Foaming catalyst for producing polyurethane foam as well as preparation method and application of foaming catalyst

Abstract

The invention discloses a foaming catalyst for producing polyurethane foam as well as a preparation method and application of the foaming catalyst, and belongs to the technical field of organic chemistry. The preparation method of the foaming catalyst for producing the polyurethane foam is simple and convenient to operate, does not generate corrosive or irritant substances in the production process, does not corrode production equipment or generate environmental pollution, can generate a target product at high yield, has the advantage of low production cost, and is suitable for industrial large-scale production. The foaming catalyst for producing the polyurethane foam, prepared by the method, has the characteristics of high reaction activity, low volatility and less peculiar smell, and the harm to operators is reduced. The foaming catalyst for producing the polyurethane foam is applied to preparation of polyurethane foam plastic, the usage amount can be reduced while efficient catalysis is kept for producing the polyurethane foam, the bonding capacity of the catalyst and a polyurethane matrix is good, and the foaming catalyst has good application prospects in the polyurethane industry.

Description

Technical Field

[0001] The invention relates to the technical field of organic chemistry, and in particular to a foaming catalyst for producing polyurethane foam, and a preparation method and application thereof. Background Art

[0002] Polyurethane foams are widely known and used in automobiles, houses and other industries. They are usually produced by reacting isocyanates with polyols in the presence of various additives to produce such foams. One common type of additive is chlorofluorocarbon (CFC) blowing agents, which evaporate due to the exothermic reaction and cause the polymerized material to form foam. However, due to the discovery that CFCs are harmful to the environment by destroying ozone in the atmosphere, the use of CFCs is being reduced in the field. Therefore, the production of green and environmentally friendly water-blown foams has become more important, which uses carbon dioxide produced by the reaction of water with polyisocyanates to achieve foaming. In this reaction process, tertiary amine catalysts are a type of catalyst typically used to accelerate foaming (e.g., the reaction of water with polyisocyanates to produce carbon dioxide) and gelation (e.g., the reaction of polyols with isocyanates).

[0003] The ability of the tertiary amine catalyst to selectively promote either foaming or gelling is an important consideration in selecting a catalyst for use in producing a particular form of polyurethane foam. If the catalyst promotes the foaming reaction to too high a degree, a large amount of carbon dioxide will escape before the isocyanate and polyol have fully reacted, and the carbon dioxide will bubble out of the formulation, causing the polymeric material to collapse, thereby producing a poor quality foam. Conversely, if the catalyst promotes the gelling reaction too strongly, a substantial portion of the carbon dioxide will not escape until a significant degree of polymerization has occurred, and a poor quality foam will also be produced, characterized by high density, broken or poorly defined cells and other undesirable characteristics.

[0004] On the one hand, tertiary amine catalysts generally have a foul and offensive odor, and many tertiary amine catalysts exhibit high fluidity due to their low molecular weight. During the processing of foam plastics, the release of tertiary amines may present significant safety and toxicity issues, and the release of residual amines from consumer products is also undesirable. On the other hand, for example, a Chinese invention patent with publication number CN1099765A provides a new adduct of alkylene oxide and N-aminoethylpiperazine and a method for producing rigid polyurethane foam plastics using it, wherein the catalytic compound used includes a long-chain structure of a piperazine skeleton, and an organic polyisocyanate component and a polyol component can be reacted in the presence of a blowing agent. However, due to its low nitrogen / carbon (N / C) ratio, this type of tertiary amine catalyst is expected to require a large amount of catalyst in the production synthesis of low vapor pressure-high molecular weight amine catalysts, resulting in excessively high production costs.

[0005] In summary, designing a foaming catalyst and a preparation method that meet the requirements of safety, environmental protection, low cost and good reaction activity has positive significance for expanding the application of polyurethane foam plastics. Summary of the invention

[0006] In view of the above-mentioned defects of the prior art, in a first aspect of the present invention, a method for preparing a foaming catalyst for producing polyurethane foam with a simple process is provided, comprising the following steps: In a solution environment, piperazine reacts with a propylene oxide homologue of formula III, and the generated product is recovered to obtain catalyst compounds of formula I and formula II; any one or a mixture of two of the catalyst compounds of formula I and formula II is selected to obtain a foaming catalyst for producing polyurethane foam; Wherein, the reaction formula of the reaction is as follows: ; In the formula, R1 is selected from hydrogen and C1-C7 alkyl; R2 is selected from hydrogen and C1-C7 alkyl.

