A water-based polycarbodiimide composition and its preparation method and application

Abstract

The present invention relates to an aqueous polycarbodiimide composition and a preparation method and application thereof, belonging to the technical field of aqueous compositions. The aqueous polycarbodiimide composition of the present invention comprises a reaction product of a polycarbodiimide compound (A) and a carboxyl-containing polyether (B); wherein: the polycarbodiimide compound (A) is at least one of the polycarbodiimides that do not contain a hydrophilic group and do not contain an urethane bond structure; the carboxyl-containing polyether (B) is at least one of the compounds shown in formula (1); the content of the polyoxyethylene segment in the carboxyl-containing polyether (B) is 5-25wt% of the total amount of the polycarbodiimide compound (A) and the carboxyl-containing polyether (B). The aqueous polycarbodiimide composition is used in aqueous coatings, and the coating film prepared by the aqueous polycarbodiimide composition has excellent water resistance and alcohol resistance.

Description

Technical Field

[0001] The present invention relates to the technical field of aqueous compositions, and in particular to an aqueous polycarbodiimide composition and a preparation method and application thereof. Background Art

[0002] Water-based coatings can significantly reduce VOC emissions and reduce harm to human health, but compared with traditional solvent-based coatings, water-based coatings have obvious deficiencies in terms of adhesion to substrates, wear resistance, solvent resistance, hydrolysis resistance, etc. Water-based polycarbodiimide compositions can undergo cross-linking reactions with carboxyl groups contained in water-based resins to improve the comprehensive properties of coatings. They are also non-toxic and environmentally friendly, making them an ideal water-based cross-linking agent, and thus have been widely used.

[0003] US5866715A and CN118085303A respectively disclose a carbodiimide composition, which uses a hydrophilic monoalcohol containing an oxyalkylene group and a hydroxyl group to hydrophilically modify and cap a polycarbodiimide containing an isocyanate group at the terminal. Since the isocyanate group is consumed by the amination reaction of the hydroxyl group and the isocyanate group, the content of the carbodiimide group in the composition is reduced, further affecting the crosslinking density.

[0004] CN113490724B discloses an aqueous carbodiimide composition of an external emulsification method, which comprises a hydrophobic polycarbodiimide compound and a water-soluble organic compound, wherein the water-soluble organic compound is a nonionic surfactant. The aqueous polycarbodiimide composition obtained by this method does not contain urethane bonds and has a high content of carbodiimide groups, but due to the addition of nonionic surfactants, these free surfactants will also have an adverse effect on the water resistance and other properties of the coating film.

[0005] CN118085303A discloses an aqueous carbodiimide composition, in which a hydrophobic carbodiimide is modified with a polyacrylic acid resin containing oxyalkylene groups and carboxyl groups. The self-emulsifying aqueous polycarbodiimide composition obtained by this method does not contain urethane bonds, but requires a higher proportion of acrylic acid resin to obtain a stable aqueous dispersion, which also reduces the content of carbodiimide groups in the composition. Summary of the invention

[0006] Based on this, the purpose of the present invention is to overcome the defects or shortcomings of the prior art and provide a water-based polycarbodiimide composition and a preparation method and application thereof. The water-based polycarbodiimide composition has excellent water resistance and alcohol resistance and can be widely used in water-based coatings to improve the performance of water-based coatings.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] A water-based polycarbodiimide composition comprises a reaction product of a polycarbodiimide compound (A) and a carboxyl-containing polyether (B); wherein:

[0009] The polycarbodiimide compound (A) is at least one of polycarbodiimides that do not contain a hydrophilic group and do not contain a urethane bond structure;

[0010] The carboxyl-containing polyether (B) is at least one of the compounds represented by formula (1):

[0011]

[0012] In formula (1), R 1 is a hydrocarbon group having 1 to 8 carbon atoms; R 2 is hydrogen or methyl; X is a divalent aliphatic hydrocarbon group or aromatic hydrocarbon group having 1 to 8 carbon atoms; n is an integer of 6 to 68, and m is 0 or 1;

[0013] The carboxyl-containing polyether (B) The content of (the segment structure is hereinafter referred to as: polyoxyethylene segment) is 5-25wt% of the total amount of the polycarbodiimide compound (A) and the carboxyl-containing polyether (B).

[0014] The water-based polycarbodiimide composition of the present invention has excellent water resistance and alcohol resistance, and can be widely used in water-based coatings as a composition to improve the performance of the water-based coatings.

[0015] The water-based polycarbodiimide composition of the present invention is obtained by reacting the polycarbodiimide compound (A) with the carboxyl-containing polyether (B). The inventors of the present invention have found through repeated studies that the carboxyl group in the carboxyl-containing polyether (B) reacts with the carbodiimide group in the polycarbodiimide compound (A), so that the hydrophilic polyethylene oxide chain segment on the carboxyl-containing polyether (B) is introduced into the polymer side chain of the polycarbodiimide compound (A) through the reaction between the carboxyl group and the carbodiimide group, thereby making the reaction product of the polycarbodiimide compound (A) and the carboxyl-containing polyether (B) have good hydrophilicity, making the water-based polycarbodiimide composition easy to disperse in water.

