阅读说明：本技术 采用微通道反应器合成缩二脲多异氰酸酯的方法及其应用 (Method for synthesizing biuret polyisocyanate by using microchannel reactor and application thereof ) 是由 谭伟民 狄志刚 史立平 雒新亮 王亚鑫 郁飞 刘仲阳 饶兴兴 何毅 于 2020-11-16 设计创作，主要内容包括：本发明公开了一种采用微通道反应器合成缩二脲多异氰酸酯的方法及其应用。它是由选自脂肪族二异氰酸酯和脂环族二异氰酸酯的至少一种二异氰酸酯与缩二脲化试剂在增溶剂和乳化剂的作用下经微通道反应器反应获得。该缩二脲多异氰酸酯含有包括缩二脲结构的三异氰酸酯预聚物和整个反应中间体中含缩二脲基的化合物,该缩二脲多异氰酸酯具有不低于60wt％的缩二脲结构的三异氰酸酯预聚物含量。均匀混合成一相的反应原料液结合微通道的强传质传热效应减少了原料中脂肪族二异氰酸酯和脂环族二异氰酸酯的投料量,同时减少反应时间降低副反应和副产物,降低后期分离成本大大提高了缩二脲多异氰酸酯反应过程的经济性和竞争力。(The invention discloses a method for synthesizing biuret polyisocyanate by using a microchannel reactor and application thereof. It is prepared by reacting at least one diisocyanate selected from aliphatic diisocyanate and alicyclic diisocyanate with biuretizing agent under the action of solubilizer and emulsifier through a microchannel reactor. The biuret polyisocyanate contains a triisocyanate prepolymer including a biuret structure and a compound containing a biuret group in the entire reaction intermediate, the biuret polyisocyanate having a content of triisocyanate prepolymer having a biuret structure of not less than 60% by weight. The reaction raw material liquid which is uniformly mixed into one phase combines the strong mass transfer and heat transfer effects of the micro-channel, so that the feeding amount of aliphatic diisocyanate and alicyclic diisocyanate in the raw materials is reduced, the reaction time is reduced, the side reaction and the by-product are reduced, the later separation cost is reduced, and the economical efficiency and the competitiveness of the reaction process of the biuret polyisocyanate are greatly improved.)

1. The method for synthesizing the biuret polyisocyanate by adopting the microchannel reactor is characterized by comprising the following steps of:

step 1, building a microchannel reactor, wherein the microchannel reactor comprises a mixed liquid storage tank, a water and solubilizer mixed liquid storage tank which are connected by pipelines; the device comprises a first metering pump, a second metering pump, a first pressure regulator, a second pressure regulator, a first Corning straight channel preheating module, a second Corning straight channel preheating module, a Corning channel module, a cooling coil water bath and a product collecting device;

step 2, mixing diisocyanate and an emulsifier, putting the mixture into a mixed solution storage tank, pumping the mixture into a first pressure regulator through a first metering pump, and then entering a first Corning straight channel preheating module for preheating;

step 3, pumping the mixed liquid of the solubilizer and the biuretizing agent into a second pressure regulator through a second metering pump in a storage tank, and then entering a second Corning straight channel preheating module for preheating;

and 4, pumping the two preheated materials into a Corning channel module for mixing reaction at the reaction temperature of 80-130 ℃ for 15-60min to obtain the compound shown in the general formula (I)Or as shown in the general formula (II)The biuret polyisocyanate of (a); and when the mass fraction of-NCO in the whole reaction liquid is 13-39%, ending the reaction, degassing biuret polyisocyanate, and removing unreacted diisocyanate in the reaction liquid by adopting a separation technology, wherein the concentration of the unreacted diisocyanate in the obtained product is not higher than 0.5%.

2. The method for synthesizing biuret polyisocyanate according to claim 1, characterized in that said Corning channel module in step 1 is a Corning straight channel module or a Corning heart channel module.

3. The method for synthesizing biuret polyisocyanates using microchannel reactor as claimed in claim 1, wherein said diisocyanate in step 2 is one or more of aliphatic diisocyanate or cycloaliphatic diisocyanate, and the molar ratio of diisocyanate to biuretizing agent is 3-10: 1.

