Carbodiimide-containing polyurethane as well as preparation method and application thereof

Abstract

The invention provides carbodiimide-containing polyurethane as well as a preparation method and application thereof, and belongs to the technical field of polyurethane, the carbodiimide-containing polyurethane is prepared from the following raw materials: isocyanate, polyester polyol, a Lewis acid catalyst and a polyol chain extender; the isocyanate has a structure as shown in a formula I in the specification. According to the present invention, the isocyanate having the low polymerization degree, containing the carbodiimide group and having the end group of-NCO and having the special structure is adopted to replace the traditional polyisocyanate to be used for polyurethane synthesis, such that the hydrolysis resistance of the polyurethane material is significantly improved so as to prolong the service life of the polyurethane material, and the value of the R1 is limited so as to significantly improve the hydrolysis resistance of the polyurethane material. The polyurethane material also has good yellowing resistance, and the application range of the polyurethane material is widened.

Description

Technical Field

[0001] The present invention belongs to the technical field of polyurethanes, and relates to a polyurethane containing carbodiimide, a preparation method thereof, and an application thereof. Background Art

[0002] At present, in the field of polyurethane synthesis, traditional preparation methods mainly use polyisocyanates as raw materials. During the reaction of polyisocyanates with raw materials such as polyols to form polyurethanes, the basic structure of polyurethanes can be constructed. For example, common toluene diisocyanate (TDI) and diphenylmethane diisocyanate (MDI) form polyurethane polymers with certain molecular weights and properties through stepwise polymerization reactions with polyether polyols or polyester polyols. The reaction process is that the isocyanate group (-NCO) reacts with the hydroxyl group (-OH) of the polyol to gradually form a urethane bond (-NHCOO-), thereby constructing the main chain structure of the polyurethane.

[0003] However, polyurethanes prepared using traditional polyisocyanates have obvious defects. In practical applications, especially in humid or aqueous environments, the ester bonds of polyurethanes are prone to hydrolysis reactions. This is because the carbonyl group (C=O) in the ester bond is easily attacked by the hydroxyl group (-OH) in water molecules, resulting in the cleavage of the ester bond, and further causing the degradation of the molecular chain of the polyurethane material. This hydrolysis phenomenon seriously affects the performance of the polyurethane material. For example, it will cause a decrease in the mechanical properties of the material, such as a reduction in tensile strength and tear strength, and the material becomes soft and brittle. At the same time, hydrolysis will also cause changes in the appearance of the material, such as discoloration and foaming, greatly shortening the service life of the polyurethane material and restricting its application in some fields with high requirements for water resistance and durability, such as outdoor building materials, ship coatings, and automotive interiors.

[0004] In addition, current polyurethanes also have problems such as poor yellowing resistance.

[0005] Therefore, in this field, it is desirable to develop a polyurethane that has good hydrolysis resistance, a long service life, and excellent yellowing resistance. Summary of the Invention

[0006] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a polyurethane containing carbodiimide, a preparation method thereof, and an application thereof, so as to overcome the deficiencies of traditional polyurethane materials in terms of hydrolysis performance, service life, and yellowing resistance, and enable it to be applied in more fields with demanding requirements for water resistance and durability.

[0007] To achieve this purpose, the present invention adopts the following technical solutions:

[0008] In a first aspect, the present invention provides a polyurethane containing carbodiimide. The raw materials for preparing the polyurethane containing carbodiimide include isocyanate, polyester polyol, Lewis acid catalyst, and polyol chain extender.

[0009] The isocyanate has a structure shown in the following formula I:

[0010]

[0011] Formula I;

[0012] In formula I, n is 2 or 3, and each R1 is independently a residue obtained by removing the isocyanate group from an aliphatic diisocyanate or an alicyclic diisocyanate.

[0013] In the present invention, by using a special structure isocyanate with a low degree of polymerization containing a carbodiimide group and having -NCO at the end groups to replace the traditional polyisocyanate for the synthesis of polyurethane, the hydrolysis resistance of the polyurethane material is significantly improved, thereby extending its service life. Moreover, by defining the value of R1, the reaction activity of the isocyanate is increased, and the prepared polyurethane material also has good yellowing resistance and a high elongation rate, broadening the application range of the polyurethane material.

[0014] Compared with directly introducing a carbodiimide-containing compound during the synthesis of polyurethane, in the present invention, carbodiimide is introduced into a diisocyanate with isocyanate groups at both end groups to obtain a modified diisocyanate, and then the modified diisocyanate participates in the synthesis of polyurethane. On the one hand, this is more conducive to improving the hydrolysis resistance of the polyurethane material, and on the other hand, it helps to make the synthesis process of polyurethane simpler.

