A dispersant based on polycarbodiimide skeleton structure and preparation method thereof

Abstract

The present invention discloses a dispersant based on a polycarbodiimide skeleton structure, which is characterized by being shown in the following structural formula 3. The present invention also discloses a preparation method thereof. The present invention provides a synthetic skeleton of a novel high molecular polymer dispersant, and the skeleton structure has the characteristics of multiple reaction sites, high reactivity, and easy structural adjustment. It is particularly suitable for products such as dispersants that require functionalization balance control in polymer molecules. The method of the present technical solution can be used to easily design and synthesize dispersants that are adapted to different systems, such as water-based dispersants, solvent-based dispersants, etc. The raw materials of the present technical solution are easily available, the process is simple, the cost is controllable, and it is suitable for industrial production.

Description

Technical Field

[0001] The invention relates to the field of dispersant preparation, and in particular to a dispersant based on a polycarbodiimide skeleton structure and a preparation method thereof. Background Art

[0002] Dispersants are chemicals that can disperse fine particles in the medium and form stable finely dispersed suspensions. Their function is to reduce the adhesion between particles or droplets to prevent flocculation or enrichment.

[0003] Dispersants are also called wetting dispersants. Their main function is to wet and disperse pigments and fillers in the base material. After the irregular particle surface is fully wetted by the medium during the dispersion process, the dispersant is adsorbed on the particle surface and keeps the particles in a dispersed state. In order to maintain the stability of this dispersed state, there are usually two ways.

[0004] One is that the dispersant makes the surface of the particles carry the same charge, and the electrostatic repulsion between the particles makes it difficult for the particles to re-aggregate. Another mechanism is the steric hindrance effect. The large steric hindrance groups contained in the dispersant molecules wrap around the particles to form a barrier layer that hinders the particles from approaching and agglomerating each other, avoiding the formation of agglomerates and floccules, and stabilizing the dispersion system. Based on the above mechanism, dispersants are usually composed of anchoring groups that have a strong adsorption effect on pigments and fillers and solvated chains with steric hindrance effects. Common anchoring groups include -NR2, -COOH, -COO-, -CONH-, -SO3H, -PO4-2, -OH, -SH, polyamines, polyols, etc. They can have a strong affinity with the surface of pigments and fillers, thus having excellent surface adsorption capacity.

[0005] In addition, some aromatic groups are also considered to be a very effective anchoring group because of their strong intermolecular forces with the conjugated groups in the organic pigment structure. The structure of the solvated chain is usually closely related to the dispersant use system. Its excellent solubility in the dispersion medium improves the system compatibility of the dispersant on the one hand, and on the other hand, it expands the steric hindrance on the particle surface and improves the stability of the dispersion system. Therefore, dispersants containing hydrophilic chain segments show better application effects in aqueous systems, among which commonly used structures include polyethylene glycol and alkyl polyoxyethylene ether; while dispersants containing lipophilic solvated chains are more suitable for oily systems, and common structures include long-chain alkanes and oil-soluble polyesters.

[0006] The balance between anchoring groups and solvated chains in dispersants has an important influence on the system compatibility and stability of the dispersants.

[0007] Dispersants can be divided into inorganic dispersants and organic dispersants based on their chemical structure. The main types of inorganic dispersants include polyphosphates, silicates, sulfonates, etc. Organic dispersants are further divided into two categories: small organic molecules and high molecular polymers. Small organic molecule dispersants include alkyl sulfates, alkyl sulfonates, alkyl aryl sulfonates, alkyl succinates, etc.

[0008] Inorganic and organic small molecule dispersants have a certain dispersing and stabilizing effect on dispersed particles in the dispersion medium, but because they have few anchoring groups and weak binding force on dispersed particles, their adsorption on the particle surface is not strong enough, so they are easily desorbed from the particle surface and lose their dispersing and stabilizing effect.

[0009] Moreover, the structure of metal salts is more easily affected by other ions in the system, which greatly limits their scope of application.

[0010] In recent years, polymer dispersants have developed into a new generation of high-efficiency dispersants, which have greatly enhanced and improved the wettability, dispersion stability and applicability of pigments.

