CN115636974B - Carbon dioxide adduct foaming agent of calcium carbonate-coated polyethyleneimine - Google Patents
Carbon dioxide adduct foaming agent of calcium carbonate-coated polyethyleneimine Download PDFInfo
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Abstract
The invention discloses a carbon dioxide adduct foaming agent of polyethyleneimine and/or grafted modified polyethyleneimine coated by calcium carbonate, which is characterized in that the particle size of the calcium carbonate is 50 nm-10 mu m, and the carbon dioxide adduct foaming agent contains 5-50% of polyethyleneimine or grafted modified polyethyleneimine by mass; the molecular weight of the polyethyleneimine is not less than 200; the graft modified polyethyleneimine contains not less than 50% by mass of polyethyleneimine segments. The foaming agent plays a role of the foaming agent in the polyurethane foaming process; the calcium carbonate particles can prevent amine groups of the polyethyleneimine from participating in the reaction of polyurethane; the grafted side chains of the grafted and modified PEI help to stabilize the calcium carbonate particles, so that the calcium carbonate particles are uniformly dispersed in the polyurethane raw material, and the reinforcing effect of the calcium carbonate particles is exerted.
Description
Technical Field
The invention relates to a carbon dioxide adduct foaming agent of polyethyleneimine coated with calcium carbonate and application thereof, belongs to the technical field of foaming agents, and particularly relates to preparation and application of a carbon dioxide adduct foaming agent of polyethyleneimine coated with nano-scale calcium carbonate.
Background
The polyurethane foam has large usage amount and is widely used in the fields of sofas, mattresses, automobile cushions, refrigerators, pipelines, building heat preservation and the like. The production of polyurethane foams requires large amounts of blowing agents, which have been experienced by four generations to date. The first generation of blowing agents were low boiling chlorofluorocarbon (CFC) compounds, which significantly destroyed the ozone layer and had severe greenhouse effect, and were currently prohibited. The second generation blowing agent is a Hydrochlorofluorocarbon (HCFC) compound. Although the Ozone Depletion Potential (ODP) of the compound is greatly reduced, the compound still has very high greenhouse effect, namely the Global Warming Potential (GWP) is larger, and the compound is subject to elimination. The third generation foaming agent is a Hydrofluorocarbon (HFC) compound, is a so-called environment-friendly foaming agent because of no chlorine and no ozone layer damage, and is popularized and applied in China at present; GWP is still high, however, its use is limited by the "kyoto protocol", and developed countries have begun to ban. The fourth generation foaming agent is fluorine-containing olefin (HFO) compound, and the decomposition product of the foaming agent in the atmosphere contains trifluoroacetic acid (CF) 3 COOH) and hydrofluoric acid (HF) can cause acid pollution and destroy the ecological environment. Alkane blowing agents (e.g., cyclopentane) perform similarly to HCFOs, and have little environmental impact, but are subject to the risk of flammability and explosiveness. In addition, all the foaming agents are volatile organic mattersVOC), and the total amount of VOC is increasingly controlled for closed and semi-closed spaces such as automobiles, airplanes, and the like.
In order to address the environmental problems with existing blowing agents, the prior art has developed carbon dioxide adduct blowing agents of hydrophobically modified polyethyleneimines as described in CN 103965470A and CN 107880306 a. The foaming agent is white powdery particles, carbon dioxide adducts are arranged in the particles, hydrophobic chains are arranged outside the particles, and the foaming agent can be dispersed into polyether polyol. In the course of forming the foam, the foaming agent absorbs the heat of reaction of the polyurethane and then emits CO 2 Is involved in polyurethane foaming. The foaming agent releases CO in the range of 50-150 DEG C 2 . The disadvantage is that it is solid and insoluble in polyether polyol at normal temperature. When the combined polyether contains small molecules (with dilution effect) such as flame retardant, a better dispersing effect can be achieved through hydrophobic modification. However, when the polyether composition does not contain a flame retardant, the dispersion of such a foaming agent is quite difficult.
Calcium carbonate is widely used for applications such as sealants, rubbers, and plastics, and particularly for fine nano calcium carbonate, it has been used as an inorganic powder filler for the purpose of improving physical properties in these applications. Calcium carbonate is often used as a nucleating agent in foam materials to improve the mechanical strength of the foam materials. From the viewpoint of reinforcing the polymer, it is theorized that the smaller the particle diameter of calcium carbonate becomes, the more the reinforcing effect can be improved. However, in practice, when the particle size of calcium carbonate becomes small, the particles aggregate with each other to form aggregates, and it becomes difficult to disperse in the polymer. Therefore, it is found that when the particle diameter is too small, a high reinforcing effect cannot be obtained.
Disclosure of Invention
The inventors have noted that Polyethyleneimine (PEI) contains a very high amine group density and can be combined with CO 2 Reaction to form adducts to convert CO 2 Immobilization onto the PEI molecular chain; the adducts are unstable and can release CO again under heating 2 . The inventors hypothesize that this kind of CO 2 The adducts can also release CO under appropriate conditions 2 Participate in chemical reactions; for this purpose the inventors have adopted PEI CO 2 Adducts as CO 2 The source tried to synthesize calcium carbonate. CO of PEI 2 Adducts convert CO 2 The starting material is immobilized in the molecular chain of the PEI, and thus both nucleation and initial crystal growth of the calcium carbonate are confined in the polymer chain, allowing the polymer chain to penetrate between the calcium carbonate grains and intimate contact between the calcium carbonate grains. CO of PEI 2 The adducts act as independent "microreactors" in which the nucleation and initial growth of calcium carbonate is limited; and PEI and calcium carbonate particles are tightly combined to regulate and stabilize the crystal form. The calcium carbonate particles encapsulate PEI between the grains, and the encapsulated PEI can still absorb CO 2 An adduct is formed which acts as a blowing agent. If the PEI is subjected to hydrophobic modification, hydrophobic groups of the PEI are distributed on the surfaces of the calcium carbonate particles, so that the PEI plays a role in dispersing the calcium carbonate particles in the raw materials of polyurethane.
