped parison 9.

When the parison 9 is transferred to the primary paint discharge station 4, the discharge nozzle 35 and the closing device 36 are in the raised position. When the parison 9 stops, the closing device 36 lowers and its packing 36
The opening 12 of the parison is sealed by a (by being pressed by a spring not shown), and at the same time the primary discharge nozzle 35 is also lowered to a predetermined level where its lower end surface 35a approaches the inner surface of the bottom 16. reach Immediately based on a signal from a limit switch (not shown), the exhaust nozzle 35 is stopped, the valve mechanism is pinched off, and the pressurized air inlet valve is opened to allow pressurized air 38 to flow through the inlet hole 37. It is fed into the parison 9. Therefore, most of the paint 30 in the parison 9 is pushed up and discharged through the discharge nozzle 35, sent to a paint tank (not shown) that supplies the paint 30 to the filling device 24, and collected.

When the upper surface 30b of the paint 30 reaches almost the lower end surface 35a of the discharge nozzle 35, the valve of the pressurized air supply device closes, the supply of pressurized air stops, and The valve mechanism also pinches on. For example, a timer signal is used as the signal. This is because by keeping the filling amount, pressurized air pressure, and valve opening constant, the level of the upper surface 30b of the paint becomes a function of the pressurized air supply time.

Subsequently the discharge nozzle 35 and the closing device 36
is returned to its original position above parison 9. The parison 9 is then transferred to the next secondary paint discharge station 5 while remaining upright, but the inner diameter and length of the primary discharge nozzle 35 are determined as described above.
In addition, since there is no shock in the valve mechanism when opening and closing (other types of valves, such as rotary valves, are prone to shock), the discharge nozzle 3
There is no risk that the paint inside the parison 5 will fall and adhere to the opening 12 of the parison 9 or the holder 10. Therefore 1
Since the paint 30 is always contained inside the secondary discharge nozzle 35, there is no fear that the paint will solidify upon contact with air inside, thereby clogging the primary discharge nozzle 35. Additionally, water emulsion paints (especially when the amount of emulsifier added is small) generally tend to coagulate when shearing force is applied, but in the case of the valve mechanism of this embodiment, almost no shearing force acts. Therefore, it solidifies on the sliding surfaces such as rotary valves, etc.
There is no risk that the valve will stop working.

At the secondary paint discharge station 5, after the primary discharge, a small amount of paint 30 that flows down the inner surface 15a of the body 15 of the parison 9 and accumulates on the bottom 16 is discharged.
While keeping the parison 9 upright, remove the secondary paint discharge device 4.
Discharge by 0.

As shown in FIG. 7, the secondary paint discharge device 40 includes a secondary paint discharge nozzle 44 made of a double pipe having an outer cylinder 42 and an inner cylinder 43, and an outer cylinder 42 and an inner cylinder of the secondary discharge nozzle 44. A water supply pipe 47 for supplying water 46 from above and a vacuum mechanism (for example, a vacuum pump), not shown, connected to the inner cylinder 43 are provided in the gap 45 between them.

The lower end of the inner cylinder 43 is an opening 43a,
An opening 42a having an inner diameter approximately equal to the opening 43a is also formed at the lower end of the outer cylinder 42. The lower end 42b of the outer cylinder 42 is narrowed inwardly and downwardly into an arcuate cross-section so as to face the lower end surface 43b of the inner cylinder 43, which has an arcuate cross-section, with a gap 45 in between. The outer diameter of the outer cylinder 42 is set to be slightly smaller than the inner diameter of the parison 9. Note that the outer cylinder 42 and the inner cylinder 4
A plurality of (for example, three) spacers 48 are provided at the lower part of the secondary discharge nozzle 44 to hold the spacers 3 coaxially and to keep the radial width of the gap 45 constant along the circumferential direction. There is.

The water supply pipe 47 also has an outer pipe 49 and an inner pipe 50.
It has a double pipe structure, and the lower part of the tubular water supply hole 51 between the outer pipe 49 and the inner pipe 50 is connected to the upper end of the gap part 45, and the upper part of the water supply hole 51 is connected to the upper end of the water supply hole 51 through a conduit 52.
Connect to a water supply source (for example, a water tank or water pipe) not shown. When a valve (not shown) provided in the conduit 52 is opened, water 46 flows down through the water supply source, the conduit 52, the water supply hole 51, and the gap 45 to the lower end 45a of the gap.

