A method for semi-continuous production of polyurethane prepolymer and application

Abstract

The application provides a method and application for semi-continuous production of polyurethane prepolymer, and the method comprises the following steps: 1) producing an isocyanate-terminated prepolymer at a temperature of 40-100 DEG C in the presence of a catalyst, an additive, an auxiliary substance and / or an added substance by reacting a diisocyanate with a compound having isocyanate-reactive hydrogen atoms, and the production is carried out in a reaction kettle to prepare a core prepolymer; 2) continuously producing an isocyanate-containing polyurethane prepolymer by mixing other kinds of diisocyanate or polyisocyanate with the core prepolymer in a static mixer. The method combines the traditional reaction kettle process with the continuous mixing process, can be applied to prepolymers in a wider viscosity range, and can be particularly applied to production operation switching between different raw materials. The synthesized prepolymer product has the same specifications and better performance than the batch stirring process, and the energy consumption is greatly reduced and the production efficiency is improved.

Description

Technical Field

[0001] This invention belongs to the field of isocyanate and polyurethane technology, specifically relating to a method and application for semi-continuous production of polyurethane prepolymers. Background Technology

[0002] Polyurethane, as one of the most important synthetic polymer materials in the world today, is mainly synthesized through two methods: the one-step method and the prepolymer method (also known as the two-step method). The one-step method involves simultaneously adding polyisocyanates and polyols to a reactor to react and form the polyurethane product. The prepolymer method involves first prepolymerizing isocyanates and polyols to form an isocyanate-containing polyurethane prepolymer, and then adding polyols to initiate a chain extension reaction to form the final polyurethane product.

[0003] The prepolymer method allows for more precise control over the number and type of functional groups in polyurethane, resulting in superior production quality stability and materials with better physicochemical properties, chemical stability, heat resistance, and aging resistance. Due to the wide variety of polyisocyanates and polyols used as raw materials, different formulations and conditions can produce different types of prepolymers, which can be widely used in many fields such as polyurethane foams, adhesives, coatings, elastomers, and fibers. Therefore, prepolymer technology is an important research area in polyurethane research and is extremely important for the research and development of polyurethane products.

[0004] The synthesis of prepolymers is the most important process in the prepolymer method for producing polyurethane. Polyurethane prepolymers are generally prepolymers containing terminal isocyanates, obtained by reacting isocyanates with polyols. Depending on the application, the terminal NCO content of the prepolymer typically ranges from 1% to 40%. Polyurethane prepolymers can be produced using both batch and continuous methods.

[0005] WO1994 / 29361A1 discloses a process for the batch preparation of isocyanate-terminated prepolymers, wherein the reaction is carried out in a conventional reactor at a temperature of 40-100°C and the NCO content of the prepolymer is 5-10%.

[0006] DE19823392A1 describes the production of isocyanate-terminated polyurethane prepolymers using a dynamic mixing head of a foam system. The foaming process for polyurethane molding is carried out directly in the same process.

[0007] US8835591B2 and DE102010027052A1 use continuous production, where the reaction components are mixed and transferred to storage or transport containers, and the reaction is completed during storage or transport.

[0008] WO2001 / 091897A1, WO2001 / 014441A1 and EP0722962A2 all involve the continuous production of isocyanate-terminated polyurethane prepolymers, which respectively use a plug flow perforated plate reactor, a static mixer, or directly transfer the prepolymer to the foaming process that provides polyurethane moldings after production.

[0009] Among the above preparation methods, the continuous method, in particular, can synthesize prepolymer products of the same specifications as the batch stirring process with shorter reaction times and lower energy consumption. However, the process is only suitable for low-viscosity prepolymers and only suitable for production operations without changing raw materials, which is not conducive to the production of high-viscosity prepolymers and complex formulation systems. This is because the residues of reactants and some byproducts such as excessive cross-linking due to controlled conditions gradually accumulate in the mixing elements, leading to an increase in gel particles in the product and affecting product quality. Summary of the Invention

[0010] To address the shortcomings of existing technologies, the present invention aims to provide a semi-continuous method for producing polyurethane prepolymers, which combines traditional reactor processes with continuous mixing processes. This method is applicable to a wider range of prepolymers (50-1500 cp) and is particularly suitable for production operations that switch between different raw materials. The synthesized prepolymer products have the same specifications and better performance as those produced by batch stirring processes, significantly reducing energy consumption and improving production efficiency.

