A wear-resistant coating modified injection mold and its preparation process

Abstract

The present invention relates to the technical field of wear-resistant coatings, specifically to an injection mold modified with a wear-resistant coating and a preparation process thereof. The wear-resistant coating prepared by the present invention comprises a base coating and a surface coating; wherein the surface coating has low surface energy and high strength; the base coating is soft and tough, and can be cured by light and heat; the present invention also loads silicon dioxide on the surface of boron nitride by a precipitation method, and adds it to the base coating as a filler to improve the wear resistance; after curing, the base coating and the surface coating undergo a cross-linking reaction, and the two complement each other to jointly improve the performance of the wear-resistant coating. After the wear-resistant coating is modified, the injection mold is more convenient to use and maintain.

Description

Technical Field

[0001] The invention relates to the technical field of wear-resistant coatings, in particular to an injection mold modified with a wear-resistant coating and a preparation process thereof. Background Art

[0002] Injection molds are commonly used tools in the production of plastic products and are responsible for giving plastic products their complete structural form. The general production process involves injecting heated, molten plastic into the mold cavity under high pressure using an injection molding machine. After cooling and solidification, the resulting molded product is obtained.

[0003] With the development of injection mold processing technology, its structure has become increasingly complex. With the continuous emergence of new plastic raw materials, more and more plastic materials are causing significant corrosion and wear to the mold. Since injection molding is a processing method used for mass production of certain complex-shaped parts, when the injection mold is corroded and worn, its precise dimensions will be affected, resulting in a decrease in the yield rate. The solution is to select a suitable coating to protect the injection mold and ensure the fluidity of the plastic melt in the injection mold. Therefore, it is very necessary to develop an injection mold modified with a wear-resistant coating. Summary of the Invention

[0004] The object of the present invention is to provide an injection mold modified with a wear-resistant coating and a preparation process thereof, so as to solve the problems raised in the above background technology.

[0005] In order to solve the above technical problems, the present invention provides the following technical solutions: an injection mold modified with a wear-resistant coating and a preparation process thereof, comprising the following steps:

[0006] Step 1:

[0007] S11: Mix 2,4,6,8-tetramethylcyclotetrasiloxane and allyl glycidyl ether, heat the system to 50-60°C, stir for 5-10 minutes, add KARSTEDT catalyst, stir until the temperature stabilizes, and continue the reaction for 3-5 hours to obtain tetraepoxysiloxane;

[0008] S12: taking tetraepoxysiloxane and heating it to 85-95° C., mixing α-methacrylic acid, catalyst benzyltriethylammonium chloride, and polymerization inhibitor p-hydroxyanisole, and adding the mixture dropwise to the tetraepoxysiloxane, controlling the addition of the mixture to be completed within 30-60 minutes; after the addition is completed, heating it to 100-110° C. and reacting it for 2-3 hours to obtain an acrylic acid-modified silicone resin;

[0009] Step 2:

[0010] S21: adding boron nitride to isopropanol to obtain a suspension having a concentration of 1 to 3 g / L, ultrasonically oscillating the suspension at a power of 200 to 300 W for 24 hours, centrifuging the suspension at 3000 to 4000 rpm for 10 to 15 minutes, collecting the upper layer of the suspension, and further centrifuging the suspension at 8000 to 10000 rpm for 10 to 15 minutes, collecting the upper layer of the suspension, and air-drying the supernatant to obtain the exfoliated boron nitride;

[0011] S22: Disperse the exfoliated boron nitride in deionized water, adjust the pH to 8-8.5 with tris(hydroxymethyl)aminomethane, add ethyl orthosilicate to hydrolyze for 6 hours, and then age for 1-2 hours, and add 3-mercaptopropyltrimethoxysilane; stir and react for 3-4 hours, then filter, and wash the filtrate with deionized water and ethanol for 3-5 times, respectively, to obtain silica-modified boron nitride powder;

[0012] Step 3:

[0013] S31: Perfluoropolyether diol and isophorone diisocyanate are mixed, dibutyltin dilaurate is used as a catalyst, the temperature is raised to 70-80° C., the reaction is carried out for 2-4 hours, and the mixture is cooled to obtain a polyurethane prepolymer;

[0014] S32: adding glycidol to a polyurethane prepolymer at 40-50° C., using dibutyltin dilaurate as a catalyst, and reacting at 70-80° C. for 1-2 hours to obtain an epoxy-terminated fluorinated polyurethane prepolymer;

[0015] Step 4:

[0016] S41: Select an injection mold made of aluminum alloy, vertically cross-grind the surface of the injection mold with sandpaper for 5 minutes, clean the surface with clean water, and then soak the injection mold in hydrochloric acid solution and sodium hydroxide solution in sequence for 3 minutes; clean with acetone to remove surface impurities, apply a mixture of silane coupling agent KH550, ethanol, and deionized water to the surface of the injection mold, and then dry at 100-120° C. for 1-2 hours to obtain a pretreated injection mold;

[0017] S42: Mix acrylic modified silicone resin, photoinitiator, curing agent, silica modified boron nitride powder and acetone, and apply it on the surface of the pre-treated injection mold at 20-30 mW / cm 2 After UV curing for 30 to 90 seconds, the film is dried by forced air at 50 to 60° C. to obtain a base coating with a thickness of 300 to 500 μm.

