Preparation method of modified HDI trimer curing agent and application thereof

Abstract

The application discloses a preparation method of a modified HDI trimer curing agent and application thereof, and comprises the following steps: mixing and reacting HDI trimer and a hydroxyl-terminated polypropylene to generate the modified HDI trimer curing agent. The method uses HDI trimer and a hydroxyl-terminated polypropylene as raw materials to prepare the curing agent, and can be applied to plastic paint of a PP base material. Compared with traditional plastic paint using a curing agent, the modified curing agent is used in combination with a main paint, does not need to additionally increase a special base paint, can have very good adhesion and water resistance on a polypropylene (PP) base material, and it is found that the paint film has very good alcohol resistance, and is very suitable for the plastic paint field, and is especially suitable for plastic paint applied to a PP base material, for example, automobile bumper paint.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of polymer chemistry, and particularly relates to a preparation method of a modified HDI trimer curing agent and application thereof. BACKGROUND

[0002] Due to the advantages of light weight, simple manufacturing process, corrosion resistance, and injection molding compared with metal materials, plastics can replace metal materials in many places. For example, polyolefins and other plastics have been widely used as raw materials for injection molding of automobile parts, engineering plastics, toys, etc. Among them, polypropylene (PP) plastic has become the mainstream of automobile bumper material due to its low material cost, high toughness and other characteristics. However, in the actual coating production of automobile bumpers, the surface of the polypropylene (PP) substrate is non-polar and has low surface energy, poor adhesion performance, and the addition of modified materials of PP material is relatively chaotic, which leads to the phenomenon of surface paint peeling even after the surface pretreatment or the use of flame treatment to improve the adhesion performance of the substrate surface.

[0003] At present, the effective solution to the problem of paint peeling on the surface of the PP substrate is to increase a special primer or a PP surface treatment agent on the PP substrate to improve the adhesion between the PP substrate and the paint. However, this method increases the spraying process and leads to high cost and low efficiency. SUMMARY

[0004] The present application aims to overcome the shortcomings of poor paint adhesion of the existing polypropylene (PP) substrate and the need for additional special primer. A preparation method of a modified HDI trimer curing agent is provided. When the modified HDI trimer curing agent is used to prepare a coating for a PP substrate, it can have very good adhesion on the PP substrate without the need for additional special primer, improve the water resistance of the coating, and unexpectedly improve the alcohol resistance of the coating.

[0005] To solve the above technical problems, the present application provides the following technical solutions:

[0006] A preparation method of a modified HDI trimer curing agent, comprising the following steps:

[0007] Mixing and reacting HDI trimer and hydroxyl-terminated polypropylene to generate a modified HDI trimer curing agent.

[0008] The hydroxyl-terminated polypropylene satisfies the general formula (I):

[0009]

[0010] In formula (I), n is any integer from 100 to 100,000.

[0011] The end-hydroxyl polypropylene can be obtained by the method disclosed in the prior art, i.e. the end-hydroxyl polypropylene obtained by catalyzing the polymerization of polypropylene with a metal catalyst and hydrolysis, such as the method disclosed in ZL200410009906.6.

[0012] The HDI trimer is obtained by trimerization of hexamethylene diisocyanate, and contains 15-70wt% of HDI trimer and other polymers in mass fraction.

[0013] The NCO functional group content of the HDI trimer is 20-23%.

[0014] The end-hydroxyl polypropylene is added in an amount of 0.1-10% of the total mass of the HDI trimer and the end-hydroxyl polypropylene, preferably 0.2-2%.

[0015] The reaction temperature is 70-80℃, and the reaction time is 4-5h.

[0016] The modified HDI trimer curing agent prepared by the method contains the structure shown in formula (II):

[0017]

[0018] In formula (II), n is any integer from 100 to 100000.

[0019] The modified HDI trimer curing agent is used for preparing a two-component polyurethane plastic coating.

[0020] A two-component polyurethane coating comprises a hydroxyl-containing acrylic resin and the modified HDI trimer curing agent, and the coating can be prepared by mixing the components.

[0021] Preferably, other additives such as leveling agents can also be added to the two-component polyurethane coating.

[0022] Preferably, a solvent can also be added to the two-component polyurethane coating, and the solvent is selected from one or more of n-butyl acetate, xylene, propylene glycol methyl ether acetate (PMA), etc.