4. the process for synthesizing biuret polyisocyanates using microchannel reactor as claimed in claim 3, characterized in that the molar ratio of said diisocyanate to biuretizing agent in step 2 is 3.5 to 4.5: 1.

5. the method for synthesizing biuret polyisocyanates using microchannel reactor as claimed in claim 1, characterized in that the weight ratio of said emulsifier to diisocyanate in step 2 is 0.1% to 2%, thereby obtaining a mixture containing unreacted diisocyanate and emulsifier; the emulsifier is one or more of polyoxyethylene oleate, polyoxyethylene palmitat, polyoxyethylene stearate, polyoxyethylene laurate, polyoxyethylene vegetable oil, alkyl aryl sulfonate or polyoxyethylene cetyl alcohol.

6. The method for synthesizing biuret polyisocyanates using microchannel reactor as claimed in claim 1, characterized in that the weight ratio of said solubilizing agent in step 3 to diisocyanate is 0.1-3%; wherein the solubilizer is represented by the structural formula (2) R₁-COO-R₂Or structural formula (3) R₃-(OCH₂CH₂)₃-R₄One or more of R and R are mixed₁And R₂Each independently represents an alkyl group having 1 to 5 carbon atoms, R₃And R₄Represents an alkyl group or an acyl group having 1 to 4 carbon atoms.

7. The method for synthesizing biuret polyisocyanates using microchannel reactor as claimed in claim 6, characterized in that said solubilizing agent is butyl acetate, amyl acetate, butyl propionate or triethylene glycol type solvent compound.

8. The method for synthesizing biuret polyisocyanate according to claim 7, wherein said triethylene glycol type solvent compound is triethylene glycol dipropionate, triethylene glycol di-2-methacrylate, triethylene glycol monoethyl ether methacrylate or triethylene glycol dimethyl ether.

9. The process for synthesizing biuret polyisocyanates using microchannel reactors as claimed in claim 1, characterized in that the separation technique used in step 4 is rotary concentration, thin-film evaporation or molecular distillation.

10. Use of the synthetic biuret polyisocyanates according to claim 1 for the production of coatings.

Technical Field

The invention belongs to the technical field of chemical organic synthesis processes, and particularly relates to a method for synthesizing biuret polyisocyanate by using a microchannel reactor and application thereof.

Background

The biuret polyisocyanates are obtained by reacting at least one diisocyanate selected from aliphatic diisocyanates and alicyclic diisocyanates with a biuretizing agent, and are mainly prepolymers having a biuret structure formed by reacting isocyanates with water. The isocyanate monomer has high steam pressure and volatility, so that the toxicity is high in the construction process, the biuret prepared by the isocyanate monomer can be used for preparing coatings with low toxicity, quick drying, good mechanical properties, good chemical resistance and good weather resistance, and particularly, the product has the characteristic of no yellowing and is mainly used for preparing yellowing-resistant polyurethane coatings, adhesives and elastomers. In recent years, some novel polyurea materials prepared based on the reaction of isocyanate and water are widely researched, and the novel polyurea materials have excellent mechanical properties, porous properties and good energy absorption and sound wave attenuation capabilities, so that the novel polyurea materials have wide application prospects in the fields of adsorption, shock resistance, sound insulation and the like.

