Disclosure of Invention
The invention provides a low-dynamic-heat-generation polyurethane elastomer and a preparation method thereof, aiming at realizing the resource utilization of waste tire rubber powder, and the polyurethane elastomer with high strength and low dynamic heat generation can be prepared.
The invention is realized by the following technical scheme: a low dynamic heat generation polyurethane elastomer is prepared from the following raw materials in parts by weight,
100 parts of diisocyanate, 240-270 parts of polyester polyol, 18-24 parts of alcohol chain extender, 5-26 parts of waste tire rubber powder and 0.01-0.5 part of catalyst.
By adopting the technical scheme, the waste tire rubber powder is introduced into the polyurethane elastomer to reduce the microphase separation degree of the polyurethane, so that the prepared polyurethane elastomer has higher tensile strength and lower dynamic heat generation.
As a further improvement of the technical scheme of the invention, the diisocyanate is 4,4' -diphenylmethane diisocyanate. By adopting the technical scheme, the waste tire rubber powder reacts with the diisocyanate and is uniformly dispersed in the polyurethane matrix, so that the mechanical strength of the polyurethane elastomer material can be greatly improved, and the dynamic heat generation of the polyurethane elastomer material is reduced.
As a further improvement of the technical scheme of the invention, the polyester polyol is polycaprolactone polyol, the functionality of the polyester polyol is 2, and the relative molecular mass range is 1000-4000 g/moL. By adopting the technical scheme, the polyurethane elastomer with different aggregation state structures is prepared based on the design of the polyurethane molecular structure, so that the performance of the product presents gradient change, and the polyurethane elastomer has the characteristics of higher tensile strength and lower dynamic heat generation, and meets the use of different environmental conditions.
As a further improvement of the technical scheme of the invention, the waste tire rubber powder is prepared by crushing and grinding at normal temperature, and the particle size range of the waste tire rubber powder is 40-200 meshes.
As a further improvement of the technical scheme of the invention, the catalyst is dibutyltin dilaurate or stannous octoate. By adopting the technical scheme, the performance of the selected catalyst material is stable, the synthesis of the polyurethane prepolymer can be catalyzed, the reaction rate is accelerated, and the synthesized polyurethane prepolymer is stable.
As a further improvement of the technical scheme of the invention, the alcohol chain extender is 1, 4-butanediol. By adopting the technical scheme, the chain extender has lower activity, and is beneficial to fully mixing the prepared polyurethane prepolymer with the chain extender, so that the synthesized polyurethane elastomer product has neat appearance and stable performance.
In order to illustrate the present invention more clearly, the present invention provides a method for preparing the low dynamic heat-generating polyurethane elastomer, comprising the steps of:
the method comprises the following steps: vacuum drying the waste tire rubber powder for 10-12 h at the temperature of 80-100 ℃ for later use;
step two: vacuumizing and dehydrating polyester polyol at the temperature of 110-120 ℃ for 2-2.5h, cooling to 60-70 ℃, adding the waste tire rubber powder in corresponding parts by weight, and uniformly mixing to obtain mixed polyol;
step three: uniformly mixing diisocyanate, a catalyst and the mixed polyol in parts by weight at 60 ℃, heating to 80-90 ℃, reacting for 2.5-3 hours to obtain a prepolymer, carrying out defoaming treatment, and sealing for later use;
step four: adding the alcohol chain extender in the corresponding weight portion into the prepolymer subjected to defoaming treatment, uniformly mixing, then quickly pouring into a mold, keeping the temperature of 100 and 110 ℃ for hot-pressing reaction and molding after the gel point is reached, demolding after 40min, and curing at 100 ℃ for 24h to obtain a finished product.
The invention also aims to provide the preparation method of the low-dynamic-heat-generation polyurethane elastomer, and the polyurethane elastomer prepared by the method has the advantages of high tensile strength and low dynamic heat generation.
As a further improvement of the technical scheme of the preparation method, the mixing process of the waste tire rubber powder and the polyester polyol is carried out in a planetary vacuum stirrer; the rotating speed is 1000r/min, and the time is 600-1000 s.
As a further improvement of the technical scheme of the preparation method, the step of defoaming treatment comprises the step of placing the prepolymer in a planetary vacuum stirrer at the rotating speed of 1200r/min for 10 min.
As a further improvement of the technical scheme of the preparation method, the alcohol chain extender and the prepolymer are mixed in a planetary vacuum stirrer at the rotating speed of 1200r/min for 30-150 s.
