Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...
Patent
1994-11-22
1995-09-26
Foelak, Morton
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Cellular products or processes of preparing a cellular...
521 81, 521 88, 521 97, 521910, 264DIG5, C08J 908, C08J 914
Patent
active
054534542
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a process for the production of foam boards of high compressive strength by extruding a mixture of styrene polymer, a blowing agent or blowing agent mixture and, if desired, conventional additives and/or auxiliaries.
A multiplicity of blowing agents has been proposed for the production of foam boards based on styrene polymers by extrusion.
For example, EP-A-464 581 discloses a process for the production of foam boards having high compressive strength and a cross-sectional area of at least 50 cm.sup.2, in which a mixture of styrene polymer, from 5 to 16% by weight, based on the styrene polymer, of a blowing agent, and, if desired, conventional additives is extruded, where the blowing agent used is a mixture comprising of from 56 to 100.degree. C., of a saturated C.sub.3 - to C.sub.5 -hydrocarbon and/or a hydrogen-containing chlorofluorocarbon or fluorocarbon having a boiling point of from -30.degree. C. to +30.degree. C.
The foam boards produced by known processes have the disadvantage that the final values, for example for heat distortion resistance, become established relatively slowly.
JP-A 60/145 835 discloses the production of a laminate board containing a polystyrene foam layer, in which the polystyrene foam layer has been produced by extrusion using an ether, such as dimethyl ether, methyl ethyl ether or methyl vinyl ether, as blowing agent.
The example describes the production of a board with a thickness of 6 mm using 3.7 parts by weight of dimethyl ether, based on polystyrene, as blowing agent.
It has also been disclosed that adequate dimensional stability and compressive strength of foam boards having a thickness of 20 mm or more, in particular of .gtoreq.50 mm, is frequently not guaranteed if blowing agents which diffuse rapidly out of the foam are used.
Furthermore, the use of blowing agents of high blowing force frequently gives foams having a high content of open cells.
Thus, in the process of EP-A-464 581, the production of high-quality foam boards having a thickness of 20 mm or more is frequently only possible in the presence of chlorofluorocarbons or fluorocarbons as blowing agent.
It is an object of the present invention to provide a process for the production of foam boards from styrene polymers having a minimum thickness of 20 mm, in which no toxic blowing agents are used and which gives foams containing closed cells which have only low water-absorption capacity and, in addition to good dimensional stability and compressive strength, have, in particular, high heat distortion resistance. It is a further object of the present invention to provide a process which enables the rapid establishment of the final values, in particular for heat distortion resistance, in the foam boards produced.
We have found that this object is achieved by a process for the production of foam boards having a minimum thickness of 20 mm and a cross-sectional area of at least 50 cm.sup.2 by extruding a mixture of a styrene polymer, from 1 to 10% by weight, based on the styrene polymer, of a blowing agent and, if desired, conventional additives and/or auxiliaries, in which the blowing agent used is at least one ether from the group consisting of dimethyl ether, methyl ethyl ether and methyl vinyl ether.
For the purposes of the present invention, styrene polymers are taken to mean polystyrene and copolymers of styrene containing at least 50% by weight of copolymerized styrene.
Examples of suitable comonomers are .alpha.-methylstyrene, ring-halogenated styrenes, ring-alkylated styrenes, acrylonitrile, esters of (meth)acrylic acid with alcohols having 1 to 8 carbon atoms, N-vinyl compounds, such as N-vinylcarbazole, maleic anhydride or alternatively small amounts of compounds containing two polymerizable double bonds, such as butadiene, divinylbenzene and butanediol diacrylate.
According to the invention, the blowing agent or blowing agent mixture is used in an amount of from 1 to 10% by weight, preferably from 3 to 9% by weight, in particular from 4 to 8% by weight, based on the styrene
REFERENCES:
patent: 5229429 (1993-07-01), Hahn et al.
patent: 5258415 (1993-11-01), Hahn et al.
Alicke Gerhard
Dietzen Franz-Josef
Hahn Manfred
Heinen Hartmut
Weber Reinhold
BASF - Aktiengesellschaft
Foelak Morton
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