Low-temperature elastic acrylic plastisol-based seam sealer

Abstract

The present invention aims to provide an acrylic plastisol composition comprising at least one acrylate polymer, at least one epoxy resin having more than one epoxide group per molecule on average, at least one latent curing agent for the epoxy resin, and at least one plasticizer, characterized in that the epoxy resin is liquid at 23°C and has a polyether main chain that is not based on bisphenol structural units. The acrylic plastisol composition according to the present invention can be used as a seam sealer on a metal substrate that will later be powder-coated at a temperature of 200°C or higher, and exhibits excellent low-temperature flexibility and bendability at a temperature of -25°C or lower.

Description

[Technical Field]

[0001] The present invention relates to an acrylic plastisol composition suitable for sealing metal surfaces that will be subsequently powder-coated. More specifically, the present invention relates to a plastisol composition that can be applied to manufactured articles or transported structures, such as automobiles, which cure at high temperatures and are powder-coated together with the manufactured articles or transported structures. [Background technology]

[0002] Various existing plastisol compositions are used in a variety of applications, such as surface coatings for waterproofing and sealing applications. Typically, plastisols consist of particulate matter of PVC or a PVC substitute suspended in a liquid plasticizer along with other additional additives to achieve the desired performance. Generally, compositions containing acrylate polymers and plasticizers are used to seal components of manufactured goods, particularly components of transport vehicles and home appliances.

[0003] Generally, it is desirable that the application of these plastisol compositions does not interfere with the processing, formation, or assembly of the manufactured articles. For example, it is extremely important that, when the composition is present at a welding location, it does not prevent or interfere with the welding of those elements. Furthermore, the composition materials should have good adhesion to metal surfaces, especially oil-covered metal surfaces.

[0004] Such plastisol compositions are also used in applications where parts of manufactured goods, such as the structure of an automobile, are bonded to each other by spot welding. In some applications, the structures are bonded to each other by a weld formed by spreading the applied composition. The compositions used in these applications are also called "welding sealer compositions" or "seam sealer compositions." In a typical welding application, the composition is applied to a part of a structure, which is then melted to form a bond with another part of the structure. After welding, the welded seam typically needs to be sealed with a seam sealer to flatten its surface and provide corrosion protection.

[0005] For example, welded structures such as manufactured goods or transport vehicles are typically coated after their manufacture to provide a protective and aesthetically pleasing surface. One common form of coating is powder coating. Powder coating is a type of coating applied as a free-flowing, dry powder. Unlike conventional liquid paints delivered via volatile solvents, powder coatings are typically applied electrostatically and then cured under heat or ultraviolet light. The powder may be a thermoplastic or thermosetting polymer. It is usually used to create a hard finish that is stronger than conventional paints. Powder coating is primarily used for coating metals, such as home appliances, aluminum extrusions, drum hardware, automobiles, and bicycle frames. Most powder coatings cure at around 180°C to 200°C for a minimum of 10 to 15 minutes. The seam sealer composition present on the object during the powder coating process must be able to withstand such harsh curing conditions. This has been done using PVC-based plastisols. However, PVC-based plastisols have limitations in terms of thermal stability.

[0006] Improved results were obtained by using acrylic plastisol, which has higher thermal stability than PVC-based plastisol. However, acrylic plastisol exhibits different drawbacks. Specifically, at extremely low temperatures, i.e., below -25°C, acrylic plastisol tends to become brittle and lose its flexibility.

[0007] To overcome this, several known reinforcing additives have been used in various attempts to improve the low-temperature flexibility of acrylic plastisols. However, they all have their own drawbacks.

[0008] For example, elastic urethane-based reinforcing additives, which are commonly found in powder coating processes, have limited thermal stability at baking temperatures above 200°C.

[0009] Blocked urethane additives in acrylic plastisols are generally detrimental to adhesion to treated or untreated metals and have poor compatibility with some polyester-based powder coatings, resulting in surface cracking on the coating and causing the coating surface to become sticky or greasy.

[0010] For example, U.S. Patent No. 7,332,539B2 discloses an acrylic plastisol containing a blocked urethane prepolymer.

[0011] As another example, Japanese Patent Publication No. 3727591B1 discloses a heat-curable composition comprising an acrylic sol and an alkylene oxide-modified glycidyl ether-type epoxy resin or a polyether urethane-modified epoxy resin.

