DE2224991A1 - Process for the pretreatment of the surface of plastics to improve the adhesive strength - Google Patents

Description

Patent attorneys

Dipl.-hg. P. Wirth

Dr. V. Srhrrisd-Kowarzik _;

Dipl. I ig. G. Dannenberg

Dr. P. Webnold, Dr. D. Gudel

6 Frankfurt / M., Gr. E »ch« nheim «r Str.39

S A N D 0 Z AG.

Basel / Switzerland Case A 109

Process for the pretreatment of the surface of plastics to improve the adhesive strength

The invention relates to a method for pretreating the surface of plastics from the group of polycondensation plastics, e.g. polyesters, polyamides and epoxy resins, also polystyrenes, polyacetals and the polyvinyl chlorides to improve the adhesive strength. The invention further relates to a layered body with at least one of the plastics mentioned at the outset Group, e.g. polyester based on terephthalic acid, consisting of a plastic layer of at least one surface

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is pretreated according to the inventive method and with at least one further layer consisting of metal, wood, glass, ceramic or plastic, the layers through at least one adhesive layer are connected. The invention also relates to metal-coated moldings made of plastics of the group mentioned at the outset, the ones to be coated Surface pretreated according to the method according to the invention have been.

The strength of known laminated bodies, which are glued together using plastic layers, leaves many left to be desired, as the adhesive connections do not withstand greater loads. Organic polymers often prepare Difficulties in gluing with the usual materials. This is especially true when bonding organic polymers with metals or inorganic substances, which mostly have a strongly polar character and a high specific surface energy with the aid of similar adhesives, e.g. epoxy resins, the case, since the organic polymers have a low specific surface energy. Attempts have been made to overcome these difficulties with polyethylene terephthalate e.g. by pretreatment with sulfuric acid, nitric acid, chromic sulfuric acid or caustic soda or by exposure to ozone, To overcome flame exposure or the like. Surface treatments.

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In the POS Mr. 1.25 ^ * 350 is "for example the pretreatment" of polyethylene glycol terephthalate foils with nitric and / or; Sulfuric acid to bitterness of the sealability. In the $ fOS Mr. 1. * 9 * .l} 6 describes the activation of the adhesive properties of the surfaces of polyether products by pretreatment with sodium dichromate and sulfuric acid. However, the strong reagents and harsh conditions used in these methods have an unfavorable influence on the material and cause degradation same.

The invention is based on the object of a method for Pre-treatment of the surface of polyesters ku create with whose help the adhesive strength, while avoiding the mentioned Disadvantages, can be improved. It's supposed to be one, using at least one plastic layer, glued-together laminated body are created »whose strength is improved.

The invention therefore relates to a method for pretreating the surface of plastics from the group of Polycondensation plastics, epoxy resins, polyacetals, Polystyrenes and polyvinyl chlorides to improve the adhesive strength, characterized in that the plastic

ORIGINAL INSPECTED

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Surface pretreated with an acidic permanganate solution will.

The plastics used are in particular those from the group of polycondensation plastics, e.g. polyesters, polyamides, polycarbonates and epoxy resins, as well as polyacetals, polystyrenes and polyvinyl chlorides.

The inventive method is particularly suitable for the pretreatment of surfaces to be bonded or metallized of thermoplastic polyesters made of terephthalic acid, Isophthalic acid, 2,6-naphthalenedicarboxylic acid, 4,4'-diphehyldicarboxylic acid or smaller amounts of aliphatic Dicarboxylic acid residues and ethylene glycol, 1,4-butanediol, • 1,4-bis (hydroxymethyl) -cyclohexane and / or 2,2'-bis- [p- (ßhydroxy-ethoxy) -phenylj-propane radicals.

A layer containing manganese oxide with a weight per unit area of 2-14 μ is advantageous on the plastic surface

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g / cm, preferably 4 - 10 μg / cm, manganese formed in the oxide.

The thin layer of manganese oxides apparently acts as an adhesion promoter and significantly improves the strength of the adhesive bond when applied to the pretreated surface of plastic e.g. polyester based on polyethylene

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terephthalate, an adhesive, e.g. an epoxy resin or a metal layer is applied directly. The immediate application a metal layer can be achieved by deposition of thin metal films, by chemical reduction of metal salt solutions or by vapor deposition of metals in a high vacuum. The most common method of making a conductive layer is the reduction silver plating. Also other metals e.g. copper and platinum can be deposited on plastic surfaces by reduction processes. Nickel can be obtained from hypophosphite baths deposited on plastic surfaces. At the High vacuum evaporation processes are the metals in one

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Evaporated to high vacuum containers at pressures of about 10 torr; The most common metal used is aluminum, as well Gold, silver, copper ,. Chromium, nickel and other metals can be vapor deposited. The metal coatings thus obtained can also as conductive layers for galvanic metal deposition to serve. The plastic parts provided with a conductive layer are attached to contact wires and act as cathodes switched, hung in the respective metal electrolytes. Usually the thin conductive layer is only strengthened in a weakly acidic copper bath. Anything can then be applied to this copper coating any metal can be deposited from the usual electroplating baths. Many metals, e.g. nickel, silver and gold but can also be deposited directly from special baths.

