Method for semi-continuous production of polyurethane prepolymer and application

Abstract

The invention provides a method for semi-continuously producing a polyurethane prepolymer and application, the method comprises the following steps: 1) reacting diisocyanate with a compound with isocyanate reactive hydrogen atoms, in the presence of a catalyst, an additive, an auxiliary substance and / or an additive substance, producing an isocyanate-terminated prepolymer at the temperature of 40-100 DEG C, the production is carried out in a reaction kettle to prepare a core prepolymer; and 2) mixing other types of diisocyanate or polyisocyanate with the core prepolymer in a static mixer, and continuously producing to obtain the isocyanate-containing polyurethane prepolymer. According to the method, a traditional reaction kettle technology and a continuous mixing technology are combined, the method can be suitable for prepolymers with a wider viscosity range and particularly suitable for production operation of switching of different raw materials, the synthesized prepolymer product is the same as an intermittent stirring technology in specification and better in performance, energy consumption is greatly reduced, and production efficiency is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of isocyanate and polyurethane, and specifically relates to a method for semi-continuously producing polyurethane prepolymer and application thereof. Background Art

[0002] As one of the most important synthetic polymer materials in the world, the synthesis methods of polyurethane materials mainly include one-step method and prepolymer method (also called two-step method). The one-step method mainly involves adding polyisocyanate and polyol and other raw materials to the reactor at the same time to react and form a polyurethane product. The prepolymer method involves first prepolymerizing isocyanate and polyol and other raw materials to form a polyurethane prepolymer containing isocyanate, and then adding polyol and other raw materials to perform a chain extension reaction to form a polyurethane product.

[0003] The prepolymer method can make the number and type of polyurethane functional groups more accurately controlled, the production quality stability is better, and the prepared materials have better physical and chemical properties, chemical stability, heat resistance and aging performance. Due to the wide variety of raw materials polyisocyanates and polyols used, different types of prepolymers can be prepared under different formulas and conditions, which can be widely used in many fields such as polyurethane foams, adhesives, coatings, elastomers and fibers. Therefore, prepolymer technology is an important research content in the field of polyurethane research and is extremely important for the research and development of polyurethane products.

[0004] The synthesis of prepolymer is the most important production process in the production of polyurethane by the prepolymer method. Polyurethane prepolymer is generally a prepolymer containing terminal isocyanate obtained by the reaction of isocyanate and polyol. Depending on its application field, the terminal NCO content of the prepolymer is usually 1-40%. Polyurethane prepolymer can be produced by batch method and continuous method.

[0005] WO 1994 / 29361A1 discloses a process for batchwise preparing 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 to 10%.

[0006] DE 198 23 392 A1 describes the production of isocyanate-terminated polyurethane prepolymers using a dynamic mixing head for a foam system. The foaming to provide the polyurethane molding is carried out directly in the same process.

[0007] US8835591B2 and DE 10 2010 027 052 ​​A1 use continuous production, and after mixing the reaction components, they are transferred to storage or transportation containers, and the reaction is completed during the storage or transportation process.

[0008] WO 2001 / 091897 A1, WO 2001 / 014441 A1 and EP 0 722 962 A2 etc. all relate to the continuous production of isocyanate-terminated polyurethane prepolymers, respectively using a plug-flow perforated plate reactor, or using a static mixer, or transferring the prepolymer directly after production to a foaming process providing polyurethane moldings.

[0009] Among the above preparation methods, the continuous method in particular can achieve the synthesis of prepolymer products of the same specifications as the intermittent stirring process with a shorter reaction time and low energy consumption. However, the process is only applicable to low-viscosity prepolymers and only to production runs 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 the reactants and some by-products such as excessive cross-linking due to condition control gradually accumulate in the mixing element, which will lead to an increase in gel particles in the product and affect product quality. Summary of the invention

[0010] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a method for semi-continuously producing polyurethane prepolymers, which can combine the traditional reactor process with the continuous mixing process, can be applicable to prepolymers with a wider viscosity range (50-1500cp), and is particularly suitable for production operations switching between different raw materials. The synthesized prepolymer product has the same specifications as the intermittent stirring process and has better performance, greatly 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] In order to achieve the above-mentioned object of the invention, the present invention adopts the following technical solutions:

[0013] A method for semi-continuously producing a polyurethane prepolymer comprises the following steps:

[0014] 1) Preparation of core prepolymer:

[0015] Mixing any one of diisocyanates with any one of isocyanate-reactive components, and reacting them in a reactor at a temperature of 40-100° C. 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 a polyurethane prepolymer containing isocyanate.