[0012] Unblocked, isocyanate-functionalized urethane additives are generally incompatible with acrylic plastisols because almost all acrylic resins used in plastisol applications incorporate hydroxyl or amino functional groups into their matrix for adhesion purposes, and these react undesirably with the isocyanate groups.

[0013] Solid rubber or core-shell particle additives are also not ideal because they are difficult to compound into the plastisol composition, have poor material properties, and can lead to excessively high viscosity or reduced storage stability of packaged products.

[0014] As another example, International Publication No. 2021 / 189402A1 discloses e-coating compositions suitable for welding sealer applications, comprising acrylic polymers, epoxy resins, latent curing agents for epoxy resins, plasticizers, and conductive carbon allotropes. The epoxy resin is a bisphenol-type glycidyl ether resin.

[0015] Similarly, European Patent Application Publication No. 0 130 389A2 discloses a one-component, thermosetting, reactive plastisol composition comprising a thermoplastic resin in powder form, such as PVC, a liquid plasticizer having isocyanate groups, and, in some embodiments, polyepoxides. The polyepoxides disclosed therein mainly consist of polyglycidyl ethers of polyhydric alcohols. [Overview of the project] [Problems that the invention aims to solve]

[0016] Therefore, there is still a need for an acrylic plastisol composition that can be used as a seam sealer on a metal substrate to be powder-coated later and has excellent low-temperature flexibility and bendability at temperatures down to -25°C, preferably even lower temperatures.

Means for Solving the Problems

[0017] An object of the present invention is to provide an acrylic plastisol composition that can be used as a seam sealer on a metal substrate to be powder-coated later at a temperature of 200°C or higher and exhibits excellent low-temperature flexibility and bendability at temperatures up to -25°C, and in a preferred embodiment up to -4°C. Surprisingly, it has been found that the object can be achieved with the composition according to claim 1.

[0018] Other aspects of the present invention are presented in the other independent claims. Preferred embodiments of the present invention are presented in the dependent claims.

Mode for Carrying Out the Invention

[0019] The subject matter of the present invention is as follows: a) At least one acrylate polymer AP; b) At least one epoxy resin A, containing on average more than one epoxide group per molecule; c) At least one latent curing agent for the epoxy resin; d) At least one plasticizer PL; An acrylic plastisol composition comprising characterized in that the epoxy resin A is liquid at 23°C and has a polyether main chain not based on bisphenol structural units.

[0020] Substance names starting with "poly" formally refer to substances that contain two or more of the functional groups in their names per molecule. For example, polyol refers to a compound having at least two hydroxyl groups. Polyether refers to a compound having at least two ether groups.

[0021] The term "plastisol" preferably refers to a dispersion of a plastic, specifically, a polymer produced by emulsion polymerization or microemulsion polymerization in a high-boiling organic compound (which functions as a plasticizer for the polymer at a higher temperature). When the plastisol is heated, those plasticizers diffuse into the particulate matter of the dispersed plastic, where they are retained between the macromolecules, thereby plasticizing the plastic. When cooled, the plastisol gels into a flexible and dimensionally stable system. More preferably, the term refers to the definition described in Roempp Chemie Lexikon, online edition, Georg Thieme Verlag (searched on March 19, 2020).

[0022] The term "polymer" refers to a chemically homogeneous group of macromolecules produced by a polymerization reaction (polymerization, polyaddition, polycondensation), where the macromolecules differ in terms of degree of polymerization, molecular weight, and chain length. This term also includes derivatives of the above generic macromolecules obtained as a result of the polymerization reaction, that is, for example, compounds obtained by an addition reaction or substitution reaction of functional groups in a predetermined macromolecule, and they may be either chemically homogeneous or chemically heterogeneous.

[0023] The term "glass transition temperature" (T g ) refers to a temperature at which, above it, the polymer components become soft and bendable, and below it, it becomes hard and glassy. The glass transition temperature (T gIt is preferable to measure this as the peak of the loss modulus (G") curve measured by dynamic mechanical analysis (DMA) with a frequency of 1 Hz and a strain of 0.1%.

[0024] "Median particle size d 50 " refers to the particle size of the solid particle population when the cumulative percentage reaches 50%. For example, median particle size d 50 In the case of a powder sample with a median particle size of d = 5 μm, this means that 50% of the particulate matter is larger than 5 μm and 50% of the particulate matter is smaller than 5 μm. 50 Preferably, this is determined by laser diffraction analysis in accordance with ISO 13320:2009, for example, by measurement using a CILAS 920 particle size analyzer (Cilas) or a Malvern Mastersizer 3000 (Malvern).

