Aqueous polymer dispersion and use thereof

Abstract

The present invention provides an aqueous polymer dispersion comprising at least one polymer having a carboxyl group and, where appropriate, additional functional groups selected from the following: hydroxyl, isocyanate, fluorine, phosphate, acetylhydrazine, acetylacetyl groups and combinations thereof, wherein the polymer has a glass transition temperature greater than -40°C and less than 35°C, and the aqueous polymer dispersion has a solids content greater than 50% by weight.

Description

[Technical Field]

[0001] This invention relates to aqueous polymer dispersions, and more particularly to aqueous polymer dispersions used as impregnation compositions for vacuum impregnation and their applications. [Previous Technology]

[0002] Numerous small holes are typically present in metal castings (such as cast aluminum and cast iron) and electronic components co-molded from metal and plastic. These small holes can cause leakage problems, which pose a significant obstacle to commercial applications, especially when such porous components are used in fluid power systems and other liquid handling applications.

[0003] One method to solve this problem is to disperse the sealant onto the holes of the component using a dispersion machine. This point-to-point dispersion method has many disadvantages: it can alter the size of the component, affect its appearance, and the resulting sealant, being on the outer surface of the component, is susceptible to failure due to impact. After failure, the sealant needs to be redispersed, which is expensive and time-consuming.

[0004] Vacuum impregnation (VI) technology is an effective method for sealing porous components without altering their size or functional characteristics. Vacuum impregnation technology uses a vacuum pressure process to penetrate an impregnating agent into the pores of metal components or assemblies co-molded from metal and plastic. Upon completion of the vacuum impregnation process, the component is transferred to the next process, namely a cleaning process, a drying process, or a curing process. In this process, the impregnating agent forms a sealant to fill the pores, achieving sealing and preventing leakage, and withstanding high pressure, thereby solving the leakage problem of the component.

[0005] In this technology, there are three main types of impregnation compositions used as vacuum impregnation sealants: inorganic sodium silicate sealants, unsaturated polyesters, and functional polyacrylate resins. Sodium silicate sealants were the earliest type used in the industry, but due to their high viscosity and poor wettability, resulting in unsatisfactory porosity, they are no longer used. Due to the high viscosity of unsaturated polyesters used as impregnation compositions, they usually must be used with diluents. However, most diluents exhibit toxicity and high volatile organic compound (VOC) release. Therefore, for environmental protection reasons, unsaturated polyesters have been gradually replaced by functional polyacrylate resins as impregnation compositions. Polyacrylate resins mainly contain functional acrylate monomers. Emulsifiers, chelating agents, and additives (such as fluorescent agents) are typically added for vacuum impregnation.

[0006] In the previously developed impregnation compositions for sealing porous components, there exists a composition disclosed in the patents identified and discussed below.

[0007] U.S. Patent No. 3,672,942 discloses an impregnation composition comprising a free radical polymerizable acrylate monomer and a free radical polymerization initiator (e.g., hydroperoxide).

[0008] U.S. Patent No. 3,969,552 describes an impregnation composition comprising a curable acrylic resin and a peroxide initiator. The washing solution is an aqueous solution of a surfactant of a specified formulation. The patent further discloses that the aqueous surfactant solution may contain an accelerator to achieve polymerization of an anaerobic sealant in the surface area of ​​the washed and impregnated part.

[0009] U.S. Patent No. Re. 32,240 describes a self-emulsifying anaerobic composition comprising an anaerobic-curing monomer (e.g., acrylate), a peroxide initiator (e.g., hydroperoxide or perester), an anionic or nonionic surfactant (which dissolves in the composition and self-emulsifies when mixed with water), and, where appropriate, an accelerator for anaerobic polymerization.

[0010] U.S. Patent No. 4,632,945 discloses an impregnation composition comprising (meth)acrylate monomers, hydroperoxide or perester initiators, accelerators having -SO2NCO- functionality, and transition metal co-accelerators comprising a copper ion source and an iron salt or ferrocene compound.

[0011] U.S. Patent No. 5,656,710 provides a reactive, i.e., low-viscosity, vulcanizable sealant composition that is temperature and chemical resistant and will not interfere with the electrical properties of the impregnated electronic components. This vulcanizable silicone is selected from the group consisting of: (i) a thermocurable polysiloxane composition, which is the product of the reaction of a first silicone-containing material having at least two SiH functionalities and a molecular weight of less than 2000 with a second silicone-containing material having at least two olefinic unsaturated functionalities and a molecular weight of less than 2000 in the presence of a platinum catalyst; and (ii) a room-temperature vulcanizable polysiloxane composition, which is the product of the reaction of a polysiloxane fluid having at least two SiOH functionalities and a molecular weight of less than 2000 with a silane crosslinking agent of a specific formula.