[0011] Another object of the present invention is to provide the application of the polyurethane prepolymer prepared by the above method.

[0012] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0013] A semi-continuous method for producing polyurethane prepolymers includes the following steps:

[0014] 1) Preparation of the core prepolymer:

[0015] Mix any diisocyanate with any isocyanate reactive component and react in a reactor at a temperature of 40-100℃ to prepare an isocyanate-terminated core prepolymer.

[0016] 2) Preparation of polyurethane prepolymer:

[0017] At least one diisocyanate or polyisocyanate is mixed with the core prepolymer of step 1) in a static mixer to continuously produce an isocyanate-containing polyurethane prepolymer.

[0018] In some specific embodiments, the NCO content of the polyurethane prepolymer is 5-40 wt%; preferably, the NCO content is 10-40 wt%.

[0019] In some specific implementations, the viscosity of the polyurethane prepolymer is in the range of 50-1500 cp, which is suitable for the production of prepolymers with different viscosity ranges.

[0020] In some specific implementations, in step 1), the molar ratio of diisocyanate to isocyanate reactive component is greater than 1, preferably 1.2-6.0;

[0021] Preferably, the NCO content of the core prepolymer is 1-15 wt%, more preferably 5-10%.

[0022] In some specific implementation schemes, in step 1), an excess of diisocyanate and a deficiency of isocyanate reactive component react, wherein the diisocyanate and isocyanate reactive component are both single components, and the prepared core prepolymer can be stored and transported independently.

[0023] In some specific implementations, step 1) further includes the step of reacting different types of diisocyanates and isocyanate reactive components with the isocyanate reactive components separately to prepare different types of core prepolymers.

[0024] In some specific embodiments, in step 2), at least one diisocyanate or polyisocyanate is mixed with the core prepolymer in a static mixer at a mixing temperature of 20-60°C, preferably 20-45°C.

[0025] In some specific embodiments, the diisocyanate mentioned in step 1) is selected from any one of alkylene diisocyanates having 4 to 12 carbon atoms (including but not limited to 1,12-dodecane diisocyanate, 2-ethyltetramethylene diisocyanate, 1,4,2-methylpentamethylene diisocyanate, 1,5-tetramethylene diisocyanate, hexamethylene diisocyanate, 1,6-alicyclic diisocyanate, cyclohexane-1,3-diisocyanate, cyclohexane-1,4-diisocyanate, etc.) and aromatic diisocyanates (including but not limited to TDI, MDI, etc.); preferably 1,12-dodecane diisocyanate, 2-ethyltetramethylene diisocyanate, 1,4,2- The methylpentamethylene diisocyanate, 1,5-tetramethylene diisocyanate, hexamethylene diisocyanate, 1,6-alicyclic diisocyanate, cyclohexane-1,3-diisocyanate, cyclohexane-1,4-diisocyanate, TDI (2,4-TDI and its isomers, 2,6-TDI and its isomers), MDI (4,4'-MDI, 2,4'-MDI, 2,2'-MDI); more preferably, the cyclohexane-1,3-diisocyanate, cyclohexane-1,4-diisocyanate, 2,4-TDI and its isomers, 2,6-TDI and its isomers, 4,4'-MDI, 2,4'-MDI, 2,2'-MDI.

[0026] In some specific embodiments, the isocyanate reactive component in step 1) is a compound having one or more acidic hydrogen atoms, a functionality of 2 to 4, preferably 2 to 3, and a molecular weight of 300 to 8000, preferably 300 to 5000.