[0025] The terms "shelf-life stability," "shelf stability," and "storage stability" refer to the performance of a composition when stored at room temperature in a suitable container under moisture barrier conditions for a certain period of time, specifically several months, without any significant change in its performance at the application or end use.

[0026] The term "molecular weight" refers to the molar mass (g / mol) of a molecule or a residue of a molecule. The term "average molecular weight" refers to the number-average molecular weight (M) of an oligomeric or polymeric mixture of molecules or residues of a molecule. n This refers to the refractive index (RFA). It is generally measured by gel permeation chromatography (GPC) with polystyrene as the standard, particularly with tetrahydrofuran as the mobile phase, and using a refractive index detector.

[0027] Unless otherwise specified, the terms "weight %" or "wt%" refer to the mass fraction of a particular component of a composition relative to the entire composition. In this document, the terms "weight" and "mass" are used synonymously.

[0028] The term "room temperature" refers to a temperature of 23°C.

[0029] All industrial standards and specifications referred to herein, unless otherwise specified, refer to the most recent versions in effect at the time of the initial application.

[0030] The composition preferably contains at least one acrylate polymer AP in amounts of 5-40 wt%, 10-40 wt%, 12.5-40 wt%, more preferably 15-35 wt%, even more preferably 17.5-32.5 wt%, and most preferably 20-30 wt%, based on the total weight of the composition.

[0031] The acrylate polymer AP is preferably selected from a list consisting of polymers of methyl acrylate, ethyl acrylate, methyl methacrylate, propyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, and various copolymers thereof.

[0032] These acrylate polymers (APs) can be obtained from commercial sources such as: Degalan® BM310 (homopolymer from Evonik), Degalan® 4944F (homopolymer from Evonik), Kane Ace® UC521 (manufactured by Kaneka), Kane Ace® UC506 (manufactured by Kaneka), and Kane Ace® UC508 (manufactured by Kaneka), as well as Dianal® LP-3106 and Dianal® LP-3121 (both manufactured by Mitsubishi).

[0033] Preferably, more than 40%, more than 50%, more than 60%, more than 70%, more than 80%, or more than 90% of the acrylate polymer AP is a methacrylate polymer or a copolymer containing methacrylate.

[0034] The glass transition temperature (Tg) of the acrylate polymer AP is preferably 60°C to 120°C, 70°C to 100°C, and more preferably 75°C to 80°C.

[0035] The acrylate polymer AP can take various forms as provided by the manufacturer, such as: bead polymers, pellets, granules, powders, spray-dried emulsion polymers, etc. The median particle size d of the acrylate polymer AP before use. 50 The particle size can be in the range of 1 to 100 μm, preferably 10 to 80 μm, 20 to 60 μm, and most preferably 40 to 60 μm.

[0036] The acrylate polymer AP has the following characteristics: (i) bulk density of approximately 350 to 450 grams / liter; (ii) glass transition temperature of 70°C to 80°C; and (iii) median particle size of 40 to 60 microns. 50 It is preferable that it has [this feature].

[0037] The composition comprises at least one epoxy resin A, which on average contains more than one epoxide group per molecule. Epoxy resin A is liquid at 23°C and has a polyether main chain that is not based on bisphenol structural units. Preferably, the epoxide groups are in the form of glycidyl ether groups.

[0038] It is preferable that the epoxy resin A has an epoxy equivalent of more than 400 and / or an average epoxy functional value between 1.5 and 2.5. It is more preferable that the epoxy resin A has an epoxy equivalent of more than 400 and an average epoxy functional value between 1.5 and 2.5.

[0039] The epoxy equivalent and / or the average epoxy functionality of epoxy resin A can be determined by potentiometric titration, for example, in accordance with EN ISO 3001 and ASTM D1652. The epoxy equivalent and / or the average epoxy functionality of epoxy resin A is preferably determined in accordance with EN ISO 3001 using an automatic titrator, such as Metrohm 905 Titrando (available from Metrohm, Switzerland) equipped with Solvotrode easyClean.