[0012] CN 1356365 A provides an impregnation composition having low viscosity and high thermal properties, which is prepared from methacrylate monomers, accelerators, polymerization inhibitors and crosslinking agents composed of dienyl compounds having a single benzene ring and methacrylates having three or four functional groups.

[0013] CN 104357010 A provides an impregnation composition based on polyacrylate, which improves the volume shrinkage problem by introducing inorganic reinforcing particles. However, impregnation compositions based on curable acrylic resins have inherent drawbacks, such as the difficulty in removing impregnation composition residues adhering to the surface of the part after the impregnation process. This affects the adhesion and appearance of the part, thus requiring a large amount of solvent or cleaning agent for repeated washing, resulting in contamination. However, even so, the residues cannot be completely removed. Additional drawbacks include shrinkage problems before and after curing, which leads to poor sealing performance. Although it is disclosed that this can be improved by introducing inorganic reinforcing particles into the impregnation composition, this reduces the solids content of the curing agent, achieving limited sealing properties.

[0014] Therefore, there is a need in the industry to improve the pore-sealing properties of existing impregnation compositions used in vacuum impregnation processes. [Summary of the Invention]

[0015] After in-depth research, the inventors were surprised to find that aqueous dispersions can be used as a new type of impregnation composition in vacuum impregnation processes.

[0016] In one embodiment of the present invention, an aqueous dispersion that can be used as an impregnating agent is provided, comprising: at least one polymer having a carboxyl group and, where appropriate, additional functional groups selected from the following: hydroxyl, isocyanate, fluorine, phosphate, acetylhydrazine, acetylacetyl groups and combinations thereof, wherein the polymer has a glass transition temperature greater than -40°C and less than 35°C, and the aqueous polymer dispersion has a solids content greater than 50% by weight.

[0017] In an additional embodiment of the present invention, a cured product of the aqueous dispersion according to the present invention is provided.

[0018] In an additional embodiment of the present invention, a component comprising a cured product according to the present invention is provided.

[0019] In an additional embodiment of the present invention, an electronic device comprising components according to the present invention is provided.

[0020] In an additional embodiment of the present invention, a method for sealing pores in a component is provided.

[0021] The aqueous dispersion of the present invention penetrates and fills the voids in porous materials, cast metals, or parts specifically molded from metal and plastic. By using a vacuum process, air is removed from the pores of the part to be impregnated and replaced by components in the dispersion. The impregnated part can then be washed and the aqueous dispersion cured.

[0022] In another embodiment of the present invention, the use of the aqueous polymer dispersion of the present invention in pore sealing is provided.

[0023] The aqueous dispersion of the present invention, used as an impregnation composition, is characterized by excellent pore-sealing performance and good bonding strength for cast metal or parts co-molded from metal and plastic. Furthermore, compared to acrylic resin-based impregnation compositions, by using the aqueous dispersion of the present invention as an impregnation composition, the impregnated parts only require simple washing with a cleaning agent selected from water, surfactants, alkaline solutions, or alcohols and combinations thereof, which is an environmentally friendly technology. In addition, the preparation of the dispersion of the present invention, the vacuum impregnation technique using it, and its post-treatment are extremely simple for commercial applications (e.g., waterproof electronic devices).

Implementation Method

[0024] Those skilled in the art should understand that the present invention is merely an illustration of exemplary embodiments and is not intended to limit the scope of the invention. Unless explicitly indicated to the contrary, each of the embodiments described may be combined with any other one or more embodiments. In particular, any feature indicated as preferred or advantageous may be combined with any other one or more features indicated as preferred or advantageous.

[0025] Unless otherwise stated, the terms used in the context of this invention shall be interpreted in accordance with the following definitions.

[0026] Unless otherwise stated, as used herein, the terms "a" and "the" include both the singular and plural indicators.

[0027] As used herein, the terms “comprising, comprises” and “including, includes” or “containing, contains” are synonymous and are inclusive or open-ended, and do not exclude additional, undescribed members, elements or processing steps.

[0028] Unless otherwise stated, the description of numerical endpoints includes all numbers and fractions belonging to the respective ranges, as well as the described endpoints.

[0029] Unless otherwise agreed, molecular weight refers to the nominal average molecular weight (Mn). Unless otherwise agreed, all molecular weight data refer to values ​​obtained by gel permeation chromatography (GPC), for example according to DIN 55672.

[0030] All references cited in this specification are incorporated herein by reference in their entirety.

[0031] Unless otherwise defined, all terms used in this invention (including technical and scientific terms) shall have the meanings commonly understood by one of ordinary skill in the art described herein.

[0032] The present invention relates to an aqueous polymer dispersion comprising: at least one polymer having a carboxyl group and, where appropriate, additional functional groups selected from the following: hydroxyl, isocyanate, fluorine, phosphate, acetylhydrazine, acetylacetyl groups and combinations thereof, wherein the polymer has a glass transition temperature greater than -40°C and less than 35°C, and the aqueous polymer dispersion has a solids content greater than 50% by weight.