[0027] Preferably, the isocyanate reactive component is a polyhydroxy compound selected from any one of polyether polyols, polyester polyols, polysulfide polyols, polyesteramides, hydroxyl-containing polyacetals, and hydroxyl-containing aliphatic polycarbonate polyols.

[0028] More preferably, the polyhydroxy compound is selected from polyester polyols or polyether polyols;

[0029] More preferably, the hydroxyl value of the polyhydroxy compound is 20-800, preferably 28-300 mgKOH / g.

[0030] In this invention, the core prepolymer described in step 2) is prepared in step 1), and one or more types can be selected as needed. Correspondingly, different types of core prepolymers are prepared independently from the single-component isocyanate and single-component polyester polyol of step 1).

[0031] Specifically, for example: isocyanate A and polyester polyol A yield core prepolymer A1, isocyanate A and polyether polyol A yield core prepolymer A2, isocyanate B and polyester polyol A yield core prepolymer B1, isocyanate B and polyether polyol A yield core prepolymer B2, and various core prepolymers with different components can be prepared independently as needed.

[0032] In some specific embodiments, the diisocyanate mentioned in step 2) is selected from at least one of alkylene diisocyanates having 4 to 12 carbon atoms and aromatic diisocyanates; preferably at least one of 2,4-TDI and its isomers, 2,6-TDI and its isomers, 4,4'-MDI, 2,4'-MDI, 2,2'-MDI and carbodiimide-modified MDI;

[0033] The polyisocyanate is polyphenyl polymethylene polyisocyanate.

[0034] In this invention, organic diisocyanates and polyisocyanates can be used alone or in any mixture.

[0035] On the other hand, the polyurethane prepolymers prepared by the aforementioned method are more suitable for the preparation of polyurethane foams, adhesives, coatings, elastomers or fibers.

[0036] Except where specifically stated above, the preparation methods of the core prepolymer or polyurethane prepolymer of the present invention may refer to the prior art. For example, the addition of catalysts, additives, etc. during the preparation of the core prepolymer or polyurethane prepolymer should be within the protection scope of the present invention.

[0037] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0038] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0039] The method of this invention first prepares core prepolymers of different specifications, and then mixes the core prepolymers with isocyanates to prepare polyurethane prepolymers. The core prepolymers can be prepared from an excess of monoisocyanate and a non-excess monoisocyanate reactive component as needed. The core prepolymers prepared by the reaction are stable and convenient for storage and transportation. More importantly, based on this, different isocyanates can be added for further mixing to prepare the target polyurethane prepolymer.

[0040] The method of the present invention can be based on a small amount (one or a few kinds) of core prepolymer. By combining the core prepolymer with different kinds of isocyanates, a large number of different kinds of polyurethane prepolymers can be obtained by simple mixing, which can meet the application needs of different fields and scopes.

[0041] The method of this invention combines traditional reactor process with continuous mixing process, which can be applied to prepolymers with a wider viscosity range, and is especially suitable for production operations that switch between different raw materials. The synthesized prepolymer products have the same specifications and better performance as those produced by batch stirring process, which greatly reduces energy consumption and improves production efficiency. Detailed Implementation

[0042] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0043] The main sources of the raw materials used in the following examples are as follows:

[0044] The carbodiimide-modified isocyanate grade is WANNATECD-MDI100L;

[0045] All other raw materials are industrial products and can be obtained from various suppliers.

[0046] The main test methods involved in the following embodiments are as follows:

[0047] Viscosity: Rotational viscometer, model DV2TLV, test viscosity range: 15–6,000,000 cP; rotation speed: 0.1-200 RPM, adjustable in 200 ranges; test temperature: 25℃.

[0048] Density, tensile strength, elongation at break, and resilience: GB / T6344-2008.

