A polycarbodiimide, a method for preparing the same, and an application thereof

Abstract

The present application belongs to the technical field of polycarbodiimide preparation, and particularly relates to a polycarbodiimide, a preparation method and application thereof. The raw materials of the polycarbodiimide include toluene diisocyanate and halogenated monoisocyanate, and the content of the halogenated monoisocyanate is not higher than 20 wt% based on the total mass of the toluene diisocyanate and the halogenated monoisocyanate. The present application uses the halogenated monoisocyanate and the toluene diisocyanate as raw materials, and limits the content of the halogenated monoisocyanate. When the polycarbodiimide is prepared, the halogenated monoisocyanate acts as an end-capping agent, which can prevent the loss of carbodiimide groups caused by residual isocyanate after the reaction is completed. When the polycarbodiimide is applied to polyurethane soft foam, the physical properties such as water resistance, mechanical properties and durability can be improved.

Description

Technical Field

[0001] This invention belongs to the field of polycarbodiimide preparation technology, specifically relating to a polycarbodiimide, its preparation method, and its application. Background Technology

[0002] Flexible polyurethane foam (PU foam for short) is a polymer material widely used in furniture, automotive seats, mattresses, and other fields, possessing excellent elasticity, softness, and cushioning properties. Polyurethane foaming is a complex process involving the chemical reaction of polyols and isocyanates, combined with the action of a foaming agent, to form a porous structure. The performance of PU foam is mainly determined by raw materials, formulation design, and process conditions, with isocyanates and polyols being the core raw materials. Diisocyanates, with their high reactivity and low cost, have become one of the key isocyanates in the synthesis of PU foam. Diisocyanates react with polyols to form polyurethane segments, and simultaneously react with water to produce carbon dioxide gas, thus achieving the foaming process.

[0003] Polycarbodiimide is a highly reactive compound that can react with the carboxyl groups in polyurethane to form a stable acylurea structure, thereby improving the material's hydrolytic stability and chemical resistance. Introducing polycarbodiimide into polyurethane flexible foam can effectively improve its hydrolytic resistance, mechanical properties, and durability. While some research on polycarbodiimide modification exists in the prior art, most focuses on polyurethane elastomers or coatings, with limited research on polycarbodiimide additives specifically for polyurethane flexible foam.

[0004] Currently, the synthesis of polycarbodiimide mainly relies on isocyanate condensation, where diisocyanate compounds undergo a condensation reaction under a catalyst to generate carbodiimide groups. Commonly used catalysts include organophosphorus compounds (such as triphenylphosphine oxide) and metal carbonyl compounds (such as nickel tetracarbonyl). Polycarbodiimide contains unreacted isocyanate groups, which react with carbodiimide groups in adjacent segments to form urea-ketimide structures. This increases the product viscosity while reducing the proportion of carbodiimide groups. Therefore, when this polycarbodiimide is applied to polyurethane flexible foam, it does not improve hydrolysis resistance, mechanical properties, or durability. Summary of the Invention

[0005] Therefore, the technical problem to be solved by the present invention is to overcome the defects of the prior art in which unreacted isocyanate groups react with carbodiimide groups in polycarbodiimide applied to polyurethane flexible foam, which cannot improve the water resistance, mechanical properties and durability of polyurethane flexible foam, thereby providing a polycarbodiimide and its preparation method and application.

[0006] To this end, the present invention provides the following technical solution.

[0007] The present invention provides a polycarbodiimide, the raw materials of which include toluene diisocyanate and haloisocyanate, wherein the content of haloisocyanate is not higher than 20 wt% based on the total mass of toluene diisocyanate and haloisocyanate.

[0008] Monoisocyanates are compounds containing one isocyanate group.

[0009] Halogenated monoisocyanates refer to monoisocyanates that include substituents, including halogens.

[0010] As an optional implementation, the halogenated monoisocyanate includes chlorinated monoisocyanate and / or brominated monoisocyanate.

[0011] As an optional embodiment, the halogenated monoisocyanate includes at least one selected from 3-chloro-4-methylphenyl isocyanate, 5-chloro-2-methylphenyl isocyanate, 4-bromo-2-methylphenyl isocyanate (CAS No. 1591-98-6), and 3-trichloromethyl-4-methylphenyl isocyanate. The structural formulas are as follows:

[0012]

[0013] As an optional implementation, the content of toluene diisocyanate is 80wt%-99.5wt% and the content of haloisocyanate is 0.5wt%-20wt% based on the total mass of the toluene diisocyanate and haloisocyanate.