It should be noted that: the term "encapsulate" as used herein does not mean that the calcium carbonate completely encapsulates the "polyethylenimine or graft modified polyethylenimine carbon dioxide adduct" (forming a capsule-like structure), but that the interstices between the crystallites of the calcium carbonate particles will contain the "polyethylenimine or graft modified polyethylenimine carbon dioxide adduct" such that the adduct is largely within the calcium carbonate particles; if PEI is hydrophobically modified, the modified hydrophobic side chains tend to be distributed on the surface of the calcium carbonate particles due to surface tension, whereas the hydrophilic PEI has CO 2 The adduct segments then tend to be distributed within the calcium carbonate particles. Thus the calcium carbonate encapsulates the CO of hydrophilic "PEI 2 An adduct "segment, if the adduct is also grafted with hydrophobic side chains, the hydrophobic side chains are outermost on the calcium carbonate particles, encapsulating the CO of the hydrophilic" PEI "with the calcium carbonate particles 2 Adduct "segments. For simplicity of description, regardless of whether the PEI grafts the side chains or not, its CO is in the present invention 2 The adducts are said to be "encapsulated" in the calcium carbonate particles.
The carbon dioxide adduct foaming agent of the polyethyleneimine coated with calcium carbonate provided by the invention firstly uses calcium carbonate to carry out PEI or thinningCO of Water modified PEI 2 The adducts are encapsulated, and the encapsulated CO is prevented because the calcium carbonate is a rigid inorganic material 2 The adduct foaming agent molecules (high polymer) are mutually diffused and agglomerated, and the encapsulated CO can be prevented 2 Adduct blowing agent CO release 2 The amine groups formed later participate in the reaction of polyurethane (possibly causing uncontrollable mechanical properties, such as a large amount of amine groups participate in the reaction, which can lead to the increase of the crosslinking degree of the foam and the embrittlement of the foam); on the other hand, CO of hydrophobically modified PEI 2 The hydrophobic chains of the adducts also aid in the dispersion of the calcium carbonate in the polyurethane foam matrix and better serve the reinforcing function of the calcium carbonate particles.
In the present invention, the polyethyleneimine may be linear or branched. The molecular weight of the polyethyleneimine is not particularly limited, and even dimers of ethyleneimine (also called aziridine) may be used with CO 2 Forming adducts for the synthesis of calcium carbonate; however, the larger the molecular weight, the more remarkable the effect as a "microreactor", the smaller the particle diameter obtained, and generally, the molecular weight of the polyethyleneimine should be not less than 200. When the molecular weight of PEI is above 5000, nano-grade calcium carbonate particles can be obtained, and the optimized particle size can reach 50-500 nm.
The invention aims at providing a carbon dioxide adduct foaming agent of PEI and/or graft modified PEI coated by calcium carbonate, which is characterized in that the particle size of the calcium carbonate is 50 nm-10 mu m, and the carbon dioxide adduct foaming agent contains PEI or graft modified PEI with the mass content of 5-50%; the graft modified PEI contains a PEI segment of not less than 50% by mass, and the graft side chain of the graft modified PEI comprises at least one of the following structures:
(1) Polyethylene glycol oligomer;
(2) Containing at least one repeating unit of polypropylene glycol, polyoxetane, polytetrahydrofuran or polysiloxane;
(3) Silanes having 4 or more carbon atoms;
(4) A hydrocarbon group having 1 to 22 carbon atoms;
(5) A fluoroalkyl group having 1 to 22 carbon atoms.
Calcium carbonate can be synthesized in the aqueous phase when the PEI contains no grafted chains or the grafted chains are water soluble when the grafted chains are polyethylene glycol oligomers. The side chains (2) to (6) of the graft polymer of PEI are hydrophobic chains (wherein polypropylene glycol means poly (1, 3-propylene glycol) ether, and hereinafter polypropylene glycol means the same), and the mass ratio of the main chain PEI is not less than 50%, and the synthesis can be performed in a mixture of an organic solvent and water. During the synthesis of calcium carbonate, nucleation and crystal growth of calcium carbonate occurs in the PEI domain of the main chain, and hydrophobic side chains tend to be distributed on the surface of the calcium carbonate particles, which is beneficial to improving the dispersion of the calcium carbonate particles in the hydrophobic polymer. In the present invention, the calcium source of the synthetic calcium carbonate is derived from calcium hydroxide. CO of calcium hydroxide and (graft modified) PEI 2 The adducts react to form calcium carbonate, while the CO of PEI 2 The adduct is converted into PEI and is attached to the surface of the calcium carbonate particles and interpenetrated in the microcrystals of the calcium carbonate; the PEI-coated calcium carbonate particles were then placed in CO 2 In the atmosphere, the PEI and the grafting modified PEI absorb CO again 2 Generating corresponding CO 2 The adducts, the carbon dioxide adduct blowing agent of the calcium carbonate coated polyethyleneimine and/or the grafted modified polyethyleneimine is obtained.
It is a further object of the present invention to provide the use of a carbon dioxide adduct blowing agent of calcium carbonate coated polyethylenimine and/or graft modified polyethylenimine for the preparation of polyurethane foam. When PEI is not grafted, the calcium carbonate particles wrap the hydrophilic PEI, so that the PEI can be well dispersed in the polyurethane raw material; when PEI is grafted with polyethylene glycol, the surface of the obtained calcium carbonate particles contains polyethylene glycol chains (which belong to hydrophilic chains and can be dissolved in hydrophobic polyurethane raw materials), so that the calcium carbonate particles are particularly suitable for preparing polyurethane foam containing polyethylene glycol chains; when PEI grafts hydrophobic chains, the hydrophobic chains are distributed on the surface of the calcium carbonate particles, which is helpful for the CO of the calcium carbonate and PEI coated by the calcium carbonate 2 The adduct blowing agent is dispersed in the hydrophobic polyurethane material and acts as a blowing agent.
