WO2025252549A1

WO2025252549A1 - Polyamide particle foam moldings with low oil uptake

Info

Publication number: WO2025252549A1
Application number: PCT/EP2025/064685
Authority: WO
Inventors: Daniela Longo-Schedel; Patrick Spies; Juergen Kaczun
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 2024-06-07
Filing date: 2025-05-27
Publication date: 2025-12-11
Anticipated expiration: 2026-12-07

Abstract

The present invention provides a polyamide particle foam molding with low oil-uptake and a coating comprises an acrylate resin on at least part of the surface as well as a process for producing the polyamide particle foam molding and its use as batterie cell holder.

Description

Polyamide particle foam moldings with low oil uptake

Description

The present invention relates to a polyamide particle foam molding with low oil-uptake and a coating on at least part of the surface as well as a process for producing the polyamide particle foam molding and its use as batterie cell holder.

Relevant Prior Art

Particle foams based on polyamide are known since the 1980 as disclosed in JP61-268737. Most particle foams made from partial crystalline polyamides, like PA6; PA66 and PA6/66 have good mechanical properties, even at temperatures above 150°C.

WO 2021/052881 A1 discloses polyamide foam particles obtainable with low bulk densities by a continuous one-step process and polyamide particle foam moldings obtainable by steam-chest molding with high temperature stability which particularly are suitable to pass high temperature conditions like an electrodeposition coating process.

Polyamides show a high stability against aliphatic oils, such as gear oil, thermal oils for cooling systems, fuels, paraffins or isoparaffinic compounds. Due to the porous surface and interspace between the fused particles of polyamide particle foam moldings they could take up liquids via capillary effect, which leads to weight increase and limits their application fields.

WO 2021/151688 A2 relates to a process of coating wood with at least two water-based coating compositions comprising applying a coating composition comprising an aqueous anionic polymer A with a Hansch parameter <1.6, as an undercoat for coating wood.

EP 1 566 400 A2 relates to particle or extrusion foam plates having a coating on at least one plate surface wherein the coating comprises a polymer film, has a glass transition temperature in the range of from -60 to + 40 °C has, as well as includes a method for the production thereof by coating and drying a polymer dispersion. Preferably styreneacrylate or styrene-butadiene-copolymers are used as film building resins. Summary of the Invention

The present invention was made in view of the prior art described above, and the object of the present invention is to provide polyamide particle foam moldings with low oil uptake and an easy applicable process for manufacturing such polyamide foam moldings.

Technical problem solved

To solve the problem, the present invention provides a polyamide particle foam molding with a coating on at least part of the surface, wherein the coating comprises an acrylate resin.

Preferably the coating is applied on the whole surface of the polyamide particle foam molding.

Preferably the oil uptake of the polyamide particle foam molding is less than 12-wt.-%, more preferably less than 10 wt.-% after storage of 500 h at 80°C in isoparaffinic hydrocarbon fluid.

The polyamide particle foam molding may be obtained by steam-chest molding of polyamide foam particles as described in WO 2021/052881 A1 . Preferably the polyamide particle foam molding has a part density in the range from 300 to 600 kg/m³ and a closed cell ratio from 85 to 95 vol.-%.

Polyamide

The polyamide of the polyamide particle foam molding may be a homopolyamide obtained from polymerization of lactams, such as caprolactames or lauryllactames, condensation products of diamines and dicarboxylic acids, copolyamides thereof or mixtures of two or more different polyamides.

Preferably the polyamide is selected from partially crystalline polyamides having a melting point in the range from 150 to 350°C determined according to DIN EN ISO 11357-3: 2014.

Also particularly preferred are polyamides having a crystallinity of more than 20%, preferably in the range from 25 to 60%, determined by means of differential scanning calorimetry (DSC) according to DIN EN ISO 11357_3_2018 by integration of the melting signal, I. a crystallinity of 100% corresponds to 230 J / g (Journal of Polymer Science Part B Polymer Physics 35 (1997) 2219-2231).

Preferably the polyamide comprises at least one polyamide selected from the group consisting of polycaprolactam (PA6), polybutylene adipamide (PA 4.6), polyhexamethylene adipamide (PA 6.6), polyhexamethylene sebacamide (PA 6.10), polyhexamethylene dodecanamide (PA 6.12 ), Poly-1 1 - aminoundecanamide (PA 11), polylaurolactam (PA 12), poly-mxylylene adipamide (PAMXD 6), polypentamethylene sebacamide (PA 510), 6T / Z (Z = lactam), 6T I 6I, 6T / 6I / XY, 6T / XT (X = straight-chain or branched C4-C18-diamine), XT (X = C4-C18-diamine), 6.12. PA PACM 12 (PACM = p-diaminodicyclohexylmethane), PA MACM 12 (MACM = 3,3-dimethyl-pdiaminodicyclohexylmethane), PA MPMD 6 (MPMD 2-methyl pentamethylene diamine), PA MPMD T, PA MPMD 12, polyhexamethylene isophthalamide (PA 6I ), polyhexamethylene isophthalamide cohexamethylene terephthalamid (PA 6I/6T), PA 6-3-T (terephthalic acid polyamide and mixtures of 2,2,4- and 2,4,4-trimethylhexamethylenediamine), polybutylene sebacamide (PA 4.10), polydecamethylene sebacamide (PA 10.10), polypentamethylene adipamide (PA 5.6), PA 6/66 and PA 66/6, PA 6Y (Y = C4-C18-diacid) and their transamidation products