[0033] There are no restrictions on the polymers used in the aqueous polymer dispersion, as long as other properties of the polymer meet the requirements. Generally, the polymer can be selected from poly(meth)acrylic acid (PA), polyurethane (PUD), vinyl acetate / ethylene copolymer (VAE), acrylic acid-modified VAE, polyvinyl acetate (PVAc), or acrylic acid-modified PVAc and combinations thereof.

[0034] Glass Transition Temperature (Tg) According to the present invention, the aqueous polymer dispersion contains at least one polymer having a glass transition temperature greater than -40°C and less than 35°C. If the Tg is too low, the cohesiveness of the polymer decreases, and therefore the sealant is prone to deformation and surface shrinkage, as well as adhesion failure, which leads to poor pore sealing.

[0035] In this paper, the glass transition temperature was determined using differential scanning calorimetry (TA DSC Q2000) according to the following procedure: The sample was equilibrated to 40°C, cooled to -50°C for 2 minutes, then heated from -50°C to 120°C at a rate of 10°C / min, and cooled from 120°C to room temperature at a rate of 20°C / min. During the heating from -50°C to 120°C, a step-like increase in heat flux was observed, indicating that a glass transition had occurred. The glass transition temperature was defined as the temperature at which the heat flux reached the midpoint of the step change.

[0036] In a preferred embodiment, the aqueous polymer dispersion comprises at least one polymer having a glass transition temperature of -30°C to 20°C, more preferably -30°C to 0°C and even more preferably -20°C to -5°C.

[0037] In a preferred embodiment, the D50 particle size of the polymer is 0.2 to 8.0 μm, more preferably 0.2 to 3.0 μm, more preferably 0.2 to 1.5 μm, and even more preferably 0.3 to 1.2 μm. In this document, the "D50 particle size" of the dispersion represents the median diameter of the volume-based particle size distribution curve obtained by means of a laser diffraction particle size analyzer.

[0038] In a preferred embodiment, the number average molecular weight of the polymer is 8,000 to 300,000 g / mol, more preferably 50,000 to 300,000 g / mol and even more preferably 100,000 to 300,000 g / mol.

[0039] The inventors of the functional group were surprised to find that polymers containing carboxyl groups and additional functional groups selected from hydroxyl, isocyanate, fluorine, phosphate, acetylhydrazine, and acetyl acetate groups, as appropriate, produce a combination of excellent pore sealing and good bonding strength due to various mechanisms. Specifically, (i) the carboxyl groups help to slightly corrode the surface of the metal to create micropores that can accommodate the particles of the dispersion, thus the sealant exhibits good bonding strength after curing; (ii) the phosphate groups increase the bonding to the metal surface due to the chelating effect; (iii) the hydroxyl groups generate van der Waals force with the free hydrogen on the metal surface; (iv) normally, polymers exhibit poor wetting properties on metal surfaces due to their large molecular weight, however, acetylglucosamine and acetylacetyl groups can exist stably in aqueous dispersions and undergo ketone-acetylglucosamine crosslinking when the dispersion cures, thus the subsequent crosslinking of acetylglucosamine and acetylacetyl groups greatly contributes to the sealing of pores in the component; (v) the isocyanate groups effectively improve the cohesiveness of the dispersion; and (vi) the fluorine groups exhibit excellent waterproof and rust-proof properties.

[0040] In some embodiments, the aqueous polymer dispersion comprises at least one polymer having a carboxyl group, wherein the at least one polymer has a glass transition temperature greater than -40°C and less than 35°C. Suitable examples of such polymers include Basf 7104 from BASF and BLJ-4122 from Shanghai Baolijia Chemical Co., Ltd.

[0041] In a preferred embodiment, the aqueous polymer dispersion comprises at least one polymer having a carboxyl group and additional functional groups selected from hydroxyl, isocyanate, fluorine, phosphate, acetylhydrazine, acetylacetonate, and combinations thereof, wherein at least one polymer has a glass transition temperature greater than -40°C and less than 35°C. Suitable examples of such polymers include the DE series products from Wanhua Chemical Co., Ltd.

[0042] In a preferred embodiment, the aqueous polymer dispersion comprises a first polymer having a carboxyl group and a second polymer having a carboxyl group and additional functional groups selected from hydroxyl, isocyanate, fluorine, phosphate, acetylhydrazine, acetylacetonate, and combinations thereof, wherein at least one polymer has a glass transition temperature greater than -40°C and less than 35°C. Suitable examples of the first polymer include Acronal® V 215 from BASF and BLJ-4122 from Shanghai Baolijia Chemical Co., Ltd. Suitable examples of the second polymer are LUMIFLON® FE-4300 from AGC Chemicals and the DE series from Wanhua Chemical Co., Ltd.