By adopting the technical scheme, the preparation method provided by the invention is simple and easy to control in operation, relatively mild in required reaction conditions, capable of obtaining the polyurethane elastomer with higher tensile strength and lower dynamic heat generation, and suitable for large-scale industrial production and application.
In summary, compared with the prior art, the low dynamic heat generation polyurethane elastomer provided by the invention has the following beneficial effects:
(1) according to the invention, through reasonable formula design, the waste tire rubber powder is introduced to reduce the microphase separation degree of the polyurethane matrix, so that the prepared polyurethane elastomer material has higher tensile strength and lower dynamic heat generation;
(2) the waste tire rubber powder used in the invention can realize the preparation of the dynamically-heated polyurethane elastomer with low cost, and has larger market competitiveness.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be described in detail below. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. All other embodiments, which can be derived by a person skilled in the art from the examples given herein without any inventive step, are within the scope of the present invention.
Examples 1 to 4: the polyurethane elastomer with low dynamic heat generation is prepared by the following steps of:
(1) vacuumizing polycaprolactone polyol at 110 ℃ for dehydration for 2.5h, and cooling to 60-70 ℃; then uniformly mixing the rubber powder and the polyester polyol in parts by weight in a planetary vacuum mixer to obtain mixed polyol;
(2) adding the mixed polyol into a three-neck flask, adding corresponding parts by weight of diphenylmethane diisocyanate and dibutyltin dilaurate, heating to 80-85 ℃, stirring for reaction for 3 hours to synthesize a polyurethane prepolymer, defoaming in a planetary vacuum stirrer for 10min (1200r/min), and sealing for later use;
(3) and (3) adding 1, 4-butanediol in corresponding weight parts into the prepolymer obtained in the step (2), uniformly mixing (1200r/min, 100s) in a planetary vacuum stirrer, quickly pouring into a mould, keeping the temperature at 100 ℃ for hot press molding (10MPa), demoulding after 40min, and curing at 100 ℃ for 24h to obtain a finished product.
Comparative example 1: a low dynamic heat generation polyurethane elastomer is different from the polyurethane elastomers in the embodiments 1-4 in that no rubber powder is added in the step (1).
Comparative example 2: a low dynamic heat generation polyurethane elastomer, which is different from the polyurethane elastomer of example 2 in that:
firstly, synthesizing a polyurethane elastomer by adopting polycaprolactone polyol, 4' -diphenylmethane diisocyanate, dibutyltin dilaurate and 1, 4-butanediol in corresponding parts by weight in example 2 according to the steps of comparative example 1;
melting and blending the rubber powder and the polyurethane elastomer synthesized in the step (1) in an internal mixer (180 ℃, 10min), then hot-pressing into sheets (10MPa, 180 ℃, 5min), and cold-pressing (10MPa) to room temperature to obtain the finished product.
TABLE 1 formulation for the preparation of a low dynamic heat-generating polyurethane elastomer
Some of the performance data for the above comparative examples and examples are shown in table 2. In the table, the heat generation index and the storage modulus retention rate refer to the loss tangent value ratio and the storage modulus ratio of the prepared elastomer at 90 ℃ and 30 ℃, respectively, and the smaller the DHGI, the higher the SMRR and the smaller the dynamic heat generation of the polyurethane elastomer. It can be seen that the higher the rubber powder content in the in-situ synthesized polyurethane elastomer, the lower the dynamic heat generation. The reason is that the rubber powder participates in the synthesis reaction of polyurethane, and is uniformly distributed in a polyurethane matrix in a network form, so that the microphase separation of the polyurethane is reduced (as shown in figure 1), and the prepared polyurethane elastomer has a special aggregation state structure. In addition, comparative example 2 fully demonstrates that the lower dynamic heat generation of the prepared polyurethane elastomer is related to the aggregation state structure thereof and is unrelated to the low dynamic heat generation of rubber powder, and the polyurethane elastomer containing the same content of rubber powder has different aggregation state structures and naturally different dynamic heat generation performance due to different processing modes.
TABLE 2 partial Performance data for examples and comparative examples
FIG. 2 is a Cole-Cole curve of the polyurethane elastomer prepared. Obviously, the Cole-Cole curve of the polyurethane elastomer synthesized in the example is obviously different from that of the comparative example, and basically has a relaxation circular arc at a lower temperature, so that the microphase separation degree is lower, and the fact that the network-shaped uniform distribution of rubber powder in a polyurethane matrix is indirectly illustrated.
The above description is only for the specific embodiments of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present invention, and all the changes or substitutions should be covered within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the appended claims.