Polycarbodiimide and preparation method thereof

Abstract

The invention provides polycarbodiimide and a preparation method thereof. The preparation method comprises the following steps: S1, carrying out first reaction on a first raw material and a second raw material to obtain a first mixture; the first raw material comprises diisocyanate, and the second raw material comprises monohydric alcohol and / or monoamine; the first mixed solution comprises an intermediate product, the intermediate product only contains one NCO group, and the mass of the NCO group in the first mixture accounts for 20-30% of the mass of the first mixed solution; and S2, adding a second catalyst into the first mixture, and carrying out condensation reaction on the intermediate product and diisocyanate to obtain polycarbodiimide. The polycarbodiimide prepared by the method is high in number-average molecular weight, narrow in molecular weight distribution and low in viscosity in the preparation process.

Description

Technical Field

[0001] The invention relates to a polycarbodiimide and a preparation method thereof. Background Art

[0002] Polycarbodiimide is a class of compounds containing NCN groups, which can react with carboxyl groups and are often used as anti-hydrolysis agents in polyester materials to improve the service life of materials in hot and humid environments. There are many reports on the preparation methods of polycarbodiimide. The mainstream method is to use bulk polymerization, that is, under the protection of inert gas and at a certain temperature, in the presence of a catalyst, diisocyanate is polymerized under reduced pressure or normal pressure to produce carbodiimide oligomers, and then end-capped with monohydric / dihydric alcohols or amines. This method is acceptable for preparing polycarbodiimide with lower molecular weight, but it will encounter difficulties when preparing polycarbodiimide with higher molecular weight. The viscosity of the system is large, the stirring is insufficient, and the process cannot be scaled up. In this regard, some existing technologies add solvents to dissolve after preparing the oligomers of carbodiimide, and then end-capped. This method can solve the problem of increased viscosity of the system, but how to remove the added solvent later is a problem. It not only has safety hazards but also increases costs. It is only suitable for preparing solvent-based products. Moreover, the polycarbodiimide prepared by the above preparation method also has the problem of large molecular weight distribution PDI. Summary of the invention

[0003] In order to overcome the problems of low molecular weight and large PDI of polycarbodiimide prepared in the prior art, the present invention provides a polycarbodiimide and a preparation method thereof. The polycarbodiimide prepared by the method has high molecular weight, narrow molecular weight distribution, and low viscosity during the preparation process.

[0004] The present invention provides a method for preparing polycarbodiimide, which comprises the following steps:

[0005] S1, performing a first reaction on a first raw material and a second raw material to obtain a first mixture; the first raw material comprises a diisocyanate, and the second raw material comprises a monohydric alcohol and / or a monoamine; the first mixed solution comprises an intermediate product, the intermediate product contains only one NCO group, and the mass percentage of the NCO group in the first mixture accounts for 20%-30% of the mass percentage of the first mixed solution;

[0006] S2. Adding a second catalyst to the first mixture, and subjecting the intermediate product to a condensation reaction with diisocyanate to obtain polycarbodiimide.

[0007] In the present invention, the NCO group is an O=C=N-group, isocyanate is a general term for various esters of isocyanic acid, and the diisocyanate means an isocyanate containing two NCO groups.

[0008] In the present invention, preferably, the diisocyanate is an aliphatic diisocyanate and / or an aromatic diisocyanate.

[0009] The aliphatic diisocyanate is, for example, one or more of hexamethylene diisocyanate, isophorone diisocyanate and dicyclohexylmethane diisocyanate.

[0010] The aromatic diisocyanate is, for example, one or more of toluene diisocyanate, diphenylmethane diisocyanate, p-phenylene diisocyanate, naphthalene diisocyanate, xylylene diisocyanate, dimethylene diphenylmethane diisocyanate and tetramethylxylylene diisocyanate.

[0011] In the present invention, preferably, the intermediate product is subjected to a condensation reaction with diisocyanate to obtain a second mixture, and when the NCO group content in the second mixture is 0, polycarbodiimide is obtained.

[0012] In the present invention, the monohydric alcohol is, for example, one or more of methanol, ethanol, n-propanol, isobutanol, tert-butanol, isooctyl alcohol, tridecanol, isopropanol and octadecenol.

[0013] In the present invention, the monoamine is, for example, one or more of methylamine, ethylamine, n-propylamine, isopropylamine, n-butylamine, tert-butylamine, cyclohexylamine and benzylamine.

