JPH05155968A - Shape memory composition - Google Patents

Abstract

PURPOSE:To provide the subject compsn. which changes its three-dimensional shape with a change in temp. across a specified temp. and hence is useful as a sensor, etc. CONSTITUTION:The objective compsn. comprises a polyurethane resin prepd. by reacting reactants essentially including a polyester polyol of the general formula 1 (wherein (m) and (n) are each an integer of 4 or higher; and (p) is a number higher than 0) and a polyisocyanate compd. at 80 deg.C or higher, changes its three-dimensional shape with a change in temp. across a specified temp., which is useful as a temp. sensor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is capable of changing an arbitrary shape at a specific temperature or higher, and when the temperature is lowered below the specific temperature while changing the shape, the changed shape is maintained and the shape is changed again to the specific temperature or higher. The present invention relates to a shape-memory composition, which is characterized by recovering its original shape when exposed to light, and a temperature sensor using the shape-memory composition.

[0002]

2. Description of the Related Art In recent years, various materials whose states change in response to an external stimulus have been developed, and have come to be used as sensors and other functional parts in various fields such as analysis, measurement and control. .. Among these various materials, shape memory alloys and shape memory alloys can be used as materials that change their shape in response to thermal stimuli, fix their shape below a specific temperature, and restore their original shape when the temperature rises above a specific temperature again. Resins are known.

The shape-memory resin is softened at a specific temperature or higher and can change its shape. When the shape-memory resin is lowered below the specific temperature while changing the shape, the changed shape can be maintained, and when the temperature is again raised to the specific temperature or higher. It recovers the original shape. However, the specific temperature that changes the shape is the glass transition point, and since it utilizes the difference in the crystalline state of the polymer, there is a limit to the range of shape change above the specific temperature, and in general, simple bending and twisting Various deformations are used, and it is not possible to fix the shape by three-dimensional deformation of the resin itself or minutely complicated deformation. As described above, the fact that the conventional shape memory resin has a limited range of deformation is one of the reasons why it is not put into practical use while being highlighted in its functionality.

[0004]

By the way, a shape memory resin which is softened at a temperature above a specific temperature and capable of changing a shape up to a three-dimensional change and capable of storing even a fine and complicated shape has not yet been developed.

For example, it may be convenient if the shape can be freely changed at a certain temperature or higher and the shape is fixed when the shape is changed and kept at a certain temperature or lower. If the original shape can be recovered again at a certain temperature or higher, it is very convenient as a reusable material, and the shape recovery can be used as an operation in equipment and the like.

The present inventor has conducted extensive studies in view of the above points, and as a result, in a polyurethane resin obtained by reacting a specific polyester polyol and a polyisocyanate compound under certain conditions, below a certain temperature, an ester group The present invention has been found to be a tough resin that is considered to be caused by the secondary bond of and a rubber-like composition presumed to be due to the disappearance of the secondary bond at the above temperature, leading to the present invention.

Thus, the present invention is capable of softening at a specific temperature or higher and changing the shape up to a three-dimensional change. When the temperature is lowered to below the specific temperature, the changed shape is maintained even in a finely complicated portion, and again. The present invention provides a shape-memory composition characterized by recovering an original shape when the temperature is raised to a specific temperature or higher, and a thermo-responsive sensor using the shape-memory composition.

[Means for Solving the Problems]

In order to achieve the above-mentioned object, the shape memory composition of the present invention comprises (a) a general formula:

[Chemical 3] (However, in the formula, m and n are integers of 4 or more, p
Represents a number greater than 0) and a (b) polyisocyanate compound as essential components, and is composed of a polyurethane resin reacted at 80 ° C. or higher, and a shape memory that responds thermally at a specific temperature as a boundary. It is characterized by having a property.

