Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Treating polymer containing material or treating a solid...
Patent
1993-12-16
1995-08-15
Michl, Paul R.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Treating polymer containing material or treating a solid...
528322, 528480, 427306, 427307, 427322, 264129, 264340, C08J 300, C08F 800, B05D 310
Patent
active
054420423
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a process for the surface treatment of moldings based on polyamides by treatment with aqueous acids.
The present invention further relates to moldings obtainable by this process and to the use thereof for metallization, i.e. for coating with metals.
Polyamides are engineering plastics and have found wide utility in many areas.
However, an interesting area has hitherto been largely denied to polyamides--the field of metallized materials. The reason for this is mainly the inadequate adhesion of the metal layer on the polyamide. This matter is discussed in a paper by Seldenspinner (Galvanotechnik 75 (1984), 852), and various possible solutions are tentatively hinted at, for example treatment with aqueous hydrochloric acid. In Galvanotechnik 79 (1988), 54, a process is described for the surface treatment of polyamide injection moldings wherein activation in a bath containing palladium salts is followed by surface roughening in a bath containing calcium and aluminum salts. This process is commercially disadvantageous because of the expensive materials used, nor is the adhesion obtained fully satisfactory.
2. Review of Related Art
EP-A 56 986 discloses polyamide molding compositions which contain from 30 to 60% by weight of wollastonite as filler and are suitable in particular for metallization. The pretreatment is carried out with a from 4 to 15% strength solution of hydrochloric acid or sulfuric acid, which by attacking the filler particles produces a roughening of the surface; that is, the filler is absolutely necessary for obtaining good adhesion between metal and polyamide. However, the high filler content impairs the quality of the surface, which is a disadvantage for decorative purposes.
EP-A 402 750 discloses a process of surface treatment and subsequent metallization for polyamides. In this process partly aromatic copolyamides are treated with aqueous H.sub.3 PO.sub.4 and metallized. However, partly crystalline or amorphous polyamides which can be composed of aromatic monomer units cannot be satisfactorily metallized by this process. The adhesion obtained is not sufficient for some applications.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a process for the surface treatment of moldings based on polyamides that is free of the above-described disadvantages and gives moldings which are subsequently readily metallizable.
We have found that this object is achieved according to the invention by a process for surface treatment of moldings based on polyamides by treatment with aqueous acids, which comprises using a mixture of at least 20% strength by weight aqueous hydrochloric acid with a mono- or diether of an aliphatic polyfunctional hydroxy compound in a mixing ratio of from 90:10 to 10:90. The weight percentage is based on the HCl content at 20.degree. C., which should be at least 20% by weight, preferably at least 25% by weight and in particular at least 30% by weight.
DESCRIPTION OF PREFERRED EMBODIMENTS
The process of the invention is suitable for the surface treatment of moldings based on polyamides, i.e. moldings which contain a thermoplastic polyamide as an important constituent. The thermoplastic polyamide may have been modified with fillers, polymers which improve the impact toughness, other polymers or flame retardants.
Suitable polyamides are known per se and encompass the semicrystalline and amorphous resins having weight average molecular weights of at least 5,000 which are customarily referred to as nylons. Such polyamides are described for example in U.S. Pat. Nos. 2,071,250, 2,071,251, 2,130,523, 2,130,948, 2,241,322, 2,312,966, 2,512,606 and 3,393,210.
The polyamides can be prepared for example by condensation of equimolar amounts of a saturated or an aromatic dicarboxylic acid of from 4 to 12 carbon atoms with a diamine of from 4 to 14 carbon atoms, or by condensation of .omega.-aminocarboxylic acids or polyaddition of lactams. Examples of polyamides are polyhexame
REFERENCES:
patent: 3556882 (1971-01-01), Fishman et al.
patent: 5192477 (1993-03-01), Betz et al.
Probleme bei der Metallisierung von Polyamid, Seidenspinner Galvanofechnik, 75 (1984) Nr. 7.
Metallisierung von Polyamid-Spritzgussteilen, Galvanotechnik 79 (1988) Nr. 1, Wolf et al.
Betz Walter
McKee Graham E.
Zeiner Hartmut
BASF - Aktiengesellschaft
Hampton-Hightower P.
Michl Paul R.
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