[0014] In certain specific embodiments of the present invention, the first raw material is dicyclohexylmethane diisocyanate, and the second raw material is isooctyl alcohol.

[0015] In the present invention, preferably, the molecular weight of the second raw material is less than 300 g / mol, more preferably 60-270 g / mol, for example 130 g / mol, 200 g / mol or 268.5 g / mol.

[0016] In the present invention, preferably, the molar percentage of the second raw material to the first raw material is 5%-40%, more preferably 5%-33%, further more preferably 5%-20%, for example 17% or 18%.

[0017] In certain specific embodiments of the present invention, the first reaction is carried out under the action of a first catalyst, and the first catalyst is an organic metal compound and / or an amine compound.

[0018] The organometallic compound is, for example, one or more of dibutyltin dilaurate, dioctyltin dilaurate, stannous acetate, zinc acetate and bismuth neodecanoate.

[0019] The amine compound is, for example, one or more of triethylamine, trimethylamine, N,N-dimethylcyclohexylamine and triethylenediamine.

[0020] The mass percentage of the first catalyst to the first raw material is preferably 0-1%, and more preferably 0.01-1%.

[0021] In certain preferred embodiments of the present invention, the first reaction is not carried out under the action of a first catalyst.

[0022] In certain specific embodiments of the present invention, the mixing step is: adding the second raw material into the first raw material.

[0023] The adding is, for example, all-at-once adding or dropwise adding, preferably dropwise adding.

[0024] The dropping time is preferably 0.5-3 h, for example 1 h.

[0025] In the present invention, the temperature of the first reaction is preferably 30-120°C, more preferably 50-100°C.

[0026] In the present invention, preferably, the first reaction is carried out under an atmosphere of an inert gas, such as nitrogen, argon, helium or neon, preferably nitrogen.

[0027] In the present invention, preferably, the first reaction time is 1-5 h, for example, 1 h or 2 h.

[0028] In the present invention, preferably, the mass percentage of the NCO groups in the first mixture to the mass percentage of the first mixture is 20%-27%, for example, 21.3%, 22.80%, 24.8% or 26.6%.

[0029] In the present invention, preferably, the mass percentage of the second catalyst to the first raw material is 0.02%-2%, for example, 0.2%.

[0030] In the present invention, preferably, the second catalyst is an organic phosphorus compound.

[0031] The organic phosphorus compound is, for example, one or more of 3-methyl-1-phenyl-2-phospholene-1-oxide, 1-ethyl-2-phospholene-1-oxide and 1-methyl-3-chloro-2-phospholene-1-oxide.

[0032] In the present invention, preferably, the condensation reaction is carried out under an atmosphere of an inert gas, such as nitrogen, argon, helium or neon, preferably nitrogen.

[0033] In the present invention, the temperature of the condensation reaction is preferably 50-220°C, more preferably 120-200°C, for example 160°C.

[0034] In the present invention, preferably, the pressure of the condensation reaction is 200-101325Pa, for example, 1000Pa.

[0035] In the present invention, preferably, the condensation reaction further includes the following steps: forming a second mixture after the condensation reaction, the mass percentage of NCO groups in the second mixture accounting for 1%-3% of the mass percentage of the second mixture; adding a third raw material to the second mixture for a second reaction, the third raw material including a monohydric alcohol and / or a monoamine.

[0036] The monohydric alcohol is, for example, one or more of methanol, ethanol, n-propanol, isobutanol and tert-butanol.

[0037] The monoamine is, for example, one or more of methylamine, ethylamine, n-propylamine, isopropylamine, n-butylamine, tert-butylamine, cyclohexylamine and benzylamine.

[0038] Preferably, the mass percentage of NCO groups in the second mixture formed after the condensation reaction accounts for 2.8% of the mass percentage of the second mixture.

[0039] The temperature of the second reaction is preferably 30-120°C, more preferably 50-100°C.

[0040] Preferably, the second reaction is carried out under an atmosphere of an inert gas, such as nitrogen, argon, helium or neon, preferably nitrogen.

[0041] Preferably, the second reaction time is 1-5 h, for example, 1 h or 2 h.

[0042] In the present invention, the second raw material and the third raw material may be of the same or different types.

[0043] The present invention also provides a polycarbodiimide prepared by the preparation method of the polycarbodiimide.

[0044] In the present invention, the number average molecular weight of the polycarbodiimide may be greater than 1400, for example, greater than 2700.

