JPS6348695B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to a method of cold molding plastics.

Conventionally, for example, methods for cooling a molten tube extruded from an extruder die in the inflation method include forced air cooling, in which air is blown onto the tube, and water cooling, in which water is flowed in a ring shape and comes into contact with the outer circumference of the tube. be. In the case of air cooling, it is necessary to blow a large amount of air around the tube, and the cooling effect is small. Moreover, since the cooling speed is slow, the polymer tends to crystallize and become opaque.
This tendency is particularly strong for thin tubes. In addition, thick tubes cause blocking due to internal close contact when the molding speed is increased. On the other hand, the water cooling method has good transparency, but since the cooling is done by absorbing heat from the water, it can only absorb heat by the amount of temperature rise of the cooling water. For example, if 1 c.c. of water rises by 1°C, it will endotherm by 1 cal. Therefore, a large amount of cooling water is required. Moreover, it is very difficult to continuously create a uniform layer of water that comes into contact with the tube surface, and if you try to create it at high speed, the water layer will never become flat.
Therefore, with this cooling method, it is not possible to increase the molding speed, and the molding speed is only 35 m/min. Moreover, depending on the material, there are drawbacks such as curling.

This invention was made in view of these points, and involves bringing water bubbles into contact with a molten plastic film or sheet, etc. in the inflation method, T-die method, etc., and using the latent heat of vaporization of the bubbles to melt the plastic. It cools the film or sheet, and can increase the cooling molding speed compared to conventional air-cooling and water-cooling methods, uses extremely little water, and has good transparency and molding with a good balance of strength in two axes. The purpose of this invention is to provide a cooling molding method for plastics that can mold products. Furthermore, the present invention provides a method of forming a uniform film made of the coating agent on a plastic film or sheet surface, etc. at the same time as cooling by incorporating an appropriate coating agent into the aqueous solution or aqueous dispersion that forms the foam. .

An embodiment of the present invention will be described below with reference to the drawings.

FIGS. 1 and 3 show an embodiment in which the present invention is applied to the inflation method. First, the apparatus used in the present invention will be explained. 1 is an extruder, 2 is a ring die of the extruder 1, 3 is an annular air-cooled primary cooling machine installed immediately above the ring die 2,
Reference numeral 4 designates an annular foam generator provided immediately above the primary cooler 3, 5 a guide plate provided above the foam generator 4, and 6 a pinch roller provided on the guide plate 5. 7 is the foam generator 4 mentioned above.
The solution storage tank 8 is a foam floating chamber provided above the solution storage tank 7, and has an opening 9 provided on one side above the foam floating chamber 8, that is, on the inner peripheral side of the foam generator 4. Reference numeral 10 denotes a liquefaction vessel which communicates with the foam suspension chamber 8 through a foam circulation chamber 11, and the foam passed through the liquefaction vessel 10 is fed back to the solution storage tank 7 again. 12 is an air discharge port provided in the solution storage tank 7, 13 is a solution inlet provided in the foam floating chamber 8, and 14 is the circulation chamber 1.
This is the outlet provided at 1. The following method of the present invention will be explained. First, an aqueous solution or aqueous dispersion containing about 0.05% surfactant is placed in the solution storage tank 7 of the foam generator 4, and air is blown into the solution storage tank 7 from the air outlet 12. This causes many bubbles 15 to float in the bubble floating chamber 8. On the other hand, a molten plastic tube 16 is extruded from the ring die 2 of the extruder 1, and the outer periphery of the tube 16 is primarily cooled by air from the primary cooler 3. Then, the foam generator 4 is placed below the frost line of the tube 16 extruded from the extruder 1, that is, on the outer periphery of the tube 16 which is still in a molten state.
The bubbles 15 come into contact with each other one after another through the opening 9 of the bubble floating chamber 8. Each foam 15 evaporates as soon as it contacts the outer surface of the molten tube 16.
This latent heat of vaporization removes heat from the tube 16, and the tube 16 is rapidly cooled. Thereafter, the tube 16 is further cooled by the secondary cooler 17 above the foam generator 4, and the air from the secondary cooler 17 accelerates the evaporation of the foam 15, causing the foam to contact the foam. cooling progresses further. Furthermore, if the tube 16 is still hot even after secondary cooling, the device for bringing the foam 15 into contact with it may be designed to be multistage. The tube 16 is then pulled up by the upper pinch roller 6, and the tube 16 is folded into a flat shape and wound into a roll. On the other hand, the foam 15 in the foam floating chamber 8 of the foam generator 4 that does not come into contact with the tube 16 passes through the circulation chamber 11 and enters the liquefier 10, becomes liquefied, and returns to the solution storage tank 7 again. be.