Most preferably the polyamide particle foam molding is made from polyamides selected from the group consisting of polycaprolatam (PA6), polylaurolactam (PA 12, polyhexamethylene adipamide (PA 6.6), poly-hexamethylene sebacamide (PA 6.10), polyhexamethylene dodecanamide (PA 6.12), PA 6/66, PA 66/6, PA 6I/6T and copolyamide PA6/6.36 or mixtures therefrom.

The polyamide may comprise additives, such as nucleating agents, dyes, pigments, flame retardant, waxes, antioxidants, stabilizers, IR-absorber and/or inorganic fillers.

Heat stabilizers or antioxidants, or a mixture of these, may be selected from the group of the copper compounds, ste- rically hindered phenols, sterically hindered aliphatic amines, and/or aromatic amines. Preferred salts of monovalent copper are cuprous acetate, cuprous chloride, cuprous bromide, and cuprous iodide, which can be used in combination with potassium or sodium halogenides e.g. potassium iodide.

The polyamide particle foam molding has a coating on at least part of the surface. The coating comprises an acrylate resin.

Preferably the coating consists of an acrylate resin and is covering the whole surface of the polyamide particle foam molding.

Preferably the coating has a thickness in the range from 40 to 60 pm.

Preferably the polyamide particle foam molding is free of the acrylate resin.

Preferably the coating is free of the polyamide.

Preferably the coating and the polyamide particle foam are different materials, which usually means that the coating and the polyamide particle foam have a different chemical composition. Coating

Preferably the coating composition comprises an acrylate resin with a Hansch parameter less than 2, preferably in the range from 0.1 to 1.8 and particularly preferably in the range from 0.2 to 1.3.

The acrylate resin is preferably formed from at least the monomers A1, A2 and A3. Acrylate resin with a Hansch parameter less than 2 means that the nature and amounts of monomers A1 and A2 and A3 and optional additional monomers have been chosen here such that the acrylate resin has a Hansch parameter of less than 2.

The Hansch parameters are generally a measure of the hydrophobicity of monomers M and the polymers P formed therefrom.

The theoretical considerations for the calculation of the Hansch parameters come from: Hansch, Fujita, J. Amer. Chem. Soc., 1964, 86, pages 1616-1626; H. Kubinyi, Methods and Principles of Medicinal Chemistry, Volume 1, R. Mannhold et al., publisher: VCH, Weinheim (1993); C. Hansch and A. Leo, Substituent Constants for Correlation Analysis, in Chemistry and Biology, Wiley, New York (1979); and C. Hansch, P. Maloney, T. Fujita, and R. Muir, Nature, 1962, 194, pages 178-180.

In the context of the present document, the Hansch parameters for the monomers are generally calculated with the "KOWWIN v1.68” (September 2010) software which is made available to the public by the US Environmental Protection Agency (EPA) as "Estimation Programs Interface Suite™ for Microsoft® Windows, v4.11” [2012], United States Environmental Protection Agency, Washington, DC, USA. This program ascertained the Hansch parameters for the monomers A1 and A2 and monomers B1 and B2 that were among those used in this document. Since the polymers 1 and 2 used or their aqueous polymer advantageously have a pH in the neutral to slightly alkaline range, complete deprotonation was assumed for the monomers containing acid groups, and so the calculation was made with the salt specified in each case.

Monomer Calculated individual Hansch parameter

Phosphoethyl methacrylate (as disodium salt, estimation) -5.6

Itaconic acid (as disodium itaconate) -5.6

Maleic acid (as disodium maleate) -5.21

Vinylsulfonic acid (as sodium vinylsulfonate) -4.17

Acrylic acid (as ammonium acrylate) -2.43

Methacrylic acid (as ammonium methacrylate) -1 .89

Vinyltrimethoxysilane -0.31

Hydroxyethyl acrylate -0.25

Acrylonitrile 0.21

Acetoacetoxyethyl methacrylate 0.24

Tetraethylene glycol diacrylate 0.29

Hydroxyethyl methacrylate 0.3

Ureidomethacrylate 0.41

Vinyl acetate 0.73

Methyl acrylate 0.73

3-Methacryloyloxypropyltrimethoxysilane 0.75

Vinyltriethoxysilane 1.16

Ethyl acrylate 1.22

Ethylene 1.27

Methyl methacrylate 1.28

Butanediol diacrylate 2.1

Allyl methacrylate 2.12

Isobutyl acrylate 2.13 n-Butyl acrylate 2.2

Isobutyl methacrylate 2.67

Butyl methacrylate 2.75

Styrene 2.89

Hexanediol diacrylate 3.08

Alpha-Methylstyrene 3.44

2-Ethylhexyl acrylate 4.09

2-Ethylhexyl methacrylate 4.64

Isobornyl methacrylate 4.76

Lauryl acrylate 6.13

Lauryl methacrylate 6.68

Stearyl acrylate 9.62 The Hansch parameters are calculated for the polymers P formed from the monomers M generally by the following general formula:

HPp = X1 ■ HPM1 + X2 ■ HPM2 + .... Xn ■ HPlvln with

HPp: calculated Hansch parameter of the polymer P formed from the monomers M1 , M2 ... Mn xi, X2, x_n: proportions by weight of the monomers M1 , M2 .... Mn incorporated into the polymer P in percent divided by 100, where the sum total of xi + X2 + . x_n = 1

HPMI, HP_M2, HPivm: the individual Hansch parameters calculated for each of the monomers M1, M2 .... Mn.

The Hansch parameter for a polymer formed, for example, from 40% by weight of methylmethacrylate (MMA) and 60% by weight of ethyl acrylate (EA) is therefore calculated as follows:

HPP = XMMA ■ HPMMA + XEA ■ HPEA

HPP = 0.4 ■ (1.28) + 0.6 ■ 1.22 = 1.24

In case the acrylate resin is formed by by stepwise polymerization with different monomer compositions the different polymers are taken as one monomer composition for calculating the Hansch parameter.

Useful monomers A1 include acid-functional monomer preferably all a, p-monoethylenically unsaturated C3- to Ce-, preferably C3- or C4-mono- or dicarboxylic acids. The invention shall likewise encompass the fully or partly neutralized water-soluble salts, especially the alkali metal or ammonium salts, of the aforementioned carboxylic acids. Examples include acrylic acid, methacrylic acid, ethylacrylic acid, itaconic acid, allylacetic acid, crotonic acid, vinylacetic acid, fumaric acid, maleic acid, 2-methylmaleic acid, but also monoesters of ethylenically unsaturated dicarboxylic acids, such as monoalkyl maleates of Ci to Cs alcohols, and the ammonium, sodium or potassium salts of the aforementioned acids. Monomer A1 is preferably selected from the group comprising acrylic acid, methacrylic acid, crotonic acid, fumaric acid, maleic acid, maleic anhydride, 2-methylmaleic acid and itaconic acid. According to the invention, however, acrylic acid and/or methacrylic acid are used particularly advantageously as monomers A1.

Useful monomers A2 include all nonionic ethylenically unsaturated monomers and are copolymerizable therewith. Examples of useful monomers A2 include, esters derived from vinyl alcohol and from monocarboxylic acids having 1 to 18 carbon atoms, preferably 2 to 10 carbon atoms, for example vinyl acetate, vinyl propionate, , Ci- to C32-alkyl vinyl ethers, such as methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, , esters derived from a,|3-monoethyleni- cally unsaturated mono- and dicarboxylic acids having preferably from 3 to 6 carbon atoms, particular examples being acrylic acid, methacrylic acid, maleic acid, fumaric acid and itaconic acid, with alkanols generally having 1 to 6, preferably 1 to 4 and especially 1 to 3 carbon atoms, particular examples being the methyl, ethyl, propyl, esters of acrylic acid and of methacrylic acid, the dimethyl esters of fumaric acid and of maleic acid, nitriles of a,|3-monoeth- ylenically unsaturated carboxylic acids, for example acrylonitrile, methacrylonitrile, fumaronitrile, maleonitrile, and also C4-8 conjugated dienes, such as 1 ,3-butadiene (butadiene) and isoprene. An useful monomer is also ethylene. The aforementioned monomers form generally > 50% by weight, preferably > 60% by weight and especially preferably > 80% by weight of the total amount of all monomers A1, A2 and A3, and thus constitute the main monomers A2. Preferably in accordance with the invention, polymer A comprises, as main monomer A2, an ester of acrylic acid or methacrylic acid with a Ci to C12 alcohol, especially methyl acrylate, ethyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate or methyl methacrylate, a vinylaromatic compound, especially styrene or o-methylstyrene, a nitrile of an a,|3-mo- noethy lenical ly unsaturated carboxylic acid, especially acrylonitrile, and/or a vinyl ester of a C2 to C12 monocarboxylic acid in copolymerized form.

