A high-strength waterproof coating for pallets and preparation method thereof

Abstract

The invention discloses a high-strength waterproof coating for pallets and a preparation method thereof, which belongs to the technical field of waterproof coatings. The coating comprises a polyurea prepolymer, a flame retardant modified polyaspartic acid ester and a graphene oxide modified polyaspartic acid ester; the preparation method comprises the following steps: adding polyaspartic acid ester and a hexamethylene diisocyanate-based polyisocyanate trimer to an organic solvent, stirring and dissolving, heating and stirring to react, to obtain a polyurea prepolymer, adding flame retardant modified polyaspartic acid ester and graphene oxide modified polyaspartic acid ester to an organic solvent, stirring and dispersing, and then dripping to the above polyurea prepolymer, heating and stirring. The protective coating uses flame retardant modified polyaspartic acid ester and graphene oxide modified polyaspartic acid ester as raw materials to enhance the impact resistance of the coating after curing, and utilizes the excellent wear resistance and weather resistance of the polyurea material to enhance its application potential in pallet materials.

Description

Technical Field

[0001] The invention belongs to the technical field of waterproof coatings, and in particular relates to a high-strength waterproof coating for a pallet and a preparation method thereof. Background Art

[0002] A pallet is a load-bearing device for cargo collection, stacking and transportation. It is the process of packing a certain amount of scattered goods into the form of a pallet - that is, the process of converting bulk goods into palletized goods, which plays a role in protecting products and facilitating storage and transportation.

[0003] Common pallets include wooden pallets, metal pallets, plastic pallets and paper pallets. The limiting factors for the long-term use of the above pallets are mainly corrosion caused by moisture and damage when loading items. If you choose to use alternative plastic pallets in layers, the pallet weight will be too high, increasing transportation costs. Therefore, choosing to apply waterproof coating on the surface of lightweight materials to improve the water resistance and wear resistance of the pallet can solve the above problems well.

[0004] Introducing graphene materials into polyurea coatings is an effective way to improve the impact resistance and corrosion resistance of the coatings. However, there is a strong π-π interaction between graphene sheets, and graphene sheets are very prone to irreversible agglomeration. In graphene-modified materials, graphene cannot be dispersed in the matrix material in a single layer state, and even obvious aggregation occurs, making it impossible for the material to achieve the expected modification effect and the performance is unstable. The existing conventional dispersants have limited dispersing capacity, and in the polyurea matrix, the uneven dispersion of graphene materials will directly affect the impact resistance of the coating after curing. Summary of the invention

[0005] The object of the present invention is to provide a high-strength waterproof coating for pallets and a preparation method thereof, so as to solve the problem that the waterproof coating for pallets has poor impact resistance.

[0006] The purpose of the present invention can be achieved by the following technical solutions:

[0007] A high-strength waterproof coating for a pallet, comprising component A, component B and component C; the component A is a polyurea prepolymer; the molar ratio of NCO:NH in the polyurea prepolymer is 1.05-1.1.5:1;

[0008] The B component is a flame retardant modified polyaspartic acid ester; the mass fraction of the B component is 18%-20%; the flame retardant modified polyaspartic acid ester is obtained by Michael addition polymerization of a dicarboxylic acid ester and a phosphorus-containing diamine, and the molar ratio of the dicarboxylic acid ester to the phosphorus-containing diamine is 2:1;

[0009] The C component is graphene oxide modified polyaspartic acid ester; the mass fraction of the C component is 10%-12%; the amino-terminated hyperbranched siloxane grafted modified graphene oxide and diamine are mixed, and then dicarboxylic acid ester is added to heat and react to obtain the C component; the molar ratio of dicarboxylic acid ester to diamine is 1.5:1; the amino-terminated hyperbranched siloxane grafted modified graphene oxide accounts for 10% of the graphene oxide modified polyaspartic acid ester.

[0010] Furthermore, the phosphorus-containing diamine is phenyl phosphoramide.