[0016] The present invention stipulates that in the waterborne polycarbodiimide composition, the content of the polyoxyethylene chain segment in the carboxyl-containing polyether (B) is 5-25wt% of the total amount of the polycarbodiimide compound (A) and the carboxyl-containing polyether (B). If the content of the polyoxyethylene chain segment is too high, the waterborne polycarbodiimide composition will be too hydrophilic, affecting the water resistance and alcohol resistance of the coating film formed after the waterborne polycarbodiimide composition is used in waterborne coatings. If the content of the polyoxyethylene chain segment is too low, the storage stability of the waterborne polycarbodiimide composition will be poor.

[0017] As a preferred solution, the average functional number of the carbodiimide group in the polycarbodiimide compound (A) is 2-20. If the average functional number of the carbodiimide group in the polycarbodiimide compound (A) is too large, its chain segment is too long or the volume is too large, which easily leads to the polycarbodiimide compound (A) having too high viscosity, and the reaction product with the carboxyl-containing polyether (B) also has high viscosity, and it is difficult to emulsify in water. If the average functional number of the carbodiimide group in the polycarbodiimide compound (A) is too small, the reaction product of the polycarbodiimide compound (A) and the carboxyl-containing polyether (B) may not have a carbodiimide group, resulting in the water-based polycarbodiimide composition being used in the process of forming a coating film after being used in a water-based coating. Crosslinking may not be achieved, and a coating film cannot be formed. More preferably, the average functional number of the carbodiimide group in the polycarbodiimide compound (A) is 2-10.

[0018] As a preferred solution, the polycarbodiimide compound (A) is at least one of an aliphatic polycarbodiimide and an aromatic polycarbodiimide. The carbodiimide groups on the aliphatic polycarbodiimide and the aromatic polycarbodiimide can crosslink with the carboxyl group of the carboxyl-containing polyether (B). Taking into account the speed of the crosslinking reaction and the weather resistance of the composition, it is more preferred that the polycarbodiimide compound (A) is an aliphatic polycarbodiimide. The reaction speed of the carbodiimide group on the aliphatic polycarbodiimide crosslinking with the carboxyl group is faster than the reaction speed of the carbodiimide group on the aromatic polycarbodiimide crosslinking with the carboxyl group, and the weather resistance is better than that of the aromatic polycarbodiimide. In addition, the waterborne polycarbodiimide composition obtained by using the aliphatic polycarbodiimide has a faster crosslinking speed as a composition used in waterborne coatings than the waterborne polycarbodiimide composition obtained by using the aromatic polycarbodiimide. Therefore, it is preferable to use an aliphatic polycarbodiimide as the polycarbodiimide compound (A).

[0019] As a preferred solution, the raw material for preparing the polycarbodiimide compound (A) is an aliphatic diisocyanate and / or an aromatic diisocyanate; for example, the aliphatic diisocyanate includes but is not limited to hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), and dicyclohexylmethane diisocyanate (HMDI); the aromatic diisocyanate includes but is not limited to toluene diisocyanate (TDI) and diphenylmethane diisocyanate (MDI). Preferably, the raw material for preparing the polycarbodiimide compound (A) is an aliphatic diisocyanate, so as to facilitate the preparation of aliphatic polycarbodiimide. The above-mentioned raw materials do not represent a limitation on the polycarbodiimide compound (A) of the present invention, and those skilled in the art can select other raw materials to prepare the polycarbodiimide compound (A) according to actual needs.

[0020] The present invention also provides a method for preparing any of the above-mentioned aqueous polycarbodiimide compositions, comprising the following steps: adding the polycarbodiimide compound (A) and the carboxyl-containing polyether (B) into a container, reacting until the acid value is zero, to obtain the aqueous polycarbodiimide composition.

[0021] As a preferred solution, in the reaction of the polycarbodiimide compound (A) and the carboxyl-containing polyether (B), the reaction temperature is 60-130° C. and the reaction time is 2-10 h.

[0022] In some embodiments, in the method for preparing the aqueous polycarbodiimide composition, an organic solvent may also be added to the container. An organic solvent is added to the reaction of the polycarbodiimide compound (A) and the carboxyl-containing polyether (B) to facilitate the reaction. Preferably, the boiling point of the organic solvent is ≥60°C. If the boiling point of the organic solvent is too low, the organic solvent may evaporate seriously. Preferably, the amount of the organic solvent added is 0-10% of the total weight of the aqueous polycarbodiimide composition. If the amount of organic solvent added is too much, it is not environmentally friendly and causes the content of the effective ingredients of the aqueous polycarbodiimide composition to decrease. Preferably, the organic solvent is preferably aromatic hydrocarbons, ketones, alcohol ethers, ethers, esters, etc.

[0023] In other embodiments, in the method for preparing the aqueous polycarbodiimide composition, the organic solvent may not be added. For environmental protection reasons, it is preferred that the organic solvent is not added.

[0024] In some embodiments, in the preparation method of the aqueous polycarbodiimide composition, after the reaction to the acid value of zero, water can be added for emulsification to obtain the aqueous polycarbodiimide composition. After the reaction of the polycarbodiimide compound (A) and the carboxyl-containing polyether (B) is completed, water is added for emulsification to form an aqueous dispersion of the aqueous polycarbodiimide composition, and the amount of water added is 45-75% of the total weight of the aqueous polycarbodiimide composition; if the amount of water added is too little, the viscosity of the aqueous dispersion formed by the aqueous polycarbodiimide composition will be too large; if the amount of water added is too little, the content of effective ingredients in the aqueous dispersion formed by the aqueous polycarbodiimide composition will be low.