[0040] The amount of epoxy resin A in the composition is, based on the total weight of the composition, in particular 1 to 25 wt%, preferably 2 to 20 wt%, in particular 3 to 15 wt%, more preferably 5 to 12 wt%.

[0041] The epoxy resin A is a liquid epoxy resin at 23 °C and standard pressure. The term "standard pressure" refers to an atmospheric pressure of 100 kPa (1 bar) as defined by IUPAC.

[0042] Preferred epoxy resin A has the formula (I).

Chemical formula

[0046] The epoxy resin A preferably exhibits a viscosity of less than 5 Pa·s, preferably less than 2.5 Pa·s, more preferably less than 1 Pa·s, and most preferably less than 0.5 Pa·s, as measured at 25°C according to ASTM D445-21.

[0047] Preferably, the composition according to the present invention does not contain any other epoxy resins other than epoxy resin A. In particular, the composition further does not contain PVC.

[0048] The composition further includes at least one latent curing agent for epoxy resins. The latent curing agent is substantially inert at room temperature but is activated by heating, typically at temperatures above 70°C, thereby initiating the curing reaction of the epoxy resin. Conventional latent curing agents for epoxy resins can be used. Preferably, these are epoxy resin latent curing agents containing nitrogen.

[0049] The latent curing agent is preferably selected from the group consisting of: dicyandiamide, guanamine, guanidine, aminoguanidine and their derivatives, substituted ureas, imidazoles, and amine complexes, preferably dicyandiamide.

[0050] The amount of the latent curing agent is preferably 0.1 to 1.5 wt%, more preferably 0.15 to 1.0 wt%, and most preferably 0.2 to 0.5 wt%, based on the total weight of the composition. Preferably, at least one of the latent curing agents is dicyandiamide.

[0051] The weight ratio of the total amount of at least one epoxy resin A to the total amount of latent curing agent is preferably 40:1 to 10:1, more preferably 35:1 to 15:1, and more preferably 30:1 to 20:1.

[0052] Furthermore, the composition further comprises at least one plasticizer PL.

[0053] The at least one plasticizer PL is preferably the following: - Dibasic acid esters, preferably dioctyl adipic acid (DOA), dioctyl azelaic acid (DOZ), and dioctyl sebacate (DOS); - Phosphate esters, preferably tricresyl phosphate (TCP), trioctyl phosphate (TOF), trixylenyl phosphate (TXP), monooctyl diphenyl phosphate, and monobutyl-dixylenyl phosphate (BZX); - Benzoic acid ester; - Other esters, preferably tributyl citrate, trioctyl-acetyl citrate, trimellitic acid, citrate, sebacate, azelaic acid, maleic acid, tri- or tetra-ethylene glycol esters of C6-C10 fatty acids, alkyl sulfonic acid esters, and methylacetyl ricinoleate; - Saturated fatty acid glycerides; - Epoxy vegetable oil; - Phthalate esters, preferably diisononyl phthalate (DINP) or dioctyl phthalate (DOP) It is selected from a list consisting of the following.

[0054] It is most preferable that at least one of the plasticizers PL contains an aliphatic polyester that is liquid at 23°C. Among these, polymeric or oligomeric polyesters are preferred, such as products available under the trade names below: Palamol® from BASF, particularly Palamol® 652, or trimellitic acid esters, such as Palatinol® TOTM (available from BASF).

[0055] For example, aromatic esters such as phthalates are not very desirable as plasticizers, but they are still perfectly suitable. However, at extremely high temperatures, i.e., above 200°C, some of them tend to smoke, although this is extremely rare with aliphatic polyesters.

[0056] The composition preferably contains at least one plasticizer PL in an amount of 5-50 wt%, 10-40 wt%, preferably 12.5-40 wt%, more preferably 15-35 wt%, and most preferably 20-30 wt%, based on the total weight of the composition.

[0057] The weight ratio between the total weight of at least one plasticizer PL and the total weight of at least one acrylate polymer AP is preferably 1:10 to 20:10. More preferred ranges for this weight ratio include: 2:10 to 15:10, 2:10 to 15:10, 5:10 to 15:10, 5:10 to 10:10, 6:10 to 10:10, and 8:10 to 10:10.