The aim of the invention can be achieved by the following technical scheme:
(1) Configuration ofCO of polyethylenimine or graft-modified polyethylenimine 2 Aqueous adduct solution: preparing polyethyleneimine or grafted polyethyleneimine into a water solution with a certain concentration, and introducing carbon dioxide to react until saturation;
(2) Preparing a clarified saturated calcium hydroxide aqueous solution, and dripping the calcium hydroxide aqueous solution into CO of polyethyleneimine under the stirring condition 2 Stirring the aqueous solution of the adduct for reaction for 6 hours, centrifugally washing and freeze-drying; or CO of (graft-modified) polyethyleneimine under stirring 2 Dropwise adding the adduct aqueous solution into the calcium hydroxide aqueous solution, stirring and reacting for 6 hours, centrifugally washing, and freeze-drying;
(3) Grinding the freeze-dried calcium carbonate particles and placing the ground calcium carbonate particles into an autoclave, and placing the ground calcium carbonate particles into a CO solution under the pressure of 0.1-10 MPa 2 And maintaining the pressure for 24 hours in the atmosphere to obtain the final calcium carbonate product.
In the above step, if the graft chain of the graft-modified polyethyleneimine is a hydrophobic chain, calcium carbonate may also be synthesized in a mixed solvent of an organic solvent/water, specifically, step (1) is changed to: CO of the configuration of polyethyleneimine or of the graft modification of polyethyleneimine 2 Organic solutions or suspensions of adducts: preparing polyethyleneimine or grafted polyethyleneimine into an organic solution with a certain concentration, and introducing carbon dioxide to react until the organic solution is saturated; the organic solution is at least one of tetrahydrofuran, diethyl ether, ethanol and methanol. The rest steps are unchanged.
The graft chain of the graft modified polyethyleneimine in the above technical scheme comprises at least one of the following structures:
(1) Polyethylene glycol oligomer;
(2) Containing at least one repeating unit of polypropylene glycol, polyoxetane, polytetrahydrofuran or polysiloxane;
(3) Silanes having 4 or more carbon atoms;
(4) A hydrocarbon group having 1 to 22 carbon atoms;
(5) A fluoroalkyl group having 1 to 22 carbon atoms.
The technical scheme of the invention will be further described through examples.
Unlike the prior art, the invention has the following advantages:
the invention uses the polyethylene imine or the CO of the graft modified polyethylene imine 2 Adducts as CO 2 The source of the synthesized calcium carbonate particles is that the obtained calcium carbonate particles are prepared by mixing polyethylene imine or CO of grafted modified polyethylene imine 2 The adduct is wrapped inside and plays a role of a foaming agent in the polyurethane foaming process; the composite foaming agent can be dispersed in polyurethane raw materials, and the calcium carbonate particles can prevent amine groups of polyethyleneimine from participating in polyurethane reaction; in addition, the grafted side chain of the grafted and modified PEI is helpful for stabilizing the calcium carbonate particles, so that the calcium carbonate particles are uniformly dispersed in the polyurethane raw material, and the reinforcing effect of the calcium carbonate particles is also helpful.
Drawings
FIG. 1 shows the chemical structural formula of side chain raw materials used for preparing graft-modified PEI in raw material preparation examples 1 to 16.
FIG. 2 nuclear magnetic resonance spectrum of the product of preparation example (5) of graft-modified polyethyleneimine raw material.
FIG. 3 is an infrared spectrum of the products of examples 1 to 6 and comparative example 1, wherein 712cm –1 The peak of (a) is a characteristic peak of calcite crystal form (see a peak marked with a symbol), and 745cm –1 Is characteristic of vaterite (see # labeled peak).
FIG. 4 is an X-ray diffraction pattern of the products of examples 1 to 6 and comparative example 1.
FIG. 5 is a graph of thermal weight loss of the products of examples 1-6 and comparative example 1.
FIG. 6 is a graph showing the particle morphology of the products of examples 1 to 6 and comparative example 1.
FIG. 7 shows X-ray diffraction patterns of examples 8 to 10.
FIG. 8 is a graph showing the morphology and particle size characterization results of the particles of examples 8-10, A is a scanning electron microscope; b is a transmission electron microscope image; c is the particle size distribution and zeta potential as measured by dynamic light scattering.
Fig. 9 is an external view of white materials (stored for 7 days) and the external view of the foam produced in application examples 1 to 5 and application comparative examples 1 and 2.
Fig. 10 is a scanning electron micrograph of foams prepared in application examples 1 to 5 and application comparative examples 1 and 2 and a calcium element plane distribution diagram of application examples 2 and 5. The scale of the low-multiple cell morphology graph is 1mm; the scale of the high-fold foam topography and calcium element face profile is 50 μm.
Detailed Description
The present invention will be described in detail with reference to examples. It is to be noted that all of these examples are for further explanation of the present invention and should not be construed as limiting the present invention. Some insubstantial modifications and adaptations of the invention as described above would be within the scope of the invention by those skilled in the art in light of the foregoing disclosure. In the following examples, "wt%" means mass percentage.
Preparation example of graft modified polyethylenimine raw material
Prior to the description of the specific examples, the preparation of a graft modified polyethyleneimine which is one of the starting materials according to the invention is described. The main chain nitrogen atom of the grafted modified polyethyleneimine is grafted with a side chain, and the grafted side chain is at least one of the following conditions:
(1) Polyethylene glycol oligomer;
(2) Containing at least one repeating unit of polypropylene glycol, polyoxetane, polytetrahydrofuran or polysiloxane;
(3) Silanes having 4 or more carbon atoms;
(4) A hydrocarbon group having 1 to 22 carbon atoms;
(5) A fluoroalkyl group having 1 to 22 carbon atoms.
