CN108503783B

CN108503783B - Thermoplastic polyurethane elastomer and preparation method thereof

Info

Publication number: CN108503783B
Application number: CN201810320510.5A
Authority: CN
Inventors: 黄鹤; 徐自冲
Original assignee: Suzhou University
Current assignee: Changchun Fengtai Technology Co ltd; Huijiawang Tianjin Technology Co ltd
Priority date: 2018-04-11
Filing date: 2018-04-11
Publication date: 2021-07-13
Anticipated expiration: 2038-04-11
Also published as: CN108503783A

Abstract

The invention relates to a preparation method of a thermoplastic polyurethane elastomer, which comprises the following steps: dissolving aliphatic diisocyanate and low molecular weight dihydric alcohol into an organic solvent according to the molar ratio of 2-5:1, and reacting for 2-3h at 75-85 ℃ under the action of a catalyst to obtain a prepolymer; preferably, the reaction temperature is 75-80 ℃; slowly adding a micromolecular chain extender into the prepolymer at the temperature of 40-50 ℃, wherein the adding time is 6-12h, the molar ratio of the micromolecular chain extender to the aliphatic diisocyanate is 1-4:1, and continuously reacting at the temperature of 40-50 ℃ until the reaction is complete to obtain the thermoplastic polyurethane elastomer.

Description

Thermoplastic polyurethane elastomer and preparation method thereof

Technical Field

The invention relates to the technical field of polyurethane elastomer synthesis, in particular to a thermoplastic polyurethane elastomer and a preparation method thereof.

Background

Thermoplastic polyurethane elastomers are a class of block polymers containing an alternating sequence of hard blocks derived from the diisocyanate in the reactants and soft blocks predominantly of low molecular weight polyester polyols, polyether polyols or polycarbonate polyols. The hard segments may act as physical cross-linking points in the matrix, while the soft segments act to provide elasticity. By selecting proper proportion of soft segment and hard segment, the polyurethane elastomer product with specific application can be synthesized, and the polyurethane elastomer product is a high molecular material between rubber and plastic, and has wide application range.

Most polyurethane elastomers today are synthesized using aromatic isocyanates, such as MDI, TDI, and the like, where TDI is hazardous to health due to low vapor pressure. In addition, the polyurethane elastomer synthesized by the method is easy to yellow due to the characteristics of benzene rings. Generally, there are two main methods for preparing polyurethane elastomers, one-step and two-step methods. However, in the traditional two-step method, physical gel is easily formed in the system when the reaction is not complete, and the generation of gel cannot be avoided even if a strong polar solvent is selected, so that the content of a hard segment in a polyurethane elastomer chain segment is greatly limited, and the mechanical property of the product is not ideal enough.

Disclosure of Invention

In order to solve the technical problems and further improve the mechanical properties of products, the invention aims to provide the thermoplastic polyurethane elastomer and the preparation method thereof.

The preparation method of the thermoplastic polyurethane elastomer comprises the following steps:

(1) dissolving aliphatic diisocyanate and low molecular weight dihydric alcohol into an organic solvent according to the molar ratio of 2-5:1, and reacting for 2-3h at 75-85 ℃ under the action of an organic tin catalyst to obtain a prepolymer; preferably, the reaction temperature is 75-80 ℃;

(2) slowly adding a micromolecular chain extender into the prepolymer at the temperature of 40-50 ℃, wherein the adding time is 6-12h, the molar ratio of the micromolecular chain extender to the low molecular weight dihydric alcohol is 1-4:1, and continuously reacting at the temperature of 40-50 ℃ until the reaction is complete to obtain the thermoplastic polyurethane elastomer.

Further, in the step (1), nanoparticles modified with a silane coupling agent are mixed in the low molecular weight diol. By adding the nano particles modified by the silane coupling agent, because the nano particles have small particle size and more surface atoms, and have a plurality of dangling bonds with unsaturation property and are easy to combine with other atoms, the nano particles can be chemically bonded or physically entangled with polyurethane high polymer molecules, so that borne external force can be effectively transferred, the polyurethane elastomer can be reinforced and toughened, the tensile strength and the elongation at break of the polyurethane elastomer are improved, and the multiple can be increased by about 2 times.