[0025] In other embodiments, in the preparation method of the water-based polycarbodiimide composition, after the reaction to the acid value of zero, an external emulsifier can be added first, and then water is added for emulsification to obtain the water-based polycarbodiimide composition. The amount of the external emulsifier added is 0-5% of the total weight of the water-based polycarbodiimide composition; after the reaction of the polycarbodiimide compound (A) and the carboxyl-containing polyether (B) is completed, the external emulsifier is first added, and then water is added for emulsification to improve the emulsification effect, so that the water-based polycarbodiimide composition forms a water dispersion and is effectively dispersed on the surface of the water dispersion. The present invention has no special restrictions on the added external emulsifier, preferably an anionic or non-ionic emulsifier. In order not to affect the water resistance of the coating film, it is preferred not to add an external emulsifier.

[0026] The present invention also provides the use of any of the above-mentioned aqueous polycarbodiimide compositions:

[0027] As an application, the present invention provides a cross-linkable composition, comprising any of the above-mentioned water-based polycarbodiimide compositions and a carboxyl-containing water-based resin.

[0028] As another application, specifically, the use of any of the above-mentioned polycarbodiimide compositions in the preparation of water-based coatings. The water-based coatings include the cross-linkable composition (i.e., any of the above-mentioned water-based polycarbodiimide compositions and a carboxyl-containing water-based resin). During the process of construction and drying to form a coating film, as the water evaporates, the carbodiimide groups in the water-based polycarbodiimide composition will undergo a cross-linking reaction with the carboxyl groups in the carboxyl-containing water-based resin to form a cross-linking network, thereby providing the coating film with better chemical properties.

[0029] As a preferred solution, the water-based coating comprises the following components in parts by weight: 1-8 parts by weight of any of the above-mentioned water-based polycarbodiimide compositions and 70 parts by weight of a carboxyl-containing water-based resin.

[0030] Furthermore, the water-based paint further comprises other additives, and the weight portion of the other additives in the water-based paint is 2-40 parts. By adding other additives, the performance and decorative effect of the water-based paint can be improved. Preferably, the weight portion of the other additives in the water-based paint is 5-25 parts.

[0031] As a preferred solution, the other additives include one or more of a defoamer, a leveling agent, a cosolvent, a color paste or a thickener. The weight portion of the defoamer in the water-based paint is 0.1-1 part; the weight portion of the leveling agent in the water-based paint is 0.1-1 part; the weight portion of the cosolvent in the water-based paint is 1-10 parts; the weight portion of the color paste in the water-based paint is 0.1-20 parts; the weight portion of the thickener in the water-based paint is 0.1-2 parts. The defoamer eliminates the bubbles generated during the stirring process and the bubbles generated during the reaction process; the leveling agent acts on the interface between the water-based paint liquid and the air to improve the flatness of the paint film surface and prevent defects such as Bénard vortices; the cosolvent improves the film-forming properties of the water-based paint, establishes a volatilization gradient of the water-based paint, and improves the surface effect of the coating; the color paste provides the covering power and color effect required for the coating; the thickener adjusts the rheological properties of the water-based paint to improve the coating's anti-sagging, anti-splashing and other properties.

[0032] As a preferred solution, the defoamer is at least one of a polysiloxane defoamer and a mineral oil defoamer; the leveling agent is at least one of a polysiloxane leveling agent and an acrylic leveling agent; the cosolvent is at least one of ethylene glycol butyl ether, propylene glycol butyl ether, diethylene glycol butyl ether, dipropylene glycol methyl ether, and dipropylene glycol butyl ether; the color paste is at least one of an inorganic color paste and an organic color paste, and the thickener is at least one of a polyurethane thickener, an alkali swellable acrylic thickener, and bentonite. The above-mentioned defoamer, leveling agent, cosolvent, and thickener do not represent limitations on the present invention, and those skilled in the art may also select other types of defoamers, leveling agents, cosolvents, color pastes, and thickeners according to actual needs.

[0033] The present invention also provides a method for preparing the water-based paint, comprising the following steps: uniformly mixing the components to obtain the water-based paint.

[0034] As another application, the present invention provides a product coated with the water-based coating, which is formed by spraying the water-based coating including the water-based polycarbodiimide composition on the surface of a substrate.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] The water-based polycarbodiimide composition of the present invention can be applied to water-based coatings, and the coating film formed by the water-based coatings has very good water resistance and alcohol resistance.

[0037] The waterborne polycarbodiimide composition of the present invention is a self-emulsifying waterborne polycarbodiimide composition with a high carbodiimide group content. The present invention obtains the waterborne polycarbodiimide composition by reacting the polycarbodiimide compound (A) with the carboxyl-containing polyether (B), so that the hydrophilic polyoxyalkylene chain segment is introduced into the side chain of the polycarbodiimide polymer (A) through the carboxyl-containing polyether (B). We surprisingly found that this type of polycarbodiimide with a side chain hydrophilic polyether structure is very easy to disperse in water, and only a small amount of polyoxyethylene chain segments are required to achieve polymer stability. The prepared waterborne polycarbodiimide composition has a high carbodiimide content, and the coating film has excellent water resistance and alcohol resistance. DETAILED DESCRIPTION

[0038] The present invention is further described below in conjunction with examples. These examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention. The experimental methods in the following examples that do not specify specific conditions are usually carried out according to conventional conditions in the art or according to the conditions recommended by the manufacturer; the raw materials, reagents, etc. used, unless otherwise specified, are all raw materials and reagents that can be obtained from commercial channels such as conventional markets. Any non-substantial changes and substitutions made by those skilled in the art on the basis of the present invention belong to the scope of protection claimed by the present invention.