[0014] Preferably, based on the total mass of the toluene diisocyanate and the haloisocyanate, the content of the toluene diisocyanate is 85wt%-90wt%, and the content of the haloisocyanate is 10wt%-15wt%.

[0015] As an optional implementation, the polycarbodiimide has a number-average molecular weight of 1500-5000; and / or,

[0016] The mass content of toluene diisocyanate in the polycarbodiimide does not exceed 0.5 wt%.

[0017] The present invention also provides a method for preparing polycarbodiimide, comprising a polymerization reaction of toluene diisocyanate and halomonoisocyanate; wherein the content of halomonoisocyanate is not higher than 20 wt% based on the total mass of the toluene diisocyanate and halomonoisocyanate.

[0018] As an optional implementation, the content of toluene diisocyanate is 80wt%-99.5wt% and the content of haloisocyanate is 0.5wt%-20wt% based on the total mass of the toluene diisocyanate and haloisocyanate.

[0019] Preferably, based on the total mass of the toluene diisocyanate and the haloisocyanate, the content of the toluene diisocyanate is 85wt%-90wt%, and the content of the haloisocyanate is 10wt%-15wt%.

[0020] Preferably, the halogenated monoisocyanate comprises at least one of 3-chloro-4-methylphenyl isocyanate, 5-chloro-2-methylphenyl isocyanate, 4-bromo-2-methylphenyl isocyanate, and 3-trichloromethyl-4-methylphenyl isocyanate; specifically, the halogenated monoisocyanate comprises one, two, three, or four of 3-chloro-4-methylphenyl isocyanate, 5-chloro-2-methylphenyl isocyanate, 4-bromo-2-methylphenyl isocyanate, and 3-trichloromethyl-4-methylphenyl isocyanate; exemplaryly, the halogenated monoisocyanate comprises 3-chloro-4-methylphenyl isocyanate, 5-chloro-2-methylphenyl isocyanate, 4-bromo-2-methylphenyl isocyanate, and 3-trichloromethyl-4-methylphenyl isocyanate. Cyanoates; halogenated monoisocyanates include 4-bromo-2-methylphenyl isocyanate, 3-trichloromethyl-4-methylphenyl isocyanate; halogenated monoisocyanates include 3-chloro-4-methylphenyl isocyanate, 3-trichloromethyl-4-methylphenyl isocyanate; halogenated monoisocyanates include 3-chloro-4-methylphenyl isocyanate, 5-chloro-2-methylphenyl isocyanate, 4-bromo-2-methylphenyl isocyanate; halogenated monoisocyanates include 3-chloro-4-methylphenyl isocyanate, 5-chloro-2-methylphenyl isocyanate, 4-bromo-2-methylphenyl isocyanate, 3-trichloromethyl-4-methylphenyl isocyanate.

[0021] Preferably, the content of 3-chloro-4-methylphenyl isocyanate is 0.1 wt%-10 wt% based on the total mass of the toluene diisocyanate and the haloisocyanate, more preferably 2 wt%-4 wt%.

[0022] Preferably, the content of 5-chloro-2-methylphenyl isocyanate is 0.1 wt% to 20 wt% based on the total mass of the toluene diisocyanate and the haloisocyanate, more preferably 5 wt% to 10 wt%.

[0023] Preferably, the content of 4-bromo-2-methylphenyl isocyanate is 0.1 wt% to 10 wt% based on the total mass of the toluene diisocyanate and the haloisocyanate, more preferably 1 wt% to 2 wt%.

