The invention comprises the following steps:
the invention aims to provide a high molecular silica gel taking siloxane-based polyurethane as a matrix and a preparation method thereof, and aims to obtain the silica gel which can ensure water absorption, moisture permeability and oxygen permeability.
In order to achieve the above purpose, the present invention adopts the following technical scheme: a high-molecular silica gel using siloxane polyurethane as matrix is prepared from polyhydroxy polyethanediol derivative, polyethanediol, polyisocyanate, polydimethyl siloxane and chain extender.
The preparation method of the silica gel of the invention comprises the following steps: reacting polyhydroxy polyethylene glycol derivative with polyethylene glycol, polyisocyanate and the like to obtain a polyurethane elastomer; and adding polysiloxane and a chain extender to finally obtain the high molecular silica gel taking siloxane polyurethane as a matrix.
The preparation method of the polyhydroxy polyethylene glycol derivative comprises the following steps: the polyethylene glycol reacts with epoxy chloropropane to obtain epoxy group end capped polyethylene glycol glycidyl ether, and the polyethylene glycol is subjected to ring opening under the catalysis of acid to generate polyhydroxy polyethylene glycol derivatives.
According to the invention, a part of polyethylene glycol is converted into a polyethylene glycol derivative containing a plurality of hydroxyl groups, and the derivative is used as a cross-linking agent, so that the increase of hydrophilic polyethylene glycol chain segments in a cross-linked network is ensured, the water absorption and the water vapor transmittance are greatly improved, and the constructed large cross-linked network is endowed with a larger degree of freedom for the polydimethylsiloxane chain segments, so that the obtained silica gel can achieve excellent balance of water absorption, water vapor transmittance and oxygen transmittance. The invention has simple scheme, cheap raw materials and certain adjustability.
Specifically, the technical scheme of the invention comprises the following steps:
adding polyhydroxy polyethylene glycol derivative and polyethylene glycol, stirring, heating to 90-130 deg.C, vacuum dewatering, and cooling to 40-60 deg.C; then, dropwise adding polyisocyanate, adding an organotin catalyst after dropwise adding, reacting a reaction system at 70-90 ℃ for 2-4 hours, adding polydimethylsiloxane, a chain extender and a solvent, continuously stirring and reacting for 6-8 hours, then introducing into a polytetrafluoroethylene mould for paving, putting the mould into a vacuum dryer, vacuumizing and defoaming for 0.5-1 hour, and then solidifying at a constant temperature of 50-70 ℃ for 8-12 hours to obtain the high polymer silica gel taking siloxane polyurethane as a matrix.
The preparation method of the polyhydroxy polyethylene glycol derivative specifically comprises the following steps: under the action of quaternary ammonium salt catalyst and sodium hydroxide, polyethylene glycol and epoxy chloropropane react for 2-4 hr at 40-60 deg.c to obtain epoxy group end capped polyethylene glycol glycidyl ether, deionized water and concentrated sulfuric acid are added to regulate pH value to acidity, ring opening reaction is performed at room temperature for 2-4 hr, sodium carbonate is used to regulate to neutrality, vacuum distillation is performed, the distilled product is filtered to eliminate precipitate, and the product is dried at 110-130 deg.c for 2-4 hr to obtain polyhydroxy polyethylene glycol derivative.
Preferably, in the process of preparing the polyhydroxy polyethylene glycol derivative, the quaternary ammonium salt catalyst is one or more of benzyl triethyl ammonium chloride, tetrabutylammonium bromide, tetrabutylammonium chloride and tetrabutylammonium bisulfate.
For the purposes of the present invention, it is preferred that the molar ratio of polyethylene glycol, polyisocyanate, polydimethylsiloxane, chain extender is 1: (3-5): (0.5-1.5): (0.2-1); the mass ratio of polyethylene glycol to polyhydroxy polyethylene glycol derivative is (5-25): 1, a step of; the mass ratio of polyisocyanate to organotin catalyst is 100: (0.5-2); the mass ratio of the polydimethylsiloxane to the solvent is 1: (1-3).