[0043] In a preferred embodiment, the aqueous polymer dispersion comprises a mixture of at least two different polymers having a carboxyl group and additional functional groups selected from hydroxyl, isocyanate, fluorine, phosphate, acetylhydrazine, acetylacetonate, and combinations thereof, wherein at least one polymer has a glass transition temperature greater than -40°C and less than 35°C. Suitable examples of such polymers include DE-G from Wanhua Chemical Co., Ltd., EM-123 from Guangzhou Lushan New Materials Co., Ltd., VINNAPAS®EAF 68 from Wacker, and Tekspro-7610 from Wanhua Chemical Co., Ltd.

[0044] The aqueous polymer dispersion according to the present invention has a solids content of more than 50% by weight. If the solids content is too low, the thickness of the resulting sealant will be insufficient to withstand the air or hydraulic pressure in commercial applications.

[0045] In this document, the solid content is determined by drying 1 gram of dispersion in a common furnace at 80°C for 30 minutes and then weighing it by a precision balance to calculate the solid content as a percentage.

[0046] Preferably, the solid content of the aqueous polymer dispersion is not less than 55% by weight and more preferably not less than 60% by weight.

[0047] Additives are preferably added to improve the stability of the dispersion and meet different mechanical and rheological requirements.

[0048] For example, neutralizing agents such as ammonia and ethanolamine may be added. These neutralizing agents are available from the Sinopharm Group. If present, the preferred amount is 0.1 to 1.5% wt, based on the total weight of the aqueous dispersion.

[0049] Another additive is a cellulose thickener and a polyacrylate thickener. Preferably, such thickeners are selected from hydroxymethyl cellulose (HEA), hydroxyethyl cellulose (CMC), BASF VISCALEX AT88, OMG Borch Gel ALA, Contex COAPUR™ 2025, etc. If present, the preferred amount is 0.1 to 1.5% wt based on the total weight of the aqueous dispersion.

[0050] An anti-skinning agent (e.g., a polyhydroxy alcohol) may be added to improve flowability and maintain a long skinning time. Preferred anti-skinning agents include maltitol, betaine, sodium lactate (available from the Sinopharm Group), and BYK-348 (available from the BYK Group). Based on the total weight of the aqueous dispersion, the preferred addition amount is 0.1 to 1.5% by weight to obtain good wetting behavior (and a long skinning time under vacuum).

[0051] Adhesion promoters (e.g., polyfunctional organosilanes) or isocyanate crosslinking agents may be added to improve the adhesion between inorganic materials (e.g., plastics) and organic polymers. Preferably, the adhesion promoter contains at least one silyl group, which can effectively improve the cohesiveness of the dispersion. Preferred examples are Dynasylan® GLYEO and Dynasylan® HYDROSIL 2926 from Evonik, WM44-L70G from Asahi Kasei, and TCI-E0327 from the TCI Group. If present, the preferred amount is 0.1 to 1.5% wt based on the total weight of the aqueous dispersion.

[0052] Other examples of additives are defoamers. Oil-based defoamers (e.g., paraffin oil, mineral oil), polysiloxane-based defoamers, or mixtures of polyether and mineral oil may be added. The defoamer may be selected from BYK-024 from BYK, Foamaster® MO 2134, Foamaster® MO 2150, Foamaster® NO 2335 and FoamStar® ST 2438 from BASF, and SN-DEFOAMER 470 and SN-DEFOAMER 485 from SAN NOPCO. If present, the preferred amount is 0.1 to 1.5% wt, based on the total weight of the aqueous dispersion.

[0053] The objective of this invention is to manufacture a usable aqueous polymer dispersion that can be obtained in a simple, industrially suitable and reproducible manner, without being limited to a specific polymer type or monomer, and has the Tg range and solids content range described herein, exhibiting excellent pore-sealing properties and good bonding strength.

[0054] In another embodiment of the present invention, a cured product of the aqueous polymer dispersion according to the present invention is provided.

[0055] In a preferred embodiment, using the ATSM D1002 test method, the cured product of the aqueous polymer dispersion has a bonding strength greater than 0.3 MPa, preferably greater than 0.35 MPa, wherein the test material is on anodized aluminum (AnAl) and polybutylene terephthalate (PBT) or glass fiber reinforced PBT.

[0056] In a preferred embodiment, the cured product of the aqueous polymer dispersion has an average air leakage of less than 0.1 mL / min on stainless steel.

[0057] In a preferred embodiment, the cured product of the aqueous polymer dispersion has an average air leakage of less than 0.1 mL / min on aluminum.

[0058] In an additional embodiment of the present invention, a component comprising the cured product of the present invention is provided.