Moreover, what is shown in FIG. 2 and FIG. 4 is an embodiment in which the present invention is applied to the T-die method or the flat die method, and like the above embodiment, the still material extruded from the T-shaped die 2' of the extruder 1' The foam generator 4' is placed on both sides of the molten plastic film 18.
The plastic film 18 is rapidly cooled by bringing the foam 15 into contact with the plastic film 18.

The present invention is the above-mentioned method, in which a molten film or sheet is cooled by the latent heat of vaporization of water, which is different from cooling by the absorption of heat from water in the conventional water-cooling system. In other words, in the case of water absorption in a conventional water-cooled system, for example, 1 c.c. of water heats up from 25°C.
Even if the temperature reaches 30℃, only 5 cal of heat can be absorbed. If 1 c.c. of water at 25°C is evaporated, the temperature will rise from 25°C to 100°C.
This is an endotherm of 75 cal, and when water at 100°C is evaporated, it becomes 540 cal. Therefore, a total of 615 cal of heat is absorbed. Therefore, the latent heat of evaporation system of this invention absorbs more than 10 times as much heat as the conventional water-cooled system. Therefore, the cooling efficiency is extremely high, and the amount of water required is 1/100 to 1/200 of that of conventional water cooling systems. In order to facilitate the evaporation of the water, it is necessary to make the thickness of the water film in contact with the film or sheet as uniform and thin as possible. Therefore, in this invention, we focused on the fact that the film thickness of water foam is extremely thin, about 1 μm, and therefore it is easy to vaporize and transport. By continuously bringing a thin layer of foam into contact with a film or sheet, evaporation occurs rapidly, and the latent heat of evaporation removes heat from the film or sheet in contact. For this purpose, the concentration of a foaming agent such as a surfactant in the above aqueous solution or aqueous dispersion is appropriate to be about 0.5 to 0.01%. It forms a boiling compound and evaporates very quickly. Further, in order to speed up cooling, it is necessary to speed up evaporation in this way, and for this purpose, it is desirable to make the size of the bubbles 15 as small and uniform as possible, and to have a low surface tension (30 dyne or less).

In addition, since the cooling by the foam 15 is carried out rapidly and continuously by the layer transfer of the thin film, the molecules are fixed in a state close to the arrangement of the molecules in the molten state, so crystallization is suppressed, and the transparency is greatly improved. It also has a good balance of strength in two axial directions. Furthermore, the plastic film or sheet molded according to the present invention has a good appearance and is very flexible to the touch.

In addition, the aqueous solution or aqueous dispersion containing the foaming agent in the above embodiments may contain chemicals such as antistatic agents, antifogging agents, and fungicides, coloring agents, metal powders, ceramics, polymeric materials, adhesives, etc. (hereinafter simply referred to as By mixing one or more of these (collectively referred to as coating agents), it is possible to form a film made of the coating agent at the same time as the film or sheet is cooled. In this case, when the coating agent dissolved or suspended in the foam comes into contact with the molten film or sheet, the moisture quickly evaporates and the coating agent adheres to the surface of the film or sheet, forming a large number of continuous bubbles. By contacting the film or sheet with the film or sheet, a uniform coating is formed on the surface of the film or sheet. As mentioned above, the foam film is extremely thin, so it evaporates quickly and the film formed is also thin. The adhesion of this coating to the film or sheet is carried out simultaneously with cooling during melting and by layer transfer of a thin film of foam, resulting in uniform adhesion and improved adhesion. In addition, since the mixed coating agent is applied at the same time as cooling, the temperature of the coating agent in contact with the molten film or sheet becomes high, and it is quickly spread onto the film or sheet surface, resulting in a uniform film surface. Fixed.

