An Extrusion Port Die Coating for Automotive Sealing Strips and Its Preparation Method

Abstract

Since this application relates to the field of coatings, it specifically discloses a coating for spraying on the extrusion port die of automotive sealing strips and its preparation method. The coating for spraying on the extrusion port die of automotive sealing strips includes a modified polyurethane resin. The preparation method of the modified polyurethane resin is as follows: dehydrate polyols and hydroxyl-terminated polyether modified silicone oil to obtain a dehydrated product; add isocyanate and a catalyst to the dehydrated product, raise the temperature, and carry out a heat preservation reaction to obtain a polyurethane product; add chain extender A to the polyurethane product, and then add acetone to obtain a primary chain-extended product; add a neutralizing agent to the primary chain-extended product, disperse to obtain a neutralized product; add water to the neutralized product, disperse, then add chain extender B and a silane coupling agent, disperse, and carry out rotary evaporation to obtain the product. The coating for spraying on the extrusion port die of automotive sealing strips in this application can be used for spraying sealing strips, and it has the advantage of strong adhesion, and can adhere to the surface of untreated rubber, thus omitting the surface treatment link in the processing process.

Description

Technical Field

[0001] This application relates to the field of coatings, and more specifically, to a spray coating for the extrusion port die of automotive sealing strips and a preparation method thereof. Background Art

[0002] Automotive sealing strips are used for the connection and sealing of movable parts of automotive doors and windows as well as the connection between metal and non-metal parts. The material of the sealing strip is generally rubber. Due to the large frictional resistance between rubber and the vehicle body and insufficient sealing performance, a coating is usually formed by spraying a coating on the rubber surface during the processing to reduce the wear between the sealing strip and the vehicle body and improve the sealing performance such as waterproofing of the sealing strip.

[0003] Spraying is generally achieved in an extrusion continuous vulcanization production process, which includes the following steps: feeding, extrusion, high-temperature shaping, microwave vulcanization, vulcanization, secondary vulcanization, tertiary vulcanization, plasma surface treatment, spraying the coating, primary curing, secondary curing, cooling, and shaping.

[0004] Due to the low surface energy of rubber, the current coating has insufficient adhesion and is therefore difficult to adhere to the rubber surface to form a coating. Therefore, surface treatment is required first to increase the surface energy of rubber, and then the coating is cured into a coating through two bakings. Although the above process can complete spraying, there are many steps, thus reducing the process efficiency. Summary of the Invention

[0005] In order to improve the process efficiency, this application provides a spray coating for the extrusion port die of automotive sealing strips and a preparation method thereof, wherein the coating has high adhesion and can be adhered to the surface of rubber without surface treatment, thereby omitting the surface treatment link in the production process of the sealing strip and improving the efficiency.

[0006] In the first aspect, this application provides a spray coating for the extrusion port die of automotive sealing strips, adopting the following technical solutions:

[0007] A spray coating for the extrusion port die of automotive sealing strips, comprising the following components in parts by weight:

[0008] 40 - 50 parts of modified polyurethane resin;

[0009] 10 - 15 parts of waterborne flatting resin;

[0010] 5 - 6 parts of film-forming aid;

[0011] 15 - 20 parts of blocked isocyanate curing agent;

[0012] 5 - 10 parts of water; The preparation method of the modified polyurethane resin is as follows:

[0013] a. Dehydrate polyol and hydroxyl-terminated polyether modified silicone oil to obtain a dehydrated product;

[0014] b. Add isocyanate and a catalyst to the dehydration product, raise the temperature, keep the temperature for reaction, and obtain a polyurethane product;

[0015] c. Add chain extender A to the polyurethane product, react, then add acetone and disperse to obtain a primary chain-extended product;

[0016] d. Add a neutralizing agent to the primary chain-extended product and disperse to obtain a neutralized product;

[0017] e. Add water to the neutralized product and disperse, then add chain extender B and a silane coupling agent, disperse, and perform rotary evaporation to obtain the product.