[0058] It is even more advantageous that the composition contains less than 10% by weight, less than 5% by weight, less than 2% by weight, less than 1% by weight, less than 0.5% by weight, particularly less than 0.1% by weight, most preferably less than 0.01% by weight of PVC, or contains no PVC at all. This is advantageous for the following reason: the high temperatures required to cure the composition cause PVC to release toxic hydrogen chloride gas, which poses an occupational hazard in work involving the composition.

[0059] It is even more preferable that the composition contains at least one additive selected from the following: curing accelerators, reinforcing agents, moisture scavengers, fillers, pigments, stabilizers, process oils, and thixotropic agents. These additives are incorporated into the composition in various combinations.

[0060] Preferably, the composition further contains at least one type of process oil.

[0061] If at least one of the process oils is used, it is preferable that it be present in the composition in an amount of 1 to 10 wt%, more preferably 2 to 8 wt%, and even more preferably 3 to 6 wt%, based on the total weight of the composition.

[0062] Suitable process oils include mineral oils and synthetic oils. In the disclosure of the present invention, the term "mineral oil" means an oil derived from crude oil and subjected to one or more refining and / or hydrotreatment steps, such as fractional distillation, hydrocracking, dewaxing, isomerization, and hydrofinishing, to which the components have been refined and chemically modified to achieve a series of final performances, with a lubricating viscosity (i.e., 100°C, 10%). -6 m 2 This refers to liquid hydrocarbons having a kinematic viscosity of 1 / s or more. Specifically, in the disclosure of this invention, the term "mineral" refers to refined mineral oil, which can be defined as Group I to III base oils according to the classification of the American Petroleum Institute (API).

[0063] Preferred mineral oils for use as at least one type of process oil include paraffinic, naphthenic, and aromatic mineral oils. Particularly preferred mineral oils are paraffinic and naphthenic oils, which preferably contain only a relatively low amount of aromatic components, for example, 25 wt% or less, preferably 15 wt% or less, based on the total weight of the mineral oil.

[0064] In preferred embodiments, the composition further comprises at least one particulate filler F preferably selected from the group consisting of: ground or precipitated calcium carbonate, lime, calcium magnesium carbonate, talcum, gypsum, barite, pyrolysis or precipitated silica, silicate, mica, wollastonite, kaolin, feldspar, chlorite, bentonite, montmorillonite, dolomite, quartz, cristobalite, calcium oxide, aluminum hydroxide, magnesium oxide, hollow ceramic spheres, hollow glass spheres, hollow organic spheres, glass spheres, kaolin, and functionalized aluminumoxane. Suitable solid particulate fillers include the fillers listed above, both with and without organic coatings, in commercially available forms.

[0065] Preferably, at least one type of solid particulate filler F is in the form of finely milled particulate matter. The term "finely milled particulate matter" refers to its median particle size d 50 However, this refers to particulate matter that does not exceed 500 μm, and especially 250 μm. The particle size distribution of particulate packing materials can be determined by sieve analysis according to the method described in the ASTM C136 / C136M-14 standard ("Standard Test Method for Sieve Analysis of Fine and Coarse Aggregates").

[0066] In one or more embodiments, the at least one particulate filler F includes at least one filler selected from the list consisting of ground or precipitated calcium carbonate, calcium oxide, lime, calcium magnesium carbonate, talcum, gypsum, graphite, barite, silica, silicate, mica, wollastonite, kaolin, and mixtures thereof, more preferably selected from the list consisting of ground or precipitated calcium carbonate, calcium oxide, silica, kaolin, and mixtures thereof. Calcium oxide has the additional benefit of also functioning as an effective desiccant in the composition, thereby improving storage stability and suppressing undesirable side reactions.

[0067] In one or more embodiments, at least one particulate filler F accounts for 10 to 50 wt%, preferably 15 to 45 wt%, more preferably 20 to 40 wt%, and even more preferably 25 to 35 wt%, of the total weight of the composition.

[0068] The composition may further contain at least one foaming agent.

[0069] Suitable blowing agents include chemical blowing agents and physical blowing agents. Chemical blowing agents are organic or inorganic compounds that decompose, for example, under the influence of temperature or humidity, and the at least one decomposition reaction product formed therefrom is a gas. Physical blowing agents include, but are not limited to, compounds that become gaseous at certain temperatures. It is preferable that at least one of the blowing agents is a chemical blowing agent.

[0070] Suitable chemical blowing agents include, but are not limited to, azo compounds, hydrazides, nitroso compounds, carbamates, carbazides, bicarbonates, polycarboxylic acids, and salts of polycarboxylic acids.