In this way, in this embodiment, the coating agent is placed on an extremely thin film of small bubbles with low surface tension, and the foam is transferred to the film or sheet, so the coating easily adheres to the surface of the film or sheet. A uniform and thin film can be formed by making continuous contact with each other. Therefore, the coating is retained for a long time. This can be applied to the above-mentioned inflation method, T-die method, etc., and can also be applied to laminate molding as shown in FIG. 5 and spinning molding as shown in FIG. 6.

That is, as shown in FIG.
The foam generating device 4 is brought close to one side of the still molten film 20 extruded from the film 20, and an aqueous solution or water containing an antistatic agent, adhesive, or surfactant is placed in the foam storage tank 7 of this device 4. Add the dispersion liquid,
By generating bubbles 15 and bringing the bubbles 15 into contact with the film 20, the film 20 is rapidly cooled, and at the same time, a dry film made of the antistatic agent and adhesive is formed on one surface of the film 20. In this state, a laminate material 21 such as a synthetic resin film or sheet, cloth, paper, etc. and the film 20 are placed between the cooling roll 22 and the pressure roll 23 and overlapped to form a laminate film 24. In this way, when this invention is used, the adhesive is applied at the same time as cooling, and this adhesive dries.
Since the laminate material 21 is polymerized in this state, laminate molding becomes extremely easy. Moreover, since the molded laminate film 24 has an antistatic layer formed inward over its entire surface, it has a high antistatic effect.

Also, as shown in FIG. 6, the die 26 of the extruder 25
The foam 25 generated by the foam generating device 4 is brought into contact with the molten spinning yarn 27 extruded from the foam, thereby cooling the spinning yarn 27 in the same manner as in the above embodiment.
At the same time, a coating made of a coating agent such as an antistatic agent can be formed on the outer periphery of the spinning yarn 27.

In addition, when the present invention is applied to the above-mentioned inflation method, a hole is made in the center of the ring die 2, foam is also introduced into the inner periphery of the tube 16, and the inner periphery of the tube 16 is cooled while circulating the internal air and external air. , coating, and pattern molding.

In addition, if the tube is above the frost line in the inflation method and the outer surface is solidified but the inner surface is not sufficiently cooled and solidified, the method of this invention can be used to bring foam into contact with the tube to speed up the cooling and form a film and pattern. Formation is also possible. In this way, the molten state of plastics referred to here includes all plastics that still have plasticity when heated, that is, they have not yet been solidified by heat. Furthermore, plastic molding is not limited to the extrusion molding of tubes, films, sheets, laminates, spinning, etc. as described in the above embodiments.

As described above, this invention brings water bubbles into contact with molten plastics, removes heat from the plastics using the latent heat of vaporization caused by the vaporization of the bubbles, and cools and molds the plastics, thereby increasing the cooling effect and cooling speed. At the same time, plastics with good transparency and high strength can be molded. Furthermore, by placing the above-mentioned coating agent on the foam, it is possible to extremely easily mold plastics in which a uniform coating of the coating agent is formed on the surface of the plastic at the same time as cooling.

[Brief explanation of drawings]

Fig. 1 is a side explanatory view showing an embodiment in which the present invention is applied to the inflation method, Fig. 2 is a side explanatory view showing an embodiment in which the invention is applied to the T-shaped die method, and Fig. An enlarged view of the main part of the figure, Figure 4 is the second
5 is an explanatory side view showing an embodiment in which the present invention is applied to laminate molding, and FIG. 6 is an explanatory side view showing an embodiment in which the present invention is applied to spinning molding. In the figure, 4 is a foam generator, 7 is a solution storage tank,
8 is a foam floating chamber, 9 is an opening, 12 is an air outlet, 15 is a foam, 16 is a tube, and 18 is a plastic film.

Claims (1)

[Scope of Claims] 1. A method for cooling and molding plastics, characterized in that a large number of foams are created by an appropriate method using an aqueous solution or an aqueous dispersion, and the foams are cooled by bringing the foams into contact with molten plastics. 2. A large number of foams are created by an appropriate method using an aqueous solution or aqueous dispersion containing an appropriate coating agent, and the foams are brought into contact with the molten plastic to cool the plastic and at the same time coat the surface of the plastic. A method for cooling and molding plastics, characterized by forming a film made of the above-mentioned coating agent. 3. The plastic cooling molding method according to claim 2, characterized in that an adhesive is contained in an aqueous solution or aqueous dispersion containing an appropriate coating agent.