[0015] Preferably, each R1 is independently a residue obtained by removing the isocyanate group from hexamethylene diisocyanate (HDI), dicyclohexylmethane - 4,4'-diisocyanate (HMDI), isophorone diisocyanate (IPDI), or tetramethyl-m-xylylene diisocyanate (TMXDI).

[0016] Preferably, in formula I, the values of R1 are the same. That is, when n is 2 or 3, the values of multiple R1 in formula I can be the same or different, but preferably the values of multiple R1 are the same.

[0017] Preferably, the isocyanate having the structure shown in formula I is prepared by the following method:

[0018] Mix an aliphatic diisocyanate and / or an alicyclic diisocyanate with a second catalyst, and react to obtain the isocyanate having the structure shown in formula I.

[0019] Preferably, the aliphatic diisocyanate and / or alicyclic diisocyanate includes any one or a combination of at least two of hexamethylene diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, isophorone diisocyanate, and tetramethyl-m-xylylene diisocyanate.

[0020] Preferably, the second catalyst includes 3-methyl-1-phenyl-2-phospholene-1-oxide (MPPO).

[0021] Preferably, the mass ratio of the aliphatic diisocyanate and / or alicyclic diisocyanate to the second catalyst is 1000:(0.2 - 5), such as 1000:0.2, 1000:0.4, 1000:0.6, 1000:0.8, 1000:1, 1000:1.5, 1000:2, 1000:2.5, 1000:3, 1000:3.5, 1000:4, 1000:4.5, 1000:5, etc.

[0022] Preferably, the temperature of the reaction is 80 - 180 °C, such as 80 °C, 90 °C, 100 °C, 110 °C, 120 °C, 130 °C, 140 °C, 150 °C, 160 °C, 170 °C, 180 °C, etc., and the reaction time is 3 - 6 h, such as 3 h, 3.5 h, 4 h, 4.5 h, 5 h, 5.5 h, 6 h, etc.

[0023] Preferably, the reaction is carried out under the protection of an inert gas.

[0024] Preferably, the inert gas includes nitrogen.

[0025] Preferably, the polyester polyol includes polycaprolactone diol.

[0026] Preferably, the molar ratio of -NCO in the isocyanate to -OH in the polyester polyol is (0.8 - 1.2):1, such as 0.8:1, 0.9:1, 1:1, 1.1:1, 1.2:1, etc.

[0027] Preferably, the Lewis acid catalyst includes any one or a combination of at least two of stannous octoate, dibutyltin dilaurate, bismuth neodecanoate, zinc isooctoate, and tetrabutyl titanate.

[0028] Preferably, based on the total mass of the raw materials for preparing the polyurethane containing carbodiimide being 100%, the dosage of the Lewis acid catalyst is 50 - 150 ppm, such as 50 ppm, 60 ppm, 70 ppm, 80 ppm, 90 ppm, 100 ppm, 110 ppm, 120 ppm, 130 ppm, 140 ppm, 150 ppm, etc.

[0029] Preferably, the polyol chain extender includes a diol chain extender.

[0030] Preferably, the diol chain extender includes 1,4-butanediol.

[0031] Preferably, the molar ratio of the polyester polyol to the polyol chain extender is (8 - 10):1, such as 8:1, 8.5:1, 9:1, 9.5:1, 10:1, etc.

[0032] In a second aspect, the present invention provides a method for preparing a polyurethane containing carbodiimide as described in the first aspect, and the preparation method includes the following steps:

[0033] Mix the isocyanate and the polyester polyol, keep warm, then add a Lewis acid catalyst and a polyol chain extender, stir, and cure to obtain the polyurethane containing carbodiimide.

[0034] Preferably, the temperature of the mixing is 70 - 90°C, such as 70°C, 75°C, 80°C, 85°C, 90°C, etc.

[0035] Preferably, the temperature of the heat preservation is 70 - 90°C, such as 70°C, 75°C, 80°C, 85°C, 90°C, etc., and the heat preservation time is 2 - 4 h, such as 2 h, 2.5 h, 3 h, 3.5 h, 4 h, etc.

[0036] Preferably, the stirring time is 0.5 - 5 minutes, such as 0.5 minute, 1 minute, 2 minutes, 3 minutes, 4 minutes, 5 minutes, etc.

[0037] Preferably, the curing temperature is 100 - 150°C, such as 100°C, 105°C, 110°C, 115°C, 120°C, 125°C, 130°C, 135°C, 140°C, 145°C, 150°C, etc., and the curing time is 10 - 15 h, such as 10 h, 11 h, 12 h, 13 h, 14 h, 15 h, etc.