[0011] Furthermore, the diamine is one of hexamethylenediamine, amino-terminated polyether and meta-xylylenediamine.

[0012] Furthermore, the dicarboxylic acid ester is one of diethyl maleate, dimethyl fumarate, diethyl fumarate, diethyl itaconate and dimethyl itaconate.

[0013] Furthermore, the amino-terminated hyperbranched siloxane grafted modified graphene oxide is prepared by the following steps:

[0014] Silane coupling agent KH-550 was added into water, hydrochloric acid was added to adjust the system to weak acidity, the temperature was raised to 50°C, and the reaction was carried out for 4 hours. After the reaction was completed, the solvent was evaporated to obtain amino-terminated hyperbranched polysiloxane;

[0015] The amino-terminated hyperbranched polysiloxane, 5 g / L graphene oxide aqueous dispersion and ethanol were mixed, the pH value was adjusted to be weakly alkaline, refluxed and stirred for reaction at a temperature of 80° C. for 8 hours, and centrifuged and washed to obtain the amino-terminated hyperbranched polysiloxane grafted modified graphene oxide.

[0016] Furthermore, the mass ratio of the amino-terminated hyperbranched polysiloxane to the graphene oxide aqueous dispersion is 1:4.

[0017] Furthermore, the material of the pallet includes EPS (expanded polystyrene), polyurethane foam, PP (polypropylene), and PE (polyethylene).

[0018] A method for preparing a high-strength waterproof coating for a pallet comprises the following steps:

[0019] Add polyaspartic acid ester and hexamethylene diisocyanate-based polyisocyanate trimer into an organic solvent, stir and dissolve, heat to 60°C and stir to react for 50-60 minutes to obtain a polyurea prepolymer (component A), add flame retardant modified polyaspartic acid ester (component B) and graphene oxide modified polyaspartic acid ester (component C) into an organic solvent, stir and disperse, then add dropwise into the above polyurea prepolymer (component A), stir at 40°C for 2-3 hours to obtain a high-strength waterproof coating for pallets.

[0020] Furthermore, the polyaspartic acid ester in the urea prepolymer is one of polyaspartic acid ester resin F420 and polyaspartic acid ester resin F524.

[0021] Furthermore, the organic solvent is tetrahydrofuran.

[0022] Beneficial effects of the present invention:

[0023] The present invention selects polyurea coating as the protective coating for the pallet, and the coating comprises component A, component B and component C; the component A is a polyurea prepolymer; the component B is a flame retardant modified polyaspartic acid ester; the component C is a graphene oxide modified polyaspartic acid ester; the protective coating selects flame retardant modified polyaspartic acid ester and graphene oxide modified polyaspartic acid ester as raw materials to enhance the impact resistance of the coating after curing, and utilizes the excellent wear resistance and weather resistance of the polyurea material to enhance its application potential in pallet materials.

[0024] In the present invention, flame retardant modified polyaspartic acid ester is added, and in the process of introducing phosphorus-containing flame retardant elements (derived from phenyl phosphorodiamidate), steric hindrance groups (phenyl groups have large steric hindrance) are introduced into the molecular structure of the coating, which can not only improve the flame retardant properties of the coating, but also synergistically improve the impact resistance of the coating with graphene oxide modified polyaspartic acid ester.

[0025] In the present invention, graphene oxide-modified polyaspartic acid ester is added to the coating, and as the amount of graphene oxide-modified polyaspartic acid ester used increases (corresponding to the increase of graphene oxide), the contact angle of water increases first and then decreases. A small amount of graphene oxide can modify polyaspartic acid ester to enhance the hydrophobicity of the coating after film formation, and graphene oxide can be better dispersed by treating it with terminal amino hyperbranched polysiloxane. In addition, the thermal stability of the Si-O-Si segment is higher than that of polyurea, and the heat resistance of the coating can also be improved to a certain extent.