[0059] In an additional embodiment of the invention, an electronic device is provided that includes components of the invention.

[0060] For the purposes of this invention, "curing" as used herein is intended to refer to the process during drying following the impregnation process, in which the solid contents contained in the dispersion enter the pores of a porous component and become a sealant. This transformation is described herein as a "curing process," which can be a purely physical transformation or, if acetylacetonate and acetyl acetate groups are present, a post-crosslinking chemical reaction. Typically, during the curing process, the impregnated component is heated to approximately 50°C to approximately 100°C, but temperatures exceeding this range may be used where appropriate.

[0061] In an additional embodiment of the invention, a method for sealing pores in a component is provided. Essentially, the aqueous dispersion of the invention penetrates and fills pores in porous materials, cast metals, or components particularly molded from a combination of metal and plastic. Air is removed from the pores of the component to be impregnated using a vacuum process and replaced with a reagent from the dispersion. The impregnated component is then washed, and the aqueous polymer dispersion is allowed to solidify.

[0062] Specifically, in a vacuum impregnation process, an impregnation chamber is typically used to hold the pre-impregnated component. The penetration of the aqueous dispersion of the present invention into the pores of the component can be aided by pressurizing the impregnation chamber with compressed air, as appropriate. A typical process using the aqueous dispersion of the present invention is described with reference to impregnating a porous component contained in a basket introduced into the impregnation chamber. This is a typical method for components of suitable small size. In the case of larger components, the components are typically mounted on or suspended from a lift or bracket. In a wet vacuum impregnation process, the basket of porous components is immersed in a vacuum tank filled with the aqueous dispersion of the present invention. A short (e.g., 10-12 minutes) vacuum cycle removes air from the pores of the component. The chamber is then restored to ambient pressure, and the dispersion penetrates into the evacuated pores.

[0063] The wet vacuum impregnation process is performed similarly, but the impregnation chamber is pressurized at the end of the vacuum cycle to force the impregnation composition further into the small pore channels. In the dry vacuum impregnation method, the basket of the porous component is placed directly in the dry vacuum chamber. Air is extracted from the pores of the component for a selected time, for example, 10 minutes. Then the delivery valve is opened, allowing the aqueous dispersion of the present invention to enter the vacuum chamber from the storage container. The chamber is automatically pressurized to force the aqueous dispersion of the present invention into the component. After impregnation, while the dispersion returns to the storage container, the basket is then allowed to suspend in free fall to remove excess surface dispersion. In the above methods, wet vacuum impregnation technology is generally more widely used than dry vacuum impregnation; however, either process is applicable to the present invention.

[0064] After the initial impregnation step, the impregnated parts are transferred, as appropriate, to an agitated water rinsing zone to remove any residual dispersion trapped in the grooves or screw holes of the impregnated parts. Agitation in the water rinsing zone may be influenced by the movement of the basket or suspension components within the zone and / or by mechanical components used to circulate water therein. Rinsing may be performed using water, surfactants, alkaline solutions, and trace amounts of alcohol. In cases where the basket contains small porous parts, it is often desirable to operate the water rinsing zone in a "tumbling basket" mode to enhance the washing effect. Subsequently, the impregnated parts may be transferred to a curing zone at a temperature of 50°C to 100°C for heating and curing, where self-crosslinking reactions can occur when acetylhydrazine or acetylacetic acid groups are present in the aqueous dispersion. In impregnation systems used at room temperature, after the impregnation process, the parts may be transferred to an oven for drying and then cooled overnight at room temperature. In use, the impregnation composition can be conventionally used in an impregnation chamber of a typical configuration, wherein a “wet” or “dry” vacuum is applied to the porous part to be impregnated, and the evacuated porous part is brought into contact with the impregnation composition at a higher (e.g., ambient) pressure, thereby allowing the impregnation composition to penetrate into the pores of the porous part to carry out its impregnation.

[0065] In another embodiment of the present invention, the use of the aqueous polymer dispersion of the present invention in pore sealing is provided.

[0066] The aqueous dispersion of the present invention, used as an impregnation composition, is characterized by excellent pore-sealing performance and good bonding strength for cast metal or parts co-molded from metal and plastic. Furthermore, compared to acrylic resin-based impregnation compositions, by using the aqueous dispersion of the present invention as an impregnation composition, the impregnated parts only require simple washing with a cleaning agent selected from water, surfactants, alkaline solutions, or alcohols and combinations thereof, which is an environmentally friendly technology. In addition, the preparation of the dispersion of the present invention, the vacuum impregnation technique using it, and the post-treatment are both extremely simple for commercial applications (e.g., waterproof electronic devices).

[0067] Examples 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 to these examples, but is defined in the appended claims. Unless otherwise stated, all parts and percentages are based on weight.

