JPS6360705B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for making a styrenic resin foam board flexible.

Styrenic resin foam boards exhibit good thermal insulation properties and have high mechanical strength, so they are widely used as thermal insulation materials at low temperatures. However, this foam board has the disadvantage of being prone to buckling. In other words, this foam board has poor elasticity, so if you try to bend it, it may break, or it may buckle while being used as a cushioning material for packaging. This will result in the loss of protection ability. Therefore, it was found that the uses of this foam board were limited. Therefore, the inventor attempted to make this foam board flexible and easy to bend.

In relation to flexibility, which is the object of the present invention, attempts to impart flexure to a foam board are already known. It is described in Japanese Patent Publication No. 42-26950. This publication applies a force that reduces the length of the foam board in the direction in which it extends.
It teaches how to give deflection to foam boards. According to this method, the foam board becomes flexible. but,
It is not easy to shorten the length of the plate so as not to deform or break it, and furthermore, to actually do this continuously requires a large-scale device. Therefore, the inventor attempted to devise a method for imparting flexibility to a foam board using an even simpler operation.

The inventor attempted various experiments in an attempt to make a foam board made by extruding polystyrene containing a foaming agent from an extruder to make it flexible. Of that, 20 to 50 times as much as foam board.
An attempt was made to bend a uniformly finely foamed plate. For example, if you use a board with a foaming ratio of 35 times, a thickness of approximately 18 mm, a width of 120 mm, and a length of 200 mm, support both ends of the board in the length direction, and expand it so that the center line extending in the length direction draws an arc. Curved. Moreover, the curve is
I proceeded slowly to avoid breaking the board until the center line formed an arc with a radius of about 60 mm. At this point, the plate seemed to be about to break, so I stopped bending it any further and returned it to its original flat shape. As a result, it was confirmed that the board became significantly more flexible.

The inventor attempted to bend an object that had been bent to one side and then returned to its original position as described above, to further bend it significantly to the opposite side, and then to return it to its original position. As a result, it was confirmed that the material bent once in the forward direction and once in the opposite direction becomes extremely flexible. In addition, it was observed that when bent in the opposite direction, the material contracted significantly in the length direction. Furthermore, it was confirmed that once bent in this way, it did not show much resistance when bent a second time, so it could be bent even further with a small amount of force. Furthermore, it has been found that repeating such bending further increases the flexibility of the foam board. This invention was made based on such knowledge.

This invention uses a styrene resin foam board, and gradually bends the foam board at a temperature below the softening temperature of the styrene resin so that the center line of the board forms an arc in its thickness.
This invention relates to a method for making a styrene resin foam board flexible, which is characterized by bending the foam board until the radius of curvature of the arc becomes small and the foam board is just before breaking, and then bending it in the same way to the opposite side.

The foamed board used as a material in the method of this invention is made by impregnating a styrene resin with a foaming agent and foaming it. The foam board uses a low-boiling aliphatic saturated hydrocarbon such as propane or butane as a blowing agent, melts a styrene resin in an extruder, and then adds the blowing agent to the resin in the melt. The foaming agent-containing resin thus obtained was extruded from an extruder to obtain a foaming ratio of 10% by weight.
It is foamed to more than double its size. It is desirable to use a foaming ratio within the range of 20 to 50 times.

The styrene resin is not limited to a styrene homopolymer, but also styrene copolymers, graft polymers, block polymers, and mixtures thereof. copolymers, graft polymers,
When using a block polymer or a mixture thereof, one containing 50% by weight or more of styrene is used.

In this invention method, a styrene resin foam board as described above is used as a material, and the foam board is bent at room temperature so that the center line of the thickness of the board draws an arc. The bending speed is low, that is, slow. This is to avoid the possibility that if the foam board is bent too quickly, it will break even if the foam board is slightly bent. Moreover, the bending state is such that the radius of curvature of the circular arc is as small as possible, in other words, it is bent greatly. The maximum limit of bending is that the foam board is for bending,
Until just before it breaks.

Immediately before the foam board breaks, the foam board exhibits a large resistance to bending and usually makes a slight breaking sound as a sign of breakage. Therefore, the bending limit is defined as the state where the occurrence of such a sound is almost recognized. The limit cannot be generalized because it varies depending on the type of foam board, degree of foaming, and history. However, with a foam board that is 20 to 50 times more foamed than polystyrene, if you bend it gently,
It can be easily bent to double the radius of curvature. Therefore, a normal polystyrene foam board has a radius of curvature of 1.5 to 15 times, preferably 2 to 5 times, the thickness of the board just before breaking.