Further, the ratio of the nano particles modified by the silane coupling agent to the low molecular weight dihydric alcohol is 0.08-0.15g:1mmol by mass and molar ratio respectively.

Further, the nano particles are one or more of nano zinc oxide, nano aluminum oxide and nano silicon dioxide.

Further, the silane coupling agent is one or more of KH550, KH560 and KH 570.

Further, the preparation method of the nano-particle modified by the silane coupling agent comprises the following steps:

dissolving a silane coupling agent in ethanol, adjusting the pH value to 3-4, hydrolyzing the silane coupling agent for 1-2h, adding the nanoparticles, mixing uniformly, performing coupling reaction at 75-85 ℃, and reacting for 4-8h to obtain the silane coupling agent modified nanoparticles.

Further, in the step (1), the aliphatic diisocyanate is one or more of isophorone diisocyanate, hexamethylene diisocyanate and dicyclohexylmethane diisocyanate. Preferably, the aliphatic diisocyanate is isophorone diisocyanate.

Further, in the step (1), the low molecular weight diol is one or more of poly adipic acid-1, 4-butanediol ester, poly adipic acid-1, 6-butanediol ester, poly epsilon-caprolactone, polycarbonate diol and polytetrahydrofuran ether diol. Preferably, the low molecular weight diol is a poly 1, 4-butylene adipate, a polycarbonate diol or a polytetrahydrofuran ether diol.

Further, the molecular weight of the low molecular weight dihydric alcohol is 1000-5000 g/mol. Preferably, the low molecular weight diol has a molecular weight of 1000 to 2000 g/mol.

Further, in the step (1), the organic solvent is N, N-dimethylacetamide.

Further, in the step (1), the organic tin catalyst is one or more of CT-E229, stannous octoate and dibutyltin dilaurate.

Further, in the step (2), the small molecule chain extender is one or more of 1, 4-butanediol, isophorone diamine, ethylene glycol and ethylene diamine. Preferably, the small molecule chain extender is 1, 4-butanediol or isophorone diamine.

Further, all the reactants need to be kept dry, so that the reaction system can be carried out under anhydrous conditions.

Further, the post-treatment of the thermoplastic polyurethane elastomer comprises the following steps:

(S1) adding the reaction product into excessive water for precipitation, washing and drying to obtain a flocculent product;

(S2) dissolving the flocculent product in a solvent, pouring the flocculent product into a mould for forming, and drying the flocculent product after the solvent is volatilized to obtain the thermoplastic polyurethane elastomer film.

Or, a hot press molding method may be adopted, in which the flocculent product obtained in the step (S1) is heated to be molten at a high temperature, and then is pressed flat by a weight directly to form a film.

Furthermore, the thermoplastic polyurethane elastomer can also be directly formed into a film, the reaction product is directly poured into a mould for forming, and after the solvent is volatilized, the thermoplastic polyurethane elastomer film is obtained after drying. Further, in the step (S2), the solvent is one or more of tetrahydrofuran, chloroform and methanol.

The invention also provides the thermoplastic polyurethane elastomer prepared by the preparation method, wherein the breaking strength of the thermoplastic polyurethane elastomer during stretching is 40-220MPa, and the breaking elongation is 320-1300%.

The thermoplastic polyurethane elastomer film obtained by the invention is subjected to performance test, the highest hard segment content is 52 percent, the highest tensile strength can reach 80MPa, and the elongation at break is 320-880 percent, which shows that the thermoplastic polyurethane elastomer film has excellent mechanical properties. When the low molecular weight dihydric alcohol is also mixed with the silane modified nano particles, the nano particle/polyurethane composite elastomer can be obtained, the tensile strength of the nano particle/polyurethane composite elastomer can reach 220MPa, the physical and mechanical properties of the nano particle/polyurethane composite elastomer are improved by 2-3 times compared with the mechanical properties of the polyurethane elastomer obtained without adding nano particles, the elongation at break can reach 750 minus 1300 percent, the tensile strength is improved, the elongation at break is also greatly improved, and the effect of simultaneously enhancing and toughening is achieved.