[0007] In the present invention, the solvent environment is created by an organic solvent, which plays a role in promoting the dispersion of substances and providing a suitable environment for the reaction, and is chemically inert relative to the reactants or products. Those skilled in the art can select a suitable organic solvent according to the physicochemical properties of the substrate and actual conditions. Among them, methanol is an organic solvent that is particularly suitable for the preparation of the present invention based on the purposes of low cost, wide sources, solubility, and easy separation.

[0008] Preferably, the solution environment is created by an organic solvent, and the organic solvent includes methanol.

[0009] Due to the limitation of chemical reaction kinetics, it is appropriate to add an equivalent or excess amount of substrate to the reaction, which is conducive to making the reaction proceed in the expected direction. At the same time, the amount of substrate should also be controlled within an appropriate range to avoid substrate waste and reduce production costs.

[0010] Preferably, the molar ratio of piperazine to the propylene oxide homologue of formula III is 1:1-3.

[0011] In the preparation method, piperazine and propylene oxide homologues have good reactivity and can react under ice bath to room temperature conditions without the need for high temperature, high pressure or catalyst conditions, which is conducive to industrial scale-up production.

[0012] Preferably, the reaction temperature is from 0°C to room temperature, and the reaction time is from 1 to 6 h.

[0013] After the reaction is completed, the operator can collect the product by using a common recovery method in the art based on actual conditions. Among them, rotary evaporation and vacuum concentration have good applicability and convenience, and can easily achieve the purpose of the operation.

[0014] Preferably, the recovery method includes rotary evaporation, reduced pressure vacuum concentration, and recrystallization.

[0015] The foaming catalyst is usually in liquid form and has good fluidity. In the present invention, the carbon chain length of the substituent in its structure is limited for consideration of the physical form and solubility of the product. As the alkyl chain increases, the fluidity of the product usually decreases and gradually becomes solid at room temperature. As presented in one or more embodiments of the present invention, some products have reduced fluidity or are in a solid state but still have good reactivity. In this case, adding an appropriate amount of co-solvent to dissolve it can also play the role of a foaming catalyst.

[0016] Preferably, a co-solvent is added to the foaming catalyst for producing polyurethane foam to increase fluidity.

[0017] Further preferably, the ratio of the foaming catalyst used to produce the polyurethane foam to the co-solvent is 10 wt.%-200 wt.%.

[0018] In the second aspect of the present invention, there is provided a foaming catalyst for producing polyurethane foam having high reaction activity, low volatility and little odor, which is prepared by the method of the first aspect of the present invention.

[0019] In a third aspect of the present invention, there is provided an application of a foaming catalyst for producing polyurethane foam, specifically, an application of a catalyst in catalytically generating polyurethane foam.

[0020] The foaming catalyst for producing polyurethane foam of the present invention has good catalytic effect in application, and can completely or partially replace the existing bis(dimethylaminoethyl) ether or other polyester foaming catalyst combination to catalyze polyurethane foaming. In some cases, some commercial catalysts have good fluidity and both solubilizing and catalytic effects. The commercial catalyst is used as a solubilizing agent and mixed with the foaming catalyst of the present invention to achieve a catalytic foaming effect better than that of the commercial catalyst.

[0021] Preferably, the foaming catalyst for producing polyurethane foam acts as a catalyst to catalyze the trimerization reaction of isocyanate or the reaction of isocyanate with a compound containing active hydrogen.

[0022] Based on the above technical scheme, the inventive concept of the present invention is to use piperazine and propylene oxide homologues to react under mild conditions. The process is simple to operate, no corrosive or irritating substances are generated during the production process, so it will not corrode the production equipment and cause environmental pollution, and at the same time, the product yield is high and the production cost is low.

