A polyurethane chain extender with high-strength polyurethane

Abstract

The application provides a polyurethane chain extender and a high-strength polyurethane, and relates to the technical field of polyurethane.The polyurethane chain extender has the following structure, wherein R1 is C1-C6 alkylene, and R2 is H or C1-C4 alkyl.The polyurethane chain extender is applied to the preparation of polyurethane materials.Because of the presence of hydrogen bond elements, a large number of hydrogen bonds can be generated in the polyurethane, so that the mechanical properties of the polyurethane material are significantly improved, and the polyurethane chain extender can also be used as a chain extender in the preparation of water-based polyurethane dispersions.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of polyurethane, and relates to a polyurethane chain extender and high-strength polyurethane. BACKGROUND

[0002] Polyurethane has good performance, and is usually obtained by reacting a polyisocyanate with a polyester polyol or a polyether polyol to obtain a prepolymer and then performing chain extension with a chain extender. Therefore, the performance of the chain extender has an important influence on the performance of the polyurethane. Commonly used chain extenders include small-molecule diols such as ethylene glycol, 1,4-butanediol and 1,6-hexanediol. The introduction of these small-molecule diols will cause microphase separation in the system, thereby affecting the mechanical properties of the polyurethane material. If the performance of the polyurethane is further optimized, a functional chain extender is becoming a research hotspot in the technical field of polyurethane. SUMMARY

[0003] At present, a large number of studies have analyzed the influence of the molecular structure of the chain extender on the mechanical properties of the polyurethane. However, as for high-performance polyurethane, the current research and processing conditions are relatively harsh. In order to solve the above technical problems, the application provides a polyurethane chain extender, so as to realize the preparation of a high-mechanical-strength polyurethane material.

[0004] The technical scheme of the application is as follows:

[0005] A polyurethane chain extender has a structure as shown in Formula I,

[0006]

[0007] wherein R1 is a C1-C6 alkylene group, and R2 is H or a C1-C4 alkyl group.

[0008] Preferably, R1 is an ethylene group, an isopropylene group or a propylene group.

[0009] Preferably, R2 is H, a methyl group or an ethyl group.

[0010] A high-strength polyurethane, wherein the polyurethane chain extender of any one of the above embodiments is used as a chain extender in the preparation process.

[0011] Preferably, the weight proportion of the polyurethane chain extender in all raw materials of the high-strength polyurethane is 0.1-20%.

[0012] More preferably, the weight proportion of the polyurethane chain extender in all raw materials of the high-strength polyurethane is 1-4%.

[0013] A high-strength polyurethane, wherein the polyurethane chain extender of any one of the above embodiments is used as one of the chain extenders in the preparation process.

[0014] Preferably, the mole ratio of the polyurethane chain extender in the chain extender is 40-90%.

[0015] Preferably, the isocyanate used to prepare the high-strength polyurethane is selected from one or a combination of toluene diisocyanate, isophorone diisocyanate, diphenyl diisocyanate, dicyclohexyl methane diisocyanate, hexamethylene diisocyanate, tetramethyl m-xylylene diisocyanate (TMXDI), xylylene diisocyanate (XDI), naphthalene diisocyanate (NDI), and lysine diisocyanate.

[0016] Preferably, the polyol used to prepare the high-strength polyurethane is selected from one or a combination of polyester diols, polyether diols, hydroxyl-terminated polybutadiene, and hydroxyl-terminated polydimethylsiloxane.

[0017] Compared with the prior art, the present application has the following beneficial effects:

[0018] (1) The polyurethane chain extender of the present application contains high-polarity groups such as diamide groups and tertiary amine groups in its structure. As a chain extender or one of the chain extenders for polyurethane, the high-polarity groups such as diamide groups and tertiary amine groups can produce hydrogen bonding, which can result in more hydrogen bonding in the polyurethane structure. The presence of a large number of hydrogen bonds improves the interaction force within the polyurethane high molecular chain and between the high molecular chains, and improves the cohesive energy, which helps to improve the strength. The dynamic crosslinking of hydrogen bonds increases energy dissipation, thereby helping to improve the toughness of the polyurethane material. The polyurethane with a high hydrogen bond content not only has high mechanical strength and toughness, but also has good mechanical recovery performance.