[0018] S43: The epoxy-terminated fluorinated polyurethane prepolymer, epoxy resin E51, curing agent, defoaming agent and epoxy diluent are mixed and coated on the base coating, and cured at 100-120° C. for 1-2 hours to obtain a surface coating with a thickness of 100-200 μm.

[0019] Furthermore, in S11, the molar ratio of 2,4,6,8-tetramethylcyclotetrasiloxane to allyl glycidyl ether is 1:4.

[0020] Furthermore, in S12, tetraepoxysiloxane and α-methacrylic acid are reacted at a molar ratio of epoxy group to carboxyl group of 2:1.

[0021] Furthermore, in S22, the amount of each component used, by weight, is 3 to 5 parts of exfoliated boron nitride dispersion, 2.5 to 3 parts of ethyl orthosilicate, and 0.2 to 0.28 parts of 3-mercaptopropyltrimethoxysilane.

[0022] Furthermore, in S31, perfluoropolyether diol and isophorone diisocyanate are mixed at a molar ratio of hydroxyl group to isocyanate group of 2:1.

[0023] Furthermore, in S32, glycidol is added to the polyurethane prepolymer at a molar ratio of hydroxyl group to isocyanate group of 1:1.

[0024] Furthermore, in S41, the concentration of the hydrochloric acid solution is 0.2-0.25 mol / L, and the concentration of the sodium hydroxide solution is 0.2-0.25 mol / L.

[0025] Furthermore, in S41, the weight ratio of silane coupling agent KH550, ethanol, and deionized water is 20:(70-75):(5-10).

[0026] Furthermore, in S42, acrylic modified silicone resin, photoinitiator, curing agent, silica modified boron nitride powder, and acetone are mixed in a weight ratio of (100-120):(3-5):(46-54):(3-8):100.

[0027] Furthermore, in S43, the amounts of the components used, by weight, are 20 to 30 parts of epoxy-terminated fluorine-containing polyurethane prepolymer, 70 to 80 parts of epoxy resin E51, 35 to 40 parts of curing agent, 8 to 13 parts of defoaming agent, and 10 to 15 parts of epoxy diluent.

[0028] Compared with the prior art, the present invention achieves the following beneficial effects: it provides an injection mold modified with a wear-resistant coating and a preparation process thereof. After pre-treating the surface of the injection mold, the present invention sequentially applies two different resin coatings to the mold surface, forming a base coating and a top coating, respectively. The base coating has strong adhesion to the mold surface and, after thermal curing, forms crosslinks with the top coating, thereby providing excellent protection for the injection mold.

[0029] Specifically, in the present invention, the bottom coating is made of 2,4,6,8-tetramethylcyclotetrasiloxane and allyl glycidyl ether as raw materials, and an addition reaction is carried out through a silicon-hydrogen bond and a carbon-carbon double bond to obtain tetraepoxysiloxane, and then the tetraepoxysiloxane and α-methacrylic acid are subjected to an esterification reaction to introduce a carbon-carbon double bond to obtain an acrylic acid-modified silicone resin. In order to give the coating good wear resistance, the present invention loads silica as an inorganic filler on the surface of boron nitride by a precipitation method, and uses 3-mercaptopropyltrimethoxysilane to modify and introduce a mercapto group. Under the action of a photoinitiator, the acrylic acid-modified silicone resin undergoes self-polymerization and can react with the mercapto group on the filler surface to form a bottom coating on the mold surface. The introduction of inorganic fillers improves the wear resistance of the coating, and the silicon-oxygen bonds in the coating also have strong flexibility and heat resistance, which improves the shortcomings of conventional vinyl resins that have large volume shrinkage, easy cracking, and poor high temperature resistance during polymerization.

[0030] The present invention uses perfluoropolyether diol and isophorone diisocyanate as raw materials to react and prepare a polyurethane prepolymer, which is then terminated with glycidol to obtain an epoxy-terminated fluorine-containing polyurethane prepolymer; the epoxy-terminated fluorine-containing polyurethane prepolymer is mixed with epoxy resin E51, coated on the surface of a base coating, and cured by heating to form a top coating. During the temperature-raising and curing stage, the epoxy-terminated fluorine-containing polyurethane prepolymer and the epoxy resin can be chemically cross-linked via the epoxy groups, while the epoxy groups in the base coating can also self-cross-link and react with the epoxy groups in the top coating at high temperatures. Thermal curing not only improves the bonding performance between the base coating and the top coating, but also greatly improves the problem of poor bonding performance of conventional vinyl resins, and the bonding performance of the base coating and the injection mold is enhanced.

[0031] The bottom coating layer in the present invention contains silicon-oxygen bonds, and the surface coating layer contains organic carbon-fluorine bonds. By coating separately and then polymerizing, the phase separation after blending of different molecular segments with poor compatibility is avoided. In the wear-resistant coating, the organic fluorine in the surface coating layer has low surface energy and high strength, which can ensure the fluidity of the plastic melt in the injection mold during use and facilitate demoulding; while the organic silicon segments in the bottom coating layer are soft and tough, which can reduce the internal stress of the coating layer when impacted by external forces and avoid cracking. After curing, the two complement each other and improve the performance of the coating. In addition, it should be noted that when preparing the acrylic modified silicone resin, in order to avoid the complete reaction of the epoxy group, the present invention controls the esterification rate to 50%, that is, tetraepoxysiloxane and α-methyl acrylic acid are reacted at a molar ratio of epoxy and carboxyl groups of 2:1. The prepared acrylic modified silicone resin can be subjected to photothermal dual curing, thereby achieving the effect to be achieved by the present invention. DETAILED DESCRIPTION

[0032] Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative work shall fall within the scope of protection of the present invention.