The linking group between the grafted side chain and the nitrogen atom of the main chain being replaceable, the linking group being a 2-hydroxy-propylene (-CH) if the grafted side chain is derived from a glycidyl ether 2 CH(OH)CH 2 (-) -; if the grafted side chain is derived from a chlorinated hydrocarbon, the linking group is a covalent bond; if the grafted side chain is derived from a carboxylic acid, the linking group is an amide bond. Specifically, in the examples, the grafted side chains were derived from glycidyl ethers, bromohydrocarbons, iodohydrocarbons, fatty acids, the structures of which are shown in FIG. 1. These structures are for the purpose of illustrating the invention and those skilled in the art may select other graft-containing sidesChain compounds (e.g., chlorinated alkanes, etc.), provided that the compound reacts with amine groups of the polyethyleneimine to graft the side chains to the polyethyleneimine. The structure of the synthesized graft modified polyethyleneimine is shown in Table 1. The degree of grafting refers to the mole percent of the total N atoms of the pendant PEI grafted N atoms. Wherein the theoretical grafting degree is calculated by the mole ratio of amino groups on the main chain to epoxy groups on the side chains, and the actual grafting degree is calculated by the area ratio of the side chains to proton signals related to the main chain in the nuclear magnetic spectrogram.
The process conditions and steps for preparing examples (1) to (13) from the graft modified polyethyleneimine raw material are as follows: adding Polyethylenimine (PEI) into a reaction kettle, adding ethanol into the reaction kettle to ensure that the mass concentration of PEI is about 10%, completely dissolving PEI under the stirring condition, then adding a corresponding glycidyl ether compound (table 1, side chain raw materials, specific structures are shown in figure 1) to ensure that the theoretical grafting degree of a side chain accords with the numerical values listed in table 1, stirring at 50 ℃ for reacting for 15 hours, and then removing ethanol by rotary evaporation; firstly, adding 10 parts by volume of petroleum ether into the product after rotary evaporation to dissolve the product and unreacted glycidyl ether compound, and then adding 1/3 of distilled water based on the volume of petroleum ether to separate out grafted modified polyethyleneimine; and washing the separated grafted modified polyethyleneimine with petroleum ether for at least three times, removing petroleum ether by rotary evaporation, and drying to constant weight to obtain the product.
The process conditions and steps for preparing example (14) from the graft modified polyethyleneimine raw material are as follows: 1 molar part of polyethyleneimine, calculated as repeating units of polyethyleneimine, was dissolved in chloroform to a mass concentration of about 10%, and then 0.03 molar part of C was added 17 H 33 -COOH (fig. 1) and N, N' -Carbonyldiimidazole (CDI), theoretical grafting yield was 3%. Stirring and reacting for 12 hours under reflux, extracting with saturated saline water for 3 times, taking chloroform layer, removing solvent by rotary evaporation at 50deg.C, and oven drying at 75deg.C to obtain purified graft chain grafted polyethyleneimine product 3%C 17 H 33 -PEI。
Process conditions and Steps for preparing graft modified polyethylenimine feedstock example (15)The method comprises the following steps: 1 molar part of polyethyleneimine, calculated as repeating units of polyethyleneimine, was dissolved in chloroform to a mass concentration of about 10%, and then 0.03 molar part of C was added 2 F 3 Reflux-reacting for 3 hours, cooling to room temperature, extracting the reaction mixture with 5% aqueous sodium hydroxide solution equal to chloroform for three times, removing the water layer, washing with water until the pH value of the water layer is neutral, drying the organic layer with anhydrous sodium sulfate, and removing the solvent by vacuum rotary evaporation at 40 ℃ to obtain the corresponding graft chain modified polyethyleneimine 3%C 2 F 3 -PEI。
TABLE 1
The process conditions and steps for preparing example (16) from the graft modified polyethyleneimine raw material are as follows: taking 1 mole part of polyethyleneimine measured by repeating units of polyethyleneimine, dissolving the polyethyleneimine in chloroform to make the mass concentration about 10%, then adding 0.4 mole part of Bu-Br (figure 1), refluxing for 6 hours, cooling to room temperature, extracting the reaction mixture with 5% aqueous sodium hydroxide solution with the same volume as chloroform for three times, removing the water layer, washing until the pH value of the water layer is neutral, drying the organic layer with anhydrous sodium sulfate, removing the solvent by vacuum rotary evaporation at 40 ℃ to obtain 40% C of the corresponding side chain modified polyethyleneimine 4 -PEI。
From Table 1, it is clear that the actual grafting degree and the theoretical grafting degree of each product are very close, indicating that the grafting reaction proceeds very completely. The theoretical grafting degree is calculated by the molar ratio of the side chain to the main chain, and the actual grafting degree is calculated by the area ratio of the side chain to the main chain related proton signals in the nuclear magnetic spectrum. As shown in Table 1, the mass percentage of the grafted side chains of each product is between 5 and 50 percent, and the mass percentage of the corresponding PEI main chain is not less than 50 percent.
FIG. 2 is a nuclear magnetic resonance hydrogen spectrum (the solvent is deuterated chloroform) of preparation example (5) of a graft modified polyethyleneimine raw material. As is clear from the figure, the proton peak with chemical shift between 2.2 and 3ppm is CH adjacent to the N atom of the main chain 2 Mainly from the backbone of PEI. The characteristic peak of the side chain dipropylene glycol methyl ether (mPG 2-) is also evident (see peaks a, b in the figure), indicating that grafting was successful.