[0024] As an optional implementation, the polymerization reaction is further complicated by a step of distilling crude toluene diisocyanate to obtain toluene diisocyanate and halogenated monoisocyanate; preferably, the distillation parameters are: pressure 1-10 kPa, temperature 110-160 °C; more preferably, the distillation parameters are: pressure 4-5 kPa, temperature 145-152 °C; it should be noted that the crude toluene diisocyanate is derived from the waste (crude toluene diisocyanate) produced by the toluene diisocyanate distillation column, and after distillation, toluene diisocyanate and halogenated monoisocyanate are obtained, and the mass ratio meets the requirements of this invention; and / or,

[0025] The polymerization reaction temperature is 120-180℃; preferably, the polymerization reaction temperature is 140-160℃; and / or,

[0026] The polymerization reaction takes 5-8 hours; and / or,

[0027] The polymerization reaction may further include a step of adding a catalyst and / or a solvent; and / or,

[0028] The polymerization reaction is followed by a rotary evaporation step.

[0029] This invention employs a plate column or a structured packed column for distillation. By subjecting the crude toluene diisocyanate produced in the toluene diisocyanate distillation column to a special distillation process, this invention can yield different halogenated monoisocyanates, which can be used to prepare polycarbodiimides.

[0030] The polymerization reaction also includes a stirring step; the stirring speed is 300-500 rpm.

[0031] As an optional implementation, the solvent includes at least one selected from chlorobenzene, o-dichlorobenzene, and diethyl carbonate, preferably o-dichlorobenzene; and / or,

[0032] The amount of solvent added is 40 wt%-150 wt%, preferably 80 wt%-120 wt%, based on the total mass of the toluene diisocyanate and the haloisocyanate; and / or,

[0033] The amount of catalyst added, based on the total mass of the toluene diisocyanate and the haloisocyanate, is 2 ppm to 20 ppm, preferably 5 ppm to 10 ppm; and / or,

[0034] The catalyst comprises 1-methyl-1-oxo-2,3-dihydrophosphacyclopentene (CAS No. 872-45-7), trichloroethyl phosphate, nickel tetracarbonyl (CAS No. 13463-39-3), and 3-methyl-1-phenyl-2-phosphacyclopentene-1-oxide; preferably, 3-methyl-1-phenyl-2-phosphacyclopentene-1-oxide; and / or...

[0035] The temperature of the rotary evaporation is 80-140℃, preferably 100-120℃; and / or,

[0036] The absolute pressure of the rotary evaporator is 2-10 kPa, preferably 3-5 kPa.

[0037] Among them, 3-methyl-1-phenyl-2-phosphacyclopentene-1-oxide, also known as 3-methyl-1-phenyl-2-phosphine-1-oxide, 2,3-dihydro-4-methyl-1-phenyl-1H-1-phosphacyclopentene-2,4-diene-1-oxide, etc.

[0038] This invention provides the above-mentioned polycarbodiimide or the polycarbodiimide prepared by the above-mentioned method for use in the preparation of polyurethane flexible foam.

[0039] When preparing polyurethane flexible foam, methods known in the art are used.

[0040] The technical solution of this invention has the following advantages:

[0041] 1. The polycarbodiimide provided by this invention comprises toluene diisocyanate and halogenated monoisocyanate as raw materials. The content of halogenated monoisocyanate is no more than 20 wt% based on the total mass of the toluene diisocyanate and halogenated monoisocyanate. This invention uses halogenated monoisocyanate and toluene diisocyanate as raw materials and limits the content of halogenated monoisocyanate. When preparing polycarbodiimide, halogenated monoisocyanate acts as a capping agent, preventing the loss of carbodiimide groups due to residual isocyanate after the reaction. Applying polycarbodiimide to polyurethane flexible foam can improve its physical properties such as water resistance, mechanical properties, and durability.

[0042] Since isocyanate reacts with carbodiimide, monoisocyanate has an isocyanate group. In the polymerization reaction to prepare polycarbodiimide, it can be used as a capping agent to prevent residual isocyanate from reacting with carbodiimide and causing the loss of carbodiimide groups, thereby increasing the proportion of polycarbodiimide groups in the product. At the same time, the introduction of halogen can also reduce the catalytic reaction rate of carbodiimide, resulting in a more uniform molecular weight distribution.

[0043] The substituents in monoisocyanates include halogens, which can inhibit isocyanate activity during carbodiimide synthesis, preventing the isocyanate from reacting with the carbodiimide group to form a urea-ketimide structure. Using specific amounts of halogenated monoisocyanates as raw materials can reduce the NCO content in polycarbodiimides and control the molecular weight, thus improving water resistance, mechanical properties, and durability when applied to polyurethane flexible foams.

