KR20100048661A - A shape memory polyurethane electrospun web and method for preparation of the same - Google Patents

Abstract

PURPOSE: Shape memory polyurethane electrospun web and a manufacturing method thereof are provided to improve applicability of the web as clothes such as sportswear or protective clothes etc by electrospinning materials under optimized conditions. CONSTITUTION: A manufacturing method of shape memory polyurethane electrospun web includes the following steps: synthesizing polyurethanes by mixing poly (ε - carprolactone diol)(PCL), 4,4'- diphenylmethane diisocyanate(MDI) and 1,4- butanediol(BD) with a molar ratio of 1:2~6:1~5; making a polyurethane solution for electrospinning by agitating and dissolving polyurethane in a solvent in which N,N- dimethylformamide(DMF) and tetrahydrofuran(THF) are mixed; and acquiring shape memory polyurethanes electrospun web by electrospinning the polyurethane solution of 4~7 weight%.

Description

Shape memory polyurethane electrospinning web and its manufacturing method {A SHAPE MEMORY POLYURETHANE ELECTROSPUN WEB AND METHOD FOR PREPARATION OF THE SAME}

The present invention relates to a shape memory polyurethane electrospun web and a method of manufacturing the same. More specifically, the present invention synthesizes the shape memory polyurethane by adjusting the molecular weight of the polyol, the type and ratio of the solvent, etc., and then electrospinning under optimum conditions (solution concentration, voltage, spinning distance, discharge amount of the solution, etc.). Thereby, a method for producing a shape memory polyurethane electrospun web that not only expresses an optimal shape memory effect but also has excellent thermal performance, comfort performance (breathability, moisture permeability, heat retention, etc.); And a shape memory polyurethane electrospun web produced by this method.

Along with the rapid rise of nanotechnology in the high-tech industry, much attention has been focused on the manufacturing technology of nanofibers having diameters of several nanometers to several hundred nanometers. Has been attracting attention.

Electrospinning can produce fibers of various diameters according to various spinning conditions such as voltage intensity, distance and angle between syringe tip and collector, discharge amount of solution, spinning temperature / humidity, etc. The equipment is relatively simpler than the nonwoven fabric manufacturing method of and can be applied to a wide range of polymer materials. Nanofiber materials constructed through electrospinning have resistance to fine particle transmission by nano-sized pores. In addition, it exhibits a breathability (breathability) that can structurally discharge the sweat and the like inside, there is a variety of advantages such as having a waterproof and windproof effect on the outside of the membrane and has a high air content to have thermal barrier properties.

'Shaping memory material' means a material having a capability of recovering from a shape temporarily stored by an external stimulus to an original shape. As such a shape memory material, a shape memory alloy, a shape memory polymer (polymer), and the like are known. 'Shaping memory effect' means that the shape memory material is made into a shape at a high temperature, stored in a shape, then cooled, and then deformed at a low temperature does not return to the original shape, but when heated above a certain temperature, it returns to the original shape. It means thin effect. The shape memory effect may be generated in response to heat, or may be generated by light or chemical reaction. Shape memory polymers (e.g. polynorborene, poly (isoprene-butadiene-styrene, polyurethane, polystyrene, etc.) are lighter than shape memory alloys, have a higher shape memory recovery rate, are easy to process, transparent and can be dyed. Shape memory polymers form a two-phase structure in which softening and curing can be reversibly repeated at fixed points and temperature changes that structurally prevent the flow of the polymer. Therefore, it is possible to recover residual strain at the time of temperature increase.

Shape memory polyurethane is a block copolymer composed of two different kinds of segments. These two segments have a structure in which phases are separated into soft and hard segments due to thermodynamic incompatibility. The physical properties of the polyurethane depend on the degree of phase separation and the phase separation form of the two segments. The soft segment has a low glass transition temperature (Tg) or a low melting point (Tm), and is flexible, so that in a normal relaxed state, the random coil is unoriented. The hard segment forms a rigid crystal lattice by interaction between the strong hydrogen bonds between the urethane bonds and the planar structure between the benzene rings to form a three-dimensional network structure by physical crosslinking. Therefore, it forms a discontinuous phase and prevents slipping between molecular chains when stretched, thereby providing stability, elasticity, and the like to the polyurethane. When stretched, the molecular chain of the soft segment in a random coil state becomes linear and elongates, and when the stretching force is removed, the soft segment is returned to its original length by entropy elasticity.