By the scheme, the invention at least has the following advantages:

1. the segmented polymer-polyurethane elastomer prepared by the method has high hard segment content in the chain segment, and a large amount of carbamate groups and carbamido groups capable of forming multiple hydrogen bonds with each other are introduced into the molecular chain, so that excellent mechanical properties can be effectively brought to the elastomer, the breaking elongation is greatly improved while the tensile strength is improved, and the effect of simultaneously enhancing and toughening is achieved.

2. The synthetic method of the invention fixes the dosage of the low molecular weight dihydric alcohol, the content of the hard segment can be changed by changing the dosages of the diisocyanate and the micromolecular chain extender, the content of the hard segment in the chain segment of the synthetic polyurethane elastomer exceeds 50 percent, and the occurrence of physical crosslinking is effectively prevented in the synthetic process.

3. The polyurethane elastomer synthesized by the invention does not contain benzene rings, is resistant to yellowing, and has good solvent resistance and weather resistance.

The foregoing description is only an overview of the technical solutions of the present invention, and in order to make the technical solutions of the present invention more clearly understood and to implement them in accordance with the contents of the description, the following detailed description is given with reference to the preferred embodiments of the present invention and the accompanying drawings.

Drawings

FIG. 1 is a schematic diagram of a route for preparing a polyurethane elastomer in example 1 of the present invention;

FIG. 2 is an infrared monitoring spectrum of the polyurethane elastomer preparation process in example 1 of the present invention;

FIG. 3 is a graph showing a tensile test of a polyurethane elastomer film in example 2 of the present invention;

FIG. 4 is a DMA storage modulus test plot of a polyurethane elastomer of example 2 of the present invention;

FIG. 5 is a DSC plot of the polyurethane elastomer of example 2 of the present invention;

FIG. 6 is a graph of the DMA loss tangent test for the polyurethane elastomer of example 2 of the present invention;

FIG. 7 is a thermogravimetric analysis of a polyurethane elastomer in example 2 of the present invention;

FIG. 8 is a graph of a tensile test of the nanoparticle/polyurethane composite elastomer film prepared in example 4 of the present invention.

Detailed Description

The following detailed description of embodiments of the present invention is provided in connection with the accompanying drawings and examples. The following examples are intended to illustrate the invention but are not intended to limit the scope of the invention.

Example 1

FIG. 1 is a schematic diagram showing a route for preparing a polyurethane elastomer in this example, wherein the compound of formula (1) represents polytetrahydrofuran ether diol, the compound of formula (2) represents isophorone diisocyanate, the compound of formula (3) represents an isocyanate (NCO) -terminated prepolymer, black circles in the drawing represent urethane groups, and black boxes represent urea groups. The specific synthesis steps are as follows:

after polytetrahydrofuran ether dihydric alcohol with the molecular weight of 1000g/mol is dehydrated for 2 hours in vacuum at 120 ℃, 1mmol of dried polytetrahydrofuran ether dihydric alcohol and 5mL of N, N-dimethylacetamide are put into a four-neck flask, under the protection of nitrogen, 2mmol of isophorone diisocyanate and 0.1-0.2% of dibutyltin dilaurate (based on the mass of the polytetrahydrofuran ether dihydric alcohol) are added, the temperature is kept at 60 ℃, the mixture is stirred at a constant speed for 10 minutes and then heated to 75 ℃ for reaction for 3 hours, isocyanate-terminated prepolymer is obtained, and then the temperature is reduced to 50 ℃.