[0049] Example 1

[0050] This embodiment provides a method for preparing a polyurethane prepolymer, specifically including the following steps:

[0051] 1) 4,4-dimethylene diisocyanate and polypropylene oxide polyol (hydroxyl value 35) were mixed at a mass ratio of 1:2 and reacted in a reactor at 80°C for 2.5 hours to obtain the core prepolymer A1 with an NCO content of 9.5 wt%.

[0052] 2) Mix 30 parts of 4,4-dimethylene diisocyanate, 15 parts of 2,4-dimethylene diisocyanate, 45 parts of polyphenyl polymethylene polyisocyanate, and 10 parts of the core prepolymer A1 prepared in 1) at 40°C using a static mixer to obtain a polyurethane prepolymer containing isocyanate with an NCO content of 29.3%.

[0053] Example 2

[0054] This embodiment provides a method for preparing a polyurethane prepolymer, specifically including the following steps:

[0055] 1.1) 4,4-Dimethylene diisocyanate and polypropylene oxide polyol (hydroxyl value 35) were mixed at a mass ratio of 1:2 and reacted in a reactor at 80°C for 2.5 hours to obtain the core prepolymer A2 with an NCO content of 9.5 wt%.

[0056] 1.2) 4,4-Dimethylene diisocyanate and polypropylene oxide polyol (hydroxyl value 40) were mixed at a mass ratio of 1:2 and reacted in a reactor at 80°C for 2 hours to obtain the core prepolymer B2 with an NCO content of 9.5 wt%.

[0057] 2) 25 parts of 4,4-dimethylene diisocyanate, 10 parts of 2,4-dimethylene diisocyanate, 35 parts of polyphenyl polymethylene polyisocyanate, 15 parts of core prepolymer A2 prepared in 1.1), 5 parts of core prepolymer B2 prepared in 1.2), and 10 parts of carbodiimide-modified dimethylene diisocyanate were mixed in a static mixer at 30°C to obtain a polyurethane prepolymer containing isocyanate with an NCO content of 23.5%.

[0058] Example 3

[0059] This embodiment provides a method for preparing a polyurethane prepolymer, specifically including the following steps:

[0060] 1.1) Toluene diisocyanate and polyoxypropylene polyol (hydroxyl value 56) were mixed at a mass ratio of 1:7 and reacted in a reactor at 80°C for 3.5 hours to obtain the core prepolymer A3 with an NCO content of 2.4 wt%.

[0061] 1.2) Toluene diisocyanate and polypropylene oxide ethylene oxide polyol (hydroxyl value 35) were mixed at a mass ratio of 1:10 and reacted in a reactor at 80°C for 2.5 hours to obtain core prepolymer B3 with an NCO content of 2 wt%.

[0062] 2) Mix 13 parts of toluene diisocyanate, 5 parts of dicyclohexylmethane diisocyanate, 28 parts of core prepolymer A3 prepared in 1.1), and 54 parts of core prepolymer B3 prepared in 1.2) at 20°C using a static mixer to obtain a polyurethane prepolymer containing isocyanate with an NCO content of 9.6%.

[0063] Example 4

[0064] This embodiment provides a method for preparing a polyurethane prepolymer, specifically including the following steps:

[0065] 1.1) Toluene diisocyanate and dipropylene glycol were mixed at a mass ratio of 2:1 and reacted in a reactor at 65°C for 1.5 hours to obtain the core prepolymer A4 with an NCO content of 11.3 wt%.

[0066] 1.2) 4,4-Dimethylene diisocyanate and polyoxypropylene polyol (hydroxyl value 280) were mixed at a mass ratio of 1.5:1 and reacted in a reactor at 75°C for 1.5 hours to obtain the core prepolymer B4 with an NCO content of 11.8 wt%.

[0067] 2) Mix 4 parts of toluene diisocyanate, 29.5 parts of 4,4-dimethylene diisocyanate, 2.5 parts of 2,4-dimethylene diisocyanate, 31 parts of polyphenyl polymethylene polyisocyanate, 25 parts of core prepolymer A4 prepared in 1.1), and 8 parts of core prepolymer B4 prepared in 1.2) at 40°C using a static mixer to obtain a polyurethane prepolymer containing isocyanate with an NCO content of 25.8%.