The shape memory polyurethane has a higher glass transition temperature (T _{g, hard} ) of the _hard segment than the glass transition temperature (T _{g, soft} ) of the soft segment. Polyurethane has the most active movement of all polymer chains at temperatures above its melting point (T _{m, hard} ). When it is cooled to the glass transition temperature (T _{g, hard} ) of the hard segment, the shape of the hard segment is stored by physical crosslinking. However, although the shape of the hard segment is stored between the glass transition temperature (T _{g, soft} ) of the _soft segment and the glass transition temperature (T _{g, hard} ) of the hard segment, the soft segment has a glass transition temperature (T _{g, soft} ). Because of the above temperature, it is fluid and still deforms into a temporary shape. Below the glass transition temperature (T _{g, soft} ) of the soft segment, the soft segment is also completely glassy, and the deformed shape is fixed as it is even when the external force is removed. Raising this back above the glass transition temperature (T _{g, soft} ) of the soft segment, the soft segment is free to move and is restored to its original length by entropy elasticity. As the physical segment of the hard segment is released, the stored shape of the polymer is erased.

Polyurethane, which is mainly used as a shape memory polymer, has a very low glass transition temperature of the soft segment. Therefore, in order to express a shape memory effect near room temperature, the glass transition temperature is controlled by adjusting the molecular weight of the soft segment or the ratio with the hard segment. There were attempts to ascend to the vicinity, but there were many difficulties.

Therefore, the inventors of the present invention, after a thorough study, the transition temperature is expressed at the melting point (T _{m, soft} ) of the soft segment, using PCL appearing at room temperature or more as a polyol, by adjusting the polyol molecular weight, solvent type and ratio, etc. After synthesizing urethane, electrospinning under optimal conditions (solution concentration, voltage, spinning distance, discharge volume of solution, etc.) not only produces the optimum shape memory effect, but also thermal performance and comfort performance (breathability, water resistance). , Shape-retaining polyurethane electrospinning web with excellent thermal insulation properties. Based on this, it can be expected to be applied to intelligent protective clothing or sportswear with a protective function.

The present invention not only expresses an optimal shape memory effect, but also provides a shape memory polyurethane electrospinning web excellent in thermal performance, comfort performance (breathability, moisture permeability, heat retention, etc.), and a manufacturing method thereof, thereby providing a protective function. It aims to make it possible to expect applicability to intelligent protective clothing or sportswear.

The present invention provides a method for producing a shape memory polyurethane electrospun web, comprising: (a) poly (ε-caprolactone diol) (PCL), 4,4'-diphenylmethane diisocyanate (MDI) and 1,4-butanediol ( Mixing BD) in a molar ratio of 1: 2 to 6: 1 to 5 to synthesize a polyurethane; (b) dissolving the polyurethane in a solvent in which N, N-dimethylformamide (DMF) and tetrahydrofuran (THF) are mixed at a ratio of 6: 4 to 4: 6 (v / v), followed by stirring Preparing a spinning polyurethane solution; And (c) electrospinning 4-7 wt% of the electrospun polyurethane solution under conditions of a voltage of 6-16 kV, a spinning distance of 5-20 cm, and a discharge amount of 1.0-2.5 ml / hour. It provides a method for producing a shape memory polyurethane electrospinning web comprising the step of obtaining a urethane electrospun web.

