Aqueous polymer emulsions and uses thereof

Abstract

The present invention provides an aqueous polymer emulsion having satisfactory resistance to electrochemical deposition properties and good void sealing performance for cast metal or parts co-molded by two different metal materials, comprising at least one (meth)acrylic polymer prepared by at least two monomers comprising at least one alkyl (meth)acrylate and at least one unsaturated carboxylic acid, at least one corrosion inhibitor, and at least one chelating agent, wherein the at least one unsaturated carboxylic acid is present in an amount of less than 3.5 wt % based on the total weight of the monomers.

Description

[Technical field]

[0001] Technical Field The present invention relates to an aqueous polymer emulsion, and in particular to an aqueous polymer emulsion used as an impregnating composition for vacuum impregnation and its use. [Background technology]

[0002] 2. Background of the Invention Metal castings, such as aluminum castings, iron castings, and electronic components co-molded with different metal materials, such as stainless steel and aluminum, usually have many micropores, which can cause leakage problems and are a major obstacle to commercial practicality, especially when such porous parts are used in fluid power systems and other liquid handling applications.

[0003] One way to solve this problem is to disperse the sealant into the holes of the parts by a dispersing machine. This fixed-point dispersion method has many disadvantages, such as changing the dimensions of the parts, affecting the appearance of the parts, and the formed sealant is on the outer surface of the parts, which may be easily damaged when an impact occurs. After damage, the sealant needs to be redispersed, which is costly and time-consuming.

[0004] Vacuum impregnation (VI) technology is an effective means of sealing porous parts without changing their dimensions or functional properties. Vacuum impregnation technology is a technique in which the impregnating agent is infiltrated into the micropores of metal parts or components that are co-molded by at least two different metal materials through a vacuum pressure process. After the vacuum impregnation process is finished, the parts are transferred to the next process, i.e., washing process, drying process, or solidification process, where the impregnating agent forms a sealant that fills the pores, achieving the purpose of sealing and leak-proofing and resistance to high pressure, thereby solving the leakage problem of the parts.

[0005] However, impregnating compositions in the art can deposit on metal substrates, making them difficult to clean and wash. This becomes more serious when parts are co-molded with at least two different metal materials, as electrochemical deposition can occur. In electrochemical deposition, metal ions are released into solution and deposited on the substrate surface. The most common example of an electrochemical mechanism is simple corrosion of a metal in an aqueous solution, where atoms of the metal surface enter the solution as metal ions and electrons are transferred through the metal to a site where they are consumed by the species in contact with the metal to sustain the reaction. In more complex cases, the metal ions form complex ions and migrate into the solution, or combine with other species in the solution to precipitate compounds such as hydroxides, oxides, and sulfides. It is often observed that electrochemical deposition on metal substrate surfaces in aqueous solutions can cause emulsion breakdown and polymer deposition, resulting in the need for large amounts of solvent to clean the parts. In summary, electrochemical deposition of impregnating compositions significantly limits the effectiveness of vacuum impregnation processes in the electronics industry. Summary of the Invention [Problem to be solved by the invention]

[0006] Therefore, there is a need to develop a vacuum impregnable composition that has good resistance to electrochemical deposition on cast metals or parts co-molded with two different metallic materials without losing good pore sealing performance during the vacuum impregnation process. [Means for solving the problem]

[0007] Summary of the Invention In one aspect of the invention, there is provided an aqueous emulsion comprising: (a) at least one (meth)acrylic polymer prepared from at least two monomers comprising at least one alkyl (meth)acrylate and at least one unsaturated carboxylic acid; (b) at least one corrosion inhibitor; and (c) at least one chelating agent; wherein said at least one unsaturated carboxylic acid is present in an amount less than 3.5 weight percent, based on the total weight of monomers.

[0008] In an additional aspect of the present invention, there is provided a solidified product of the aqueous emulsion according to the present invention.

[0009] In an additional aspect of the present invention, a part is provided that includes a solidified product according to the present invention.

[0010] In an additional aspect of the invention, there is provided an electronic device including a component according to the invention.

[0011] In an additional aspect of the present invention, a method for sealing pores (voids) in a component is provided.

[0012] The aqueous polymer emulsion of the present invention penetrates and fills the voids of porous materials, cast metals, or parts co-molded with at least two metallic materials. Using a vacuum process, air is removed from the voids of the part being impregnated and replaced with the components in the emulsion. After cleaning and solidification, the part surface is shiny and almost free of residue or particles.

[0013] In yet another aspect of the present invention there is provided the use of the aqueous polymer emulsion according to the present invention in gap sealing. Effect of the Invention

[0014] The aqueous emulsion of the present invention used as a vacuum impregnation composition features satisfactory electrochemical deposition resistance performance and good pore sealing properties for cast metal or parts co-molded by two different metal materials. Moreover, the aqueous emulsion of the present invention is easy to prepare, and the vacuum impregnation process using this aqueous emulsion is suitable for commercial application. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Detailed Description of the Invention Those skilled in the art will appreciate that the present invention has been described with reference to exemplary embodiments only, and is not intended to limit the broad scope of the present invention. Each aspect thus described may be combined with other aspects, unless expressly indicated to the contrary. In particular, any feature indicated as being preferred or advantageous may be combined with other features or features indicated as being preferred or advantageous.