[0068] In the examples, the following abbreviations are used: AnAl: Aluminum anode; PBT: Polybutylene terephthalate; HDI: Hexamethylene diisocyanate; PAEK: Phthalosinone; PA: Poly(meth)acrylate; PUD: Polyurethane; VAE: Vinyl acetate / ethylene.

[0069] The raw material Acronal® V 215 is an aqueous dispersion of PA containing a carboxyl acrylate copolymer, wherein the acrylate copolymer has a Tg of -43°C and is available from BASF.

[0070] LUMIFLON®FE-4300 is an aqueous dispersion of PA containing polymers composed of alternating fluoroethylene and alkyl vinyl ether segments, wherein the PA polymer has a Tg of 30°C, and is available from AGC Chemicals.

[0071] VINNAPAS®EAF 68 series aqueous VAE dispersion, wherein the VAE polymer has a Tg of -35°C, is available from Wacker.

[0072] Basf 7104 is an aqueous PA dispersion of an acrylate copolymer containing carboxyl groups and having a Tg of -40°C, which can be purchased from BASF.

[0073] EM-123 is an aqueous PA dispersion of an acrylate copolymer containing carboxyl, hydroxymethyl and amide groups and having a Tg of -23°C. It is available from Guangzhou Lushan New Materials Co., Ltd.

[0074] BLJ-4122 is an aqueous PA dispersion of an acrylate copolymer containing carboxyl groups and having a Tg of -15℃, which can be purchased from Shanghai Baolijia Chemical Co., Ltd.

[0075] BLJ-3209 is an aqueous PA dispersion of an acrylate copolymer containing carboxyl and amide groups and having a Tg of -35°C. It is available from Shanghai Baolijia Chemical Co., Ltd.

[0076] Tekspro-7610 is an aqueous PA dispersion of an acrylate copolymer containing carboxyl, acetylhydrazine, and acetylacetyl groups and having a Tg of -13°C. It is available from Wanhua Chemical Co., Ltd.

[0077] An aqueous PA dispersion of DE-B series acrylate copolymer, which contains carboxyl, acetylhydrazine, acetylacetonate and phosphate groups and has a Tg of -12°C, is available from Wanhua Chemical Co., Ltd.

[0078] An aqueous PA dispersion of DE-C acrylate copolymer, wherein the acrylate copolymer contains carboxyl groups, acetylhydrazine, acetylacetonate, and phosphate groups and has a Tg of -20°C, is available from Wanhua Chemical Co., Ltd.

[0079] An aqueous PA dispersion of DE-D series acrylate copolymer, wherein the acrylate copolymer contains carboxyl groups, acetylhydrazine, acetylacetonate, and phosphate groups and has a Tg of -5°C, is available from Wanhua Chemical Co., Ltd.

[0080] DE-F-BLJ is an aqueous PA dispersion of a polymer containing carboxyl groups and having a Tg of -30℃, which can be purchased from Baolijia Chemical Co., Ltd.

[0081] DE-G is an aqueous PUD dispersion of an acrylate copolymer containing carboxyl groups and having a Tg of -10°C, sold by Wanhua Chemical Co., Ltd.

[0082] The ammonia solution with a concentration of approximately 25% to 28% was purchased from the Sinopharm Group.

[0083] Ethanolamine was purchased from Sinopharm Group.

[0084] D-sorbitol was acquired from Sinopharm Group.

[0085] Maltitol was acquired from Sinopharm Group.

[0086] Betaine was acquired from Sinopharm Group.

[0087] The sodium lactate with a concentration of approximately 60% was purchased from the Sinopharm Group.

[0088] BYK-348 is a polysiloxane surfactant containing an aqueous dispersion of polyether-modified siloxane, and is purchased from BYK.

[0089] The H-1400 was purchased from Guangzhou Hensic New Material Co., Ltd.

[0090] WM44-L70G is a block polyisocyanate based on HDI, purchased from Asahi Kasei.

[0091] Dynasylan® HYDROSIL 2926 is a water-based organosilicone compound and is available from Evonik.

[0092] TCI-E0327 is 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, which can be purchased from the TCI Group.

[0093] TCI-T3585 is 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane, which can be purchased from the TCI Group.

[0094] H-592 is a multifunctional polysilicon compound that is available from Guangzhou Hensic New Material Co., Ltd.

[0095] COAPUR™ 2025 is a solvent and an APE-free associative polyurethane thickener designed for use in water-based formulations, available from Contex.

[0096] BYK-024 is a mixture of defoaming polysiloxane and hydrophobic solids in polyethylene glycol, and can be purchased from BYK.

[0097] S-8370 is a defoamer containing polyether and mineral oil, which can be purchased from SAN NOPCO.

[0098] FoamStar®ST 2437 is an antifoaming agent for aqueous dispersions and is available from BASF.