[0033] Materials used in the present invention and their sources: perfluoropolyether diol (Mn = 2000) is from Fuzhou Taipuda New Materials Co., Ltd.; boron nitride is from Jiangsu Xianfeng Nanomaterials Technology Co., Ltd., item number 102414; photoinitiator 2959 is from Nanjing Milan Chemical Co., Ltd.; epoxy resin E51 is from Hebei Linyuan Fine Chemical Co., Ltd.; the curing agent is a polyetheramine modified curing agent, from Suzhou Hengst Industrial Co., Ltd., item number 4026; the defoaming agent is from Jiangsu Tengda Additive Co., Ltd., item number T-118; the epoxy diluent is from Guangzhou Wei Chuang High-tech Materials Technology Co., Ltd., item number WE-6690.

[0034] Example 1: An injection mold modified with a wear-resistant coating and a preparation process thereof, comprising the following steps:

[0035] Step 1:

[0036] S11: Mix 2,4,6,8-tetramethylcyclotetrasiloxane and allyl glycidyl ether in a molar ratio of 1:4, heat the system to 50°C, stir for 5 minutes, add KARSTEDT catalyst, stir until the temperature stabilizes, and continue the reaction for 3 hours to obtain tetraepoxysiloxane;

[0037] S12: taking tetraepoxysiloxane and heating it to 85°C, mixing α-methacrylic acid, catalyst benzyltriethylammonium chloride, and polymerization inhibitor p-hydroxyanisole, and adding the mixture dropwise to the tetraepoxysiloxane, controlling the addition of the mixture to be completed within 30 minutes; after the addition, heating it to 100°C and reacting for 2 hours to obtain an acrylic acid-modified silicone resin; wherein the tetraepoxysiloxane and α-methacrylic acid react at a molar ratio of epoxy group to carboxyl group of 2:1;

[0038] Step 2:

[0039] S21: Boron nitride was added to isopropanol to prepare a suspension with a concentration of 3 g / L, and ultrasonically vibrated at a power of 200 W for 24 hours. The suspension was centrifuged at 3000 rpm for 10 minutes, and the upper layer of the suspension was collected. The suspension was then centrifuged at 8000 rpm for 10 minutes, and the upper layer of the suspension was collected and air-dried to obtain exfoliated boron nitride.

[0040] S22: 5 g of exfoliated boron nitride was dispersed in deionized water, the pH was adjusted to 8 using tris(hydroxymethyl)aminomethane, 3 g of ethyl orthosilicate was added for hydrolysis for 6 h, and then aged for 1 h, and 0.25 g of 3-mercaptopropyltrimethoxysilane was added; the mixture was stirred for 3 h and filtered, and the filtrate was washed three times with deionized water and ethanol, respectively, to obtain silica-modified boron nitride powder;

[0041] Step 3:

[0042] S31: Perfluoropolyether diol and isophorone diisocyanate were mixed in a hydroxyl group to isocyanate group molar ratio of 2:1, dibutyltin dilaurate was used as a catalyst, the temperature was raised to 70° C. for reaction for 2 h, and the mixture was cooled to obtain a polyurethane prepolymer;

[0043] S32: Glycidol was added to a polyurethane prepolymer at a molar ratio of 1:1 between hydroxyl group and isocyanate group at 40°C, and the mixture was reacted at 70°C for 1 hour using dibutyltin dilaurate as a catalyst to obtain an epoxy-terminated fluorinated polyurethane prepolymer;

[0044] Step 4:

[0045] S41: Select an injection mold made of aluminum alloy, vertically cross-grind the surface of the injection mold with sandpaper for 5 minutes, clean the surface with clean water, and then soak the injection mold in a 0.2 mol / L hydrochloric acid solution and a 0.2 mol / L sodium hydroxide solution for 3 minutes, respectively; clean with acetone to remove surface impurities, and apply a mixture of silane coupling agent KH550, ethanol, and deionized water in a weight ratio of 20:72:8 to the surface of the injection mold, and then dry at 100° C. for 1 hour to obtain a pretreated injection mold;

[0046] S42: Acrylic modified silicone resin, photoinitiator, curing agent, silica modified boron nitride powder, and acetone were mixed in a weight ratio of 100:3:50:3:100, and coated on the surface of the pretreated injection mold at 20 mW / cm 2 After UV curing for 30 seconds, the film was dried by air blast at 50°C to obtain a base coating with a thickness of 500 μm.

[0047] S43: 20 g of epoxy-terminated fluorinated polyurethane prepolymer, 80 g of epoxy resin E51, 38 g of curing agent, 10 g of defoaming agent, and 13 g of epoxy diluent were mixed and applied on the base coating. The mixture was cured at 100° C. for 1 h to obtain a surface coating with a thickness of 100 μm.