[0016] In the context of the present invention, unless otherwise specified, the terms used shall be construed in accordance with the following definitions.

[0017] As used herein, unless otherwise stated, the terms "a," "an," and "the" include singular and plural references.

[0018] As used herein, the terms "comprising" and "comprises" are synonymous with "including," "includes," or "containing," and "contains," and are inclusive or open-ended and do not exclude additional, unlisted members, elements, or process steps.

[0019] Unless otherwise specified, the recitation of numerical endpoints includes all numbers and fractions subsumed within the respective ranges, as well as the recited endpoints.

[0020] "Polymer," as used herein and as defined by FW Billmeyer, JR. in Textbook of Polymer Science, second edition, 1971, refers to a relatively large molecule made up of the reaction product of smaller chemical repeating units. Polymers may have structures that are linear, branched, star-shaped, looped, hyperbranched, crosslinked, or combinations thereof; polymers may have a single type of repeating unit (a "homopolymer") or more than one type of repeating unit (a "copolymer"). Copolymers may have the various types of repeating units randomly, sequentially, in blocks, or in other arrangements, or mixtures or combinations thereof.

[0021] As used herein, "polymerization" refers to the process of reacting monomers to form a polymer. In the practice of the present invention, the polymerization process is an aqueous emulsion polymerization. The resulting polymer is synonymously known as a latex or emulsion polymer.

[0022] Molecular weights refer to number average molecular weights (Mn) unless otherwise stated. All molecular weight data are determined by gel permeation chromatography (GPC), e.g. according to DIN 55672, unless otherwise stated.

[0023] The terms (meth)acrylate or (meth)acrylic refer to both acrylate / acrylic and methacrylate / methacrylic.

[0024] All documents cited herein are incorporated by reference in their entirety.

[0025] Unless otherwise defined, all terms used herein, including technical and scientific terms, have the meaning commonly understood by one of ordinary skill in the art to which this invention belongs.

[0026] The present invention relates to (a) at least one (meth)acrylic polymer prepared from at least two monomers comprising at least one alkyl (meth)acrylate and at least one unsaturated carboxylic acid; (b) at least one corrosion inhibitor; and (c) at least one chelating agent; wherein said at least one unsaturated carboxylic acid is present in an amount of less than 3.5% by weight, based on the total weight of monomers. The present invention is directed to an aqueous polymer emulsion comprising:

[0027] (Meth)acrylic polymer According to the present invention, the aqueous polymer emulsion comprises at least one (meth)acrylic polymer prepared by at least two monomers including at least one alkyl (meth)acrylate and at least one unsaturated carboxylic acid, said at least one unsaturated carboxylic acid being present in an amount of less than 3.5% by weight, based on the total weight of the monomers.

[0028] The at least one unsaturated carboxylic acid may be selected from (meth)acrylic acid, crotonic acid, itaconic acid, cinnamic acid, linoleic acid, oleic acid and combinations thereof, preferably (meth)acrylic acid.

[0029] In one preferred embodiment, the at least one unsaturated carboxylic acid is present in the aqueous polymer emulsion in an amount of 3% by weight or less, preferably 0.01% to 3% by weight, more preferably 0.5% to 2.8% by weight, based on the total weight of the monomers. Increasing the amount of unsaturated carboxylic acid can improve the pore-blocking ability of the aqueous polymer emulsion.

[0030] Examples of alkyl (meth)acrylates used in the present invention include C1 to C20 alkyl (meth)acrylates, such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, s-butyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, heptadecyl (meth)acrylate, octadecyl (meth)acrylate, nonadecyl (meth)acrylate, eicosyl (meth)acrylate, and combinations thereof are included, and preferably methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, acrylate, s-butyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate.Preferred are C1-C10 alkyl (meth)acrylates, such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, s-butyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, and isodecyl (meth)acrylate. Such monomers can be used alone or in combination.

[0031] In a preferred embodiment, the at least one alkyl (meth)acrylate is present in the aqueous polymer emulsion in an amount of 35 to 67.5% by weight, preferably 35 to 60% by weight, more preferably 35 to 50% by weight, based on the total weight of monomers.

[0032] Other monomers that can be used as monomers for preparing (meth)acrylic polymers. In one embodiment, the monomers for preparing (meth)acrylic polymers further include at least one other monomer. Such other monomers include (meth)acrylates having at least one hydroxyl group, acrylonitrile, acrylamide, (meth)acrylamide, N-substituted (meth)acrylamides, hydroxyacrylamides, diacetone acrylamide, vinyl esters such as vinyl acetate, vinyl ethers such as isobutyl vinyl ether, styrene, alkyl- or halo-styrenes, N-vinylpyrrolidone, vinyl chloride, vinylidene chloride, diacrylate monomers, silicone monomers, phosphate / polyphosphate monomers and combinations thereof, and preferably (meth)acrylates having at least one hydroxyl group.