[0044] 2. The method for preparing polycarbodiimide provided by the present invention has a number average molecular weight of 1500-3000, which is beneficial to further improve the thermal stability of polyurethane flexible foam under high temperature conditions, and is easy to dissolve in organic solvents or toluene diisocyanate, making it convenient to disperse during use.

[0045] This invention involves distilling waste materials from a toluene diisocyanate distillation column, namely crude toluene diisocyanate, under specific conditions. The resulting products, toluene diisocyanate and halogenated monoisocyanate, can be used to prepare polycarbodiimide. When applied to polyurethane flexible foam, these products can improve its physical properties such as water resistance, mechanical properties, and durability, while simultaneously realizing the resource utilization of waste materials.

[0046] The polycarbodiimide prepared by this invention has a toluene diisocyanate residue of no more than 0.5%, and after rotary evaporation, it becomes a solid powder that can be directly used as an additive in the production of polyurethane flexible foam.

[0047] 3. The method for preparing polycarbodiimide provided by the present invention, by optimizing the formula, improving the process conditions and the amount of raw materials, can better utilize the waste generated by the toluene diisocyanate refining tower. When carbodiimide is applied to polyurethane flexible foam, it can further improve hydrolysis resistance, mechanical properties and durability. On the basis of realizing the reuse of waste materials, it can reduce production costs and achieve green environmental protection. Detailed Implementation

[0048] The following embodiments are provided to better understand the present invention and are not limited to the preferred embodiments described. They do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention.

[0049] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0050] The main raw material sources involved in the various embodiments and comparative examples of this invention are as follows; unless otherwise specified, all raw materials were obtained from ordinary commercial channels:

[0051] 3-Methyl-1-phenyl-2-phosphacyclopentene-1-oxide, purity ≥95.0%, THIAI (Shanghai) Chemical Industry Development Co., Ltd., CAS No. 707-61-9;

[0052] WANNATE TDI-80, purity ≥99.9%, Wanhua Chemical Group Co., Ltd.

[0053] WANOL F3156D, purity ≥99.9%, Wanhua Chemical Group Co., Ltd.

[0054] o-Dichlorobenzene, diethyl carbonate, purity ≥99%, Beijing Inokai Technology Co., Ltd.;

[0055] Amine catalyst Niax TM Catalyst A-33, purity ≥99%, Momentive.

[0056] Tin catalyst Niax TM Catalyst Stannous Octanoate T9, purity ≥99%, Momentive

[0057] Silicone oil Niax TM Silicone L-580, purity ≥99%, Momentive

[0058] Example 1

[0059] This embodiment provides a method for preparing polycarbodiimide, including the following steps:

[0060] (1) Toluene diisocyanate crude product (toluene diisocyanate abbreviation TDI, content 96.5wt%, 3-chloro-4-methylphenyl isocyanate 1.2wt%, 5-chloro-2-methylphenyl isocyanate 2.1wt%, other impurities 0.2%, crude toluene diisocyanate abbreviation TDI crude product, which comes from the waste generated by the toluene diisocyanate distillation column) was distilled in a plate column at a temperature of 121℃ and a pressure of 2.5kPa to obtain the distillation product; the composition of the distillation product was analyzed by an Agilent 7890B gas chromatograph. The distillation product included: 3-chloro-4-methylphenyl isocyanate 2.1wt%, 5-chloro-2-methylphenyl isocyanate 4.7wt%, and TDI 93.2wt%.

[0061] (2) 100g of the above distillation product, 100g of o-dichlorobenzene, and 1000μg of 3-methyl-1-phenyl-2-phosphacyclopentene-1-oxide were stirred and mixed evenly at 150℃ and 400rpm for 8h to obtain a mixed solution of polycarbodiimide and o-dichlorobenzene.

[0062] (3) The above mixed solution was subjected to rotary evaporation at 140°C and 3 kPa absolute pressure to remove the organic solvent and obtain polycarbodiimide powder.

