Impregnating composition for aluminum castings

Abstract

The present invention relates to an impregnating composition for aluminum castings and, to an impregnating composition comprising a first acrylic monomer, a first acrylic oligomer with a molecular weight greater than that of the first acrylic monomer, and a second acrylic monomer with a ring structure having a bulky alkyl group. The impregnating composition according to the present invention has excellent micropore-penetration ability, and has a low shrinkage rate after curing, and thus can reduce the frequency of impregnation for preventing defects in micropores during impregnation and can minimize the generation of organic waste liquid.

Description

Impregnating composition for aluminum castings

[0001] The present invention relates to an impregnating composition for aluminum castings, and more particularly, to an impregnating composition comprising a first acrylic monomer, a first acrylic oligomer having a molecular weight greater than that of the first acrylic monomer, and a second acrylic monomer having a ring structure having a bulky alkyl group.

[0002] Impregnation technology refers to a technique that fills and hardens micropores, which are inherently formed during the casting process but are invisible to the naked eye. Impregnation agents are used to fill the pores in materials such as cast products, sintered metals, and aluminum alloys, thereby ensuring airtightness.

[0003] These impregnating agents have been mainly used since the development of inorganic products in the 1930s, with the development of methacrylic resins in 1985, and have been used until 2023, and generally use monomers with excellent micropore penetration.

[0004] However, when using mainly monomers, it is known that the shrinkage rate of the impregnating agent after the curing process is high, and to overcome this, the impregnation process is repeated at least 2 to 3 times to resolve the micropore defects caused by the shrinkage of the impregnating agent, but this lengthens the process time and causes other problems such as the emission of hazardous substances.

[0005] In relation to this, various studies are being conducted in the industry to apply impregnants with different types and composition ratios of impregnants, but the state is not yet satisfactory.

[0006] The object of the present invention is to solve the aforementioned problems and to develop an impregnating composition that not only has high penetration efficiency into micropores existing in aluminum castings but also has low shrinkage after hardening, so that a single impregnation is sufficient.

[0007] In addition, the object of the present invention is to provide an impregnating composition capable of reducing the amount of impregnating agent used and minimizing the generation of harmful substances, and other purposes not mentioned herein will be readily understood by those skilled in the art.

[0008] In order to solve the above problem, the present invention provides an impregnating composition comprising a first acrylic monomer, a first acrylic oligomer having a molecular weight greater than that of the first acrylic monomer, a second acrylic monomer having a ring structure containing a bulky alkyl group, and an initiator.

[0009] According to one embodiment of the present invention, the composition is characterized in that the first acrylic monomer is 40 to 60 wt%, the second acrylic monomer is 20 to 35 wt%, and the first acrylic oligomer is 10 to 25 wt% based on the total weight of the composition.

[0010] According to one embodiment of the present invention, the first acrylic monomer is one selected from 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, 4-hydroxybutyl acrylate, and glycerol monomethacrylate, and the second acrylic monomer is one selected from glycidyl methacrylate, tetrahydrofurfuryl acrylate, cyclohexyl acrylate, isobonyl acrylate, and cyclic trimethylolpropane formal. It is characterized in that the first acrylic oligomer is one selected from acrylate (Cyclic trimethylolpropane formal acrylate) and trimethyl cyclohexyl acrylate, and the first acrylic oligomer is an epoxyacrylate oligomer.

[0011] According to one embodiment of the present invention, the initiator is characterized in that it is 0.1 to 2 wt% based on the total weight of the composition.

[0012] According to another embodiment of the present invention, the composition is characterized in that it additionally comprises at least one component selected from the group consisting of an antioxidant, a light stabilizer, and a surfactant.

[0013] The impregnating composition according to the present invention can reduce the amount of impregnating agent used and the amount of wastewater generated by reducing the number of impregnation processes from 2 to 3 times to 1 time by enhancing impregnation characteristics such as reducing the leakage rate through improving the shrinkage rate after curing.

[0014] This application claims the benefit of priority from Korean Patent Application No. 10-2023-0111786, filed August 25, 2023, the entire contents of which are incorporated herein by reference.

[0015] While the present invention may be susceptible to various modifications and embodiments, it should be understood that this does not limit the invention to a specific embodiment, but rather encompasses all modifications, equivalents, and alternatives falling within the spirit and technical scope of the present invention. In describing the present invention, detailed descriptions of related known technologies will be omitted if they are deemed to obscure the gist of the present invention.

[0016] The terminology used in this application is only used to describe specific embodiments and is not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly indicates otherwise. In this application, it should be understood that the terms "comprise" or "have" indicate the presence of a feature, number, step, operation, component, part, or combination thereof described in the specification, but do not exclude in advance the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0017] Terms such as first, second, etc. may be used to describe various components, but these components should not be limited by these terms. These terms are used solely to distinguish one component from another.

[0018] Hereinafter, the present invention will be described in detail with reference to embodiments according to the present invention, and when describing with reference to the attached drawings, identical or corresponding components are given the same reference numerals regardless of the drawing symbols, and redundant descriptions thereof will be omitted.

