Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
200396~
O.Z. 0050/40430
Extruded styrene polymer foam ~heets
The present invention relates to extruded foam
sheet3 based on ~tyrene polymers, which are distinguished
by high compressive strength and good heat distortion
resistance.
It is an ob~ect of the present invention to im-
prove the compressive strength and heat distortion
resistance of styrene polymer foam sheets produced by
extrusion. It i8 a further ob~ect of the present inven-
tion to reduce the power consumption and the corrosion of
the extruder during production of the shee~s, to decrease
the amount of flameproofing agents required for producing
self-extinguishing foam sheets, to reduce the density of
the foam sheets and to increase the number of cells.
lS We have found that these ob~ects are achieved,
surprisingly, by the concomitant use of small amounts of
2,3-diphenyl-2,3-dimethylbutane.
The present invention thu~ relates to extruded
styrene polymer foam sheets having high compressive
strength and a density of from 20 to 60 kg/m3 and con-
taining from 0.05 to 0.5% by weight of 2,3-diphenyl-2,3-
dimethylbutane.
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U.S. Patent 3,441,524 di~closes self-
extingui~hing ~tyrene polymers which contain organic
bromine compound~ and ~ub~tituted diphenylethanes. How- ~ ~
ever, thi~ literature does not indicate how the proper- -`
ti-- of extruded styrene polymer foam sheets can be im-
proved.
Styrene polymer foam sheet~ are produced in a
conventional manner by extruding a mixture of a styrene
polymer, a blowing agent and, if required, conventional -
additives. In an extruder, the styrene polymer plas-
ticized by heating is mixed thoroughly with the blowing
agent and the additives. The mixture then passes through
a stabilization zone, in which it is cooled to about 100-
120C with con~tant ~tirring, and i~ then extruded through
a die with expan~ion to fo~m ~heet~
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In practice, the foam sheets have a cro~s-section ~ -
of not less than 50 cm2, preferably from 100 to about 1000
cm2 The thickness of the sheets may be up to 200 mm and
the width up to 1300 mm
5The novel sheets have a density of from 20 to 60,
preferably from 25 to 40, kg/m3 ~ ;
The sheets generally have a coefficient of
thermal conduction ( A value) of from 0 022 to 0 036, ~ ~-
preferably from 0 026 to 0 032, W/mR, a compressive
10strength of from 0 1 to 0 6, in particular from 0 025 to
0 45, N/mm2, a water absorption of less than 0 5, in ~
particular less than 0 2, % by volume and high dimen- ~ -
sional stability and good heat distQrtion resistance
The sheets have a skin and in general more than
lS90%, in particular more than 96%, of the cells are closed
cells The cell size is in general from 0 1 to 0 5 mm,
preferably from 0 1 to 0 3 mm ~ ~ ;
For the purposes of the present invention,
styrene pol y rs are poly~tyrene and copolymers of sty- -;
20rene which contain not less than 50% by weight of styrene
a~ copolymerized unit~ ~xamples of suitable comonomers - ~-
are ~-methylstyrene, styrene~ whieh are halogenated or
alkylated in the nueleu~, aerylonitrile, e~ters of -~
(meth)aerylie aeid with aleohols of 1 to 8 earbon atoms,
25N-vinyl eompound~, sueh a- vinylcarbazolo, maleic an- ;~
hydride or mall amount~ of compounda whieh eontain two
poly~erizable doubl- bond~, ~ueh a~ butadiene, divinyl-
benz-ne or butanediol diaerylate
The blowing agent- u~ed are the eonventional ~- i
30phy~ieal blowing agents whieh do not dissol~e styrene
polymer~ but are soluble in the styrene polymer melt
under pressure ~xamples of suitable substanees are C3-
C~-hydroearbon~, such as propane, n-butane, n-pentane,
isopentane, neopentane and mi~tures thereof, ehlorohydro-
35earbon~, sueh a- methyl ehloride and/or ethyl chloride,~' ''.'',-;'.''~'.`!,
fluoroehlorohydroearbon~, sueh a- dichlorodifluoromethane ~-
and/or l,l-difluoro-l-ehloroethane, and earbon dio~ide ~ -~
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X003966
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Preferably used blowing agents are mixtures of the stated
compounds. The optimum composition of the mixtures can -~
readily be determined by preliminary experiments. The
blowing agent is used in general in amounts of from 7 to
s 16% by weight, based on the ~tyrene polymer. -
The concomitant use of 2,3-diphenyl-2,3-dimethyl-
butane in an amount of from 0.05 to 0.5, preferably from
0.1 to 0.3, % by weight is essential for the invention.