[0063] Example 2

[0064] This embodiment provides a method for preparing polycarbodiimide, including the following steps:

[0065] (1) TDI crude product (TDI 95.5wt%, 3-chloro-4-methylphenyl isocyanate 1.0wt%, 5-chloro-2-methylphenyl isocyanate 2.7wt%, 4-bromo-2-methylphenyl isocyanate 0.6wt%, other impurities 0.2%) was distilled in a plate column at a temperature of 135℃ and a pressure of 2.7kPa to obtain the distillation product; the composition of the distillation product was analyzed by an Agilent 7890B gas chromatograph, and the distillation product included: 3.6wt% 3-chloro-4-methylphenyl isocyanate, 5.6wt% 5-chloro-2-methylphenyl isocyanate, 2.1wt% 4-bromo-2-methylphenyl isocyanate, and 88.7wt% TDI.

[0066] (2) 100g of the above distillation product, 100g of diethyl carbonate, and 1000μg of 3-methyl-1-phenyl-2-phosphacyclopentene-1-oxide were stirred and mixed evenly at 120℃ and 400rpm for 7h to obtain a mixed solution of polycarbodiimide and diethyl carbonate.

[0067] (3) The above mixed solution was rotary evaporated at 100°C and 2.5 kPa absolute pressure to remove the organic solvent and obtain polycarbodiimide powder.

[0068] Example 3

[0069] This embodiment provides a method for preparing polycarbodiimide, including the following steps:

[0070] (1) TDI crude product (TDI 92.6wt%, 3-trichloromethyl-4-methylphenyl isocyanate 2.2wt%, 3-chloro-4-methylphenyl isocyanate 3.7wt%, 5-chloro-2-methylphenyl isocyanate 1.3wt%, other impurities 0.2%) was distilled in a plate column at a temperature of 140℃ and a pressure of 3.1kPa to obtain the distillation product; the composition of the distillation product was analyzed by an Agilent 7890B gas chromatograph, and the distillation product included: 3-trichloromethyl-4-methylphenyl isocyanate 4.9wt%, 3-chloro-4-methylphenyl isocyanate 7.3wt%, 5-chloro-2-methylphenyl isocyanate 2.4wt%, and TDI 85.4wt%.

[0071] (2) 100g of the above distillation product, 100g of o-dichlorobenzene, and 1000μg of 3-methyl-1-phenyl-2-phosphacyclopentene-1-oxide were stirred and mixed evenly at 150℃ and 500rpm for 6h to obtain a mixed solution of polycarbodiimide and o-dichlorobenzene.

[0072] (3) The above mixed solution was subjected to rotary evaporation at 120°C and 3 kPa absolute pressure to remove the organic solvent and obtain polycarbodiimide powder.

[0073] Example 4

[0074] This embodiment provides a method for preparing polycarbodiimide, including the following steps:

[0075] (1) 3-chloro-4-methylphenyl isocyanate, 5-chloro-2-methylphenyl isocyanate and toluene diisocyanate were mixed in a mass ratio of 2.1:4.7:93.2 to obtain a mixture;

[0076] (2) 100g of the above mixture, 100g of o-dichlorobenzene, and 1000μg of 3-methyl-1-phenyl-2-phosphacyclopentene-1-oxide were stirred and mixed evenly at 150℃ and 400rpm for 8h to obtain a mixed solution of polycarbodiimide and o-dichlorobenzene.

[0077] (3) The above mixed solution was subjected to rotary evaporation at 140°C and 3 kPa absolute pressure to remove the organic solvent and obtain polycarbodiimide powder.

[0078] Example 5

[0079] This embodiment provides a method for preparing polycarbodiimide, including the following steps:

[0080] (1) 3-chloro-4-methylphenyl isocyanate, 5-chloro-2-methylphenyl isocyanate, 4-bromo-2-methylphenyl isocyanate and toluene diisocyanate were mixed in a mass ratio of 0.1:2.8:9.8:87.3 to obtain a mixture;

[0081] (2) 100g of the above mixture, 100g of o-dichlorobenzene, and 2000μg of 1-methyl-1-oxo-2,3-dihydro-phosphacyclopentene were stirred and mixed evenly at 150℃ and 400rpm for 6h to obtain a mixed solution of polycarbodiimide and o-dichlorobenzene.

[0082] (3) The above mixed solution was rotary evaporated at 90°C and 2 kPa absolute pressure to remove the organic solvent and obtain polycarbodiimide powder.

