Polyisocyanates and processes for their preparation

Abstract

The present invention relates to a polyisocyanate containing urethane groups prepared by reacting a system comprising an organic polyhydroxy compound and an excess of toluene diisocyanate, a method for preparing the same, a product containing the polyisocyanate, and the use thereof as a polyisocyanate component in a polyurethane paint. The polyisocyanate has the following characteristics: a. the ratio of the integrated area of the component peak with a weight average molecular weight of 800 ± 50 to the integrated area of the shoulder peak with a weight average molecular weight of 950 ± 50 is 2 - 14; and b. the viscosity is less than or equal to 2500 mPa·s. The polyisocyanate of the present invention has good storage stability.

Description

Technical Field

[0001] The present invention relates to a polyisocyanate containing urethane groups prepared by reacting a system comprising an organic polyhydroxy compound and an excess of toluene diisocyanate, a method for preparing the same, a product containing the same, and its use as a polyisocyanate component in polyurethane paints. Background Art

[0002] Polyisocyanates having urethane groups from organic polyhydroxy compounds, especially low molecular weight organic polyhydroxy compounds and toluene diisocyanate (TDI), have long been known, such as the polyisocyanates described in DE 870 400, DE953012 and DE 1 090 196. Such polyisocyanates are very important in the fields of polyurethane paints (also known as polyurethane coatings) and polyurethane adhesives, especially in wood painting and in the field of adhesives. DE-PS1090 186 and US-PS 3,183,112 describe the preparation of commercially common polyisocyanate products, such as Desmodur L75 EA, by reacting a polyhydroxy compound with 5 to 10 times the molar amount of toluene diisocyanate, then separating off the excess starting diisocyanate in a thin-film evaporator, and subsequently adding the corresponding solvent. CN1793194A also discloses a technique for separating free isocyanate monomers in a polyurethane curing agent.

[0003] In the actual use of the above polyisocyanates, in some products, after being used or stored for a period of time, especially at a lower storage temperature, agglomerates or even solid precipitates sometimes appear in the product solution. Although the above products containing agglomerates or even solid precipitates will become clear solutions again after being heated and stirred for a period of time without affecting the quality and effect of the products, the additional heating treatment operation affects the usability of the products. Therefore, avoiding the appearance of agglomerates or even solid precipitates during storage is a problem faced by polyisocyanate manufacturers.

[0004] CN109824865A discloses a method for preparing a storage-stable polyurethane curing agent. High-molecular-weight polymer components are considered to be the reason for the poor storage stability. Therefore, after the reaction of excessive toluene diisocyanate with a hydroxy compound, an organic acid with a pKa value of 1-15 is added to the reaction mixture, and then the excessive toluene diisocyanate monomer is separated at a high temperature through a thin-film evaporator. The added organic acid is considered to promote the reaction between the free hydroxy groups and the highly reactive isocyanate groups in the reaction mixture during the thin-film evaporation, reduce the residual hydroxy content in the prepared curing agent, and thus improve the storage stability of the curing agent. However, the addition of an organic acid (such as dibutyl phosphate) not only increases the complexity of the process and the raw material cost, but also limits the application fields of the curing agent. For example, such curing agents cannot be applied to food contact.

[0005] CN1793194A improves the storage stability of the curing agent by additionally adding high-molecular-weight polyethylene glycol 200 based on a low-molecular-weight organic polyhydroxy compound. It is generally understood in the industry that high-molecular-weight polyethylene glycol 200 will react with toluene diisocyanate to form components with a higher molecular weight, and may cause an increase in viscosity and a decrease in the content of isocyanate groups, which is not conducive to industrial applications. Moreover, the increase in the types of raw material components will also increase the complexity of the process and the raw material cost.

[0006] Therefore, it is still an urgent need in the polyurethane industry to develop polyisocyanates with low viscosity and good storage stability without increasing the raw material components and the process complexity. Summary of the Invention

[0007] The term "curing" refers to the process of a paint or adhesive changing from a liquid state to a solid state.

[0008] The term "adhesive" refers to a mixture containing curable and sticky chemical components, and is also used as a synonym for binder and / or sealant and / or adherent.

[0009] The term "polyurethane" refers to polyurethane urea and / or polyurethane polyurea and / or polyurea and / or polythiourethane.

[0010] The term "toluene diisocyanate" refers to the general term for 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, and the mixture of 2,4-toluene diisocyanate and 2,6-toluene diisocyanate.

[0011] The polyisocyanate of the present invention is actually in the form of a solution, and the solvent can be those known in the industry.

[0012] The object of the present invention is to provide a polyisocyanate containing urethane groups, a process for its preparation, a product containing the same, and its use as a polyisocyanate component in polyurethane paints, which is prepared by reacting a system containing an organic polyhydroxy compound and an excess of toluene diisocyanate.

[0013] A polyisocyanate containing urethane groups, which is prepared by reacting a system containing an organic polyhydroxy compound and an excess of toluene diisocyanate according to the present invention, wherein the organic polyhydroxy compound contains trimethylolpropane and optionally a di- to tetravalent alcohol having a molecular weight of 62 - 146 g / mol, and the polyisocyanate has the following characteristics:

[0014] a. The ratio of the integrated area of the component peak with a weight average molecular weight of 800 ± 50 g / mol to the integrated area of the shoulder peak with a weight average molecular weight of 950 ± 50 g / mol is 2 - 14; and

[0015] b. The viscosity is less than or equal to 2500 mPa·s.

[0016] According to one aspect of the present invention, there is provided a process for preparing a polyisocyanate, comprising:

[0017] i. Reacting a system containing an organic polyhydroxy compound and an excess of toluene diisocyanate to obtain a prepolymer reaction mixture, the reaction temperature being 85°C - 120°C and the reaction time being 1 hour - 24 hours;

[0018] ii. Separating and removing the unreacted toluene diisocyanate from the prepolymer reaction mixture obtained in step i; and

[0019] iii. Adding an organic solvent for dilution to obtain the polyisocyanate.