[0023] The principle of the present invention is that the inventors designed to use piperazine as the main structure of the foaming catalyst, based on the ring tension and molecular weight of the six-membered ring, the reaction activity of the catalyst can be optimized and the subsequent generation of volatile organic compounds (VOC) can be reduced. At least one of the catalyst compounds of formula I and formula II is used as a foaming catalyst for the production of polyurethane foam. As an amine catalyst containing hydroxyl groups and C6 or higher alkyl and fatty acids, it shows good reaction activity. Although the molecular weight of such catalysts is high, it can still maintain a relatively moderate usage amount. In addition, the high molecular weight and low volatility and odor of the foaming catalyst can reduce the risk of operators and users being exposed to harmful amine vapors. When used, the amine catalyst containing hydroxyl functional groups can be chemically bonded to the polyurethane in the reaction, thereby reducing their release from the final product. The two catalyst compounds are amine catalysts with secondary hydroxyl functional groups, showing a balance between promoting the reaction of active hydrogen-isocyanate (gel and foaming) and their own reactivity with isocyanate. Therefore, the foaming catalyst system of the present invention has the ability to increase reaction activity, reduce usage and increase the ability to bind to the polyurethane matrix.

[0024] Compared with the prior art, the present invention has the following advantages and beneficial effects: The invention provides a method for preparing a foaming catalyst for producing polyurethane foam. The method is simple to operate, no corrosive or irritating substances are generated during the production process, the target product can be generated with a high yield, the production cost is low, and the method is suitable for industrial-scale production.

[0025] The invention provides a foaming catalyst for producing polyurethane foam, which has the characteristics of high reaction activity, low volatility and less odor, and reduces the harm to operators.

[0026] The invention provides an application of a foaming catalyst for producing polyurethane foam, which can reduce the usage while maintaining high-efficiency catalysis to produce polyurethane foam, and the catalyst has good bonding ability with the polyurethane matrix, and has good application prospects in the polyurethane industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1The nuclear magnetic resonance spectrum (NMR) of the product C2 of Example 1; Figure 2 This is the infrared absorption spectrum (IR) of the commercial product WANNATE 7050. DETAILED DESCRIPTION

[0028] The present invention is further described below by way of examples, but the present invention is not limited to the scope of the examples. The experimental methods in the following examples without specifying specific conditions are carried out according to conventional methods and conditions, or selected according to the product specifications.

[0029] Example 1 The preparation method of a foaming catalyst for producing polyurethane foam comprises the following steps:

[0030] Under ice bath conditions, piperazine (4 g, 1 equiv.) and methanol (100 mL) were placed in a 250 mL three-necked flask, and then propylene oxide (2 equiv.) was added dropwise; after the addition was completed, the temperature was gradually raised to room temperature for reaction, and stirring was maintained and the reaction was continued at room temperature for a predetermined time to obtain a reaction solution of N,N'-bis(2-hydroxypropyl); the reaction solutions obtained at different predetermined reaction times were concentrated by rotary evaporation under reduced pressure to obtain products C1 and C2; In this embodiment, when the predetermined reaction time is 1 h, the molar ratio of the product C1:C2 is 1:1, wherein the reaction yield of C1 is 45%, and the reaction yield of C2 is 45%; when the reaction time is 6 h, the molar ratio of the product C1:C2 is 1:3, wherein the reaction yield of C1 is 22%, and the reaction yield of C2 is 66%; At least one of C1 and C2 is selected according to demand to obtain a foaming catalyst for producing polyurethane foam.

[0031] The NMR spectrum of the representative component C2 of the foaming catalyst is as follows Figure 1 The data results are as follows: 1 H NMR (400MHz, CDCl3) δ 3.81 (dqd, J = 9.4, 6.1, 3.3 Hz, 2H), 2.77 – 2.59 (m, 4H), 2.50 –2.37 (m, 4H), 2.33 – 2.17 (m, 4H), 1.12 (dd, J = 6.1, 0.9 Hz, 6H).13 C NMR (101MHz, CDCl3) δ 77.36, 65.68 (d, J = 4.2 Hz), 62.28 (d, J = 3.9 Hz), 20.04. Example 2 The preparation method of a foaming catalyst for producing polyurethane foam comprises the following steps:

[0032] Under ice bath conditions, piperazine (4 g, 1 equiv.) and methanol (100 mL) were placed in a 250 mL three-necked flask, and then 2-ethylethylene oxide (2 equiv.) was added dropwise; after the addition was completed, the temperature was gradually raised to room temperature for reaction, and stirring was maintained and the reaction was continued at room temperature for 3 h to obtain a reaction solution of 1,1'-(piperazine-1,4-diyl)bis(butan-2-ol); the reaction solutions obtained at different reaction times were concentrated by rotary evaporation under reduced pressure to obtain crude products C3 and C4, with a total yield of 57%; at least one of C3 and C4 was selected according to demand to obtain a foaming catalyst for the production of polyurethane foam.