[0071] It is preferable that the composition has viscosities of 1000-3000 Pa·s (0.1 / s), 300-1000 Pa·s (1 / s), 80-250 Pa·s (10 / s), and 10-50 Pa·s (100 / s) when measured at 23°C using a rheometer with a heating plate (MCR 201, Anton Paar) with a gap of 1000 μm, a measuring plate diameter of 25 mm (plate / plate; PP25-SN13401), and a shear rate of 0.01 / s to 650 / s.

[0072] Higher viscosities, especially at lower shear rates (specifically 0.1 / s), are less desirable because they are not suitable for industrial bonding applications.

[0073] In one preferred embodiment, the composition includes: - At least one acrylate polymer AP, in an amount of 5-40 wt%, 10-40 wt%, 12.5-40 wt%, more preferably 15-35 wt%, even more preferably 17.5-32.5 wt%, and most preferably 20-30 wt%, based on the total weight of the composition; - At least one epoxy resin A having an average of more than one epoxide group per molecule, preferably having an epoxy equivalent of more than 400 and / or an average epoxy functional value between 1.5 and 2.5, in an amount of 1 to 25 wt%, preferably 2 to 20 wt%, particularly 3 to 15 wt%, more preferably 5 to 12 wt%, based on the total weight of the composition; - At least one latent curing agent for epoxy resins, selected from the group consisting of dicyandiamide, guanamine, guanidine, aminoguanidine and their derivatives, substituted ureas, imidazoles and amine complexes, preferably dicyandiamide; - At least one plasticizer PL (the at least one plasticizer PL preferably contains or consists of an aliphatic polyester that is liquid at 23°C), in an amount of 5-50 wt%, 10-40 wt%, preferably 12.5-40 wt%, more preferably 15-35 wt%, even more preferably 17.5-32.5 wt%, and most preferably 20-30 wt%, based on the total weight of the composition: - Preferably, at least one particulate filler F (preferably selected from the list consisting of ground or precipitated calcium carbonate, calcium oxide, silica, kaolin, and mixtures thereof), in an amount of 10 to 50 wt%, preferably 15 to 45 wt%, more preferably 20 to 40 wt%, and even more preferably 25 to 35 wt%, of the total weight of the composition; - Preferably at least one additive, selected from curing accelerators, strengtheners, moisture scavengers, pigments, stabilizers, and thixotropic agents.

[0074] In the above composition, it is preferable that the weight ratio of the total amount of at least one epoxy resin A to the total amount of the latent curing agent is 40:1 to 10:1, preferably 35:1 to 15:1, and more preferably 30:1 to 20:1.

[0075] In the above composition, it is even more preferable if the weight ratio between the total weight of at least one plasticizer PL and the total weight of the acrylate polymer AP is in the range of 1:10 to 20:10, preferably 2:10 to 15:10, 2:10 to 15:10, 5:10 to 15:10; 5:10 to 10:10, 6:10 to 10:10, and most preferably 8:10 to 10:10.

[0076] In the above composition, it is even more preferable that the composition does not contain any epoxy resin other than epoxy resin A.

[0077] Furthermore, it is preferable that the composition does not contain PVC.

[0078] The preferred composition described above may be even more advantageous if it consists of the aforementioned components in an amount of more than 80% by weight, preferably more than 90% by weight, particularly more than 95% by weight, especially preferably more than 98% by weight, and most preferably more than 99% by weight, based on the total weight of the composition.

[0079] The compositions according to the present invention can be produced by mixing their components in various suitable mixing devices, such as: a dispersion mixer, a planetary mixer, a twin-screw mixer, a continuous mixer, an extruder, or a twin-screw extruder.

[0080] The compositions according to the present invention obtained using the process described above are storage stable under normal storage conditions. The term "storage stable" here refers to a substance that can be stored for a long period of time, for example, at least one month, and especially at least three months, under specific storage conditions without causing any significant change in its usability. The term "typical storage conditions" in this case refers to a temperature of 40°C or lower, and especially 30°C or lower.