[0023] The application also provides the use of the curing agent for preparing a two-component polyurethane plastic coating, which is particularly suitable for use on PP (polypropylene) materials.

[0024] Compared with the prior art, the application has the following positive effects:

[0025] (1) By using the end hydroxyl polypropylene to modify the HDI trimer, the polypropylene segment is introduced into the structure of the HDI trimer curing agent, and by using the principle of similar molecular structure, the modified curing agent has very good adhesion when used on the polypropylene (PP) substrate, without the need for additional special primer, simplifying the construction process and improving the construction efficiency.

[0026] (2) The non-polar segment of polypropylene is introduced into the system, which greatly improves the water resistance, and it is accidentally found that the alcohol resistance of the coating is also greatly improved. DETAILED DESCRIPTION

[0027] The application will be further illustrated by the following examples, which should be understood that the following examples are only for illustrative purposes and do not constitute any limitation on the scope of the application.

[0028] In this application, % by mass, unless otherwise specified.

[0029] Table 1

[0030]

[0031]

[0032] Example 1

[0033] Preparation of modified HDI trimer curing agent A.

[0034] 100g HDI trimer (Wanhua HT-100), 1g end hydroxyl polypropylene HM512 were added into the reaction kettle, mixed uniformly, heated to 70℃ for 5h. When the NCO value in the system reached about 21wt%, the reaction was stopped, and the modified HDI trimer curing agent A was obtained and placed in a sealed container for use.

[0035] Example 2

[0036] Preparation of modified HDI trimer curing agent B.

[0037] 100g HDI trimer (Wanhua HT-600), 2g end hydroxyl polypropylene HM568 were added into the reaction kettle, mixed uniformly, heated to 70℃ for 5h. When the NCO value in the system reached about 20wt%, the reaction was stopped, and the modified HDI trimer curing agent B was obtained and placed in a sealed container for use.

[0038] Example 3

[0039] Preparation of modified HDI trimer curing agent C.

[0040] Into a reaction kettle, 100 g of HDI trimer (Wanhua HT-600) and 1.5 g of hydroxyl-terminated polypropylene HM512 were added and mixed uniformly, and heated to 70°C for 5 h. When the NCO value of the system reached about 20.5 wt%, the reaction was stopped, and a modified HDI trimer curing agent C was obtained and placed in a sealed container for later use.

[0041] Example 4

[0042] A modified HDI trimer curing agent D was prepared.

[0043] Into a reaction kettle, 100 g of HDI trimer (Wanhua HT-600) and 0.5 g of hydroxyl-terminated polypropylene HM512 were added and mixed uniformly, and heated to 70°C for 5 h. When the NCO value of the system reached about 22.5 wt%, the reaction was stopped, and a modified HDI trimer curing agent D was obtained and placed in a sealed container for later use.

[0044] Example 5

[0045] A modified HDI trimer curing agent E was prepared.

[0046] Into a reaction kettle, 100 g of HDI trimer (Wanhua HT-100) and 0.5 g of hydroxyl-terminated polypropylene HM568 were added and mixed uniformly, and heated to 70°C for 5 h. When the NCO value of the system reached about 21.5 wt%, the reaction was stopped, and a modified HDI trimer curing agent E was obtained and placed in a sealed container for later use.

[0047] Example 6

[0048] A modified HDI trimer curing agent F was prepared.

[0049] Into a reaction kettle, 100 g of HDI trimer (Wanhua HT-100) and 2 g of hydroxyl-terminated polypropylene HM568 were added and mixed uniformly, and heated to 70°C for 5 h. When the NCO value of the system reached about 19.5 wt%, the reaction was stopped, and a modified HDI trimer curing agent F was obtained and placed in a sealed container for later use.

[0050] For example, the following was prepared:

[0051] The modified HDI trimer curing agents prepared in the above examples and the unmodified HDI curing agent HT-100 were used to prepare a plastic paint formulation as follows:

[0052] Table 2

[0053]

[0054] The preparation method of the plastic paint was as follows:

[0055] (1) Take the selected mass of F3060, BYK-306, n-butyl acetate into a beaker, stir at a speed of 500 r / min for 10 min, then take a sample with a scraping plate for testing, and observe whether the coating film surface is uniform and has no obvious defects. Stop stirring to obtain the hydroxyl acrylate component;

[0056] (2) Take the selected mass of the curing agent and stir to form a uniform solution to obtain the curing agent component.