In the step (a), the molecular weight (Mw) of the poly (ε-caprolactone diol) (PCL) is preferably 2500 to 4500, more preferably 3000 to 4000, and most preferably 4000. Further, poly (ε-caprolactone diol) (PCL), 4,4'-diphenylmethane diisocyanate (MDI) and 1,4-butanediol (BD) were mixed in a molar ratio of 1: 2 to 6: 1 to 5 Preferably, poly (ε-caprolactone diol) (PCL), 4,4'-diphenylmethane diisocyanate (MDI) and 1,4-butanediol (BD) having a molecular weight of 4000 are 1: 6: 5. Most preferably mixed.

The polyurethane synthesized in the step (a) is preferably a ratio of the hard segment content to the soft segment content of 75 to 95: 5 to 25, and most preferably 92: 8. Do.

The solvent used in step (b) is preferably N, N-dimethylformamide (DMF) and tetrahydrofuran (THF) 6: 4-4: 6 (v / v), most preferably 5: Solvent mixed at a ratio of 5 (v / v). When DMF alone is used, the solvent is low in volatility, and the webs collected at the collector during electrospinning are not good. Therefore, by mixing DMF and THF in the same ratio, the excellent volatility of THF is used. You will get a web of.

 In the step (c), 4 to 7% by weight of the electrospun polyurethane solution is electrospun under the conditions of a voltage of 6 to 16 kV, a spinning distance of 5 to 20 cm and a discharge amount of 1.0 to 2.5 ml / hour. More preferably, 4-7 wt% of the electrospun polyurethane solution is electrospun under the conditions of a voltage of 9-16 kV, a spinning distance of 14-16 cm, and a discharge amount of 1.0-2.0 ml / hour. As a result, an optimal shape memory polyurethane electrospun web can be obtained.

The present invention also provides a shape memory polyurethane electrospun web produced by the method described above.

The shape memory polyurethane electrospun web according to the present invention has a pore size of 144 to 553 nm in a steady state, and a pore size of 153 to 807 nm when fixed by stretching 50% in both directions. The pore size was 149-605 nm.

Shape memory polyurethane electrospun web according to the present invention has a transition temperature (T _trans ) It is preferable that it is 35-40 degreeC, and it is still more preferable that it is 38-39 degreeC.

The shape memory polyurethane electrospun web according to the present invention preferably has a shape recovery of at least 90%, even more preferably at least 95%.

The shape memory polyurethane electrospun web according to the present invention is 9 to 10 cm 3 / cm 2 / s when the air permeability measured by the ASTM D737 method is in a steady state, and 30 cm 3 when it is fixed by stretching 50% in both directions. It is preferable that it is / cm <2> / s or more. In addition, the water vapor transmission rate of the shape memory polyurethane electrospun web measured by the ASTM E96 method increased from 2000 to 2400 g / ㎡ / 24 hours to 5800 to 5900 g / ㎡ / 24 hours when the temperature is raised from 20 ℃ to 40 ℃ Become; The water resistance of the shape memory polyurethane electrospun web measured by the ISO 811 method is preferably 30 to 80 cmWC.

Shape memory polyurethane electrospun web according to the present invention is a high temperature and high humidity environment (relative humidity (RH): 65%, temperature: 20 ℃ → 30 ℃ → 40 ℃) and a high temperature drying environment [relative humidity (RH): 10%, Temperature: 20 ° C-30 ° C-40 ° C], it is preferable that the temperature difference ΔT in the case of not insulated and insulated is at most 4 ° C or more, respectively.

Shape memory polyurethane electrospinning web according to the present invention is excellent in thermal performance, comfort performance (breathability, water resistance, heat retention, etc.), and especially in sportswear or extreme environments because it exhibits better thermal barrier properties in high temperature dry environment It can be applied in various ways.

Through the following examples will be described in more detail the present invention. However, the following examples are only for illustrating the present invention, and the scope of the present invention should not be construed as being limited to the following examples. Therefore, it will be understood by those skilled in the art that various modifications, modifications and applications of the following embodiments are possible within the scope of the technical idea derived from the matters described in the appended claims.