[0038] During the preparation of the polyurethane, due to the possible high viscosity of the reaction mixture (especially caused by the high viscosity of the polyol), optionally, the preparation method is carried out in the presence of a solvent. However, the presence of the solvent is less preferred because it may be necessary to remove the solvent from the produced polymer. The solvent can be any compound that does not react in the reaction system and can dissolve the starting reactants. The solvent can be selected from conventional industrial solvents, for example, esters such as propylene carbonate, ethyl acetate or butyl acetate, ketones such as acetone or butanone, aliphatic hydrocarbons such as hexane, heptane or octane, and aromatic hydrocarbons such as benzene, toluene, p-xylene, o-xylene, m-xylene and ethylbenzene, etc.

[0039] Unless otherwise specified, the reagents and raw materials used in the present invention are all commercially available.

[0040] In a third aspect, the present invention provides an application of a polyurethane containing carbodiimide as described in the first aspect in outdoor building materials, ship coatings or automotive interiors.

[0041] Compared with the prior art, the present invention has at least the following beneficial effects:

[0042] In the present invention, by using a special structure isocyanate with a low degree of polymerization containing a carbodiimide group and an -NCO end group to replace the traditional polyisocyanate for the synthesis of polyurethane, the hydrolysis resistance of the polyurethane material is significantly improved, thereby extending its service life. Moreover, by limiting the value of R1, the polyurethane material also has good yellowing resistance, broadening the application range of the polyurethane material. Specific Embodiments

[0043] The technical solutions of the present invention will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments are only for helping to understand the present invention and should not be regarded as specific limitations on the present invention. For the experimental methods without specific conditions indicated in the following embodiments, they are carried out according to conventional methods and conditions, or selected according to the product specifications.

[0044] The main raw materials and compound sources involved in the following preparation examples, comparative preparation examples, examples and comparative examples are as follows:

[0045] HDI: Hexamethylene diisocyanate, purchased from Sinopharm Chemical Reagent Co., Ltd., with a purity of ≥99.5%;

[0046] HMDI: Dicyclohexylmethane - 4,4'-diisocyanate, purchased from Sinopharm Chemical Reagent Co., Ltd., with a purity of ≥99.5%;

[0047] IPDI: Isophorone diisocyanate, purchased from Sinopharm Chemical Reagent Co., Ltd., with a purity of ≥99.5%;

[0048] TMXDI: Tetramethyl - m - xylylene diisocyanate, purchased from Sinopharm Chemical Reagent Co., Ltd., with a purity of ≥99.5%;

[0049] MDI: Diphenylmethane diisocyanate, purchased from Sinopharm Chemical Reagent Co., Ltd., with a purity of ≥99.5%;

[0050] 3 - Methyl - 1 - phenyl - 2 - phospholene - 1 - oxide (MPPO): Purchased from TCI, with a purity of ≥95.0% (RG);

[0051] Polycaprolactone diol: Purchased from Julong New Materials Co., Ltd., with a molecular weight of 2000;

[0052] Stannous octoate: Purchased from Sinopharm Chemical Reagent Co., Ltd., with a purity of ≥99.0% (RG);

[0053] 1,4 - Butanediol: Purchased from Sinopharm Reagent, with a purity of ≥99.0% (RG);

[0054] STABAXOL® I is a carbodiimide anti - hydrolysis agent, purchased from Rhein Chemie, with a purity of ≥99.0% (RG).

[0055] Preparation Example 1

[0056] In this preparation example, an isocyanate having the structure shown in Formula I is provided, and the preparation method includes the following steps:

[0057] Add 1000 g of HDI into a 5 - L three - necked flask, protect it with nitrogen, add 0.2 g of MPPO, and react at 80 °C for 4 hours to obtain the isocyanate having the structure shown in Formula I (denoted as Compound A), where n is 2.

[0058] Preparation Example 2

[0059] In this preparation example, an isocyanate having the structure shown in Formula I is provided, and the preparation method includes the following steps:

[0060] Add 1000 g of HDI into a 5 - L three - necked flask, protect it with nitrogen, add 0.2 g of MPPO, and react at 80 °C for 5.5 hours to obtain the isocyanate having the structure shown in Formula I (denoted as Compound B), where n is 3.

[0061] Preparation Example 3

[0062] Add 1000 g of HMDI into a 5 - L three - necked flask, protect it with nitrogen, add 2 g of MPPO, and react at 160 °C for 4 hours to obtain the isocyanate having the structure shown in Formula I (denoted as Compound C), where n is 2.