[0019] (2) The polyurethane chain extender of the present application contains tertiary amine groups in its structure, which can be cationized to make the polyurethane have a positive charge, thereby improving the hydrophilicity of the polyurethane. Even a polyurethane aqueous dispersion can be obtained. After drying or curing of the aqueous polyurethane dispersion, due to the hydrogen bonding between and within the high molecular chains, the polyurethane has not only higher mechanical strength, but also lower water absorption.

[0020] (3) The polyurethane chain extender of the present application has a simple preparation method and can be used as a general chain extender for polyurethane.

[0021] (4) The polyurethane chain extender of the present application contains a tertiary amine structure in its molecular structure, which can be used as a catalyst for the reaction of isocyanate with hydroxyl groups. Therefore, when the polyurethane chain extender provided by the present application is used to prepare polyurethane, a high reaction temperature (such as 180℃ or higher) is not required, and the chain extension reaction can be achieved at about 80℃. BRIEF DESCRIPTION OF DRAWINGS

[0022] The accompanying drawings, which are incorporated herein and constitute part of the specification, illustrate embodiments consistent with the application and, together with the description, further serve to explain the principles of the application, wherein:

[0023] Figure 1 is an infrared spectrum of the polyurethane chain extender N,N-bis(2-hydroxyethylmethylaminoethyl)oxamide provided by the present application;

[0024] Figure 2 is an infrared spectrum of the polyurethane prepared by Example 1 of the present application. DETAILED DESCRIPTION

[0025] The following disclosure provides many different embodiments, or examples, for implementing different structures consistent with the application. For purposes of simplicity of the present disclosure, specific examples are described in terms of specific examples. Of course, they are only examples and are not intended to limit the present application in any way. Furthermore, the present application can be implemented in different embodiments and / or examples without departing from the scope of the present application. Specifically, reference to a particular aspect of the application does not mean that the disclosure is directed towards an embodiment, the scope of which does not include other variations. The various examples of the application are illustrated by the description that follows with reference to the drawings and must not be interpreted in their restrictive sense. The elements of the various examples can be combined or replaced by other technical features, without departing from the scope of the present application. Other objects, advantages and features of the present application will become more apparent from the following detailed description when read in conjunction with the accompanying drawings.

[0026] The first aspect of the present application provides a polyurethane chain extender, the polyurethane chain extender has a structure as shown in formula I,

[0027]

[0028] wherein R1 is C1-C6 alkylene, and R2 is H or C1-C4 alkyl.

[0029] Further, in the above formula (1), R1 is ethylene, isopropylene or propylene.

[0030] Further, in the above formula (1), R2 is H, methyl or ethyl.

[0031] The structure of the polyurethane chain extender of the present application is symmetrical, the preparation method is simple, and can be obtained by substitution reaction of alkyl hydroxyalkyl substituted ethylenediamine with a chemical formula of HOR1NR2CH2CH2NH2 and oxalic acid dialkyl ester (such as diethyl oxalate). The reaction formula II is:

[0032]

[0033] wherein R3 is selected from C1-C6 hydrocarbon group.

[0034] For example, the alkyl hydroxyalkyl substituted ethylenediamine with the chemical formula of HOR1NR2CH2CH2NH2 includes N-methyl-N-hydroxyethyl ethylenediamine, N-methyl-N-(2-hydroxyethyl)-1,3-propanediamine, etc.