[0099] Foamaster® MO 2134 is an antifoaming agent for aqueous dispersions and is available from BASF.

[0100] SN-DEFOAMER 475-L is a hydrophobic silica defoamer purchased from SAN NOPCO.

[0101] Test Method: Overlap Shear Strength: Overlap shear strength was determined based on ATSM D1002, with AnAl and PBT replaced by test materials. Specifically, a PBT laminate with dimensions of 2 cm width and 2 mm thickness was prepared, then coated with the sample dispersion, and then a metal spacer with a diameter of 0.127 mm was placed to control the sealant thickness. Subsequently, AnAl was attached to form a sandwich laminate with an effective sealing area of ​​20*10*0.127 mm. The sandwich laminate was then cured in an oven at 100°C for 2 hours, and then left at room temperature overnight. To determine the tensile strength at which the sealant layer breaks, the overlap shear strength of the sample was determined using an INSTRON tensile testing machine at a test speed of 5 mm / min. The failure load was recorded accordingly. A bond strength greater than 0.3 MPa was considered acceptable.

[0102] Leakage Resistance: The test component was made of aluminum laminate, with an H-shaped cutout in the center of the PBT molding. Another test component was of the same shape, co-molded from stainless steel SUS301 and PAEK. Both types of components had small holes between the metal and plastic. Vacuum impregnation was performed using the dispersion described in this invention. That is, the test component was placed in a vacuum impregnation tank. The vacuum phase was maintained for several minutes and then the vacuum was broken to allow the small holes of the component to be impregnated by the dispersion. During the impregnation phase, 5 bar of compressed air was introduced through the tank lid to pressurize the vacuum impregnation tank. If bubbles were observed escaping, the amount of leaked air (mL) was measured for 1 minute to evaluate the leakage resistance. After the impregnation phase, the vacuum impregnation tank was opened, and the test component was removed.

[0103] Use these two test components to test five samples for each instance. Record the air leakage amount (if any) for each sample, and calculate the average leaked air amount by arithmetic mean to evaluate the nature of the leak using the following scale: Scale Average air leakage rate (mL / min) A 0 B Greater than 0 and less than 0.05 C 0.05 to less than 0.1 D 0.1 to less than 0.2 E 0.2 to less than 0.5 F 0.5 to less than 0.8 Grade C or above is considered acceptable.

[0104] Examples 1 to 8 (Ex.1 to Ex.8) and Comparative Examples 1 to 5 (CE.1 to CE.5) used the amounts (parts by weight) of the components listed in Table 1 to prepare dispersions using the following methods, and tested the properties using the above methods. The evaluation results are shown in Table 1.

[0105] A method for preparing an aqueous dispersion comprises the following steps: (1) mixing emulsions (if more than one emulsion is present) at room temperature; (2) adding additives in the following order: neutralizer, anti-skinning agent, accelerator, thickener and defoamer (if any), and mixing thoroughly. Table 1 Components Ex 1 Ex 2 Ex 3 Ex 4 Ex 5 Ex 6 Ex 7 Ex 8 Acronal ® V 215 59.43 - - - - - - - LUMIFLON ® FE-4300 - 79.63 - - - - - - VINNAPAS ®EAF 68 - 20 - - - - - - BASF 7104 - - - - - - - - EM-123 - - - - - - - - BLJ-4122 - - - - - - - 79.1 BLJ-3209 - - - - - - - - Textpro-7610 - - - - - - - - DE-B 40 - 99.3 - - - - - DE-C - - - 99.38 - - 99.6 - DE-D - - - - 99.38 99 - - DE-F-BLJ - - - - - - - - DE-G - - - - - - - 20 ammonia - - 0.3 - - 0.5 - - ethanolamine 0.17 - 0.42 0.42 - - 0.5 D-sorbitol - - - - - - - - maltitol - - - - - - - - beet alkali - - - - - - - - Sodium lactate - - - - - - - - BYK-348 0.1 - 0.1 - - - - - H-1400 - - - - - - - 0.2 WM44-L70G - 0.17 - - - - - - Dynasylan ® HYDROSIL 2926 - - - - - - - - TCI-E0327 - - - - - - - - TCI-T3585 - - - - - - 0.2 - H-592 - - - - - 0.3 - - COAPUR™ 2025 0.1 - 0.1 - - - - - BYK-024 0.2 0.2 0.2 - - 0.2 - - S-8370 - - - 0.2 - - - 0.2 FoamStar ® ST 2437 - - - - - - - - Foamaster ® MO 2134 - - - - 0.2 - 0.2 - SN-DEFOAMER 475-L - - - - - - - - Solid content 64% 67% 61% 61% 61% 60% 61% 55% *Functional groups C, P, HZ, A C, HO, I, F, Si C, P, HZ, A C, P, HZ, A C, P, HZ, A C, P, HZ, A Si C, P, HZ, A, Si C Test Results AnAl / PBT combination 0.35 0.40 0.41 0.3 0.78 0.38 0.48 0.4 SUS leak-proof A A A A A A A C AnAl leak-proof A A A B B A A C * C represents carboxyl group; P represents phosphate ester group; HZ represents acetylhydrazine group; AC represents acetylacetonate group; HO represents hydroxyl group; I represents isocyanate group; F represents fluorine group; Si represents silyl group. Table 1 (continued) Components CE 1 CE 2 CE 3 CE 4 CE 5 Acronal ® V 215 99.5 99.8 - - - Basf 7104 - - 99.5 - - EM-123 - - - 50 - BLJ-4122 - - - - - BLJ-3209 - - - 49 - Tekspro-7610 - - - - 99.8 ethanolamine - - - 0.6 - BYK-348 0.3 - - - - TCI-E0327 - - 0.3 - - H-592 - - - 0.2 - BYK-024 0.2 0.2 - - 0.2 FoamStar® ST 2437 - - 0.2 - - SN-DEFOAMER 475-L - - - 0.2 - Solid content 68% 69% 60% 58% 50% *Functional groups C C C, Si C, HOM, AM C, P, HZ, AC Test Results AnAl / PBT combination 0.16 0.13 0.21 0.27 0.3 SUS leak-proof A A C D D AnAl leak-proof C D F D F * C represents carboxyl group; Si represents silyl group; AM represents amide group; HOM represents hydroxymethyl group; AC represents acetylacetonate group; P represents phosphate group; HZ represents acetylhydrazine group.