[0009]

The polyester polyol used in the present invention has the following general formula:

[0010]

[Chemical 4]

(In the formula, m and n are integers of 4 or more, and p is a number larger than 0). Here, in the above formula, when m and n are less than 4, the obtained polyurethane composition becomes a general elastomer having no shape memory. There is no particular limitation as long as m and n are 4 or more, but when m or n is 10 or more, the melting point of the raw material, the viscosity after melting, and the cost are increased during the production of the polyester polyol. Therefore, a more preferable value of m and n is 4 to 9. The composition according to the present invention maintains the changed shape when the temperature is lowered below a certain temperature, and the time until the shape is maintained by lowering the temperature (hereinafter referred to as shape fixing time) is It depends on the number. The smaller the values of m and n are, the longer the shape fixing time is. On the contrary, the larger the values of m and n are, the shorter the shape fixing time is.

However, in the formula, when the methylene group represented by m and n has a side chain or when another atom is bonded to the methylene group (for example, ether group), the obtained polyurethane composition Is a composition having no shape memory.

The value of p in the formula is not particularly limited, but is preferably in the range of 0 <p ≦ 15 and 2 <p ≦ 1.
2 is more preferable. Here, within the range described above,
The larger the number of p, the higher the response temperature of shape memory, and the smaller it, the lower. However, when p is 16 or more, it is not preferable because the reactivity of the polyester polyol is lowered and the viscosity at the time of melting is increased during the production of the polyurethane composition.

Next, as the polyester polyol used in the present invention, a known compound obtained by a condensation reaction of a polyhydric alcohol and a dicarboxylic acid, or a known compound obtained by ring-opening polymerization of a lactone using a diol as an initiator is used. it can. It is also possible to use a mixture of two or more of these.

As the polyhydric alcohol, 1,4-butanediol, 1,6-hexanediol, 1,9-nonanediol and the like can be used, and as the dicarboxylic acid, adipic acid, suberic acid, azelaic acid, Sebacic acid or the like can be used. In addition, examples of the diol as an initiator in the lactone ring-opening polymerization include ethylene glycol, propylene glycol, butylene glycol, and hexamethylene glycol. As the lactone, γ
-Butyrolactone, δ-valerolactone, ε-caprolactone and the like.

The polyisocyanate compound used in the present invention is an organic compound having two or more isocyanate groups in one molecule and having a reactive isocyanate group for the active hydrogen-containing functional group of the polyester polyol. Be done. As an example of the polyisocyanate compound, general aromatic, aliphatic and alicyclic compounds can be used. For example, tolylene diisocyanate, hexamethylene diisocyanate (HMD
I), diphenylmethane diisocyanate (MDI),
There are liquid modified MDI and the like, and HMDI and MDI are particularly preferable. Moreover, you may use the compound etc. which have a terminal isocyanate group obtained by making the above-mentioned polyisocyanate compound and an active hydrogen containing compound react. here,
As the active hydrogen-containing compound, the polyester polyol used in the present invention is preferable, and when an active hydrogen-containing compound other than this is used, the shape fixing time becomes long and the thermal response sensitivity becomes slow, so that it is not always preferable. .. These polyisocyanate compounds can be used alone or in combination of two or more.

In the present invention, it is necessary to react the above-mentioned polyester polyol and polyisocyanate compound at 80 ° C. or higher. There is no particular problem if the reaction temperature is 80 ° C. or higher, but 100 to 170 ° C. is preferable, and 120 to 150 ° C. is more preferable. If the reaction temperature is lower than 80 ° C., the changed shape can be maintained when the temperature is changed to below the specific temperature while changing the shape, but it is not preferable because the original shape is not restored when the temperature is again above the specific temperature.

In carrying out the urethanization reaction between the polyester polyol and the polyisocyanate compound, an appropriate urethanization catalyst can be used. As the urethanization catalyst, known catalysts such as tertiary amine compounds and organic metal compounds can be used. For example, triethylenediamine, 1,4-hexamethylenediamine, 1,4-butanediamine, lead octylate, dibutyltin laurate and the like are preferable. However, the use of this urethanization catalyst is not an essential requirement of the present invention.

Further, in order to improve the durability and stability of the composition, as a stabilizer, a heat stabilizer, an antioxidant, an ultraviolet protective agent, an ultraviolet stabilizer, etc. may be used, if they do not cause any problems. Alternatively, two or more kinds may be mixed and used.
In addition to the above, plasticizers, pigments, dyes,
It is also possible to appropriately add a flame retardant, a defoaming agent, a dispersant, a surface modifier, a water adsorbent and the like.