[0045] In the present invention, the PDI of the polycarbodiimide may be less than 1.65, for example, 1.15, 1.21, 1.26, 1.31, 1.36 or 1.65. PDI is the molecular weight distribution, and the smaller the PDI, the narrower the molecular weight distribution.

[0046] In the present invention, the softening point of the polycarbodiimide may be above 50°C, for example, 50°C, 54°C, 57°C, 61°C, 72°C or 83°C.

[0047] In the present invention, the thermal decomposition temperature of the polycarbodiimide may be above 246°C, for example, 246°C, 253°C, 255°C, 267°C, 295°C or 334°C.

[0048] On the basis of being in accordance with the common sense in the art, the above-mentioned preferred conditions can be arbitrarily combined to obtain the preferred embodiments of the present invention.

[0049] The reagents and raw materials used in the present invention are commercially available.

[0050] The positive and progressive effects of the present invention are:

[0051] The polycarbodiimide prepared by the preparation method of the polycarbodiimide of the present invention has the advantages of high molecular weight and low molecular weight distribution PDI, and has low viscosity during the preparation process while having high molecular weight, which is conducive to industrial scale-up, and the process is safe and environmentally friendly. At the same time, the polycarbodiimide also has the advantages of high softening point and thermal decomposition temperature. DETAILED DESCRIPTION

[0052] The present invention is further described below by way of examples, but the present invention is not limited to the scope of the examples. The experimental methods in the following examples without specifying specific conditions are carried out according to conventional methods and conditions, or selected according to the product specifications.

[0053] The suppliers, models and purity information of the main raw materials used in the following examples and comparative examples are as follows:

[0054] Dicyclohexylmethane diisocyanate (HMDI) was purchased from Wanhua Chemical, model WANNATE, with a purity of ≥99.5%;

[0055] 3-Methyl-1-phenyl-2-phosphotene-1-oxide (MPPO) was purchased from TCI with a purity of ≥95.0% (RG);

[0056] Isooctyl alcohol was purchased from Exploration, with a purity of ≥99.0% (RG); molecular weight of 130 g / mol;

[0057] Polyethylene glycol 300 was purchased from Haian Petrochemical, with the model number of PEG-300 and a hydroxyl value of 340-416 mgKOH / g.

[0058] Example 1

[0059] 1000 g of HMDI (3.8 mol, NCO% 32.1%) was added to a 5 L three-necked flask equipped with a stirrer, nitrogen was passed through, the temperature was controlled at 100°C, 164 g of isooctyl alcohol (molecular weight 130, 1.26 mol) was added dropwise, the addition was completed within 1 hour, and the first reaction was carried out for 2 hours to obtain a first mixture; the first mixture included unreacted diisocyanate and an intermediate product, and the intermediate product contained only one NCO group;

[0060] When the mass percentage of the NCO group in the first mixture is 22.8%, 2 g of MPPO is added to the three-necked flask, the temperature is raised to 160° C., the pressure is 1000 Pa, and the condensation reaction is carried out for 22 hours to obtain the second mixture. When the NCO group content in the second mixture is 0, polycarbodiimide is obtained.

[0061] The mass percentage of NCO groups is determined by referring to the method for determining the isocyanate content in Part 4 of Aromatic Isocyanates for Polyurethane Production in GBT 12009.4-2016.

[0062] Example 2

[0063] 1000 g of HMDI (3.8 mol, NCO% 32.1%) was added to a 5 L three-necked flask equipped with a stirrer, nitrogen was passed through, the temperature was controlled at 100°C, 82 g of isooctyl alcohol (0.63 mol) was added dropwise, and the addition was completed within 1 hour. The first reaction was carried out for 1 hour to obtain a first mixture; the first mixture included unreacted diisocyanate and an intermediate product, and the intermediate product contained only one NCO group;

[0064] When the mass percentage of the NCO group in the first mixture is 27%, 2 g of MPPO is added to the three-necked flask, the temperature is raised to 160° C., the pressure is 1000 Pa, and the condensation reaction is carried out for 15 hours to obtain a second mixture;

[0065] When the mass percentage of the NCO group in the second mixture is 2.8%, 82 g of isooctyl alcohol (0.63 mol) is added to the second mixture for a second reaction for 2 h. The second reaction temperature is 100° C. When the content of the NCO group is 0, polycarbodiimide is obtained.