[0106] As can be seen from Table 1, compared with the comparative examples, the dispersion in the examples of the present invention exhibits excellent leak-proof properties on various materials when solidified and also maintains high lap shear strength.

[0107] Although some preferred embodiments have been described, many modifications and changes can be made to them based on the above teachings. Therefore, it should be understood that the present invention can be practiced in ways other than those specifically described without departing from the scope of the appended claims.

Claims

1. An aqueous polymer dispersion for a vacuum impregnation process, comprising at least one polymer having a carboxyl group and additional functional groups selected from the following: a combination of hydroxyl, isocyanate and fluorine, or a combination of phosphate, acetylhydrazine and acetyl acetate groups, wherein the polymer has a glass transition temperature greater than -40°C and less than 35°C, and the aqueous polymer dispersion has a solids content greater than 50% by weight.

2. The aqueous polymer dispersion of claim 1, wherein the aqueous polymer dispersion has a solid content of not less than 55% by weight.

3. The aqueous polymer dispersion of claim 1 or 2, wherein the polymer has a glass transition temperature of -30°C to 20°C.

4. An aqueous polymer dispersion as claimed in claim 1 or 2, wherein the polymer has a particle size (D50) of 0.2 to 8.0 μm.

5. An aqueous polymer dispersion as claimed in claim 1 or 2, wherein the polymer has a number average molecular weight of 8,000 to 300,000 g / mol.

6. The aqueous polymer dispersion of claim 1 or 2, wherein the polymer is selected from poly(meth)acrylate (PA), polyurethane (PUD), vinyl acetate / ethylene copolymer (VAE), acrylic acid-modified VAE, polyvinyl acetate (PVAc) or acrylic acid-modified PVAc and combinations thereof.

7. The aqueous polymer dispersion of claim 1 or 2, wherein the aqueous polymer dispersion further comprises at least one additive selected from neutralizers, skinning time extenders, adhesion promoters, thickeners, defoamers, and combinations thereof.

8. The aqueous polymer dispersion of claim 7, wherein the adhesion promoter comprises at least one silyl group.

9. The aqueous polymer dispersion of claim 7, wherein the amount of the additive is from 0.1% to 1.5% by weight based on the total weight of the dispersion.

10. A cured product of an aqueous polymer dispersion as claimed in any one of claims 1 to 9.

11. The cured product of claim 10 has a bond strength greater than 0.3 MPa on anodized aluminum and polybutylene terephthalate using the ATSM D1002 test method.

12. The cured product of claim 10 or 11 has an average air leakage rate of less than 0.1 mL / min on stainless steel.

13. The cured product of claim 10 or 11 has an average air leakage rate of less than 0.1 mL / min on aluminum.

14. A component comprising a cured product as claimed in any one of claims 10 to 13.

15. An electronic device comprising the components of claim 14.

16. A method for sealing pores in a component, comprising a) vacuum impregnating the component with an aqueous polymer dispersion as claimed in any one of claims 1 to 8 and b) curing the aqueous polymer dispersion at a temperature in the range of 50°C to 100°C.

17. Use of an aqueous polymer dispersion as claimed in any one of claims 1 to 9 in pore sealing.