[0048] Example 2: An injection mold modified with a wear-resistant coating and a preparation process thereof, comprising the following steps:

[0049] Step 1:

[0050] S11: Mix 2,4,6,8-tetramethylcyclotetrasiloxane and allyl glycidyl ether in a molar ratio of 1:4, heat the system to 55°C, stir for 8 minutes, add KARSTEDT catalyst, stir until the temperature stabilizes, and continue the reaction for 4 hours to obtain tetraepoxysiloxane;

[0051] S12: Take tetraepoxysiloxane and heat it to 90°C, mix α-methacrylic acid, catalyst benzyltriethylammonium chloride, and polymerization inhibitor p-hydroxyanisole, and add the mixture dropwise to the tetraepoxysiloxane, controlling the addition of the mixture to be completed within 45 minutes; after the addition, heat it to 105°C and react for 2.5 hours to obtain an acrylic acid-modified silicone resin; wherein the tetraepoxysiloxane and α-methacrylic acid react at a molar ratio of epoxy group to carboxyl group of 2:1;

[0052] Step 2:

[0053] S21: Boron nitride was added to isopropanol to prepare a suspension with a concentration of 3 g / L, and ultrasonically vibrated at a power of 250 W for 24 hours. The suspension was centrifuged at 3500 rpm for 13 minutes, and the upper layer of the suspension was collected. The suspension was then centrifuged at 9000 rpm for 12 minutes, and the upper layer of the suspension was collected and air-dried to obtain exfoliated boron nitride.

[0054] S22: 5 g of exfoliated boron nitride was dispersed in deionized water, the pH was adjusted to 8.5 using tris(hydroxymethyl)aminomethane, 3 g of ethyl orthosilicate was added for hydrolysis for 6 h, and then aged for 2 h, and 0.25 g of 3-mercaptopropyltrimethoxysilane was added; the mixture was stirred for 3.5 h and filtered, and the filtrate was washed three times with deionized water and ethanol, respectively, to obtain silica-modified boron nitride powder;

[0055] Step 3:

[0056] S31: Perfluoropolyether diol and isophorone diisocyanate were mixed in a hydroxyl group to isocyanate group molar ratio of 2:1, dibutyltin dilaurate was used as a catalyst, the temperature was raised to 75° C. for reaction for 3 h, and the mixture was cooled to obtain a polyurethane prepolymer;

[0057] S32: Glycidol was added to a polyurethane prepolymer at a molar ratio of 1:1 between hydroxyl and isocyanate groups at 45°C, and the mixture was reacted at 75°C for 1.5 hours using dibutyltin dilaurate as a catalyst to obtain an epoxy-terminated fluorinated polyurethane prepolymer.

[0058] Step 4:

[0059] S41: Select an injection mold made of aluminum alloy, vertically cross-grind the surface of the injection mold with sandpaper for 5 minutes, clean the surface with clean water, and then soak the injection mold in a 0.2 mol / L hydrochloric acid solution and a 0.2 mol / L sodium hydroxide solution for 3 minutes, respectively; clean with acetone to remove surface impurities, and apply a mixture of silane coupling agent KH550, ethanol, and deionized water in a weight ratio of 20:72:8 to the surface of the injection mold, and then dry at 110° C. for 1.5 hours to obtain a pretreated injection mold;

[0060] S42: Acrylic modified silicone resin, photoinitiator, curing agent, silica modified boron nitride powder, and acetone were mixed in a weight ratio of 100:3:50:5:100, and coated on the surface of the pre-treated injection mold at 25 mW / cm 2 After UV curing for 60 seconds, the film was dried by air blast at 55°C to obtain a base coating with a thickness of 500 μm.

[0061] S43: 25 g of epoxy-terminated fluorinated polyurethane prepolymer, 75 g of epoxy resin E51, 38 g of curing agent, 10 g of defoaming agent, and 13 g of epoxy diluent were mixed and applied on the base coating. The mixture was cured at 105° C. for 1.5 h to obtain a surface coating with a thickness of 100 μm.

[0062] Example 3: An injection mold modified with a wear-resistant coating and a preparation process thereof, comprising the following steps:

[0063] Step 1:

[0064] S11: Mix 2,4,6,8-tetramethylcyclotetrasiloxane and allyl glycidyl ether in a molar ratio of 1:4, heat the system to 60°C, stir for 10 minutes, add KARSTEDT catalyst, stir until the temperature stabilizes, and continue the reaction for 5 hours to obtain tetraepoxysiloxane;

[0065] S12: Take tetraepoxysiloxane and heat it to 95°C, mix α-methacrylic acid, catalyst benzyltriethylammonium chloride, and polymerization inhibitor p-hydroxyanisole, and add the mixture dropwise to the tetraepoxysiloxane, controlling the addition of the mixture to be completed within 60 minutes; after the addition, heat it to 110°C and react for 3 hours to obtain an acrylic acid-modified silicone resin; wherein the tetraepoxysiloxane and α-methacrylic acid react at a molar ratio of epoxy group to carboxyl group of 2:1;

[0066] Step 2:

[0067] S21: Boron nitride was added to isopropanol to prepare a suspension with a concentration of 3 g / L, and ultrasonically vibrated at a power of 300 W for 24 hours. The suspension was centrifuged at 4000 rpm for 15 minutes, and the upper layer of the suspension was collected. The suspension was then centrifuged at 10000 rpm for 15 minutes, and the upper layer of the suspension was collected and air-dried to obtain the exfoliated boron nitride.