Example

Preparation of Electrospun Polyurethane Solution

Poly (ε-caprolactone diol) (PCL) having a molecular weight of 4000, 4,4'-diphenylmethane diisocyanate (MDI) and 1,4-butanediol (BD) were mixed in a molar ratio of 1: 6: 5, Polyurethane was synthesized in which the ratio of the content of the segment to the content of the soft segment was 92: 8. Subsequently, after dissolving the polyurethane in a solvent in which N, N-dimethylformamide (DMF) and tetrahydrofuran (THF) were mixed at a ratio of 5: 5 (v / v), the solution was stirred by electrospinning polyurethane. Was prepared.

Electrospinning Under Optimum Conditions

While varying the concentration of the electrospun polyurethane solution, the concentration range suitable for electrospinning was found, and the optimum electrospinning condition was found by adjusting the voltage, the spinning distance (the distance between the syringe tip and the collector), and the discharge amount of the solution.

The electrospinning conditions were adjusted while varying the concentration of the polyurethane solution from 4% to 8% by weight. Observation while adjusting the voltage for forming the electrospinning web of the 4 wt% solution confirmed that the electrospinning was possible at 6 kV. At 5%, 6%, 7%, and 8% by weight, electrospinning began at 7 kV, 9 kV, 10 kV, and 11 kV, respectively. . The optimum voltages for the concentrations of the solutions were 9 kV, 10 kV, 14 kV and 16 kV at 4%, 5%, 6%, and 7% by weight, respectively. Could get. At a voltage lower than the optimum voltage of the solution, a non-uniform, slightly agglomerated web appeared, and at higher voltages, the solution bounced or beads were generated. Beads generated in the electrospinning web have a major influence on the voltage, and in addition, the formation of the beads is different depending on the concentration of the solution and the type of the solvent.

The optimum discharge amount according to the concentration of the solution was 1.0 ml / hour, 1.5 ml / hour, 2.0 ml / hour and 2.0 ml / hour in 4 wt%, 5 wt%, 6 wt% and 7 wt% solutions, respectively. When the amount of discharge of the solution increases even after electrospinning at the proper voltage according to the concentration of the solution, all the discharged solution does not form a web on the web while the electrospun solution is collected on the collector. Form appeared. This was more pronounced when electrospinning a low viscosity 4 wt% solution.

The distance between the syringe tip and the collector was adjusted in the range of 10-20 cm. In the case of 10 cm, the amount of fibers gathered in the collector was large, but the amount of the solution splashed by the voltage was limited to obtain a relatively uniform web. . Therefore, the distance between the syringe tip and the collector within 15 cm was selected as the optimum condition.

On the other hand, the solution of more than 8% by weight was shown to be a concentration unsuitable for electrospinning because the viscosity increased rapidly and spun in a very thick and non-uniform form.

Performance of Shape Memory Polyurethane Electrospun Web

Experiments were performed on the performance of shape memory polyurethane electrospun webs formed by spinning under the optimal conditions mentioned above.

● Transition temperature (T _trans )

Differential Scanning Calorimetry (DSC) was used to measure the thermal behavior of shape memory polyurethane electrospun webs. The shape memory polyurethane electrospun web showed an endothermic peak at 38.16 ° C. In addition, as the temperature rises continuously, a more inclined curve in the endo direction of the heat flow is shown. In particular, the nanofibers have a better crystallization and orientation in the process of forming the nanoweb, the transition temperature and the heat of fusion was thought to be high.

● Shape memory effect

The shape memory polyurethane electrospun webs had a shape recovery of more than 95% due to the development of the orientation of the hard segments. However, shape-memory polyurethane electrospun webs have a relatively low strain retention of 66% because of their nano-sized, thin fibrous mesh structure.

● pore

The shape-memory polyurethane electrospun web had an average pore diameter of 346 nm under normal conditions, an average pore diameter of 478 nm when immobilized by 50% stretching in both directions, and an average pore diameter of 382 nm when recovered. It was.

● Air permeability, moisture permeability and water resistance

The shape memory polyurethane electrospun web was 9.5 cm 3 / cm 2 / s when the air permeability measured by the ASTM D737 method was in a steady state, and was 30 cm 3 / cm 2 / s or more when the sheet was stretched and fixed by 50% in both directions. .