The prior synthetic method of biuret polyisocyanate mainly comprises the following steps: (1) spraying method: the biuretizing agent and isocyanate are reacted in a spraying mode to generate triisocyanate prepolymer with a biuret structure, and unreacted isocyanate monomer is removed by short-path distillation. However, the spray particle size has a large influence on the composition of the product ingredients (2) water crystallization: although the amount of the raw materials to be fed can be reduced, the content of the triisocyanate prepolymer having a biuret structure is low. (3) Gas phase method: the process has the lowest content of unreacted monomers and the highest yield of triisocyanate prepolymer with a biuret structure, but has poor repeatability and has higher requirements on equipment. The above processes all have a problem that it is difficult to control the conversion of raw materials into desired products, wherein the resulting biuret polyisocyanate has an undesirable one type of biuret belonging to the above reaction intermediate and a plurality of N isocyanate prepolymer byproducts belonging to the biuret structure formed by the above-mentioned biuret isocyanuric acid side reaction, such as tetraisocyanate prepolymer of biuret structure and pentaisocyanate prepolymer of biuret structure. The reason is that-NCO groups can react with chemical substances containing active hydrogen, the triisocyanate prepolymer with a biuret structure is shown as a structural formula (1), the-NCO groups at the outer ends of the triisocyanate prepolymer continuously react with water to obtain byproducts shown as a structural formula (4), wherein R is shown as a structural formula₅、R₆And R₇Each independently represents the residual group of aliphatic diisocyanate or alicyclic diisocyanate monomer after one-NCO group is removed; or n (n is more than or equal to 1) aliphatic diisocyanate or alicyclic diisocyanate monomers react with active hydrogen, and then a residual group after one-NCO group is removed. Taking pentamethylene-1, 5-diisocyanate (PDI) as an example: the structural formula of the by-product (4-1) is R₅And R₇Representing the residue of a PDI monomer after removal of one-NCO group, R₆Representing the residual group after reaction of PDI monomer and active hydrogen and then removing one-NCO group; the structural formula of the by-product (4-2) is R₅And R₇Denotes the residue R of a PDI monomer after removal of one-NCO group₆Representing the residual groups after the reaction of two PDI monomers and active hydrogen; the structural formula of the by-product (4-3) is R₅And R₇To representResidual group R of PDI monomer after one-NCO group is removed₆Representing the residual group after reaction of three PDI monomers and active hydrogen and then removal of one-NCO group. The biuret group-containing compounds comprise triisocyanate prepolymer with a biuret structure and byproducts, the existence of the biuret prepolymer in the synthesis process of biuret polyisocyanate has a remarkable influence on the product quality, and the comprehensive index fullness of the product is rapidly reduced due to the increase of the content of the byproducts. The reaction formula (I) for synthesizing the polyisocyanate biuret by using the PDI monomer is shown in the specification, when the molar ratio of PDI to water is 3:1, just one mole of diisocyanate biuret is generated, but actually, the aliphatic diisocyanate, the alicyclic diisocyanate and the water are mixed and layered, the two reactants cannot be uniformly mixed in a reactor, so that the local water content is too high, more intermediate products are generated, and the mechanism is shown in the formula (II), the formula (III) and more by-product structural formulas are shown in the formula (4), meanwhile, the isocyanate monomer cannot be contacted with the water to be not reacted in other parts, so that the obtained product has low content of the polyisocyanate biuret and high by-product content, so that the quality of the product is reduced, and the main bottleneck for limiting the application of the product is also realized.

The advantages of the microchannel reactor are rapid and well controlled mixing, precise temperature control, rapid and effective quality and heat transfer, reduced reagent consumption and safer conditions, and under the condition of mixing into one phase under the action of diisocyanate, biuretizing agent, solubilizer and emulsifier, the diisocyanate and the biuretizing agent react better according to an ideal proportion to reduce the proportion of by-products, improve the proportion of isocyanate biuret products and improve the quality and the reaction yield of the products.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention provides a method for synthesizing biuret polyisocyanate by using a microchannel reactor and application thereof, which combines an automatic reaction with a microreactor, effectively improves the utilization rate of products and restrains the generation of byproducts. Meanwhile, the method for preparing the polyurea material by reacting the isocyanate and the water has mild process and simple and convenient operation, and can avoid the defect that a monomer is required in the traditional method, so the method has higher industrial application value.

