Preparation method of a low-temperature and rapid-curing polyurethane film material

Abstract

The present invention belongs to the technical field of the preparation of organic polymer materials, and particularly relates to a preparation method of a low-temperature and rapid-curing polyurethane film material. In the present invention, polytetramethylene ether glycol (PTMEG) is used as the diol, diphenylmethane diisocyanate (MDI) is used as the isocyanate, 1,4-butanediol (BDO) is used as the chain extender, and dibutyltin dilaurate (DBTDL) is used as the catalyst to react to prepare a rapidly curing self-healing polyurethane coating material. The rapidly curing self-healing polyurethane coating material obtained by using this preparation method can be applied in fields such as automobile manufacturing, construction engineering, aerospace, and electronic products. By introducing the reaction of PTMEG diol and MDI under the catalyst DBTDL, the polyurethane coating can be rapidly cured and formed within 2 minutes at 90 °C. By introducing the chain extender BDO, more hydrogen bonds are formed between the molecular chains, and the high-density hydrogen bond interaction endows the material with higher mechanical properties and self-healing properties.

Description

Technical Field

[0001] The present invention belongs to the technical field of the preparation of organic polymer materials, and particularly relates to a method for preparing a low-temperature and rapid-curing polyurethane film material. Background Art

[0002] Polyurethane is composed of hard segments and soft segments. The hard segments are mainly composed of isocyanates and small molecule chain extenders, and their proportion affects the heat resistance, mechanical properties, hardness, etc. of polyurethane materials. The soft segments are composed of diols or diamines, and their relative molecular weight is higher than that of isocyanates and small molecule chain extenders, and their proportion affects the elasticity, crystallization, flexibility, etc. of polyurethane. The hydrogen bonds in the hard segments and the crystallization generated by the soft segments cause a microphase separation phenomenon between the soft segments and the hard segments. There is a sea-island structure inside the polyurethane material, and this structure has functions such as reinforcement and physical crosslinking, endowing the polyurethane material with excellent properties. Polyurethane has broad development prospects in the fields of automobile manufacturing, construction, medical devices, etc. due to its good elasticity and impact resistance, excellent waterproof performance, wear and corrosion resistance, and high chemical stability.

[0003] At present, most of the polyurethane film materials prepared in China have a relatively long curing time, with an average of about several hours, far from meeting the requirements of rapid curing. The purpose of the present invention is to prepare a low-temperature and rapid-curing polyurethane film material to realize the domestic production and application of low-cost materials. Summary of the Invention

[0004] In view of this, the present invention provides a method for preparing a low-temperature and rapid-curing polyurethane film material. A PUR polyurethane material is prepared through a reaction system composed of cyanate ester, polyol, chain extender, and catalyst, which is used for rapid curing into a high-brightness and high-gloss surface and should have characteristics of a low heat release value and a fast forming speed. The in-mold coating polyurethane material developed by this method not only has advantages such as low viscosity, rapid curing, good film-forming performance, and low small molecule content, but also can be applied in the fields of construction engineering, automobile manufacturing, aerospace, and electronic products.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A method for preparing a low-temperature and rapid-curing polyurethane film material, comprising the following steps:

[0007] A1: Add 1 mol of 1,4-butanediol and dehydrated polytetrahydrofuran respectively, then add 5 g of DMF and mix and stir, and then add 2 mol of diphenylmethane diisocyanate, 0.2 g of dibutyltin dilaurate, and 15 g of DMF and heat to react to form a prepolymer;

[0008] A2: Increase the molar ratio of diphenylmethane diisocyanate, polytetrahydrofuran, and 1,4-butanediol to 2 - 3:1:1 to increase the R value (-NCO / -OH) to 1.3. Since the -NCO groups in the isocyanate react with moisture in the air to form urea groups, a part of the -NCO groups is lost. Then add the remaining diphenylmethane diisocyanate in three portions with stirring, adding 4 g of DMF each time. After the reaction is complete, bubble the mixture under vacuum, pour the treated mixture onto a glass plate to coat a film, and heat and cure to obtain the low-temperature and rapid-curing polyurethane film material.