[0068] S22: 5 g of exfoliated boron nitride was dispersed in deionized water, the pH was adjusted to 8.5 using tris(hydroxymethyl)aminomethane, 3 g of ethyl orthosilicate was added for hydrolysis for 6 h, and then aged for 3 h, and 0.25 g of 3-mercaptopropyltrimethoxysilane was added; the mixture was stirred for 4 h and filtered, and the filtrate was washed three times with deionized water and ethanol, respectively, to obtain silica-modified boron nitride powder;

[0069] Step 3:

[0070] S31: Perfluoropolyether diol and isophorone diisocyanate were mixed in a hydroxyl group to isocyanate group molar ratio of 2:1, dibutyltin dilaurate was used as a catalyst, the temperature was raised to 80° C. for reaction for 4 h, and the mixture was cooled to obtain a polyurethane prepolymer;

[0071] S32: Glycidol was added to a polyurethane prepolymer at a molar ratio of 1:1 between hydroxyl group and isocyanate group at 50°C, and the mixture was reacted at 80°C for 2 h using dibutyltin dilaurate as a catalyst to obtain an epoxy-terminated fluorinated polyurethane prepolymer;

[0072] Step 4:

[0073] S41: Select an injection mold made of aluminum alloy, vertically cross-grind the surface of the injection mold with sandpaper for 5 minutes, clean the surface with clean water, and then soak the injection mold in a 0.2 mol / L hydrochloric acid solution and a 0.2 mol / L sodium hydroxide solution for 3 minutes in sequence; clean with acetone to remove surface impurities, and apply a mixture of silane coupling agent KH550, ethanol, and deionized water in a weight ratio of 20:72:8 to the surface of the injection mold, and then dry at 120° C. for 2 hours to obtain a pretreated injection mold;

[0074] S42: acrylic modified silicone resin, photoinitiator, curing agent, silica modified boron nitride powder, and acetone were mixed in a weight ratio of 100:3:50:8:100, and coated on the surface of the pre-treated injection mold at 30 mW / cm 2 After UV curing for 90 seconds, the film was dried by air blast at 60°C to obtain a base coating with a thickness of 500 μm.

[0075] S43: 30 g of epoxy-terminated fluorinated polyurethane prepolymer, 70 g of epoxy resin E51, 38 g of curing agent, 10 g of defoaming agent, and 13 g of epoxy diluent were mixed and applied on the base coating. The mixture was cured at 120° C. for 2 h to obtain a surface coating with a thickness of 100 μm.

[0076] Comparative Example 1: 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane was used instead of tetraepoxysiloxane, and the other parameters were the same as those in Example 1.

[0077] Step 1:

[0078] 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane was heated to 85°C, α-methacrylic acid, catalyst benzyltriethylammonium chloride, and polymerization inhibitor p-hydroxyanisole were mixed, and then added dropwise to tetraepoxysiloxane, with the mixture added dropwise within 30 minutes. After the addition, the temperature was raised to 100°C and reacted for 2 hours to obtain an acrylic acid-modified resin; wherein, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane and α-methacrylic acid were reacted in a molar ratio of epoxy group to carboxyl group of 2:1;

[0079] Step 2:

[0080] S21: Boron nitride was added to isopropanol to prepare a suspension with a concentration of 3 g / L, and ultrasonically vibrated at a power of 200 W for 24 hours. The suspension was centrifuged at 3000 rpm for 10 minutes, and the upper layer of the suspension was collected. The suspension was then centrifuged at 8000 rpm for 10 minutes, and the upper layer of the suspension was collected and air-dried to obtain exfoliated boron nitride.

[0081] S22: 5 g of exfoliated boron nitride was dispersed in deionized water, the pH was adjusted to 8 using tris(hydroxymethyl)aminomethane, 3 g of ethyl orthosilicate was added for hydrolysis for 6 h, and then aged for 1 h, and 0.25 g of 3-mercaptopropyltrimethoxysilane was added; the mixture was stirred for 3 h and filtered, and the filtrate was washed three times with deionized water and ethanol, respectively, to obtain silica-modified boron nitride powder;

[0082] Step 3:

[0083] S31: Perfluoropolyether diol and isophorone diisocyanate were mixed in a hydroxyl group to isocyanate group molar ratio of 2:1, dibutyltin dilaurate was used as a catalyst, the temperature was raised to 70° C. for reaction for 2 h, and the mixture was cooled to obtain a polyurethane prepolymer;

[0084] S32: Glycidol was added to a polyurethane prepolymer at a molar ratio of 1:1 between hydroxyl group and isocyanate group at 40°C, and the mixture was reacted at 70°C for 1 hour using dibutyltin dilaurate as a catalyst to obtain an epoxy-terminated fluorinated polyurethane prepolymer;

[0085] Step 4:

[0086] S41: Select an injection mold made of aluminum alloy, vertically cross-grind the surface of the injection mold with sandpaper for 5 minutes, clean the surface with clean water, and then soak the injection mold in a 0.2 mol / L hydrochloric acid solution and a 0.2 mol / L sodium hydroxide solution for 3 minutes, respectively; clean with acetone to remove surface impurities, and apply a mixture of silane coupling agent KH550, ethanol, and deionized water in a weight ratio of 20:72:8 to the surface of the injection mold, and then dry at 100° C. for 1 hour to obtain a pretreated injection mold;

[0087] S42: acrylic modified resin, photoinitiator, curing agent, silica modified boron nitride powder, and acetone were mixed in a weight ratio of 100:3:50:3:100, and coated on the surface of the pretreated injection mold at 20 mW / cm 2 After UV curing for 30 seconds, the film was dried by air blast at 50°C to obtain a base coating with a thickness of 500 μm.