[0039] Example 1

[0040] This embodiment provides an aqueous polycarbodiimide composition C1, which is obtained by reacting a polycarbodiimide compound A1 and a carboxyl-containing polyether B1.

[0041] The aqueous polycarbodiimide composition C1 of this embodiment is prepared by the following process:

[0042] (1) Preparation of polycarbodiimide compound A1:

[0043] The reaction flask was filled with nitrogen, and 1049.4 g of dicyclohexylmethane diisocyanate, 198.3 g of butyl isocyanate, and 12.6 g of 1-methylphosphine-1-oxide (MPO) were added. The mixture was heated to 160° C. and reacted until the NCO value reached zero, thereby obtaining polycarbodiimide compound A1.

[0044] The theoretical average functional number of the carbodiimide group in the polycarbodiimide compound A1 is 5.

[0045] (2) Preparation of carboxyl-containing polyether B1:

[0046] The reaction flask was purged with nitrogen, and 187.5 g of Clariant M750 (polyethylene glycol monomethyl ether, 750 molecular weight), 39.0 g of 2,2,6,6-tetramethylpiperidinoxide (TEMPO, Aladdin Chemical Reagent), and 500.0 g of dichloromethane were added, and heated to reflux, and dry air was introduced. 15.6 g of concentrated nitric acid was added, and the addition was completed within 15 minutes, and then the mixture was heated to reflux for 17 hours. Then 250.0 g of isopropanol was added and stirred for 1 hour. The volatile components were vacuumed to obtain 180.2 g of product, and the acid value was tested to be 72 mgKOH / g, and the carboxyl equivalent was calculated to be about 780.

[0047] Among them, the carboxyl-containing polyether B1 satisfies the general formula (1), and R 1 is methyl, R 2 is hydrogen, X is methylene, the average value of n is 15.3, and m is 0.

[0048] (3) Preparation of water-based polycarbodiimide composition C1:

[0049] The reaction flask was filled with nitrogen, and 100.0 g of polycarbodiimide compound A1 (containing 0.481 mol of carbodiimide groups) and 19.7 g of carboxyl-containing polyether B1 (containing 0.0253 mol of carboxyl groups) were added, and heated to 120°C for 2 h. At this time, the acid value was zero. 146.3 g of deionized water was added under high-speed stirring to obtain a milky liquid, i.e., an aqueous polycarbodiimide composition C1, which had a solid content of 45% and a carbodiimide group equivalent (based on solids) of 263.

[0050] The content of the polyethylene oxide segment in the carboxyl-containing polyether B1 is 14.2 wt % of the total amount of the polycarbodiimide compound A1 and the carboxyl-containing polyether B1.

[0051] Example 2

[0052] This embodiment provides an aqueous polycarbodiimide composition C2, which is obtained by reacting the polycarbodiimide compound A1 of Example 1 and the carboxyl-containing polyether B2.

[0053] The aqueous polycarbodiimide composition C2 of this embodiment is prepared by the following process:

[0054] (1) Take the polycarbodiimide compound A1 of Example 1;

[0055] (2) Preparation of carboxyl-containing polyether B2:

[0056] The reaction flask was purged with nitrogen, and 43.8 g of Clariant M350 (polyethylene glycol monomethyl ether, 350 molecular weight), 39.0 g of 2,2,6,6-tetramethylpiperidinoxide (TEMPO, Aladdin Chemical Reagent), and 160.0 g of dichloromethane were added, and heated to reflux, and dry air was introduced. 15.6 g of concentrated nitric acid was added, and the addition was completed within 15 minutes, and then the mixture was heated to reflux for 17 hours. Then 80.0 g of isopropanol was added and stirred for 1 hour. The volatile components were vacuumed to obtain 40.7 g of product, and the acid value was tested to be 148 mgKOH / g, and the carboxyl equivalent was calculated to be about 380.

[0057] Among them, the carboxyl-containing polyether B2 satisfies the general formula (1), and R 1 is methyl, R 2 is hydrogen, X is methylene, the average value of n is 6.2, and m is 0.

[0058] (3) Preparation of water-based polycarbodiimide composition C2:

[0059] The reaction flask was filled with nitrogen, and 100.0 g of polycarbodiimide compound A1 (containing 0.481 mol of carbodiimide groups) and 19.7 g of carboxyl-containing polyether B2 (containing 0.0518 mol of carboxyl groups) were added, and heated to 120°C for 2 h. At this time, the acid value was zero. 146.3 g of deionized water was added under high-speed stirring to obtain a milky liquid, i.e., an aqueous polycarbodiimide composition C2, which had a solid content of 45% and a carbodiimide group equivalent (based on solids) of 279.

[0060] The content of the polyethylene oxide segment in the carboxyl-containing polyether B2 is 11.8 wt % of the total amount of the polycarbodiimide compound A1 and the carboxyl-containing polyether B2.

[0061] Example 3

[0062] This embodiment provides an aqueous polycarbodiimide composition C3, which is obtained by reacting the polycarbodiimide compound A1 of Example 1 and the carboxyl-containing polyether B3.