[0033] Examples of (meth)acrylates having at least one hydroxyl group in the present invention include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 1,4-cyclohexanedimethanol mono(meth)acrylate, glycerol mono(meth)acrylate, polyethylene glycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, terminal hydroxyl group-containing lactone-modified (meth)acrylate, and combinations thereof, preferably selected from 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and combinations thereof. (Meth)acrylates having at least one hydroxyl group can be used alone or in combination.

[0034] In a preferred embodiment, when at least one (meth)acrylate having at least one hydroxyl group is used to prepare the (meth)acrylic polymer of the present invention, it is present in an amount of 0.5 to 15 wt.%, preferably 0.5 to 10 wt.%, more preferably 0.5 to 6 wt.%, based on the total weight of the monomers.

[0035] In some embodiments, the (meth)acrylic polymer in the present invention has a number average molecular weight (Mn) of 20,000 to 2,000,000 g / mol, preferably 50,000 to 1,000,000 g / mol, and more preferably 100,000 to 500,000 g / mol, as measured by gel permeation chromatography (GPC).

[0036] In some embodiments, the (meth)acrylic polymer in the present invention has a D of 0.1 to 1.0 μm, preferably 0.25 to 0.85 μm, more preferably 0.40 to 0.70 μm, and even more preferably 0.50 to 0.60 μm. 50 It has a grain size.

[0037] Here, the (meth)acrylic polymer "D 50 "Particle size" refers to the median diameter in a volume-based particle size distribution curve obtained by measurement using a laser diffraction particle size analyzer.

[0038] In some embodiments, the (meth)acrylic polymer in the present invention has a glass transition temperature of -40°C to 10°C, preferably -30°C to 0°C, and more preferably -20°C to -10°C.

[0039] Here, the glass transition temperature is determined using a differential scanning calorimeter (TA DSC Q2000) according to the following process: the sample is equilibrated to 40°C, cooled to -80°C for 2 minutes, then heated from -80°C to 60°C at a rate of 10°C per minute, and cooled from 60°C to room temperature at a rate of 20°C per minute. The glass transition is also indicated by a stepwise increase in heat flow during heating from -80°C to 60°C. The glass transition temperature is defined as the temperature at which the heat flow is at the midpoint of the step change.

[0040] In a preferred embodiment, the (meth)acrylic polymer used in the present invention may be in the form of a (meth)acrylic polymer emulsion prepared by emulsion polymerization as is well known in the art. In practice, a reactive mixture including the monomer of the present invention, water, one or more emulsifiers, and one or more initiators is provided to a reaction vessel. The components of the reactive mixture may be combined in any manner. For example, two or more components of the reactive mixture, or portions thereof, may be mixed together before a mixture of those components, or portions thereof, is placed in the reaction vessel. For example, components, or portions thereof, that are not mixed together outside the reaction vessel may be added simultaneously or sequentially to the reaction vessel. The above methods of providing the components of the reactive mixture may be used in any combination. After the reactive mixture is in the reaction vessel, conditions are provided for the reactive mixture to undergo emulsion polymerization. For example, conditions necessary for the initiator to form one or more free radicals are provided. That is, depending on the initiator used, for example, the reaction mixture may be heated, a reducing agent may be added, the reaction mixture may be exposed to radiation, or a combination thereof. It is also contemplated that other conditions (e.g., emulsification of monomers, concentration of monomers, initiator concentration, etc.) that result in successful emulsion polymerization are also provided. In some embodiments, the conditions for the reactive mixture to undergo emulsion polymerization are established simultaneously with the introduction of the reactive mixture into the reaction vessel. For example, if the components of the reactive mixture are not added simultaneously, in some embodiments, the conditions for the reactive mixture to undergo emulsion polymerization may be established simultaneously with the introduction of the final component of the reactive mixture into the reaction vessel. In some embodiments, it is contemplated that after the conditions for the reactive mixture to undergo emulsion polymerization are established, additional monomer may be added, additional water may be added, additional emulsifier may be added, additional initiator may be added, or any mixture or combination thereof may be added.

[0041] In the present invention, commercially available (meth)acrylic polymers can also be used, examples of which include DE-B and DE-E polymer emulsions, which are commercially available from Wanhua Chemical Co., Ltd.

[0042] Particularly preferably, the (meth)acrylic polymer in the present invention is present in an amount of 40.0% to 70.0% by weight, preferably 45.0% to 70.0% by weight, based on the total weight of the aqueous polymer emulsion.

[0043] Corrosion Inhibitors According to the present invention, the aqueous polymer emulsion further comprises at least one corrosion inhibitor.Generally, when electrochemical corrosion occurs on metal surface, metal ions released from metal substrate surface cause emulsion destruction, resulting in deposition.Corrosion inhibitor is generally desired in the composition to suppress the release of metal ions and prevent emulsion destruction, so as to improve electrochemical deposition prevention performance.