[0035] Specifically, taking the reaction of N-methyl-N-(2-hydroxyethyl)-1,3-propanediamine with diethyl oxalate to prepare the polyurethane chain extender of the present invention as an example, it can be prepared by the following method:

[0036] Add 0.022 mol of diethyl oxalate and 25 g of anhydrous ethanol to a reaction flask, then add 0.1 mol of N-methyl-N-(2-hydroxyethyl)-1,3-propanediamine dropwise. Stir at room temperature for 24 hours. The resulting white precipitate is the product. The white precipitate can be washed with anhydrous ethanol and dried under vacuum to directly obtain the product. Alternatively, the white precipitate can be dissolved in DMF solvent, then added dropwise to diethyl ether to precipitate a white powder. After filtration and vacuum drying, a product with higher purity can be obtained. The product name is N,N-bis(2-hydroxyethylmethylaminoethyl)oxalamide, and the chemical formula is (HOCH2CH2N(CH3)CH2CH2NHCO)2.

[0037] like Figure 1 As shown, it is located at 3284cm. -1 The peak represents the stretching vibration of the OH group in the hydroxyl group, at 2973 cm⁻¹. -1 2870cm -1 1448cm -1 1382cm -1 The peak at 1651 cm⁻¹ is the characteristic absorption peak of CH in methyl groups. -1 The characteristic absorption peak of the carbonyl group is at 1517 cm⁻¹. -1 The NH absorption peak is for amides.

[0038] The second aspect of the present invention provides a high-strength polyurethane, wherein the high-strength polyurethane is prepared by using the polyurethane chain extender described in any of the above embodiments as the sole or one of the chain extenders.

[0039] In the preparation of polyurethane, polyisocyanates are typically first added to polymeric polyols to obtain isocyanate-terminated prepolymers. These prepolymers are then chain-extended using small-molecule diols as chain extenders to obtain high-molecular-weight polyurethane. The polyurethane chain extender of this invention can directly replace existing chain extenders, such as ethylene glycol, 1,4-butanediol, and 1,6-hexanediol, or can be mixed with existing chain extenders. Therefore, there are no particular restrictions on the addition of the polyurethane chain extender of this invention during the polyurethane preparation process; it can be used in accordance with existing chain extender usage methods.

[0040] Furthermore, the aforementioned polyurethane chain extender accounts for 0.1-20% by weight of all raw materials of the high-strength polyurethane.

[0041] Furthermore, the aforementioned polyurethane chain extender accounts for 1-4% by weight of all raw materials in high-strength polyurethane.

[0042] Further, the mole ratio of the polyurethane chain extender in the chain extender is 40-90%. In the technical solution, the chain extender contains the polyurethane chain extender of the application and other existing chain extenders, such as ethylene glycol, 1,4-butanediol, 1,6-hexanediol, etc. The polyurethane chain extender of the application and the existing chain extenders (such as ethylene glycol, 1,4-butanediol, 1,6-hexanediol, etc.) are used together, which can exert the advantages of the two chain extenders.

[0043] Further, the isocyanate used in the high-strength polyurethane is not particularly limited and can be selected from one or a combination of toluene diisocyanate (TDI), isophorone diisocyanate (IPDI), diphenyl diisocyanate (MDI), dicyclohexylmethane diisocyanate (hydrogenated MDI), hexamethylene diisocyanate (HDI), tetramethyl-m-xylylene diisocyanate (TMXDI), xylylene diisocyanate (XDI), naphthalene diisocyanate (NDI), and lysine diisocyanate (LLDI).

[0044] Further, the polyol used in the high-strength polyurethane is not particularly limited and can be selected from one or a combination of polyester diols, polyether diols, hydroxyl-terminated polybutadiene, and hydroxyl-terminated polydimethylsiloxane. The polyester diols can be selected from polycaprolactone diol (PCL), polycarbonate diol (PC), polyadipate diol, and aromatic polyester diol. The polyether diols can be selected from polyethylene glycol (PEG), polypropylene glycol (PPG), and polyethylene glycol / polypropylene glycol copolymer (PEG / PPG).