The method for synthesizing the biuret polyisocyanate by adopting the microchannel reactor comprises the following steps:

step 1, building a microchannel reactor, wherein the microchannel reactor comprises a mixed liquid storage tank, a water and solubilizer mixed liquid storage tank which are connected by pipelines; the device comprises a first metering pump, a second metering pump, a first pressure regulator, a second pressure regulator, a first Corning straight channel preheating module, a second Corning straight channel preheating module, a Corning channel module, a cooling coil water bath and a product collecting device;

step 2, mixing diisocyanate and an emulsifier, putting the mixture into a mixed solution storage tank, pumping the mixture into a first pressure regulator through a first metering pump, and then entering a first Corning straight channel preheating module for preheating;

step 3, pumping the mixed solution of the solubilizer and the biuretizing agent into a second pressure regulator through a second metering pump in a storage tank, and then entering a second Corning straight channel preheating module for preheating;

and 4, pumping the two preheated materials into a Corning channel module for mixing reaction at the reaction temperature of 80-130 ℃ for 15-60min to obtain the compound shown in the general formula (I)Or as shown in the general formula (II)The biuret polyisocyanate of (a); ending when the mass fraction of-NCO in the whole reaction liquid is 13-39%And (3) performing reaction, namely degassing the biuret polyisocyanate, and removing unreacted polyisocyanate in the reaction liquid by adopting a separation technology, wherein the concentration of the unreacted diisocyanate in the obtained product is not higher than 0.5%.

As a modification, the Corning channel module in step 1 is a Corning straight channel module or a Corning heart-shaped channel module.

The improvement is that the diisocyanate in the step 2 is one or more of aliphatic diisocyanate or alicyclic diisocyanate, and the molar ratio of the diisocyanate to the biuretizing agent is 3-10: 1.

in a further improvement, the molar ratio of diisocyanate to biuretizing agent in step 2 is 3.5 to 4.5: 1.

the improvement wherein the diisocyanate is pentamethylene diisocyanate and the biuretizing agent is water.

As a modification, the weight ratio of the emulsifier to the diisocyanate in step 2 is 0.1% to 2%, thereby obtaining a mixture containing unreacted diisocyanate and the emulsifier; the emulsifier is one or more of polyoxyethylene oleate, polyoxyethylene palmitat, polyoxyethylene stearate, polyoxyethylene laurate, polyoxyethylene vegetable oil, alkyl aryl sulfonate or polyoxyethylene cetyl alcohol.

The improvement is that in the step 3, the weight ratio of the solubilizer to the diisocyanate is 0.1-3%; wherein the solubilizer is represented by the structural formula (2) R₁-COO-R₂Or structural formula (3) R₃-(OCH₂CH₂)₃-R₄One or more of R and R are mixed₁And R₂Each independently represents an alkyl group having 1 to 5 carbon atoms, R₃And R₄Represents an alkyl group or an acyl group having 1 to 4 carbon atoms. That is, the compound of the formula (2) or the formula (3) does not react with the isocyanate group in the diisocyanate.

In a further refinement, the solubilizer is butyl acetate, amyl acetate, butyl propionate or a triethylene glycol type solvent compound.

In a further improvement, the triethylene glycol type solvent compound is triethylene glycol dipropionate, triethylene glycol di-2-methacrylate, triethylene glycol monoethyl ether methacrylate or triethylene glycol dimethyl ether.

As a modification, the separation technique employed in step 4 is rotary concentration, thin-film evaporation or molecular distillation.

The application of the synthesized biuret polyisocyanate in preparing paint.

Has the advantages that:

compared with the prior art, the method for synthesizing biuret polyisocyanate by using the microchannel reactor and the application thereof have the following advantages:

at least one diisocyanate according to the invention selected from the group consisting of aliphatic diisocyanates and cycloaliphatic diisocyanates, obtained by reaction with a biuretizing agent, the biuret polyisocyanates being as follows:

general formula (I)Or general formula (II)As shown in the drawings, the above-described,

(1) the biuret polyisocyanates contain biuret group-containing compounds including biurets that are intermediate products of the reaction of the diisocyanates and biuretizing agents, wherein the biurets are represented by the general formula (I): wherein each R independently represents an aliphatic group and an alicyclic group derived from the diisocyanate, and the biuret polyisocyanate has a triisocyanate prepolymer content of a biuret structure of not less than 60.0 wt%, based on the total weight of the biuret polyisocyanate and the biuret group-containing compound including biuret, wherein the triisocyanate prepolymer content of the biuret structure is defined as: in a gel permeation chromatogram of the biuret polyisocyanate containing an unreacted diisocyanate and the biuret group-containing compound, the area of the triisocyanate prepolymer peak of the biuret structure is a percentage of the total area of all peaks in the gel permeation chromatogram after excluding the peaks belonging to the unreacted diisocyanate;

(2) the biuret polyisocyanate has a light transmission of at least 90% measured at 430nm by using a sample cell of 2cm length.