The inner tube 50 is connected to the upper end of the inner tube 43 and is in contact with a vacuum mechanism (not shown) via the conduit 53. When a valve (not shown) provided in the conduit 53 is opened, the fluid (water, paint,
It is constructed so that air (such as air) can be sucked up.

In the case of FIG. 7, the water supply pipe 47 is connected to the holder 10.
One water supply pipe 47 extends in the long side direction, and five secondary discharge nozzles 44 are installed at positions corresponding to each hole 11 of the stopped holder 10, that is, to each stopped parison 9. There is.

When the parison 9 is transferred to the secondary ejection station 5, the secondary ejection device 40 is in the raised position. When each parison 9 stops directly below each secondary discharge nozzle 44, the secondary discharge nozzle 44 immediately descends to a position where the lower end 42b of the outer cylinder approaches the inner surface of the bottom 16 of the parison, as shown in FIG. do. The valve in conduit 53 is then opened, and immediately the valve in conduit 52 is also opened. Then, the paint 30 remaining on the bottom 16 is sucked up through the cylinder 43 and discharged together with the water 46 flowing down through the gap 45 and flowing out from the lower end 45a of the gap 45. After the first discharge is completed, the secondary discharge device 40
The time until the next discharge starts is preferably about 15 to 30 seconds.

After the secondary discharge is completed, the valve closes and the secondary discharge nozzle 44 rises, but the inner surface of the inner cylinder 43 is filled with water 4.
6, the inner cylinder 43 is coated with paint 30.
There is no risk of it becoming clogged. Also, the paint 30 from the inner cylinder 43
There is no risk that the parison 9 may fall and stain the opening 12, etc. of the parison 9 during transport. Note that the paint 30 discharged together with the water 46 as described above is discarded and is not reused.

In this manner, the paint film 30a having a relatively uniform thickness is formed along the inner surfaces of the body 15 and bottom 16 of the parison 9.

It is necessary to sufficiently discharge the residual paint to form a paint film with a substantially uniform thickness on the inner surface of the parison 9 from the viewpoint of shortening the drying time described later and maintaining the quality of the product.

Next, the parison 9 is transferred to the primary paint film drying station 6 while remaining erect.

As shown in FIG. 8, the preliminary paint film drying device 6
In the case of this embodiment, 1 indicates five hanging heating air nozzles 62a, 62 arranged in a straight line at intervals equal to one pitch in the short side direction of the holder 10.
b, 62c, 62d and 62e.
The upper end of each air nozzle is connected to a heated air supply pipe 63, and the heated air supply pipe 63 is connected to a heated air gap (not shown) via a conduit 64 and a valve (not shown).

Each air nozzle becomes shorter from the upstream side to the downstream side. That is, each air nozzle 62
a, 62b, 62c, 62d, and 62e become shorter in the order of air nozzle 62 on the most upstream end side.
The difference between the level of the lower end 62a ₁ of a and the lower end 62e ₁ of the most downstream blowing nozzle 62e is the height from the lowest point of the inner surface of the bottom 16 of the parison 9 to the upper end 30a ₁ of the paint film 30a. determined to be approximately equal.

Each air nozzle 62a, 62b, 62c, 62
d and 62e are disposed directly above the stopping position of each parison 9 in the primary paint drying station 6, and lined up coaxially with each parison 9 in the direction of arrow D, with the air nozzle 62a being on the most upstream side. ing. In the embodiment shown in FIG. 1, five primary paint film drying devices 61 are provided in parallel.

When the parison 9 held and transferred by the holder 10 stops, the heated air supply pipe 63 is lowered until the lower end 62a ₁ of the longest air nozzle 62a approaches the inner surface of the bottom 16 of the parison, and each air nozzle 62a, . . . , 62e are simultaneously inserted into the corresponding parisons. At that time, the lower end 62e ₁ of the shortest air nozzle 62e is connected to the upper end 3 of the paint film 30a.
Located at a level near _0a1 . Immediately opening the valve draws heated air 65 into each parison 9.