[0020] According to one aspect of the present invention, there is provided a product containing a polyisocyanate.

[0021] According to one aspect of the present invention, there is provided the use of the polyisocyanate as a polyisocyanate component in polyurethane paints.

[0022] According to one aspect of the present invention, there is provided the use of the polyisocyanate as a polyisocyanate component in polyurethane adhesives.

[0023] The polyisocyanate containing urethane groups, which is prepared by reacting a system containing an organic polyhydroxy compound and an excess of toluene diisocyanate according to the present invention, not only has a high content of isocyanate groups, a low content of monomeric toluene diisocyanate and a low viscosity, but also has the advantage of good storage stability, that is, no agglomerates are likely to appear during long-term storage.

[0024] The polyurethane coatings containing the polyisocyanate of the present invention and, in particular, the two-component polyurethane coatings containing the polyisocyanate of the present invention as a crosslinking agent form paint films with high abrasion resistance. The paint films have excellent adhesion on various different substrates, are hard but still elastic, and are not prone to discoloration. The texture of light-colored wood species painted with them can also be significantly effective. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The present invention will be described and explained in more detail below with reference to the accompanying drawings, in which:

[0026] Figure 1 is the gel permeation chromatography obtained from the polyisocyanate 5 of Example 5. Figure 1 It also shows the calculation of the ratio of the integral area of the component peak with a weight-average molecular weight of 800 ± 50 g / mol to the integral area of the shoulder peak with a weight-average molecular weight of 950 ± 50 g / mol of the polyisocyanate 5. DETAILED DESCRIPTION OF THE INVENTION

[0027] The present invention provides a polyisocyanate containing urethane groups prepared by reacting a system of an organic polyhydroxy compound and an excess of toluene diisocyanate. The organic polyhydroxy compound contains trimethylolpropane and optionally a di- to tetravalent alcohol with a molecular weight of 62 - 146 g / mol. The polyisocyanate has the following characteristics: a. The ratio of the integral area of the component peak with a weight-average molecular weight of 800 ± 50 g / mol to the integral area of the shoulder peak with a weight-average molecular weight of 950 ± 50 g / mol is 2 - 14; and b. The viscosity is less than or equal to 2500 mPa·s. The present invention also provides a method for preparing the polyisocyanate, products containing the same, and its use as a polyisocyanate component in polyurethane coatings and adhesives.

[0028] Polyisocyanate

[0029] The ratio of the integral area of the component peak with a weight-average molecular weight of 800 ± 50 g / mol to the integral area of the shoulder peak with a weight-average molecular weight of 950 ± 50 g / mol is preferably 3 - 13, more preferably 4 - 12, and most preferably 6 - 12.

[0030] The components of the polyisocyanate of the present invention and its weight average molecular weight are determined according to DIN 55672-1:2016-03 by using a gel chromatograph of the HLC-8320 EcoSEC type from TOSOH, a 4-fold column set of high-performance general chromatographic columns (TSKgel G2000HXL, TSKgel G2500HXL, TSKgel G3000HXL, and TSKgel G4000HXL, with the column packing being a styrene-divinylbenzene copolymer) and a differential refractive index detector. The eluent is tetrahydrofuran, the flow rate is 1.0 ml / min, the pressure is 6.4 MPa, and the column temperature is 40 °C.

[0031] The viscosity of the polyisocyanate is preferably not more than 2000 mPa·s, and most preferably not more than 1800 mPa·s. The viscosity is measured at 23 °C using a cone / plate measuring instrument according to DIN EN ISO 5:1994-10.

[0032] Preferably, the polyisocyanate has a viscosity of 2000 mPa·s or less, and the ratio of the integrated area of the component peak with a weight average molecular weight of 800 ± 50 g / mol to the integrated area of the shoulder peak with a weight average molecular weight of 950 ± 50 g / mol is 4 - 12.

[0033] Most preferably, the polyisocyanate has a viscosity of 1800 mPa·s or less, and the ratio of the integrated area of the component peak with a weight average molecular weight of 800 ± 50 g / mol to the integrated area of the shoulder peak with a weight average molecular weight of 950 ± 50 g / mol is 6 - 12.

[0034] The polyisocyanate preferably further has one or more of the following characteristics:

[0035] c. The solid content is greater than or equal to 50% by weight and less than or equal to 90% by weight;

[0036] d. The amount of unreacted excess toluene diisocyanate is less than or equal to 0.5% by weight; and

[0037] e. The isocyanate group content is 13% by weight - 15% by weight;

[0038] The above % by weight are based on the total weight of the polyisocyanate calculated as 100% by weight.

[0039] The solid content of the polyisocyanate is preferably 60% by weight - 80% by weight, more preferably 70% by weight - 77% by weight, and most preferably 73% by weight - 77% by weight, based on the total weight of the polyisocyanate calculated as 100% by weight.

[0040] The solids content (also called non-volatile content) was determined in accordance with DIN EN ISO 3251 using a drying temperature and time of 2 hours at 120° C. and a test dish diameter of 75 mm and a weighed-in amount of 2.00 g + / - 0.02.

[0041] The amount of unreacted excess toluene diisocyanate of the polyisocyanate is preferably equal to or less than 0.4% by weight, based on 100% by weight of the total weight of the polyisocyanate.

[0042] The content of unreacted excess toluene diisocyanate is determined by gas chromatography in accordance with DIN EN ISO 10283:2007-11 using an internal standard.

[0043] The polyisocyanate of the present invention contains a very low content of unreacted excess toluene diisocyanate, which improves occupational hygiene, especially occupational hygiene in manual operations, and expands the application field of the polyisocyanate of the present invention.