[0083] Example 6

[0084] This embodiment provides a method for preparing polycarbodiimide, including the following steps:

[0085] (1) 3-chloro-4-methylphenyl isocyanate, 5-chloro-2-methylphenyl isocyanate, 4-bromo-2-methylphenyl isocyanate and toluene diisocyanate were mixed in a mass ratio of 9.8:0.1:0.1:90 to obtain a mixture;

[0086] (2) 100g of the above mixture, 100g of chlorobenzene, and 2000μg of trichloroethyl phosphate were stirred and mixed evenly at 120℃ and 400rpm for 8h to obtain a mixed solution of polycarbodiimide and chlorobenzene.

[0087] (3) The above mixed solution was rotary evaporated at 130°C and 8 Pa absolute pressure to remove the organic solvent and obtain polycarbodiimide powder.

[0088] Example 7

[0089] This embodiment provides a method for preparing polycarbodiimide, including the following steps:

[0090] (1) 4-Bromo-2-methylphenyl isocyanate and toluene diisocyanate were mixed in a mass ratio of 10:90 to obtain a mixture;

[0091] (2) 100g of the above mixture, 100g of chlorobenzene, and 2000μg of 1-methyl-1-oxo-2,3-dihydro-phosphacyclopentene were stirred and mixed evenly at 120℃ and 400rpm for 8h to obtain a mixed solution of polycarbodiimide and chlorobenzene.

[0092] (3) The above mixed solution was rotary evaporated at 130°C and 8 Pa absolute pressure to remove the organic solvent and obtain polycarbodiimide powder.

[0093] Example 8

[0094] This embodiment provides a method for preparing polycarbodiimide, including the following steps:

[0095] (1) 5-chloro-2-methylphenyl isocyanate and toluene diisocyanate were mixed at a mass ratio of 20:80 to obtain a mixture;

[0096] (2) 100g of the above mixture, 100g of chlorobenzene, and 200μg of 3-methyl-1-phenyl-2-phosphacyclopentene-1-oxide were stirred and mixed evenly at 180℃ and 400rpm for 6h to obtain a mixed solution of polycarbodiimide and chlorobenzene.

[0097] (3) The above mixed solution was subjected to rotary evaporation at 120°C and 3Pa absolute pressure to remove the organic solvent and obtain polycarbodiimide powder.

[0098] Comparative Example 1

[0099] This comparative example provides a method for preparing polycarbodiimide, comprising the following steps:

[0100] (1) 100g TDI-80 (halogen-free) and 100g o-dichlorobenzene were stirred and mixed evenly at 150℃ and 400rpm for 8h to obtain a mixed solution of polycarbodiimide and o-dichlorobenzene.

[0101] (2) The above mixed solution was subjected to rotary evaporation at 140°C and 3 kPa absolute pressure to remove the organic solvent and obtain polycarbodiimide powder.

[0102] Comparative Example 2

[0103] This comparative example provides a method for preparing polycarbodiimide, comprising the following steps:

[0104] (1) TDI crude product (1.3 wt% 3-chloro-4-methylphenyl isocyanate, 3.3 wt% 5-chloro-2-methylphenyl isocyanate, 95.2 wt% TDI, and 0.2% other impurities) was distilled in a plate column at 121℃ and 2.5 kPa to obtain the distillation product. The composition of the distillation product was analyzed using an Agilent 7890B gas chromatograph. The distillation product included 2.1 wt% 3-chloro-4-methylphenyl isocyanate, 5.6 wt% 5-chloro-2-methylphenyl isocyanate, and 93.2 wt% TDI. 3-chloro-4-methylphenyl isocyanate and 5-chloro-2-methylphenyl isocyanate were added to the distillation product to obtain a mixture containing 13.5 wt% 3-chloro-4-methylphenyl isocyanate, 17.7 wt% 5-chloro-2-methylphenyl isocyanate, and 68.8 wt% TDI.

[0105] (2) 100g of the above mixture, 100g of o-dichlorobenzene, and 1000μg of 1-methyl-1-oxo-2,3-dihydro-phosphacyclopentene were stirred and mixed evenly at 150℃ and 400rpm for 8h to obtain a mixed solution of polycarbodiimide and o-dichlorobenzene.

[0106] (3) The above mixed solution was subjected to rotary evaporation at 140°C and 3 kPa absolute pressure to remove the organic solvent and obtain polycarbodiimide powder.