A colorless, transparent biuret polyisocyanate is obtained by the process of the present invention, with a urea dimer content of not more than 0.4% by weight, preferably not more than 0.25% by weight, and a transmittance of the biuret polyisocyanate of at least 91% and with an unreacted diisocyanate concentration of not more than 1.5% by weight, preferably not more than 1% by weight, more preferably not more than 0.5% by weight. For the biuret polyisocyanates of the invention, the isocyanate group content is generally from 5 to 30% by weight; the number average molecular weight is generally 500-900; and a viscosity at 25 ℃ of generally 300-40000 mPa.s. The resulting polyisocyanates not only show excellent stability at low temperatures but also are color-free and are suitable for the production of coating compositions, adhesives, fiber-treating agents, sealants, water repellents, foams, elastomers and the like, which meet the quality requirements of the corresponding products for biuret polyisocyanates.

Drawings

FIG. 1 is an infrared chromatogram of a biuret pentamethylene diisocyanate biuret reaction solution obtained by the present invention;

FIG. 2 is a nuclear magnetic hydrogen spectrum of a biuret pentamethylene diisocyanate biuret reaction liquid obtained by the present invention;

FIG. 3 is a schematic flow diagram of a Corning straight-through channel reactor of the present invention, wherein 1-the mixed liquor storage tank; 2-a storage tank for mixed liquor of water and solubilizer; 3-a first metering pump, 4-a second metering pump, 5-a first pressure regulator, 6-a second pressure regulator; 7-a first Corning straight channel preheating module, 8-a second Corning straight channel preheating module; 9-Corning straight channel module; 10-cooling coil water bath; 11-a product collection device;

FIG. 4 is a schematic flow diagram of a Corning Heart Path reactor of the present invention; wherein, 1-mixed liquid storage tank; 2-a storage tank for mixed liquor of water and solubilizer; 3-a first metering pump, 4-a second metering pump, 5-a first pressure regulator, 6-a second pressure regulator; 7-a first Corning straight channel preheating module, 8-a second Corning straight channel preheating module; 12-a Corning heart channel module; 10-cooling coil water bath; 11-a product collection device;

FIG. 5 is a molecular gel chromatography spectrum of biuret pentamethylene diisocyanate obtained by the present invention.

Detailed Description

The present invention can be better understood from the following examples, which are provided for the purpose of illustration only, and the following properties were measured in the following examples, comparative examples and reference examples.

(1) Biuret content

The content of the triisocyanate prepolymer of the biuret structure in the biuret polyisocyanates of the present invention is defined as: the amount of the biuret structure triisocyanate prepolymer represented by the general formula (I) or the general formula (II) is 60 to 65 wt% based on the total weight of the biuret polyisocyanate and the biuret group-containing compound including biuret.

A sample of the biuret polyisocyanate used to measure the content of the biuret structure triisocyanate prepolymer was prepared by dissolving the biuret polyisocyanate in Tetrahydrofuran (THF) so that the final concentration of the biuret polyisocyanate in THF became 0.5 wt%. In order to measure the content of the biuret structure triisocyanate prepolymer of the biuret polyisocyanate in the reaction mixture, the reaction mixture was used as such as a sample.

A sample of the biuret polyisocyanate was subjected to Gel Permeation Chromatography (GPC) measurement under the conditions mentioned below, whereby a spectrum was obtained. The content of triisocyanate prepolymer of a biuret structure is measured as the area% of the triisocyanate prepolymer belonging to a biuret structure, i.e. the peak having a residence time corresponding to the molecular weight of 310 when the polyisocyanate is hexamethylene-1, 6-diisocyanate (HMDI), based on the total area of all peaks in the obtained spectrum (except the peak belonging to the unreacted diisocyanate).