[0044] In some embodiments, the corrosion inhibitors of the present invention are zinc-based corrosion inhibitors, phosphate-based corrosion inhibitors, carboxylate-based corrosion inhibitors, ion-exchanged silica-based corrosion inhibitors, and organic corrosion inhibitors. Such corrosion inhibitors may be used alone or in combination.

[0045] Examples of suitable corrosion inhibitors include, but are not limited to, sulfonates, phosphines, oxides and silicates; zinc oxide, zinc phosphate, zinc borate, zinc molybdate, barium metaborate, calcium borosilicate, barium sulfate, aluminum phosphate, magnesium oxide, strontium zinc phosphosilicate.

[0046] Examples of zinc-based corrosion inhibitors include, for example, VOK®-AP 179 available from VOK Corporation; HEUCOPHOS ZPA and ZAPP zinc aluminum phosphate, HEUCOPHOS ZAM and ZMP zinc molybdenum phosphate, HEUCOPHOS ZPO zinc orthophosphate, and the like, available from Heucotech Corporation. Examples of phosphate-based corrosion inhibitors include, for example, micronized HALOX SZP-39 1, HALOX 430 calcium phosphate, HALOX ZP zinc phosphate, HALOX SW-ill strontium phosphate silicate, HALOX 720 mixed metal phosphorus carbonate, and HALOX 700, 550 and 650 (proprietary organic corrosion inhibitors available from Halox Corporation, Hammond, Ind.). Examples of carboxylate-based corrosion inhibitors include, for example, ASCOTRAN® H14 and ASCOTRAN® NSC available from Ascotec Corporation. An example of an organic acid based corrosion inhibitor is KH 7026 available from HPM New Materials (Shanghai) Co., Ltd. Examples of ion-exchanged silica based corrosion inhibitors include Shieldex® CS313, Shieldex® 303 available from Grace, and NOVINOX XCA02 available from SNCZ. Other suitable corrosion inhibitors include HEUCOPHOS SAPP and SRPP strontium aluminum polyphosphate hydrate, HEUCOPHOS CAPP calcium aluminum polyphosphate available from Heucotech.

[0047] Particularly preferably, the corrosion inhibitor is present in the aqueous polymer emulsion in an amount of from 0.01% to 5.0% by weight, preferably from 0.03% to 3.5% by weight, based on the total weight of the aqueous polymer emulsion.

[0048] Chelating Agents According to the present invention, the aqueous polymer emulsion further comprises at least one chelating agent, which can capture metal ions on the substrate and prevent the polymer particles from agglomerating in the aqueous medium, thereby improving the resistance to electrochemical deposition of metals.

[0049] The ligands are typically organic compounds, also called chelators, chelating agents, or sequestering agents, and may be biodegradable in embodiments of the present invention.

[0050] Exemplary chelating agents that may be employed in the present invention are selected from ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid (DTPA), N-(hydroxyethyl)ethylenediaminetetraacetic acid (HEDTA), nitrilotriacetic acid (NTA), 2,3-dimercaptosuccinic acid (DMSA), citric acid, salicylic acid or its amino or sulfone derivatives, and combinations thereof. In addition to the acid form of the chelating agent, salts that may be employed include alkali metal salts such as sodium salt, disodium salt, tetrasodium salt, diammonium salt, tetraammonium salt, and other salts. Physical forms of the chelating agent include liquid, powder, and crystalline forms.

[0051] Commercially available DTPA, HEDTA and NTA chelating agents are available from Dow Chemical Company, Midland Mich and Shijiazhuang Jackchem Co.

[0052] Particularly preferably, the chelating agent is present in the aqueous polymer emulsion in an amount of 0.01 to 5.0% by weight, preferably 0.01 to 3.0% by weight, based on the total weight of the aqueous polymer emulsion.

[0053] water According to the present invention, water, preferably deionized water, is included in the polymer emulsion. Preferably, water is present in the polymer emulsion in an amount of 29.98% to 50.00% by weight, preferably 34.00% to 50.00% by weight, based on the total weight of the aqueous polymer emulsion.

[0054] Other additives Additives can be added to improve the stability of the emulsion and to meet various mechanical and rheological requirements, such as humectants, skin time extenders, adhesion promoters, thickeners, defoamers, pH adjusters and combinations thereof.

[0055] Non-limiting examples of humectants include betaine, glycerol, D-sorbitol, polyglycols, polyoxyethylene sorbitan, sodium lactate, and combinations thereof, commercially available from Sinopharm Group. When present, the preferred amount of humectant used in the present invention is 0.01-10.0%, preferably 0.1-3.0%, more preferably 0.2-0.6%, based on the total weight of the aqueous polymer emulsion.

[0056] Non-limiting examples of thickeners include hydroxypropyl methylcellulose thickeners. Preferably, these thickeners are hydroxymethylcellulose (HEA), hydroxyethylcellulose (CMC), BASF VISCALEX AT88, OMG Borch Gel ALA, Contex COAPUR TM The preferred amount of the thickener used in the present invention is 0.01-3.0%, preferably 0.1-1.0%, more preferably 0.2-0.5%, based on the total weight of the aqueous polymer emulsion.