[0044] The GPC analysis results show that there are multiple polyisocyanate components in the polyisocyanate of the present invention, and the specific components depend on the organic polyol and toluene diisocyanate (TDI) content used. Among them, the main component is generated by the reaction of a single organic polyol in the system with TDI molecules corresponding to its functionality number; in addition to the main component, it also contains a high molecular weight component generated by the continuous reaction of two or more organic polyols in the system with TDI and the main component. We were surprised to find that a shoulder peak sometimes appears on the high molecular weight side of the GPC peak of the component generated by the reaction of a single organic polyol with TDI molecules corresponding to its functionality number, and surprisingly found that the shoulder peak helps to increase the isocyanate group content of the polyisocyanate and improve the storage stability of the polyisocyanate without significantly increasing the viscosity of the polyisocyanate. In particular, for the polyisocyanate produced by the reaction of trimethylolpropane and TDI, the ratio of the integrated area of ​​the component peak with a weight average molecular weight (Mw) of 800±50 g / mol to the integrated area of ​​the shoulder peak with a weight average molecular weight of 950±50 g / mol in GPC will affect the storage stability of the polyisocyanate product.

[0045] Toluene diisocyanate

[0046] The toluene diisocyanate is preferably a mixture of 2,4-toluene diisocyanate and 2,6-toluene diisocyanate, wherein the weight ratio of 2,4-toluene diisocyanate to 2,6-toluene diisocyanate is 60:40-95:5, preferably 65:35-90:10, and most preferably 70:30-85:15.

[0047] The toluene diisocyanate is preferably prepared by gas phase phosgenation.

[0048] 2-Chloro-6-isocyanato-methylcyclohexadiene (CIMCH) can exist in the form of three double bond isomers, which can be present in TDI in different proportions. They are formed, for example, in the preparation of TDI from 1-amino-2-methyl-cyclohexenone contained in the TDA used, which in turn can be generated by partial hydrogenation of the TDA and replacement of the amino functional group with water during the preparation of TDA from dinitrotoluene (DNT). The keto functional group can also be introduced proportionally by oxidative attack during the nitration of toluene to prepare DNT, where nitrocresol is first formed, which can then form the above-mentioned 1-amino-methyl-2-cyclohexenone during subsequent hydrogenation.

[0049] The tolylene diisocyanate has a 2-chloro-6-isocyanato-methylcyclohexadiene (CIMCH) content of < 5 wt. ppm, preferably < 3 wt. ppm. Such a TDI grade can be obtained, for example, by targeted distillation of 2-chloro-6-isocyanato-methylcyclohexadiene from a pre-concentrated TDI crude solution with the aid of a dividing wall distillation column as described in EP 1 413 571 B1. However, particularly preferred is tolylene diisocyanate prepared by gas phase phosgenation of TDA and having a 2-chloro-6-isocyanato-methylcyclohexadiene content below the detection limit of 1 ppm. Such a grade of tolylene diisocyanate is available, for example, from the Caojing production site of Covestro Deutschland AG in China.

[0050] Two independent analytical methods have been used for the unambiguous characterization of the component 2-chloro-6-isocyanato-methylcyclohexadiene. With the aid of gas chromatography techniques, different grades of tolylene diisocyanate with a 2,4 content of approximately 80 wt. % were tested for differences in their secondary component spectra. By subsequent gas chromatography-mass spectrometry, a molecular weight of 169 g / mol was attributed to three hitherto unknown compounds (CIMCH, including two isomers). Further structural information can be obtained from fragmentation in a manner known to those skilled in the art. With the aid of sophisticated nuclear magnetic resonance spectroscopy experiments ('H-NMR, 'H-COSY, 'H-, 'HTOCSY and 'H-, 'C-HMBC), the following structures can be attributed to the three components with m / z 169.

[0051]

[0052] The detection limit of CIMCH isomers can be determined to be 1 wt ppm by gas chromatography-spectroscopy by targeted method expansion using a Macherey-Nagel Optima 5 HT column (60 m long, 0.25 mm inner diameter, 0.25 µm film thickness) in a Hewlett Packard HP Series 6890 gas chromatograph.

[0053] Isocyanate compound different from the toluene diisocyanate

[0054] The system may further comprise an isocyanate compound different from the toluene diisocyanate, and the weight ratio of the toluene diisocyanate to the isocyanate compound different from the toluene diisocyanate is preferably not less than 60:40, more preferably not less than 90:10, and most preferably not less than 95:5.

[0055] The isocyanate compound different from the toluene diisocyanate in the system may be any other compound having an isocyanate group, such as a monoisocyanate having an aliphatic, cycloaliphatic, araliphatic or aromatic bonded isocyanate group, a diisocyanate having an aliphatic, cycloaliphatic, araliphatic and / or aromatic bonded isocyanate group, a triisocyanate and / or a higher functionality isocyanate, and a modified isocyanate derived from the above diisocyanates and triisocyanates and prepared by an oligomerization reaction, such as a trimerization reaction.

[0056] The monoisocyanate having an aliphatic, cycloaliphatic, araliphatic or aromatic bonded isocyanate group is preferably one or more of the following: stearyl isocyanate and naphthyl isocyanate.

[0057] The diisocyanates having aliphatic, cycloaliphatic, araliphatic and / or aromatic bonded isocyanate groups are preferably one or more of the following: 1,4-diisocyanatobutane, 1,5-diisocyanatopentane (PDI), 1,6-diisocyanatohexane (HDI), 2-methyl-1,5-diisocyanatopentane, 1,5-diisocyanato-2,2-dimethylpentane, 2,2,4- or 2,4,4-trimethyl-1,6-diisocyanatohexane, 1,10-diisocyanatodecane, 1,3- and 1,4-diisocyanatocyclohexane, 1,3- and 1,4-bis(isocyanatomethyl)cyclohexane, 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane (isophorone diisocyanate, IPDI), 4,4'-diisocyanatodicyclohexylmethane, 1-isocyanato-1-methyl-4(3)-isocyanatomethylcyclohexane (IMCI), bis(isocyanatomethyl)norbornane, 2,4'- and 4,4'-diisocyanatodiphenylmethane and higher homologues, 1,5-diisocyanatonaphthalene and dipropylene glycol diisocyanate.

