JP2536388B2 - Shape memory foam - Google Patents

Description

Detailed Description of the Invention

[0001]

This invention relates to shape memory foams,
By adhering a thermoplastic polymer to the inner surfaces of the open cells of the polyurethane shape memory foam, the hygroscopicity of the thermoplastic polymer is reduced and the stability of the shape under high humidity is improved.

[0002]

2. Description of the Related Art Generally, a polyurethane shape memory foam is given a shape by molding (external force is applied) at a temperature exceeding a glass transition point (hereinafter, abbreviated as Tg), and then a Tg or less is applied in this state. The shape can be fixed by cooling to the temperature. (Hereinafter, the original shape that recovers at a temperature exceeding Tg when no external force is applied is referred to as a memory shape, and the shape to which the applied shape is fixed is referred to as a fixed shape.) The polyurethane shape memory foam is used at Tg or less. As long as it is kept, it remains hard and retains the fixed shape, but when the temperature exceeds Tg, it becomes a soft rubber-like state and returns to the memorized shape. Polyurethane shape memory foam T
g is determined by the ambient temperature of use of the polyurethane shape memory foam, and Tg can be changed by changing the degree of crosslinking of the polyurethane. Further, when the shape-provided polyurethane shape memory foam is heated to a temperature of Tg or higher, the shape is softened, the shape is restored from the applied fixed shape to the memory shape, and the shape can be re-applied by further molding.

[0003]

By the way, since the polyurethane shape memory foam is a material which easily absorbs moisture, it is plasticized by absorbing moisture, and Tg drops, thereby maintaining its fixed shape and stability. There is a problem that is damaged. For example, assuming a use environment temperature of 40 ° C. or lower, a shape of a polyurethane shape memory foam having a Tg of 60 ° C. is given at 100 ° C., and then cooled to 60 ° C. or lower to fix the shape, 40 ° C. or lower However, when the humidity rises, for example, when the humidity is 95%, Tg drops to 40 ° C. As a result, the polyurethane shape memory foam will recover to the memorized shape in about 15 minutes.

The present invention has been made in view of the above circumstances. It is difficult for Tg to change even when the environmental humidity is high.
It is to provide a shape memory foam having a high fixed shape retention property.

[0005]

The shape memory foam of the present invention is a polyurethane shape memory foam having open cells, wherein a thermoplastic polymer is adhered to the inner surface of the open cells. To do.

[0006]

In the shape memory foam of the present invention, since the thermoplastic polymer is adhered to the inner surfaces of the cells of the polyurethane shape memory foam, the shape of the thermoplastic polymer can be improved by the above-mentioned thermoplastic polymer even when the environmental humidity is high. Moisture absorption of the polyurethane shape memory foam is prevented. Therefore, the change in Tg of the polyurethane shape memory foam due to the moisture absorption of the polyurethane shape memory foam is reduced, which prevents the polyurethane shape memory foam from recovering from the fixed shape to the memorized shape. Can be held. Further, even if the polyurethane shape memory foam absorbs moisture and plasticizes, the polyurethane shape memory foam has a fixed shape due to the rigidity of the thermoplastic polymer in the temperature range below the softening point of the thermoplastic polymer. It becomes possible to hold.

The present invention will be described in detail below. The shape memory foam of the present invention is a polyurethane shape memory foam having open cells, and has a thermoplastic polymer attached to the inner surfaces of the cells.

The adhesion of the thermoplastic polymer to the inner surface of the cell may be a state in which the cell is filled with the thermoplastic polymer.

Although the glass transition point of such a polyurethane shape memory foam varies depending on the use of the foam, it is preferably about + 40 ° C. to + 90 ° C. in view of the normal use range.

As the thermoplastic polymer, thermoplastic polyester, ethylene-vinyl acetate copolymer, ethylene-acrylate copolymer, ethylene-vinyl acetate-acrylate copolymer, thermoplastic polyurethane, etc. can be used. For this, PLAXEL H7 (trade name; manufactured by Daicel), which is a type of thermoplastic polyester, is suitable.

The softening point of the thermoplastic polymer is -20 ° C to the glass transition point of the polyurethane shape memory foam.
It is preferably + 70 ° C. More strictly speaking, it is preferable to set the softening point of the thermoplastic polymer within the range of -20 ° C at which the polyurethane shape memory foam starts to show a softening tendency to + 70 ° C at which it starts to show a curing tendency. If the softening point of the thermoplastic polymer is not within the above range, the thermoplastic polymer may soften and flow in the temperature range where the polyurethane shape memory foam maintains the fixed shape. Further, even if the polyurethane shape memory foam is softened, if the thermoplastic polymer does not soften,
Since the shape cannot be imparted to the polyurethane shape memory foam, the polyurethane shape memory foam is abnormally heated in order to soften the thermoplastic polymer, resulting in deterioration of properties.

More preferably, the softening point of the thermoplastic polymer (Tg in the case where the thermoplastic polymer is amorphous, Tm in the case where it is crystalline) is approximately the same as the Tg of the polyurethane shape memory foam.

Next, an example of a method for producing the shape memory foam of the present invention will be described with reference to FIG. First, a polyol, a diisocyanate, a foaming agent, a catalyst, a bubble size adjusting agent and the like are mixed with a mixer. Then, this is foam-molded in a molding die to produce a polyurethane shape memory foam 1 having open cells. On the other hand, a thermoplastic polymer solution 2 in which a thermoplastic polymer is dissolved in a solvent is prepared, and the container 3 is filled with this.