[0081] Another subject of the present invention is a method for sealing a manufactured article, preferably a structure of an automobile, which will later be powder-coated, and the method includes the following steps: i) A step of forming a weld that joins the first member and the second member of the structure (both the first and second members have an outward-facing contact surface and an inward-facing contact surface), ii) The step of applying the composition according to the present invention onto the weld seam, iii) bringing the welded structure and the sealed welded seam obtained in step ii) into contact with a powder coating, and curing the powder coating and the composition according to the present invention, particularly the structure, by heating at a temperature of 140 to 220°C, particularly 160 to 200°C, preferably 180 to 190°C, for particularly 10 to 60 minutes, particularly preferably 20 to 45 minutes.

[0082] It is preferable to perform Steps i) to iii) in this order, starting with Step i).

[0083] The welding that joins the first member and the second member can be formed using various appropriate welding techniques, such as electrical resistance welding or spot welding.

[0084] In step iii), the plasticizer PL diffuses into the dispersed acrylate polymer AP, thereby plasticizing the composition and achieving curing. Upon cooling, the composition gels, becoming a dimensionally stable system. Through a simultaneous generation mechanism, epoxy resin A is cured under heated conditions using a latent curing agent.

[0085] The first member of the structure may be made of the same material as the second member, or it may be made of a different material.

[0086] Applications in which at least one material is metal are preferred. In particular, in white body construction in the automotive industry, the use of the same or different metals is considered a particularly preferred application. Preferred metals include steel sheets, especially electroplated steel sheets, hot-dip plated steel sheets, oil-coated steel sheets, bonazinc-coated steel sheets, and subsequently phosphate-coated steel sheets, as well as aluminum, especially its variants that typically arise in automobile manufacturing.

[0087] Therefore, it is preferable that the first member of the structure and / or the second member of the structure be made of metal.

[0088] Furthermore, it is advantageous that, prior to step iii), the applied composition has not cured, in particular, not fully cured, and in particular, has not cured even when the composition is heated at a temperature of 140-220°C for 10-60 minutes, and especially preferably 20-45 minutes.

[0089] Such a method of providing a seal to the structure of a manufactured article gives the article, which also represents a further aspect of the present invention. Such articles are preferably vehicles, preferably automobiles or parts of vehicles.

[0090] Another subject of the present invention is the use of the composition as a plastisol seam sealer on a substrate as described above, according to various embodiments of the present invention, the substrate being powder-coated after the application of the aforementioned seam sealer. This use is preferably carried out by employing the method described above.

[0091] In the preferred embodiment of the above use, the seam sealer is exposed to a temperature of 140-220°C, particularly for 10-60 minutes, during the powder coating process. [Examples]

[0092] Preparation of composition Reference composition R1 and compositions E1 to E3 according to the present invention were manufactured from the raw materials listed in Table 1.

[0093] Table 2 shows the detailed composition (weight percentage values ​​for each composition). Each composition was prepared by mixing the listed components in a standard mixer equipped with a dissolver blade, and then filled into an airtight cartridge.

[0094] [Table 1]

[0095] [Table 2]

[0096] Test method Examples R1 and E1-E3 were subjected to low-temperature mandrel bending tests according to SAE J243 (1971) (ADS-2-Low temperature tests, 4.2 Method B (Bend Test)).

[0097] The substrate used in the bending test was 0.05 mm thick aluminum foil.

[0098] The substrate was pre-treated / washed using the following chemicals: Immerse the sample in a 3% diluted solution of concentrated Linc Clean® 2706M (Lincoln Chemical Corp.) at 40°C for 5 minutes, then in a 2% diluted solution of concentrated Linc Phos® 4262SW (Lincoln Chemical Corp.) at 40°C for 5 minutes, and finally in a 1% diluted solution of concentrated Linc Seal® 3308 (Lincoln Chemical Corp.) at 40°C for 5 minutes.

[0099] The sealant composition for testing was first applied as beads onto aluminum foil to a thickness of approximately 2.5 millimeters.

[0100] Two types of samples were used in each experiment: one was uncoated, and the other was coated with a polyester-TGIC-based powder coating.

[0101] Each sample was baked at 204°C (400°F) for 30 minutes, which is a very typical procedure for curing powder coatings.

[0102] Subsequently, a mandrel bending test (the mandrel used for the bending test had a diameter of 1 inch (2.56 cm)) was performed at various temperatures (details in Table 3) according to the SAE J243 standard test specified above. A sample was deemed to have passed ("Pass") if it could be bent 180 degrees without cracking or / or losing adhesion. Samples that cracked or / or lost adhesion to the substrate during the bending test were deemed to have failed ("Fail"). This test allows for the evaluation of the low-temperature flexibility and bendability of the sample composition.