Examples 1 to 6
Examples 1 to 6 CO to Polyethyleneimine (PEI) Using saturated calcium hydroxide solution 2 The carbon dioxide adduct foaming agent of the polyethyleneimine coated with calcium carbonate is prepared by dripping the adduct solution, and comprises the following steps:
(1) PEI (branched structure) having a molecular weight shown in Table 2 was selected to be 10mL of an aqueous PEI solution having a concentration of 0.1g/mL, and CO was introduced at a rate of 1mL/min 2 Reacting for 1 day to obtain CO of PEI 2 Adducts (PEI-CO) 2 ) A solution for standby;
(2) 50-400 mL (shown in Table 1) of clarified saturated Ca (OH) was added dropwise with stirring at about 1000 rpm 2 Stirring the aqueous solution for reaction for 6 hours, centrifugally washing, and freeze-drying to obtain PEI-CO 2 Modified calcium carbonate particles.
(3) PEI-CO 2 The modified calcium carbonate particles were ground and placed in an autoclave at 0.5MPa CO 2 And maintaining the pressure for 24 hours in the atmosphere to obtain the final foaming agent product.
TABLE 2
Note that: m is M n Represents molecular weight, 25k represents molecular weight 25000, and so on; PEI-CO 2 The solution contains CO 2
510.08mg; at 25 ℃, the solubility of calcium hydroxide is 159mg per 100mL of water; the actual amount of calcium carbonate is derived from thermal weight loss data. Ratio 1 is "comparative example 1".
TABLE 3 Table 3
Note that: ratio 1 is "comparative example 1".
Comparative example 1
The procedure of comparative example 1 is the same as examples 1 to 6, except that the molecular weight of PEI used and clarified saturated Ca (OH) 2 The amount of the aqueous solution added was varied as shown in Table 2.
FIG. 3 shows the IR spectrum of the foaming agent prepared, and the PEI backbone 2935cm can be seen –1 And 2832cm –1 Stretching vibration peak of methylene and 3100-3300 cm –1 Amino peaks of (2); the asymmetric vibration peak of carbonate radical of calcium carbonate appears in 1400-1500 cm –1 Out-of-plane flexural vibration at 875cm –1 . The in-plane flexural vibration of carbonate is related to the crystal form of calcium carbonate, 712cm of which –1 The peak of (a) is a characteristic peak of calcite crystal form (see a peak marked with a symbol), and 745cm –1 Is characteristic of vaterite (see # labeled peak). Fig. 4 is an X-ray diffraction pattern of the prepared calcium carbonate, the crystal forms of which are consistent with infrared testing, example 4 being a mixed crystal form (containing 78.4% vaterite and 21.6% calcite), examples 1-3 being vaterite crystal forms, and comparative examples 1, 5 and 6 being calcite crystal forms.
FIG. 5 is a graph of thermal weight loss of the blowing agent prepared. Wherein the mass loss between 30 and 150 ℃ is the CO of PEI 2 The adducts release CO by heating 2 200-500 ℃ is the mass loss of PEI decomposition in the material, and the mass loss after 600 ℃ is CaCO in the material 3 Thermal decomposition occurs. Table 3 lists thermogravimetric data of each example and comparative example 1, from which the composition of the calcium carbonate prepared in each example can be analyzed. As is clear from Table 3, the obtained foaming agent was PEI CO 2 Adduct and calcium carbonate composition, mass of PEI and CO released by the adduct 2 The amount substantially corresponds to the theoretical amount (higher saturation); residue of calcium carbonate (CaO) and released CO 2 The molar ratio of (2) and the theoretical value (1:1) are very close. As can be seen from Table 3, the calcium carbonate content varies between 66 and 91% and the corresponding PEI CO 2 The adducts varied between 9 and 34%. Comparative example 1, however, contains up to 99% calcium carbonate and almost no PEI-containing CO 2 An adduct. Since the foaming temperature of polyurethane is about 100 ℃, the foaming effect is that the CO of PEI wrapped by calcium carbonate 2 The adduct, therefore the calcium carbonate obtained in comparative example 1, does not act as a foaming agent, because it contains PEI CO 2 Too little adduct (1%).
Fig. 6 is a topography of examples 1 to 6 and comparative example 1. From the graph, the morphology of the calcium carbonate with the vaterite structure as the main part is a spherical morphology consisting of spherical microcrystals, and the morphology is between 320 and 420 nm; the calcite structure is of a cauliflower-shaped irregular block shape (example 5) and an irregular block shape (example 6), calcium carbonate particles are composed of small microcrystal grains, and the grain size of the calcium carbonate particles can reach the micron level. Regardless of whether the resulting blowing agent is vaterite or calcite in crystalline form, it is composed of crystallites, with optional interstices between the crystallites to accommodate the CO of the PEI 2 The adduct blowing agent acts as a "package" for the adduct blowing agent. The calcium carbonate particles of comparative example 1 were smooth in surface and were not seen to have crystallites forming large particles and were unable to "encapsulate" the PEI CO 2 An adduct blowing agent.