[0045] The polyurethane chain extender of the application has a tertiary amine group, which is easy to be cationized with a hydrogen ion, thereby improving water solubility. Therefore, the polyurethane chain extender of the application can also be used in the preparation of water-based polyurethane. For example, in the acetone method, after a polyether diol or a polyester diol is reacted with a diisocyanate to form an isocyanate-terminated prepolymer, the polyurethane chain extender of the application is added for chain extension, acetone is added to reduce the viscosity, an ionization reagent (such as acetic acid) is added, and stirring is performed for ionization to obtain an ionized polyurethane. The ionized polyurethane is then dispersed in water, and acetone is evaporated to obtain a water-based polyurethane dispersion.

[0046] The technical solution of the application is further described and explained below according to various embodiments.

[0047] Unless otherwise specified, the raw materials in the following examples and comparative examples are all commercially available.

[0048] Tensile strength test: The test was performed according to the method of GB / T528-2009.

[0049] Tear strength test: test according to GB / T 528-2009, notch 1 mm.

[0050] Notched breaking strength: test according to GB / T 528-2009, notch 1 mm.

[0051] Water absorption: the polyurethane elastomer to be tested is weighed and recorded as W1, then immersed in deionized water at 25°C for 24 hours, taken out, the water on the surface of the elastomer is wiped off, weighed and recorded as W2, and the water absorption = (W2-W1) / W1 x 100%.

[0052] Example 1

[0053] The polyurethane chain extender N,N-bis(2-hydroxyethylmethylaminoethyl) oxamide is synthesized according to the method described above.

[0054] The dried polycaprolactone diol (PCL-2000) with an average molecular weight of 2000 and IPDI are added to the reactor at a molar ratio of 0.7:1, 0.2% of dibutyltin dilaurate based on the total weight of PCL-2000 and IPDI is added, the temperature is raised to 80°C, and the reaction is carried out for 1 h to obtain a prepolymer; then 29% of the chain extender N,N-bis(2-hydroxyethylmethylaminoethyl) oxamide based on the molar amount of IPDI (5.4% of the total raw material weight of the high-strength polyurethane) is added, and the reaction is continued at 80°C for 1 h, and then the polyurethane elastomer is obtained after cooling. Figure 2 The infrared absorption spectrum of the polyurethane elastomer is shown in

[0055] Example 2

[0056] The polyurethane chain extender N,N-bis(2-hydroxyethylmethylaminoethyl) oxamide is synthesized according to the method described above.

[0057] The dried polycaprolactone diol (PCL-2000) with an average molecular weight of 2000 and IPDI are added to the reactor at a molar ratio of 0.7:1, 0.2% of dibutyltin dilaurate based on the total weight of PCL-2000 and IPDI is added, the temperature is raised to 80°C, and the reaction is carried out for 1 h to obtain a prepolymer; then 29% of the chain extender N,N-bis(2-hydroxyethylmethylaminoethyl) oxamide based on the molar amount of IPDI (5.4% of the total raw material weight of the high-strength polyurethane) is added, and the reaction is continued at 80°C for 1 h, and then the polyurethane elastomer is obtained after cooling.

[0058] Comparative Example 1

[0059] In Example 1, the chain extender N,N-bis(2-hydroxyethylmethylaminoethyl) oxamide is replaced by an equal molar amount of 1,4-butanediol, and the remaining steps remain unchanged.

[0060] Comparative Example 2

[0061] In Example 1, the chain extender N,N-bis(2-hydroxyethylmethylaminoethyl) oxamide is replaced by equimolar N,N-bis(2-hydroxyethyl)oxamide, and the remaining steps remain unchanged.

[0062] Example 3

[0063] The polyurethane chain extender N,N-bis(2-hydroxyethylmethylaminoethyl) oxamide is synthesized according to the method described above.