[0026] The polyurea coating prepared by the present invention can form an effective protective layer on the surface of the pallet, which can not only meet the basic protection needs, but also adjust its performance according to the specific application scenarios, increase the waterproof and flame retardant effects, and improve the wide applicability of the pallet in industry and daily life. DETAILED DESCRIPTION

[0027] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] Example 1

[0029] The flame retardant modified polyaspartic acid ester is prepared by Michael addition polymerization of dicarboxylic acid ester and phosphorus-containing diamine; the specific steps include:

[0030] Under nitrogen protection and at a temperature of 50°C, diethyl maleate was added to phenyl phosphorodiamidate in a molar ratio of 1:2 using tetrahydrofuran as a solvent. After the addition, the temperature was raised to 60°C, and the reaction was refluxed and stirred for 35 hours to obtain flame-retardant modified polyaspartic acid ester.

[0031] Example 2

[0032] Preparation of flame retardant modified polyaspartic acid ester comprises the following steps:

[0033] Under nitrogen protection and at a temperature of 55°C, diethyl fumarate was added to phenyl phosphorodiamidate in a molar ratio of 1:2 using tetrahydrofuran as a solvent. After the addition, the temperature was raised to 60°C, and the reaction was refluxed and stirred for 30 hours to obtain flame-retardant modified polyaspartic acid ester.

[0034] Example 3

[0035] Preparation of flame retardant modified polyaspartic acid ester comprises the following steps:

[0036] Under nitrogen protection and at a temperature of 50°C, dimethyl fumarate was added to phenyl phosphorodiamidate in a molar ratio of 1:2 using tetrahydrofuran as a solvent. After the addition, the temperature was raised to 60°C, and the reaction was refluxed and stirred for 35 hours to obtain flame-retardant modified polyaspartic acid ester.

[0037] Comparative Example 1

[0038] Compared with Example 1, the comparative example replaces phenyl phosphorodiamidamide with hexamethylenediamine, and the other raw materials and preparation method remain unchanged.

[0039] Example 4

[0040] Preparation of graphene oxide modified polyaspartic acid ester comprises the following steps:

[0041] 40 g of silane coupling agent KH-550 was added to 60 mL of water, and hydrochloric acid was added to adjust the system to weak acidity (pH value was 5), and the temperature was raised to 50° C. and reacted for 4 h. After the reaction was completed, the solvent was evaporated to obtain amino-terminated hyperbranched polysiloxane;

[0042] 10 g of amino-terminated hyperbranched polysiloxane, 40 mL of 5 g / L graphene oxide aqueous dispersion, and 60 mL of ethanol were mixed, the pH value was adjusted to be weakly alkaline (pH value was 9), refluxed and stirred at 80° C. for 8 h, and centrifuged and washed to obtain amino-terminated hyperbranched polysiloxane grafted modified graphene oxide;

[0043] The amino-terminated hyperbranched siloxane grafted modified graphene oxide and hexamethylenediamine were mixed, and then diethyl maleate was added and the temperature was raised to 100°C, and the reaction was carried out for 10 hours to obtain component C; the molar ratio of diethyl dimaleate to hexamethylenediamine was 1.5:1; the amino-terminated hyperbranched siloxane grafted modified graphene oxide accounted for 10% in the graphene oxide modified polyaspartic acid ester.

[0044] Comparative Example 2

[0045] Compared with Example 4, this comparative example replaces the amino-terminated hyperbranched siloxane grafted modified graphene oxide with graphene oxide modified by aminosilane coupling agent KH-550, and the other raw materials and preparation methods remain unchanged. 0.2g of graphene oxide is added to 100mL of 80% ethanol aqueous solution by mass fraction, and 10g of silane coupling agent KH-550 is added, and the temperature is raised to 80°C, and the mixture is refluxed and stirred for 8h. After the reaction is completed, the mixture is centrifuged and washed with ethanol to obtain aminosilane-modified graphene oxide.