[0066] Example 3

[0067] 1000 g of HMDI (3.8 mol, NCO% 32.1%) was added to a 5 L three-necked flask equipped with a stirrer, nitrogen was passed through, the temperature was controlled at 100°C, 91 g of isooctyl alcohol (0.7 mol) was added dropwise, and the addition was completed within 1 hour. The first reaction was carried out for 1 hour to obtain a first mixture; the first mixture included unreacted diisocyanate and an intermediate product, and the intermediate product contained only one NCO group;

[0068] When the mass percentage of the NCO group in the first mixture is 26.6%, 2 g of MPPO is added to the three-necked flask, the temperature is raised to 160° C., the pressure is 1000 Pa, and the condensation reaction is carried out for 30 hours to obtain the second mixture. When the NCO group content in the second mixture is 0, polycarbodiimide is obtained.

[0069] Example 4

[0070] 1000 g of HMDI (3.8 mol, NCO% 32.1%) was added to a 5 L three-necked flask equipped with a stirrer, nitrogen was passed through, the temperature was controlled at 100°C, and 252 g of tridecanol (molecular weight 200, 1.26 mol) was added dropwise. The addition was completed within 1 hour. The first reaction was carried out for 2 hours to obtain a first mixture; the first mixture included unreacted diisocyanate and an intermediate product, and the intermediate product contained only one NCO group;

[0071] When the mass percentage of the NCO group in the first mixture is 21.3%, 2 g of MPPO is added to the three-necked flask, the temperature is raised to 160° C., the pressure is 1000 Pa, and the condensation reaction is carried out for 23 hours to obtain the second mixture. When the NCO group content in the second mixture is 0, polycarbodiimide is obtained.

[0072] Example 5

[0073] 1000 g of HMDI (3.8 mol, NCO% 32.1%) was added to a 5 L three-necked flask equipped with a stirrer, nitrogen was passed through, the temperature was controlled at 100°C, and 76 g of isopropanol (molecular weight 60.1, 1.26 mol) was added dropwise. The addition was completed within 1 hour. The first reaction was carried out for 2 hours to obtain a first mixture; the first mixture included unreacted diisocyanate and an intermediate product, and the intermediate product contained only one NCO group;

[0074] When the mass percentage of the NCO group in the first mixture is 24.8%, 2 g of MPPO is added to the three-necked flask, the temperature is raised to 160° C., the pressure is 1000 Pa, and the condensation reaction is carried out for 19 hours to obtain the second mixture. When the NCO group content in the second mixture is 0, polycarbodiimide is obtained.

[0075] Example 6

[0076] 1000 g of HMDI (3.8 mol, NCO% 32.1%) was added to a 5 L three-necked flask equipped with a stirrer, nitrogen was passed through, the temperature was controlled at 100° C., 338 g of octadecenol (molecular weight 268.5, 1.26 mol) was added dropwise, and the addition was completed within 1 hour. The first reaction was carried out for 2 hours to obtain a first mixture; the first mixture included unreacted diisocyanate and an intermediate product, and the intermediate product contained only one NCO group;

[0077] When the mass percentage of the NCO group in the first mixture is 20%, 2 g of MPPO is added to the three-necked flask, the temperature is raised to 160° C., the pressure is 1000 Pa, and the condensation reaction is carried out for 24 hours to obtain the second mixture. When the NCO group content in the second mixture is 0, polycarbodiimide is obtained.

[0078] Comparative Example 1

[0079] 1000g HMDI (3.8mol) was added to a 5L three-necked flask equipped with a stirrer, and nitrogen was passed through. 2g MPPO was added and reacted at 160°C for 24h to obtain HMDI oligomer (0.63mol). 164g isooctyl alcohol (1.26mol) was added and reacted for 2h. When the group content in the three-necked flask was 0, polycarbodiimide was obtained.

[0080] Comparative Example 2

[0081] 1000 g of HMDI (3.8 mol, NCO% 32.1%) was added to a 5 L three-necked flask equipped with a stirrer, nitrogen was passed through, the temperature was controlled at 100°C, 189 g of polyethylene glycol (molecular weight 300, 0.63 mol) was added dropwise, the addition was completed in 1 hour, and the first reaction was carried out for 2 hours to obtain a first mixture; the first mixture included unreacted diisocyanate and an intermediate product, and the number average molecular weight of the intermediate product was 824;

[0082] When the mass percentage of the NCO group in the first mixture is 22.5%, 2 g of MPPO is added to the three-necked flask, the temperature is raised to 160° C., the pressure is 1000 Pa, and the condensation reaction is carried out for 23 hours to obtain the second mixture. When the NCO group content in the second mixture is 0, polycarbodiimide is obtained.