[0063] Preparation Example 4

[0064] Add 1000 g of IPDI into a 5 - L three - necked flask, protect it with nitrogen, add 2 g of MPPO, and react at 120 °C for 4 hours to obtain the isocyanate having the structure shown in Formula I (denoted as Compound D), where n is 2.

[0065] Preparation Example 5

[0066] Add 1000 g of TMXDI into a 5 - L three - necked flask, protect it with nitrogen, add 5 g of MPPO, and react at 170 °C for 4 hours to obtain the isocyanate having the structure shown in Formula I (denoted as Compound E), where n is 2.

[0067] Comparative Preparation Example 1

[0068] Add 1000 g of HDI into a 5-L three-necked flask, protect it with nitrogen, add 0.2 g of MPPO, and react at 80 °C for 2 hours to obtain an isocyanate with a degree of polymerization of 1 (denoted as compound DB-1).

[0069] Comparative Preparation Example 2

[0070] Add 1000 g of MDI into a 5-L three-necked flask, protect it with nitrogen, add 0.1 g of MPPO, and react at 60 °C for 4 hours to obtain an isocyanate with a degree of polymerization of 2 (denoted as compound DB-2), where R1 is an aromatic structure.

[0071] Example 1

[0072] In this example, a polyurethane containing carbodiimide is provided, and the preparation method includes the following steps:

[0073] According to the formulation in Table 1, add isocyanate into a three-necked flask, add polyester polyol while stirring at 80 °C, after heat preservation for 3 h, add a mixture of Lewis acid catalyst and polyol chain extender, stir for 1 minute, then pour the melt into a polytetrafluoroethylene mold, and cure in an oven at 110 °C for 12 h to obtain the polyurethane containing carbodiimide.

[0074] Examples 2-5, Comparative Examples 1-3

[0075] Examples 2-5 and Comparative Examples 1-3 are different from Example 1 only in that the raw materials and / or dosages used are different, as shown in Table 1 and Table 2 specifically.

[0076] Comparative Example 4

[0077] According to the formulation in Table 2, add HDI into a three-necked flask, add polyester polyol while stirring at 80 °C, after heat preservation for 3 h, add a mixture of Lewis acid catalyst, polyol chain extender, and STABAXOL® I, stir for 1 minute, then pour the melt into a polytetrafluoroethylene mold, and cure in an oven at 110 °C for 12 h to obtain the polyurethane containing carbodiimide.

[0078] Prepare the polyurethanes prepared in the above examples and comparative examples into dumbbell-shaped specimens with a thickness of 2 mm, and conduct the following tests:

[0079] (1) Tensile properties (tensile strength and elongation at break): Test according to the method of GB / T 528—1998; among them, the test method for the tensile properties after aging is: first age the sample at 85 °C and 85% humidity for 72 h, and then test according to the method of GB / T 528—1998;

[0080] (2)Yellowing resistance performance: The prepared samples were irradiated with xenon lamp at 60 °C and 50% humidity for 120 hours, and their yellowness index YI was measured. The higher the yellowness index, the easier the sample is to yellow.

[0081] (3)Hydrolysis resistance performance: The hydrolysis resistance performance was characterized by the tensile strength retention rate after 72h of aging and the elongation at break retention rate after 72h of aging. Among them, the test methods for the tensile strength after 72h of aging and the elongation at break after 72h of aging are as described in the above test (1);

[0082] Tensile strength retention rate after 72h of aging = Tensile strength after 72h of aging / Initial tensile strength × 100%;

[0083] Elongation at break retention rate after 72h of aging = Elongation at break after 72h of aging / Initial elongation at break × 100%.

[0084] The performance test results are shown in Table 1 and Table 2.

[0085] Table 1

[0086]

[0087] Table 2

[0088]

[0089] It can be seen from Table 1 that the polyurethanes containing carbodiimide provided in the embodiments of the present invention all have good hydrolysis resistance performance (tensile strength retention rate after 72h of aging: 76% - 82%, elongation at break retention rate after 72h of aging: 81% - 90%) and good yellowing resistance performance (YI: 6.5 - 8.4). This is because the embodiments of the present invention all use isocyanates with a special structure of low degree of polymerization containing carbodiimide groups and -NCO as the end group to participate in the reaction.

