Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...
Patent
1993-08-30
1995-08-08
Foelak, Morton
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Cellular products or processes of preparing a cellular...
521 79, 521146, 521147, 521149, C08J 902
Patent
active
054399467
DESCRIPTION:
BRIEF SUMMARY
This application is a 371 of PCT/NL92/0040 filed Feb. 27, 1992.
The invention relates to a process and an intermediate for preparing an intrinsically foamed thermoplastic polymer comprising a vinyl monomer and maleic acid and/or anhydride.
The invention also relates to a foam based on a thermoplastic polymer comprising a vinyl monomer and maleic acid and/or anhydride obtainable according to the process.
Such a process is known from the Japanese patent application JP-A-01170623. In that patent application a process is described for preparing a thermoplastic polymer foam using the intrinsic foaming characteristics of the polymer.
Thermoplastic polymers are generally foamed by means of a blowing agent. Blowing agents can be divided into physical and chemical blowing agents.
Physical blowing agents are inert volatile compounds such as chlorofluoromethanes, aliphatic hydrocarbons containing four to six carbon atoms and inorganic blowing agents such as CO.sub.2, H.sub.2 and air. They are added to the polymer to be foamed in the melt and expand in consequence of the high temperature. The polymer is foamed to the desired density.
Chemical blowing agents are compounds showing a chemical reaction under the conditions in the melt and in the process release a propellant which expands and causes the polymer melt to foam to the desired density. Examples hereof are organic carbonates delivering CO.sub.2 by heating.
The chemical blowing agents can be added to the polymer to be foamed in two ways. The chemical blowing agent is admixed to the polymer to be foamed, in which process the mixing can be effected before the melting or during the melting.
In the polymer to be foamed chemical blowing agents can, however, also be incorporated: during the polymerization of the polymer to be foamed the chemical blowing agent is incorporated as comonomer. Such polymers, with a chemical blowing agent forming an integral part of the polymer, are herein referred to as intrinsically expandable polymers. Chemical blowing agents forming an integral part of a polymer can be divided into additional chemical blowing agents and functional chemical blowing agents.
Additional chemical blowing agents are chemical blowing agents present in the intrinsically expandable polymer as an additional comonomer. Besides delivering a blowing agent, they do not affect the properties of the polymer itself.
Functional chemical blowing agents are chemical blowing agents forming a functional monomer of the intrinsically expandable polymer. Besides delivering a blowing agent, the functional chemical blowing agent is important for the characteristic properties of the polymer itself.
The process described in the Japanese patent application JP-A-01170623 relates to a thermoplastic polymer belonging to the intrinsically expandable polymers. The thermoplastic polymer contains units of a monoester of an ethylenically unsaturated dicarboxylic acid and a vinyl monomer.
During the heating of the thermoplastic polymer according to JP-A-01170623, the monoester decomposes to form the corresponding cyclic anhydride and an alcohol. The alcohol molecules released evaporate at the high temperature and thus function as propellant for the polymer. A limitation of the said preparation process is the temperature at which the foam is formed; this is 120.degree. C.-170.degree. C. The polymer expands just above its Tg.
For the preparation of, for instance, foam obtained from a polymer melt of polymers with a Tg above 120.degree. C. the said process is unsuitable, however. The propellant is formed then in too early a phase. The solubility of the propellant in the polymer melt is thought to be too low, so that the blowing agent might escape. Besides, the polymer may yet be in the form of a solid, so that the gas released may escape via the polymer feed opening.
The object of the invention is to provide a process for preparing a thermoplastic polymer foam comprising a vinyl monomer and maleic acid and/or maleic anhydride, the polymer to be foamed being intrinsically expandable with a Tg of
REFERENCES:
patent: 3547838 (1970-12-01), Moore et al.
patent: 4306036 (1981-12-01), Corbett
patent: 4307202 (1981-12-01), Corbett
patent: 4454086 (1984-06-01), Corbett et al.
patent: 4544682 (1985-10-01), Corbett et al.
Boyens Joseph P. H.
Geesink Johannes H.
Klumperman Lubertus
DSM N.V.
Foelak Morton
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