[0107] Application Example 1

[0108] This application example demonstrates the use of polycarbodiimide in the preparation of polyurethane flexible foam, including the following steps:

[0109] Raw materials include:

[0110] Polyether F3156D: 100g

[0111] Silicone oil L-580: 1g

[0112] Amine catalyst A33: 0.2g

[0113] Tin-based catalyst T9: 0.14g

[0114] Water: 4g

[0115] TDI-80: 52g

[0116] Polycarbodiimide (from the examples and comparative examples, respectively): 1g

[0117] The above raw materials were mixed evenly to form a foaming material. The ambient temperature and the foaming material temperature were kept consistent, the ambient humidity was 45%, and the foaming material temperature was 24.5℃. The mixture was allowed to mature for 48 hours. A control group was used without the addition of polycarbodiimide.

[0118] The above embodiments and comparative examples were obtained by applying the above methods to obtain polyurethane flexible foams.

[0119] Test Example 1

[0120] This test example provides the performance parameters of the polycarbodiimides prepared in each embodiment and comparative example, as follows:

[0121] Test method for residual NCO: WanTong 905-Titrando potentiometric titration analysis;

[0122] Table 1. Test results of polycarbodiimide

[0123]

[0124] Test Example 2

[0125] This test example provides the performance of the polyurethane flexible foam prepared in Example 1, with the control group not containing polycarbodiimide. The results are as follows:

[0126] Tensile strength and elongation at break test methods: The testing instrument is a universal tensile testing machine, TCS-2000-D, manufactured by High-Speed ​​Rail Testing Instruments Co., Ltd. Tensile strength (MPa) and elongation at break (%) are tested according to GB / T 528-2009 standard.

[0127] Test method for hydrolysis resistance: According to GB / T 1844-2008 standard, the sample is placed in an environment of 70℃ and 95% humidity for 7 days, and the tensile strength retention rate and mass loss rate are tested. The tensile strength retention rate is calculated according to the following formula:

[0128]

[0129] The tensile strength after hydrolysis was obtained by testing the tensile strength using the method described above.

[0130] The mass loss rate is calculated using the following formula:

[0131]

[0132] Test methods for foam density and foam appearance: Measure the foam density (kg / m³) after foaming. 3 Observe the foam morphology after maturation; foam morphology includes normal and shrunken foams. When the foam density is higher than 35 kg / m³, the morphology is considered normal. 3 At that time, the appearance of the foam is recorded as shrinkage, and the foam density is no higher than 35 kg / m³. 3 At that time, the appearance of the foam was recorded as normal.

[0133] Test method for compression set: Compress at 70℃ for 22 hours according to GB / T 6669-2008 standard. After compression, measure the height. The deformation recovery rate is calculated using the following formula:

[0134]

[0135] Table 2. Test results of polyurethane flexible foam prepared from polycarbodiimide.

[0136]

[0137]

[0138] As can be seen from the performance test results in Table 2, the polycarbodiimide provided by this invention can improve properties such as hydrolysis resistance, tensile strength, and elongation at break when applied to polyurethane flexible foam, and also improve the appearance of the foam. Furthermore, comparing Examples 1-2, it is evident that the polycarbodiimide obtained by this invention, using a specific content of halogenated monoisocyanate as a raw material, exhibits significant effects when applied to polyurethane flexible foam.

[0139] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A polycarbodiimide, characterized in that, Its raw materials include toluene diisocyanate and halogenated monoisocyanate, and the content of halogenated monoisocyanate is not higher than 20 wt% based on the total mass of toluene diisocyanate and halogenated monoisocyanate.

2. The polycarbodiimide according to claim 1, characterized in that, The halogenated monoisocyanates include chlorinated monoisocyanates and / or brominated monoisocyanates.

3. The polycarbodiimide according to claim 2, characterized in that, The halogenated monoisocyanate includes at least one of 3-chloro-4-methylphenyl isocyanate, 5-chloro-2-methylphenyl isocyanate, 4-bromo-2-methylphenyl isocyanate, and 3-trichloromethyl-4-methylphenyl isocyanate.