[0009] Preferably, in step A1, the dehydration temperature of polytetrahydrofuran is 110 °C, and the dehydration time is 2 h; the rotation speed of the stirrer is 200 - 300 r / min, preferably 300 r / min;

[0010] The heating reaction temperature is 70 - 80 °C, preferably 70 °C; the heating reaction time is 2 h.

[0011] Preferably, in step A2, the molar ratio of the diphenylmethane diisocyanate, polytetrahydrofuran, and 1,4-butanediol is preferably 2.6:1:1.

[0012] Preferably, the operation of adding the remaining diphenylmethane diisocyanate in three portions is as follows:

[0013] Stir for 30 min for the first time, 1 h for the second time, and 30 min for the third time.

[0014] Preferably, in step A2, the curing temperature is 80 - 90 °C, preferably 90 °C; the coating film thickness is 500 μm.

[0015] Compared with the prior art, the beneficial effects of the present invention are:

[0016] The present invention uses polytetrahydrofuran (PTMEG) as the diol, diphenylmethane diisocyanate (MDI) as the isocyanate, 1,4-butanediol (BDO) as the chain extender, and dibutyltin dilaurate as the catalyst to react and prepare a low-temperature and rapid-curing polyurethane film material. The composed material system is simple, efficient, and low in cost, which is conducive to realizing industrial production. The low-temperature and rapid-curing polyurethane film material obtained by this preparation method can be applied in fields such as automobile manufacturing, construction engineering, aerospace, and electronic products.

[0017] The present invention makes the polyurethane coating rapidly cure and form within 2 min at 90 °C by introducing PTMEG diol to react with MDI under the catalyst DBTDL, and introducing the chain extender BDO to form more hydrogen bonds between its molecular chains. The high-density hydrogen bond interaction endows the material with higher mechanical properties and self-healing properties. Description of the Drawings

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on the provided drawings.

[0019] Figure 1 Schematic diagram for preparing a fast-curing polyurethane film of the present invention.

[0020] Figure 2 Schematic diagram of the infrared spectrum of a 1000 molecular weight PTMEG-based MDI-type polyurethane film.

[0021] Figure 3 Schematic diagram of the infrared spectrum of a 2000 molecular weight PTMEG-based MDI-type polyurethane film.

[0022] Figure 4 Schematic diagram of the infrared spectrum of a p-phenylene diisocyanate (PPDI)-type polyurethane film.

[0023] Figure 5 Schematic diagram of the infrared spectrum of an isophorone diisocyanate (IPDI)-type polyurethane film. Detailed implementation manners

[0024] The following will clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of them. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0025] The special term "embodiment" here, any embodiment described as "exemplary" does not have to be construed as superior to or better than other embodiments. For the performance index tests in the embodiments of this application, unless otherwise specified, the conventional test methods in the art are adopted. It should be understood that the terms described in this application are only for describing special implementation manners and are not used to limit the content disclosed in this application.

[0026] Unless otherwise specified, the technical and scientific terms used herein have the same meanings as those generally understood by those of ordinary skill in the technical field to which this application belongs; other test methods and technical means not specifically noted in this application refer to the experimental methods and technical means commonly adopted by those of ordinary skill in the art.

[0027] To better illustrate the content of this application, numerous specific details are provided in the following specific embodiments. Those skilled in the art should understand that this application can still be implemented without certain specific details. In the embodiments, some methods, means, instruments, equipment, etc. that are well-known to those skilled in the art are not described in detail to highlight the gist of this application.

[0028] On the premise of no conflict, the technical features disclosed in the embodiments of this application can be combined arbitrarily, and the obtained technical solutions belong to the content disclosed in the embodiments of this application.

[0029] The present invention discloses a preparation method of a low-temperature and fast-curing polyurethane film material.

[0030] To better understand the present invention, the following embodiments are used to further specifically elaborate on the present invention, but it should not be construed as a limitation to the present invention. For some non-essential improvements and adjustments made by those skilled in the art based on the above-mentioned invention content, they are also considered to fall within the protection scope of the present invention. Embodiment

[0031] In this embodiment, polytetrahydrofuran is used as the diol, diphenylmethane diisocyanate is used as the isocyanate, dibutyltin dilaurate is used as the catalyst, and 1,4-butanediol is used as the chain extender. After the pre-polymerization of the diol and the isocyanate is successful, an appropriate amount of isocyanate is added to increase the molar ratio to 2.6:1:1, and finally, film coating and low-temperature curing are carried out to prepare a fast-curing polyurethane film material. The preparation flow chart is as Figure 1 shown, and the specific method is as follows:

[0032] (1) Add 1 mol each of polytetrahydrofuran and 1,4-butanediol and 5 g of DMF to a flask and mix and stir for 30 min.