[0083] Effect Example 1

[0084] The polycarbodiimide prepared in Examples 1-6 and Comparative Examples 1-2 was subjected to the following tests:

[0085] 1. PDI and number average molecular weight test: GPC was used for testing. The model of GPC was Agilent 1260. The test conditions were: chromatographic column Agilent PL aquagel-OH MIXED-M 8um (300 x 7.8 mm), mobile phase: tetrahydrofuran (THF), flow rate: 1 mL / min, column temperature: 40°C.

[0086] 2. Viscosity test: The instrument used is Brookfield online viscometer, model AST-100.

[0087] 3. Softening point test: The instrument used is Mettler Toledo, model DSC 3, and the test conditions are RT ~ 120 ° C, heating rate 10 ° C / min, and nitrogen atmosphere.

[0088] 4. Thermal decomposition temperature test: The instrument used is Mettler Toledo, model TGA 2 (SF), and the test conditions are RT ~ 600 ° C, heating rate 10 ° C / min, and nitrogen atmosphere.

[0089] The above test results are listed in Table 1:

[0090] Table 1

[0091] Number average molecular weight Maximum viscosity / mpa.s PDI Softening point / ℃ Thermal decomposition temperature / ℃ Example 1 1612 8750 1.26 61 267 Example 2 1630 9805 1.31 57 255 Example 3 2702 24104 1.65 83 334 Example 4 1753 7658 1.21 54 253 Example 5 1472 11930 1.36 72 295 Example 6 1889 5733 1.15 50 246 Comparative Example 1 1662 21992 1.78 55 250 Comparative Example 2 2064 36995 2.01 29 245

[0092] The number average molecular weight of the polycarbodiimide prepared in Example 1-6 is above 1400; when the number average molecular weight of the polycarbodiimide is 2702, the maximum viscosity during the preparation process does not exceed 24104 mpa.s, and when the number average molecular weight of the polycarbodiimide is 1400-1900, the maximum viscosity during the preparation process does not exceed 11930 mpa.s, indicating that the viscosity of the process system of the present invention is low, which is conducive to industrial amplification. The molecular weight distribution PDI of the polycarbodiimide prepared in Example 1-6 is below 1.65, and the smaller the PDI, the narrower the molecular weight distribution. The softening point of the polycarbodiimide prepared in Example 1-6 is above 50°C, and the thermal decomposition temperature is above 246°C.

[0093] Compared with the examples of the present application, the number average molecular weight of Comparative Example 1 is close to that of Examples 1-2 and Examples 4-6, but the maximum viscosity during its preparation process is 21992 mpa.s, and the PDI is 1.78, both of which are greater than those of Examples 1-2 and Examples 4-6.

[0094] Comparative Example 2 uses polyethylene glycol containing two active hydrogen atoms, so that the maximum viscosity and PDI in the preparation process far exceed those of the embodiments of the present invention, and the softening point is only 29°C.

Claims

1. A method for preparing polycarbodiimide, characterized in that: It includes the following steps: S1. Performing a first reaction on a first raw material and a second raw material to obtain a first mixture; the first raw material includes a diisocyanate, and the second raw material includes a monohydric alcohol and / or a monoamine; the first mixture includes an intermediate product, and the intermediate product contains only one NCO group; the mass percentage of the NCO group in the first mixture accounts for 20%-30% of the mass percentage of the first mixture; S2. Adding a second catalyst to the first mixture, and subjecting the intermediate product to a condensation reaction with diisocyanate to obtain polycarbodiimide.

2. The method for preparing polycarbodiimide according to claim 1, characterized in that: The monohydric alcohol is one or more of methanol, ethanol, n-propanol, isobutanol, tert-butanol, isooctyl alcohol, tridecanol, isopropanol and octadecenol; and / or, the monoamine is, for example, one or more of methylamine, ethylamine, n-propylamine, isopropylamine, n-butylamine, tert-butylamine, cyclohexylamine and benzylamine; And / or, the molecular weight of the second raw material is less than 300 g / mol, preferably 60-270 g / mol, for example 130 g / mol, 200 g / mol or 268.5 g / mol.