Gel Permeation Chromatography (GPC) measurements were performed under the following conditions:

a chromatographic treatment machine: p230 type GPC-gel permeation chromatography system

A chromatographic column: KF-604, KF-603 and KF-602 connected in series

Carrier: THF (flow rate: 0.6ml/min)

A detector: a refractive index detector.

(2) Nuclear magnetic hydrogen spectrum analysis

The sample is firstly subjected to derivatization reaction with methanol, then dissolved in deuterated dimethyl sulfoxide (DMSO), and is carried out on a Bruker AV400 nuclear magnetic resonance spectrometer at room temperature, wherein the proton resonance frequency is 400.13MHz, the number of data points is 4096, the accumulation frequency is 12, and the relaxation delay time is 2 s.

(3) Infrared chromatography

In infrared spectrum, different groups have different absorbances at different wave number positions, and some groups can be identified by using the characteristic, and the content of the groups in a certain range is in linear relation with the electron current intensity. Operating conditions of Fourier infrared spectrum: the scanning times are 16 times, the resolution iS 4, K-K correction iS selected, the test wave number range iS 4000-.

(4) Concentration of unreacted diisocyanate

The unreacted diisocyanate concentration in the reaction mixture or biuret polyisocyanate is defined as the amount of unreacted diisocyanate and as a percentage (wt%) of the total weight of unreacted diisocyanate and biuret polyisocyanate (including the biuret group compound).

A sample of the reaction mixture or biuret polyisocyanate was prepared in the same manner as described in (1) above. A sample of the reaction mixture or biuret polyisocyanate was subjected to GPC under the conditions described in (1) above, thereby obtaining a chromatogram. The diisocyanate concentration is determined as the area% of the peak belonging to the diisocyanate (i.e. the peak whose residence time corresponds to a molecular weight of 168 when the diisocyanate is HMDI), based on the total area of all the peaks in the chromatogram obtained.

(5) Number average molecular weight

The number average molecular weight of the biuret polyisocyanate was measured by dissolving the biuret polyisocyanate in Tetrahydrofuran (THF) so that the final concentration of the biuret polyisocyanate in THF became 0.25 wt%. The prepared sample was subjected to GPC analysis to determine the number average molecular weight thereof. GPC was carried out under the same conditions as described in (1) above.

(6) Isocyanate group content

the-NH of NCO and di-n-butylamine can be utilized to react completely and generate urea quantitatively. The excess di-n-butylamine-toluene solution is used for reacting with NCO in a titration sample, the excess amine is back-titrated to an end point by using standard hydrochloric acid, and the NCO content in the sample can be calculated according to the reaction equilibrium, the volume and the concentration of the standard hydrochloric acid. The reaction equation is as follows:

chemical reagents and indicators

(a) Anhydrous di-n-butylamine-toluene solution: the solution has a molar concentration of 0.5mol/L, can be stored in a brown bottle, is protected from light and is not suitable for long-term storage. (b) Toluene, analytically pure, which needs to be handled dry. (c) Absolute ethanol, analytical grade, (d) hydrochloric acid (HCl) standard solution: diluting to a molar concentration of 0.5mol/L, GB 601-88. (e) Indicator (b): 0.1% wt of bromocresol blue in ethanol; also useful is a bromocresol green, at a concentration of 0.1% wt: dissolving 0.1g of bromocresol green in 1.5mL of NaOH aqueous solution with the molar concentration of 0.1mol/L, oscillating and dissolving, and then fixing the volume to 100 mL.

A250 mL conical flask with a stopper was filled with the appropriate amount of sample (accurate to 10-3g) and, if necessary, with anhydrous toluene to aid dissolution. Accurately measuring 25mL of di-n-butylamine-toluene solution, adding into a ground conical flask, washing the flask opening with anhydrous toluene, shaking uniformly, standing for 15 min, adding 10mL of ethanol, shaking uniformly, and stopping the reaction. 2-3 drops of indicator were added, at which time the solution appeared blue. Titration with a standard solution of hydrochloric acid until the blue color disappeared, the solution went from cyan to pale yellow with no color change in 1 minute, and the volume of hydrochloric acid consumed was recorded.

