JPS6039246Y2 - Equipment for foam production - Google Patents

Description

[Detailed description of the invention] This invention relates to an apparatus for producing foam, especially for resins that are easily thermally decomposed such as vinyl chloride resins.
The present invention relates to an apparatus for extrusion molding a foam made of a resin having a relatively high melting point, such as a styrene resin.

Foams are often made from one type of resin, but sometimes they are made from a mixture of two or more types of resin.

In the latter case, two or more resins are first mixed mechanically in granular or powdered form without applying heat, and this mixture is fed to an ordinary foaming extruder for extrusion and foaming.

However, in this method, when the respective melting temperatures of two or more types of resins are different, or when two or more types of resins include resins that are easily thermally decomposed, or when two or more types of resins are When the physical properties of the two materials differ considerably, it may be difficult to mix them uniformly.

For example, when trying to extrude a mixed resin foam of polyvinyl chloride and polystyrene, polyvinyl chloride has a lower melting temperature than polystyrene and is more easily thermally decomposed. If extruded at a relatively low temperature so that it does not decompose, the polystyrene will not melt sufficiently and as a result the two resins will not mix.

On the other hand, if extruded at a relatively high temperature where polystyrene is sufficiently melted, polyvinyl chloride will thermally decompose and its physical properties will deteriorate significantly, making it impossible to obtain a good homogeneous mixture.

However, when a blowing agent is added to a high melting point resin such as polystyrene, if the blowing agent is a hydrocarbon such as butane or pentane, the resin is plasticized by the blowing agent and the foam containing the blowing agent is It was confirmed that the polystyrene melt does not solidify even when cooled below the decomposition temperature of polyvinyl chloride, making mixing easier.

Also, some resins mix well with the blowing agent and others do not, but among them, select a resin that mixes well with the blowing agent, put it into one extruder, and then Mix well with the foaming agent and knead it uniformly in a separate extruder, while kneading the resin that is difficult to mix with the foaming agent in a separate extruder.
It was confirmed that when these were mixed after that, uniform mixing was easily obtained, and therefore suitable for obtaining a foam.

Further, in this case, it was confirmed that it is convenient to use a twin screw extruder to knead the resin that is difficult to mix with the blowing agent.

This invention provides a device made based on such confirmation.

This idea was based on the combination of a single screw extruder and a twin screw extruder. The tip of the barrel is opened in the middle of the barrel of a twin-screw extruder, and the twin-screw extruder is equipped with a hopper for supplying raw resin at the rear end of the barrel, and is related to a foam manufacturing device. .

The device according to this invention will be explained as follows with reference to the drawings.

The figure is a schematic cross-sectional view of the device according to this invention.

In the figure, a is a single-screw extruder, b is a twin-screw extruder, and the tip of the extruder a is connected to the middle of the extruder.

1 is a hopper of extruder a, 2 is a barrel, 3 is a screw, 4 is a heating device, 5 is a blowing agent pressure inlet, and 6 is a connecting pipe.

7 is a hopper of the extruder; 8 and 9 are both screws; 10 is a barrel; 11 is a heating device; 12 is a second blowing agent press inlet; and 13 is an extrusion port.

The screws 8 and 9 may both be rotated in the same direction, or may be rotated in opposite directions, either outward or inward, respectively.

Of these, rotation in the same direction is preferred.

The device of this invention is used as follows.

As materials, for example, polystyrene pellets are charged into the hopper 1 of the extruder a, butane is pressed into the blowing agent injection port 5, and polyvinyl chloride is charged into the hopper 7 of the extruder.

The polystyrene is transported by the screw 3 of the extruder a, receives heat from the heated barrel 2 and melts, and is thoroughly kneaded between the screw 3 and the barrel 2 to form a uniform melt.

At this time, butane is injected from the injection port 5 to become a fluid melt containing butane, which progresses through the connected vibro.

At this time, the melt is cooled to below the thermal decomposition temperature of polyvinyl chloride.

On the other hand, the polyvinyl chloride charged into the hopper 7 of the extruder is carried by the screws 8 and 9, and is transported to the barrel 1.
It receives heat from 0 and melts, and the screw 8,
9 and barrel 10 to form a uniform melt.

Afterwards, he encounters polystyrene from the connected vibro,
In addition to being a molten substance, polystyrene has increased fluidity with butane and is cooled below the thermal decomposition temperature of polyvinyl chloride, so it does not thermally decompose polyvinyl chloride (it is not easily mixed). Ru.

Polyvinyl chloride has a poor ability to dissolve butane, but polystyrene dissolves butane well, so the mixture will contain some butane.

In this state, the mixture is immediately extruded from the extrusion port 13.

At this time, a blowing agent such as butane may be added through the injection port 12.

However, in the device according to this invention, the pressure inlet 12 is not necessarily required.

According to the device of this invention, a foam made from a mixture of two types of resin can be easily obtained all at once.

This point will be explained in detail as follows. Since the resin, which is easily melted such as polystyrene, is kneaded using an axial screw extruder, kneading is both economical and easy.

In addition, since polystyrene tends to contain blowing agents such as butane, it becomes more fluid by including it, and as a result, it remains fluid even when cooled to below the thermal decomposition temperature of polyvinyl chloride. Since it does not lose its content, it can be fed into the connected vibro as a melt at a temperature below the thermal decomposition temperature of polyvinyl chloride.

On the other hand, polyvinyl chloride is a resin that is difficult to melt because its softening point and decomposition point are close to each other, but since it is kneaded in a twin-screw extruder, there is less internal heat generation during kneading, and the resin There is little temperature unevenness and smooth melting is possible.

This melt contains a highly fluid polystyrene melt,
It is cooled to below the thermal decomposition temperature of polyvinyl chloride and added.
Since the polyvinyl chloride is kneaded as is in the twin-screw extruder, it is easily kneaded with the polystyrene melt without decomposition, resulting in a uniform mixture.

A uniform foam is thus obtained.

Furthermore, since the pressure inside the barrel of the two-wheel screw extruder is low, the fluid resin that has been heated and melted in the single-screw extruder and kneaded with the foaming agent is very easily forced into the twin-screw extruder.

Furthermore, by adjusting the rotation speed of the screw in each extruder, the mixing ratio of the two resins can be arbitrarily changed.

The device of this invention has such advantages.

The device of this invention is particularly suitable for making foams using resins such as polystyrene and polyvinyl chloride, which have poor compatibility with each other and are easily decomposed when heated.

[Brief explanation of drawings]

The figure is a schematic cross-sectional view of an extruder according to this invention. In the figure, a is a single-screw extruder, b is a twin-screw extruder, 1 and 7 are both hoppers, 2 and 10 are barrels, 3, 9, and 8 are all screws, 4 and 11 are heating tools, and 5 and 12 is a blowing agent pressure inlet, 6 is a connecting pipe, 1
3 is an extrusion port.

Claims (1)

[Scope of utility model registration request] The result is a combination of a single screw extruder and a twin screw extruder, and the single screw extruder is equipped with a hopper for supplying raw resin at the rear end of the barrel, a blowing agent pressure inlet in the middle of the barrel, and a barrel The tip of the extruder is opened halfway into the barrel of a twin-screw extruder, and the two-wheel screw extruder is equipped with a hopper for supplying raw resin at the rear end of the barrel.