Then, the polyester polyol and the polyisocyanate compound used as the raw materials are mixed with these two components while being heated to about 80.degree. After that, this is poured into a mold heated to 60 to 170 ° C. to cause a urethanization reaction at 80 to 170 ° C. for 30 to 300 minutes. Then, the shape memory resin is obtained by returning this to normal temperature and taking it out from the mold. This composition can be used as it is, but the shape in the deformed state can be memorized by firing at 120 ° C. or higher for 2 hours or more in the deformed state.

The shape memory composition thus obtained has a light brown transparent and uniform appearance at room temperature.
Hardness (HS) 70 or more, tensile strength 200 kg / c
m ² , tensile elongation of 300% or more, tear strength of 35 kg /
It is a tough plastic of cm or more. In addition, this test method was performed based on JIS K6301.

This shape-memory composition is capable of three-dimensional deformation when heated to a predetermined temperature to be deformed, and the shape changed when the temperature is lowered below the predetermined temperature while changing the shape. Is maintained as it is, and has a property of recovering the original shape when the temperature is again raised to a predetermined temperature or higher. Therefore, when this composition is applied by being attached to a predetermined object in a state of being lowered to a temperature lower than a predetermined temperature while changing its shape, when the target object exceeds a predetermined temperature state, the original Since the shape is restored, it can be used as a sensor or the like that can visually detect whether or not the object has reached a predetermined temperature.

Alternatively, if the function of recovering the original shape when the temperature exceeds a predetermined temperature is used for the switch operation, it may be used as a temperature sensitive switch that is activated or disconnected when the temperature reaches a predetermined temperature. Be done.

[0024]

EXAMPLES Examples of the present invention will be described below. Examples 1-11

[0025]

[Table 1]

A polyester polyol shown in

[0027]

[Table 2]

The polyisocyanate compounds shown in Table 3 and Table 3
According to the prescription, the polyester polyol and the polyisocyanate compound are separately added under vacuum to each other.
It was heated to 0 ° C. and degassed, after which both components were mixed in a homogenizer at 3,000 rpm. Then, the mixed solution was defoamed again in vacuum. Furthermore, this mixture was cast into an open mold having a thickness of 2 mm and having a thickness of 200 mm × 200 mm, which had been heated to 80 ° C. in advance, left at 150 ° C. for 5 hours, then demolded, and then at room temperature for 7 hours
A sheet-shaped resin was obtained by curing for a day.

The resin having a thickness of 2 mm thus obtained was subjected to the following tests. The results are shown in Tables 3 and 4.

[0030]

[Table 3]

[0031]

[Table 4]

In this table, [two-dimensional shape memory]
Is a state in which a sample adjusted to a width of 5 mm and a length of 100 mm at normal temperature is immersed in hot water at 80 ° C. for 2 minutes and then immediately folded in half at 180 ° in the center of the length direction and fixed in its original shape. It was air-cooled for 60 minutes. Then, the force for fixing the shape was removed, and the angle of the folded portion after being left for 7 days was measured and displayed as [shape fixability (unit degree)]. That is, it means that a perfect shape retention is exhibited at an angle of 0 degree and no shape retention is achieved at an angle of 180 degrees.
Then, the sample was immersed again in hot water at 80 ° C. for 2 minutes, and then the angle of the folded portion was measured and displayed as [shape recovery property (unit degree)]. That is, it means perfect shape recovery at an angle of 180 degrees. Also, [3D shape memory] is
Similarly to the above, the sample was treated in hot water, immediately stressed at both ends in the longitudinal direction to extend the length to about 300 mm, and air-cooled for 60 minutes in that state. The ratio (%) of the residual length to the extension length after leaving for 7 days, excluding the force applied to the deformation, was expressed as [shape fixability (unit%)]. [Shape deformability] is indicated as good if it is stretched to a length of about 300 mm under stress, and as bad if it has a trouble such as breakage before stretching of about 300 mm. Subsequently, the stretched sample was immersed again in hot water, and the ratio (%) of the sample length after re-immersion to the sample length before the test was expressed as [shape recovery (unit%)]. And, [tensile strength] and [tensile elongation] are JIS K
According to 6301, it is the numerical value of the result measured using the dumbbell No. 3.

