DE2012433A1 - Heat-curable, powder-shaped. Plastic coatings - Google Patents

Description

INVENTA Aß for research and patent exploitation Zurich,

Zurich, Switzerland

Heat-curable »powdery plastic coating agents

It is known ,, epoxy compounds, e i @ m © hr as ein® epoxy group in the molecule, in combination with: suitable hardeners, vorzugswel & e old latsate © character fillers and leveling agents, etc "," in h®t Ramteapemtiir bestandig © pulverförmlge To transfer materials that are suitable for coating a wide variety of substrates with the application methods customary for this purpose and that harden in the heat ⁵ b @ ± tung stone temperatures, after complete hardening, high heat resistance and very good electrical properties over a wide temperature range. Responsible for "this" behavior is the thermoplastic state during application. which after hardening changes to the thermoset state

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goes · Furthermore, the epoxy resin powder is characterized by its very good adhesive strength on a wide variety of materials . In comparison to the conventional thermoplastic coating materials, in particular the polyamides, the epoxy resin-based coverings have only limited elasticity and impact strength, which are inadequate for many applications. Polyamides, especially nylon 11 and 12, are excellent coating materials with high elasticity, impact strength, low water absorption and very good corrosion resistance, but they retain their thermoplastic character even after application and due to the limited adhesive strength, especially when exposed to wet conditions an additional bonding agent is required.

It has therefore been various attempts, the benefits of the epoxy resins with those of polyamides, for various applications to combine * So vmrde sB _{a is} the adhesive strength of powdery Überzugsisiitsln ans Car'bonamidgruppen containing plastics by 0i.np:'i addition of 2 to 20 wt. ~? S reacting in the melt nonorjoren odsr ol.lgo & eren compounds with amino-, epojcid-; Carhaa / JL - ... ~ dyä.r & Y.y ~ l ~? lA ^ rt-Ppto- ₁ FLTRI-l · - or Xsocyanatgruppsn v rO & a & v.r-:. u'ü ^^ ü '}. as a result, complete crosslinking is achieved xriru (cf. * DA ^ 1. ?? l 286), the modification of ifporzidharzen with i'olyamiden for the application of al><K'i'A * zv _t da on 4i «i4Ci lv> ge dl «shear and peel strength (BS, QoMOn ₁ J, AppX. Polymer Sei, B (3), 1287-95 (1964)) and the T ^ i''ha3tci \ at t5 ^ f ^ v. Temper? - 'xu "5n - is ^{improved (" Advances In Cryogenic Eng, i?} 7, 336-42 (1961)).

By Guellvercuniie vmrde "bewiei ^ si that the polyamides i;? Reacts It ate Eposldgr ^ d r ψραη epoxy resins, and one V ^ r ^ ef, clothes eirttritt C ^ l * ^Ti, S _ä Gordon," J Appl Polymer Sci. 8 (2) # 1287-9? (196 * -)) Since dl ^ V ^ ruetsuoss only at relatively high temperatures « especially in the USA patent: ^ 9β2 hSe

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any event occurs about 25O ⁰ C, ie It £ above the Sehmelspunktes the polyamide used, it has also sought appropriate Reaktionsbesc ^ öuniger ijnd use lower-melting copolyamides which reaches the cross-linking reaction at lower temperatures and accelerated · Suitable catalysts Phenolic resins, dicyandiamide, tertiary amines, aliphatic polyamines or other basic compounds, as well as BF ^ amine complexes are suggested. A copolyamide of the nylon 6 / 6,6 / 6,10 type has been described, for example, but the copolyamides previously used for use as adhesive components have the disadvantage of high water absorption (up to 20% by weight ~ 56) <»Also as cured adhesives, they are sensitive to moisture (cf. A. Matting and W. - Brockmann, Angew, Chemie 80, 1968, Wr. 16, p. 646, line 18-0LO from below, left column. ", Switzerland. Patent 456 819 and W. Laskawskl et al., "Polymery * 11 (6), 261-265 (1966)," Product information "About Elvamide ™ 8061 from Du Pont de Nemours, CA.66, Il475bc).

It has now been found that heat-curable, powdery plastic coating agents can be produced by reacting epoxy compounds containing more than one epoxy group in the molecule with copolyamides in the presence of catalysts by using a teraäres copolyamide consisting of the randomly distributed structural units as the copolyamides des nylon 6, nylon 6/6 and nylon _; 12, used.

Instead of uniform starting materials, can mixtures of these also be used, of course? _s this is preferred even in practice. Particularly suitable epoxy resins for the coating compositions according to the invention are those compounds which are solid at room temperature. Per preferred range of the epoxy resins is between 60 and 135 ⁰ C

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phenols with epihalohydrins in the presence of alkalis. It is also possible to use GIyeldester, which are produced by reacting polycarboxylic acids with epihalohydrins and subsequent dehydrohalogenation, as well as reaction products of epoxy compounds which are liquid at room temperature with suitable dl- or polyfunctional ones Compounds such as amines, polycarboxylic acids, etc., between. 60 and 135 ° C, however, can still be melted.