[0046] Example 5

[0047] A high-strength waterproof coating for pallets, comprising component A, component B and component C; the component A is a polyurea prepolymer; the component B is a flame-retardant modified polyaspartic acid ester prepared by the method in Example 1; the component C is a graphene oxide modified polyaspartic acid ester prepared by the method in Example 4, the molar ratio of NCO:NH in the polyurea prepolymer of component A is 1.05-1.1.5:1; the mass fraction of component B is 20%; the mass fraction of component C is 10%. The molar ratio of NCO:NH in component A of the coating is adjusted according to Table 1, and the mechanical properties of the sample are tested;

[0048] Table 1

[0049] sample NCO / NH molar ratio Mass fraction of component B / % Mass fraction of C component % a 1.05 20 10 b 1.08 20 10 c 1.10 20 10 d 1.13 20 10 e 1.15 20 10

[0050] A method for preparing a high-strength waterproof coating for a pallet comprises the following steps:

[0051] Add polyaspartic acid ester resin F420 and hexamethylene diisocyanate-based polyisocyanate trimer (HT-110) into tetrahydrofuran, stir and dissolve, heat to 60°C and stir to react for 50-60 minutes to obtain a polyurea prepolymer (component A), add flame retardant modified polyaspartic acid ester (component B) and graphene oxide modified polyaspartic acid ester (component C) into tetrahydrofuran, stir and disperse, then add dropwise into the above polyurea prepolymer (component A), stir at 40°C for 2-3 hours, and obtain a high-strength waterproof coating for pallets.

[0052] The prepared coatings were used to prepare the test samples, denoted as a to e, and sprayed on the polished aluminum sheet and the polytetrafluoroethylene non-stick board, respectively, and cured at room temperature for seven days. The polyurea coated aluminum sheet was tested for its impact resistance, with a thickness of 1 mm, and the mechanical properties were tested. The results are shown in Table 2 below:

[0053] The tensile strength test is carried out in accordance with the provisions of GB / T23446-2009 "Spraying Polyurea Waterproof Coating";

[0054] The impact resistance is tested according to ASTM D2794.

[0055] Table 2

[0056] Sample Tensile strength / MPa Shock resistance / J a 10.6 12.04 b 11.5 12.16 c 12.1 12.31 d 11.9 12.29 e 11.2 12.25

[0057] From the results recorded in Table 2, it can be seen that with the increase of NCO / NH molar ratio, the mechanical properties of the sample are improved to a certain extent, but with the continued increase of the molar ratio, the stability of the emulsion decreases, which affects the mechanical properties of the sample.

[0058] Example 6

[0059] Compared with sample c in Example 5 (NCO / NH molar ratio of component A is 1.1), the ratio of component B to component C is adjusted, and the remaining raw materials and preparation process are the same as those in Example 5. For details, refer to Table 3 to test the performance of the sample.

[0060] A comparative sample 1 was prepared. Compared with sample c, component B of comparative sample 1 was polyaspartic acid ester prepared in comparative example 1 during the preparation process, and the remaining raw materials and the preparation process were the same as those of sample c.

[0061] A comparative sample 2 was set up. Compared with sample C, in the preparation process, component C of comparative sample 2 selected graphene oxide modified polyaspartic acid ester prepared in comparative example 2, and the other raw materials and preparation process remained the same as those of sample c.

[0062] Flame retardant grade: Vertical burning (UL94) test is performed according to ASTM3801 standard, sample size is 125mm×12.7mm×3.2mm;

[0063] Table 3

[0064]

[0065] From the test results, the flame retardant properties of the coating can be improved by adding flame retardant modified polyaspartic acid ester. Compared with comparative sample 2, the present invention utilizes amino-terminated hyperbranched polysiloxane to process graphene oxide, which can be better dispersed. In addition, the thermal stability of Si-O-Si segments is higher than that of polyurea, and the heat resistance of the coating is also improved to a certain extent; amino-terminated hyperbranched polysiloxane processes graphene oxide to introduce more silicon elements, and flame retardant modified polyaspartic acid esters are used to improve the flame retardant properties of the material. In the process of introducing phosphorus-containing flame retardant elements (derived from phenyl phosphoramide), steric groups (the steric hindrance of phenyl is larger) are introduced into the molecular structure of the coating, which has an internal plasticizing effect, can improve the toughness of the coating, and then improve the impact resistance.