[0064] The dried polypropylene glycol (PPG-1500) with an average molecular weight of 1500 and HDI are added to the reactor at a molar ratio of 0.92:1, 0.15% of dibutyl tin dilaurate based on the total weight of PPG-1500 and HDI is added, the temperature is raised to 80°C, and the reaction is carried out for 1 h to obtain a prepolymer; 7% of the chain extender N,N-bis(2-hydroxyethylmethylaminoethyl) oxamide based on the moles of HDI is added to the system (1.4% based on the total weight of high-strength polyurethane raw materials), the temperature is raised to 165°C, and the reaction is carried out for 1 h, and then the product is cooled to obtain a polyurethane elastomer.

[0065] Example 4

[0066] The polyurethane chain extender N,N-bis(2-hydroxyethylmethylaminoethyl) oxamide is synthesized according to the method described above.

[0067] The dried polypropylene glycol (PPG-1500) with an average molecular weight of 1500 and HDI are added to the reactor at a molar ratio of 0.92:1, 0.15% of dibutyl tin dilaurate based on the total weight of PPG-1500 and HDI is added, the temperature is raised to 80°C, and the reaction is carried out for 1 h to obtain a prepolymer; 7% of the chain extender N,N-bis(2-hydroxyethylmethylaminoethyl) oxamide based on the moles of HDI is added to the system (1.4% based on the total weight of high-strength polyurethane raw materials), the temperature is raised to 165°C, and the reaction is carried out for 1 h, and then the product is cooled to obtain a polyurethane elastomer.

[0068] Comparative Example 3

[0069] In Example 3, the chain extender N,N-bis(2-hydroxyethylmethylaminoethyl) oxamide is replaced by equimolar ethylene glycol, the temperature is raised to 165°C and the reaction is carried out for 1 h, which is replaced by a reaction at 80°C for 1 h, and the remaining steps remain unchanged.

[0070] The properties of Examples 1-4 and Comparative Examples 1-3 are shown in Table 1 below.

[0071] Table 1 Comparison of mechanical properties of Examples 1-4 and Comparative Examples 1-3

[0072]

[0073] From the results of Table 1, it can be seen that the polyurethane chain extender of the present application, either alone or in combination with other chain extenders, can significantly improve the mechanical strength of the polyurethane elastomer, and high-strength polyurethane can be obtained at 80°C without the need for using a higher reaction temperature.

[0074] Example 5

[0075] The polyurethane chain extender N,N-bis(2-hydroxyethylmethylaminoethyl) oxamide was synthesized according to the method described above.

[0076] After drying, polypropylene glycol (PPG-1200) with an average molecular weight of 1200 and TDI were added to the reactor at a molar ratio of 0.85:1, 0.15% of dibutyltin dilaurate based on the total weight of PPG-1500 and TDI was added, and the mixture was reacted at 82°C for 1 hour. Then, 15% of N,N-bis(2-hydroxyethylmethylaminoethyl) oxamide based on the number of moles of TDI was added (3.9% based on the total weight of the raw materials for the high-strength polyurethane), and the reaction was continued for 2 hours. Then, 1 times the weight of PEG-1200 of acetone was added to reduce the viscosity, and then acetic acid was added to adjust the pH to 4.0. The mixture was stirred for 0.5 hours, 4 times the volume of water was added, and the mixture was stirred and dispersed for 0.5 hours to obtain a polyurethane aqueous dispersion.

[0077] Example 6

[0078] In Example 5, N,N-bis(2-hydroxyethylmethylaminoethyl) oxamide was replaced with an equal molar amount of a chain extender composed of 1,4-butanediol and N,N-bis(2-hydroxyethylmethylaminoethyl) oxamide at a molar ratio of 1:2, and the remaining steps were unchanged.

[0079] Example 7

[0080] In Example 5, N,N-bis(2-hydroxyethylmethylaminoethyl) oxamide was replaced with an equal molar amount of a chain extender composed of 1,4-butanediol and N,N-bis(2-hydroxyethylmethylaminoethyl) oxamide at a molar ratio of 1:1, and the remaining steps were unchanged.

