Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Patent
1998-07-09
2000-08-22
Wu, David W.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
524500, 428402, C08F 800, C08J 5702, B32B 516
Patent
active
061074128
DESCRIPTION:
BRIEF SUMMARY
CROSS-REFERENCE TO RELATED APPLICATIONS
This is the national stage of International Application No. PCT/BE96/00091 filed Aug. 28, 1996.
SUBJECT OF THE INVENTION
The present invention relates to a process for the preparation of ionomers in powder form.
The invention covers the use of ionomers in powder form obtained by this process for the protection of floor coverings or wall coverings.
TECHNOLOGICAL BACKGROUND
Floor coverings or wall covering are made essentially based on vinyl chloride homopolymers or copolymers. In addition to its physical and mechanical properties, the use of PVC is advantageous on account of its ease and diversity of use, especially by:
The inclusion of a swelling agent in the formulations allows foams to be obtained. These can be inhibited by localized printing to obtain relief effects.
However, for reasons associated with environmental protection, studies are currently under way in an attempt to replace PVC by polymers containing neither chlorine nor nitrogen.
Patents DE-3,903,670 C1 and DE-3,903,669 C1 describe the manufacture of floor coverings or wall coverings from PMMA, which is plasticized, by calendering or coating with plastisols.
These products contain a high level of plasticizers and can thus have drawbacks resulting from their migration and their volatility. Furthermore, acrylic compounds are relatively expensive polymers.
Patent application BE-09300955 describes the manufacture of a floor covering on EVA foam by calendering or extrusion and coated with a sheet of a so-called ionomeric compound, extruded as a wear layer. As a result of its excellent properties (transparency, resistance to abrasion, to scratching and to marking), this type of wear layer is considered to be particularly advantageous.
The manufacture of ionomers is itself described in the document "Ionic Polymers", Encyclopedia of Polymer Science and Engineering, Wiley-Interscience, Volume 8 (1987), pp. 393-423.
An ionomer is generally produced in two steps: the manufacture of a precursor, followed by its neutralization with a metal salt.
In order to obtain the precursor, ionic polymers are usually prepared by copolymerization of a functionalized monomer and of an olefinic monomer or by direct functionalization of a pre-existing polymer. Typically, the presence of a carboxyl group is obtained by copolymerization of acrylic acid or methacrylic acid with ethylene, styrene or other monomers. The resulting copolymer contains free acid functions which can be neutralized to the desired degree with metal hydroxides, metal acetates or salts.
The second step consists in neutralizing the said groups. Several routes can be used.
In the reaction in solution, this involves dissolving the copolymer, neutralizing in solution, precipitating it, washing it and finally drying it. The ionomer obtained is then stored with a desiccant to avoid any uptake of moisture.
This method of production is described in the literature, for example: "Ionomers: the sodium salt of Poly(ethylene-co-Methacrylic Acid)", Keling Han and H. Leverne Williams, Journal of Applied Polymer Science, Vol. 38, pp. 73-86 (1989), and U.S. Pat. No. 5,003,012.
The reaction for extrusion-neutralization is carried out in the extrusion die during melting of the products. The temperatures reached in the die are from about 180.degree. C. to 260.degree. C., and sometimes even higher. The sources of cations which can be used are especially Na.sub.2 CO.sub.3, K.sub.2 CO.sub.3, Mg(OH).sub.2, ZnO and Cu(CH.sub.3 COO).sub.2.
During this reaction, volatile products are eliminated in a degassing chamber on the die. This degassing step is very intricate since, with ionomer precursors with a high fluidity index, it is the product which escapes. This technique thus limits the manufacture of ionomer from precursors having an excessively high melt index.
Furthermore, this technique gives rise to contact between melting material and metal surfaces. On account of their chemical composition (presence of acidic sites), these products are corrosive, and it is necessary to work
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Roussel Albert
Siche Alexandre
Tarkett Sommer S.A.
Wu David W.
Zalukaena Tanya
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