Preferably, in the process of preparing the polyhydroxy polyethylene glycol derivative, the molar ratio of polyethylene glycol, epichlorohydrin, sodium hydroxide and quaternary ammonium salt catalyst is 1: (1.5-3): (1.5-3): (0.005-0.05).
Preferably, the polyethylene glycol has a molecular weight of 400 to 3000g/mol, more preferably 1000 to 2000g/mol.
Preferably, the polydimethylsiloxane is one or more of hydroxyl-terminated polydimethylsiloxane and amino-terminated polydimethylsiloxane; the molecular weight is 1000-6000g/mol, wherein the molecular weight is more preferably 1000-3000g/mol.
Preferably, the polyisocyanate is one or more of isophorone diisocyanate (IPDI), 1, 6-Hexamethylene Diisocyanate (HDI), toluene Diisocyanate (TDI), diphenylmethane-4, 4' -diisocyanate (MDI).
Preferably, the chain extender is one or more of 1, 4-butanediol, diethylene glycol, ethylene glycol, and 1, 4-cyclohexanediol.
Preferably, the solvent is one or more of tetrahydrofuran, acetone, toluene, dimethyl sulfoxide and chloroform.
Preferably, the organotin catalyst is one or more of dibutyltin dilaurate, stannous octoate, dibutyltin diacetate and stannous oleate.
Compared with the prior art, the invention has the following beneficial effects:
the invention converts partial polyethylene glycol into polyethylene glycol derivative containing polyhydroxy, and takes the derivative as a cross-linking agent, the swelling degree of the prepared silica gel is above 130%, and the water vapor permeability is 28g/m2 The oxygen permeability coefficient is 140 multiplied by 10 < -11 > cm above/h3 ·cm/(cm2 s.mmHg) or more, and an effective balance of water absorption, water vapor permeability and oxygen permeability can be sufficiently ensured.
The specific embodiment is as follows:
in order to make the purposes, technical solutions and advantages of the implementation of the present invention more clear, the technical solutions of the present invention are further described below by means of specific embodiments. Those skilled in the art should appreciate that the examples are only for aiding in understanding the technical contents and effects of the present invention and should not be construed as limiting the present invention.
Production example 1
Mixing 0.2mol (400 g) of polyethylene glycol-2000 (PEG-2K) with 0.4mol (37 g) of epichlorohydrin, adding 0.005mol (1.1 g) of benzyl triethyl ammonium chloride and 0.4mol (16 g) of sodium hydroxide, reacting at 55 ℃ for 2 hours to obtain epoxy group-terminated polyethylene glycol glycidyl ether, adding deionized water and concentrated sulfuric acid, adjusting the pH value to 5, carrying out ring-opening reaction at room temperature for 3 hours, adjusting to neutrality by sodium carbonate, carrying out reduced pressure distillation at 90 ℃ and vacuum degree of 0.085MPa, carrying out suction filtration to remove sediment, and weighing to obtain 375.14g of polyhydroxy polyethylene glycol derivative. The molecular weight of the polyhydroxy polyethylene glycol derivative is about 2150g/mol according to the structure calculation, and about 0.174mol of the product is obtained.
Production example 2
Mixing 0.2mol (200 g) of polyethylene glycol-1000 (PEG-1K) with 0.6mol (55.5 g) of epichlorohydrin, adding 0.005mol (about 1.6 g) of tetrabutylammonium bromide and 0.5mol (20 g) of sodium hydroxide, reacting at 45 ℃ for 4 hours to obtain epoxy group-terminated polyethylene glycol glycidyl ether, adding deionized water and concentrated sulfuric acid, adjusting the pH value to 5.5, carrying out ring-opening reaction at room temperature for 4 hours, adjusting to be neutral by sodium carbonate, distilling at 90 ℃ under vacuum degree of 0.085MPa under reduced pressure, filtering out suction filtration to remove sediment, drying at 110 ℃ for 4 hours, and weighing to obtain 192.46g of polyhydroxy polyethylene glycol derivative. The molecular weight of the polyhydroxy polyethylene glycol derivative is about 1150g/mol according to the structure calculation of the obtained polyhydroxy polyethylene glycol derivative, and the product of about 0.167mol is obtained.