It is desirable that such bending of the foam board be performed when a suitable amount of the foaming agent remains. This is because the foaming agent acts like an eyelid agent, so if a suitable amount of the foaming agent remains, the alarm plate can be easily bent without being damaged. Specifically, if there is too much foaming agent remaining, the foam board will become difficult to bend due to the lack of tension in the bubbles, and conversely, if there is too little foaming agent remaining, the bubbles will be brittle and break easily, making the foam board difficult to bend. This is because the plate becomes difficult to bend.

Generally, the blowing agent gradually escapes from the foam board when the foam board is left at room temperature, but if the foam board is left for 30 days after foaming, the escape of the foaming agent will be extremely small, and the remaining amount of the foaming agent will be almost negligible. It becomes constant and appears to be in an equilibrium state. Based on the blowing agent content in such an equilibrium state, the blowing agent content suitable for bending is 1.5 to 4 times, preferably 2 to 3 times, the content in the equilibrium state. Generally, the escape rate of the blowing agent is
Since it depends on the type of blowing agent, it is difficult to determine in general how long after foaming the point at which the blowing agent is contained is suitable for bending, but the approximate period is 1-10 days, preferably around 7 days.

It is easy to bend the foam board so that the center line of its thickness forms an arc. For example, both longitudinal ends of the foam board may be supported with hands or other means, and the midpoint thereof may be pressed so that the foam board flexes significantly.
Alternatively, the foam board may be pressed against the surface of the roll so that the foam board bends along the surface of the roll.

Bending operations can also be performed continuously,
It can also be performed discontinuously. To do this continuously, the foam board may be bent along the surface of the rolls by passing it in a zigzag pattern between rolls arranged at intervals and rotating in the same direction. To do this discontinuously, it may be pressed between presses.

The bending operation is performed below the softening temperature of the foam board.
This is to give the foam board as much elastic deformation as possible. Furthermore, although it is convenient to perform the bending operation along the longitudinal direction, it may also be performed along the width direction, or may be performed simultaneously along both directions.

The bending operation should be performed slowly and gradually at the lowest possible speed. More specifically, the displacement perpendicular to the longitudinal direction is 1 between both ends and their midpoint.
It is gradually bent at a rate of about 10mm to 1000mm per minute. In the early stages of bending, it may not be necessary to bend at such low speeds, but in the final stages, when the foam board approaches a state of failure, it may be necessary to bend slowly at the speeds mentioned above. do.

The time required to maintain the state near the point of rupture may be from several seconds to several minutes. If the foam board is left bent for too long, for example 24 hours, it will lose its ability to return to its original state, which is inconvenient.

As described above, after bending the foam board to one side, the foam board is returned to its original state. Then bend the foam board further to the opposite side. The operation of bending to the opposite side is exactly the same as the operation of bending to one side described above, only the direction of bending is reversed. That is, the bending speed, bending limit, and time for maintaining the bent state are all the same.

With the method of the invention, as described above, only one bend to one side and one bend to the opposite side is sufficient. However, in order to obtain sufficient flexibility, it is not enough to bend each part just once, and such a set of operations is repeated several times. However, 2 of the operations forming a pair
After the first bending, it is not necessary to perform the bending gradually at a lower speed than the first time, but the bending speed can be increased somewhat, and the bending limit can be gradually increased.

The foam board treated by the method of this invention has a reduced length in the longitudinal direction. In other words, the distance between the two ends of the arc is reduced. On the other hand, the length in the thickness direction does not change much. This shrinkage is the first
It is most noticeable during the second bending, and becomes smaller as the bending continues after the second bending.

The method of this invention is characterized in that it is easy to implement. That is, according to the method of this invention,
It is excellent in that flexibility can be easily imparted by simply bending in the longitudinal direction. More specifically, foam boards treated by the method of the invention are flexible and highly pliable. Therefore, the article treated according to the invention can be bent to a small radius of curvature without buckling. Therefore, since it can be first formed into a flat board and later bent into any shape, it can be used for the same purposes as soft or semi-rigid foam boards, such as as a cushioning material, a heat insulating material, etc.
Furthermore, it can be used as a filler in curved areas. In this respect, the method of this invention has great utility.

Claims (1)

[Claims] 1 Using a styrene resin foam board, gradually bend the foam board below the softening temperature of the styrene resin so that the center line of the board's thickness forms an arc, and the radius of curvature of the arc becomes smaller until the foam board becomes a board. Thickness 1.5 to 15
A method for making a styrene resin foam board flexible, which is characterized by bending it to a state where it has twice the radius of curvature, and then bending it in the same way to the opposite side.