[0033] (2) Add 2 mol of MDI, 0.2 g of DBTDL, and 15 g of DMF to the flask, and heat and stir at 70 °C and 300 r / min for 2 h to form a prepolymer.

[0034] (3) After the pre-polymerization is completed, raise the molar ratio of diphenylmethane diisocyanate, polytetrahydrofuran, and 1,4-butanediol to 2.6:1:1, and add the remaining 0.6 mol of MDI to the prepolymer in three portions. Add 0.39 g for the first time and stir for 30 min, add 0.48 g for the second time and stir for 1 h, add 0.31 g for the third time and stir for 30 min, and add 4 g of DMF each time to reduce its viscosity.

[0035] (4) After all the reactions are completed, bubble the synthesized polyurethane glue in a vacuum oven at 60 °C for 30 min.

[0036] (5) Spray a layer of mold release agent on the glass plate, place it in an oven and heat for 5 min. Finally, use a 500-μm coating rod to evenly coat the polyurethane glue on the glass plate. Place the glass plate in an oven at 90 °C and heat it to cure into a film, and record the curing time.

[0037] (6) After the heating is completed, detach the polyurethane film from the glass plate to obtain a rapidly cured polyurethane film. Example

[0038] In this example, polytetrahydrofuran is used as the diol, diphenylmethane diisocyanate is used as the isocyanate, dibutyltin dilaurate is used as the catalyst, and 1,4-butanediol is used as the chain extender. After the pre-polymerization of the diol and the isocyanate is successful, an appropriate amount of isocyanate is added to increase the molar ratio to 3:1:1. Finally, coating and low-temperature curing are carried out to prepare the polyurethane film material. The specific method is as follows:

[0039] (1) Add 1 mol each of polytetrahydrofuran and 1,4-butanediol and 5 g of DMF to a flask and mix and stir for 30 min.

[0040] (2) Add 2 mol of MDI, 0.2 g of DBTDL, and 15 g of DMF to the flask, and heat and stir at 70 °C and 300 r / min for 2 h to form a prepolymer.

[0041] (3) After the pre-polymerization is completed, increase the molar ratio of diphenylmethane diisocyanate, polytetrahydrofuran, and 1,4-butanediol to 3:1:1. Add the remaining 1 mol of MDI to the prepolymer in three portions. Add 0.40 g for the first time and stir for 30 min, add 0.72 g for the second time and stir for 1 h, and add 0.31 g for the third time and stir for 30 min. Add 4 g of DMF each time.

[0042] (4) After all the reactions are completed, bubble the synthesized polyurethane glue in a vacuum oven at 60 °C for 30 min.

[0043] (5) Spray a layer of mold release agent on the glass plate, place it in an oven and heat for 5 min. Finally, use a 500-μm coating rod to evenly coat the polyurethane glue on the glass plate. Place the glass plate in an oven at 90 °C and heat it to cure into a film, and record the curing time.

[0044] (6) After the heating is completed, detach the polyurethane film from the glass plate to obtain a rapidly cured polyurethane film.

[0045] To further prove the beneficial effects of the present invention for better understanding of the present invention, the technical features disclosed by the present invention are further clarified by the following test examples, but it should not be construed as a limitation to the present invention. For other improvements made by those skilled in the art without creative work based on the above-mentioned invention content, they are also considered to fall within the protection scope of the present invention.