[0057] Non-limiting examples of defoamers are oil-based defoamers, such as paraffin oil, mineral oil, silicone-based defoamers, or mixtures of polyether and mineral oil. Such defoamers are commercially available under the names DFC171 from Shanghai Champion Chemical, SN Defoamer 8370, 470, 485 from Sannopc, BYK-024 from BYK, Foamaster® MO 2134, Foamaster® MO 2150, Foamaster® NO 2335 and FoamStar® ST 2438 from BASF. When present, the preferred amount of defoamer of the present invention is 0.001-3.0%, preferably 0.01-1.0%, more preferably 0.1-0.3%, based on the total weight of the aqueous polymer emulsion.

[0058] To improve the flowability and prolong the skin time, anti-skinning agents such as polyhydroxy alcohols can be added. Preferred anti-skinning agents can be selected from maltitol, betaine, sodium lactate available from Sinopharm Group, and BYK-348 available from BYK Group. Preferably, the amount added is 0.1-1.5% based on the total weight of the aqueous emulsion to obtain good wetting behavior (and long skin time under vacuum).

[0059] To improve the adhesion between inorganic materials such as plastics and organic polymers, adhesion promoters, such as polyfunctional organosilanes and isocyanate crosslinkers, can be added. Preferably, the adhesion promoter contains at least one silane group, which can effectively improve the cohesive strength of the emulsion. Preferred examples are Dynasylan® GLYEO and Dynasylan® HYDROSIL 2926 from Evonik, WM44-L70G from Asahi Kasei, and TCI-E0327 from TCI Group. When present, the amount ranges from 0.1 to 1.5%, based on the total weight of the aqueous emulsion.

[0060] A pH adjuster, such as acetic acid, may be added to neutralize the alkaline chelating agents of the compositions of the present invention.

[0061] Water-based polymer emulsion Preferably, the aqueous polymer emulsion has a solids content of 50% by weight or more, preferably 60% by weight or more. For commercial applications, a solids content that can withstand pneumatic and hydraulic pressures is desired. Here, the solid content concentration is determined by drying 1 gram of the emulsion in a general oven at 130° C. for 30 minutes, weighing it with a precision weighing machine, and calculating the solid content concentration as a percentage.

[0062] Preferably, the aqueous polymer emulsion of the present invention exhibits a viscosity of 200-2000 cPs at 25° C., preferably 500-1000 cPs at 25° C., preferably 500-800 cPs at 25° C., as measured on a Brookfield DV2t LV-02 with spindle 62 at 20 rpm.

[0063] In a preferred embodiment, the aqueous polymer emulsion comprises, based on the total weight of the aqueous polymer emulsion: (a) 40.0% to 70.0% by weight, preferably 45.0% to 70% by weight, of at least one (meth)acrylic polymer prepared by at least two monomers comprising at least one alkyl (meth)acrylate and at least one unsaturated carboxylic acid, (b) 0.01% to 5.0% by weight, preferably 0.03% to 3.5% by weight, of at least one corrosion inhibitor; (c) 0.01% to 5.0% by weight, preferably 0.01% to 3.0% by weight, of at least one chelating agent, and (d) 29.98% by weight to 50.0% by weight, preferably 34.0% by weight to 50.0% by weight, of water; wherein said at least one unsaturated carboxylic acid is present in an amount less than 3.5 weight percent, based on the total weight of monomers.

[0064] The object of the present invention is to make available an aqueous polymer emulsion, obtained in a simple, industrially suitable and reproducible manner, which can be used as a vacuum impregnation composition and which exhibits satisfactory resistance to electrochemical deposition properties and good pore-sealing properties for cast metals or parts co-molded by two different metallic materials.

[0065] solidified product In another aspect of the present invention, there is provided a solidified product of the aqueous polymer emulsion according to the present invention.

[0066] In a further aspect of the present invention, there is provided a part comprising a solidified product according to the present invention.

[0067] In an additional embodiment of the invention, there is provided an electronic device comprising a component according to the invention. Exemplary electronic devices include computers and computing equipment such as printers, faxes, scanners, keyboards, consumer electronics, medical sensors, automotive sensors, and the like, and personal electronic devices such as telephones, mobile phones, calculators, remote controls, cameras, CD players, DVD players, cassette tape recorders, laptops, tablet computers, and the like.

[0068] In this specification, "solidification" means that the solids contained in the emulsion penetrate into the pores of the component having voids during the drying process after the impregnation step to become a sealant. This conversion is expressed as the "solidification process" in the present invention, but it can be a purely physical conversion or a chemical reaction after crosslinking, if hydrazide and acetoacetate groups are present. Typically, the impregnated parts are heated in the range of about 40°C to about 80°C during the solidification process, although temperatures outside this range can also be used if appropriate.