[0068] Comparative Example 1

[0069] A method for preparing a polyurethane prepolymer specifically includes the following steps:

[0070] 33 parts of 4,4-dimethylene diisocyanate, 15 parts of 2,4-dimethylene diisocyanate, 45 parts of polyphenyl polymethylene polyisocyanate, and 7 parts of polypropylene oxide ethylene oxide polyol (hydroxyl value 35) were reacted in a reactor at 80°C for 2 hours to obtain a polyurethane prepolymer containing isocyanate with an NCO content of 29.3%.

[0071] Comparative Example 2

[0072] A method for preparing a polyurethane prepolymer specifically includes the following steps:

[0073] 32 parts of 4,4-dimethylene diisocyanate, 10 parts of 2,4-dimethylene diisocyanate, 35 parts of polyphenyl polymethylene polyisocyanate, 10 parts of carbodiimide-modified dimethylene diisocyanate, 10 parts of polypropylene oxide ethylene oxide polyol (hydroxyl value 35), and 3 parts of polypropylene oxide ethylene oxide polyol (hydroxyl value 40) were reacted in a reactor at 80°C for 2 hours to obtain a polyurethane prepolymer containing isocyanate with an NCO content of 23.5%.

[0074] Comparative Example 3

[0075] A method for preparing a polyurethane prepolymer specifically includes the following steps:

[0076] 22 parts of toluene diisocyanate, 24 parts of polyoxypropylene polyol (hydroxyl value 56), 49 parts of polyoxypropylene ethylene oxide polyol (hydroxyl value 35), and 5 parts of dicyclohexylmethane diisocyanate were reacted in a reactor at 80°C for 3 hours to obtain a polyurethane prepolymer containing isocyanate with an NCO content of 9.6%.

[0077] Comparative Example 4

[0078] A method for preparing a polyurethane prepolymer specifically includes the following steps:

[0079] 21 parts of toluene diisocyanate, 33.5 parts of 4,4-dimethylene diisocyanate, 2.5 parts of 2,4-dimethylene diisocyanate, 32 parts of polyphenyl polymethylene polyisocyanate, 3 parts of polyoxypropylene polyol (hydroxyl value 280), and 8 parts of dipropylene glycol were reacted in a reactor at 70°C for 1.5 hours to obtain a polyurethane prepolymer containing isocyanate with an NCO content of 25.8%.

[0080] Application performance tests were conducted on the above embodiments and comparative examples, and the specific test results are shown in Table 1:

[0081] Table 1

[0082]

[0083] Note: Production efficiency per unit time is a comparative quantitative indicator, which compares the production volume of the same reactor size and the same production time. The quantitative indicator of production efficiency can be calculated based on the amount of material fed. Taking Example 1 as an example, the core prepolymer accounts for 10 parts, or 10%, and under the same scale effect, it can be scaled up by 100 parts / 10 parts = 10 times, or 1 / 10% = 10 times.

[0084] As shown in the table above, the method for preparing polyurethane prepolymers provided by this invention significantly increases production efficiency by several times per unit time, has a wide range of applicable product viscosity, and provides better product performance than the original process.

[0085] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for semi-continuous production of polyurethane prepolymers, characterized in that, Includes the following steps: 1) Preparation of the core prepolymer: Mix any diisocyanate with any isocyanate reactive component and react in a reactor at a temperature of 40-100°C to prepare an isocyanate-terminated core prepolymer, or... Different types of diisocyanates and isocyanate reactive components are reacted separately with isocyanate reactive components according to the single diisocyanate component to prepare different types of core prepolymers; The NCO content of the core prepolymer is 1-15 wt%; 2) Preparation of polyurethane prepolymer: At least one diisocyanate or polyisocyanate is mixed with the core prepolymer of step 1) in a static mixer to continuously produce an isocyanate-containing polyurethane prepolymer, wherein the NCO content of the polyurethane prepolymer is 5-40 wt%. This method is based on one or a few core prepolymers. By combining the core prepolymers with different types of isocyanates, a large number of different types of polyurethane prepolymers are obtained through simple mixing.