[0011] The polymer dispersants that have been widely used in the market mainly include two categories: polycarboxylic acid and polyurethane. Among them, polycarboxylic acid dispersants are mainly prepared by copolymerization of various acrylate monomers and functional monomers such as acrylic acid, methacrylic acid or maleic anhydride. They have the advantages of simple preparation process, low cost, and good dispersing effect on inorganic pigments.

[0012] Correspondingly, polycarboxylic acid dispersants also have a relatively single anchoring group and a wide molecular weight distribution due to the small number of monomer types and difficulty in controlling molecular weight during the synthesis process, which in turn affects the dispersion stability performance.

[0013] In the production and application of polyurethane polymer dispersants, although the adjustment range of its functional groups has been greatly improved compared with the polyacrylate type structure, due to the extremely high anhydrous condition control during its synthesis process and the difficulty in controlling the degree of polymerization, the production reproducibility of this type of dispersant is poor, which greatly limits its production and application range. Summary of the invention

[0014] In order to overcome the above-mentioned defects of the prior art, the object of the present invention is to provide a dispersant based on a polycarbodiimide skeleton structure and a preparation method thereof.

[0015] The dispersant of the present invention has a main chain of a polycarbodiimide structure and has a diversified selection of end-capping groups and grafting groups, and improves the dispersing performance of polymer molecules by adjusting the balance between the anchoring group and the solvation chain in the dispersant structure.

[0016] In order to achieve the purpose of the present invention, the technical solution adopted is:

[0017] A dispersant based on a polycarbodiimide skeleton structure, as shown in the following structural formula 3:

[0018]

[0019] Formula 3;

[0020] The polycarbodiimide skeleton structure is shown in the following structural formula 2:

[0021]

[0022] Formula 2.

[0023] The polycarbodiimide skeleton structure of the present invention can be derivatized from multiple sites on the molecular structure. R1 and R2 are repeating units located in the polymer, which can be used to adjust the rigidity, flexibility and steric hindrance of the skeleton. The carbodiimide group can easily realize the grafting reaction of the skeleton, and the R3 end group can be used to adjust the system compatibility of the target dispersant. Through the derivatization of these sites, the balance of the anchoring group and the solvation chain in the dispersant structure can be obtained to adapt to the application of different dispersion systems.

[0024] In a preferred embodiment of the present invention, the structure shown in the structural formula 3 is prepared by the following reaction formula 1:

[0025]

[0026] Reaction formula 1;

[0027] In a preferred embodiment of the present invention, R1 is a structure described in any one of the following structural formulas 4 and 5:

[0028]

[0029] Formula 4;

[0030]

[0031] Formula 5;

[0032] In a preferred embodiment of the present invention, R2 is a structure described in any one of the following structural formulas 6 and 7:

[0033]

[0034] Formula 6;

[0035]

[0036] Formula 7;

[0037] In a preferred embodiment of the present invention, R3 is a structure described in any one of the following structural formulas 8, 9 and 10:

[0038]

[0039] Formula 8;

[0040]

[0041] Formula 9;

[0042]

[0043] Formula 10;

[0044] In a preferred embodiment of the present invention, the R4 is a structure as described in Formula 11 below:

[0045]

[0046] Formula 11;

[0047] In a preferred embodiment of the present invention, the R5 is a structure as described in Formula 12 below:

[0048]

[0049] Formula 12.

[0050] In a preferred embodiment of the present invention, the degree of polymerization n of the structural formula 3 is an integer, preferably n=6-8.

[0051] In a preferred embodiment of the present invention, the degree of polymerization n of the structural formula 3 is not an integer or is an integer when the average value is calculated.

[0052] In a preferred embodiment of the present invention, the molecular weight of the dispersant is in the range of 2000-50000, preferably 8000-20000.