[0058] The triisocyanates and / or higher functionality isocyanates are preferably one or more of the following: 4-isocyanatomethyloctane-1,8-diisocyanate (nonane triisocyanate) and undecane-1,6,11-triisocyanate.

[0059] The isocyanate compounds different from the toluene diisocyanate in the system are most preferably one or more of the following: 1,5-diisocyanatopentane (PDI), 1,6-diisocyanatohexane (HDI) and modified isocyanates derived from the above diisocyanates and prepared by oligomerization reactions such as trimerization reactions.

[0060] When the system contains both toluene diisocyanate and isocyanate compounds different from the toluene diisocyanate, the total amount of any unreacted monomeric isocyanate remaining (i.e., the sum of the amount of unreacted excess toluene diisocyanate and the amount of unreacted excess isocyanate compounds different from the toluene diisocyanate) is preferably less than or equal to 0.5% by weight, more preferably less than or equal to 0.4% by weight, based on 100% by weight of the total weight of the polyisocyanate.

[0061] The content of unreacted excess monomeric toluene diisocyanate and the content of unreacted excess isocyanate compounds different from the toluene diisocyanate are both determined by gas chromatography using an internal standard in accordance with DIN EN ISO 10283:2007-11.

[0062] Organic polyhydroxy compound

[0063] The total weight of the trimethylolpropane and the optional di- to tetravalent alcohols having a molecular weight of 62 - 146 g / mol is preferably 99.7 wt% - 100 wt%, most preferably 100 wt%, based on 100 wt% of the total weight of the organic polyhydroxy compound.

[0064] The weight ratio of the trimethylolpropane to the di- to tetravalent alcohols having a molecular weight of 62 - 146 g / mol is preferably 1:4 - 4:1, more preferably 3:7 - 3:1, and most preferably 1:1 - 7:3.

[0065] The di- to tetravalent alcohols having a molecular weight of 62 - 146 g / mol are preferably one or more of the following: ethylene glycol, diethylene glycol, 1,2 - propanediol, 1,3 - propanediol, 1,2 - butanediol, 1,3 - butanediol, 1,4 - butanediol, 1,5 - pentanediol, neopentyl glycol, 1,6 - hexanediol, 2 - ethylhexanediol, glycerol, and pentaerythritol, and most preferably diethylene glycol.

[0066] The di- to tetravalent alcohols having a molecular weight of 62 - 146 g / mol are most preferably diethylene glycol, and the weight ratio of the trimethylolpropane to the diethylene glycol is preferably 1:4 - 4:1, more preferably 3:7 - 3:1, and most preferably 1:1 - 7:3.

[0067] Method

[0068] A process for preparing the polyisocyanate of the present invention, comprising:

[0069] i. Reacting a system comprising an organic polyhydroxy compound and an excess of tolylene diisocyanate to obtain a prepolymer reaction mixture at a reaction temperature of 85°C - 120°C for a reaction time of 1 hour - 24 hours;

[0070] ii. Separating and removing the unreacted tolylene diisocyanate from the prepolymer reaction mixture obtained in step i; and

[0071] iii. Adding an organic solvent for dilution to obtain the polyisocyanate;

[0072] wherein the organic polyhydroxy compound comprises trimethylolpropane and an optional di- to tetravalent alcohol having a molecular weight of 62 - 146 g / mol; and the polyisocyanate has the following characteristics:

[0073] a. The ratio of the integral area of the component peak having a weight average molecular weight of 800 ± 50 g / mol to the integral area of the shoulder peak having a weight average molecular weight of 950 ± 50 g / mol is 2 - 14; and

[0074] b. The viscosity is less than or equal to 2500 mPa·s.

[0075] The reaction temperature in step i is preferably 85°C-110°C, most preferably 90°C-98°C.

[0076] The reaction time of step i is preferably 1.2 hours to 7 hours, and most preferably 1.2 hours to 4 hours. The reaction time of step i of the present invention includes the mixing time of the organic polyhydroxy compound and toluene diisocyanate and the reaction time of the system at the reaction temperature.

[0077] The equivalent ratio of isocyanate groups to hydroxyl groups of the system is preferably 3:1-20:1, more preferably 3.5:1-10:1, and most preferably 3.8:1-8:1.

[0078] The separation in step ii is preferably carried out by distillation.

[0079] Preferably, the step ii is to distill the prepolymer reaction mixture through a thin film evaporator at 100°C-180°C, preferably 120°C-170°C under vacuum to remove excess unreacted toluene diisocyanate to obtain a semi-hard to hard crude product.

[0080] The step iii specifically comprises adding an organic solvent to the semi-hard to hard crude product obtained in step ii to dilute and obtain the polyisocyanate.

[0081] The organic solvent may be those known in the industry, such as toluene, xylene, cyclohexane, butyl acetate, ethyl acetate, ethyl glycol acetate, amyl acetate, hexyl acetate, methoxypropyl acetate, tetrahydrofuran, dioxane, acetone, N-methylpyrrolidone, methyl ethyl ketone, white spirit, which may be obtained, for example, under the trade name Solvent Naphtha ® , Solvesso ® 、Shellsol ® , Isopar ® 、Nappar ® and Diasol ® Commercially available relatively highly substituted aromatic compounds, benzene homologues, tetralin, decalin and alkanes with more than 6 carbon atoms, conventional plasticizers such as phthalates, sulfonates and phosphates and mixtures of such diluents and solvents. Other suitable solvents are polyisocyanates based on aliphatic diisocyanates as described, for example, in DE-A 4 428 107, which make the polyisocyanates free of or less containing volatile solvents and diluents.

[0082] The amount of the organic solvent is preferably added in an amount required to set the solid content of the polyisocyanate to 50% to 90% by weight, more preferably 60% to 80% by weight, still more preferably 70% to 77% by weight, and most preferably 73% to 77% by weight.