The temperature of the heated air 65 during primary drying is desirably approximately the boiling point of water or slightly higher than that, i.e., approximately 100 to 110°C, and the air volume is relatively small (for example, when the inner diameter is 20 mm and the height is approximately For a 100mm parison, approximately 5-10/min).

Parison 9 on the most upstream side, completely unheated until then.
(Into which the air nozzle 62a has been inserted), the vicinity of the inner surface of the bottom 16 is rapidly heated, and the paint film 30a in this area is formed into a pre-dried film 30a' that has lost its fluidity.

The second parison 9 from the upstream side (air nozzle 6
2b was inserted, the air nozzle 62a was inserted at the most upstream side during the previous heated air blowing, and the previously formed pre-dried film 30a' is located near the inner surface of the bottom 16 of the air nozzle 62a. is formed in the lower part of the body 15 (near the lower end 62b1 of the air nozzle 62b) which is slightly higher than the inner surface of the bottom part 16 where no film was formed last time by blowing heated air _this time. ) is coated with a film. Similarly, the parison 9 on the most downstream side is coated with the paint film 3 this time.
The vicinity of the upper end _30a1 of 0a is heated to form the entire paint film 30a to form a pre-dried film 30a'. That is, the parison 9 moves along the primary drying device 61 multiple times (5 times in this example) one pitch at a time, and each time it stops, the heated air 65 is applied to the inner surface of the body 15 in the order from below to above. By spraying, a paint film 30a is formed over the entire height. The time for one heating is usually about 5 to 10 seconds.

As described above, since the parison is heated and pre-dried in order from the bottom 16 side upward, the unformed paint film 30a flows down by the time the pre-drying is completed, and the pre-dried film near the inner surface of the bottom 30a' is particularly thick, or the pre-dried film 30 in the upper part of the body 15
A pre-dried film 30a' having a substantially uniform thickness throughout is formed without a' becoming particularly thin. The reason why the air volume is relatively small during pre-drying is to prevent deterioration, deformation, etc. of the parison 9 due to a rise in temperature since the temperature of the heated air 65 is relatively high.

In the above example, the primary drying, or pre-drying, was carried out five times from the bottom to the top using five heating air nozzles of different lengths, but the heating air nozzles were aligned in the direction of arrow D. Using five air nozzles of the same length, insert these air nozzles into the parison until their lower ends reach the level near the inner surface of the bottom of the parison, then blow heated air while raising the air nozzles to form a paint film. It may be pre-dried over its entire height. However, the method shown in FIG. 8 is mechanically simpler.

Pre-dried film 30 formed as above
Although a' has been formed into a film, it also contains water, and contains most of the water in the paint film 30a. Therefore, next, complete drying to completely remove this moisture is performed at the secondary paint film drying station 7 using the secondary heating air nozzle 72. A large number of secondary air nozzles 72 are disposed directly above the stopping position of each parison 9 of the secondary drying station 7 so as to be movable up and down coaxially with each parison 9.

As shown in FIG. 9, this complete drying is carried out when the parison 9 is held upright by the holder 10 and stopped, and the secondary heating air nozzle 72
at the upper part of the parison 9, preferably at its lower end 7
2a is inserted into the parison 9 so that it is located near the upper end 30a ₁ ' of the pre-dried membrane 30a', that is, the upper end 30a ₁ '' of the completely dried membrane 30a'', and heated air 75 is blown into the parison 9. It is carried out with In this case, the temperature of the heated air 75 is slightly lower than the boiling point of water, preferably about 90 to 95°C, and in order to increase the drying speed, the air volume is relatively large (for example,
For a parison of 20mm and a height of about 100mm, about 30-50
/ minute). Total blowing time is typically about 30-80 seconds.

The reason for keeping the temperature of the heated air 75 slightly lower than the boiling point of water is to keep it within a range that does not cause foaming of the coating film.
This is to increase the drying speed as much as possible. 2
The reason why the secondary heating air nozzle 72 is inserted relatively shallowly into the parison 9 is to prevent local heating.