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10% - - sulfuric acid at 60 - Suitably the pretreated plastic surface in a solution of potassium permanganate # 2-6 in Figure 1 is 80 ° C immersed. But you can also work at temperatures between 20 and 100 ^0C. For example, a 2-6 $ solution of potassium permanganate is preferably used. 1 - 5 $ sulfuric acid is used. The workpieces are immersed in the sulfuric acid solution and then dried. It has proven to be beneficial to degrease and mechanically roughen the workpieces beforehand. The previous degreasing can also be replaced by an extension of the immersion time in the permanganate solution. The temperature of the permanganate solution should preferably be chosen between 60 and 80 ° C; At higher temperatures the deposition of the manganese oxides is somewhat faster, at lower temperatures somewhat more slowly. Depending on the size of the workpiece and the treatment conditions, the treatment times are between 5 seconds and 15 minutes. The process can also be carried out continuously.

The inventive method can be used to pretreat the to adhesive surfaces of injection molding, extrusion or molded bodies produced by other shaping processes made of plastics of the group mentioned above can be used. The pretreated surfaces can be

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layers of a suitable adhesive, e.g. based on Epoxy resins, isocyanates or vinyl acetate copolymers. with each other or with other materials, e.g. metals, Wood, glass or ceramics can be glued. It can also apply to the According to the invention pretreated plastic surfaces are directly applied a metal layer. A suitable one Process is e.g. the reduction silver plating. In this process, ammonia is added to a silver nitrate solution until the precipitate just dissolves. Then a reducing solution is poured in and the one to be silvered Shaped body briefly immersed.

The plastics pretreated by the process according to the invention can also contain pigments, stabilizers, plasticizers, Contain fillers, reinforcing substances, e.g. glass fiber and other common additives.

The laminated bodies produced according to the invention, in particular made of plastics from the group mentioned at the outset, and metals 'or wood are used, for example, as ski components. Metallized plastic moldings are used as capacitors, film resistors, Switching elements, pushbuttons, signs and reflector components are used. Decorative metal coatings can E.g. on pieces of jewelry, furniture fittings, bottle caps

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among others are applied.

Preferably, the metallic coatings consist of those according to the invention metallized plastic molded body made of at least one metal from the group aluminum, lead, chrome, gold, Copper, nickel, platinum, silver, zinc and tin and generally have a total thickness of up to 0.5 mm.

The following examples serve to explain the invention in more detail without restricting it.

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example 1

Polyethylene terephthalate injection-molded specimens measuring 180 15 x 4 mm were roughened on the surface, cleaned with a brush, degreased with saturated NapCO-solution, rinsed with water and dried with hot air. Then, the specimens were immersed in a 5 $ solution of potassium permanganate in 4 ^ sulfuric acid at 70 ⁰ C for a period of 2 minutes ·, the bath was stirred. The test specimens were then washed with water, dried with hot air and immediately bonded with an epoxy resin. The epoxy resin araldite was used as the adhesive. The surface to be bonded was coated with the adhesive and an aluminum foil pretreated by the sulfuric acid-sodium dichromate process was applied, 0.5 mm thick and 15 mm wide in accordance with DIN 53 28l. The test specimen was then pressed under a pressure of 10 kp / cm and at a temperature of 120 ^° C. for 15 minutes. At the same time, test specimens made from the same plastic but not treated with the potassium permanganate solution were bonded in the same way with the same adhesive. After storage for one hour at room temperature, the peel strength of both those treated with the potassium permanganate solution and the untreated test specimens were determined using the climbing drum peeling method based on the DTN draft

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53 289 of November 1967 and the results were compared, with 10 test specimens being tested in each case: The peel strengths of the pretreated test specimens were on average 20 % higher than those of the non-pretreated test specimens.

Example 2

A Polyathylenterephthalatplatte, 80 mm χ 120 mm χ J5> 5 mm in size, was C IQ minutes pretreated with a 5 $ strength potassium permanganate solution in 4 # sulfuric acid at 70 ^0th The plate was then washed with distilled water and dried. The pretreated plate was then silver-plated. (Regulation according to the manual of preparative inorganic chemistry by G. Brauer 2nd edition, volume 2, page 907) where the following procedure was used:

Production of the solutions required for silver plating

a) Silver solution: 5 g of AgNO were dissolved in 100 ml of distilled water solved. One third of this solution was set aside as a reserve solution. To the remaining two thirds of the Solution was concentrated dropwise with stirring from a burette. Ammonia added until the resulting deep brown

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Precipitation dissolved. Reserve solution was then added until the precipitate reappeared. By Further dropping of ammonia, the precipitate was redissolved. This procedure was repeated as long as until the reserve solution was used up. Then ■ was made up to 500 ml with distilled water.

b) Reduction solution: 0.9 6 Seignette salts were in 5 ml of water dissolved and poured into 500 ml of boiling hot water. A solution of 1.1 g of AgNO- in 5 ml Poured in water, gradually forming a green-gray precipitate. Thereafter, the solution was 5 minutes for Heated to boiling and filtered.