Example 1
Uniformly stirring 40g of polyhydroxy polyethylene glycol derivative prepared in preparation example 1 and 0.4mol (800 g) of polyethylene glycol (PEG-2K), heating to 110 ℃, dehydrating in vacuum, and reducing the temperature to 50 ℃; then, 1.6mol (278.4 g) of toluene diisocyanate was added dropwise, after the completion of the dropwise addition, 2.5g of dibutyltin dilaurate was added, the reaction system was allowed to react at 70℃for 4 hours, then 0.3mol (300 g) of an amino-terminated polydimethylsiloxane (molecular weight: 1000), 0.3mol (18.6 g) of ethylene glycol, and 900g of acetone were added, the reaction was continued for 6 hours with stirring, and then the mixture was introduced into a polytetrafluoroethylene mold and laid flat, the mold was placed in a vacuum drier, and after the vacuum degassing treatment for 1 hour, the mixture was cured at a constant temperature of 60℃for 10 hours, to obtain a polymer silicone gel having a silicone-based polyurethane as a matrix.
Example 2
Uniformly stirring 20g of polyhydroxy polyethylene glycol derivative prepared in preparation example 2 and 0.2mol (100 g) of polyethylene glycol (PEG-1K), heating to 130 ℃, dehydrating in vacuum, and reducing the temperature to 60 ℃; then, 0.6mol (133.2 g) isophorone diisocyanate was added dropwise, 1.5g dibutyltin dilaurate was added after the completion of the dropwise addition, the reaction system was allowed to react at 90℃for 2 hours, then 0.2mol (400 g) hydroxyl-terminated polydimethylsiloxane (molecular weight: 2000), 0.05mol (4.5 g) 1, 4-butanediol, 600g tetrahydrofuran were added, the reaction was continued for 8 hours with stirring, and then the mixture was introduced into a polytetrafluoroethylene mold and laid flat, the mold was placed in a vacuum dryer, and after the evacuation and deaeration treatment for 0.5 hour, the mixture was cured at a constant temperature of 70℃for 8 hours, to obtain a polymer silicone gel based on a silicone-based polyurethane.
Example 3
Based on example 1, 0.4mol (800 g) of polyethylene glycol (PEG-2K) was replaced with 0.4mol (320 g) of polyethylene glycol-800 (PEG-800), the remaining conditions being unchanged.
Example 4
Based on example 2, 0.2mol (400 g) of hydroxy-terminated polydimethylsiloxane (molecular weight 2000) was replaced by 0.2mol (600 g) of hydroxy-terminated polydimethylsiloxane (molecular weight 3000), with the remaining conditions unchanged.
Comparative example 1
Based on example 1, no polyhydric polyethylene glycol derivative was added, the remaining conditions being unchanged.
Comparative example 2
Based on example 1, the curing conditions in the mold were changed to: moisture curing in air at room temperature for 24 hours, then moving to an oven, and continuously curing at 60 ℃ for 24 hours to obtain high polymer silica gel taking siloxane-based polyurethane as a matrix; the remaining conditions were unchanged.
Comparative example 3
Based on example 2, the amount of the polyhydric polyethylene glycol derivative was adjusted to 35g, and the remaining conditions were unchanged.
Comparative example 4
Based on example 2, the polyhydric polyethylene glycol derivative was replaced by 0.017mol (2.3 g) of pentaerythritol, the remaining conditions being unchanged.
Under the reaction conditions in comparative example 1, a crosslinked network was not completely formed, and therefore, there was no silica gel product having a certain mechanical strength, which was not subjected to the test of swelling property and the like, and only the swelling property, oxygen permeability and moisture permeability of the silica gel in examples 1 to 4 and comparative examples 2 to 4 were respectively tested.
Specific test methods are shown below.