[0053] A method for preparing a dispersant based on a polycarbodiimide skeleton structure, the preparation method comprising the following steps:

[0054] The first step, polycondensation reaction:

[0055] Add an organic diisocyanate or solvent A to a reaction vessel, add an organic phosphorus catalyst, raise the temperature to 120-200° C., and react to a desired target degree of polymerization to obtain a polycarbodiimide molecular intermediate as shown in structural formula 1;

[0056] The second step is the end-capping reaction:

[0057] The intermediate obtained by the first step reaction is adjusted to a temperature of 60-160° C., a blocking agent is added, and the temperature is maintained to react until the isocyanate groups react completely to obtain a blocked polycarbodiimide main chain intermediate as shown in structural formula 2;

[0058] The third step, grafting reaction:

[0059] The temperature of the second reaction intermediate is adjusted to 40-120° C., a selected grafting compound for modifying the main chain is added, and the reaction is carried out until the carbodiimide group reacts completely, the reaction is terminated, and solvent B is added to adjust the dispersant solid content to the target result to obtain the target dispersant.

[0060] In a preferred embodiment of the present invention, the solvent A is a high-boiling aprotic solvent. Preferably, xylene, butyl acetate, cyclohexanone, methylcyclohexanone, etc. are used for non-water-soluble systems; any one or more of diethylene glycol dimethyl ether, diethylene glycol diethyl ether, dipropylene glycol dimethyl ether, dipropylene glycol diethyl ether, N-methylpyrrolidone, N-ethylpyrrolidone, N,N-dimethylformamide or N,N-dimethylacetamide.

[0061] In a preferred embodiment of the present invention, the mass ratio of the organic diisocyanate to the solvent A is 0.2-2:1, preferably 0.5-1:1.

[0062] In a preferred embodiment of the present invention, the organic diisocyanate is any one or more of aromatic diisocyanate, aliphatic diisocyanate, alicyclic diisocyanate or heterocyclic diisocyanate.

[0063] Preferred are any one or more of 1,5-naphthalene diisocyanate, 4,4'-diphenylmethane isocyanate, 4,4'-diphenyldimethylmethane isocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, hexamethylene isocyanate, cyclohexane-1,4-diisocyanate, xylene diisocyanate, isophorone diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, methylcyclohexane diisocyanate or tetramethylxylene diisocyanate.

[0064] More preferably, it is any one or more of dicyclohexylmethane-4,4'-diisocyanate, hexamethylene diisocyanate, and tetramethylxylene diisocyanate.

[0065] In a preferred embodiment of the present invention, the organophosphorus catalyst is a heterocyclic high steric hindrance organophosphorus reagent. Preferably, any one or more of 1-phenyl-2-phospholine-1-oxide, 3-methyl-1-phenyl-2-phospholine-1-oxide, 1-ethyl-2-phospholine-1-oxide, and 3-methyl-2-phospholine-1-oxide are selected. More preferably, 3-methyl-1-phenyl-2-phospholine-1-oxide is selected.

[0066] In a preferred embodiment of the present invention, the amount of the organophosphorus catalyst is 0.5%-5% by mass based on diisocyanate, preferably 2%.

[0067] In a preferred embodiment of the present invention, the reaction temperature of the polycondensation reaction is 140-160°C.

[0068] In a preferred embodiment of the present invention, the reaction time of the polycondensation reaction is 4-72 hours, preferably 8-16 hours.

[0069] In a preferred embodiment of the present invention, the target degree of polymerization is 5-20, which is obtained by instrumental analysis and measurement.

[0070] In a preferred embodiment of the present invention, the blocking agent is any one or more of monoalcohol, monoamine or monoisocyanate.

[0071] The monohydric alcohol is preferably any one or more of an aliphatic hydrocarbon monohydric alcohol having 1 to 18 carbon atoms, an alicyclic hydrocarbon monohydric alcohol, an aromatic hydrocarbon monohydric alcohol, a tertiary amine-substituted hydrocarbon monohydric alcohol, a monosubstituted polyoxyethylene ether-based monohydric alcohol, a monosubstituted polyoxypropylene ether-based monohydric alcohol, a monosubstituted mixed polyether-based monohydric alcohol or a polyester-based monohydric alcohol.

[0072] Monohydric alcohol polyethylene glycol monomethyl ether is further preferred, and the corresponding R3 is shown in structural formula 8.

[0073] The monoamine is preferably any one or more of an aliphatic hydrocarbon monoamine having 1 to 18 carbon atoms, an alicyclic hydrocarbon monoamine, an aromatic hydrocarbon monoamine, a tertiary amine-substituted hydrocarbon monoamine, a monosubstituted polyoxyethylene ether monoamine, a monosubstituted polyoxypropylene ether monoamine or a monosubstituted mixed polyether monoamine.