[0057] (3) Slowly add the selected mass of the hydroxyl acrylate resin component to the selected mass of the curing agent component at a stirring speed of 300 r / min, increase the stirring speed to 500 r / min, and stir for 10 min. Then test, spray on a PP substrate, and test the application performance according to the following method.

[0058] Pot life: according to the provisions of GB / T 31416-2015;

[0059] Viscosity: according to the provisions of GB / T 1723-1993; equipment brand: brookfield / Bolife, model: DV-I+prime

[0060] Gloss test: test gloss according to GB / T 9754-2007; equipment brand: BGD, model: BGD 274

[0061] Water resistance test: test water resistance according to GB / T 5209-85 "Determination of Water Resistance of Pigment and Varnish by Immersion Method";

[0062] Pencil hardness test: test pencil hardness according to GB / T 6739-1996 "Pencil Hardness Test Method for Coating Film";

[0063] Impact resistance test: test impact resistance according to GB / T 1732-1993 "Paint Film Impact Resistance Test Method"; equipment brand: BGD, model: BGD 304

[0064] Flexibility test: test flexibility according to GB / T 1731-1993 "Paint Film Flexibility Test Method"; equipment brand: BGD, model: BGD 560

[0065] Adhesion test: according to the provisions of GB / T 5210-2006; equipment brand: BGD, model: BGD 503

[0066] Alcohol resistance test: GB / T 23989-2009, i.e. paint solvent resistance test method; equipment brand: BGD, model: BGD 888 / S

[0067] The specific test results are shown in Table 3:

[0068] Table 3: Performance test results of the plastic coating prepared

[0069]

[0070] From Table 3, it can be seen that the plastic coating prepared in Examples 1-6 has very good adhesion on PP substrate, and the water resistance is greatly improved, and the alcohol resistance of the paint film is also greatly improved, compared with Comparative Formulation 1 and Comparative Formulation 2 using conventional curing agents.

[0071] The above shows that the modified HDI trimer curing agent prepared in the present application has excellent adhesion, excellent water resistance and excellent alcohol resistance on polypropylene (PP) substrate without additional special primer.

[0072] Obviously, the above examples are only examples for the purpose of clarity, and are not limitations on the embodiments. Based on the above description, other different forms of changes or variations can also be made by those of ordinary skill in the art. It is not necessary and impossible to enumerate all the embodiments. The obvious changes or variations derived therefrom are still within the protection scope of the present application.

Claims

1. A method for preparing a modified HDI trimer curing agent, characterized in that, The method comprises the following steps: mixing and reacting HDI trimer and hydroxyl-terminated polypropylene to form modified HDI trimer curing agent; wherein the hydroxyl-terminated polypropylene has a structure as shown in general formula (I): wherein in formula (I), n is any integer from 100 to 100,000. The modified HDI trimer curing agent comprises a structure as shown in formula (II): wherein in formula (II), n is any integer from 100 to 100,000.

2. The production method according to claim 1, characterized by, The HDI trimer is prepared by trimerization of hexamethylene diisocyanate.

3. The production method according to claim 1, characterized by, The HDI trimer comprises 15-70wt% of HDI trimer and other polymers.

4. The method of claim 1, wherein, The HDI trimer has an NCO functional group content of 20-23%.

5. The preparation method according to claim 1, characterized in that, The hydroxyl-terminated polypropylene is added in an amount of 0.1-10% based on the total mass of the HDI trimer and the hydroxyl-terminated polypropylene.

6. The preparation method according to claim 5, characterized in that, The hydroxyl-terminated polypropylene is added in an amount of 0.2-2% based on the total mass of the HDI trimer and the hydroxyl-terminated polypropylene.

7. The preparation method according to claim 1, characterized in that, The reaction temperature is 70-80℃, and the reaction time is 4-5h.

8. Use of the modified HDI trimer curing agent prepared by the method of any one of claims 1-7 in the preparation of two-component polyurethane plastic coating.

9. The use of claim 8, wherein the coating is used on polypropylene material.

10. A two-component polyurethane coating comprising hydroxyl-containing acrylic resin and the modified HDI trimer curing agent prepared by the method of any one of claims 1-7.

11. The coating of claim 10, wherein the two-component polyurethane coating further comprises a leveling agent and a solvent.

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