JPH0120051B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a molding method in which a pattern is formed while cooling 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, 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. Furthermore, since the cooling speed is slow, the polymer tends to crystallize and become opaque, and this tendency is particularly strong in tubes with a thin thickness. 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 because 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, this cooling method cannot increase the molding speed. The speed is limited to 35m/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 in the inflation method, T-die method, etc., and using the vapor latent heat of the water 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. It is a plastic cooling molding method that can mold products, and it also creates areas with different degrees of crystallinity by limiting the contact points of the foam to the film or sheet surface, etc., and varying the size of the foam. , provides a method of forming a pattern on the film or sheet surface due to unevenness or a difference in transparency at the same time as the above-mentioned cooling.

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. A liquefaction filter 10 communicates with the foam suspension chamber 8 through a foam circulation chamber 11, and the foam filtered by the liquefaction filter 10 is fed back to the solution storage tank 7 again. 12 is an air outlet 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 11.
This is a discharge port installed in the Next, the method of this 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 extruder 1 ring die 2, and the outer periphery of the tube 16 is primarily cooled by air from the primary cooler 3. Then, the foam 15 successively contacts the area below the frost line of the tube 16 extruded from the extruder 1, that is, the outer periphery of the tube 16 which is still in a molten state, through the opening 9 of the foam floating chamber 8 of the foam generator 4. 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 rapidly cools the tube 16. When the foam 15 comes into contact with the outer surface of the tube 16, the foam 15 is artificially removed.
The amount and size of 5, the foam 15 on the outer surface of the tube 16
By changing the contact points of tube 1
Create areas with different degrees of cooling on the outer surface of 6. Thereafter, the tube 16 is further cooled secondary by the upper secondary cooler 17 of the foam generating device 4, but the air from the secondary cooler 17 promotes evaporation of the foam 15, and the foam contact point As the cooling progresses, the areas in contact with the foam solidify, and the areas where the foam did not come into contact are stretched, thereby forming an uneven pattern on the outer surface of the tube 16. Also tube 1
If the foam 6 is still hot even after secondary cooling, it is also possible to design a mounting system that brings the foam 15 into contact with the foam 15 to form a multi-stage system. Then, the tube 16 is pulled up by the upper pinch roller 6, and the tube 1
6 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 enters the liquefaction filter 10 through the circulation chamber 11, becomes liquefied, and returns to the solution storage tank 7 again. be.

Furthermore, FIGS. 2 and 4 show examples in which the present invention is applied to the T-die method or the flat die method. Similar to the above-mentioned embodiments, 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 intermittently being brought into contact with the foam 15, and at the same time, an uneven pattern is formed on the outer surface of 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, this latent heat of vaporization method absorbs more than 10 times more heat than the conventional water-cooled method. 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.
A foam is created by adding a foaming agent to an aqueous solution or aqueous dispersion, and the extremely thin foam is brought into continuous contact with a film or sheet, resulting in rapid evaporation. Or it takes heat away from the sheet. For this purpose, the concentration of a blowing agent such as a surfactant in the above aqueous solution or aqueous dispersion is appropriate to be about 0.5 to 0.01%, and furthermore, by mixing an organic solvent such as alcohol into this aqueous solution or aqueous liquid, an azeotropic It forms a compound that 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 (3 dyne or less).

In addition, since the cooling by the foam 15 is carried out rapidly and continuously by the 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, so transparency is greatly improved, and Good strength balance in two axes. Furthermore, the plastic film or sheet molded according to the present invention has a good appearance and is very flexible to the touch. Furthermore, as in the above embodiments, by varying the amount and size of the bubbles and the point of contact of the bubbles with the outer surface of the tube, film, or sheet, points with different degrees of cooling are created on the surface of the film or sheet. Forms an uneven pattern on the outer surface of a tube, film, or sheet.

These patterns have areas that are quenched by contact with the foam and areas that are not quenched, resulting in areas with different degrees of transparency.

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. , can be molded into patterns.

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 speed up cooling and form patterns by bringing foam into contact with the tube. It is. 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.

As described above, this invention brings water bubbles into contact with molten plastics, removes heat from the plastics using the latent heat of evaporation caused by the vaporization of the bubbles, and cools and molds the plastics, thereby increasing the cooling effect and cooling speed. A plastic with good transparency and high strength can be molded, and which has patterns formed by unevenness or differences in transparency by variously changing the size, amount, and contact point of the bubbles to the plastic. The molding process can be performed simultaneously with 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. 3 is the An enlarged view of the main part of the figure, Figure 4 is the second
It is an enlarged view of the main part of the figure. 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)

[Claims] 1. A large number of bubbles are created using an appropriate method using an aqueous solution or aqueous dispersion, and these bubbles are brought into contact with the molten plastic at regular intervals or intermittently to cool the plastic and at the same time create unevenness or unevenness on the surface of the plastic. A plastic cooling molding method characterized by forming a pattern consisting of differences in transparency.