Further useful monomers A2, to a minor degree, are those ethy lenical ly unsaturated monomers which comprise either at least one sulfo group and/or the corresponding anion thereof or at least one amino, amido, ureido or N-hetero- cyclic group and/or the nitrogen-protonated or alkylated ammonium derivatives thereof. Examples include acrylamide and methacrylamide; and also vinylsulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, styrenesulfonic acid, and water-soluble salts thereof, and also N-vinylpyrrolidone, 2-vinylpyridine, 4-vinylpyridine, 2-vinylimidazole, 2-(N, N- dimethylamino)ethyl acrylate, 2-(N, N-dimethylamino)ethyl methacrylate, 2-(N,N-diethylamino)ethyl acrylate, 2-(N,N- diethylamino)ethyl methacrylate, 2-(N-tert-butylamino)ethyl methacrylate, N-(3-N',N'-dimethylaminopropyl)methac- rylamide, and 2-(1 -imidazolin-2-onyl)ethyl methacrylate. The aforementioned monomers A2 are used generally in amounts of < 10% by weight, preferably < 5% by weight and especially < 1 % by weight, based in each case on the total amount of monomers A2.

Further monomers A2 usable in accordance with the invention are functionalized ethy lenically unsaturated compounds selected from the group comprising acetoacetoxyethyl acrylate, acetoacetoxypropyl acrylate, acetoacetoxybutyl acrylate, acetoacetoxyethyl methacrylate, acetoacetoxypropyl methacrylate, acetoacetoxybutyl methacrylate, diacetoneacrylamide and diacetonemethacrylamide. The aforementioned monomers A2 are used generally in amounts of < 15% by weight, preferably < 10% by weight and especially < 5% by weight, based in each case on the total amount of monomers A1, A2 and A3.

Monomers A2 which typically increase the integrity of the films formed by a polymer matrix normally have at least one epoxy group, at least one carbonyl group, or at least two nonconjugated ethylenically unsaturated double bonds. Examples of these are monomers having two vinyl moieties, monomers having two vinylidene moieties, and also monomers having two alkenyl moieties. Particularly advantageous monomers here are the diesters of dihydric alcohols with a, p-monoethylenically unsaturated monocarboxylic acids, and among these preference is given to acrylic and methacrylic acid. Examples of monomers of this type having two non-conjugated ethylenically unsaturated double bonds are alkylene glycol diacrylates and alkylene glycol dimethacrylates, for example ethylene glycol diacrylate, propylene 1 ,2-glycol diacrylate, propylene 1 ,3-glycol diacrylate, butylene 1 ,3-glycol diacrylate, butylene 1,4-gly- col diacrylate, hexane-1 ,6-diol diacrylate and ethylene glycol dimethacrylate, propylene 1 ,2-glycol dimethacrylate, propylene 1,3-glycol dimethacrylate, butylene glycol 1 ,3-dimethacrylate, butylene glycol 1,4-dimethacrylate, hexane- 1 ,6-diol dimethacrylate, and also divinylbenzene, vinyl methacrylate, vinyl acrylate, allyl methacrylate, allyl acrylate, diallyl maleate, diallyl fumarate, methylenebisacrylamide, cyclopentadienyl acrylate, triallyl cyanurate, and triallyl iso- cyanurate. The aforementioned monomers A2 are used generally in amounts of < 5% by weight, preferably < 3% by weight and especially preferably < 2,5% by weight, based in each case on the total amount of monomers A1, A2, A3.

However, monomers A2 used with preference are selected from the group consisting of vinyl acetate, ethylene, ethyl acrylate, methyl acrylate, methyl methacrylate,

Useful monomers A3 include nonionic ethy lenical ly unsaturated monomers and are copolymerizable therewith. Examples of A3 include vinylaromatic compounds such as styrene, o-methylstyrene, o-chlorostyrene or vinyltoluenes, vinyl halides such as vinyl chloride or vinylidene chloride, esters derived from a, p-monoethy lenically unsaturated mono- and dicarboxylic acids having preferably from 6 to 12 carbon atoms, particular examples being acrylic acid, methacrylic acid, maleic acid, fumaric acid and itaconic acid, with alkanols generally having 4 to 16, preferably 4 to 12 and especially 4 to 10 carbon atoms, particular examples being the, n-butyl, isobutyl, n-butyl, isobutyl, .pentyl, hexyl, heptyl, octyl, nonyl, decyl and 2-ethy lhexy I esters of acrylic acid and of methacrylic acid or di-n-butyl esters of fumaric acid and of maleic acid,

Advantageously, the at least one polymer A therefore comprises, in copolymerized form, acrylic acid and/or methacrylic acid as monomers A1, and vinyl acetate, ethylene, ethyl acrylate, methyl acrylate, methyl methacrylate as monomer A2, and styrene, n-butyl acrylate, n-butyl methacrylate and/or 2-ethy lhexy I acrylate as monomers A3.