[0063] The aqueous polycarbodiimide composition C3 of this embodiment is prepared by the following process:

[0064] (1) Take the polycarbodiimide compound A1 of Example 1;

[0065] (2) Preparation of carboxyl-containing polyether B3:

[0066] The reaction flask was purged with nitrogen, and 375 g of Clariant M3000 FL (polyethylene glycol monomethyl ether, 3000 molecular weight), 39.0 g of 2,2,6,6-tetramethylpiperidinoxide (TEMPO, Aladdin Chemical Reagent), and 160.0 g of dichloromethane were added, and heated to reflux, and dry air was introduced. 15.6 g of concentrated nitric acid was added, and the addition was completed within 15 minutes, and then the mixture was heated to reflux for 17 hours. Then 80.0 g of isopropanol was added and stirred for 1 hour. The volatile components were vacuumed to obtain 40.7 g of product, and the acid value was tested to be 148 mgKOH / g, and the carboxyl equivalent was calculated to be about 380.

[0067] Among them, the carboxyl-containing polyether B3 satisfies the general formula (1), and R 1 is methyl, R 2 is hydrogen, X is methylene, the average value of n is 66.4, and m is 0.

[0068] (3) Preparation of water-based polycarbodiimide composition C3:

[0069] The reaction flask was filled with nitrogen, and 100.0 g of polycarbodiimide compound A1 (containing 0.481 mol of carbodiimide groups) and 35.0 g of carboxyl-containing polyether B3 (containing 0.0117 mol of carboxyl groups) were added, and heated to 120°C for 2 h. At this time, the acid value was zero. 165.0 g of deionized water was added under high-speed stirring to obtain a milky liquid, i.e., an aqueous polycarbodiimide composition C3, which had a solid content of 45% and a carbodiimide group equivalent (based on solids) of 288.

[0070] The content of the polyethylene oxide segment in the carboxyl-containing polyether B3 is 25.0 wt % of the total amount of the polycarbodiimide compound A1 and the carboxyl-containing polyether B3.

[0071] Example 4

[0072] This embodiment provides an aqueous polycarbodiimide composition C4, which is obtained by reacting the polycarbodiimide compound A1 of Example 1 and the carboxyl-containing polyether B4.

[0073] The aqueous polycarbodiimide composition C4 of this embodiment is prepared by the following process:

[0074] (1) Take the polycarbodiimide compound A1 of Example 1;

[0075] (2) Preparation of carboxyl-containing polyether B4:

[0076] The reaction flask was purged with nitrogen, and 312.5 g of Clariant B11 / 150 (butyl mono-terminated ethylene oxide propylene oxide copolymer, 2500 molecular weight, ethylene oxide / propylene oxide molar ratio = 1:1), 39.0 g of 2,2,6,6-tetramethylpiperidin oxide (TEMPO, Aladdin Chemical Reagent), and 600.0 g of dichloromethane were added, and heated to reflux and dry air was introduced. 15.6 g of concentrated nitric acid was added, and the addition was completed within 15 minutes, and then the mixture was heated to reflux for 17 hours. Then 80.0 g of isopropanol was added and stirred for 1 hour. The volatile components were vacuumed to obtain 300.5 g of product, and the acid value was tested to be 22.2 mgKOH / g, and the carboxyl equivalent was calculated to be about 2530.

[0077] Among them, the carboxyl-containing polyether B4 satisfies the general formula (1), and R 1 is n-butyl, R 2 are hydrogen and methyl (the molar ratio of hydrogen / methyl is 4:1), X is methylene, the average value of n is 46.7, and m is 0.

[0078] (3) Preparation of aqueous polycarbodiimide composition C4:

[0079] The reaction flask was ventilated with nitrogen, and 100.0 g of polycarbodiimide compound A1 (containing 0.481 mol of carbodiimide groups) and 15.0 g of carboxyl-containing polyether B4 (containing 0.0059 mol of carboxyl groups) were added, and heated to 120°C for 2 h. At this time, the acid value was zero. The temperature was lowered to 90°C, 5.0 g of sodium dodecylbenzene sulfonate was added, and the mixture was stirred until uniform. 146.67 g of deionized water was added under high-speed stirring to obtain a milky white liquid, i.e., an aqueous polycarbodiimide composition C4, which had a solid content of 45% and a carbodiimide group equivalent (based on solid content) of 253.

[0080] The content of the polyethylene oxide segment in the carboxyl-containing polyether B4 is 5.3 wt % of the total amount of the polycarbodiimide compound A1 and the carboxyl-containing polyether B4.

[0081] Example 5

[0082] This embodiment provides an aqueous polycarbodiimide composition C5, which is obtained by reacting the polycarbodiimide compound A1 of Example 1 and the carboxyl-containing polyether B5.

[0083] The aqueous polycarbodiimide composition C5 of this embodiment is prepared by the following process:

[0084] (1) Take the polycarbodiimide compound A1 of Example 1;

[0085] (2) Preparation of carboxyl-containing polyether B5:

[0086] The reaction flask was filled with nitrogen, and 750 g of Clariant M750 (polyethylene glycol monomethyl ether, 750 molecular weight) and 168.2 g of methylhexahydrophthalic anhydride were added. The flask was heated to 120°C and reacted for 4 h. Infrared spectrum detection showed that the hydroxyl group was almost completely converted, the acid value was 61 mgKOH / g, and the carboxyl equivalent was calculated to be about 918.