[0083] The method can be carried out intermittently or continuously.

[0084] Product

[0085] The product is preferably selected from polyurethane paints and polyurethane adhesives.

[0086] The polyurethane paint can be a one-component polyurethane paint or a two-component polyurethane paint.

[0087] The two-component polyurethane paint can contain the polyisocyanate of the present invention and one or more of the following known in polyurethane paint technology: polyester polyol, polyether polyol, polyacrylate polyol, and optionally low molecular weight polyol.

[0088] The two-component polyurethane paint can also contain the polyisocyanate of the present invention and one or more of the following: blocked polyketimine and polyamine of oxazolidine, wherein the equivalent ratio of the isocyanate group to the isocyanate-reactive group is 0.8:1 - 3.0:1, preferably 0.9:1 - 1.1:1.

[0089] The two-component polyurethane paint can further contain a catalyst. The catalyst is used to accelerate the curing of the polyurethane paint.

[0090] The catalyst can be those known in the art, such as amines, such as triethylamine, pyridine, methylpyridine, benzyldimethylamine, N,N'-dimethylpiperazine, or metal salts, such as iron(III) chloride, zinc chloride, zinc 2-ethylhexanoate, tin(II) 2-ethylhexanoate, dibutyltin(IV) dilaurate, or molybdenum glycolate.

[0091] The one-component polyurethane paint or two-component polyurethane paint containing the polyisocyanate of the present invention can form a hard and still elastic paint film with excellent adhesion on various different substrates. The paint film also has the advantages of high wear resistance and non-discoloration, and is suitable for the woodware field, especially for the woodware field using light-colored wood. Examples

[0092] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this invention belongs. When the definition of a term in this specification conflicts with the meaning commonly understood by those skilled in the art to which this invention belongs, the definition set forth herein shall prevail.

[0093] Unless otherwise indicated, all numerical values of ingredients amounts, reaction conditions, etc. used in the specification and claims are understood to be modified by the term "about". Accordingly, unless indicated to the contrary, the numerical parameters set forth herein are approximations that can vary depending upon the desired properties sought to be obtained.

[0094] As used herein, "and / or" refers to one or all of the recited elements.

[0095] As used herein, "above" and "below" include the recited numerical value itself, unless otherwise indicated.

[0096] As used herein, "comprising" and "including" encompass both cases where only the recited elements are present and cases where there are also other unrecited elements in addition to the recited elements.

[0097] All analytical measurements of the present invention are carried out at 23 °C, unless otherwise indicated.

[0098] The components of the polyisocyanate of the present invention and its weight-average molecular weight are determined according to DIN 55672-1:2016-03 by using a gel permeation chromatograph of the HLC-8320 EcoSEC type from TOSOH with polystyrene standards, a high-performance universal chromatographic column set of 4 columns (TSKgel G2000HXL, TSKgel G2500HXL, TSKgel G3000HXL and TSKgel G4000HXL, the column packing being a styrene-divinylbenzene copolymer) and a differential refractive index detector. The eluent is tetrahydrofuran, the flow rate is 1.0 ml / min, the pressure is 6.4 MPa, and the column temperature is 40 °C.

[0099] The isocyanate group (NCO) content is determined by titration according to DIN-EN ISO 11909:2007-05. The measured data include the free and potentially free NCO content.

[0100] Storage stability test of the polyisocyanate: The polyisocyanate sample is sealed and stored in a freezer at -5 °C for 10 weeks. The sample is irradiated with a cold light source to observe whether the sample is clear or turbid. If the sample is clear, it is considered to have good storage stability; if the sample is turbid, it is considered to have poor storage stability.

[0101] Raw materials and reagents

[0102] DESMODUR ® T 80: Toluene diisocyanate, containing approximately 80 wt% 2,4-toluene diisocyanate and 20 wt% 2,6-toluene diisocyanate, can be purchased from Covestro Polymer GmbH.

[0103] Trimethylolpropane: Purchased from Nantong Baichuan New Materials Co., Ltd.

[0104] Diethylene glycol: Purchased from Yangzi Petrochemical - BASF Co., Ltd.

[0105] Ethyl acetate: Purchased from Sigma - Aldrich (Shanghai) Trading Co., Ltd.

[0106] 2 - Ethylhexanol: Purchased from Sigma - Aldrich (Shanghai) Trading Co., Ltd.

[0107] Borchi ® Kat 22: A catalyst, available from OMG Borchers GmbH.

[0108] NACURE ® 5076: A terminator, available from King Industries.

[0109] Examples and comparative examples

[0110] Example 1

[0111] 800 g of DESMODUR ® T 80 was pre - added to a 1000 mL reaction flask. The flask was heated to 98 °C by an oil bath, and a premixed polyol mixture composed of 52 g of trimethylolpropane and 28 g of diethylene glycol was continuously metered into the flask within 60 minutes for reaction. The reaction was carried out with stirring at 98 °C for 3 hours to obtain a reaction mixture. Excess monomeric toluene diisocyanate in the reaction mixture was removed by two - stage thin - film distillation (170 °C / 165 °C, p ≤ 0.5 mbar), and then ethyl acetate was added to obtain a polyisocyanate 1 containing urethane groups.

[0112] Example 2

[0113] 800 g of DESMODUR ® T 80 was pre - added to a 1000 mL reaction flask. The flask was heated to 95 °C by an oil bath, and a premixed polyol mixture composed of 52 g of trimethylolpropane and 28 g of diethylene glycol was continuously metered into the flask within 60 minutes for reaction. The reaction was carried out with stirring at 95 °C for 2 hours to obtain a reaction mixture. Excess monomeric toluene diisocyanate in the reaction mixture was removed by two - stage thin - film distillation (170 °C / 165 °C, p ≤ 0.5 mbar), and then ethyl acetate was added to obtain a polyisocyanate 2 containing urethane groups.