Preferably the acrylic resin is obtained by free radical aqueous emulsion polymerization of a mixture comprising eth- y lenically unsaturated monomers A, wherein the monomer mixture comprises:

0.1 to < 5 % by weight, based on the total amount of monomers A, of at least one acid-functional monomer, as a monomer A1, preferably acrylic acid and/or methacrylic acid and

95 to 99.9 % by weight, based on the total amount of monomers A2 and A3, of at least one nonionic monomer, as a monomer A2, preferably whereas at least 50 % by weight of the monomer A2 is selected from the group consisting of vinyl acetate, ethylene, ethyl acrylate, methyl acrylate, methyl methacrylate, and up to 40% styrene, n-butyl- , i-butyl acrylate, n-butyl, - i-butyl methacrylate and 2-ethylhexyl acrylate, and other monomers A2. According to one preferred embodiment the acrylic resin is obtained by free radical aqueous emulsion polymerization of a mixture comprising ethy lenical ly unsaturated monomers A, wherein the monomer mixture comprises:

0.1 to < 5 % by weight, based on the total amount of monomers A of a monomer A1 which is acrylic acid and/or methacrylic acid and

95 to 99.9 % by weight, based on the total amount of monomers A, of at least one nonionic monomer, as a monomer A2, whereas at least 50% % by weight of the monomer A2 is selected from the group consisting of ethyl acrylate, methyl acrylate and methyl methacrylate, especially preferred ethyl acrylate, and up to 40 % by weight of monomer A2 are other monomers A2 and up to 10% are monomers A3

The conduct of free-radical ly initiated emulsion polymerizations of ethy lenical ly unsaturated compounds (monomers) in an aqueous medium has already been widely described and is therefore well known to the person skilled in the art [in this regard see Emulsionspolymerisation [Emulsion Polymerization] in Encyclopedia of Polymer Science and Engineering, volume 8, pages 659 ff. (1987); D.C. Blackley, in High Polymer Latices, volume 1 , pages 35 ff. (1966); H. W arson, The Applications of Synthetic Resin Emulsions, chapter 5, pages 246 ff. (1972); D. Diederich, Chemie in unserer Zeit 24, pages 135 to 142 (1990); Emulsion Polymerisation, Interscience Publishers, New York (1965); DE- A-40 03 422 and Dispersionen synthetischer Hochpolymerer [Dispersions of Synthetic High Polymers], F. Hblscher, Springer-Verlag, Berlin (1969)]. The free-radically initiated aqueous emulsion polymerization is typically effected by dispersing the monomers, generally with inclusion of dispersing aids, such as emulsifiers and/or protective colloids, in aqueous medium and polymerizing them using at least one water-soluble free-radical polymerization initiator. Frequently, the residual contents of unconverted monomers in the aqueous polymer dispersions obtained are reduced using chemical and/or physical methods likewise known to a person skilled in the art [see for example EP-A 771328, DE-A 19624299, DE-A 19621027, DE-A 19741184, DE-A 19741187, DE-A 19805122, DE-A 19828183, DE-A 19839199, DE-A 19840586 and 19847115], the polymer solids content is adjusted to a desired value by diluting or concentrating, or further customary added substances, for example foam- or viscosity-modifying additives, are added to the aqueous polymer dispersion.

The preparation of the acrylic resin might be a multistage polymerization process, which means a sequential polymerization in two or more stages of two or more distinct and different monomer mixture is conducted. This is known in principle to those skilled in the art. Suitable preparation processes are therefore disclosed, for all examples in EP-A in examples 1 to 10 according to the invention of EP-A 574803, or all examples of EP-A 1732962. The at least one polymer A may therefore be in neat form (bulk) or be dissolved in a suitable solvent or dispersed in a suitable liquid medium. The aqueous acrylic resin dispersion obtained after the polymerization comprises polymer particles having a weightaverage particle diameter in the range of > 10 and < 800 nm, advantageously in the range of > 20 and < 400 nm and especially in the range of > 30 and < 150 nm.

Most preferably the acrylate resin of the coating consists of monomer units selected from acrylic acid, methacrylic acid and esters thereof and styrene.

Application to a substrate may be by any conventional method including brushing, dipping, flow coating, spraying, roller coating and pad coating.

The coating compositions used in the inventive process may also comprise further customary auxiliaries that are familiar to the person skilled in the art in terms of nature and amount, for example fillers, soluble dyes, optical brighteners, retention agents, wetting agents, film-forming auxiliaries, defoamers, preservatives, biocides, slime control agents, plasticizers, antiblocking agents, antistats, buffer substances, hydrophobizing agents, etc..

Fillers used are essentially inorganic materials having a lower refractive index compared to the pigments (white fillers, according to DIN 55943 and DIN 55945, have refractive index values < 1 .7). The pulverulent fillers are frequently naturally occurring minerals, for example calcite, chalk, dolomite, kaolin, talc, mica, diatomaceous earth, baryte, quartz or talc/chlorite assemblages, but also synthetically produced inorganic compounds, for example precipitated calcium carbonate, calcined kaolin or barium sulfate, and fumed silica. The filler used is preferably calcium carbonate in the form of crystalline calcite or of amorphous chalk.

With platelet-shaped fillers, the barrier effect can be increased. For example, materials such as mica, talc, and graphene oxide are commonly used as platelet-shaped fillers in various applications to enhance the barrier properties.