[0046] Test Example:

[0047] (1) The infrared spectrum schematic diagram of the 1000 molecular weight PTMEG-based MDI type polyurethane film in this example is as Figure 2 shown. As can be seen from Figure 2 (a) and (b) therein, the characteristic peaks of PTMEG include C-H at 2934 cm -1 and 2850 cm -1 , the bending vibration absorption peaks of -CH2- are at 1447 cm -1 and 1367 cm -1 , the in-plane bending vibration absorption peak of -OH is at 1235 cm -1 , and the stretching vibration absorption peak of the ether bond is at 1100 cm -1 (Figure a). The characteristic peak of MDI is mainly the asymmetric stretching vibration absorption peak of -NCO at 2255 cm -1 . In the infrared spectrum of PU, a C=O stretching vibration absorption peak is located at 1591 cm -1 - 1741 cm -1 and an ether bond stretching vibration absorption peak is at 1104 cm -1 , and the asymmetric stretching vibration absorption peak of -NCO disappears at 2253 cm -1 . As the reaction proceeds, the FTIR absorption intensity of -NCO gradually decreases (Figure b), indicating that the reaction between MDI and PTMEG is successful, the isocyanate group reacts with the hydroxyl group to form urethane, and the expected product is formed.

[0048] The curing time of the polyurethane film cured at 90 °C is 7 min. The film is overall transparent, has good elasticity and high adhesion.

[0049] (2) The infrared spectrum schematic diagram of the 2000 molecular weight PTMEG-based MDI type polyurethane film in this example is as Figure 3 shown. As can be seen from Figure 3 therein, the -NCO characteristic peak in the infrared spectrum of the PU film has disappeared at 2253 cm -1 , indicating that MDI has completely reacted, and -NCO reacts with -OH to form urethane, generating the expected polyurethane product.

[0050] The curing time of the polyurethane film cured at 90 °C is 2 min. The synthesized polyurethane adhesive is yellowish, the film as a whole is transparent, with high adhesion and high elasticity.

[0051] (3)The infrared spectrum schematic diagram of the polyurethane film of p-phenylene diisocyanate (PPDI) type in this example is as Figure 4 shown. It can be seen from the Figure 4 infrared spectrum of the PU film that the characteristic peaks of -NCO at 2220 cm -1 ~2280 cm -1 disappear in the PU sample, indicating that all -NCO groups have reacted with -OH groups, and the PPDI type polyurethane film has been successfully synthesized. The curing time of the polyurethane film cured at 90 °C is 3 min, and the film as a whole is matte.

[0052] (4)The infrared spectrum schematic diagram of the polyurethane film of isophorone diisocyanate (IPDI) type in this example is as Figure 5 shown. It can be seen from Figure 5 that there are no characteristic peaks near the wavenumber of 2270 cm -1 in the polyurethane film synthesized from PTMEG, IPDI and BDO, that is, the -NCO groups have completely reacted and there are no free -NCO groups in the system, indicating that the IPDI type polyurethane film has been successfully prepared. The curing time of the polyurethane film cured at 90 °C is 7 min, the film as a whole is transparent, with poor mechanical properties and high adhesion.

[0053] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A preparation method of a low-temperature and rapid-curing polyurethane film material, characterized in that, It includes the following steps: A1: Add 1 mol of 1,4-butanediol and dehydrated polytetrahydrofuran respectively, then add 5 g of DMF and mix and stir. Subsequently, add 2 mol of diphenylmethane diisocyanate, 0.2 g of dibutyltin dilaurate and 15 g of DMF and heat to react to form a prepolymer; A2: Increase the molar ratio of diphenylmethane diisocyanate, polytetrahydrofuran and 1,4-butanediol to 2-3:1:

1. Add the remaining diphenylmethane diisocyanate in three portions, stir, and add 4 g of DMF each time. After the reaction is complete, evacuate the bubbles from the mixture under vacuum, pour the treated mixture on a glass plate to coat a film, and heat and cure to obtain the low-temperature and rapid-curing polyurethane film material; The operation of adding the remaining diphenylmethane diisocyanate in three portions is as follows: Stir for 30 min for the first time, stir for 1 h for the second time, and stir for 30 min for the third time; In step A1, the dehydration temperature of polytetrahydrofuran is 110 °C, and the dehydration time is 2 h; the rotation speed of the stirrer is 200-300 r / min; The heating reaction temperature is 70-80 °C, and the heating reaction time is 2 h; In step A2, the curing temperature is 80-90 °C, and the film coating thickness is 500 μm.

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