[0018] By adopting the above technical solutions: The modified polyurethane resin and the waterborne matting resin have characteristics such as good toughness, softness, and high strength. As the film-forming base material of the coating, after being paired with a blocked isocyanate curing agent, the prepared coating can coexist at room temperature for a long time, and the curing agent releases isocyanate groups at high temperature to achieve crosslinking and curing.

[0019] Among them, the modified polyurethane resin has a special structural design. It is graft-modified with terminal hydroxyl polyether silicone oil to improve the surface smoothness and high-temperature resistance of the polyurethane. During the chain extension stage, self-crosslinking and external crosslinking are achieved with the participation of chain extender A and chain extender B to form a three-dimensional network structure, improving the wear resistance of the polyurethane. The grafting with a silane coupling agent enables the polyurethane to be connected to the silicone rubber through chemical bonds, improving the adhesion strength to the rubber, and a modified polyurethane resin with good adhesion to rubber is prepared. After testing, when using a waterborne polyurethane, the coating peeling grade is as high as five levels, while the coating peeling grade prepared with an equal amount of the modified polyurethane is only two levels, indicating that the modified polyurethane resin improves the adhesion of the coating on the rubber surface.

[0020] With the aid of the above coating, the coating can be attached to the surface of the rubber without surface treatment, thus simplifying the surface treatment link in the processing technology of the sealing strip, not only saving resources but also greatly improving the efficiency.

[0021] Optionally, the modified polyurethane resin, by weight fraction, comprises 100 - 130 parts of polyol and 30 - 40 parts of isocyanate.

[0022] By adopting the above technical solutions: When the dosages of the polyol and the isocyanate are within the above ranges, the prepolymer has a higher molecular weight, the viscosity of the system decreases, the rheology of the coating is good; the coating peeling grade is low and the abrasion decreases slightly, and the coating performance is excellent.

[0023] Optionally, the weight ratio of the terminal hydroxyl polyether modified silicone oil to the isocyanate is (10 - 15):35.

[0024] Optionally, the chain extender A is composed of trimethylolpropane, 1,6 - hexanediol, and dimethylolpropionic acid in a weight ratio of (4 - 8):(8 - 12):(6 - 10).

[0025] Optionally, the polyol is composed of polytetrahydrofuran ether diol, polycarbonate diol, and polycaprolactone diol in a weight ratio of (35 - 45):(30 - 40):(35 - 45).

[0026] Optionally, the specific steps of dehydration are as follows: dehydrate the polyol and the hydroxyl - terminated polyether modified silicone oil at a temperature of 110 - 130 °C and a vacuum degree of 0.09 - 0.10 MPa for 0.8 - 1.2 h.

[0027] By adopting the above - mentioned technical solution: when the dehydration conditions are within the above - mentioned range, it can not only ensure the dehydration effect, promote the better effect of modified polyurethane, but also ensure a higher dehydration efficiency.

[0028] Optionally, during the process of adding water to the neutralization product in step e, furfural residue is also added.

[0029] By adopting the above - mentioned technical solution: it is further found that after testing, when furfural residue is not added, the peeling grade of the coating is grade one and the abrasion is 23.7 mg, while after adding furfural residue, the peeling grade of the coating drops to grade zero and the abrasion is significantly reduced to 17.6 mg, indicating that adding furfural residue can significantly improve the wear resistance and adhesion of the coating.

[0030] Analyzing the reason may be that: when the temperature of the coating friction surface rises, it will aggravate the wear of the coating, while the furfural residue releases water when heated, which plays a role in reducing the heat accumulated on the friction surface and improving the wear resistance; and the acidic substances in the furfural residue cause the surface of the polyurethane to be hydroxylated, improving the hydrophilicity, thus improving the grafting effect of the silane coupling agent, and further improving the adhesion of the modified polyurethane resin, so the adhesion of the prepared coating is stronger.

[0031] Optionally, the weight ratio of the added amount of the furfural residue to water is (0.4 - 0.8):10.