In the manner described above, a parison 9 having a completely dried coating film 30a'' having gas barrier properties formed on its inner surface can be obtained.

Although the blowing time in this case is long, each air nozzle 72 is connected to each parison each time each parison 9, which is intermittently transferred one after another by arranging a large number of air nozzles 72 at regular pitch intervals as described above, stops. By simultaneously inserting and blowing heated air, the blowing time for each insertion can be shortened, and consistency in parison transfer with the pre-drying process can be maintained.

The thickness of the completely dried coating film 10a'' obtained by the one-step operation of filling, discharging, and drying described above is usually about 10
~20μm, so if you want to obtain a thicker coating, install a similar device in one or two stages above the coating device 1 in Figure 1, that is, create a coating device with a two- or three-story structure. Then, the parison 9 may be sequentially moved to the first, second, and third floors, and the above-mentioned covering operation may be repeated.

As described above, the gas barrier coating film 30
A bottle with improved gas barrier properties can be obtained by heating the parison 9 coated with a'' to a predetermined temperature and then blow molding or biaxial stretching-blow molding.

According to the apparatus of the present invention, a dry paint film can be formed on the inner surface by filling and discharging the water emulsion paint and drying the remaining paint film while the plastic parison with a bottom is in an upright state. The level at which the film is formed can be freely determined, and therefore a plastic hollow body with excellent sealing and gas barrier properties can be produced without coating on or near the end face of the mouth, and the paint can be recovered and reused. It has the effect of being able to.

[Brief explanation of drawings]

FIG. 1 is an explanatory plan view of an apparatus that is an embodiment of the present invention, FIG. 2 is a longitudinal sectional view taken along the line - in FIG. 1, and FIG. 3 is a longitudinal sectional view taken along the line - in FIG. 1. ,
Figure 4 is a plan view taken from the - line in Figure 1;
The figure is a longitudinal cross-sectional view showing a state in which paint has been filled into a parison by a paint filling nozzle, which is an embodiment of the present invention.
A vertical cross-sectional view showing paint being discharged from the parison by the secondary paint discharge nozzle, and Fig. 7 is a vertical cross-sectional view showing paint remaining in the parison being discharged by the secondary paint discharge nozzle, which is an embodiment of the present invention. FIG. 8 is a vertical cross-sectional view showing the state in which the paint film formed inside the parison is pre-dried by the primary heating air nozzle according to an embodiment of the present invention, and FIG. FIG. 2 is a longitudinal sectional view showing a state in which a paint film is completely dried by a secondary heating air nozzle according to an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Paint film coating device, 9... Plastic bottomed parison, 10... Holder, 11... Hole, 1
2... Mouth part, 14... Support ring, 15... Body part, 18, 19... Frame (part of the device that circulates and transfers the holder), 20a, 20b, 20
d, 20e, 20f, 20g, 20h, 20i...
...Air cylinder, 20c...Hydraulic cylinder (part of the device that circulates and transfers the holder), 28
...Paint filling nozzle, 30...Water emulsion paint, 30a...Paint film, 30a''...Completely dried paint film, 35...Primary paint discharge nozzle, 44...Secondary paint discharge nozzle, 62...1 Next heating air nozzle,
72...Secondary heating air nozzle.

Claims (1)

[Claims] 1 Blow molding or stretching - A device for forming a gas barrier coating on the inner surface of a plastic bottomed parison for forming a blow molded bottle, the device having a hole through which the body of the parison passes. a holder for holding the parison with the mouth of the parison facing upward by engaging with a support ring of the parison; a filling nozzle for filling a water emulsion paint with barrier properties at least up to the level of the support ring; a first discharge nozzle for discharging most of the filled paint; a first discharge nozzle for discharging the paint remaining at the bottom of the parison after the discharge; A second discharge nozzle for discharging the parison, a heated air nozzle for drying the film of paint remaining on the inner surface of the parison, and the holder is circulated and transferred so that the mouth of the parison is located directly below each of the nozzles. An apparatus for coating a plastic parison with a coating film, characterized in that the apparatus is equipped with an apparatus.