[0114] Example 3

[0115] Charge 1800 g of DESMODUR ® T 80 into a 2000 mL double-jacketed glass reaction vessel in advance. Heat the vessel to 85 °C, and continuously meter and add a premixed polyol mixture composed of 166 g of trimethylolpropane and 89 g of diethylene glycol into the vessel within 250 minutes for reaction. During the reaction process, safely remove the reaction heat from the vessel through a thermal circulator with heating and cooling functions. Conduct the reaction in an isothermal manner. Stir the reaction at 85 °C for 2 hours to obtain a reaction mixture. Subsequently, remove the excessive monomer toluene diisocyanate in the reaction mixture through two-stage thin-film distillation (170 °C / 165 °C, p ≤ 0.5 mbar), and then add ethyl acetate to obtain a polyisocyanate 3 containing urethane groups.

[0116] Example 4

[0117] The continuous reaction system consists of 4 cascaded jacketed reactors, each with a volume of 400 L. Charge the 4 cascaded reactors with DESMODUR ® T 80 in advance, and set the reaction temperatures of the four reactors to 90 °C, 95 °C, 95 °C, and 95 °C respectively. Each reactor safely removes the reaction heat released by the reaction through a cooling and heating temperature control system. Conduct the reaction in an isothermal manner. At the start of the reaction, continuously meter and add DESMODUR ® T 80 (room temperature) and an organic polyhydroxy compound (60 °C) with a weight ratio of 8.5:1 into the first reactor of the cascade, and maintain the temperature in this reactor at 90 °C through the jacket. The organic polyhydroxy compound is a mixture of trimethylolpropane and diethylene glycol with a weight ratio of 65:35. Control the total feed flow rate to keep the average residence time in the 4 cascaded reactors at about 1.5 hours. Remove the excessive monomer toluene diisocyanate from the reaction mixture through two-stage thin-film distillation (170 °C / 160 °C, p ≤ 0.5 mbar), and then add ethyl acetate to obtain a polyisocyanate 4 containing urethane groups.

[0118] Example 5

[0119] The continuous reaction system consists of 4 cascaded jacketed reactors, each with a volume of 400 L. Charge the 4 cascaded reactors with DESMODUR ® T 80 in advance, and set the reaction temperatures of the four reactors to 90 °C, 95 °C, 95 °C, and 95 °C respectively. Each reactor safely removes the reaction heat released by the reaction through a cooling and heating temperature control system. Conduct the reaction in an isothermal manner. At the start of the reaction, continuously meter and add DESMODUR ®T 80 (room temperature) and the organic polyhydroxy compound (60 °C) are fed into the first reactor of the cascade, and the temperature inside the reactor is maintained at 90 °C through the jacket. The organic polyhydroxy compound is a mixture of trimethylolpropane and diethylene glycol with a weight ratio of 65:35. The total feed flow rate is controlled to maintain an average residence time of about 1.2 hours in the 4 cascade reactors. Excess monomeric toluene diisocyanate is removed from the reaction mixture by two-stage thin-film distillation (170 °C / 160 °C, p ≤ 0.5 mbar), and then ethyl acetate is added to obtain the polyisocyanate 5 containing urethane groups.

[0120] Example 6

[0121] The continuous reaction system consists of 4 cascade jacketed reactors, each with a volume of 400 L. The 4 cascade reactors are pre-filled with DESMODUR ® T 80, and the reaction temperatures of the four reactors are set at 85 °C, 90 °C, 90 °C, and 90 °C respectively. Each reactor safely removes the heat of reaction released by the reaction with the help of a cooling and heating temperature control system. The reaction is carried out isothermally. When the reaction is started, DESMODUR ® T 80 (room temperature) and the organic polyhydroxy compound (60 °C) are fed into the first reactor of the cascade, and the temperature inside the reactor is maintained at 85 °C through the jacket. The organic polyhydroxy compound is a mixture of trimethylolpropane and diethylene glycol with a weight ratio of 65:35. The total feed flow rate is controlled to maintain an average residence time of about 1.5 hours in the 4 cascade reactors. Excess monomeric toluene diisocyanate is removed from the reaction solution by two-stage thin-film distillation (170 °C / 160 °C, p ≤ 0.5 mbar), and then ethyl acetate is added to obtain the polyisocyanate 6 containing urethane groups.

[0122] Example 7

[0123] 1700 g of DESMODUR ® T 80 is pre-added to a 2000 mL double-jacketed glass reaction vessel. The vessel is heated to 85 °C, and within 45 minutes, a premixed polyol mixture consisting of 110 g of trimethylolpropane and 60 g of diethylene glycol is continuously metered into the vessel for reaction. During the reaction, the heat of reaction is safely removed from the vessel by a heat circulator with heating and cooling functions. The reaction is carried out isothermally. The reaction is carried out with stirring at 85 °C for 2 hours to obtain a reaction mixture. Subsequently, excess monomeric toluene diisocyanate in the reaction mixture is removed by two-stage thin-film distillation (135 °C / 130 °C, p ≤ 0.05 mbar), and then ethyl acetate is added to obtain the polyisocyanate 7 containing urethane groups.

[0124] Comparative example 1

[0125] Pre-add 1700 g of DESMODUR ® T 80 into a 2000 mL double-jacketed glass reaction vessel in advance. Heat this vessel to 80 °C, and within 45 minutes, continuously meteringly add a premixed polyol mixture composed of 110 g of trimethylolpropane and 60 g of diethylene glycol into this vessel for reaction. During the reaction process, safely remove the reaction heat from the vessel through a thermal circulator with heating and cooling functions. Conduct the reaction in an isothermal manner. Conduct the reaction with stirring at 80 °C for 1 hour to obtain a reaction mixture. Subsequently, remove the excessive monomer toluene diisocyanate in the reaction mixture through two-stage thin-film distillation (135 °C / 130 °C, p ≤ 0.05 mbar), and then add ethyl acetate to obtain Comparative Polyisocyanate 1 containing urethane groups.