[0087] Among them, the carboxyl-containing polyether B5 satisfies the general formula (1), and R 1 is methyl, R 2 is hydrogen, the average value of n is 15.3, m is 1, and X is a divalent alicyclic hydrocarbon group of 7 carbon atoms represented by formula (2):

[0088]

[0089] (3) Preparation of water-based polycarbodiimide composition C5:

[0090] The reaction flask was filled with nitrogen, and 100.0 g of polycarbodiimide compound A1 (containing 0.481 mol of carbodiimide groups) and 19.7 g of carboxyl-containing polyether B5 (containing 0.0215 mol of carboxyl groups) were added, and heated to 120°C for 2 h. At this time, the acid value was zero. 146.3 g of deionized water was added under high-speed stirring to obtain a milky liquid, i.e., an aqueous polycarbodiimide composition C5, which had a solid content of 45% and a carbodiimide group equivalent (based on solids) of 261.

[0091] The content of the polyethylene oxide segment in the carboxyl-containing polyether B5 is 12.1 wt % of the total amount of the polycarbodiimide compound A1 and the carboxyl-containing polyether B5.

[0092] Example 6

[0093] This embodiment provides an aqueous polycarbodiimide composition C6, which is obtained by reacting the polycarbodiimide compound A1 of Example 1 and the carboxyl-containing polyether B6.

[0094] The aqueous polycarbodiimide composition C6 of this embodiment is prepared by the following process:

[0095] (1) Take the polycarbodiimide compound A1 of Example 1;

[0096] (2) Preparation of carboxyl-containing polyether B6:

[0097] The reaction flask was filled with nitrogen, and 750 g of Clariant M750 (polyethylene glycol monomethyl ether, molecular weight 750) and 148.1 g of phthalic anhydride were added. The flask was heated to 120°C and reacted for 4 h. Infrared spectrum detection showed that the hydroxyl group was almost completely converted, the acid value was 62 mgKOH / g, and the carboxyl equivalent was calculated to be about 898.

[0098] Among them, the carboxyl-containing polyether B6 satisfies the general formula (1), and R 1 is methyl, R 2 is hydrogen, the average value of n is 15.3, m is 1, and X is a divalent aromatic hydrocarbon group of 6 carbon atoms as shown in formula (3):

[0099]

[0100] (3) Preparation of water-based polycarbodiimide composition C6:

[0101] A reaction flask was filled with nitrogen, and 100.0 g of polycarbodiimide compound A1 (containing 0.481 mol of carbodiimide groups) and 19.7 g of carboxyl-containing polyether B6 (containing 0.0219 mol of carboxyl groups) were added, and heated to 120°C for 2 h. At this time, the acid value was zero. 146.3 g of deionized water was added under high-speed stirring to obtain a milky white liquid, i.e., an aqueous polycarbodiimide composition C6, which had a solid content of 45% and a carbodiimide group equivalent (based on solids) of 261.

[0102] The content of the polyethylene oxide segment in the carboxyl-containing polyether B6 is 12.3 wt % of the total amount of the polycarbodiimide compound A1 and the carboxyl-containing polyether B6.

[0103] Example 7

[0104] This embodiment provides an aqueous polycarbodiimide composition C7, which is obtained by reacting a polycarbodiimide compound A2 with the carboxyl-containing polyether B1 of Example 1.

[0105] The aqueous polycarbodiimide composition C7 of this embodiment is prepared by the following process:

[0106] (1) Preparation of polycarbodiimide compound A2:

[0107] The reaction flask was filled with nitrogen, and 889.3 g of isophorone diisocyanate, 250.3 g of cyclohexyl isocyanate, and 12.6 g of 1-methylphosphine-1-oxide (MPO) were added. The flask was heated to 160° C. and reacted until the NCO value was zero to obtain polycarbodiimide compound A2.

[0108] The theoretical average functional number of the carbodiimide group in the polycarbodiimide compound A2 is 5.

[0109] (2) Take the carboxyl-containing polyether B1 of Example 1.

[0110] (3) Preparation of water-based polycarbodiimide composition C7:

[0111] The reaction flask was filled with nitrogen, and 100.0 g of polycarbodiimide compound A2 (containing 0.536 mol of carbodiimide groups) and 19.7 g of carboxyl-containing polyether B6 (containing 0.0253 mol of carboxyl groups) were added, and heated to 120°C for 2 h. At this time, the acid value was zero. 146.3 g of deionized water was added under high-speed stirring to obtain a milky liquid, i.e., an aqueous polycarbodiimide composition C6, which had a solid content of 45% and a carbodiimide group equivalent (based on solids) of 234.

[0112] The content of the polyethylene oxide segment in the carboxyl-containing polyether B1 is 14.2 wt % of the total amount of the polycarbodiimide compound A2 and the carboxyl-containing polyether B1.

[0113] Comparative Example 1

[0114] This comparative example provides an aqueous polycarbodiimide composition C8, which is obtained by reacting the polycarbodiimide compound A1 of Example 1 and the carboxyl-containing polyether B3.

[0115] The aqueous polycarbodiimide composition C8 of this embodiment is prepared by the following process:

[0116] (1) Take the polycarbodiimide compound A1 of Example 1;

[0117] (2) Take the carboxyl-containing polyether B3 of Example 3;

[0118] (3) Preparation of water-based polycarbodiimide composition C3:

[0119] The reaction flask was filled with nitrogen, and 100.0 g of polycarbodiimide compound A1 (containing 0.481 mol of carbodiimide groups) and 50.0 g of carboxyl-containing polyether B3 (containing 0.0167 mol of carboxyl groups) were added, and heated to 120°C for 2 h. At this time, the acid value was zero. 225.0 g of deionized water was added under high-speed stirring to obtain a milky liquid, i.e., an aqueous polycarbodiimide composition C3, which had a solid content of 40% and a carbodiimide group equivalent (based on solids) of 323.