[0088] S43: 20 g of epoxy-terminated fluorinated polyurethane prepolymer, 80 g of epoxy resin E51, 38 g of curing agent, 10 g of defoaming agent, and 13 g of epoxy diluent were mixed and applied on the base coating. The mixture was cured at 100° C. for 1 h to obtain a surface coating with a thickness of 100 μm.

[0089] Comparative Example 2: No surface coating was applied, and the remaining parameters were the same as those in Example 2.

[0090] Step 1:

[0091] S11: Mix 2,4,6,8-tetramethylcyclotetrasiloxane and allyl glycidyl ether in a molar ratio of 1:4, heat the system to 55°C, stir for 8 minutes, add KARSTEDT catalyst, stir until the temperature stabilizes, and continue the reaction for 4 hours to obtain tetraepoxysiloxane;

[0092] S12: Take tetraepoxysiloxane and heat it to 90°C, mix α-methacrylic acid, catalyst benzyltriethylammonium chloride, and polymerization inhibitor p-hydroxyanisole, and add the mixture dropwise to the tetraepoxysiloxane, controlling the addition of the mixture to be completed within 45 minutes; after the addition, heat it to 105°C and react for 2.5 hours to obtain an acrylic acid-modified silicone resin; wherein the tetraepoxysiloxane and α-methacrylic acid react at a molar ratio of epoxy group to carboxyl group of 2:1;

[0093] Step 2:

[0094] S21: Boron nitride was added to isopropanol to prepare a suspension with a concentration of 3 g / L, and ultrasonically vibrated at a power of 250 W for 24 hours. The suspension was centrifuged at 3500 rpm for 13 minutes, and the upper layer of the suspension was collected. The suspension was then centrifuged at 9000 rpm for 12 minutes, and the upper layer of the suspension was collected and air-dried to obtain exfoliated boron nitride.

[0095] S22: 5 g of exfoliated boron nitride was dispersed in deionized water, the pH was adjusted to 8.5 using tris(hydroxymethyl)aminomethane, 3 g of ethyl orthosilicate was added for hydrolysis for 6 h, and then aged for 2 h, and 0.25 g of 3-mercaptopropyltrimethoxysilane was added; the mixture was stirred for 3.5 h and filtered, and the filtrate was washed three times with deionized water and ethanol, respectively, to obtain silica-modified boron nitride powder;

[0096] Step 3:

[0097] S31: The surface of the injection mold was vertically cross-polished with sandpaper for 5 minutes, the surface was washed with clean water, and then the injection mold was soaked in a 0.2 mol / L hydrochloric acid solution and a 0.2 mol / L sodium hydroxide solution for 3 minutes, respectively; surface impurities were removed by washing with acetone, and a mixture of silane coupling agent KH550, ethanol, and deionized water in a weight ratio of 20:72:8 was applied to the surface of the injection mold, and then dried at 110° C. for 1.5 hours to obtain a pretreated injection mold;

[0098] S32: Mix acrylic modified silicone resin, photoinitiator, curing agent, silica modified boron nitride powder and acetone in a weight ratio of 100:3:50:5:100, apply it on the surface of the pre-treated injection mold, and heat it at 25mW / cm 2 After UV curing for 60 seconds, the film was dried by air blast at 55° C. to obtain a base coating with a thickness of 600 μm.

[0099] Comparative Example 3: The tetraepoxysiloxane and α-methacrylic acid in S12 were reacted at a molar ratio of epoxy to carboxyl of 1:1, and the other parameters were the same as those in Example 3.

[0100] Step 1:

[0101] S11: Mix 2,4,6,8-tetramethylcyclotetrasiloxane and allyl glycidyl ether in a molar ratio of 1:4, heat the system to 60°C, stir for 10 minutes, add KARSTEDT catalyst, stir until the temperature stabilizes, and continue the reaction for 5 hours to obtain tetraepoxysiloxane;

[0102] S12: Take tetraepoxysiloxane and heat it to 95°C, mix α-methacrylic acid, catalyst benzyltriethylammonium chloride, and polymerization inhibitor p-hydroxyanisole, and add the mixture dropwise to the tetraepoxysiloxane, controlling the addition of the mixture to be completed within 60 minutes; after the addition, heat it to 110°C and react for 3 hours to obtain an acrylic acid-modified silicone resin; wherein the tetraepoxysiloxane and α-methacrylic acid react at a molar ratio of epoxy group to carboxyl group of 1:1;

[0103] Step 2:

[0104] S21: Boron nitride was added to isopropanol to prepare a suspension with a concentration of 3 g / L, and ultrasonically vibrated at a power of 300 W for 24 hours. The suspension was centrifuged at 4000 rpm for 15 minutes, and the upper layer of the suspension was collected. The suspension was then centrifuged at 10000 rpm for 15 minutes, and the upper layer of the suspension was collected and air-dried to obtain the exfoliated boron nitride.