[0069] How to seal voids (pores) In an additional embodiment of the present invention, there is provided a method for sealing voids in a component, comprising: a) vacuum impregnating the component with an aqueous polymer emulsion according to the present invention; and b) solidifying the aqueous polymer emulsion at a temperature in the range of 40-80° C. for at least 30 minutes, followed by drying at room temperature for at least 1 day.

[0070] Basically, the aqueous polymer emulsion of the present invention penetrates and fills the voids of porous materials, cast metals, or parts that are co-molded with at least two different metals in particular. Using a vacuum process, air is removed from the voids of the part to be impregnated and replaced with the agent in the emulsion. The impregnated part is then washed and the aqueous polymer emulsion is allowed to solidify.

[0071] Specifically, in a vacuum impregnation process, there is usually an impregnation chamber in which the parts to be impregnated are placed. The penetration of the aqueous emulsion of the present invention into the voids of the parts may be assisted by optionally pressurizing the impregnation chamber with compressed air. A typical process using the aqueous emulsion of the present invention involves the impregnation of porous parts contained in a basket that is introduced into the impregnation chamber. This is the common method if the parts are reasonably small. For larger parts, the same are typically mounted or suspended on a hoist or carrier. In a wet vacuum impregnation process, a basket of porous parts is immersed in a vacuum tank filled with the aqueous emulsion of the present invention. A short vacuum cycle, for example 10-12 minutes, removes the air from the pores of the parts. The chamber is then returned to normal pressure and the emulsion penetrates into the evacuated voids.

[0072] The wet vacuum impregnation process works similarly, but the impregnation chamber is pressurized at the end of the vacuum cycle to further force the impregnation composition into the small void passages. In the dry vacuum impregnation method, a basket of porous parts is placed directly into the dry vacuum chamber. Air is evacuated from the voids of the part for a selected time, e.g., 10 minutes. A transfer valve is then opened and the aqueous emulsion of the present invention enters the vacuum chamber from a storage reservoir. The chamber is automatically pressurized, forcing the aqueous emulsion of the present invention into the part. After impregnation, the basket is suspended in free fall while the emulsion is returned to the reservoir to remove excess surface emulsion. Of the aforementioned methods, the wet vacuum impregnation technique is generally more widely adopted than the dry vacuum impregnation process, but either process is suitable for use in the present invention.

[0073] After the first impregnation step, the impregnated parts are optionally transferred to an agitated water-rinsing zone to remove any remaining emulsion trapped in the grooves or threaded holes of the impregnated parts. Agitation in the water-rinsing zone can be affected by mechanical means to effect movement of baskets or suspended parts in such zones and / or circulation of water therein. Water, surfactants, alkaline aqueous solutions and very small amounts of alcohols can be used for rinsing. For small porous parts housed in baskets, it is often desirable to operate the water-rinsing zone in a "tumbling basket" mode to enhance the cleaning effect. The impregnated parts may then be transferred to a solidification zone at temperatures between 40°C and 80°C for at least 30 minutes. To warm and solidify the impregnated parts, a self-crosslinking reaction may take place. In impregnation systems using room temperature, after the impregnation step, the parts can be transferred to an oven for drying and allowed to cool at room temperature overnight. In use, the impregnation composition may be employed in an impregnation chamber of conventional typical construction, where a "wet" or "dry" vacuum is imposed on the porous component to be impregnated, and the evacuated porous component is contacted with the impregnation composition at higher, e.g. ambient, pressure, thereby allowing the impregnation composition to pass into the voids of the porous component, resulting in impregnation thereof.

[0074] In yet another aspect of the present invention there is provided the use of the aqueous polymer emulsion according to the present invention in gap sealing.

[0075] The aqueous emulsion of the present invention used as an impregnation composition is characterized by satisfactory resistance to electrochemical deposition properties and good pore sealing performance for cast metals or parts co-molded by two different metal materials. Moreover, the preparation of the emulsion of the present invention, the technique of vacuum impregnation with it, and the subsequent processing are both easy for commercial use. EXAMPLES

[0076] Working Example The following examples are intended to help those skilled in the art to better understand and practice the present invention. The scope of the present invention is not limited by the examples, but is defined by the appended claims. All parts and percentages are by weight unless otherwise specified.

[0077] material DE-B is an aqueous emulsion of (meth)acrylic polymer prepared with monomers including alkyl (meth)acrylate and 2.8 wt. % (meth)acrylic acid based on the total weight of monomers, having a polymer content of 55-65% based on the total weight of the aqueous emulsion, and is available from Wanhua Chemical Co.

[0078] DE-E is an aqueous emulsion of (meth)acrylic polymer prepared by monomers consisting of alkyl (meth)acrylate, hydroxyalkyl (meth)acrylate and 0.5 wt. % (meth)acrylic acid based on the total weight of monomers, having a polymer content of 55-65% based on the total weight of the aqueous emulsion, and is available from Wanhua Chemical Co.

[0079] DE-H is an aqueous emulsion of (meth)acrylic polymer prepared with monomers including alkyl (meth)acrylate and 3.5 wt. % (meth)acrylic acid based on the total weight of monomers, having a polymer content of 55-65% based on the total weight of the aqueous emulsion, and is available from Wanhua Chemical Co.