[0081] Comparative Example 4

[0082] In Example 5, N,N-bis(2-hydroxyethylmethylaminoethyl) oxamide was replaced with an equal molar amount of N-methyldiethanolamine, and the remaining steps were unchanged.

[0083] The polyurethane aqueous dispersions of Examples 5-7 and Comparative Example 4 were spread on clean tinplate to form films, and the results of the tests are shown in Table 2.

[0084] Table 2 Performance comparison of Examples 5-7 and Comparative Example 4

[0085] Tensile strength / MPa Tear strength KN / m Water absorption / % Example 5 34.8 27.6 2.2 Example 6 32.5 24.9 2.0 Example 7 31.3 23.2 1.9 Comparative Example 4 8.9 7.4 4.7

[0086] As can be seen from the results of Table 2, the polyurethane chain extender of the present application, either used alone as a chain extender for the waterborne polyurethane dispersion or in combination with other chain extenders, can significantly improve the mechanical strength of the waterborne polyurethane dispersion after film formation, and under the combined action of tertiary amine cationization and a large number of hydrogen bonds, within a certain range of addition of the polyurethane chain extender of the present application, the water absorption of the polyurethane decreases with the decrease of the polyurethane chain extender.

[0087] Other embodiments of the application will be apparent to those skilled in the art from consideration of the specification and practice of the application disclosed herein. It is intended that the present application cover any and all variations of the present application comprising modifications and / or additions of fit, together with all equivalents thereof and it is intended that the application cover the design, use and methods of the application for the full scope of the claims. It is therefore desired that the present application be considered merely exemplary of the application and that it be limited only as set forth in the claims.

[0088] It is to be understood that the application is not limited to the precise details of construction and the arrangement of components described above and illustrated in the drawings, and that various modifications and changes can be made without departing from the scope of the present application. The scope of the application is limited only by the claims that follow.

Claims

1. A high-strength polyurethane characterized by: The high-strength polyurethane adopts a polyurethane chain extender with the structure shown in the following formula I as a chain extender in the preparation process, wherein R1 is selected from C1-C6 alkylene, and R2 is selected from H or C1-C4 alkyl.

2. The high-strength polyurethane of claim 1, wherein: The R1 is ethylene, isopropylene or propylene.

3. The polyurethane chain extender of claim 1, wherein: The R2 is H, methyl or ethyl.

4. The high-strength polyurethane of claim 1, wherein: The weight proportion of the polyurethane chain extender in all raw materials of the high-strength polyurethane is 0.1-20%.

5. The high-strength polyurethane of claim 4, wherein: The weight proportion of the polyurethane chain extender in all raw materials of the high-strength polyurethane is 1-4%.

6. A high-strength polyurethane characterized by: The high-strength polyurethane adopts a polyurethane chain extender with the structure shown in the following formula I as a chain extender in the preparation process, wherein R1 is selected from C1-C6 alkylene, and R2 is selected from H or C1-C4 alkyl.

7. The high-strength polyurethane of claim 6, wherein: The R1 is ethylene, isopropylene or propylene; and the R2 is H, methyl or ethyl.

8. The high-strength polyurethane of claim 7, wherein: The molar proportion of the polyurethane chain extender in the chain extender is 40-90%.

9. The high-strength polyurethane of any of claims 1-8, wherein: The isocyanate used for preparing the high-strength polyurethane is selected from one or a combination of toluene diisocyanate, isophorone diisocyanate, diphenyl diisocyanate, dicyclohexyl methane diisocyanate, hexamethylene diisocyanate, tetramethyl m-xylylene diisocyanate, xylylene diisocyanate, naphthalene diisocyanate and lysine diisocyanate.

10. The high-strength polyurethane of any of claims 1-8, wherein: The polyol used for preparing the high-strength polyurethane is selected from one or a combination of polyester diol, polyether diol, hydroxyl-terminated polybutadiene and hydroxyl-terminated polydimethylsiloxane.

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