The swelling performance was tested by cutting the silica gel into 3 cylinders of 5mm diameter and 10mm length, immersing them in phosphate buffer solution of ph=7.4 at room temperature until their mass was unchanged, namely, their mass was mw, and then placing the water-absorbed samples in a vacuum oven at 50 ℃ to constant weight, namely, their mass was md. The swelling properties were calculated by the following formula and averaged:
SR(％)＝(mw–md)/md×100％
the oxygen permeability was measured by differential pressure method, and a sample having a diameter of 50mm and a thickness of 1mm was placed in an atmosphere having a temperature of 25℃and a relative humidity of 50% for 12 hours as prescribed in GB/T2918 before the measurement. The test conditions were: the temperature was 25℃and the relative humidity was 50%, the external pressure was atmospheric pressure, and the test time was 8 hours.
The moisture permeability is tested by a moisture permeability tester, and a sample with the diameter of 50mm and the thickness of 1mm is placed in an environment with the temperature of 25 ℃ and the relative humidity of 50% for 12 hours according to the specification in GB/T2918 before the test. Test conditions: the temperature is 37 ℃, the relative humidity is 90+/-2 percent, the pressure is atmospheric, and the test time is 4 hours.
The results of the test are shown in table 1.
TABLE 1 results of tensile Properties, swelling Properties, oxygen permeability Properties and moisture permeability Properties of examples and comparative examples
From the test results of examples 1 to 4, the swelling degree of the polymer silica gel prepared by the invention and taking the siloxane-based polyurethane as a matrix is above 130%, and the water vapor permeability is 28g/m2 The oxygen permeability coefficient is 140 multiplied by 10 above/h-11 cm3 ·cm/(cm2 s.mmHg) or more, and an effective balance of water absorption, water vapor permeability and oxygen permeability can be sufficiently ensured.
From the comparison between example 1 and comparative example 2, the crosslinking mode in comparative example 2 is moisture curing, NCO groups react with moisture in the air, a cured network formed by moisture curing is smaller than a cured network using polyhydroxy polyethylene glycol derivatives as a crosslinking agent, crystallization is easy to form, polyethylene glycol segments are absent from the cured segments, hydrophilic network is reduced, insufficient network construction deep and inside the gel is caused by moisture curing, and finally, the swelling degree and water vapor permeability are low as a whole. In addition, the cured network becomes smaller, so that the degree of freedom of the polydimethylsiloxane in the space becomes smaller, and the gas passing is adversely affected. The curing network is large, polyethylene glycol in the curing chain segment is more, and the degree of freedom of the polydimethylsiloxane is higher, so that the effective balance of water absorption, water vapor transmittance and oxygen permeability coefficient can be fully ensured.
From example 2 and comparative example 3, as the amount of the polyhydroxy polyethylene glycol derivative increases, the degree of crosslinking becomes higher, excessive concentration of the crosslinked network will not be favorable for permeation of water vapor, and also for free rotation of the polydimethylsiloxane segment, which will result in a decrease in water vapor permeability and oxygen permeability coefficient; in addition, too dense a crosslinked network also leads to a decrease in the water swelling rate.
From example 2 and comparative example 4, the addition of pentaerythritol having a similar hydroxyl number as a crosslinking agent to replace the polyhydric polyethylene glycol derivative causes problems of too small a cured network and a reduced hydrophilic segment, resulting in a decrease in water absorption, water vapor permeability and oxygen permeability coefficient.
In summary, according to the invention, by converting part of polyethylene glycol into the polyethylene glycol derivative containing a plurality of hydroxyl groups and using the derivative as the cross-linking agent, the increase of hydrophilic polyethylene glycol chain segments in a cross-linked network is ensured, so that the water absorption and the water vapor transmittance are greatly improved, and the constructed large cross-linked network ensures the greater degree of freedom of the polydimethylsiloxane chain segments, so that the obtained silica gel can achieve excellent balance of water absorption, water vapor transmittance and oxygen transmittance.
The present application is not limited to the above embodiment. The above embodiments are merely examples, and embodiments having substantially the same configuration and the same effects as those of the technical idea within the scope of the present application are included in the technical scope of the present application. Further, various modifications that can be made to the embodiments and other modes of combining some of the constituent elements in the embodiments, which are conceivable to those skilled in the art, are also included in the scope of the present application within the scope not departing from the gist of the present application.