The water vapor transmission rate measured by the ASTM E96 method increased from 2000 to 2400 g / m 2/24 hours to 5800 to 5900 g / m 2/24 hours when the temperature was raised from 20 ° C. to 40 ° C. In case of fixation by 50% extension in both directions, pore size increases and vapor pressure increases due to temperature increase, and the moisture permeability increases. However, the elongated electrospun web passes through the transition temperature of 38 ° C. Since it recovers more than 95% while shrinking to its original shape, it did not show a big difference with the electrospun web not stretched at 40 ° C.

On the other hand, the water resistance of the shape memory polyurethane electrospun web measured by the ISO 811 method was relatively low in the range of 30 ~ 80 cmWC. However, it was thought that water resistance could be greatly improved if fabrics were used together with the floor fabrics in actual garments.

● thermal insulation

Using the apparatus for evaluating thermal barrier properties as shown in Figure 5, the thermal barrier properties in the high temperature and high humidity and high temperature drying environment was evaluated.

The inside of the chamber and the inside of the insulation box are kept the same at a temperature of 20 ° C. and a relative humidity of 65% (RH), then the relative humidity (RH) of the chamber is maintained at 65% and the temperature is raised to 30 ° C. and 40 ° C. The change in temperature inside the insulation box was measured. When it heated up at 30 degreeC, the temperature difference ((DELTA) T) when the insulation box was cut off and it was not cut off showed about 2 degreeC at maximum. Moreover, when it heated up at 40 degreeC, the temperature difference ((DELTA) T) when the insulation box was interrupted | blocked and not interrupted appeared about 4 degreeC at most.

 The inside of the chamber and the inside of the insulation box are kept the same at a temperature of 20 ° C. and 65% relative humidity (RH), and then the chamber is kept at a relative humidity (RH) of 65% to 10% and the temperature is maintained at 30 ° C., 40%. The change in the temperature inside the insulation box was measured while increasing to ℃. When it heated up at 30 degreeC, the temperature difference ((DELTA) T) when the insulation box was cut off and it was not cut off showed about 2.5 degreeC at maximum. Moreover, when it heated up at 40 degreeC, the temperature difference ((DELTA) T) when the insulation box was interrupted | blocked and not interrupted appeared about 4 degreeC at most.

Therefore, it was confirmed that the shape memory polyurethane electrospinning web has a function of blocking heat from the outside in an active and active manner while maintaining moisture permeability by adjusting the pore size according to the environmental temperature. In particular, it had better thermal barrier performance in hot and dry environments. Therefore, it is expected that the present invention can be applied to various kinds of sportswear or firewalls in extreme environments.

1 is a process chart for the production of shape memory polyurethane electrospun web of the present invention.

2 is a general stress-stain curve for measuring shape memory effects.

3 illustrates an apparatus for evaluating thermal insulation.

4 shows a chamber internal temperature / humidity control system in the apparatus of FIG. 3.

FIG. 5 shows a 600x magnification of a video microscope image at optimum conditions for various concentrations of shape memory polyurethane solutions.

6 is a graph showing the relationship between the optimal voltage and the heat flow of various concentrations of shape memory polyurethane solutions.

FIG. 7 is a scanning electron micrograph at a magnification of 2000 times a shape memory polyurethane electrospun web prepared by electrospinning a 4 weight% shape memory polyurethane solution under optimum conditions.

8 is a graph showing the pore diameter distribution of the shape memory polyurethane electrospun web.

9 is a graph showing the air permeability of the sample.

10 is a graph showing the moisture permeability according to the temperature of the shape memory polyurethane electrospun web.

11 is a graph showing the water resistance of the sample.

12 is a graph showing the thermal barrier properties of a sample at a temperature of 30 ° C. and a relative humidity (RH) of 65%.

FIG. 13 is a graph showing the thermal barrier properties of a sample at a temperature of 40 ° C. and a relative humidity (RH) of 65%.