From the results of examples 1 to 6 and comparative example 1, it was found that the crystal form and particle size of the obtained calcium carbonate can be controlled by the change in the molecular weight of PEI and the amount of calcium hydroxide added. Under the process conditions of the present group of examples, the addition amount of calcium hydroxide should not be too high, and the molar amount thereof should generally be controlled to be not more than that of the raw material PEI-CO 2 Medium CO 2 50% of the number of moles; comparative example 1 calcium hydroxide was in the molar amount of PEI-CO 2 Medium CO 2 Since the molar number of (4%) of the PEI-coated CO was not obtained in comparative example 1 2 The adduct foaming agent only gives pure calcium carbonate. The addition of calcium hydroxide consumes PEI-CO 2 CO in (b) 2 Allowing it to partially recover the amine structure of the polyethyleneimine. As in example 3, calcium hydroxide was added in an amount corresponding to PEI-CO 2 Medium CO 2 37% of the molar amount, i.e. PEI-CO after the reaction 2 37% of the chain links on the molecular chain are of an amino structure, and 63% of the chain links are still CO of polyethyleneimine 2 The adduct structure, the adduct structure and the adsorption force of the calcium carbonate are stronger, and the calcium carbonate particles are more easily wrapped. In addition, the higher the molecular weight of PEI, the more advantageous it is for the PEI to be encapsulated by the calcium carbonate particles. From the slaveTable 3 shows that the releasable CO of examples 1 to 4 2 Amount (from PEI-CO) 2 This part of CO 2 Can play the role of foaming), the particle size of the obtained calcium carbonate is smaller than 500nm and is a good foaming agent, and the particle size of the calcium carbonate is between 5.7 and 11.1 percent. Examples 1 to 6 therefore show that PEI has a relatively high molecular weight (e.g.10000 and 25000) and that the calcium hydroxide is added as raw material PEI-CO 2 Medium CO 2 Within 50% of the molar amount, a nanoscale foaming agent can be obtained.
Examples 7 to 10
This set of examples prepares CO of a calcium carbonate-coated graft modified polyethyleneimine in an aqueous phase 2 An adduct blowing agent. For example 7, the grafted PEI was derived from preparation example (1) of the grafted modified polyethyleneimine of Table 1, the grafted side chain was polyethylene glycol (PEG), which itself was water soluble. The synthesis formulation, process, conditions were the same as in examples 1-6 except that PEI was used as the source of Ca (OH) added dropwise to the preparation example (1) of the graft modified polyethyleneimine of Table 1 2 The amount of (2) was 50mL. The obtained calcium carbonate has a vaterite microsphere structure, the average particle diameter is 50nm, and stable colloid is formed in water; the thermal weight loss data are shown in Table 4, and the obtained foaming agent contains 40.45% PEI CO 2 The adduct and 59.55% calcium carbonate.
TABLE 4 Table 4
Note that: the sources of grafted PEI in the tables are shown in Table 1. The content of calcium carbonate is derived from CO 2 (CaCO 3 ) And the sum of the residual weights.
Examples 8 to 10 first synthesis of CO grafted PEI 2 Adducts of the graft-modified PEI obtained in preparation examples (4) to (6) of Table 1 were placed in a mortar in CO 2 Grinding into powder under atmospheric conditions, placing the powder into an autoclave, and adding CO at 0.6MPa 2 Maintaining pressure to continuously enable PEI and CO 2 Reacting for 24h to obtain grafted PEI-CO 2 White powder. Weighing the obtained grafted PEI-CO 2 10g each of the white powder was dissolved in 50mL of deionized waterIn which the dissolved grafted PEI-CO 2 Rapidly pouring 1000 rpm of 3L saturated Ca (OH) under stirring 2 In water solution, reacting overnight at room temperature to obtain white emulsion, rotary evaporating at 50deg.C for 2h, separating at 8000 rpm for 5min to obtain white precipitate, freeze drying the precipitate, grinding into powder, placing in autoclave, and adding CO at 0.6MPa 2 Maintaining the pressure for 24 hours under the atmosphere to ensure CaCO 3 PEI and CO in (E) 2 Fully reacting to obtain the CO of the grafted PEI wrapped by the calcium carbonate 2 An adduct blowing agent.
Fig. 7 shows X-ray diffraction patterns of examples 8 to 10, in which three calcium carbonates are mainly calcite. The present set of examples uses CO from PEI to be grafted 2 The foaming agent product is prepared by adding the adduct aqueous solution into the calcium hydroxide aqueous solution, and Ca (OH) is prepared in the reaction process 2 Is excessive, PEI-CO 2 CO in (b) 2 All of the reaction involved, only calcite crystal forms could be obtained, but vaterite crystal forms could not be obtained. Fig. 8 shows the morphology (a and B) and the particle size distribution (C) of examples 8 to 10, and as can be seen from the scanning electron microscope (fig. 8A), the microcrystalline particles are composed of aggregates of different sizes, and the transmission electron microscope (fig. 8B) shows that the crystal particles have a block structure (characteristic morphology of calcite) and the particle size is in the nanometer scale. The resulting blowing agent particles may be dispersed in water to form a colloid, the particle size distribution of which is analyzed by a dynamic light scattering particle size analyzer, and the result is shown in fig. 8C, which has an average particle size of between 100 and 200nm and a surface potential of between 20 and 24 millivolts.
Thermogravimetric analysis was performed on the calcium carbonate prepared in this group of examples, and the spectrum is similar to that of fig. 5, and specific thermogravimetric data are shown in table 4. As can be seen from the table, the calcium carbonate content of this group of examples is between 59 and 70%, corresponding to the CO of the grafted PEI 2 The adduct is between 30 and 41%.
Examples 11 to 22
This set of examples further synthesizes CO of various calcium carbonate-coated grafted polyethyleneimines 2 The adduct foaming agent is synthesized into PEI-CO in organic solvent 2 Then, calcium hydroxide saturated solution is added dropwise to prepare the corresponding foaming agent product. Grafting of desiredThe modified PEI was derived from the preparation examples of Table 1, as shown in Table 5. 1 part by mass of grafted PEI shown in Table 5 was dissolved in a corresponding solvent to prepare a 10% by mass solution, and CO was introduced into the obtained solution 2 Reacting for 24h under stirring to obtain the CO grafted with PEI 2 The adduct suspension (semitransparent, dynamic light scattering test, particle size of 100-400 nm, and the obtained external hydrophobic nanoparticle with hydrophilic inside and CO with PEI inside 2 Adducts, external hydrophobic chains). Finally, CO of the obtained grafted PEI 2 Ca (OH) was added dropwise to the adduct suspension 2 The added mass parts are 100 times of the mass parts of PEI, white precipitate is obtained after the dripping is finished, the stirring reaction is continued for 1h, and the paste is obtained after the filtering; the resulting paste was resuspended in 100 parts of tetrahydrofuran, filtered again, and finally 100 parts of water washed and filtered to give a paste. Freeze drying the paste, grinding into powder, placing in autoclave, and adding CO at 0.6MPa 2 Maintaining the pressure for 24 hours under the atmosphere to ensure CaCO 3 PEI and CO in (E) 2 Fully reacting to obtain the CO of the grafted polyethyleneimine wrapped by the calcium carbonate 2 An adduct blowing agent. The resulting blowing agent may be suspended in an organic solvent (tetrahydrofuran, chloroform, diethyl ether, etc.).