[0032] By adopting the above - mentioned technical solution: when the added amount of the furfural residue is within the above - mentioned range, due to the proper ratio, the performance of the modified polyurethane is the best, the peeling grade of the prepared coating is low, and the abrasion is as low as 14.4 - 15.3 mg, and the comprehensive performance of the prepared coating reaches the best.

[0033] In the second aspect, the present application provides a preparation method of a coating for spraying on the extrusion port die of an automotive sealing strip, adopting the following technical solution:

[0034] A preparation method of a coating for spraying on the extrusion port die of an automotive sealing strip, the specific steps of which are as follows:

[0035] It is obtained by adding an aqueous matting resin, a film-forming aid, water, and a blocked isocyanate curing agent to a modified polyurethane resin and mixing them.

[0036] In summary, the present application has the following beneficial effects:

[0037] 1. In the present application, a modified polyurethane is used to form a three-dimensional network structure through two-step chain extension, improving the wear resistance of the polyurethane. After grafting a silane coupling agent onto the polyurethane, a chemical bond connection is formed between the polyurethane and the silicone rubber, improving the bonding strength with the rubber, and thus improving the adhesion of the coating to the rubber surface. Therefore, it is not necessary to perform surface treatment on the rubber before spraying the rubber, reducing the processing steps of the sealing strip and improving the efficiency.

[0038] 2. In the preparation process of the modified polyurethane in the present application, furfural residue is added. On the one hand, the furfural residue plays a role in cooling during the friction process, making the modified polyurethane more wear-resistant. On the other hand, it improves the grafting effect of the silane coupling agent on the surface of the polyurethane, making the modified polyurethane more adhesive, thereby further improving the wear resistance and adhesion of the coating. Specific Embodiments

[0039] The following further elaborates on the present application with reference to examples.

[0040] Preparation Examples 1 - 7

[0041] A modified polyurethane resin, its components and their corresponding weights are shown in Table 1, and it is obtained through the following steps:

[0042] a. Dehydrate polyol (polytetrahydrofuran ether diol) and hydroxyl-terminated polyether modified silicone oil at a temperature of 120 °C and a vacuum degree of 0.095 MPa for 1 h to obtain a dehydrated product.

[0043] b. Cool the dehydrated product to 55 °C, add isophorone diisocyanate and an organic bismuth catalyst dropwise, and raise the temperature to 95 °C and keep the temperature for reaction for 1.5 h to obtain a polyurethane product.

[0044] c. Add chain extender A (a mixture of trimethylolpropane and 1,6 - hexanediol) to the polyurethane product, react for 3 h, and then add acetone and stir and mix for 10 min to obtain a primary chain - extended product.

[0045] d. Cool the primary chain - extended product to 40 °C, stir and mix at a rotation speed of 2000 rpm for 20 min, then add a neutralizing agent (N,N - dimethylethanolamine), and stir and mix at a rotation speed of 1000 rpm for 30 min to obtain a neutralized product.

[0046] e. Add water accounting for 50% of the total water amount to the neutralization product, shear and disperse for 10 min, then add the remaining water, shear and disperse for 10 min, add chain extender B (isophorone diamine) and silane coupling agent (N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane), adjust to pH 8.0 with hydrochloric acid and sodium hydroxide aqueous solution, stir and mix for 20 min, and rotary evaporate for 20 min to obtain.

[0047] The hydroxyl-terminated polyether modified silicone oil was purchased from Guangzhou Yinuo Chemical Technology Co., Ltd., with the product number 8427.

[0048] Table 1 Components and their weights (kg) in Preparation Examples 1-7

[0049]

[0050] It should be noted that the conditions in the above process can be selected within the following ranges, and this selection does not have a great impact on the performance of the modified polyurethane resin. For example, the temperature after cooling of the dehydrated product is within the range of 50-60 °C, specifically 50 °C, 52 °C, 54 °C, 56 °C, 58 °C, 60 °C, the temperature increase after adding the organobismuth catalyst is within the range of 80-90 °C, specifically 80 °C, 82 °C, 84 °C, 86 °C, 88 °C, 90 °C, and the temperature after cooling of the primary chain-extended product is within the range of 35-45 °C, specifically 35 °C, 37 °C, 39 °C, 41 °C, 43 °C, 45 °C.