Dissolving 1mmol of isophorone diamine in N, N-dimethylacetamide, adding into a syringe, slowly injecting the solution into the system within 6 hours, continuing to react at 50 ℃, and simultaneously tracking the change condition of isocyanate groups in the reaction process by adopting a Fourier infrared spectrometer. When the peak of the isocyanate group observed in the infrared spectrogram basically disappears, the reaction is finished. Then adding the reacted solution into excessive water for precipitation, washing and drying to obtain a cotton-shaped product, and putting the cotton-shaped product into a dryer for later use.

The embodiment is characterized in that: excessive alicyclic diisocyanate is used to synthesize a polyurethane prepolymer, and then diisocyanate at two ends of the polyurethane prepolymer reacts with a micromolecular chain extender diamine to carry out chain extension to obtain the linear macromolecular polyurethane elastomer.

The polyurethane elastomer film is prepared by a solution casting method. Dissolving a small amount of cotton-like products in methanol, pouring into a rectangular polytetrafluoroethylene mold, putting into a vacuum drying oven for drying at 40 ℃ for 12h after the methanol is volatilized completely, and finally obtaining the polyurethane elastomer film. The thermoplastic elastomer prepared by the method can be dissolved in various solvents and has excellent processing performance.

FIG. 2 is an IR spectrum of the polyurethane elastomer of this example taken from the top down, the IR spectra measured by sampling at the start of the reaction, at 2 hours, 5 hours, 7 hours, 9 hours and 12 hours, respectively, from-NCO group (2275 cm)^-1) The reaction was judged to be complete by the disappearance of (D).

Example 2

Carrying out vacuum dehydration on polycarbonate diol with the molecular weight of 2000g/mol at 120 ℃ for 2h, taking 1mmol of dried polycarbonate diol and 5mL of N, N-dimethylacetamide, adding 5mmol of isophorone diisocyanate and 5 muL of catalyst dibutyltin dilaurate in a four-neck flask under the protection of nitrogen, keeping the temperature at 60 ℃, uniformly stirring for 10min, heating to 80 ℃ for reaction for 2h to obtain an isocyanate-terminated prepolymer, and cooling to 50 ℃.

4mmol of isophorone diamine is dissolved in 15mL of N, N-dimethylacetamide and added into a syringe, then the solution is slowly injected into the system within 8 hours, the reaction is continued at 50 ℃, and a Fourier infrared spectrometer is adopted to track the change of isocyanate groups in the reaction process. When the peak of the isocyanate group observed in the infrared spectrogram basically disappears, the reaction is finished. Then adding the reacted solution into excessive water for precipitation, washing and drying to obtain a cotton-shaped product, and putting the cotton-shaped product into a dryer for later use.

The polyurethane elastomer film is prepared by a solution casting method. Dissolving a small amount of cotton-like products in tetrahydrofuran, pouring into a rectangular polytetrafluoroethylene mold, putting into a vacuum drying oven for drying at 40 ℃ for 12 hours after methanol is volatilized completely, finally obtaining a polyurethane elastomer film, and then carrying out various performance tests.

FIG. 3 is a graph showing a tensile test of the polyurethane elastomer film, and it can be seen that the tensile strength is as high as about 80 MPa.

Fig. 4-7 are graphs illustrating thermodynamic tests of polyurethane materials provided in this example. The DMA storage modulus plot of the polyurethane material in fig. 4 shows its typical thermoplastic elastomer properties. The glass transition temperature of the elastomer is about-45 ℃ (fig. 5-6), which shows that the elastomer has excellent low temperature resistance. In the thermogravimetric curve (fig. 7), the thermal degradation temperature of the polyurethane elastomer at 5% weight loss was about 300 ℃, the temperature range at the maximum degradation rate was about 380 ℃, and the temperature at which flow started (about 170 ℃, fig. 4) was much lower than the decomposition temperature. This feature is very advantageous for the hot press forming.