[0080] DFC171 is a defoamer available from Shanghai Champion Chemical Company.

[0081] SN Defoamer 8370 is a mixture of mineral oil, polyether, silica and water defoamer available from Sannopco.

[0082] ASCOTRAN TM H14 is a carboxylate-based corrosion inhibitor that prevents flammable rust and is available from Ascotec.

[0083] VOK TM -AP 179 is a zinc-based corrosion inhibitor available from VOK.

[0084] DTPA is diethylenetriaminepentaacetic acid, pentasodium salt, available from SHIJIAZHUANG JACKCHEM COMPANY.

[0085] Betaine is available from the Sinopharm Group.

[0086] Rheobyk-HV 80 is a VOC-free associative thickener available from the BYK Group.

[0087] Acetic acid is available from the Sinopharm Group.

[0088] Test Method: Electrostatic deposition performance Two laminates each of stainless steel SUS304 and aluminum Al6061 were prepared, each 2 mm thick, 25.4 mm long, and 76.2 mm wide. The two laminates were pressed to form so-called "bistratal metal" test specimens. The test specimens were placed in the emulsion of the example described in the present invention for 30 minutes. The test specimens were then removed and subjected to the following cleaning schedule:

[0089] Step 1: The test specimen was immersed in a tank containing 1-2 wt% of the cleaning agent at room temperature for 1-3 minutes, during which air was introduced into the tank; Step 2: Step 1 was repeated twice, removed from the test specimen and placed in the fresh tank in the same arrangement as in step 1; Step 3: The test specimen was removed and placed in a tank containing 1-2 wt% cleaning agent at 45°C for 2-4 minutes, during which air was introduced through the tank and the test specimen was vibrated at high frequency. Step 4: The specimens were removed from the tank in step 3 and placed in a tank containing deionized water at 40°C for 1 to 3 minutes.

[0090] After cleaning, the test pieces were dried at 60°C for 30 min or at room temperature for 6 to 12 h, and the appearance was observed by counting the number of electrolytic deposition spots (galvanic deposition spots).

[0091] The electrochemical vapor deposition resistance performance of each example of the present invention was evaluated according to the following scale:

[0092] TIFF2025517562000001.tif36159

[0093] Level A was considered favorable, and level B was considered acceptable.

[0094] Leak proof performance: The leak-proofing performance of the composition of the present invention was evaluated based on two test pieces made of anodized aluminum and stainless steel SUS304 sheet, respectively. Both of these two types of parts had fine pores. The vacuum impregnation was carried out using the emulsion of the embodiment described in the present invention. Specifically, the test pieces were placed in a vacuum impregnation tank. The vacuum stage was kept for a few minutes, after which the vacuum was released to allow the emulsion to be impregnated into the fine pores of the parts. During the impregnation stage, 5 bar of compressed air was introduced through the tank cover to pressurize the vacuum impregnation tank. After the impregnation stage, the vacuum impregnation tank was opened, the test pieces were removed, and the following cleaning schedule was carried out:

[0095] Step 1: The test specimen was immersed in a tank containing 1-2 wt% of the cleaning agent at room temperature for 1-3 minutes, during which air was introduced into the tank; Step 2: Step 1 was repeated twice, removed from the test specimen and placed in the fresh tank in the same arrangement as in step 1; Step 3: During the process, the test specimens were removed and placed in a tank containing 1-2 wt% of the cleaning agent at 45°C for 2-4 minutes; and Step 4: The specimens were removed from the tank and placed in a tank containing deionized water at 40°C for 1 to 3 minutes.

[0096] After washing, the samples were dried at 60°C for 30 minutes or at room temperature for 6 to 12 hours, and then their appearance was observed.

[0097] Five samples were tested for each example using two test pieces. The air leakage rate for each was recorded, if any, and the average air leakage rate was calculated by arithmetic averaging and the air leakage characteristics were rated on the following scale:

[0098] TIFF2025517562000002.tif41145

[0099] A level was considered favorable and A or B levels were considered acceptable.

[0100] Examples 1 to 6 (Ex.1 to Ex.6) and Comparative Examples 1 to 3 (CE.1 to CE.3) Emulsions were prepared by the following method using the components in the amounts (parts by weight) shown in Table 1, and the properties were tested by the methods described above. The evaluation results are shown in Table 1.

[0101] In general, the preparation of the aqueous emulsion is not particularly limited as long as the components described herein are homogeneously mixed, but a preferred preparation method comprises the following steps: (1) preparing an aqueous emulsion of the (meth)acrylic polymer of the present invention; (2) optionally adding an antifoaming agent to the emulsion obtained in (1); (3) optionally adding and mixing chelating agents, corrosion inhibitors, and other additives (such as moisturizers, skin time extenders, adhesion promoters, etc.); and (4) adding a thickening agent to the emulsion obtained in step (3) and mixing until uniform;

[0102] Table 1 TIFF2025517562000003.tif96170 TIFF2025517562000004.tif57168

[0103] As can be seen from Table 1, the emulsions of the examples of the present invention exhibited satisfactory electrolytic deposition prevention performance and good pore-blocking performance for metals, as compared with the comparative examples.