[0051] Preparation Examples 8-10

[0052] A modified polyurethane resin, different from Preparation Example 6 in that the chain extender A is different, using a mixture of equal amounts of trimethylolpropane, 1,6-hexanediol, and dimethylolpropionic acid instead of the mixture of trimethylolpropane and 1,6-hexanediol. The weight ratios of the components in chain extender A are as follows:

[0053] Preparation Example 8

[0054] The weight ratio of trimethylolpropane, 1,6-hexanediol, and dimethylolpropionic acid is 4:8:6.

[0055] Preparation Example 9

[0056] The weight ratio of trimethylolpropane, 1,6-hexanediol, and dimethylolpropionic acid is 6:10:8.

[0057] Preparation Example 10

[0058] The weight ratio of trimethylolpropane, 1,6-hexanediol, and dimethylolpropionic acid is 8:12:10.

[0059] Preparation Examples 11-13

[0060] A modified polyurethane resin, which is different from Preparation Example 9 in that the polyol is different. A mixture of equal amounts of polytetrahydrofuran ether diol, polycarbonate diol, and polycaprolactone diol is used instead of polytetrahydrofuran ether diol. The weight ratios of the components in the polyol are as follows:

[0061] Preparation Example 11

[0062] The weight ratio of polytetrahydrofuran ether diol, polycarbonate diol, and polycaprolactone diol is 35:30:35.

[0063] Preparation Example 12

[0064] The weight ratio of polytetrahydrofuran ether diol, polycarbonate diol, and polycaprolactone diol is 40:35:40.

[0065] Preparation Example 13

[0066] The weight ratio of polytetrahydrofuran ether diol, polycarbonate diol, and polycaprolactone diol is 45:40:45.

[0067] Preparation Examples 14 - 15

[0068] A modified polyurethane resin, which is different from Preparation Example 12 in that the specific steps of dehydration are as follows:

[0069] Preparation Example 14

[0070] The polyol and the hydroxyl - terminated polyether modified silicone oil are dehydrated for 0.8 h under the conditions of a temperature of 110 °C and a vacuum degree of 0.09 MPa to obtain a dehydrated product.

[0071] Preparation Example 15

[0072] The polyol and the hydroxyl - terminated polyether modified silicone oil are dehydrated for 1.2 h under the conditions of a temperature of 130 °C and a vacuum degree of 0.10 MPa to obtain a dehydrated product.

[0073] Preparation Examples 16 - 19

[0074] A modified polyurethane resin, which is different from Preparation Example 12 in that in step e, during the process of adding water to the neutralized product, ball - milled furfural residue is also added. The furfural residue is purchased from Rizhao Yuanli Biotechnology Co., Ltd., and the product number is 3061146. The ball - milling method is: ball - mill the furfural residue for 40 min and pass through a 1600 - mesh sieve to obtain the ball - milled furfural residue.

[0075] The addition amount of the ball - milled furfural residue and the weight ratio of water are as follows:

[0076] Preparation Example 16

[0077] The weight ratio of the ball - milled furfural residue to water is 0.3:10.

[0078] Preparation Example 17

[0079] The weight ratio of the ball-milled furfural residue to water is 0.4:10.

[0080] Preparation Example 18

[0081] The weight ratio of the ball-milled furfural residue to water is 0.6:10.

[0082] Preparation Example 19

[0083] The weight ratio of the ball-milled furfural residue to water is 0.8:10.

[0084] Examples 1-3, Comparative Examples 1-2

[0085] A spray coating for the extrusion port die of an automotive sealing strip, each component and its corresponding weight are shown in Table 2, and it is obtained through the following steps:

[0086] Add water-based flatting resin, film-forming aid, dispersant (BASF EFKA PU4061), water, leveling agent (BYK 381), blocked isocyanate curing agent, and polyether-modified polydimethylsiloxane to the modified polyurethane resin (prepared from Preparation Example 1), and stir and mix at a speed of 800 rpm for 60 min;

[0087] Then add yellow fluorescent agent, black color paste, and silicone defoamer, stir and mix at a speed of 600 rpm for 60 min, and let it stand for 1 h to obtain.