4. The polycarbodiimide according to any one of claims 1-3, characterized in that, Based on the total mass of the toluene diisocyanate and the haloisocyanate, the content of the toluene diisocyanate is 80wt%-99.5wt%, and the content of the haloisocyanate is 0.5wt%-20wt%. Preferably, based on the total mass of the toluene diisocyanate and the haloisocyanate, the content of the toluene diisocyanate is 85wt%-90wt%, and the content of the haloisocyanate is 10wt%-15wt%.

5. The polycarbodiimide according to any one of claims 1-4, characterized in that, The number-average molecular weight of the polycarbodiimide is 1500-5000; and / or, The mass content of toluene diisocyanate in the polycarbodiimide does not exceed 0.5 wt%.

6. A method for preparing polycarbodiimide, characterized in that, The polymerization reaction involves toluene diisocyanate and halomonoisocyanate; the content of halomonoisocyanate is not higher than 20 wt% based on the total mass of toluene diisocyanate and halomonoisocyanate.

7. The preparation method according to claim 6, characterized in that, Based on the total mass of the toluene diisocyanate and the haloisocyanate, the content of the toluene diisocyanate is 80wt%-99.5wt%, and the content of the haloisocyanate is 0.5wt%-20wt%. Preferably, based on the total mass of the toluene diisocyanate and the haloisocyanate, the content of the toluene diisocyanate is 85wt%-90wt%, and the content of the haloisocyanate is 10wt%-15wt%. Preferably, the halogenated monoisocyanate includes at least one of 3-chloro-4-methylphenyl isocyanate, 5-chloro-2-methylphenyl isocyanate, 4-bromo-2-methylphenyl isocyanate, and 3-trichloromethyl-4-methylphenyl isocyanate; Preferably, the content of 3-chloro-4-methylphenyl isocyanate is 0.1 wt%-10 wt% based on the total mass of the toluene diisocyanate and the haloisocyanate, more preferably 2 wt%-4 wt%. Preferably, the content of 5-chloro-2-methylphenyl isocyanate is 0.1 wt% to 20 wt% based on the total mass of the toluene diisocyanate and the haloisocyanate, more preferably 5 wt% to 10 wt%. Preferably, the content of 4-bromo-2-methylphenyl isocyanate is 0.1 wt% to 10 wt% based on the total mass of the toluene diisocyanate and the haloisocyanate, more preferably 1 wt% to 2 wt%.

8. The preparation method according to claim 6 or 7, characterized in that, The polymerization reaction is preceded by a step of distilling crude p-toluene diisocyanate to obtain the toluene diisocyanate and halogenated monoisocyanate; preferably, the distillation parameters are: pressure 1-10 kPa, temperature 110-160 °C; more preferably, the distillation parameters are: pressure 4-5 kPa, temperature 145-152 °C; and / or, The polymerization reaction temperature is 120-180℃; preferably, the polymerization reaction temperature is 140-160℃; and / or, The polymerization reaction takes 5-8 hours; and / or, The polymerization reaction may further include a step of adding a catalyst and / or a solvent; and / or, The polymerization reaction is followed by a rotary evaporation step.

9. The preparation method according to claim 8, characterized in that, The solvent includes at least one of chlorobenzene, o-dichlorobenzene, and diethyl carbonate, preferably o-dichlorobenzene; and / or, The amount of solvent added is 40 wt% to 150 wt%, preferably 80 wt% to 120 wt%, based on the total mass of the toluene diisocyanate and the haloisocyanate; and / or, The amount of catalyst added, based on the total mass of the toluene diisocyanate and the haloisocyanate, is 2 ppm to 20 ppm, preferably 5 ppm to 10 ppm; and / or, The catalyst comprises 1-methyl-1-oxo-2,3-dihydrophosphacyclopentene, trichloroethyl phosphate, nickel tetracarbonyl, and 3-methyl-1-phenyl-2-phosphacyclopentene-1-oxide; preferably, 3-methyl-1-phenyl-2-phosphacyclopentene-1-oxide; and / or, The temperature of the rotary evaporation is 80-140℃, preferably 100-120℃; and / or, The absolute pressure of the rotary evaporator is 2-10 kPa, preferably 3-5 kPa.

10. The polycarbodiimide according to any one of claims 1-5 or the polycarbodiimide prepared by the preparation method according to any one of claims 6-9 is used to prepare polyurethane flexible foam.

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