[0120] The content of the polyethylene oxide segment in the carboxyl-containing polyether B3 is 32.1 wt % of the total amount of the polycarbodiimide compound A1 and the carboxyl-containing polyether B3.

[0121] Comparative Example 2

[0122] This comparative example provides an aqueous polycarbodiimide composition C9, which is different from Example 1-7. Instead of using the carboxyl-containing polyether B for modification, a hydrophilic monoalcohol containing an oxyalkylene group and a hydroxyl group is used to hydrophilically modify and cap the polycarbodiimide containing an isocyanate group at the terminal.

[0123] The aqueous polycarbodiimide composition C9 of this comparative example was synthesized in a similar manner to Example 1 of CN107099019A, with a solid content of 40% and an equivalent weight of carbodiimide groups (based on solids) of 406.

[0124] Comparative Example 3

[0125] This comparative example provides an aqueous polycarbodiimide composition C10, which is modified with a polyoxyalkylene-containing polyacrylic acid resin instead of the carboxyl-containing polyether B in Example 1-7.

[0126] The aqueous polycarbodiimide composition C10 of this comparative example was synthesized according to Example 1 of CN118085303A: the carbon solid content was 40%, and the equivalent weight of the carbodiimide group (based on the solid content) was 373.

[0127] Comparative Example 4

[0128] This comparative example provides an aqueous polycarbodiimide composition C11, which is obtained by reacting the polycarbodiimide compound A1 of Example 1 and the carboxyl-containing polyether B4.

[0129] The aqueous polycarbodiimide composition C11 of this comparative example is prepared by the following process:

[0130] (1) Take the polycarbodiimide compound A1 of Example 1;

[0131] (2) Take the carboxyl-containing polyether B4 of Example 4;

[0132] (3) Preparation of water-based polycarbodiimide composition C11:

[0133] The reaction flask was ventilated with nitrogen, and 100.0 g of polycarbodiimide compound A1 (containing 0.481 mol of carbodiimide groups) and 11.0 g of carboxyl-containing polyether B4 (containing 0.0043 mol of carboxyl groups) were added, and heated to 120°C for 2 h. At this time, the acid value was zero. The temperature was lowered to 90°C, 5.0 g of sodium dodecylbenzene sulfonate was added, and stirred until uniform. 141.8 g of deionized water was added under high-speed stirring to obtain a milky liquid, i.e., an aqueous polycarbodiimide composition C11, which had a solid content of 45% and an equivalent weight of carbodiimide groups (based on solids) of 244. The obtained dispersion was unstable and separated after standing.

[0134] The content of the polyethylene oxide segment in the carboxyl-containing polyether B4 is 4.0 wt % of the total amount of the polycarbodiimide compound A1 and the carboxyl-containing polyether B4.

[0135] Example 8

[0136] This embodiment provides a crosslinkable composition, including any one of the aqueous polycarbodiimide composition of embodiments 1-7, and an aqueous polyurethane dispersion (i.e., an aqueous resin containing a carboxyl group), wherein the solid content of the aqueous polycarbodiimide composition is 1.8 parts by weight (for example, if the solid content of the aqueous polycarbodiimide composition is 45%, then the added amount of the composition is 1.8 / 45%=4 parts), and the weight of the aqueous polyurethane dispersion is 70 parts.

[0137] Example 9

[0138] The present embodiment provides a water-based coating, comprising the following components in parts by weight: 4.5 parts of the water-based polycarbodiimide composition of any one of Embodiments 1-7; 70 parts of water-based polyurethane dispersion; 0.2 parts of silicone defoamer; 0.5 parts of silicone leveling agent; 0.5 parts of acetylene glycol wetting defoamer, 1 part of dispersant, 3 parts of matte powder, 10 parts of color paste, 6 parts of cosolvent; 0.5 parts of thickener; and 8.8 parts of water.

[0139] The preparation method of the water-based paint of this embodiment includes the following steps: mixing the components evenly to obtain the water-based paint.

[0140] Example 10

[0141] This embodiment provides a product coated with the water-based coating of Embodiment 9.

[0142] The water-based coatings in Example 9, i.e., the water-based coatings formed by the water-based polycarbodiimide compositions in Examples 1-7, were sprayed on the surface of the plastic substrate to form a coating film with a thickness of 23±3 μm on the surface of the plastic substrate.

[0143] Performance Testing

[0144] The performance of the aqueous polycarbodiimide compositions of Examples 1-7 and Comparative Examples 1-3 was tested as follows:

[0145] The water-based polycarbodiimide compositions C1-C10 of Examples 1-7 and Comparative Examples 1-3, and the commercial water-based polycarbodiimide composition OS-8000 (Guangzhou Guanzhi New Materials, solid content: 40%, not modified with carboxyl-containing polyether) were respectively formulated with a commercial water-based polyurethane dispersion (trade name PU-7206, Guangzhou Guanzhi New Materials, solid content: 40%) into water-based coatings 1-11 according to the formula in Table 1.

[0146] Table 1 Water-based coating formula

[0147]

[0148] The following performance tests were conducted on water-based coatings 1-11:

[0149] Water resistance test: spray the freshly prepared water-based paint on the plastic PC substrate with a film thickness of 23±3μm, bake at 70℃ for 2h, and then keep at room temperature overnight. Soak the plastic plate in room temperature water and observe the whitening and bubbling of the coating after 24h. Score 1-5 points, with 5 points being the best.