TABLE 5
Note that: the sources of the grafted PEI in the table are shown in table 1; v and C in the tables represent vaterite and calcite, respectively; "80V+20C" means that the composition contains 80% vaterite and 20% calcite, and so on.
Table 5 shows the calcium carbonate content, particle size and crystal form data of the obtained products. The calcium carbonate particles obtained from the table are mainly of vaterite structure, and the content of calcium carbonate is 50-95%; correspondingly, the carbon dioxide adducts of the graft-modified polyethyleneimine are between 5 and 50%. The grain diameter of the obtained calcium carbonate is between 50nm and 10 mu m; when the molecular weight of the PEI main chain in the graft-modified PEI is 5000 or more (examples 13, 14 and examples 17 to 21), the particle size of the resulting calcium carbonate is 50 to 500nmCO of grafted modified PEI coated with nano-scale calcium carbonate 2 An adduct blowing agent.
Application examples 1 to 10
This set of application examples utilizes the blowing agent prepared in the previous examples to prepare polyurethane foams. The formulation of the foam prepared is shown in Table 6 (this formulation is only used to illustrate the foaming effect of different foaming agents, and the foaming formulation can be adjusted according to different purposes of use). Table 6 only shows the white stock (formulation other than isocyanate component) formulation, wherein the total amount of polyether is 100 parts by mass; wherein the source and amount of blowing agent are shown in Table 7. 105.73 parts by mass of polymethylene polyphenyl isocyanate, which is named Wannate PM-200 and has an NCO mass fraction of 30.5% to 32%, was used as a black material in each application example. The polyethers 4110 and the polyethers MN-450 in the white material are from the company Zigbori chemical Co. The remaining components (excluding blowing agent) were from adult high-end polymer company, inc.
The processes of application examples 1 to 10 are as follows: white materials are prepared according to the formula shown in Table 6, 1000 revolutions per part is stirred for 5 minutes, PM-200 is added after the mixture is stored for 7 days at room temperature, the mixture is stirred and mixed for 20 seconds at 1000 revolutions per part, and the mixture is poured into an open container and foamed freely at room temperature. White stock without blowing agent was also used for foaming to prepare blank samples.
TABLE 6
TABLE 7
Note that: the blank was not externally added with foaming agent.
Comparative application examples 1 and 2
CO of grafting modified PEI with water and not coated with calcium carbonate 2 Adducts (3% mPPG 2-PEI-CO) 2 ) As a foaming agent, a polymer was prepared by the process of application examples 1 to 10 (the formulations are shown in tables 6 and 7)Urethane foam.
Table 7 shows the density and mechanical properties of the foams prepared in the application examples and comparative application examples, and the stability of the foam raw material white stock. Application examples 6 and 7 use CO of ungrafted modified PEI 2 The foaming agent prepared by the adduct has poor stability in white materials for only 10 days; however, the foaming agent does not agglomerate after delamination, and can be easily redispersed in white materials by stirring. The rest of the foaming agent adopts a grafted chain, so that the dispersibility in white materials is relatively good. As can be seen from the data in the table, the density of the foam added with the foaming agent is smaller than that of the blank (the blank raw material contains a small amount of water, and the foam can be prepared without adding the foaming agent), which shows that the added foaming agent plays a role in foaming. Figure 9 shows the white material appearance (7 days of storage) and the appearance of the foam produced for a portion of the application examples and the comparative examples. As can be seen from the figure, the foam appearance of comparative application example 1 was severely cracked due to 3% mPPG2-PEI-CO 2 After the foaming agent is dispersed in the white material, the viscosity of the system is greatly increased, the foaming process is seriously disturbed, and the appearance of the foam is poor. Application examples 1 to 5 mPG 2-PEI-CO 2 As blowing agent (with a change in the degree of grafting), except that according to the process of the invention the adduct blowing agent is encapsulated inside the calcium carbonate particles; in this case, the appearance of the foam obtained was smooth, indicating that the encapsulated calcium carbonate particles avoid CO of the internal polyethyleneimine 2 The adduct interferes with the foaming process so that foaming can proceed normally. In addition, the foams prepared in the application examples (application examples 1 to 4) were all larger than the foams prepared by foaming with water (comparative application example 2) at approximately similar densities, indicating that the calcium carbonate particles exert a reinforcing effect on the foams. The strength of application example 5 is reduced, on the one hand, because the density of the foam is lower (strength naturally decreases); on the other hand, the foam has higher addition of the foaming agent, which reaches 68 percent of polyether in the white material, and the excessive addition of the foaming agent (calcium carbonate) does not play a role in reinforcement.