Optionally, the coating compositions may also comprise at least one organic solvent that preferably acts as a filmforming auxiliary. Useful examples for this purpose include aromatic hydrocarbons, such as solvent naphtha, benzene, toluene, xylene, or mixtures of aromatic hydrocarbons as sold, for example, as Solvesso® 100, 150 or 200, chlorobenzene, esters such as ethyl acetate, butyl acetate, methylglycol acetate, ethylglycol acetate, methoxypropyl acetate, 2,2,4-trimethylpentane-1 ,3-diol monoisobutyrate (Texanol® from Eastman), dipropylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, propylene glycol monomethyl ether acetate, ethers such as butylglycol, tetrahydrofuran, dioxane, ethylglycol ether, diethylene glycol monoethyl ether, diethylene glycol monomethyl ether, diethylene glycol mono-n-butyl ether, diethylene glycol mono-n-hexyl ether, diethylene glycol diethyl ether, diethylene glycol dimethyl ether, diethylene glycol di-n-butyl ether, diethylene glycol di-n-hexyl ether, ethylene glycol di-2-ethylhexyl ether, ethylene glycol di-n-butyl ether, ethylene glycol di-n-hexyl ether, ethylene glycol di-n-propyl ether, dipropylene glycol dimethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol mono-n-butyl ether, dipropylene glycol mono-n-propyl ether, dipropylene glycol mono-tert-butyl ether, dipropylene glycol di-tert-butyl ether, propylene glycol monoethyl ether, propylene glycol monomethyl ether, propylene glycol mono-n-propyl ether, propylene glycol monophenyl ether, propylene glycol mono-tert-butyl ether, propylene glycol diphenyl ether, propylene glycol mono-n-butyl ether, tripropylene glycol monomethyl ether and poly(allyl glycidyl ether), ketones such as acetone, methyl ethyl ketone, halogenated organic solvents such as methylene chloride or trichloromonofluoroethane or other organic solvents, for example benzyl alcohol, dibutyl phthalate, propylene glycol, tris(butoxyethyl) phosphate.

Film-forming auxiliaries are used especially in order to lower the minimum film-forming temperature of the emulsion polymers and hence to contribute to good film formation without pin-holes.

The coating composition may contain pigments. Preferably the coating composition comprises from 0.1 to 2.0 wt.-% defoaming agents, from 0.1 to 2.0 wt.-% wetting agents and 0.1 to 10wt.-% in total of further auxiliaries, such as mineral fillers or pigments, flame retardants, coalescing agents such as BDG or Texanol, based on the liquid coating composition.

A further subject of the present invention is a process for producing a polyamide particle foam molding as described above, which comprises forming a coating by applying an aqueous acrylate dispersion on the surface of a polyamide particle foam molding in an amount of more than 30 g/m², preferably in the range from 40 to 60 g/m² based solids after drying.

The coating once applied may be allowed to dry naturally at ambient temperature and more preferably at a temperature in the range of from 10 to 80 °C, mostly preferable between 25°C and 60°C.

In accordance with the invention, the process of coating the polyamide particle foam molding with the water-based coating compositions comprises the applying and drying of the coating composition. It is possible to apply the coating composition as one, two or more layers, preferably as one layer.

Preferably the process comprises the steps of a) welding pre-expanded polyamide foam particles in a mold by heating with steam, infrared or microwave radiation, b) applying an aqueous acrylate dispersion by dip, spray or curtain coating, and c) curing the aqueous acrylate coating at a temperature of more than 10°C, preferably in the range from 25°C and 60°C.

The aqueous acrylate coating may be prepared as described in WO 2021/151688 A2. Further benefits and advantages of the present invention

The polyamide particle foam molding of the present invention is particularly useful as a battery cell holder. The molding provides excellent insulation properties and resistance to oils and other chemicals commonly found in battery systems. The acrylate resin coating also improves the surface properties of the molding, making it more resistant to scratches and abrasions. Additionally, the molding can be produced with a high degree of precision, allowing for a perfect fit with battery cells.

Examples

Hereinafter, the present invention is described in more detail and specifically with reference to the Examples, which however are not intended to limit the present invention.

Raw Materials:

PA1 : Ultramid® Flex F 38, Copolyamide 6/6.36, BASF SE, density 1060-1090 kg/m3, relative Viscosity

(RV) 37-3.9, melting point 199°C,

PA2: Ultramid® B40, Polyamide 6, BASF SE, density 1120-1150 kg/m³, viscosity number (VN) 240-260 ml/g, melting point 220°C

CM: (carbon black masterbatch): Ultrabatch 420: polyamide 6 batch containing 30 wt.-% Special Black

4 /beads

Antioxidant sterically hindered phenolic antioxidants, Irganox® 1098 from BASF SE, N,N'-hexane-1,6-diylbis(3-(3,5-di-tert-butyl-4-hydroxyphenylpropionamide))

Test methods:

Calculation of Hansch parameter

The Hansch parameters were calculated from the US EPA Kowwin software as described in US 2013/0053499 or may be calculated using a group contribution method as disclosed in Hansch and Fujita, J. Amer. Chem. Soc., 86, 1616-1626 (1964); H. Kubinyi, Methods and Principles of Medicinal Chemistry, Volume 1 , R. Mannhold et al., Eds., VCH, Weinheim (1993); C. Hansch and A. Leo, Substituent Constants for Correlation Analysis in Chemistry and Biology, Wiley, New York (1979); and C. Hansch, P. Maloney, T. Fujita, and R. Muir, Nature, 194. 178-180 (1962). Closed cell ratio (Volume fraction of closed cells and cell walls, ipr )

The Volume fraction of closed cells and cell walls so called closed cell ratio ipr was determined via DIN EN ISO 4590_Process 2b. The measurement device that was used Accupyc 1330 is produced from micromeritics. The closed cell ratio i r was calculated via following equation where cor the Volume fraction of open cells was. cor had to be calculated via equation 2. Vg corresponds to the sample volume. The sample volume was measured via the geometrical sample data (3). The rough sample size was 30*30*25 mm. VI corresponds to the sample volume of the specimen into which no air enters under test conditions and from which no gas can escape. VI was be measured via the measurement tool Accupyc 1330. i r = 100 - cor (1) cor = [(Vg - VI )/Vg] x 100 (2)

Vg = 2 x [(A1 + A2)/2 x (B1 + B2)/2 x (C1 + C2)/2]

Oil uptake

To evaluate the oil up take (O) the test parts were stored for 500 h and 80°C storage temperature in a test fluid. As test fluid isoparafine with a low viscosity was chosen (Isopar M from Exxon Mobil.

The test parts weighted after cooling down phase and soft daping of the sample to remove oil on the sample surface. The sample weight before the first contact (mO) with the car processing oil and the weight (ml) after 500h contact time were put in relation as follow:

O [%] = (m1-m0)/m0*100

Preparation of expanded polyamide foam particles (EPA)

Expanded Polyamide beads were produced on a ZE40 extruder with under water granulation (UWG): throughput 60 kg/h; extruder: 170 rpm; MT270°C; temperature die plate: 290°C, pressure melt pump before UWG: 230 bar; UWG: water temp. 65-68°C, 3700 rpm; die plate 35hole, diameter 0.85 mm, water pressure of the underwater pelletizer was adjusted between 1 - 4 bar. The below listed listed amounts of solid components were dosed into the feeding zone of the extruder:

50.0 w% PA 1 : Ultramid® Flex F 38, Copolyamide 6/6.36, BASF SE, density 1060-1090 kg/m3, relative Viscosity (RV) 3.7-3.9, melting point 199°C,

46.7 w% PA2: Ultramid® B40, Polyamide 6, BASF SE, density 1120-1150 kg/m3, viscosity number (VN) 240-260 ml/g, melting point 220°C 3% w% CM: (carbon black masterbatch): Ultrabatch 420: 70% ULT.B27 (10588306), 30% Special Black 4 geperlt/beads (10756078)

0.3 w% antioxidant: Irganox 1098 from BASF SE

The Blowing agent (nitrogen, N2) was directly dosed into the polymer melt. The obtained expanded polyamide beads (EPA) are spherical with a diameter between 0.8-1 .2 mm and have an initial bulk density of 300 - 400 g/l.

Preparation of polyamide particle foam molding FM1

The expanded polyamide beads (EPA) were stored at least 24 h before processing. The processing of the expanded particles to a molded part, was carried out with a standard EPP chest molding machine (Erlenbach EHV-C PP 870 x 670) in a mold with the dimensions 200 x 300 x 25 mm. The beads were fused with cross and autoclave steam with steam pressure of 2-4 bar. The obtained molded parts had a part density from 420 g/l to 440 g/l and a closed cell ratio from 85 vol% to 95 vol%.

Preparation of polyamide particle foam molding FM2

The expanded polyamide beads (EPA) were processed as described for FM1 but the beads were pre-pressurized with compressed air with 3.5 bar for 24 h at room temperature prior to steam chest molding. The obtained molded parts had a part density from 420 g/l to 440 g/l and a closed cell ratio from 85 vol% to 95 vol%.

Preparation of aqueous coating formulations CF1 - CF8

For the aqueous coating formulations (CF1 - CF) listed in table 1, the following components were added in a lab dissolver under stirring @ lOOOrpm. After the addition was complete the mixture was stirred for further 10 minutes.