[0150] Alcohol rub resistance test: spray the newly prepared water-based paint on the plastic PC substrate with a film thickness of 23±3μm, bake at 70℃ for 2h, and then keep at room temperature overnight. Use a solvent rub tester to test according to GB / T 23989-2009 with a load of 500g.

[0151] Gloss test: Tested according to GB / T 9754-2007.

[0152] Adhesion test: Tested according to GB 9286-98, with a rating of 0-5, 0 being the best.

[0153] The test results are shown in the following table:

[0154] Table 2 Test results of water-based coatings

[0155]

[0156] The water-based coating formula of Table 1 and the performance test results of Table 2 show that the water-based coatings 1-7 added with the water-based polycarbodiimide compositions C1-C7 of Examples 1-7 of the present invention have excellent water resistance and ethanol resistance. The water-based coating 8 added with the water-based polycarbodiimide composition C8 of Comparative Example 1 has poor water resistance and alcohol resistance; this is because in the water-based polycarbodiimide composition C8 of Comparative Example 1, the content of the polyoxyethylene chain segment in the carboxyl-containing polyether B3 accounts for too high a proportion, resulting in the water-based polycarbodiimide composition C8 itself having a high hydrophilicity, which affects the water resistance and alcohol resistance of the coating film formed by the water-based coating 8. However, the water-based polycarbodiimide composition C11 in Comparative Example 4 has too low a proportion of the polyoxyethylene chain segment in the carboxyl-containing polyether, resulting in the water-based polycarbodiimide composition C11 itself having too low hydrophilicity and failing to form a stable aqueous dispersion. The water-based coating 9 to which the water-based polycarbodiimide composition C9 of comparative example 2 is added, and the water-based coating 11 to which the water-based polycarbodiimide composition OS-8000 is added, have poor water resistance and alcohol resistance; this is because the water-based polycarbodiimide composition C9 of water-based coating 9 and the water-based polycarbodiimide composition OS-8000 use a hydrophilic unit alcohol containing an oxyalkylene group and a hydroxyl group to hydrophilically modify and cap the polycarbodiimide containing an isocyanate group at the terminal, resulting in a low content of polycarbodiimide groups and insufficient crosslinking density of the coating film. The water-based polycarbodiimide composition C10 in water-based coating 10 is modified with a polyacrylic resin containing a polyoxyalkylene group, and a high proportion of polyacrylic resin is required to stabilize the aqueous dispersion of the composition, which also results in a low content of polycarbodiimide groups and a low crosslinking density of the coating film.

[0157] The above-mentioned embodiments only express several implementation methods of the present invention, and the description is relatively specific and detailed, but it cannot be understood as limiting the scope of the invention patent. It should be pointed out that for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present invention, and the present invention is also intended to include these modifications and modifications.

Claims

1. An aqueous polycarbodiimide composition, characterized in that: The invention comprises a reaction product of a polycarbodiimide compound (A) and a carboxyl-containing polyether (B); wherein: The polycarbodiimide compound (A) is at least one of polycarbodiimides that do not contain a hydrophilic group and a urethane bond structure; the average functional number of the carbodiimide group in the polycarbodiimide compound (A) is 2-20; The carboxyl-containing polyether (B) is at least one of the compounds represented by formula (1): In formula (1), R 1 is a hydrocarbon group having 1 to 8 carbon atoms; R 2 is hydrogen or methyl; X is a divalent aliphatic hydrocarbon group or aromatic hydrocarbon group having 1 to 8 carbon atoms; n is an integer of 6 to 68, and m is 0 or 1; The carboxyl-containing polyether (B) The content of the polycarbodiimide compound (A) and the carboxyl-containing polyether (B) is 5-25wt% of the total amount.

2. The aqueous polycarbodiimide composition according to claim 1, characterized in that: The polycarbodiimide compound (A) is at least one of an aliphatic polycarbodiimide and an aromatic polycarbodiimide.

3. The aqueous polycarbodiimide composition according to claim 1, characterized in that: The raw material for preparing the polycarbodiimide compound (A) is an aliphatic diisocyanate and / or an aromatic diisocyanate; the aliphatic diisocyanate is at least one of hexamethylene diisocyanate, isophorone diisocyanate, and dicyclohexylmethane diisocyanate; the aromatic diisocyanate is at least one of toluene diisocyanate and diphenylmethane diisocyanate.

4. A method for preparing an aqueous polycarbodiimide composition as claimed in any one of claims 1 to 3, characterized in that: The polycarbodiimide compound (A) and the carboxyl-containing polyether (B) are added into a container and reacted until the acid value reaches zero to obtain the water-based polycarbodiimide composition.

5. The method for preparing the aqueous polycarbodiimide composition according to claim 4, characterized in that: The reaction temperature is 60-130°C and the reaction time is 2-10h.

6. The method for preparing the aqueous polycarbodiimide composition according to claim 4, characterized in that: The mixture is reacted until the acid value is zero, and water is added for emulsification to obtain the aqueous polycarbodiimide composition; wherein the amount of water added is 45-75% of the total weight of the aqueous polycarbodiimide composition.

7. A crosslinkable composition, characterized in that: The invention comprises the aqueous polycarbodiimide composition as claimed in any one of claims 1 to 3 and an aqueous resin containing a carboxyl group.

8. A water-based paint, characterized in that: Comprising the crosslinkable composition of claim 7.

9. An article coated with the water-based coating according to claim 8.

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