[0105] S22: 5 g of exfoliated boron nitride was dispersed in deionized water, the pH was adjusted to 8.5 using tris(hydroxymethyl)aminomethane, 3 g of ethyl orthosilicate was added for hydrolysis for 6 h, and then aged for 3 h, and 0.25 g of 3-mercaptopropyltrimethoxysilane was added; the mixture was stirred for 4 h and filtered, and the filtrate was washed three times with deionized water and ethanol, respectively, to obtain silica-modified boron nitride powder;

[0106] Step 3:

[0107] S31: Perfluoropolyether diol and isophorone diisocyanate were mixed in a hydroxyl group to isocyanate group molar ratio of 2:1, dibutyltin dilaurate was used as a catalyst, the temperature was raised to 80° C. for reaction for 4 h, and the mixture was cooled to obtain a polyurethane prepolymer;

[0108] S32: Glycidol was added to a polyurethane prepolymer at a molar ratio of 1:1 between hydroxyl group and isocyanate group at 50°C, and the mixture was reacted at 80°C for 2 h using dibutyltin dilaurate as a catalyst to obtain an epoxy-terminated fluorinated polyurethane prepolymer;

[0109] Step 4:

[0110] S41: Select an injection mold made of aluminum alloy, vertically cross-grind the surface of the injection mold with sandpaper for 5 minutes, clean the surface with clean water, and then soak the injection mold in a 0.2 mol / L hydrochloric acid solution and a 0.2 mol / L sodium hydroxide solution for 3 minutes in sequence; clean with acetone to remove surface impurities, and apply a mixture of silane coupling agent KH550, ethanol, and deionized water in a weight ratio of 20:72:8 to the surface of the injection mold, and then dry at 120° C. for 2 hours to obtain a pretreated injection mold;

[0111] S42: acrylic modified silicone resin, photoinitiator, curing agent, silica modified boron nitride powder, and acetone were mixed in a weight ratio of 100:3:50:8:100, and coated on the surface of the pre-treated injection mold at 30 mW / cm 2 After UV curing for 90 seconds, the film was dried by air blast at 60°C to obtain a base coating with a thickness of 500 μm.

[0112] S43: 30 g of epoxy-terminated fluorinated polyurethane prepolymer, 70 g of epoxy resin E51, 38 g of curing agent, 10 g of defoaming agent, and 13 g of epoxy diluent were mixed and applied on the base coating. The mixture was cured at 120° C. for 2 h to obtain a surface coating with a thickness of 100 μm.

[0113] Experiment: According to the schemes in Examples 1 to 3 and Comparative Examples 1 to 3, the surface of an aluminum alloy (3A12) substrate with a size of 10 cm×10 cm×0.5 mm was pretreated and a wear-resistant coating was prepared, and then the performance of the coating was tested.

[0114] The test method is:

[0115] Friction resistance test: A friction tester is used to rub a random 3cm×3cm area on the sample surface. The friction probe is loaded with 200g. After 1000 frictions, a salt spray corrosion test is performed on the sample using a 5% sodium chloride saline solution. The test temperature is 50°C and the test time is 120h. The wear resistance of the coating is characterized by comparing the rust conditions of the substrate in the friction area and the non-friction area. If obvious rust occurs in the friction area of ​​the substrate relative to the non-friction area, it indicates that the coating has poor wear resistance. Otherwise, the wear resistance is good.

[0116] Impact resistance test: According to GB / T 1732-2020 "Determination of impact resistance of paint films", impact tests were carried out using an impact testing machine with a hammer mass of 1 kg. Each group of samples was tested 3 times. An electric spark leak detector was used to detect whether the samples had cracks. Finally, the impact resistance was evaluated based on the maximum stroke.

[0117] Surface hydrophilicity and hydrophobicity test: The surface water contact angle test was performed using an optical contact angle meter.

[0118] The test results are shown in Table 1 below:

[0119] Table 1. Wear-resistant coating performance test results

[0120] project Wear resistance Impact height / cm contact angle Example 1 No obvious rust in the friction area 61 122° Example 2 No obvious rust in the friction area 63 125° Example 3 No obvious rust in the friction area 64 127° Comparative Example 1 No obvious rust in the friction area 58 122° Comparative Example 2 Visible rust in the friction area 57 108° Comparative Example 3 Visible rust in the friction area 64 126°

[0121] Conclusion: The data of Examples 1 to 3 show that the coating prepared by the present invention has good performance. The data of Example 1 and Comparative Example 1 show that the base coating prepared with siloxane can effectively improve the toughness of the coating, thereby improving the impact strength; the data of Example 2 and Comparative Example 2 show that the surface coating in Example 2 can improve the surface hydrophobicity, reduce the surface energy, and has high strength, and has a good protective effect on the substrate. In Comparative Example 2, although the silicon-containing coating has good toughness, it has low strength and lacks the protection of the surface coating, and the wear resistance and impact strength are significantly reduced; the data of Example 3 and Comparative Example 3 show that the adhesion between the base coating and the substrate in Example 3 is good, and after thermal curing, it is cross-linked with the surface coating, and the coating protection effect is obvious. In Comparative Example 3, the adhesion between the base coating and the substrate is poor, and it cannot be cross-linked with the surface coating. Therefore, after the friction test, the coating falls off, the substrate lacks the protection of the coating, and rust occurs in the salt spray test.