14 is a graph showing the thermal barrier properties of a sample at a temperature of 30 ° C. and a relative humidity (RH) of 10%.

15 is a graph showing the thermal barrier properties of a sample at a temperature of 40 ° C. and a relative humidity (RH) of 10%.

Claims (12)

(a) Poly (ε-caprolactone diol) (PCL), 4,4'-diphenylmethane diisocyanate (MDI) and 1,4-butanediol (BD) in a molar ratio of 1: 2-6: 1-5 Synthesizing the polyurethane by mixing; (b) dissolving the polyurethane in a solvent in which N, N-dimethylformamide (DMF) and tetrahydrofuran (THF) are mixed at a ratio of 6: 4 to 4: 6 (v / v), followed by stirring Preparing a spinning polyurethane solution; And (c) shape-memory polyurethane by electrospinning 4-7% by weight of an electrospun polyurethane solution under conditions of a voltage of 6-16 kV, a spinning distance of 5-20 cm and a discharge amount of 1.0-2.5 ml / hour. A method of producing a shape memory polyurethane electrospun web, comprising the step of obtaining an electrospun web. The method of claim 1, The molecular weight of said poly (ε-caprolactone diol) (PCL) is 2500-4500, The manufacturing method of the shape memory polyurethane electrospinning web characterized by the above-mentioned. The method of claim 1, Polyurethane synthesized in the step (a) is a shape memory polyurethane electrospinning, characterized in that the ratio of the content of the hard segment (soft segment) and the content of the soft segment (75-95: 5-25) Method of making the web. The method of claim 1, Shape memory polyurethane, characterized in that in the step (b) N, N- dimethylformamide (DMF) and tetrahydrofuran (THF) is a solvent mixed in a ratio of 5: 5 (v / v) Method of making a spinning web. The method of claim 1, In the step (c), 4 to 7% by weight of the electrospun polyurethane solution is electrospun under the conditions of a voltage of 9 to 16 kV, a spinning distance of 14 to 16 cm, and a discharge amount of 1.0 to 2.0 ml / hour. Method of producing a shape memory polyurethane electrospun web. Shape-memory polyurethane electrospun web prepared according to the method of any one of claims 1 to 5. The method of claim 6, The shape memory polyurethane electrospun web has a pore size of 144 to 553 nm in a steady state and a pore size of 153 to 807 nm when it is fixed by stretching 50% in both directions. Shape memory polyurethane electrospinning web, characterized in that the size of 149 ~ 605 nm. The method of claim 6, The transition temperature (T _trans ) of the shape memory polyurethane electrospun web is Shape memory polyurethane electrospinning web, characterized in that 35 ~ 40 ℃. The method of claim 6, Shape recovery of the shape memory polyurethane electrospun web (shape recovery) is 90% or more shape memory polyurethane electrospinning web, characterized in that. The method of claim 6, The air permeability of the shape-memory polyurethane electrospun web measured by the ASTM D737 method is 9 to 10 cm 3 / cm 2 / s in the steady state, and 30 cm 3 / cm 2 / Shape memory polyurethane electrospinning web, characterized in that more than s. The method of claim 6, The water vapor transmission rate of the shape memory polyurethane electrospun web measured by the ASTM E96 method was increased from 2000 to 2400 g / m 2/24 hours to 5800 to 5900 g / m 2/24 hours when the temperature was raised from 20 ° C. to 40 ° C .; The shape memory polyurethane electrospinning web characterized in that the water resistance of the shape memory polyurethane electrospun web measured by the ISO 811 method is 30 ~ 80 cmWC. The method of claim 6, In a high temperature and high humidity environment [relative humidity (RH): 65%, temperature: 20 ° C. → 30 ° C. → 40 ° C.] and a high temperature drying environment [relative humidity (RH): 10%, temperature: 20 ° C. → 30 ° C. → 40 ° C.] The shape memory polyurethane electrospinning web, characterized in that the temperature difference (ΔT) of the shape memory polyurethane electrospinning web when not insulated and when insulated is at most 4 ℃.

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