The ternary copolyamides suitable for the mixtures according to the invention preferably consist of a copolymer composed of structural units of 10-60% by weight nylon 6, 10-50% by weight nylon 6/6 and 10-70% by weight nylon 12 composed, with the units of these types of nylon being randomly distributed. The percentages relate to the total weight of the ternary copolyamide. The melting temperature of these copolyamides is advantageously between 100 and 150 ⁰ C, and the water absorption under standard conditions (20 ° C and 65% relative humidity) is depending on the composition of the copolyamides between 0.5 and 3.0 wt .-%. The relative viscosity of the suitable copolyamides, measured as a 0.5 - # solution (wt .-? $) In m-cresol at 20 ⁰ C, is 1.3 to 1.6.

Particularly suitable catalysts are dicyandiamide, as well as certain inorganic or organic alkaline compounds, such as sodium phenolate, carbonate, bicarbonate and acetate, and the analogous potassium compounds in proportions of 0.3-3.0% by weight, based on the epoxy resin content, or Lewis acids, such as boron fluoride. The mixtures can also contain pigments, dyes, fillers, leveling agents, thixotropic agents, etc.

The mixtures of the reactants can be prepared in a heatable Z-kneader, an extruder or another suitable one Device by fusing at a temperature above

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half of the melting temperature of the highest melting compo- ' nente, but below the crosslinking temperature, take place. This mixture is then cooled to room temperature and then pulverized to the desired grain size · These mixtures preferably contain 30-90% by weight of epoxy resin and 10 - * 70% by weight ternary copolyamide of the type nylon 6, 6/6 and 12, where the percentages relate to the total weight of the mixture

The application of the mixtures according to the invention can be carried out according to the methods customary for this purpose, such as the fluidized bed method, electrostatic coating, spraying and flocking methods, the Stafluid method, the cloud chamber method for coating pipes, etc., the flame spraying method, among others. The preheating temperature of the objects to be coated should be approximately 180 - be 250 ⁰ C. The curing takes place, the catalyst and js portion within 5-30 minutes between 150 to 200 ^e C. It thermoset coatings with excellent adhesion to various materials, and very good flexibility and impact resistance are obtained. Although the production and processing properties are largely the same as systems based on pure epoxy resins *, the coatings obtained from them have, in addition to the preferred properties of epoxy resin coatings, the excellent mechanical properties of polyamides, without the high preheating temperature and additional adhesion promoters required for polyamides. ^ -

The coatings obtained with the mixture according to the invention stand out, in contrast to the previously known epoxy resin / Polyamide mixtures, due to a significantly lower water absorption capacity and in the cured state by a significantly lower moisture sensitivity. The excellent Properties of the epoxy resins and the copolyamides are combined by means of the method according to the invention. The following Examples illustrate the invention.

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example 1

In a heated stirred vessel, 420 parts by weight of a solid at room temperature, epoxy resin, trade name Grilonit L 1202 (based on bisphenol A and epichlorohydrin) having an epoxy equivalent of 590 - ternary 710 at 150 ⁰ C with 210 parts by weight of copolyamide of nylon 6, 6/6 and 12 having a melting temperature of 120 - 130 ⁰ C and mixed a water absorption capacity of 1 part by weight JS with vigorous stirring until complete dissolution. The homogeneous mass is then cooled, roughly broken and mixed in a heated Z-kneader at approx. 120 ^° C. with 140 parts by weight of a 50% by weight titanium dioxide, rutile KB, 50% by weight liquid epoxy resin, epoxy equivalent 190 - 200, trade name GRILONIT G 3, containing pigment paste is kneaded until the pigment is evenly distributed. The pigment paste is rubbed off beforehand on a three-roller mill. Then 56 parts by weight of powdered dicyandiamide are incorporated at the same temperature and immediately cooled. The roughly crushed material is then pulverized to the desired grain size in a pin tooth mill. For application using the electrostatic coating process, the grain size must be a maximum of 100 / u and for the fluidized bed process approx. 70 - 300 / u. To produce coatings, ^{steel sheets heated to about 180 °} C. are immersed for about 3 seconds in a whirling bath made from the powder obtained and then cured ^{at 180 ° C. for 20 minutes.} About 200 to 250 / u thick coatings are obtained which are superior to similar coatings made of pure epoxy resins in terms of adhesive strength, flexibility and impact resistance. In the Erichsen deepening test in accordance with DIM 53156, a deepening of 10 mm is achieved.