[0104] While certain preferred embodiments have been described, many modifications and variations are possible in light of the above teachings, and it is to be understood that the invention may be practiced otherwise than as specifically described without departing from the scope of the appended claims.

Claims

1. An aqueous polymer emulsion comprising: (a) at least one (meth)acrylic polymer prepared from at least two monomers comprising at least one alkyl (meth)acrylate and at least one unsaturated carboxylic acid; (b) at least one corrosion inhibitor; and (c) at least one chelating agent; wherein the at least one unsaturated carboxylic acid is present in an amount of less than 3.5% by weight, based on the total weight of the monomers.

2. The aqueous polymer emulsion according to claim 1, wherein the at least one unsaturated carboxylic acid is selected from acrylic acid, methacrylic acid, crotonic acid, itaconic acid, cinnamic acid, linolenic acid, oleic acid, and combinations thereof, preferably acrylic acid and / or methacrylic acid.

3. The aqueous polymer emulsion according to claim 1, wherein the at least one unsaturated carboxylic acid is present in an amount of 3% by weight or less, preferably 0.01% to 3% by weight, more preferably 0.5% to 2.8% by weight, based on the total weight of the monomers.

4. The at least one alkyl (meth)acrylate is selected from methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, s-butyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, heptadecyl (meth)acrylate, octadecyl (meth)acrylate, nonadecyl (meth)acrylate, eicosyl (meth)acrylate, and combinations thereof, preferably selected from methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, s-butyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, and combinations thereof, the aqueous polymer emulsion according to claim 1.

5. The at least two monomers further comprise at least one other monomer, preferably, the at least one other monomer is selected from (meth)acrylates having at least one hydroxyl group, acrylonitrile, acrylamide, (meth)acrylamide, N-substituted (meth)acrylamide, hydroxyacrylamide, diacetoneacrylamide, vinyl esters, vinyl ethers, styrene, alkyl- or halo-styrene, N-vinylpyrrolidone, vinyl chloride, vinylidene chloride, diacrylate monomers, silicon monomers, phosphoric acid / polyphosphoric acid monomers, and combinations thereof, preferably, the at least one other monomer is a (meth)acrylate having at least one hydroxyl group, the aqueous polymer emulsion according to claim 1.

6. The (meth)acrylate having at least one hydroxyl group is selected from 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 1,4-cyclohexanedimethanol mono(meth)acrylate, glycerol mono(meth)acrylate, polyethylene glycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, lactone-modified (meth)acrylate containing a terminal hydroxyl group, and combinations thereof, preferably, selected from 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and combinations thereof, the aqueous polymer emulsion according to claim 5.

7. The at least one (meth)acrylic polymer has a number average molecular weight of 20,000 to 2,000,000 g / mol, preferably 50,000 to 1,000,000 g / mol, more preferably 100,000 to 500,000 g / mol as measured by gel permeation chromatography (GPC), the aqueous polymer emulsion according to claim 1.

8. The at least one corrosion inhibitor is selected from a zinc-based corrosion inhibitor, a phosphate-based corrosion inhibitor, a carboxylate-based corrosion inhibitor, an ion-exchanged silica-based corrosion inhibitor, an organic corrosion inhibitor, and combinations thereof, and the aqueous polymer emulsion according to claim 1.

9. The at least one chelating agent is selected from ethylene diamine tetraacetic acid (EDTA), diethylene triamine pentaacetic acid (DTPA), N-(hydroxyethyl) ethylene diamine tetraacetic acid (HEDTA), nitrilotriacetic acid (NTA), 2,3-dimercaptosuccinic acid (DMSA), citric acid, salicylic acid or an amino derivative or sulfone derivative thereof, an alkali metal salt selected from a sodium salt, a disodium salt, a tetrasodium salt, a diammonium salt, a tetraammonium salt, and combinations thereof, and the aqueous polymer emulsion according to claim 1.

10. The aqueous polymer emulsion further comprises at least one additive selected from a humectant, a thickener, an antifoaming agent, a skin time extender, an adhesion promoter, a pH adjuster, and combinations thereof, and the aqueous polymer emulsion according to claim 1.

11. The aqueous polymer emulsion has a solid content of 50% by weight or more, preferably 60% by weight or more, and the aqueous polymer emulsion according to claim 1.

12. A solidified product of the aqueous polymer emulsion according to any one of claims 1 to 11.

13. A component comprising the solidified product according to claim 12.

14. a) Vacuum impregnating a component with the aqueous polymer emulsion according to any one of claims 1 to 11, b) solidifying the aqueous polymer emulsion at a temperature in the range of 40 to 80 °C for at least 30 minutes, and then drying at room temperature for at least 1 day, and a method for sealing voids in a component.

15. Use of the aqueous polymer emulsion according to any one of claims 1 to 11 in void sealing.