[0066] As the amount of component C (graphene oxide modified polyaspartic acid ester) increases, the contact angle of water increases first and then decreases. A small amount of graphene oxide can enhance the hydrophobicity of the coating after film formation, but the performance improvement of the comparative sample 2 treated with a conventional silane coupling agent is limited. The component C modified by the branched structure in the present invention can better improve the stability of the sample and be better applied to the preparation and application of the coating.

[0067] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0068] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A high-strength waterproof coating for pallets, characterized in that: The invention comprises component A, component B and component C; the component A is a polyurea prepolymer; the molar ratio of NCO:NH in the polyurea prepolymer is 1.05-1.1.5:1; The B component is a flame retardant modified polyaspartic acid ester; the mass fraction of the B component is 18%-20%; the flame retardant modified polyaspartic acid ester is obtained by Michael addition polymerization of a dicarboxylic acid ester and a phosphorus-containing diamine, and the molar ratio of the dicarboxylic acid ester to the phosphorus-containing diamine is 2:1; the phosphorus-containing diamine is phenyl phosphoramide; The C component is graphene oxide modified polyaspartic acid ester; the mass fraction of the C component is 10%-12%; the amino-terminated hyperbranched siloxane grafted modified graphene oxide and diamine are mixed, and then dicarboxylic acid ester is added to heat and react to obtain the C component; the molar ratio of dicarboxylic acid ester to diamine is 1.5:1; the amino-terminated hyperbranched siloxane grafted modified graphene oxide accounts for 10% in the graphene oxide modified polyaspartic acid ester; The amino-terminated hyperbranched siloxane grafted modified graphene oxide is prepared by the following steps: Silane coupling agent KH-550 was added into water, the system was adjusted to be weakly acidic, the temperature was raised to 50°C, and the reaction was carried out for 4 hours. After the reaction was completed, the solvent was evaporated to obtain amino-terminated hyperbranched polysiloxane; The amino-terminated hyperbranched polysiloxane, 5 g / L graphene oxide aqueous dispersion and ethanol were mixed, the pH value was adjusted to be weakly alkaline, refluxed and stirred for reaction at a temperature of 80° C. for 8 hours, and centrifuged and washed to obtain the amino-terminated hyperbranched polysiloxane grafted modified graphene oxide.

2. The high-strength waterproof coating for pallets according to claim 1, characterized in that: The diamine is one of hexamethylenediamine, amino-terminated polyether and meta-xylylenediamine.

3. The high-strength waterproof coating for pallets according to claim 1, characterized in that: The dicarboxylic acid ester is one of diethyl maleate, dimethyl fumarate, diethyl fumarate, diethyl itaconate and dimethyl itaconate.

4. The high-strength waterproof coating for pallets according to claim 1, characterized in that: The amino-terminated hyperbranched polysiloxane and the graphene oxide aqueous dispersion are used in a mass ratio of 1:

4.

5. A method for preparing a high-strength waterproof coating for a pallet according to any one of claims 1 to 4, characterized in that: The steps include: Add polyaspartic acid ester and hexamethylene diisocyanate-based polyisocyanate trimer into an organic solvent, stir and dissolve, heat to 60°C and stir to react for 50-60 minutes to obtain a polyurea prepolymer, add flame retardant modified polyaspartic acid ester and graphene oxide modified polyaspartic acid ester into an organic solvent, stir and disperse, then add dropwise into the above polyurea prepolymer and stir at 40°C for 2-3 hours to obtain a high-strength waterproof coating for pallets.

6. The method for preparing a high-strength waterproof coating for a pallet according to claim 5, characterized in that: The polyaspartic acid ester in the urea prepolymer is one of polyaspartic acid ester resin F420 and polyaspartic acid ester resin F524.

7. The method for preparing a high-strength waterproof coating for a pallet according to claim 5, characterized in that: The organic solvent is tetrahydrofuran.

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