For silver plating, equal amounts of silver and reducing solution were mixed and the pretreated polyethylene terephthalate plate was hung in this mixture for 5 minutes, a thin layer of silver forming on the plate. Anschlies- "send the plate was rinsed with distilled water and plated with a new solution for another 20 minutes.

The resulting well-adhering, cohesive silver mirror was when a self-adhesive strip was torn off not detached from the polyethylene terephthalate surface.

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If, on the other hand, an untreated, However, degreased polyethylene terephthalate plate was silver-plated, so it came off when the self-adhesive strip was torn off the silver layer completely from the polyethylene terephthalate plate away.

Even in the cross-cut test according to DIN 5J5.151, No peeling of the silver layer was observed on the pretreated plates after the self-adhesive strip had been stuck on and torn off.

The applied to the pretreated polyethylene terephthalate plate contiguous silver mirror has very good electrical conductivity, which makes applying further Metal layers is made possible by conventional electrochemical processes.

Replace "polyethylene terephthalate" in the examples Polytetramethylene terephthalate, trioxane-ethylene oxide copolymer, 6,6-polyamide or the polycarbonate ester of 4,4'-dioxydiphenyl-2,2-propane similarly good results are achieved.

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Claims (8)

- 13 - Case A 109 PATENT CLAIMS 1. Process for the pretreatment of the surface of plastics from the group of polycondensation plastics, epoxy resins, of polyacetals, polystyrenes and polyvinyl chlorides to improve the adhesive strength, characterized in that that the plastic surface is pretreated with an acidic permanganate solution. 2. The method according to claim 1, characterized in that a layer containing manganese oxide with a weight per unit area of 2-14 μg / cm ² 'of manganese is formed in the oxide on the plastic surface, 3. The method according to claim 2, characterized in that the surface of the plastics in a 2-6 # solution of potassium permanganate in 1 to 10, preferably 1 to 5 i & ^ iger, sulfuric acid at 20 - 100 ⁰ C, preferably 60 - 80 ° C, is immersed. 4. Laminated body with at least one layer made of a plastic from the group of polycondensation plastics, epoxy resins, polyacetals, polystyrenes and polyvinyl chlorides, and with at least one further layer 209850/1108 - l4 - Case A 109 made of metal, glass or plastic, being the layers are connected by at least one adhesive layer, characterized in that the pretreated surface (s) (n) of the plastic layer (s) an adhesion-promoting, manganese oxide-containing coating with a surface 2 weight of 2 - 14 μg / cm, preferably 4 - 10 μg / cm, have manganese in the oxide. 5. plastic moldings from the group of polycondensation plastics, the epoxy resins, the polyacetals, polystyrenes and the polyvinyl chlorides, which form a Adhesive coating containing manganese oxide a basis weight from 2 to 14 μ g / cm, preferably 4 - 10 ^ g / cm, manganese in the oxide and at least having a metal layer daüberliegende. 6. The method according to any one of claims 1-5, characterized in that that the plastic is a thermoplastic, linear polyester or copolyester made from terephthalic acid, Isophthalic acid, 2,6-naphthalenedicarboxylic acid, 4,4'-diphenyldicarboxylic acid or smaller amounts of aliphatic dicarboxylic acid residues and ethylene glycol, 1,4-butanediol, 1,4-bis (hydroxymethyl) cyclohexane and / or 2,2'-BIs- [p- (ß-hydroxyethoxy) phenyl] -propane residues is used. 209850/1108 - 15 - Case A 109 7. Laminated body according to claim 4, characterized in that ■ that the plastic is a thermoplastic linear polyester or copolyester made from terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, 4,4'-diphenyldicarboxylic acid or smaller amounts of aliphatic dicarboxylic acid . residues and ethylene glycol, 1,4-butanediol, 1,4-bis (hydroxymethyl) cyclohexane and / or 2,2'-bis- \ p- (ß-hydroxyethoxy) phenyl] propane radicals are used. 8. Plastic molding according to claim 5 *, characterized in that that the plastic is a thermoplastic linear polyester or copolyester made from terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, 4,4'-diphenyldicarboxylic acid or smaller amounts of aliphatic dicarboxylic acid residues and ethylene glycol, 1,4-butanediol 1,4-bis (hydroxymethyl) cyclohexane and / or 2,2 ^ rBIs- [p- (β-hydroxyethoxy) phenyl] propane radicals is used. / Patent attorney id-Kowarzik) 209850/1108