[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 embodiments, the viscosity of the polyurethane prepolymer is within the range of 50-1500 cp, which is suitable for the production of prepolymers with different viscosity ranges.

[0020] In some specific embodiments, 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%, preferably 5-10%.

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

[0023] In some specific embodiments, step 1) further includes the step of reacting different types of diisocyanates and isocyanate reactive components respectively according to a single diisocyanate component and an isocyanate reactive component 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 in step 1) is selected from any one of alkylene diisocyanates having 4 to 12 carbon atoms in the alkylene group (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.), aromatic diisocyanates (including but not limited to TDI, MDI, etc.); preferably 1,12-dodecane diisocyanate, 2-ethyltetramethylene diisocyanate, 1,4,2- Any one of methyl pentamethylene diisocyanate, 1,5-tetramethylene diisocyanate, hexamethylene diisocyanate, 1,6-alicyclic diisocyanate, cyclohexane-1,3-diisocyanate, cyclohexane-1,4-diisocyanate, TDI (2,4-TDI and isomers, 2,6-TDI and isomers), MDI (4,4'-MDI, 2,4'-MDI, 2,2'-MDI); more preferably any one of cyclohexane-1,3-diisocyanate, cyclohexane-1,4-diisocyanate, 2,4-TDI and isomers, 2,6-TDI and 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 polyol selected from any one of polyether polyols, polyester polyols, polythioether polyols, polyester amides, hydroxyl-containing polyacetals, and hydroxyl-containing aliphatic polycarbonate polyols;

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

[0029] More preferably, the polyol has a hydroxyl value of 20-800, preferably 28-300 mg KOH / g.

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

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

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

[0033] The polyisocyanate is polyphenyl polymethylene polyisocyanate.

[0034] In the present invention, the organic diisocyanate and polyisocyanate may be used alone or in any mixture.

[0035] On the other hand, the polyurethane prepolymer prepared by the aforementioned method is used in the preparation of polyurethane foam, adhesive, coating, elastomer or fiber; it is more suitable for the preparation of polyurethane foam, adhesive and elastomer.

[0036] Except for the above special instructions, the preparation method of the core prepolymer or polyurethane prepolymer of the present invention can refer to the existing technology. For example, the addition of catalysts, additives, etc. during the preparation of the core prepolymer or polyurethane prepolymer should be within the scope of protection of the present invention.

[0037] The numerical range described in the present invention not only includes the point values ​​listed above, but also includes any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

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

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

[0041] The method of the present invention combines the traditional reactor process with the continuous mixing process, and can be applied to prepolymers with a wider viscosity range, and is particularly applicable to production operations switching between different raw materials. The synthesized prepolymer product has the same specifications as the intermittent stirring process and has better performance, greatly reducing energy consumption and improving production efficiency. DETAILED DESCRIPTION

[0042] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0043] The main raw materials used in the following examples are from the following sources:

[0044] Carbodiimide modified isocyanate grade WANNATE CD-MDI 100L;

[0045] The remaining 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 200 steps adjustable, test temperature: 25°C.

[0048] Density, tensile strength, elongation at break, rebound: GB / T 6344-2008.

[0049] Example 1

[0050] This embodiment provides a method for preparing polycarbonate, which specifically comprises the following steps:

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

[0052] 2) 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) were mixed at 40° C. via a static mixer to obtain an isocyanate-containing polyurethane prepolymer having an NCO content of 29.3%.

[0053] Example 2

[0054] This embodiment provides a method for preparing polycarbonate, which specifically comprises the following steps:

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

[0056] 1.2) 4,4-methylene diisocyanate and polyoxypropylene oxyethylene polyol (hydroxyl value 40) were mixed in a mass ratio of 1:2, and reacted in a reactor at 80° C. for 2 hours to obtain a 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 the core prepolymer A2 prepared in 1.1), 5 parts of the core prepolymer B2 prepared in 1.2), and 10 parts of carbodiimide-modified dimethylene diisocyanate were mixed at 30° C. in a static mixer to obtain an isocyanate-containing polyurethane prepolymer having an NCO content of 23.5%.

[0058] Example 3

[0059] This embodiment provides a method for preparing polycarbonate, which specifically comprises the following steps:

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

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

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

[0063] Example 4

[0064] This embodiment provides a method for preparing polycarbonate, which specifically comprises the following steps:

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

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

[0067] 2) 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 the core prepolymer A4 prepared in 1.1), and 8 parts of the core prepolymer B4 prepared in 1.2) were mixed at 40° C. via a static mixer to obtain an isocyanate-containing polyurethane prepolymer having an NCO content of 25.8%.