[0074] The monoamine n-octadecylamine is further preferred, and the corresponding R3 is shown in Structural Formula 9.

[0075] The monoisocyanate is any one or more of aliphatic hydrocarbon monoisocyanate, alicyclic hydrocarbon monoisocyanate or aromatic monoisocyanate.

[0076] Cyclohexyl isocyanate is further preferred, and the corresponding R3 is shown in structural formula 10.

[0077] The introduction of end-capping groups in the end-capping agent can help improve the stability of the polymer and the compatibility of the system. Hydrophilic end-capping groups are beneficial to improving the compatibility of aqueous systems, while lipophilic end-capping groups are beneficial to improving the compatibility of oily systems.

[0078] In a preferred embodiment of the present invention, when the end-capping agent is a monoalcohol or a monoamine, the end-capping reaction temperature is 60-120°C;

[0079] When the blocking agent is monoisocyanate, the blocking reaction temperature is 140-160°C.

[0080] In a preferred embodiment of the present invention, the end-capping reaction time is 1-4 hours.

[0081] In a preferred embodiment of the present invention, the molar ratio of the end-capping agent to the polycarbodiimide molecular intermediate as shown in Structural Formula 1 is 2:1-2.2:1.

[0082] In a preferred embodiment of the present invention, the end point of the blocking reaction is when the isocyanate group content in the system is 0, as measured by an analytical instrument.

[0083] In a preferred embodiment of the present invention, the reaction temperature of the grafting reaction is 80-100°C.

[0084] In a preferred embodiment of the present invention, the reaction time of the grafting reaction is 1-4 hours.

[0085] In a preferred embodiment of the present invention, the molar ratio of the grafted compound used to modify the main chain to the end-capped polycarbodiimide main chain intermediate as shown in Structural Formula 2 is 1-1.2:1.

[0086] The grafted compound used to modify the main chain is one or more compounds, and when multiple compounds are selected, the sum of the compounds is 100%.

[0087] In a preferred embodiment of the present invention, the grafted compound used to modify the main chain is any one of a grafted compound containing a carboxyl group or a grafted compound containing an amine group, or a mixture of the two.

[0088] When used in combination, the grafted compound containing an amine group is first added to react, and then the grafted compound containing a carboxyl group is added to react.

[0089] In a preferred embodiment of the present invention, the grafting compound used to modify the main chain is a grafting reaction compound containing a group of the structural formula R4 and a grafting reaction compound containing a group of R5.

[0090] The grafting reaction compound containing the group of the structural formula R4 is preferably any one or more of aliphatic hydrocarbon monocarboxylic acid, alicyclic hydrocarbon monocarboxylic acid or aromatic hydrocarbon monocarboxylic acid having 1 to 18 carbon atoms.

[0091] Oleic acid is further preferred.

[0092] The grafting reaction compound containing the R5 group is preferably any one or more of an aliphatic hydrocarbon monoamine having 1 to 18 carbon atoms, an alicyclic hydrocarbon monoamine, an aromatic hydrocarbon monoamine, a tertiary amine-substituted hydrocarbon monoamine, a monosubstituted polyoxyethylene ether monoamine, a monosubstituted polyoxypropylene ether monoamine or a monosubstituted mixed polyether monoamine.

[0093] Dimethylaminopropylamine is further preferred.

[0094] In a preferred embodiment of the present invention, the reaction end point of the grafting reaction is when the content of carbodiimide groups in the system is 0, as measured by an analytical instrument.

[0095] In a preferred embodiment of the present invention, the solvent B is the same as the solvent A or is water.

[0096] In a preferred embodiment of the present invention, the solid content of the dispersant product is 20-100%, preferably 50-80%.

[0097] The three synthesis steps of the present invention can be carried out separately and step by step as required, or the preparation of the dispersant can be completed efficiently in one pot.