2. The method according to claim 1, characterized in that, In step 1), excess diisocyanate and insufficient isocyanate reactive component react, wherein both diisocyanate and isocyanate reactive component are single components, and the prepared core prepolymer can be stored and transported independently.

3. The method according to claim 1, characterized in that, The NCO content of the polyurethane prepolymer is 10-40 wt%.

4. The method according to claim 1, characterized in that, In step 1), the molar ratio of diisocyanate to isocyanate reactive component is greater than 1.

5. The method according to claim 4, characterized in that, In step 1), the molar ratio of diisocyanate to isocyanate reactive component is 1.2-6.

0.

6. The method according to claim 1, characterized in that, In step 1), the NCO content of the core prepolymer is 5-10 wt%.

7. The method according to any one of claims 1 to 6, characterized in that, In step 2), at least one diisocyanate or polyisocyanate is mixed with the core prepolymer in a static mixer at a mixing temperature of 20-60°C.

8. The method according to claim 7, characterized in that, The mixing temperature is 20-45℃.

9. The method according to any one of claims 1 to 6, characterized in that, The diisocyanate mentioned in step 1) is selected from any one of alkylene diisocyanates having 4 to 12 carbon atoms or aromatic diisocyanates.

10. The method according to claim 9, characterized in that, The alkylene diisocyanate having 4 to 12 carbon atoms is selected from any one of 1,12-dodecane diisocyanate, 2-ethyltetramethylene diisocyanate, and hexamethylene diisocyanate; and / or The aromatic diisocyanate is selected from either TDI or MDI.

11. The method according to any one of claims 1 to 6, characterized in that, The diisocyanate mentioned in step 1) is selected from either cyclohexane-1,3-diisocyanate or cyclohexane-1,4-diisocyanate.

12. The method according to any one of claims 1 to 6, characterized in that, The diisocyanate mentioned in step 1) is selected from any one of cyclohexane-1,3-diisocyanate, cyclohexane-1,4-diisocyanate, 2,4-TDI, 2,6-TDI, 4,4'-MDI, 2,4'-MDI, and 2,2'-MDI.

13. The method according to any one of claims 1 to 6, characterized in that, The isocyanate reactive component described in step 1) is a compound having one or more acidic hydrogen atoms, a functionality of 2 to 4, and a molecular weight of 300 to 8000.

14. The method according to claim 13, characterized in that, The isocyanate reactive component described in step 1) is a compound having one or more acidic hydrogen atoms, a functionality of 2 to 3, and a molecular weight of 300 to 5000.

15. The method according to claim 13, characterized in that, The isocyanate reactive component is a polyhydroxy compound selected from any one of polyether polyols, polyester polyols, polysulfide polyols, polyesteramides, hydroxyl-containing polyacetals, and hydroxyl-containing aliphatic polycarbonate polyols.

16. The method according to claim 15, characterized in that, The polyhydroxy compound is selected from polyester polyols or polyether polyols.

17. The method according to claim 16, characterized in that, The hydroxyl value of the polyhydroxy compound is 20-800 mg KOH / g.

18. The method according to claim 17, characterized in that, The hydroxyl value of the polyhydroxy compound is 28-300 mg KOH / g.

19. The method according to any one of claims 1 to 6, characterized in that, The diisocyanate mentioned in step 2) is selected from at least two of alkylene diisocyanates having 4 to 12 carbon atoms and aromatic diisocyanates; The polyisocyanate is polyphenyl polymethylene polyisocyanate.

20. The method according to claim 19, characterized in that, The diisocyanate mentioned in step 2) is selected from at least two of 2,4-TDI, 2,6-TDI, 4,4'-MDI, 2,4'-MDI, 2,2'-MDI and carbodiimide-modified MDI.

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