AC1 : Joncryl 9522; acrylic dispersion from BASF, MFFT approx.. 20°C , solid content approx. 45%, Hansch parameter 1,19

AC2: Joncryl BRC 9631 : self x-linking acrylic dispersion from BASF , MFFT approx. 30°C, solid content approx. 39,5% Hansch parameter!, 14

AC3: Joncryl 9532: self x-linking acrylic dispersion from BASF, Minimum film forming temperature (MFFT) approx. 48°C, solid content approx. 40%, Hansch parameter 1,75

AC4 Joncryl 8224: Styrolacrylat mit poylmeren „hydrophilem" Schutzkolloid acryl Hansch parameter 2,17

AC5 Joncryl 8331 : Styrolacrylat selbstvernetzend; Hantsch Parameter 2,54 PU1 : Joncryl U 4500: self x-linking aliphatic polyester PUD dispersion from BASF, MFFT 17°C, solid content approx. 36%

PU2: Luphen 3615: poylester PUD from BASF MFFT <5°C, solid content approx 40%,

BDG: Butyldigylkol, Diethylengly koi n butylether from BASF

A1 Texanol , 2,2,4-Trimethyl-1 ,3-pentandiolmonoisobutyrat from Eastman Chemical (

A2 Foamstar SI 2292 , silicone based defoamer from BASF, solid content 9%

A3 Hydropalat WE 3221 , silicone based substrate wetting agent from BASF 45% solid content water: demineralized water

Tablel : composition (in w%) of aqueous coating formulations CF1 - CF6

Examples E1 - E6 and Comparative Examples C3 and C4

Coating of polyamide particle foam moldings

The polyamide particle foam moldings were dried for 8 h at 80°C (air) and then specimens with a dimension 57x30x25mm were prepared via cutting with a saw.

The specimens were immersed to the half-height of the specimen in the aqueous dispersion (CF 1-5) for 5 minutes at room temperature, dried for 5 min at 70°C, and then the procedure was repeated for the other non-immersed half of the specimen. Afterwards a second coating layer was applied by following the above-described procedure with the difference that the drying was caried out for 10 minutes at 50°C. The twofold coated samples were at least stored for 96 h at room temperature before further testing was carried out. The coating was 50 g/m² based on solids and had a layer thickness of 50 pm.

Comparative Examples C1 and C2 were not coated.

The test results of the Examples E1 - E6 and comparative Examples C1 - C4 are listed in table 2.

Table 2: Oil uptake of Examples E1 - E4 and Comparative Examples C1 - 04

The oil uptake of a standard specimen without coating is 19 % (01) and caused by the porous surface of the particle foam (interspace between fused particles): Via optimized processing conditions like pre-pressurizing of the beads prior steam chest molding the oil uptake could be slightly reduced to 13 w% (02). Specimens which are coated with the acrylate-based dispersions CF1- CF4 and especially CF2, CF7 and CF8 show a significant reduced oil uptake of 0-6 w% (E1 - E6). On the other specimens which were treated with the aliphatic polyester PU based formulation CF5 and CF6 did not show such significant decrease in oil uptake.

Claims

1 . A polyamide particle foam molding with a coating on at least part of the surface, wherein the coating comprises an acrylate resin.

2. The polyamide particle foam molding according to claim 1, wherein the acrylate resin of the coating has a Hansch parameter less than 3.

3. The polyamide particle foam molding according to claim 1 or 2, wherein the coating consists of an acrylate resin and is covering the whole surface of the polyamide particle foam molding.

4. The polyamide particle foam molding according to any of claims 1 to 3, wherein the coating has a thickness in the ranger from 40 to 60 m.

5. The polyamide particle foam molding according to any of claims 1 to 4, wherein the acrylate resin of the coating consists of monomer units selected from acrylic acid, methacrylic acid and esters thereof, styrene, vinyl acetate, acrylonitrile.

6. The polyamide particle foam molding according to any of claims 1 to 5, wherein the oil uptake is less than 12 wt.-% after storage of 500 h at 80°C in isoparaffinic hydrocarbon fluid.

7. The polyamide particle foam molding according to any of claims 1 to 6, wherein the polyamide is selected from the group consisting of polycaprolatam (PA6), polylaurolactam (PA 12, polyhexamethylene adipamide (PA 6.6), poly-hexamethylene sebacamide (PA 6.10), polyhexamethylene dodecanamide (PA 6.12), PA 6/66, PA 66/6, PA 6I/6T and copolyamide PA6/6.36 or mixtures therefrom.

8. The polyamide particle foam molding according to any of claims 1 to 7, where the polyamide particle foam molding is free of the acrylate resin.

9. The polyamide particle foam molding according to any of claims 1 to 8, where the coating is free of the polyamide.

10. The polyamide particle foam molding according to any of claims 1 to 9, where the coating and the polyamide particle foam are different materials.

11. A process for producing a polyamide particle foam molding according to any of claims 1 to 10, which comprises forming a coating by applying an aqueous acrylate dispersion on the surface of a polyamide particle foam molding in an amount of more than 40 to 60 g/m².

12. The process according to claim 11, comprising the steps of a) welding pre-expanded polyamide foam particles in a mold by heating with steam, infrared or microwave radiation, b) applying an aqueous acrylate dispersion by dip, spray or curtain coating, and c) curing the aqueous acrylate coating at a temperature of more than 40°C.

13. Use of the polyamide particle foam molding the according to any of claims 1 to 10 as batterie cell holder.