[0098] The beneficial effects of the present invention are:

[0099] The present invention provides a novel synthetic skeleton of a high molecular weight polymer dispersant, which has the characteristics of multiple reaction sites, high reactivity, and easy structural adjustment. It is particularly suitable for products such as dispersants that require functionalization balance control in polymer molecules. The method of the technical solution can be used to easily design and synthesize dispersants adapted to different systems, such as water-based dispersants, solvent-based dispersants, etc. The raw materials of the technical solution are easily available, the process is simple, the cost is controllable, and it is suitable for industrial production. DETAILED DESCRIPTION

[0100] The present invention is further described below by way of examples, wherein Examples 1 to 8 respectively introduce methods for preparing aqueous dispersants using the present technical solution. Example 9 introduces a method for preparing solvent-based dispersants using the present technical solution.

[0101] Embodiment 1 (aqueous dispersant, solution without solvent A)

[0102] 100g of dicyclohexylmethane-4,4'-diisocyanate (HMDI) and 2g of an organic phosphorus catalyst (3-methyl-1-phenyl-2-phosphocyclopentene-1-oxide) were added to a reaction bottle with a stirrer, and the temperature was raised to 160 degrees under nitrogen protection and stirred for 8 hours to obtain dicyclohexylmethane polycarbodiimide with an isocyanate group at the end. The NCO% was measured to be 4.2% and the degree of polymerization n=8.

[0103] The system was cooled to 120 degrees, 30 g of polyethylene glycol monomethyl ether (molecular weight 350, hereinafter referred to as MPEG350) was added, and the reaction temperature was maintained at 120 degrees. After reacting for 4 hours, the isocyanate absorption peak at a wavelength of 2200-2300 detected by infrared spectroscopy (IR) disappeared to obtain polyether-terminated dicyclohexylmethane polycarbodiimide.

[0104] The system was cooled to 80 degrees, 68g of methoxy-terminated mixed polyether unit amine (molecular weight 1000, hereinafter referred to as M1000) and 24g of N,N-dimethylethylenediamine were added, and the reaction temperature was maintained at 80 degrees. After reacting for 2 hours, the grafted product was obtained after the absorption peak of the carbodiimide group disappeared near the infrared spectrum (IR) detection wavelength of 2150. After adding 138g of deionized water for dilution, a yellow transparent liquid target dispersant with a solid content of 60% was obtained.

[0105] Example 2-8 (aqueous dispersant)

[0106] According to the method of Example 1, the types and amounts of the starting material organic diisocyanate, the blocking agent, and the grafting compound were adjusted respectively, and the other experimental conditions were the same as those of Example 1. The obtained dispersant is described in Table 1.

[0107] HDI refers to hexamethylene diisocyanate; MPEG400, MPEG550, and MPEG750 refer to polyethylene glycol monomethyl ether with molecular weights of 400, 550, and 750, respectively;

[0108] M600 and M2000 refer to methoxy-terminated mixed polyether unit amines with molecular weights of 600 and 2000, respectively.

[0109] Table 1

[0110]

[0111] Example 9 (Solvent-based dispersant, solution with solvent A)

[0112] 100g of dicyclohexylmethane-4,4'-diisocyanate (HMDI), 100g of N-methylpyrrolidone and 2g of an organophosphorus catalyst (3-methyl-1-phenyl-2-phosphocyclopentene-1-oxide) were added to a reaction bottle with a stirrer, and the temperature was raised to 160 degrees under nitrogen protection and stirred for 16 hours to obtain dicyclohexylmethane polycarbodiimide with an isocyanate group at the end. The NCO% was measured to be 4.2% and the degree of polymerization n=8.

[0113] The system was cooled to 120 degrees, 47 g of octadecyl polyoxypropylene ether (molecular weight 550, hereinafter referred to as SPO-5) was added, and the reaction temperature was maintained at 120 degrees. After reacting for 4 hours, the isocyanate absorption peak at a wavelength of 2200 to 2300 detected by infrared spectroscopy (IR) disappeared to obtain dicyclohexylmethane polycarbodiimide terminated with fatty alcohol polyether.

[0114] The system was cooled to 80 degrees, 18 g of n-octadecylamine and 28 g of N,N-dimethylpropylenediamine were added, and the reaction temperature was maintained at 80 degrees for 2 hours. After the absorption peak of the carbodiimide group disappeared at the infrared spectrum (IR) detection wavelength of 2150, a grafted product was obtained. After adding 78 g of N-methylpyrrolidone and diluting, a yellow transparent liquid target dispersant with an effective content of 50% was obtained.