[0019] The impregnating agent according to the present invention uses a first acrylic oligomer having a molecular weight greater than that of the first acrylic monomer type to solve the shrinkage problem of the first acrylic monomer and the impregnating agent, and additionally includes a second acrylic monomer having a ring structure containing a bulky alkyl group.

[0020] While conventional impregnating agents are made up of a hydroxy-based acrylate monomer as a main component and are cured by a thermal initiator, the present invention is different in that it is composed of a structure in which a first acrylic monomer (hydroxy-based acrylate), a second acrylic monomer (cycloaliphatic), and a first acrylic oligomer (acrylate-based oligomer) are mixed and cured by a thermal initiator.

[0021] That is, the first acrylic monomer is a hydroxy-based acrylate monomer that is added to lower the viscosity of the impregnating agent and facilitate washing after curing. Types that can be used as the first acrylic monomer include 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, 4-hydroxybutyl acrylate, and glycerol monomethacrylate.

[0022] The first acrylic monomer of the present invention is preferably included in an amount of 40 to 60 wt% relative to the total composition. If the first acrylic monomer is included in an amount less than 40 wt%, the viscosity of the impregnating agent increases, resulting in poor workability. Furthermore, if the first acrylic monomer is included in an amount exceeding 60 wt%, the impregnation properties are weakened due to increased shrinkage after curing.

[0023] Next, the present invention includes a second acrylic monomer having a cyclic structure containing a bulky alkyl group that serves to lower the viscosity of the impregnating agent and reduce shrinkage after curing, and preferably, a cyclo aliphatic acrylate can be used.

[0024] Types that can be used as the second acrylic monomer include glycidyl methacrylate, tetrahydrofurfuryl acrylate, cyclohexyl acrylate, isobonyl acrylate, cyclic trimethylolpropane formal acrylate, and trimethyl cyclohexyl acrylate.

[0025] The second acrylic monomer of the present invention is preferably included in an amount of 20 to 35 wt% relative to the total composition. If the second acrylic monomer is included in an amount of less than 20 wt%, shrinkage after curing increases. Furthermore, if the second acrylic monomer is included in an amount exceeding 35 wt%, cleaning after impregnation curing becomes difficult.

[0026] Next, the present invention includes a first acrylic oligomer that enhances the adhesion to the wall surface within the micropores of the impregnating agent and reduces the shrinkage rate of the impregnating agent after curing, and preferably, an epoxy acrylate oligomer can be used.

[0027] The first acrylic oligomer of the present invention is preferably comprised in an amount of 10 to 25 wt% relative to the total weight of the composition. If the first acrylic oligomer is comprised in an amount less than 10 wt%, the impregnating agent may have weak adhesion to the substrate after penetration into the micropores and hardening, resulting in easy detachment. In addition, if the first acrylic oligomer is comprised in an amount exceeding 25 wt%, the viscosity of the impregnating agent increases, resulting in poor workability and poor washability.

[0028] In addition to the main components, the present impregnating composition additionally contains an initiator that causes a polymerization reaction. An example of the initiator is preferably 2,2-Azobisisobutyronitrile (AIBN), but the type thereof is not limited.

[0029] It is preferable that the initiator of the present invention be included in an amount of 0.1 to 2 wt% relative to the total amount of the entire composition. If the initiator is included in an amount less than 0.1 wt%, it takes a long time for the curing reaction to be completed, and if it is included in an amount exceeding 2 wt%, the physical properties of the composition, such as adhesion and shrinkage, deteriorate.

[0030] In addition, the impregnation composition according to the present invention may additionally include at least one selected from the group consisting of an antioxidant, a light stabilizer, and a surfactant as an additive.

[0031] <Example 1. Oligomer Synthesis>

[0032] In a 1L 4-neck flask, 374g of YD-128 (Kukdo Chemical), a bisphenol A type epoxy, 130g of acrylic acid, and 50ppm of hydroquinone, a polymerization inhibitor, were mixed based on the total mixing ratio, and then the reaction temperature was increased to 110℃. At the same temperature, 0.1g of triethylamine, a reaction catalyst, was injected and the reaction was maintained until the acid value became 1 or less, thereby producing an epoxy acrylate oligomer.

[0033] <Example 2. Preparation of impregnating agent A>

[0034] In a 1 L flask container, 50 g of 2-Hydroxy ethyl acrylate, 30 g of glycidyl methacrylate, 20 g of the epoxy acrylate oligomer synthesized in Example 1, and 0.2 g of AIBN (2,2-Azobisisobytyronitrile), an initiator, were mixed with a stirrer to prepare impregnating agent A.

[0035] <Example 3. Preparation of impregnating agent B>

[0036] In a 1 L flask container, 50 g of 2-Hydroxy ethyl acrylate, 30 g of Tetrahydrofurfuryl Acrylate, 20 g of the epoxy acrylate oligomer synthesized in Example 1, and 0.2 g of AIBN (2,2-Azobisisobytyronitrile), an initiator, were mixed with a stirrer to prepare impregnating agent B.