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Example 2

As described in Example 1 in the same manner, at 150-160 ⁶ C a homogeneous mixture composed of 420 wt * parts by a solid at room temperature, epoxy resin based on bisphenol A and epichlorohydrin having an epoxide equivalent of 870 to 1000 (trade name GRlLONIT L 1204) and 210 parts by weight of a ternary copolyamides of nylon 6, 6/6 and 12.mit a melting temperature of 120 - 13O ⁰ C ₉ prepared. The brittle to room temperature after cooling material is coarsely crushed and, until d a pigment is uniformly dispersed in a heated Z-kneader at 120 ⁰ C with 140 parts by weight of a pigment paste, as described in Example 1, kneaded ,, &; Then 7 parts by weight of sodium phenolate are introduced at the same temperature and, after mixing, the mixture is immediately cooled to room temperature. A material is obtained which is brittle at room temperature and which can be ground to the desired grain fineness in a pin tooth mill or other suitable mill. By dipping at about 200 ⁹ C heated steel sheets in a whirlpool from the thus obtained powder and curing for 15 minutes at 180 ⁰ C coatings are obtained with layer thicknesses 200-550 / u depending on the immersion time, which is excellent in adhesive strength, flexibility, and Have impact strength. Coatings applied by the electrostatic coating process with powder with a grain size smaller than 100 / u showed similar properties at layer thicknesses of 70-100 / u.

Following the same procedure and under the same conditions, as already described in Examples 1 and 2, a Powder made from 420 parts by weight of an epoxy resin which is 3rd at room temperature and is based on bisphenol A and epichlorohydrin with an epoxy equivalent weight of 590-710, and 210 parts by weight a ternary copolyamide of nylon 6 * 6/6 and 12 with

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a melting temperature of 140 to 150 ° C and a water absorption capacity under standard climate of 3 wt .- ^ produced. 140 parts by weight of the pigment paste described in Examples 1 and 2 were used for pigmentation and 1% by weight of sodium acetate, based on the amount of epoxy resin, was used as the catalyst 180 ⁰ C excellent properties which are superior to the usual epoxy resin coatings in terms of adhesive strength, flexibility and impact strength. In the case of the Erichsen cupping test in accordance with DIN 93156, cupping of 10 mm was achieved in layer thicknesses of 300 λι.

Example 4

In the same way as described in Examples 1 and 2, a powder with the following composition manufactured:

420.0 parts by weight of epoxy resin based on bisphenol A and

Epichlorohydrin with an epoxide equivalent of 590 to 710

140.0 parts by weight of ternary copolyamide of nylon 6, 6/6 and 12 with

a melting temperature of 120-130 ⁰ C and a water absorption capacity of 1 part by weight JS

280.0 parts by weight pigment paste, consisting of 50 wt .- # epoxy resin,

Epoxy equivalent 190 to 200, and 50% by weight? » Titanium dioxide, rutile KB

10.5 parts by weight of sodium carbonate
7.0 parts by weight of Aerosll.

The coatings obtained from this powder showed after curing for 15 minutes at 180 ⁰ C similar characteristics as in the preceding examples.

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Example 5

Xn modification to Example 1 was made under the same conditions gen and using the same starting materials Powder with a weight ratio of epoxy resin to ternary Copolyamide of 1: 1 produced «Coatings produced with this powder showed properties similar to those in Example 1 described.

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Claims (6)

- ίο - Claims Iy Heat-curable, powdery plastic coating agents, obtained by copolymerization of epoxy compounds containing more than one epoxy group in the molecule ternary copolyamides, characterized in that the used Copolyamide a ternary copolyamide consisting of represent the randomly distributed structural units of nylon 6, nylon 6/6 and nylon 12. 2. Process for the production of in the V-farm curable, powdery Plastic coating agents by reacting epoxy compounds containing more than one epoxy group in the molecule with copolyamides in the presence of catalysts, characterized in that the copolyamides used are a ternary copolyamide, consisting of the randomly distributed structural units of nylon 6, nylon 6/6 and nylon 12, used 3. The method according to claim 2, characterized in that the ternary copolyamides used have melting temperatures of 110 to 150 ⁰ C and a water absorption capacity under standard climate (20 ⁰ C and 65 % relative humidity) of 0.5 to 5 Gev; .-% · 4. The method according to claim 2 and 3 »characterized in that the copolyamides used copolymers with a composition of 10« - 60 wt .- $ structural unit of nylon 6, 10-50 wt. ~% Structural units of nylon 6/6 and 10 - representing 70 wt. '% Struktureinheitan of nylon 12, based vrobei the percentages on the total weight of the ternary copolyamides. 009839/1574 5 «Method according to claim 2 bit 4, characterized in that mixing 30 - 90 wt -.% Epoxy resin and 10 - 70 Gqw .- S ternary copolyamide used. 6. The method according to claim 2 to 5, characterized in that that the reaction of the epoxy compounds with the copolyamides carried out in the presence of inorganic or organic basic substances or of Lewis acids as a catalyst will. 009839/157