[0115] Embodiment 10-15 (Solvent-type dispersant, solution with solvent A)

[0116] According to the method of Example 9, the types and amounts of the starting raw material organic diisocyanate, the blocking agent, and the grafting compound were adjusted respectively. Except for Example 14, the other experimental conditions were the same as those of Example 9. The obtained dispersant is described in Table 2.

[0117] Wherein HDI refers to hexamethylene diisocyanate;

[0118] SPO-10, SPO-20, and SPO-30 refer to octadecyl alcohol polyoxyethylene ether with molecular weights of 850, 1400, and 2000, respectively;

[0119] M600 refers to methoxy-terminated mixed polyether unit amine with a molecular weight of 600;

[0120] In Example 14, since oleic acid and N,N-dimethylpropylenediamine were used as grafting compounds, N,N-dimethylpropylenediamine was first added during the grafting reaction and reacted for 2 hours, and then oleic acid was added and reacted for 2 hours until the reaction was completed.

[0121] Table 2

[0122]

[0123]

[0124] Example 16

[0125] The water-based color paste formula of different pigments (see Table 3) was selected to evaluate the dispersing performance of the synthesized water-based dispersant. The method is to refer to the formula and use the synthesized dispersant to prepare the corresponding water-based color paste using a grinding and dispersing machine. The dispersing performance of the dispersant was examined by comparing the viscosity, fineness, and heat storage (50 degrees for 7 days) stability of the color paste (Table 4).

[0126] Table 3: Experimental recipes

[0127]

[0128] Table 4: Dispersant properties

[0129]

[0130] From the experimental results in Table 4, it can be seen that the aqueous dispersant synthesized according to the technical solution has a strong dispersing ability for dispersing inorganic pigments, organic pigments, and carbon black in an aqueous system, and has excellent dispersion stability.

[0131] Embodiment 17

[0132] The solvent-based color paste formula of different pigments (Table 5) was selected to evaluate the dispersing performance of the synthesized solvent-based dispersant. The method is to refer to the formula and use the synthesized dispersant to prepare the corresponding solvent-based color paste using a grinding and dispersing machine. The dispersing performance of the dispersant was examined by comparing the viscosity, fineness, and heat storage (50 degrees for 7 days) stability of the color paste (Table 6).

[0133] Table 5: Experimental formula

[0134]

[0135] Table 6: Dispersant properties

[0136]

[0137] From the experimental results in Table 6, it can be seen that the solvent-based dispersant synthesized according to the technical solution can obtain good dispersion effects on inorganic pigments, organic pigments, and carbon black in the solvent-based system, and has excellent dispersion stability.

[0138] Embodiment 18

[0139] The water-based color paste formula of different pigments (see Table 7) was selected to compare and evaluate the performance of the synthesized water-based dispersant with the commercially available dispersant products. The method is to refer to the formula and use the synthesized dispersant to prepare the corresponding water-based color paste using a grinding and dispersing machine. The dispersing performance of the dispersant was examined by comparing the viscosity, fineness, and heat storage (50 degrees for 7 days) stability of the color paste (Table 8).

[0140] Table 7: Experimental formula

[0141]

[0142] Table 8: Dispersant properties

[0143]

[0144]

[0145] From the experimental results in Table 8, it can be seen that the aqueous dispersant synthesized according to the present technical solution shows better performance in terms of viscosity and thermal storage stability of dispersed pigment paste compared to commercially available products.

[0146] Embodiment 19

[0147] The solvent-based color paste formulas of different pigments (Table 9) were selected to compare and evaluate the solvent-based dispersants with better performance that have been synthesized and the commercially available solvent-based dispersants. The method is to refer to the formula and use the synthesized dispersants to prepare the corresponding solvent-based color pastes using a grinding and dispersing machine. The dispersing performance of the dispersants was examined by comparing the viscosity, fineness, and heat storage (50 degrees for 7 days) stability of the color pastes (Table 10).

[0148] Table 9: Experimental formula

[0149]

[0150] Table 10: Dispersant properties

[0151]

[0152]

[0153] From the experimental results in Table 10, it can be seen that the solvent-based dispersant synthesized according to the present technical solution exhibits better performance in terms of color paste viscosity reduction efficiency and thermal storage stability than commercially available solvent-based dispersants.