[0088] The water-based flatting resin is a water-based polyurethane flatting resin purchased from Hefei Lingzheng Environmental Protection Technology Co., Ltd., grade 1; the film-forming aid is purchased from Shanghai Zhenlishi Network Technology Co., Ltd., product number DIB; the blocked isocyanate curing agent is purchased from Covestro, model Imprafix 2794XP; the polyether-modified polydimethylsiloxane is purchased from Anhui Aiyota Silicone Oil Co., Ltd., model IOTA 1291; the black color paste is purchased from Dongguan Guangsiyuan Polyurethane Materials Co., Ltd., model SK-102.

[0089] Table 2 Components and weights (kg) in Examples 1-3, Comparative Examples 1-2

[0090]

[0091]

[0092] Comparative Example 3

[0093] An aqueous polyurethane coating, which is different from that of Example 1 in that an equal amount of aqueous polyurethane resin is used instead of modified polyurethane resin. The aqueous polyurethane resin is purchased from Wuhan Jixin Yibang Biotechnology Co., Ltd. and its model is 9009-54-5.

[0094] Examples 4 - 21

[0095] An automotive sealing strip extrusion port die spraying coating, which is different from that of Example 2 in that the usage of modified polyurethane resin refers to Table 3, but the dosage of modified polyurethane in the automotive sealing strip extrusion port die spraying coating remains unchanged.

[0096] Table 3 Usage of modified polyurethane resin in Examples 4 - 21

[0097] Example 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 Preparation Example 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19

[0098] Performance testing of automotive sealing strip extrusion port die spraying coating

[0099] The automotive sealing strip extrusion port die spraying coatings prepared in the examples and comparative examples are subjected to the following performance tests, and the test results are recorded in Table 4.

[0100] Testing method

[0101] 1. Adhesion: Samples are prepared according to GB / T 9286-1998, boiled in water at 95°C for 24h, and then tested and graded according to GB / T9286-1998. The smaller the peeling grade, the better the adhesion of the coating.

[0102] 2. Abrasion resistance: According to the standard GB / T 1768-2006, using an ASR-5612 type Taber abrasion tester, under the test conditions of a 750g load, 1000 revolutions, and a CS10# abrasion grinding wheel, the sample is polished, and the abrasion of the coating is recorded. The lower the abrasion, the better the wear resistance of the coating.

[0103] Sample preparation: The coating is made into a coating film sheet with a thickness of (1.5 ± 0.2) mm using a film applicator, cured for 96h under the conditions of a temperature of (25 ± 2)°C and a relative humidity of (50 ± 10)%, demolded, turned over, and then cured for another 72h to obtain the sample.

[0104] Table 4 Performance test results

[0105]

[0106]

[0107] As can be seen from Table 4, in Example 1, due to the use of the modified polyurethane resin prepared in Preparation Example 1, the coating peeling grade of the prepared coating is grade two, while in Comparative Example 3, due to the use of the same amount of commercially available waterborne polyurethane resin, the coating peeling grade of the prepared coating is grade five, indicating that the modified polyurethane resin can enhance the adhesion of the coating.

[0108] The differences between Examples 2-3, Comparative Examples 1-2 and Example 1 lie in the different usage amounts of each component in the coating. As can be seen from Table 4, when the usage amounts of each component are within the ranges of Examples 1-3, the adhesion and abrasion resistance of the coating are both excellent.