Example 3

Vacuum dehydrating poly adipic acid-1, 4-butanediol ester with the molecular weight of 1000g/mol at 120 ℃ for 2h, taking 1mmol of dried poly adipic acid-1, 4-butanediol ester and 5mL of N, N-dimethylacetamide, adding 4mmol of isophorone diisocyanate and two drops of dibutyltin dilaurate in a four-neck flask under the protection of nitrogen, preserving heat at 60 ℃, uniformly stirring for 10min, heating to 75 ℃ for reacting for 3h to obtain an isocyanate-terminated prepolymer, and then cooling to 50 ℃.

Dissolving 3mmol of isophorone diamine in N, N-dimethylacetamide to prepare 20ml of solution, adding the solution into a syringe, slowly injecting the solution into the system within 6 hours, continuing to react at 50 ℃, and simultaneously tracking the change condition of isocyanate groups in the reaction process by adopting a Fourier infrared spectrometer. When the peak of the isocyanate group observed in the infrared spectrogram basically disappears, the reaction is finished. Then adding the reacted solution into excessive water for precipitation, washing and drying to obtain a cotton-shaped product, and putting the cotton-shaped product into a dryer for later use.

The polyurethane elastomer film is prepared by a solution casting method. Dissolving a small amount of cotton-like products in chloroform, pouring into a rectangular polytetrafluoroethylene mold, putting into a vacuum drying oven for drying at 40 ℃ for 12h after methanol is volatilized completely, and finally obtaining the polyurethane elastomer film.

Example 4

Modification of the nanoparticles: 2.5g of silane coupling agent KH550 is added into 97.5g of ethanol, and the mixture is mixed uniformly to prepare a solution with the concentration of 2.5%. Adjusting the pH value of the solution to 3-4 by using hydrochloric acid, hydrolyzing for 1 hour, adding 3-5g of silicon dioxide nano particles, uniformly mixing, and performing ultrasonic treatment for 30min to further uniformly mix. And (3) placing the four-neck flask containing the reaction liquid into a water bath at 80 ℃ for heating, carrying out coupling reaction, carrying out the reaction process for 4-8h to obtain modified nanoparticles, centrifuging the modified nanoparticles, washing and filtering the modified nanoparticles with ethanol for 3 times, and drying in an oven to obtain the purified modified nano-silica.

Preparing a nano particle/polyurethane composite elastomer: adding modified 0.085g of nano-silica into 1mmol of polycarbonate diol with the molecular weight of 2000g/mol, uniformly shearing at a high speed in a heating state, carrying out ultrasonic treatment for 15-20min, and removing water in a vacuum oven at 120 ℃ for 3 h. Then under the protection of nitrogen, adding 5mmol of isophorone diisocyanate and two drops of dibutyltin dilaurate, preserving heat at 60 ℃, uniformly stirring for 10min, heating to 75 ℃ for reaction for 3 hours, and then cooling to 50 ℃.

Dissolving 4mmol of isophorone diamine in N, N-dimethylacetamide to prepare a solution, adding the solution into a syringe, injecting the mixed solution into the system for 8 hours, continuing to react at 50 ℃, and simultaneously tracking the change condition of isocyanate groups in the reaction process by adopting a Fourier infrared spectrometer. When the peak of the isocyanate group observed in the infrared spectrogram basically disappears, the reaction is finished. And adding the solution into excessive water for precipitation, washing and drying to obtain a product, and putting the product into a dryer for later use.

Dissolving a small amount of the nano particle/polyurethane urea composite elastomer in tetrahydrofuran, pouring into a polytetrafluoroethylene mold, after the tetrahydrofuran is volatilized completely, putting into a vacuum drying oven for drying at 40 ℃ for 12 hours, and finally obtaining the nano particle/polyurethane composite elastomer film.

Referring to fig. 8, which is a graph of a tensile test curve of the nanoparticle/polyurethane composite elastomer film provided in the present embodiment, it can be seen that the tensile strength is as high as about 220MPa, and the elongation at break is as high as about 900%, which is improved by about 2.75 times and improved by about 2.25 times compared with the nanoparticle without modified silica.