[0154] The above describes the preferred specific embodiments of the present invention, describes in detail the design ideas and implementation methods of the present invention, and further verifies the versatility and effectiveness of the present invention. Therefore, any technical solution that can be obtained by a person skilled in the art based on the concept of the present invention through logical analysis, reasoning or limited experiments on the basis of the prior art should be within the scope of protection determined by the claims.

Claims

1. A dispersant based on a polycarbodiimide skeleton structure, characterized in that: As shown in the following structural formula 3: The polycarbodiimide skeleton structure is shown in the following structural formula 2: The degree of polymerization n is an integer; or the degree of polymerization n is not an integer or is an integer when the average value is calculated; The R1 is a structure described in any one of the following structural formulas 4 and 5: The R2 is a structure described in any one of the following structural formulas 6 and 7: The R3 is a structure described in the following structural formula 8: The R4 is a structure as described in Formula 11 below: The R5 is a structure as described in Formula 12 below:

2. A dispersant based on a polycarbodiimide skeleton structure as claimed in claim 1, characterized in that: The structure shown in the structural formula 3 is prepared by the following reaction formula 1: Reaction formula 1; The degree of polymerization n of the structural formula 3 is an integer; Or the degree of polymerization n of the structural formula 3 is not an integer or is an integer when the average value is calculated.

3. A dispersant based on a polycarbodiimide skeleton structure as claimed in claim 1, characterized in that: The molecular weight of the dispersant is in the range of 8000-20000.

4. The method for preparing a dispersant based on a polycarbodiimide skeleton structure according to claim 2, characterized in that: The preparation method comprises the following steps: The first step, polycondensation reaction: Adding an organic diisocyanate or adding an organic diisocyanate and a solvent A to a reaction container, adding an organic phosphorus catalyst, heating to 140-160° C. and reacting to a desired target degree of polymerization to obtain a polycarbodiimide molecular intermediate as shown in structural formula 1; The reaction time of the polycondensation reaction is 4-72 hours; The target degree of polymerization is 5-20; The solvent A is a high boiling point aprotic solvent; The mass ratio of the organic diisocyanate to the solvent A is 0.2-2:1; The organic diisocyanate is any one or more of aromatic diisocyanate, aliphatic diisocyanate, alicyclic diisocyanate or heterocyclic diisocyanate; The organophosphorus catalyst is a heterocyclic highly sterically hindered organophosphorus reagent; The amount of the organophosphorus catalyst is 0.5% to 5% by mass based on diisocyanate; The second step is the end-capping reaction: The intermediate obtained by the first step reaction is adjusted to a temperature of 60-160° C., a blocking agent is added, and the temperature is maintained to react until the isocyanate groups react completely to obtain a blocked polycarbodiimide main chain intermediate as shown in structural formula 2; When the end-capping agent is a monohydric alcohol, the end-capping reaction temperature is 60-120°C; The end-capping reaction time is 1-4 hours; The molar ratio of the end-capping agent to the polycarbodiimide molecular intermediate as shown in structural formula 1 is 2:1-2.2:1; The end point of the blocking reaction is when the isocyanate group content in the system is 0; The third step, grafting reaction: The temperature of the intermediate of the second step reaction is adjusted to 40-120° C., and the selected grafting compound for modifying the main chain is added to react until the carbodiimide group reacts completely, and then the reaction is terminated, and solvent B is added to adjust the dispersant solid content to the target result to obtain the target dispersant; The reaction temperature of the grafting reaction is 80-100°C; The reaction time of the grafting reaction is 1-4 hours; The molar ratio of the grafted compound used to modify the main chain to the end-capped polycarbodiimide main chain intermediate as shown in structural formula 2 is 1-1.2:1; The grafting compound used to modify the main chain is a mixture of a grafting reaction compound containing a group of the R4 structural formula and a grafting reaction compound containing a group of the R5 structural formula; The reaction end point of the grafting reaction is when the content of carbodiimide groups in the system is 0; The solvent B is the same as the solvent A or is water; The solid content of the dispersant product is 20-100%.

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