[0033] The high resolution mass spectrum (HRMS) results of C3 and C4 are as follows: C3:HRMS (ESI): [M+H] C8H 19 N2O Calculated for =159.1497; found =159.1493. C4:HRMS (ESI): [M+H] C 12 H 27 N2O2Calculated for =231.2073; found =231.2062. Example 3 The preparation method of a foaming catalyst for producing polyurethane foam comprises the following steps:

[0034] Under ice bath conditions, piperazine (4 g, 1 equiv.) and methanol (100 mL) were placed in a 250 mL three-necked flask, and then 2-n-octylethylene oxide (2 equiv.) was added dropwise; after the addition was completed, the temperature was gradually raised to room temperature for reaction, and stirring was maintained and the reaction was continued at room temperature for 3 h to obtain a reaction solution of 1,1'-(piperazine-1,4-diyl)bis(decane-2-ol); the reaction solutions obtained at different reaction times were concentrated by rotary evaporation under reduced pressure to obtain crude products C5 and C6, with a total yield of 54%; at least one of C5 and C6 was selected according to demand to obtain a foaming catalyst for the production of polyurethane foam.

[0035] Example 4 This example is an application example of a foaming catalyst for producing polyurethane foam. The foaming effects of the foaming catalyst for producing polyurethane foam composed of products C1 and C2 in Example 1 and the commercial LE-530 foaming catalyst under different conditions are studied.

[0036] According to the molar ratio of C1 to C2 in the foaming catalyst used to produce polyurethane foam, it is divided into the following catalysts: 1) Cat.I: C1:C2=1:0, that is, it only contains C1; it is liquid at room temperature; 2) Cat.Ⅱ: C1:C2=1:1; it is liquid at room temperature; 3) Cat.Ⅲ: C1:C2=1:3; it is solid at room temperature; 4) Cat.Ⅳ: C1:C2=0:1, that is, it only contains C2; it is solid at room temperature.

[0037] When the content of C2 gradually increases, the physical form of the foaming catalyst used to produce polyurethane foam changes from liquid to solid. Considering the properties of the foaming catalyst, the following types of commercial co-solvents are selected in this embodiment: 1: 1,4-butanediol (BDO); ​​2: LE-103; 3: LE-310; 4: LE-530; 5: Dipropylene glycol (DPG).

[0038] In addition, according to the mass fraction of catalyst to cosolvent used in the production of polyurethane foam, the dosage is divided into the following: A: 200 wt.%; B: 100 wt.%; C: 50 wt.%; D: 25 wt.%; E: 10 wt.%.

[0039] According to the combination of the above parameters, different types of foaming catalysts are obtained. Taking the number "Ⅱ-C3" as an example, "Ⅱ" means the molar ratio of Cat.Ⅱ, "3" means LE-310 as a co-solvent, and "C" means the mass fraction of the catalyst to the co-solvent used in the production of polyurethane foam is 50 wt.%; the naming rules for other numbers are the same.

[0040] The apparent reaction rate (K value) of a series of numbered blowing catalysts was tested by infrared experiments. A mixture of diphenylmethane diisocyanate (MDI) and toluenediisocyanate (TDI), namely the commercial product WANNATE 7050, was dissolved in tetrahydrofuran (THF) and then online infrared was used to measure the reaction rate (K value) at 500-2500 cm -1 The infrared absorption spectrum of WANNATE 7050 is obtained by scanning within the wave number range. Figure 2 shown.

[0041] Adjust the test state of the online infrared instrument (scan and obtain a spectrum every 1 min), add 4 mL of THF to the Schleck tube equipped with a magnet, and then start scanning. Add WANNATE 7050 to it in five times, with an interval of 1 min each time. Add commercial polyether 83EK (dissolved in 3 wt.% water) to it in five times, with an interval of 1 min each time. Finally, add a catalyst with a mass fraction of 0.5 wt.% (dissolved in 200 mg THF or 51 mg DPG) to the system, monitor for 2 h, and then monitor the wavenumber at 1645-1566 cm -1 The catalytic effects of each foaming catalyst are shown in Table 1.

[0042] Table 1: Foaming catalyst and corresponding apparent reaction rate test results

[0043] In the table, No-1 represents that the foaming catalyst contains only Cat.I.