[0126] Comparative example 2

[0127] Pre-add 1411 g of DESMODUR ® T 80 into a 2000 mL double-jacketed glass reaction vessel in advance. Heat this vessel to 85 °C, and within 60 minutes, continuously meteringly add a premixed polyol mixture composed of 91 g of trimethylolpropane and 49 g of diethylene glycol into this vessel for reaction. During the reaction process, safely remove the reaction heat from the vessel through a thermal circulator with heating and cooling functions. Conduct the reaction in an isothermal manner. Conduct the reaction with stirring at 85 °C for 1 hour to obtain a reaction mixture. Heat the obtained reaction mixture to approximately 98 °C. Add 0.26 g of Borchi ® Kat 22 solution (10 wt% in 2-ethylhexanol), and conduct the reaction with stirring at 98 °C for 1 hour. Add 0.17 g of NACURE ® 5076, and stir for 1 hour. Subsequently, remove the excessive monomer toluene diisocyanate through two-stage thin-film distillation (127 °C / 140 °C, p ≤ 0.05 mbar), and then add ethyl acetate to obtain Comparative Polyisocyanate 2 containing urethane groups.

[0128] Test results of the specifications and storage stability of polyisocyanate

[0129] Table 1 lists the specifications and storage stability test results of Polyisocyanates 1 - 7 and Comparative Isocyanates 1 - 2.

[0130] Table 1 Polyisocyanate Characteristics and Storage Stability Test

[0131]

[0132] Note: The ratio of the integral areas refers to the ratio of the integral area of the component peak with a weight-average molecular weight of 800 ± 50 g / mol and the integral area of the shoulder peak with a weight-average molecular weight of 950 ± 50 g / mol in the GPC measured by a gel permeation chromatograph.

[0133] As can be seen from Examples 1-7, the polyisocyanate of the present invention not only has a high content of isocyanate groups, a low content of monomeric toluene diisocyanate and a low viscosity, but also has good storage stability. From Comparative Example 1, it can be seen that when the ratio of the integral area of the component peak with a weight-average molecular weight of 800 ± 50 g / mol and the integral area of the shoulder peak with a weight-average molecular weight of 950 ± 50 g / mol in the gel permeation chromatogram of the comparative polyisocyanate is greater than 14, the storage stability of the comparative polyisocyanate is poor. From Comparative Example 2, it can be seen that when the ratio of the integral area of the component peak with a weight-average molecular weight of 800 ± 50 g / mol and the integral area of the shoulder peak with a weight-average molecular weight of 950 ± 50 g / mol in the GPC of the comparative polyisocyanate is less than 2 by adding Borchi ® Kat 22 solution, although the storage stability of the comparative polyisocyanate is improved, the viscosity of the comparative polyisocyanate is greater than 2500 mPa·s, which is not conducive to practical industrial applications.

[0134] Comparing Examples 2-6 with Examples 1 and 7, when the viscosity of the polyisocyanate is below 2000 mPa·s and the ratio of the integral area of the component peak with a weight-average molecular weight of 800 ± 50 g / mol and the integral area of the shoulder peak with a weight-average molecular weight of 950 ± 50 g / mol is 4-12, the storage stability of the polyisocyanate is good and it better meets the low-viscosity requirements desired in the industry. As shown in Examples 3-6, when the viscosity of the polyisocyanate is below 1800 mPa·s and the ratio of the integral area of the component peak with a weight-average molecular weight of 800 ± 50 g / mol and the integral area of the shoulder peak with a weight-average molecular weight of 950 ± 50 g / mol is 6-12, the storage stability of the polyisocyanate is good and it is more popular in the industry.

[0135] Those skilled in the art will readily appreciate that the present invention is not limited to the foregoing specific details, and that the present invention may be embodied in other specific forms without departing from the spirit or main characteristics thereof. Therefore, in any aspect, the embodiments should be regarded as illustrative rather than restrictive, and the scope of the present invention should be indicated by the claims rather than the foregoing description; and thus any change, as long as it falls within the meaning and scope of the equivalents of the claims, should be regarded as belonging to the present invention.

Claims

1. A polyisocyanate containing urethane groups, prepared by reacting a system comprising an organic polyhydroxy compound and an excess of toluene diisocyanate, wherein the organic polyhydroxy compound comprises trimethylolpropane and optionally a di- to tetravalent alcohol having a molecular weight of 62 - 146 g / mol, and the polyisocyanate has the following characteristics: a. The ratio of the integrated area of the component peak with a weight average molecular weight of 800 ± 50 g / mol to the integrated area of the shoulder peak with a weight average molecular weight of 950 ± 50 g / mol is 2 - 13; and b. The viscosity is less than or equal to 2500 mPa·s, wherein the components of the polyisocyanate and their weight average molecular weights are determined according to DIN 55672 - 1:2016 - 03 using a gel permeation chromatograph of the TOSOH HLC - 8320 EcoSEC type with polystyrene standards, a 4 - fold column set of high - performance general chromatography columns, and a differential refractive index detector. The 4 - fold column set of chromatography columns are TSKgel G2000HXL, TSKgel G2500HXL, TSKgel G3000HXL, and TSKgel G4000HXL respectively. The column packing is a styrene - divinylbenzene copolymer, the eluent is THF, the flow rate is 1.0 ml / min, the pressure is 6.4 MPa, and the column temperature is 40 °C. And wherein the viscosity of the polyisocyanate components is measured at 23 °C using a cone / plate measuring instrument according to DIN EN ISO 5:1994 - 10.

2. The polyisocyanate according to claim 1, characterized in that the ratio of the integrated area of the component peak with a weight average molecular weight of 800 ± 50 g / mol to the integrated area of the shoulder peak with a weight average molecular weight of 950 ± 50 g / mol is 3 - 13.