The additive is present in the styrene polymer in dis-
solved or homogeneously dispersed form. ~ ;
Conventional additives which may be added to the
styrene polymer are a blowing agent mixture, antistatic
agents, stabilizers, colorants, lubricants, fillers,
nucleating agents and/or flameproofing agents in conven~
tional amounts.
Preferably used flameproofing agents are organic
bromine compounds which have two or more bromine atoms
and a bromine content of not less than 40~ by weight.
Suitable bromine compounds are 1,2,3,4-tetrabromobutane, ~ i
tetrabromopentane, tribromobutane, 1-chloro-2,3,4,5,6- ~ `
pentabromocyclohexane, hexabromocyclohexane, hexabromo-
cyclododecane, octabromocyclohexadecane, dibromomethyl-
benzene, pentabromodiphenyl ether, esters and acetals of ;;~
dibromopropenol, such aa tris-(2,3-dibromopropyl) phos-
phate. 1,2,5,6,9,10-Hexabromocyclododecane is preferably
u-ed. The foa~ contain the bromine compound in general
in an amount uch that the bromine content ia from 0.3 to
3, preferably from 0.3 to 2, in particular from 0.3 to 1,
~ by weight, ba~ed on the styrene polymer. Compared with
corre~ponding foams without 2,3-diphenyl-2,3-diethyl-
butane, only le~ than half the amount of bromine com-
pound i8 reguired to achieve the same flameproofing
effect. By reducing the content of the bromine compound, ~ ~-
corro~ion and abrasion of the extruder screws is dr~mati-
cally reduced. -~
In the Examples, parts are by weight. -
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20039~,~
_ 4 _ o z 0050/40430
EXAMPLE 1 (COMPARISON)
1~0 parts of polystyrene having a melt flow index
of 4 5, 0 1 part of talc as a nucleating agent for
regulating the cell size and 1 7 parts of hexabromocyclo-
dodecane were fed continuously to an extruder having an
internal screw diameter of 120 mm At the same time, a
blowing agent mixture consisting of 1 9 parts of ethyl
chloride and 14 parts of dichlorodifluoromethane was
forced continuously through an inlet orifice in the ex-
truder The gel kneaded uniformly in the extruder was
passed through a stabilization zone and, after a resi-
dence time of 15 minutes, was extruded at an outlet
t~mperature of 105C through a 1 5 mm die having a width
of 300 mm, into the atmosphere The foam was passed
through a shaping channel connected to the extruder, an
expanded poly~tyrene web having a cross-section of 650 x
50 mm being formed
The e~panded product wa~ cut into sheets measur-
ing 600 x 50 x 1250 m~ The samples were tested after
~torage for 30 d~ys, and the ~ value from the measure-
ment- after 30 and 60 day~ wa- extrapolated to a storage
tim- of 2 year~ The ~ value ~eoefficient of therm~
conduetion) aecording to D$N 52,612, the foam den~ity
according to DIN 53,420, the cell size according to ASTM
D 3842-69, the proportion of elo~ed eell~ aeeording to
DIN-I80 4590, th w~ter ab-orption of entire heet~
aeeordfng to DIN 53,434, the eompre~-lve ~tre-s aeeording
to DIN 53,421 and the heat di-tortion re-i~tanee aecord-
ing to DIN 53,431 were mea~ured
To determine the total combustion time, the
following fl~ e te~t WaB carried outs a 20 mm thick
he t saapl- cut fro~ the center of the sheet to be
te~ted wa- treated with a S e~ long propane flame along
the long ide 10 time- The ~verage wa- caleulated for
the tot~l eombu~tion time~ ea~ured until extinction
oeeurred, for the-e 10 te~t~ The value i~ taken a~ the
tot~l co bu-tion ti~e
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20039~$
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EXAMPLE 2 - - -~
The procedure described in Example 1 was fol~
lowed, except that only 0.76 parts of hexabromocyclo-
dodecane was used instead of 1.7 part~, and in addition
0.15 part of 2,3-diphenyl-2,3-dimethylbutane was
employed. --~
EXAMPLE 3 ~ :-
The procedure described in Example 1 was fol- ~ -~
lowed, except that in this case 1.5 parts of hexabromo~
cyclododecane were used instead of 1.7 parts, and in
addition 0.05 part of 2,3-diphenyl-2,3-dimethylbutane was
employed. -
EXAMPLE 4
The procedure described in Example 1 was fol- - ;
lowed, except that in this case 0.5 part of hexabromo~
cyclododecane were used instead of 1.7 parts, and in
addition 0.05 part of 2,3-diphenyl-2,3-dimethylbutane was ~;~
employed.
The results obtained are s~mm~rized in the Table.
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2003966
- 6 - O- Z . 0050~40430
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