[0044] From the K value results measured by infrared data, we can see that the K value of LE-530 is 3.54, while IV-C2 has a K value of 6.78, which is twice as fast, and III-D3 has the highest K value of 7.45, which further proves the advantages of foaming catalysts.

[0045] The conventional one-step polyurethane foaming process was adopted, and the raw materials such as polyether polyol, polyisocyanate, water, foaming catalyst, surfactant, blowing agent and other additives were added into the foaming machine in one step, and mixed under high-speed stirring for foaming. In all cases, the amount of foaming catalyst (0.5 g) was the same, and the control group was taken as the control group without adding the foaming catalyst; the variety selection of the foaming catalyst and the corresponding foaming data obtained are listed in Table 2.

[0046] Table 2: Foaming catalyst and corresponding foaming data

[0047] In the table, “-” means no measurable data.

[0048] As can be seen from the table, the commercial LE-530 foaming catalyst has a slower foaming start time / milky white time than the mixed catalyst using the foaming catalyst of the present invention; although LE-530 matures faster, its synthesis cost is much higher than the catalyst of this patent.

[0049] In summary, the preparation method of the foaming catalyst for producing polyurethane foam of the present invention is simple to operate, no corrosive or irritating substances are generated during the production process, the production equipment will not be corroded and environmental pollution will not be generated, the target product can be generated at a high yield, the production cost is low, and it is suitable for industrial-scale production. The foaming catalyst for producing polyurethane foam prepared by the method has the characteristics of high reaction activity, low volatility and less odor, and reduces the harm to operators. The foaming catalyst for producing polyurethane foam is used in the preparation of polyurethane foam plastics, and the usage can be reduced while maintaining high-efficiency catalytic production of polyurethane foam, and the catalyst has good binding ability with the polyurethane matrix, and has good application prospects in the polyurethane industry.

[0050] The preferred specific embodiments of the present invention are described in detail above. It should be understood that a person skilled in the art can make many modifications and changes based on the concept of the present invention without creative work. Therefore, any technical solution that can be obtained by a person skilled in the art through logical analysis, reasoning or limited experiments based on the concept of the present invention on the basis of the prior art should be within the scope of protection determined by the claims.

Claims

1. A method for preparing a foaming catalyst for producing polyurethane foam, characterized in that: The steps include: In a solution environment, piperazine reacts with a propylene oxide homologue of formula III, and the generated product is recovered to obtain catalyst compounds of formula I and formula II; any one or a mixture of two of the catalyst compounds of formula I and formula II is selected to obtain a foaming catalyst for producing polyurethane foam; Wherein, the reaction formula of the reaction is as follows: ； In the formula, R1 is selected from hydrogen and C1-C7 alkyl; R2 is selected from hydrogen and C1-C7 alkyl.

2. The method for preparing a foaming catalyst for producing polyurethane foam according to claim 1, characterized in that: The solution environment is created by an organic solvent, and the organic solvent includes methanol.

3. The method for preparing a foaming catalyst for producing polyurethane foam according to claim 1, characterized in that: The molar ratio of the piperazine to the propylene oxide homologue of formula III is 1:1-3.

4. The method for preparing a foaming catalyst for producing polyurethane foam according to claim 1, characterized in that: The reaction temperature is from 0°C to room temperature, and the reaction time is from 1 to 6 h.

5. The method for preparing a foaming catalyst for producing polyurethane foam according to claim 1, characterized in that: The recovery method includes rotary evaporation, reduced pressure, vacuum concentration, and recrystallization.

6. The method for preparing a foaming catalyst for producing polyurethane foam according to claim 1, characterized in that: Preferably, a co-solvent is added to the foaming catalyst for producing polyurethane foam to increase fluidity.

7. The method for preparing a foaming catalyst for producing polyurethane foam according to claim 6, characterized in that: The ratio of the foaming catalyst used to produce polyurethane foam to the co-solvent is 10 wt.%-200 wt.%.

8. A foaming catalyst for producing polyurethane foam, characterized in that: The method is prepared according to any one of claims 1 to 7.

9. A use of a foaming catalyst for producing polyurethane foam as claimed in claim 8, characterized in that: Use as a catalyst in the catalytic production of polyurethane foam.

10. The use of a foaming catalyst for producing polyurethane foam according to claim 9, characterized in that: The foaming catalyst for producing polyurethane foam serves as a catalyst for catalyzing the trimerization reaction of isocyanate or the reaction of isocyanate with a compound containing active hydrogen.

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