Next, the polyurethane shape memory foam 1 is immersed in the thermoplastic polymer solution 2 in the container 3. Then, the container 3 is placed in a vacuum chamber 5 connected to a negative pressure source (vacuum pump) 4, the negative pressure source 4 is operated to reduce the pressure in the vacuum chamber 5, and the polyurethane shape memory foam 1 The air in the open cells is replaced with the thermoplastic polymer solution 2.

Finally, after taking out the polyurethane shape memory foam 1 from the vacuum chamber 5, the solvent in the thermoplastic polymer solution 2 is volatilized to obtain the desired shape memory foam. In this way, the thermoplastic polymer of the thermoplastic polymer solution 2 is attached inside the cells of the polyurethane shape memory foam 1.

The shape memory foam obtained in this manner is a polyurethane shape memory foam in which the thermoplastic polymer is adhered to the inside of the open cells, so that even if the operating environment humidity becomes high, Since the plastic polymer prevents the polyurethane shape memory foam from absorbing moisture, the change in Tg is reduced, which prevents the polyurethane shape memory foam from recovering from the fixed shape to the memory shape.
Can hold a fixed shape. Further, even if the polyurethane shape memory foam absorbs moisture and plasticizes, the polyurethane shape memory foam will have a fixed shape due to the rigidity of the thermoplastic polymer in the temperature range below the softening point of the thermoplastic polymer. Can hold Therefore, such a shape memory foam has a high ability to retain a fixed shape.

[0017]

【Example】

Example A polyurethane shape memory foam 1 (Tg = 60 ° C.) having open cells and having a thickness of 10 mm was prepared. On the other hand, Praxel H7 (trade name; manufactured by Daicel) having a softening point of 60 ° C. was dissolved in toluene to prepare a 10 wt% thermoplastic polymer solution 2, which was filled in the container 3.

Next, the polyurethane shape memory foam 1 was immersed in the thermoplastic polymer solution 2 in the container 3. Then, the container 3 is placed in a vacuum chamber 5 connected to a vacuum pump, the vacuum pump is operated to reduce the pressure in the vacuum chamber 5 to 8 kPa, and the air in the bubbles of the polyurethane shape memory foam 1 is removed. The thermoplastic polymer solution 2 was replaced. Finally, the polyurethane shape memory foam 1 was taken out from the vacuum chamber 5, and then toluene was volatilized to obtain a target shape memory foam. The shape memory foam of this example had a thermoplastic polymer (Plaxel H7) in the cells.

Comparative Example A shape memory foam similar to that of the example was obtained, except that the polyurethane shape memory foam was not immersed in the 10% thermoplastic polymer solution 2. The shape memory foam of this comparative example had no thermoplastic polymer (Plaxel H7) in the cells.

Next, the shape memory foam of the embodiment (thickness 1
0 mm) and the shape memory foam of Comparative Example (thickness 10 mm) are each given a shape at 100 ° C. (compressed to a thickness of 4 mm).
After that, the shape was fixed (thickness 4 mm) by cooling to 25 ° C. in this state. Then, these were put into air at 100 ° C., and their shape restoring ability (memory ability) was tested. The result is shown in FIG. In FIG. 2, the rate of change on the vertical axis means (thickness of shape memory foam after shape imparting / thickness of shape memory foam before shape imparting) × 100. From FIG. 2, it was confirmed that the shape memory foams of the examples had the ability to restore from the fixed shape to the memory shape in the same manner as the conventional shape memory foam of the comparative example.

Further, the shape memory foams of the examples and the shape memory foams of the comparative examples were used, and each of them was given a shape at 100 ° C. (compressed to a thickness of 4 mm), and then 25 in this state.
The shape was fixed (thickness: 4 mm) by cooling to ℃. Then, these were placed in air at 45 ° C. and 95% relative humidity to test the shape retention. The result is shown in FIG. In FIG. 3, the rate of change on the vertical axis is (thickness of shape memory foam after shape application / thickness of shape memory foam before shape application) × 1
It means 00. As is clear from FIG. 3, the shape memory foam of the comparative example was plasticized by absorbing moisture and Tg dropped, and 100% was restored to the memory shape in 15 minutes. On the other hand, the shape memory foams of Examples retain the fixed shape (thickness of about 40% of the memorized shape) even after about 300 hours, and have high fixed shape retention. Was confirmed.

[0022]

As described above, since the shape memory foam of the present invention has the thermoplastic polymer adhered to the open cells of the polyurethane shape memory foam, it can be used in high environmental humidity. Since the thermoplastic polymer prevents the polyurethane shape memory foam from absorbing moisture, the change in Tg is reduced, whereby the polyurethane shape memory foam can be prevented from recovering from the fixed shape to the memory shape, and the fixed shape can be maintained. . Even if the polyurethane shape memory foam absorbs moisture and becomes plastic,
In the temperature range below the softening point of the thermoplastic polymer,
Polyurethane shape memory foam can retain a fixed shape due to the rigidity of the thermoplastic polymer. Therefore, the shape memory foam of the present invention has an advantage that it has a high fixed shape retention property.

[Brief description of drawings]

FIG. 1 is a diagram illustrating an example of a method for producing the shape memory foam of the present invention.

FIG. 2 is a graph showing the results of testing the shape restoring ability of the shape memory foams of Examples and the shape memory foams of Comparative Examples.

FIG. 3 is a graph showing the results of testing the shape retention of the shape memory foams of Examples and the shape memory foams of Comparative Examples.

[Explanation of symbols]

1 ... Polyurethane shape memory foam, 2 ... Thermoplastic polymer

Claims (1)

(57) [Claims] 1. A shape memory foam comprising a polyurethane shape memory foam having open cells, wherein a thermoplastic polymer is attached to the inside surfaces of the open cells.