FIG. 10 is a scanning electron micrograph of the foams prepared in application examples 1 to 5 and comparative examples 1 and 2, each of which shows a closed cell structure, and application example 5 shows that cells are somewhat brittle and chipped when cut because of an excessively high calcium carbonate content. The enlarged pictures of application examples 1 to 5 show a uniform distribution of calcium carbonate particles. By scanning the calcium element by X-ray energy dispersive spectrometry, it can be seen that the distribution of the calcium element foam of application example 2 is uniform, i.e. the distribution of the calcium carbonate particles is uniform, which uniform distribution is beneficial for the calcium carbonate particles to exert an enhancing effect; in application example 5, calcium carbonate particles were partially agglomerated due to excessive addition of the foaming agent, so that the distribution of calcium was not very uniform. Therefore, the mechanical strength of application example 5 was lowered. The application examples fully illustrate that the carbon dioxide adduct foaming agent of the polyethyleneimine and/or the grafted modified polyethyleneimine coated with calcium carbonate prepared by the invention can be used for polyurethane foaming, and on one hand, the calcium carbonate coats the carbon dioxide adduct of the polyethyleneimine and/or the grafted modified polyethyleneimine to prevent the carbon dioxide adduct from affecting the foaming process of the polyurethane; on the other hand, the carbon dioxide adduct of the grafted modified polyethyleneimine also regulates and controls the crystal form and the particle size of the calcium carbonate, and the grafted side chain improves the dispersibility of the calcium carbonate in polyurethane raw materials, thereby being more beneficial to the strengthening effect of calcium carbonate particles.
The foregoing is a further detailed description of the invention in connection with specific/preferred embodiments, and is not intended to limit the practice of the invention to such description. It will be apparent to those skilled in the art that several alternatives or modifications can be made to the described embodiments without departing from the spirit of the invention, and these alternatives or modifications should be considered to be within the scope of the invention.
Claims (4)
1. A carbon dioxide adduct foaming agent of polyethyleneimine and/or graft modified polyethyleneimine coated with calcium carbonate, characterized in that the particle size of the calcium carbonate is 50 nm-10 μm, and the carbon dioxide adduct of polyethyleneimine or graft modified polyethyleneimine contains 5-50% of mass content; the molecular weight of the polyethyleneimine is not less than 200; the graft modified polyethyleneimine contains a polyethyleneimine segment in an amount of not less than 50% by mass, and a graft side chain of the graft modified polyethyleneimine includes at least one of the following structures:
(1) Polyethylene glycol oligomer;
(2) Containing at least one repeating unit of polypropylene glycol, polyoxetane, polytetrahydrofuran or polysiloxane;
(3) Silanes having 4 or more carbon atoms;
(4) A hydrocarbon group having 1 to 22 carbon atoms;
(5) A fluoroalkyl group having 1 to 22 carbon atoms;
the carbon dioxide adduct foaming agent of the calcium carbonate-coated polyethyleneimine and/or the grafted modified polyethyleneimine is prepared by the following steps:
(1) CO of the configuration of polyethyleneimine or of the graft modification of polyethyleneimine 2 Aqueous adduct solution: preparing polyethyleneimine or grafted modified polyethyleneimine into aqueous solution with a certain concentration, and introducing carbon dioxide to react until saturation;
(2) Preparing a clarified saturated calcium hydroxide aqueous solution, and dripping the calcium hydroxide aqueous solution into CO of the polyethyleneimine or the graft modified polyethyleneimine under the stirring condition 2 Stirring the aqueous solution of the adduct for reaction for 6 hours, centrifugally washing and freeze-drying; or CO of the polyethyleneimine or the graft modified polyethyleneimine under stirring 2 Dropwise adding the adduct aqueous solution into the calcium hydroxide aqueous solution, stirring and reacting for 6 hours, centrifugally washing, and freeze-drying;
(3) Grinding the freeze-dried calcium carbonate particles and placing the ground calcium carbonate particles into an autoclave, and placing the ground calcium carbonate particles into a CO solution under the pressure of 0.1-10 MPa 2 Maintaining the pressure for 24 hours in the atmosphere to obtain a final calcium carbonate product;
in the above step, if the graft chain of the graft modified polyethyleneimine is a hydrophobic chain, calcium carbonate is synthesized in a mixed solvent of an organic solvent/water.
2. A carbon dioxide adduct of calcium carbonate-coated polyethyleneimine and/or graft-modified polyethyleneimine according to claim 1, wherein the calcium carbonate has a particle size of 50nm to 500nm.
3. A carbon dioxide adduct blowing agent of a calcium carbonate-coated polyethyleneimine and/or a graft-modified polyethyleneimine according to claim 1, wherein the polyethyleneimine has a molecular weight of not less than 5000.
4. Use of a carbon dioxide adduct of a calcium carbonate-coated polyethyleneimine and/or a graft modified polyethyleneimine as claimed in any of claims 1 to 3 as blowing agent for the preparation of polyurethane foam.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN107880306A (en) * | 2017-09-30 | 2018-04-06 | 四川大学 | Hydrophobically modified polyethyleneimine foaming agent |
| CN112457520A (en) * | 2019-09-09 | 2021-03-09 | 四川大学 | Preparation method and application of polyurethane foaming mixture |
| CN114507362A (en) * | 2022-03-17 | 2022-05-17 | 四川大学 | Modified polyethyleneimine carbon dioxide adduct microsphere foaming agent prepared by spraying method |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN107880306A (en) * | 2017-09-30 | 2018-04-06 | 四川大学 | Hydrophobically modified polyethyleneimine foaming agent |
| CN112457520A (en) * | 2019-09-09 | 2021-03-09 | 四川大学 | Preparation method and application of polyurethane foaming mixture |
| CN114507362A (en) * | 2022-03-17 | 2022-05-17 | 四川大学 | Modified polyethyleneimine carbon dioxide adduct microsphere foaming agent prepared by spraying method |
Non-Patent Citations (1)
| Title |
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| Carbon dioxide adduct from polypropylene glycol grafted polyethyleneimine as a climate-friendly blowing agent for polyurethane foams;Yuanzhu Long et al.;Carbon dioxide adduct from polypropylene glycol grafted polyethyleneimine as a climate-friendly blowing agent for polyurethane foams;第55卷;第6494-6503页 * |
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