Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Patent
1993-06-10
1994-01-18
Schofer, Joseph L.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
427299, 427322, 428409, 4284111, 428500, 525374, 528424, C08F 830, C08F 806
Patent
active
052800849
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a method for modifying the surfaces of polymeric materials. More specifically, the method is intended to increase the surface energy of polymer surfaces and therewith render hydrophobic polymeric materials hydrophilic.
An increase in the surface energy and hydrophilicity of synthetic resin surfaces and fiber surfaces comprising hydrophobic polymeric materials is a highly significant factor in the improvement of the properties of such materials with respect to gluing, adhesion, painting, dying, metallizing and printing.
Improvements in these properties have been decisive in meeting the expanding usage of polymeric materials in practical applications. Hitherto, the hydrophilicity of hydrophobic polymers has been increased by the following methods: flame and plasma treatment.
Known chemical oxidation methods may include the use of solutions of chromium oxides, permanganates and perchlorates in strong mineral acids. These chemical methods have resulted in a very marginal lowering of the contact angle used as a measurement of the surface energy of polymer surfaces. Furthermore, it is difficult to obtain reproduceable results on the contact angle when applying these methods. Most polymers have a low surface energy (19.1 mJM.sup.-2 in the case of polytetrafluoroethylene; 30 to 33 in the case of polyethylene, and 47. mjm.sup.-2 in the case of polyethylene terephthalate) which means that they exhibit a high contact angle at the air/water interface, in the order of 80.degree.-95.degree., and cannot therefore be wetted readily with water.
A further drawback with the earlier published treatment methods is that that treatment is not stable and that the contact angle returns to its original values during the storage or use of such treated materials. Consequently, the effect of the treatment disappears with time and cannot therefore be used beneficially in practical contexts.
The improvement achieved in the hydrophilicity of polymer surfaces by the oxidative treatment of these surfaces is mainly due to the occurrence of polar groups on the polymer surfaces, mainly carboxyl, hydroxyl and carbonyl groups. The physical-chemical methods recited under point 2 above will generally result in the formation of similar groups on the polymer surfaces, and the limited success of these methods is due to the same reasons, namely an insufficient increase in surface energy and poor stability with regard to time.
The grafting methods referred to in point 3 above include a large number of known methods which although resulting generally in stable hydrophilicity, are expensive because of the complicated process apparatus required and the considerable monomer and catalyst input entailed. An additional drawback with graft copolymerization methods resides in the difficulties experienced in removing the simultaneously forming homopolymers, and in the very long extraction times required herefor.
The object of the present invention is to provide a method which will increase the surface energy and hydrophilicity of polymer surfaces, which will result in permanent hydrophilicity, and which because of the short treatment times and low chemical consumption entailed is suitable for industrial applications.
Accordingly this invention consists in a method which is mainly characterized by subjecting to oxidation in a first step, polymeric materials which include polyolefins, polystyrene, fluoroplastics, polyesters, polyacetals and polyacrylates, such as to produce on the polymer surfaces functional groups such as carboxyl, hydroxyl and carbonyl groups with the aid of known methods chosen from etching with oxidizing acid solutions, corona-treatment, plasma treatment and flashing treatment, and said first step also including the selection of polymerisation conditions in the manufacture of the polymeric material such that said functional groups will be incorporated in the polymer chains, and by bringing the resultant polymer surface in a second step into liquid contact with organic compounds which include heterocyclic compo
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Dialog Information Services, File 351, World Patent Index 81-89, Dialog Accession No. 85-102044/17, Shinto Paint KK: "Coating of Polyolefin Resin Mouldings by Plasma-Treating, Applying Compsn Contg. Free Isocyanate-Contg. Opds and Exposing to Amine Vapour", JP 60047035, A, 850314, 8517 (Basic).
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PP Polymer AB
Schofer Joseph L.
Zitomer Fred
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