[0103] Viscosity data was obtained using an Anton Paar rheometer (using a 25mm diameter plate PP25-SN13401, gap: 1mm, measurement: 23°C, shear rate: 0.01~650 / s, test time: 49 minutes, sampling every 1 second). Viscosity measurements were performed on two samples: one stored at 23°C for 7 days prior to the 23°C measurement, and another of the same material stored at 40°C for 7 days prior to the 23°C measurement. The latter constituted an artificially aged sample, allowing for the evaluation of the storage stability of each composition compared to a fresh sample.

[0104] The results of those measurements are shown in Table 3.

[0105] [Table 3]

Claims

1. Acrylic plastisol composition, e) At least one acrylate polymer AP; f) At least one epoxy resin A containing more than one epoxide group per molecule on average; g) At least one latent curing agent for epoxy resins; h) At least one type of plasticizer PL; Includes, A composition characterized in that the epoxy resin A is liquid at 23°C and has a polyether main chain that is not based on bisphenol structural units.

2. The composition according to claim 1, wherein the epoxy resin A has an epoxy equivalent of more than 400 and / or an average epoxy functional value of 1.5 to 2.

5.

3. The composition according to any one of claims 1 to 2, wherein the amount of epoxy resin A is 1 to 25 wt%, preferably 2 to 20 wt%, particularly 3 to 15 wt%, and more preferably 5 to 12 wt%, based on the total weight of the composition.

4. The composition according to any one of claims 1 to 3, wherein the amount of the at least one acrylate polymer AP is 5 to 40 wt%, 10 to 40 wt%, 12.5 to 40 wt%, more preferably 15 to 35 wt%, even more preferably 17.5 to 32.5 wt%, and most preferably 20 to 30 wt%, based on the total weight of the composition.

5. The composition according to any one of claims 1 to 4, wherein the at least one acrylate polymer AP is selected from a list consisting of polymers of methyl acrylate, ethyl acrylate, methyl methacrylate, propyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, and various copolymers thereof.

6. The composition according to any one of claims 1 to 5, wherein the epoxy resin A exhibits a viscosity of less than 5 Pa·s, preferably less than 2.5 Pa·s, more preferably less than 1 Pa·s, and most preferably less than 0.5 Pa·s, as measured at 25°C according to ASTM D445-21.

7. The composition according to any one of claims 1 to 6, wherein the latent curing agent is selected from the group consisting of dicyandiamide, guanamine, guanidine, aminoguanidine and their derivatives, substituted ureas, imidazoles and amine complexes, and is preferably dicyandiamide.

8. The composition according to any one of claims 1 to 7, wherein the weight ratio of the total amount of at least one epoxy resin A to the total amount of the latent curing agent is 40:1 to 10:1, preferably 35:1 to 15:1, and more preferably 30:1 to 20:

1.

9. The composition according to any one of claims 1 to 8, wherein the at least one plasticizer PL comprises an aliphatic polyester that is liquid at 23°C.

10. The composition according to any one of claims 1 to 9, wherein the composition contains at least one plasticizer PL in an amount of 5 to 50 wt%, 10 to 40 wt%, preferably 12.5 to 40 wt%, more preferably 15 to 35 wt%, and most preferably 20 to 30 wt%, based on the total weight of the composition.

11. The composition according to any one of claims 1 to 10, wherein the composition comprises at least one latent curing agent, particularly dicyandiamide, in an amount of 0.1 to 1.5 wt%, preferably 0.15 to 1.0 wt%, and most preferably 0.2 to 0.5 wt%, based on the total weight of the composition.

12. The composition according to any one of claims 1 to 11, wherein the composition further comprises at least one additive selected from curing accelerators, strengtheners, moisture scavengers, fillers, pigments, stabilizers, and thixotropic agents.

13. The composition according to any one of claims 1 to 12, wherein the composition does not contain any other epoxy resin other than epoxy resin A, and the composition does not contain PVC.

14. Use of the composition according to any one of claims 1 to 13 as a plastisol seam sealer on a substrate, wherein the substrate is powder-coated after the application of the seam sealer.

15. The use according to claim 14, wherein the seam sealer is exposed to a temperature of 140 to 220°C, particularly for 10 to 60 minutes, during the powder coating process.

Images