The NCO content of the product is expressed in terms of mass fraction and amine equivalent, respectively. Amine equivalent means the relative molecular mass per functional group in a molecule of a compound.

In the formula: n-molar concentration of Standard hydrochloric acid, mol/L

W-sample mass, g

V₁Titration of sample consumes volume of standard hydrochloric acid, mL

V₂Blank test consumes volume of standard hydrochloric acid, mL

0.04202-equivalent grams per millimole of-NCO groups

(6) Viscosity of the oil

The viscosity of the biuret polyisocyanate was determined at 25 ℃ using an E-type viscometer (model JK99B, manufactured and sold by Shanghai morning digital technology Equipment, Inc.).

(7) Transmittance of light

The transmittance of biuret polyisocyanates was measured with the aid of a visible and UV spectrophotometer ("722S visible spectrophotometer", manufactured and sold by the Qingdao Polymer environmental protection group, Inc.) using a sample cell of 2cm length at 430 nm.

(8) Storage stability of biuret polyisocyanates at 5 ℃

The biuret polyisocyanate was placed in a colorless, transparent glass vessel and sealed after purging the vessel with nitrogen. The glass containers were then stored at 5 ℃ for 1 day. The biuret polyisocyanate in the glass container was visually inspected to determine if the polyisocyanate became cloudy.

EXAMPLE 1 Corning straight-through channel reactor reaction with hexamethylene 1, 6-diisocyanate (HDI) and Water

(1) The device used is as follows: the Corning straight-going micro-channel reactor (Corning straight-going channel module + Corning straight-going reaction channel module) determines the connection mode of the micro-channel reactor by referring to FIG. 3, the number of mixed reaction modules is determined according to the flow rate and the reaction residence time, and the heat exchange medium is heat conduction oil.

(2) The reaction raw material hexamethylene 1, 6-diisocyanate: emulsifier: water: the volume ratio of the solubilizer is 125:1:5:30, wherein the mixed solution of hexamethylene 1, 6-diisocyanate and the emulsifier is pumped into a first pressure regulator 5 in a mixed solution storage tank 1 through a first metering pump 3 and then enters a first Corning straight channel preheating module 7, the mixed solution of water and the solubilizer enters a second Corning straight channel preheating module 8 in a mixed solution storage tank 2 of the turn solubilizer, is pumped into a second pressure regulator 6 through a second metering pump 4 and then enters a second Corning straight channel preheating module 8, and the heat exchanger temperature of the first Corning straight channel preheating module 7 and the second Corning straight channel preheating module 8 is set to be 98 ℃. Setting the volume flow rate ratio of the first metering pump 3 to the second metering pump 4 to be 3.5:1, pumping the two preheated materials into a Corning straight channel module 9 for mixing reaction, wherein the temperature of the Corning straight channel module 9 is 130 ℃, the reaction residence time is 900s, the pressure is 1.6bar, and after a reaction product passes through a cooling coil water bath 10, the reaction product flows out of the reactor in a continuous flow state and enters a product collecting device 11 (see attached figure 3).

(3) The reaction mixture obtained in the product collecting means 11 was fed into a wiped film evaporator (degree of vacuum 50 Pa; temperature 150 ℃ C.) to obtain biuret polyisocyanate by removing unreacted diisocyanate from the reaction mixture. For the isolated biuret polyisocyanate, its number average molecular weight is 678; the isocyanate group (NCO) content was 22.9% by weight; the unreacted diisocyanate concentration was 0.4 wt%; the content of triisocyanate prepolymer of biuret structure is not less than 60 wt%. The transmission and viscosity of the biuret polyisocyanate were 92% and 3850 mPas (25 ℃ C.), respectively. Furthermore, the biuret polyisocyanates did not become cloudy even after being subjected to storage stability tests at 5 ℃.