Comparative Examples 1 to 5 Polyurethane resin sheets shown in Table 5 and liquid modified MDI listed in Table 2 were used to prepare polyurethane resin sheets in the same manner as in the above-mentioned Examples. Manufactured. The same evaluations and measurements as those in Examples were carried out, and the results are shown in Table 6.

[0034]

[Table 5]

[0035]

[Table 6]

Comparative Example 6 100 parts by weight of a propylene oxide adduct of glycerin (OH value 400) as a polyol component and 112 parts by weight of the liquid modified MDI shown in Table 2 as a polyisocyanate component were separately degassed under vacuum. Then, after that, both the components were 3,000 rpm in the presence of 0.3 part by weight of N, N-tetramethylhexamethylenediamine as a catalyst.
Mix with a minute homogenizer. Then, the mixed solution was defoamed again in vacuum. Furthermore, this mixture has a thickness of 2 m.
The sheet-shaped resin was cast into a 200 mm × 200 mm open mold previously heated to 80 ° C., left at 80 ° C. for 5 hours, then demolded, and subsequently cured at room temperature for 7 days. Got When the same evaluation and measurement as those in Examples were carried out, a result of [shape fixability] in [two-dimensional shape memory] of an angle of 180 degrees and [shape recovery] of 0 degree was obtained. It was confirmed to be an excellent shape memory resin in the dimensional deformation range. However, regarding the [shape deformability] in the [three-dimensional shape memory], it was determined that the resin broke at an elongation of about 20 to 30% and was impossible.
That is, the resin according to this comparative example is excellent in the two-dimensional shape memory property due to simple deformation such as bending and twisting, but does not have the three-dimensional shape memory property accompanied by large deformation and minute deformation of the resin itself.
The [response temperature] is about 65 ° C and the tensile strength is 626 kg.
/ Cm ² , and the tensile elongation was 32%.

Example 12 The shape memory composition having a thickness of 2 mm obtained in Example 6 was
A prism having a width of 2 mm and a length of 20 mm was prepared, the sample was treated in hot water in the same manner as in Example 1, and immediately stress was applied to both ends in the longitudinal direction to extend the length to about 60 mm, and the sample was air-cooled as it was. The shape was fixed. We made a set by connecting the lever end of the leaf lever type micro switch Z-15GW2 (OMRON) fixed on the base with screws and the base part under the lever with both ends of this stretched structure by instant adhesive, When placed in an oven at 80 ° C., after about 7 seconds, the composition prism was restored to its original size (shape) and the microswitch was cut off. As a result, it becomes possible to provide a temperature sensor that senses that the ambient temperature has risen to 64 ° C. or higher and that accompanies a response operation.

[0038]

As described above, the composition according to the present invention can change the shape three-dimensionally at a specific temperature, and the shape can be changed three-dimensionally depending on the temperature condition. As a material having a function of changing the shape, for example, it can be used as a temperature sensor that can easily detect a change in the temperature state of a predetermined object by a shape change, or as a temperature sensor that is activated by a shape change. It is a composition that can be used for a wide range of purposes such as sex windows, fitness materials, toys, and the like.

Claims (3)

[Claims] 1. (a) General formula: (However, in the formula, m and n are integers of 4 or more, p
Represents a number greater than 0) and a (b) polyisocyanate compound as essential components, and is composed of a polyurethane resin reacted at 80 ° C. or higher, and a shape memory that responds thermally at a specific temperature as a boundary. Sex composition. 2. The shape memory composition according to claim 1, wherein the polyurethane resin is formed in a modified shape, a film shape or a sheet shape. 3. (a) General formula: (However, in the formula, m and n are integers of 4 or more, p
Represents a number greater than 0) and a (b) polyisocyanate compound as essential components, and is composed of a polyurethane resin reacted at 80 ° C. or higher, and a shape memory that responds thermally at a specific temperature as a boundary. Sensor using a conductive composition.