Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
349
This inyention relates to an el~stic soft foamed materi.al
and a pxocess of preparillg it,
In conve.ntional preparation of elastic soft foamed
materials, crystalline calc;te or dolomite as filler is mixed
with the basic materi~I, which may be caoutchouc latices, plas-
tic dispersions, soft polyurethane adducts, PVC plastisols etc.,
and w.ith the requisite additions, whereupon ~he composition i.s
expanded, tha~c is~ whisked or ~oamed, until the desired densit~
has been obtained. By increasing the filler conten~ and the
expansion it is possible to reduce the cost of the product,
which will, however, impair the strength propérties of -the ~ .
. product:.Quality xequirements therefore put a limit to these
- measures.
Since a couple of years, small gas-filled hollow
spheres of aluminum silicate, so-called microspheres, are
available on the market, these microspheres being a constituènt
part of so-called fly-ash, which is obtained in coal-fired
power plants. The microspheres occur in sizes of a~out 20-300
microns havin~ a wall thickness of between 3 and 5 microns and ;.
a vol~ne weight of 0.3-0.7 g/cm3. The microspheres have been
used as weight lowering agents in curable plastic composltio~s,
concrete etc. .
The object of the present invention is t~ improve, with
the aid of said microspheres, the prior art tvpes of elastic
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so~t foamed materials, whlch as basic materlal have natural
caoutchouc latex or artificial caoutchouc latex or mixtures
thereof, plastic dispexsions, soft polyurethane adducts,
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PVC plastisols etc. ~y admixture of microspheres with the
basic mat:erial and subsequent expansion Of the m~terlal, a foamed
material is obtained after a finishing treatmentt said material
having two types of gas-filled cells, viz. hollow ~as-filled
reinforced cells, and hollow gas-filled non-reinforced cells.
q'he gaseous contents of the non-reinforced cells significantly
contribute to the indentation characteristic of the material~
By reason of the high compressibility of the gas the yas or
air cells increase the resilience and softness of the foam,
these properties being desirable from many aspects. The rein-
forsed cells, on the other hand, form a non-r~siiient structure
with the surrounding plastic or elastomer composition and are
mainly determinative of the strength properties of the marerial. ;
Characteristic of the new material is that it is considerably
lighter than prior art ma~erials of a corresponding type and
possesses better strengtll properties, particularly a higher
delamination strength.
The invention will be more fully described hereinbelow
and with reference to the ~ollowing ~xamples which ~elate to the
preparation of a latex composition in the previously known
manner and according to the new process, as well as to the pre
Faration of~PVC plastisols for mechanical foaming in the pre-
viously known manner and acaording to the new Process.
EXAMPLE 1
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Preparation of a latex composition in the previously known
manner (recipe ~) and according to the new process (recipe B).
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EX~MPI.~ OF IJ~TEX CGMPOS: TION Reci~e A Recipe B
A~tificial caoutchouc late~
(67 percent dry s~lids content) 10~ 100
Vulcanizin~ paste
(40 percent dry solids content) 55 55
Natural caoutchouc latex
~60 percent dry solids content) 115 115
Crystalline filler 135 ---
Microspheres, ceramic --- 100
405 370
Poamed to y/liter - 38G 230
The composition is continuously ~ed to a Eur-O~atic~
type foaming machine, in which air is mechanically whisked into
the composition. Recipe B which contains spheres of a density
of about 0.6 g/cm , yields, after the same amount of air has
been whisked in as in recipe A, a foam which is about 150 g
lighter per liter.
The foam is supplied to a coating machine, in which the
foam is applied with the aid of a roll or doctor blade to a
web, for instance a textile carpet. The web with the foam is ~,
moved for vulcanisation through ovens having a temperature of
about 150 C.
When tested, -the foamed material thus prepared prQved to
have far better mechanical properties, for instance a higher
dQlamination strength.
- The quan~lty of microspheres added ma~ vary and amounts to
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.a maxim~ o.t clbo~ 0 perce~t by weigh~
EXA-'IPLE 2
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Prep~ration of ~!VC plasti s015 for mechanical foaming in
.he prevlously known manner (reci.pe A~ and according to the new .. .
proce$s (recipe B~. .
EXAMPLES O~ PVC PLASTISOLS FOR MECHAN CAL FO~r~ING
~ecipe A Recipe B
P~C 100 100
Plasticiz~r 60 60
S~abilizer . ~. 2
Foam emulsifier 4 4
Cr~stall.ine filler, for instance calcite 20
Micros~heres, ceramic ~-- 20
. ~.86 186
Foamed ~o ~ t;er 500 425
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The plastisol i5 continuously fed into a Eur-O~Matic
or Oakes type foaming machine. In this machine air can be
whisked into the PVC paste because of the existence of foam
e~uls.ifiers i.n the)composition. These emulsifiers can also be
soap or silicon type emulsif.iers.
Depending upon t:he formulation of the composition and
the amount of air added it is possible to obtain a lighter ..
or a heavier foam. ~ecipe A includes a normally crystalline
filler (density of about 2.6 ~/cm3~ while recipe B contains ~
microspheres~ ~ecause o~ the lower density of the microspheres
~about 0.6 g/cm3) recipe B, after whisking wit~ the same
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~mO~lIlt of ~,ir as in recipe A,yields a foam which is about
75 g~liter lighter than the calcite-cont~ining oam according
to recipe A.
The mechanical strength of a foam is dependent int~ al.
on the volume weight and the employed volume of fil~er. A1~
though the fill volume is higher for the foam containing
microspheres the delamina~ion strenqth of this f~am is twice
that of a foam having calcite as filler. The admixture of
microspheres thus gives a foam of superior mechanical ~ro-
perties.
The quantity of microspheres added may vary and in
the present instance may amount to a maximum of about 50
percent calculated on the total weight of the composition~ -
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