Example 5

Modification of the nanoparticles: 2.5g of silane coupling agent KH560 is added into 97.5g of ethanol, and the mixture is mixed evenly to prepare a solution with the concentration of 2.5 percent. Adjusting the pH value of the solution to 3-4 with hydrochloric acid, hydrolyzing for 1 hour, adding 3-5g of alumina nanoparticles, mixing uniformly, and performing ultrasonic treatment for 30min to further mix uniformly. And (3) placing the four-neck flask containing the reaction liquid into a water bath at 80 ℃ for heating, carrying out coupling reaction, carrying out the reaction process for 4-8h to obtain modified nanoparticles, centrifuging the modified nanoparticles, washing and filtering the modified nanoparticles with ethanol for 3 times, and drying in an oven to obtain the purified modified nanoparticles.

Preparing a nano particle/polyurethane composite elastomer: adding modified 0.15g of nano alumina into 1mmol of polycarbonate diol with the molecular weight of 2000g/mol, uniformly shearing at a high speed in a heating state, carrying out ultrasonic treatment for 15-20min, and then carrying out vacuum drying in a drying oven at 120 ℃ for dewatering for 3 h. Then adding 5mmol of isophorone diisocyanate and two drops of stannous octoate under the protection of nitrogen, preserving heat at 60 ℃, stirring at constant speed for 10min, heating to 75 ℃, reacting for 3 hours, and then cooling to 50 ℃.

Dissolving weighed 4mmol of isophorone diamine in N, N-dimethylacetamide to prepare a solution, adding the solution into a syringe, injecting the mixed solution into the system for 8 hours, continuing to react at 50 ℃, and simultaneously tracking the change condition of isocyanate groups in the reaction process by adopting a Fourier infrared spectrometer. When the peak of the isocyanate group observed in the infrared spectrogram basically disappears, the reaction is finished. And adding the solution into excessive water for precipitation, washing and drying to obtain a product, and putting the product into a dryer for later use.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, it should be noted that, for those skilled in the art, many modifications and variations can be made without departing from the technical principle of the present invention, and these modifications and variations should also be regarded as the protection scope of the present invention.

Claims

1. A preparation method of a thermoplastic polyurethane elastomer is characterized by comprising the following steps:

(1) dissolving aliphatic diisocyanate and low molecular weight dihydric alcohol into an organic solvent according to the molar ratio of 2-5:1, and reacting for 2-3h at 75-85 ℃ under the action of an organic tin catalyst to obtain a prepolymer;

nano particles modified by a silane coupling agent are also mixed in the low molecular weight dihydric alcohol;

the nano particles are nano silicon dioxide;

the silane coupling agent is KH 550;

the aliphatic diisocyanate is isophorone diisocyanate;

the low molecular weight dihydric alcohol is polycarbonate dihydric alcohol; the molecular weight of the low molecular weight dihydric alcohol is 1000-5000 g/mol;

(2) slowly adding a micromolecular chain extender into the prepolymer at the temperature of 40-50 ℃, wherein the adding time is 6-12h, the molar ratio of the micromolecular chain extender to the low molecular weight dihydric alcohol is 1-4:1, and then continuously reacting at the temperature of 40-50 ℃ until the reaction is complete to obtain the thermoplastic polyurethane elastomer; the micromolecular chain extender is isophorone diamine;

the ratio of the nano particles modified by the silane coupling agent to the low molecular weight dihydric alcohol is 0.08-0.15g:1mmol in terms of mass and molar ratio.

2. The method for producing a thermoplastic polyurethane elastomer according to claim 1, characterized in that: in the step (1), the organic tin catalyst is one or more of CT-E229, stannous octoate and dibutyltin dilaurate.

3. A thermoplastic polyurethane elastomer produced by the production method described in any one of claims 1 to 2, which has a tensile breaking strength of 220MPa and an elongation at break of 900%.