[0068] Comparative Example 1

[0069] A method for preparing polycarbonate, comprising the following steps:

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

[0071] Comparative Example 2

[0072] A method for preparing polycarbonate, comprising the following steps:

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

[0074] Comparative Example 3

[0075] A method for preparing polycarbonate, comprising the following steps:

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

[0077] Comparative Example 4

[0078] A method for preparing polycarbonate, comprising 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 are reacted in a reactor at 70°C for 1.5 hours to obtain an isocyanate-containing polyurethane prepolymer with an NCO content of 25.8%.

[0080] The application performance test was carried out on the above embodiments and comparative examples, and the specific test results are shown in Table 1:

[0081] Table 1

[0082]

[0083] Note: The production efficiency per unit time is a comparative quantitative index, and the production volume in the same reactor scale and the same production time is compared. The quantitative index of production efficiency can be calculated according to the feed amount. Taking Example 1 as an example, the core prepolymer accounts for 10 parts, that is, 10%. Under the same scale effect, it can be enlarged by 100 parts / 10 parts = 10 times, that is, 1 / 10% = 10 times.

[0084] As can be seen from the above table, the preparation method of the polyurethane prepolymer provided by the present invention greatly improves the production efficiency per unit time by more than several times, is applicable to a wide range of product viscosities, and has better product application performance than the original process.

[0085] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is 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 in the scope of protection of the present invention.

Claims

1. A method for semi-continuously producing a polyurethane prepolymer, characterized in that: The following steps are involved: 1) Preparation of core prepolymer: Mixing any one of diisocyanates with any one of isocyanate-reactive components, and reacting them in a reactor at a temperature of 40-100° C. to prepare an isocyanate-terminated core prepolymer; 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 a polyurethane prepolymer containing isocyanate.

2. The method according to claim 1, characterized in that The NCO content of the polyurethane prepolymer is 5-40 wt %; preferably, the NCO content is 10-40 wt %.

3. The method according to claim 1 or 2, characterized in that: In step 1), the molar ratio of diisocyanate to isocyanate reactive component is greater than 1, preferably 1.2-6.0; Preferably, the NCO content of the core prepolymer is 1-15 wt%, preferably 5-10%.

4. The method according to any one of claims 1 to 3, characterized in that: In step 1), an excess of diisocyanate and an insufficient amount of isocyanate-reactive component react, wherein the diisocyanate and the isocyanate-reactive component are both single components, and the prepared core prepolymer can be stored and transported independently.

5. The method according to any one of claims 1 to 4, characterized in that: Step 1) also includes the step of reacting different types of diisocyanates and isocyanate reactive components respectively according to a single diisocyanate component and an isocyanate reactive component to prepare different types of core prepolymers.

6. The method according to any one of claims 1 to 5, 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, preferably 20-45°C.

7. The method according to any one of claims 1 to 6, characterized in that: The diisocyanate in step 1) is selected from any one of an alkylene diisocyanate having 4 to 12 carbon atoms in the alkylene group and an aromatic diisocyanate; Preferably, the alkylene diisocyanate having 4 to 12 carbon atoms is selected from any one of 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, and cyclohexane-1,4-diisocyanate; and / or The aromatic diisocyanate is selected from any one of TDI and MDI; More preferably, the diisocyanate is selected from any one of cyclohexane-1,3-diisocyanate, cyclohexane-1,4-diisocyanate, 2,4-TDI and isomers, 2,6-TDI and isomers, 4,4'-MDI, 2,4'-MDI, and 2,2'-MDI.

8. The method according to any one of claims 1 to 7, characterized in that: 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; Preferably, the isocyanate-reactive component is a polyol selected from any one of polyether polyols, polyester polyols, polythioether polyols, polyester amides, hydroxyl-containing polyacetals, and hydroxyl-containing aliphatic polycarbonate polyols; More preferably, the polyol is selected from polyester polyols or polyether polyols; More preferably, the polyol has a hydroxyl value of 20-800, preferably 28-300 mg KOH / g.

9. The method according to any one of claims 1 to 8, characterized in that: In step 2), the diisocyanate is selected from at least two of alkylene diisocyanates having 4 to 12 carbon atoms in the alkylene group and aromatic diisocyanates; preferably at least two of 2,4-TDI and isomers, 2,6-TDI and isomers, 4,4'-MDI, 2,4'-MDI, 2,2'-MDI and carbodiimide-modified MDI; The polyisocyanate is polyphenyl polymethylene polyisocyanate.

10. Use of the polyurethane prepolymer prepared by the method according to any one of claims 1 to 9 in the preparation of polyurethane foam, adhesive, coating, elastomer or fiber; more suitable for the preparation of polyurethane foam, adhesive and elastomer.

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