3. The method for preparing polycarbodiimide according to claim 1, characterized in that: The diisocyanate is an aliphatic diisocyanate and / or an aromatic diisocyanate; Wherein, the aliphatic diisocyanate is, for example, one or more of hexamethylene diisocyanate, isophorone diisocyanate and dicyclohexylmethane diisocyanate; The aromatic diisocyanate is, for example, one or more of toluene diisocyanate, diphenylmethane diisocyanate, p-phenylene diisocyanate, naphthalene diisocyanate, xylylene diisocyanate, dimethylene diphenylmethane diisocyanate and tetramethylxylylene diisocyanate.

4. The method for preparing polycarbodiimide according to claim 1, characterized in that: The molar percentage of the second raw material to the first raw material is 5%-40%, preferably 5%-33%, and further preferably 5%-20%, for example 17% or 18%; And / or, the mixing step is: adding the second raw material to the first raw material; Wherein, the adding is one-time adding or dropwise adding, preferably dropwise adding; The dropping time is 0.5-3h, for example, 1h.

5. The method for preparing polycarbodiimide according to claim 1, characterized in that: The temperature of the first reaction is 30-120°C, preferably 50-100°C; And / or, the first reaction is carried out under an atmosphere of an inert gas, such as nitrogen, argon, helium or neon, preferably nitrogen; And / or, the first reaction time is 1-5 h, for example, 1 h or 2 h.

6. The method for preparing polycarbodiimide according to claim 1, characterized in that: The mass percentage of the NCO groups in the first mixture is 20%-27% of the mass of the first mixture, for example, 21.3%, 22.80%, 24.8% or 26.6%.

7. The method for preparing polycarbodiimide according to claim 1, characterized in that: The mass percentage of the second catalyst to the first raw material is 0.02%-2%, for example, 0.2%; and / or, the second catalyst is an organophosphorus compound; Wherein, the organic phosphorus compound is, for example, one or more of 3-methyl-1-phenyl-2-phospholene-1-oxide, 1-ethyl-2-phospholene-1-oxide and 1-methyl-3-chloro-2-phospholene-1-oxide; and / or, the condensation reaction is carried out under an atmosphere of an inert gas, such as nitrogen, argon, helium or neon, preferably nitrogen; And / or, the condensation reaction temperature is 50-220°C, preferably 120-200°C, for example 160°C; And / or, the pressure of the condensation reaction is 200-101325Pa, for example, 1000Pa.

8. The method for preparing polycarbodiimide according to claim 1, characterized in that: The method further comprises the following steps after the condensation reaction: forming a second mixture after the condensation reaction, wherein the mass percentage of the NCO groups in the second mixture is 1%-3% of the mass percentage of the second mixture; adding a third raw material to the second mixture for a second reaction, wherein the third raw material comprises a monohydric alcohol and / or a monoamine; Wherein, the monohydric alcohol is, for example, one or more of methanol, ethanol, n-propanol, isobutanol, tert-butanol, isooctyl alcohol, tridecanol, isopropanol and octadecenol; Wherein, the monoamine is, for example, one or more of methylamine, ethylamine, n-propylamine, isopropylamine, n-butylamine, tert-butylamine, cyclohexylamine and benzylamine; Preferably, the mass percentage of the NCO groups in the second mixture formed after the condensation reaction is 2.8% of the mass percentage of the second mixture; Wherein, the temperature of the second reaction is preferably 30-120°C, more preferably 50-100°C; Preferably, the second reaction is carried out under an atmosphere of an inert gas, such as nitrogen, argon, helium or neon, preferably nitrogen; Preferably, the second reaction time is 1-5 h, for example, 1 h or 2 h.

9. A polycarbodiimide obtained by the method for preparing a polycarbodiimide according to any one of claims 1 to 8.

10. The polycarbodiimide according to claim 9, characterized in that The number average molecular weight of the polycarbodiimide is greater than 1400, for example, greater than 2700; and / or, the PDI of the polycarbodiimide is less than 1.65, for example, 1.15, 1.21, 1.26, 1.31, 1.36 or 1.65; and / or the softening point of the polycarbodiimide is above 50° C., for example, 50° C., 54° C., 57° C., 61° C., 72° C. or 83° C.; And / or, the thermal decomposition temperature of the polycarbodiimide is above 246°C, for example, 246°C, 253°C, 255°C, 267°C, 295°C or 334°C.