Example 2 Corning straight-through channel reactor reaction with pentamethylene 1, 5-diisocyanate (PDI) and Water

Steps (1) and (2) were the same as in example 1 except that hexamethylene 1, 6-diisocyanate was replaced with pentamethylene 1, 6-diisocyanate;

(3) the reaction mixture obtained in the product collecting means 11 was fed into a wiped film evaporator (degree of vacuum 50 Pa; temperature 150 ℃ C.) to obtain biuret polyisocyanate by removing unreacted diisocyanate from the reaction mixture. For the isolated biuret polyisocyanate, its number average molecular weight is 582; the isocyanate group content was 26.19 wt%; the unreacted diisocyanate concentration was 0.4% by weight. The transmittance and viscosity of the biuret polyisocyanate were 93% and 3400 mPas (25 ℃ C.), respectively.

Example 3 reaction of pentamethylene 1, 5-diisocyanate (PDI) and water in a Corning Heart-type channel reactor

(1) The device used is as follows: the Corning straight-moving micro-channel reactor (Corning straight-moving channel module + Corning heart-shaped reaction channel module) determines the connection mode of the micro-channel reactor by referring to FIG. 4, the number of mixed reaction modules is determined according to the flow rate and the reaction residence time, and the heat exchange medium is heat conduction oil.

(2) The reaction raw material pentamethylene 1, 5-diisocyanate: emulsifier: water: the volume ratio of the solubilizer is 125:1:5:30, wherein mixed solution of pentamethylene 1, 5-diisocyanate and the emulsifier enters a first Corning straight channel preheating module 7 after being pumped into a first pressure regulator 5 through a first metering pump 3 in a mixed solution storage tank 1, mixed solution of water and the solubilizer enters a second Corning straight channel preheating module 8 after being pumped into a second pressure regulator 6 through a second metering pump 4 in a mixed solution storage tank 2 of water and the solubilizer, and the temperature of heat exchangers of the first Corning straight channel preheating module 7 and the second Corning straight channel preheating module 8 is set to be 98 ℃. Setting the volume flow rate ratio of each first metering pump 3 to each second metering pump 4 to be 3.5:1, pumping the two preheated materials into a Corning heart-shaped channel module 12 for mixing reaction, wherein the temperature of the Corning straight-moving channel module 12 is 130 ℃, the reaction residence time is 600s, the pressure is 1.6bar, and after a reaction product passes through a cooling coil water bath 10, the reaction product flows out of the reactor in a continuous flow state and enters a product collecting device 11 (see figure 4).

(3) The reaction mixture obtained in the product collecting means 11 was fed into a wiped film evaporator (degree of vacuum 50 Pa; temperature 150 ℃ C.) to obtain biuret polyisocyanate by removing unreacted diisocyanate from the reaction mixture. For the biuret polyisocyanate isolated, its number average molecular weight is 692; the isocyanate group content was 26.78 wt%; the unreacted diisocyanate concentration was 0.3 wt%; the content of triisocyanate prepolymer of biuret structure is not less than 60 wt%. The transmission and viscosity of the biuret polyisocyanate were 94% and 3350 mPas (25 ℃ C.), respectively. Furthermore, the biuret polyisocyanates did not become cloudy even after being subjected to storage stability tests at 5 ℃.

The results of data obtained by measuring biuret polyisocyanate obtained after removing unreacted diisocyanate by Gel Permeation Chromatography (GPC) are shown in FIG. 5, and the following table shows specific data of FIG. 5, in which peaks No. 1 to 7 represent nine-isocyanate prepolymer of biuret structure, seven-isocyanate prepolymer of biuret structure, pentaisocyanate prepolymer of biuret structure, tetra-isocyanate prepolymer of biuret structure, diisocyanate prepolymer of biuret structure, triisocyanate prepolymer of biuret structure, and diisocyanate, respectively.

The above description is only a preferred embodiment of the present invention, and the scope of the present invention is not limited thereto, and any simple modifications or equivalent substitutions of the technical solutions that can be obviously obtained by those skilled in the art within the technical scope of the present invention are within the scope of the present invention.