[0122] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art will be able to modify the technical solutions described in the aforementioned embodiments or substitute equivalents for some of the technical features. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A process for preparing an injection mold modified with a wear-resistant coating, characterized in that: The following steps are involved: Step 1: Select an aluminum alloy injection mold, sand the surface of the injection mold vertically and cross-grind with sandpaper for 5 minutes, clean the surface with clean water, and then soak the injection mold in hydrochloric acid solution and sodium hydroxide solution in sequence for 3 to 5 minutes; clean with acetone to remove surface impurities, apply a mixture of silane coupling agent KH550, ethanol, and deionized water to the surface of the injection mold, and then dry it at 100 to 120°C for 1 to 2 hours to obtain a pretreated injection mold; Step 2: After mixing acrylic modified silicone resin, photoinitiator, curing agent, silica modified boron nitride powder, and acetone, apply it on the surface of the pretreated injection mold, cure it under 20-30 mW / cm2 ultraviolet light for 30-90 seconds, and then air dry it at 50-60°C to obtain a base coating with a thickness of 300-500 μm; Step 3: Mix the epoxy-terminated fluorinated polyurethane prepolymer, epoxy resin E51, curing agent, defoaming agent, and epoxy diluent, apply the mixture on the base coating, and cure at 100-120° C. for 1-2 hours to obtain a surface coating with a thickness of 100-200 μm; In step 2, the preparation method of the acrylic modified silicone resin includes the following steps: taking 2,4,6,8-tetramethylcyclotetrasiloxane and allyl glycidyl ether, mixing, heating to a system temperature of 50-60°C, stirring for 5-10 minutes, adding a KARSTEDT catalyst, stirring until the temperature stabilizes, and continuing the reaction for 3-5 hours to obtain a tetraepoxysiloxane; taking the tetraepoxysiloxane and heating it to 85-95°C, mixing α-methylacrylic acid, a catalyst benzyltriethylammonium chloride, and a polymerization inhibitor p-hydroxyanisole, and adding the mixture dropwise to the tetraepoxysiloxane, controlling the addition of the mixture within 30-60 minutes; after the addition is completed, heating to 100-110°C and reacting for 2-3 hours to obtain an acrylic modified silicone resin; In step 2, the preparation method of silica-modified boron nitride powder comprises the following steps: S1: adding boron nitride to isopropyl alcohol to obtain a suspension with a concentration of 1 to 3 g / L, ultrasonically oscillating at a power of 200 to 300 W for 24 hours, centrifuging at 3000 to 4000 r / min for 10 to 15 minutes, taking the upper layer of the suspension, and then centrifuging at 8000 to 10000 r / min for 10 to 15 minutes, taking the upper layer of the suspension, and air-drying. Dry to obtain exfoliated boron nitride; S2: Take 3 to 5 parts of exfoliated boron nitride by weight and disperse them in deionized water, use trishydroxymethylaminomethane to adjust the pH to 8 to 8.5, add 2.5 to 3 parts of ethyl orthosilicate to hydrolyze for 6 hours and then age for 1 to 2 hours, add 0.2 to 0.28 parts of 3-mercaptopropyltrimethoxysilane; stir the reaction for 3 to 4 hours and then filter, take the filtrate and wash it with deionized water and ethanol for 3 to 5 times respectively to obtain silica-modified boron nitride powder.

2. The process for preparing a wear-resistant coating modified injection mold according to claim 1, characterized in that: In step 1, the concentration of the hydrochloric acid solution is 0.2 to 0.25 mol / L; the concentration of the sodium hydroxide solution is 0.2 to 0.25 mol / L; and the weight ratio of the silane coupling agent KH550, ethanol, and deionized water is 20:(70 to 75):(5 to 10).

3. The process for preparing a wear-resistant coating modified injection mold according to claim 1, characterized in that: In step 2, acrylic modified silicone resin, photoinitiator, curing agent, silica modified boron nitride powder, and acetone are mixed in a weight ratio of (100-120): (3-5): (46-54): (3-8):

100.

4. The process for preparing a wear-resistant coating modified injection mold according to claim 1, characterized in that: 2,4,6,8-tetramethylcyclotetrasiloxane and allyl glycidyl ether react at a molar ratio of 1:4; tetraepoxysiloxane and α-methacrylic acid react at a molar ratio of epoxy group to carboxyl group of 2:

1.

5. The process for preparing a wear-resistant coating modified injection mold according to claim 1, characterized in that: In step 3, the amount of each component used, by weight, is 20 to 30 parts of epoxy-terminated fluorine-containing polyurethane prepolymer, 70 to 80 parts of epoxy resin E51, 35 to 40 parts of curing agent, 8 to 13 parts of defoaming agent, and 10 to 15 parts of epoxy diluent.

6. The process for preparing a wear-resistant coating modified injection mold according to claim 1, characterized in that: In step 3, the preparation method of the epoxy-terminated fluorine-containing polyurethane prepolymer includes the following steps: mixing perfluoropolyether diol and isophorone diisocyanate, using dibutyltin dilaurate as a catalyst, heating to 70-80°C for reaction for 2-4 hours, and cooling to obtain a polyurethane prepolymer; adding glycidol to the polyurethane prepolymer at 40-50°C, using dibutyltin dilaurate as a catalyst, and reacting at 70-80°C for 1-2 hours to obtain an epoxy-terminated fluorine-containing polyurethane prepolymer.

7. The process for preparing a wear-resistant coating modified injection mold according to claim 6, characterized in that: Perfluoropolyether diol and isophorone diisocyanate are mixed at a molar ratio of 2:1 between hydroxyl group and isocyanate group; and glycidol is added to the polyurethane prepolymer at a molar ratio of 1:1 between hydroxyl group and isocyanate group.

8. The injection mold prepared by the preparation process according to any one of claims 1 to 7.