[0037] <Comparative Example 1. Preparation of impregnating agent C>

[0038] Impregnating agent C was prepared by mixing 62.5 g of 2-Hydroxy ethyl acrylate, 37.5 g of glycidyl methacrylate, and 0.2 g of AIBN (2,2-Azobisisobytyronitrile), an initiator, in a 1 L flask container using a stirrer.

[0039] <Comparative Example 2. Preparation of Impregnant D>

[0040] Impregnating agent D was prepared by mixing 62.5 g of 2-Hydroxy ethyl acrylate, 37.5 g of Tetrahydrofurfuryl Acrylate, and 0.2 g of AIBN (2,2-Azobisisobytyronitrile), an initiator, in a 1 L flask container using a stirrer.

[0041] <Experimental Example 1. Shrinkage and Leak Test>

[0042] The shrinkage rate and leak test were evaluated for the impregnants A to D manufactured through the examples and comparative examples described above, and the results are shown in Table 1. Here, the shrinkage rate (%) is calculated by substituting the liquid specific gravity and solid specific gravity into the calculation formula as shown in the formula below to obtain the shrinkage rate (%).

[0043] Shrinkage (%) = [(Liquid specific gravity - Solid specific gravity) / (Liquid specific gravity)]*100

[0044] The leak (leakage rate) test method is to install a jig for each impregnated specimen on the leak test equipment and then apply air pressure to conduct the experiment. If the leak allowance is 0.3 kPa / min or less under the air pressure condition of 300 kPa / min, it is judged as PASS.

[0045] Classification Preliminary Comparison Example Impregnation Type Impregnation A Impregnation B Impregnation C Impregnation D Shrinkage (%) 89.09 1.07 9.08 3.0 Leak Test (kPa / min) 0.19 0.15 0.44 0.35

[0046] Looking at the results in Table 1, there was a difference in shrinkage rate depending on the application and presence of oligomer and the presence or absence of cycloaliphatic monomer, and the lower the shrinkage rate, the more satisfactory the leak leakage allowance was shown in the leak test evaluation. In other words, it was confirmed that the impregnating agent manufactured by additionally mixing an acrylic oligomer and a monomer having a ring structure, as in the present invention, had a relatively good shrinkage rate even after curing, and thus could be effective in reducing the actual number of impregnations.

[0047] Although the present invention has been described above with reference to one embodiment, it will be understood by those skilled in the art that various modifications and changes can be made to the present invention without departing from the spirit and scope of the present invention as set forth in the claims below.

[0048] It is hereby disclosed that the present invention is the result of research conducted with the assistance of the following government-supported project.

[0049] 1. Assignment ID: 1425156351

[0050] 2. Assignment Number: S3159832

[0051] 3. Ministry Name: Ministry of SMEs and Startups

[0052] 4. Project Management Agency Name: Small and Medium Business Technology Information Promotion Agency

[0053] 5. Research Project Name: Small and Medium Enterprise Technology Innovation Development Project (Export-Oriented)

[0054] 6. Research Project Name: Development of a Domestically Produced, Eco-Friendly Chemical-Based Impregnation System for Defect-Free Aluminum Castings for Electric Hydrogen Vehicles

[0055] 7. Contribution rate: 1 / 1

[0056] 8. Project execution agency: InnoF&C Co., Ltd.

[0057] 9. Research Period: September 27, 2021 - September 26, 2025

Claims

1. First acrylic monomer; A second acrylic monomer having a ring structure containing a bulky alkyl group; A first acrylic oligomer having a molecular weight greater than that of the first acrylic monomer; and characterized by including an initiator Impregnating composition for aluminum castings.

2. In paragraph 1, The composition is characterized in that the first acrylic monomer is 40 to 60 wt%, the second acrylic monomer is 20 to 35 wt%, and the first acrylic oligomer is 10 to 25 wt% based on the total weight of the composition. Impregnating composition for aluminum castings.

3. In paragraph 1, The first acrylic monomer is one selected from 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, 4-hydroxybutyl acrylate, and glycerol monomethacrylate. The second acrylic monomer is one selected from glycidyl methacrylate, tetrahydrofurfuryl acrylate, cyclohexyl acrylate, isobonyl acrylate, cyclic trimethylolpropane formal acrylate, and trimethyl cyclohexyl acrylate. The above first acrylic oligomer is characterized in that it is an epoxyacrylate oligomer. Impregnating composition for aluminum castings.

4. In paragraph 1, The above initiator is characterized in that it is 0.1 to 2 wt% based on the total weight of the composition. Impregnating composition for aluminum castings.

5. In paragraph 1, The composition is characterized in that it additionally comprises at least one component selected from the group consisting of an antioxidant, a light stabilizer, and a surfactant. Impregnating composition for aluminum castings.