[0090] Compared with Example 1, the isocyanate used in Comparative Example 1 is HDI, which does not contain carbodiimide groups, and the hydrolysis resistance performance of the prepared polyurethane is greatly reduced. The degree of polymerization of the isocyanate containing carbodiimide groups used in Comparative Example 2 is too low (n is 1), and the hydrolysis resistance performance of the prepared polyurethane is reduced. The isocyanate containing carbodiimide groups used in Comparative Example 3 contains an aromatic structure, and the hydrolysis resistance performance and yellowing resistance performance of the prepared polyurethane are both reduced; On the basis of Comparative Example 1, Comparative Example 4 adds a hydrolysis inhibitor. Although the hydrolysis resistance performance of the prepared polyurethane is improved compared with Comparative Example 1, compared with the embodiments of the present invention, the hydrolysis resistance performance and yellowing resistance performance of the prepared polyurethane are both reduced.

[0091] The applicant declares that the present invention illustrates the polyurethane containing carbodiimide, its preparation method and application through the above embodiments. However, the present invention is not limited to the above embodiments, that is, it does not mean that the present invention must rely on the above embodiments to be implemented. Those skilled in the art should understand that any improvement of the present invention, the equivalent substitution of each raw material of the product of the present invention, the addition of auxiliary components, the selection of specific methods, etc. all fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A polyurethane containing carbodiimide, characterized in that, The raw materials for preparing the polyurethane containing carbodiimide include isocyanate, polyester polyol, Lewis acid catalyst, and polyol chain extender; The isocyanate has a structure shown in the following formula I: Formula I; In formula I, n is 2 or 3, and each R1 is independently the residue after removing the isocyanate group from an aliphatic diisocyanate or an alicyclic diisocyanate.

2. The polyurethane containing carbodiimide according to claim 1, characterized in that, Each R1 is independently the residue after removing the isocyanate group from hexamethylene diisocyanate, dicyclohexylmethane - 4,4'-diisocyanate, isophorone diisocyanate, or tetramethyl - m - xylylene diisocyanate; The isocyanate with the structure shown in formula I is prepared by the following method: Mix an aliphatic diisocyanate and / or an alicyclic diisocyanate with a second catalyst and react to obtain the isocyanate with the structure shown in formula I; The aliphatic diisocyanate and / or alicyclic diisocyanate includes any one or a combination of at least two of hexamethylene diisocyanate, dicyclohexylmethane - 4,4'-diisocyanate, isophorone diisocyanate, and tetramethyl - m - xylylene diisocyanate; The second catalyst includes 3 - methyl - 1 - phenyl - 2 - cyclophosphene - 1 - oxide; The mass ratio of the aliphatic diisocyanate and / or alicyclic diisocyanate to the second catalyst is 1000:(0.2 - 5); The temperature of the reaction is 80 - 180 °C, and the reaction time is 3 - 6 h; The reaction is carried out under the protection of an inert gas.

3. The polyurethane containing carbodiimide according to claim 1, characterized in that, The polyester polyol includes polycaprolactone diol.

4. The polyurethane containing carbodiimide according to claim 1, characterized in that, The molar ratio of -NCO in the isocyanate to -OH in the polyester polyol is (0.8 - 1.2):

1.

5. The polyurethane containing carbodiimide according to claim 1, characterized in that, The Lewis acid catalyst includes any one or a combination of at least two of stannous octoate, dibutyltin dilaurate, bismuth neodecanoate, zinc isooctoate, and tetrabutyl titanate.

6. The polyurethane containing carbodiimide according to claim 1, characterized in that, Based on the total mass of the raw materials for preparing the polyurethane containing carbodiimide being 100%, the dosage of the Lewis acid catalyst is 50 - 150 ppm.

7. According to the polyurethane containing carbodiimide as claimed in claim 1, characterized in that The polyol chain extender includes a diol chain extender; The diol chain extender includes 1,4 - butanediol; The molar ratio of the polyester polyol to the polyol chain extender is (8 - 10):

1.

8. A method for preparing a polyurethane containing carbodiimide according to any one of claims 1-7, characterized in that, The preparation method includes the following steps: Mix the isocyanate and the polyester polyol, keep warm, then add the Lewis acid catalyst and the polyol chain extender, stir, and cure to obtain the polyurethane containing carbodiimide.

9. The preparation method according to claim 8, characterized in that, The temperature of the mixing is 70 - 90 °C; The temperature of the heat preservation is 70 - 90 °C, and the heat preservation time is 2 - 4 h; The stirring time is 0.5 - 5 minutes; The curing temperature is 100 - 150 °C, and the curing time is 10 - 15 h.

10. Use of a polyurethane containing carbodiimide as described in any one of claims 1 - 7 in outdoor building materials, ship coatings, or automotive interiors.

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