[0109] The differences between Examples 18-21 and Example 14 are that furfural residue is further added in step e of the preparation process of the modified polyurethane. The peeling area of the prepared coating is homogenously significantly reduced from grade one when furfural residue is not added to grade zero, and the abrasion is significantly reduced from 23.7 mg when not added to 17.6 mg. Especially when the addition amount of furfural residue is within the ranges of Examples 19-21, the abrasion is as low as 14.4-15.3 mg, and the adhesion of the coating is strong and the abrasion resistance is remarkable. The reasons for this may be as follows:

[0110] 1. Furfural residue releases water during the friction process to cool the friction surface, reducing the problem of decreased abrasion resistance caused by temperature rise, thus improving the abrasion resistance; 2. The acidic substances in furfural residue introduce hydrophilic groups, improving the grafting effect of the silane coupling agent on the surface of polyurethane, thereby enhancing the chemical bond connection between the coating and the rubber and improving the adhesion.

[0111] This specific embodiment is only an explanation of the present application, and it is not a limitation of the present application. Those skilled in the art can make modifications without creative contributions to this embodiment according to needs after reading this specification, but as long as it is within the scope of the claims of the present application, it is protected by the patent law.

Claims

1. An extrusion port die coating for automotive sealing strips, characterized in that, It comprises components in the following parts by weight: 40 - 50 parts of modified polyurethane resin; 10 - 15 parts of waterborne matting resin; 5 - 6 parts of film-forming auxiliary; 15 - 20 parts of blocked isocyanate curing agent; 5 - 10 parts of polyether-modified polydimethylsiloxane; 5 - 10 parts of water; The preparation method of the modified polyurethane resin is as follows: a. Dehydrate polyol and hydroxyl-terminated polyether-modified silicone oil to obtain a dehydrated product; b. Add isocyanate and a catalyst to the dehydrated product, raise the temperature, and carry out a heat preservation reaction to obtain a polyurethane product; c. Add chain extender A to the polyurethane product, react, then add acetone and disperse to obtain a primary chain-extended product; d. Add a neutralizing agent to the primary chain-extended product and disperse to obtain a neutralized product; e. Add water to the neutralized product and disperse, then add isophorone diamine and silane coupling agent, disperse, and carry out rotary evaporation to obtain the product; The chain extender A is composed of trimethylolpropane, 1,6-hexanediol, and dimethylolpropionic acid in a weight ratio of (4 - 8):(8 - 12):(6 - 10); In step e, furfural residue is also added during the process of adding water to the neutralized product.

2. A coating sprayed on the extrusion port die of an automotive sealing strip according to claim 1, characterized in that: The modified polyurethane resin, by weight fraction, comprises 100 - 130 parts of polyol and 30 - 40 parts of isocyanate.

3. A coating sprayed on the extrusion port die of an automotive sealing strip according to claim 1, characterized in that: The weight ratio of the hydroxyl-terminated polyether-modified silicone oil to the isocyanate is (10 - 15):

35.

4. A coating sprayed on the extrusion port die of an automotive sealing strip according to claim 1, characterized in that: The polyol is composed of polytetrahydrofuran ether diol, polycarbonate diol, and polycaprolactone diol in a weight ratio of (35 - 45):(30 - 40):(35 - 45).

5. A coating sprayed on the extrusion port die of an automotive sealing strip according to claim 1, characterized in that: The specific steps of the dehydration are as follows: Dehydrate polyol and hydroxyl-terminated polyether-modified silicone oil under the conditions of a temperature of 110 - 130 °C and a vacuum degree of 0.09 - 0.10 MPa for 0.8 - 1.2 h.

6. A coating sprayed on the extrusion port die of an automotive sealing strip according to claim 1, characterized in that: The addition amount of the furfural residue and the weight ratio of water is (0.4 - 0.8):

10.

7. A method for preparing a coating sprayed on the extrusion port die of an automotive sealing strip according to any one of claims 1-6, characterized in that, The specific steps are as follows: Add waterborne matting resin, film-forming auxiliary, dispersant, water, leveling agent, blocked isocyanate curing agent, and polyether-modified polydimethylsiloxane to the modified polyurethane resin and mix; then add fluorescent agent, color paste, and organosilicon defoamer, mix, and stand to obtain the product.

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