3. The polyisocyanate according to claim 1, characterized in that the ratio of the integrated area of the component peak with a weight average molecular weight of 800 ± 50 g / mol to the integrated area of the shoulder peak with a weight average molecular weight of 950 ± 50 g / mol is 4 - 12.

4. The polyisocyanate according to claim 1, characterized in that the ratio of the integrated area of the component peak with a weight average molecular weight of 800 ± 50 g / mol to the integrated area of the shoulder peak with a weight average molecular weight of 950 ± 50 g / mol is 6 - 12.

5. The polyisocyanate according to claim 1 or 2, characterized in that the viscosity of the polyisocyanate is not greater than 2000 mPa·s.

6. The polyisocyanate according to claim 1 or 2, characterized in that the viscosity of the polyisocyanate is not greater than 1800 mPa·s.

7. The polyisocyanate according to claim 1, characterized in that the polyisocyanate further has one or more of the following characteristics: c. The solid content is greater than or equal to 50 wt% and less than or equal to 90 wt%; d. The amount of unreacted excess toluene diisocyanate is less than or equal to 0.5 wt%; and e. The isocyanate group content is 13 wt% - 15 wt%; The above wt% are all based on 100 wt% of the total weight of the polyisocyanate.

8. The polyisocyanate according to claim 1, characterized in that the sum of the weights of the trimethylolpropane and the optional di- to tetravalent alcohol having a molecular weight of 62 - 146 g / mol is 99.7 wt% - 100 wt%, based on 100 wt% of the total weight of the organic polyhydroxyl compound.

9. The polyisocyanate according to claim 1, characterized in that the weight ratio of the trimethylolpropane to the di- to tetravalent alcohol having a molecular weight of 62 - 146 g / mol is 1:4 - 4:

1.

10. The polyisocyanate according to claim 1, characterized in that the weight ratio of the trimethylolpropane to the di- to tetravalent alcohol having a molecular weight of 62 - 146 g / mol is 3:7 - 3:

1.

11. The polyisocyanate according to claim 1, characterized in that the weight ratio of the trimethylolpropane to the di- to tetravalent alcohol having a molecular weight of 62 - 146 g / mol is 1:1 - 7:

3.

12. The polyisocyanate according to claim 1, characterized in that the di- to tetravalent alcohol having a molecular weight of 62 - 146 g / mol is one or more of the following: ethylene glycol, diethylene glycol, 1,2 - propanediol, 1,3 - propanediol, 1,2 - butanediol, 1,3 - butanediol, 1,4 - butanediol, 1,5 - pentanediol, neopentyl glycol, 1,6 - hexanediol, 2 - ethylhexanediol, glycerol, and pentaerythritol.

13. The polyisocyanate according to claim 1, characterized in that the di- to tetravalent alcohol having a molecular weight of 62 - 146 g / mol is diethylene glycol, and the weight ratio of the trimethylolpropane to the diethylene glycol is 1:4 - 4:

1.

14. The polyisocyanate according to claim 1, characterized in that the system further comprises an isocyanate compound different from the toluene diisocyanate, and the weight ratio of the toluene diisocyanate to the isocyanate compound different from the toluene diisocyanate is not less than 60:

40.

15. The polyisocyanate according to claim 14, characterized in that the weight ratio of the toluene diisocyanate to the isocyanate compound different from the toluene diisocyanate is not less than 90:

10.

16. The polyisocyanate according to claim 14, characterized in that the weight ratio of the toluene diisocyanate to the isocyanate compound different from the toluene diisocyanate is not less than 95:

5.

17. The polyisocyanate according to claim 1, characterized in that the toluene diisocyanate is a mixture of 2,4 - toluene diisocyanate and 2,6 - toluene diisocyanate in a weight ratio of 60:40 - 95:

5.

18. The polyisocyanate according to claim 1, characterized in that the toluene diisocyanate is a mixture of 2,4 - toluene diisocyanate and 2,6 - toluene diisocyanate in a weight ratio of 65:35 - 90:

10.

19. The polyisocyanate according to claim 1, characterized in that The toluene diisocyanate is a mixture of 2,4-toluene diisocyanate and 2,6-toluene diisocyanate with a weight ratio of 70:30 - 85:

15.

20. A method for preparing a polyisocyanate according to any one of claims 1 - 19, comprising: i. Reacting a system comprising an organic polyhydroxy compound and an excess of toluene diisocyanate to obtain a prepolymer reaction mixture at a reaction temperature of 85°C - 120°C for a reaction time of 1 hour - 24 hours; ii. Separating and removing the unreacted toluene diisocyanate from the prepolymer reaction mixture obtained in step i; and iii. Adding an organic solvent for dilution to obtain the polyisocyanate.

21. The method according to claim 20, wherein, the reaction temperature in step i is 85°C - 110°C.

22. The method according to claim 20, wherein, the reaction temperature in step i is 90°C - 98°C.

23. The method according to claim 20, wherein, the reaction time in step i is 1.2 hours - 7 hours.

24. The method according to claim 20, wherein, the reaction time in step i is 1.2 hours - 4 hours.

25. The method according to claim 20, wherein, the equivalent ratio of the isocyanate groups to the hydroxyl groups in the system is 3:1 - 20:

1.

26. The method according to claim 20, wherein, the equivalent ratio of the isocyanate groups to the hydroxyl groups in the system is 3.5:1 - 10:

1.

27. The method according to claim 20, wherein, the equivalent ratio of the isocyanate groups to the hydroxyl groups in the system is 3.8:1 - 8:

1.

28. A product comprising a polyisocyanate according to any one of claims 1 - 19.

29. The product according to claim 28, wherein, the product is selected from polyurethane paints and polyurethane adhesives.

30. Use of a polyisocyanate according to any one of claims 1 - 19 as a polyisocyanate component in a polyurethane paint.

31. Use of a polyisocyanate according to any one of claims 1 - 19 as a polyisocyanate component in a polyurethane adhesive.

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