~h~ E).~esent lnventi.on relate3 ~o ~Jater v~.pou.r
permeabJ.e sheet,material.s~ ~uch rnaterials fi~d many
u~es a~d i.Il particular find use as shoe upper
materials and clothing materials~ ,
~n excellcllt mi.cxoporous polyu.rethane sheet '
; material which is free from pxe-fo~med fibrous ~'
rei~orcement and which consists'of a micropo.,ous
strength impar-ti~g substrate layer about 1~35 mm. , ' ~''
thick having a cle~sity of about 0.55 grams per s~axe ,,
~ , ,
metre and ha~ing in-tegrally attached to o~e ~ace a
; ~, thinner less dense surface layer is alread~ known. , .. '
~ ~he surface layer is tgpic,ally a~out 0.35 mm. thick ~,
,
and has a de~sity of about 0.35 grams per cc. q'he ~ :
: ~' free surface of the surface layex is give~ a very ,.~
15~ thin surface finish. . ~' ?
his-material has a gaod cut tear stre~gth ',' ",:
for fabrleation into shoes and an ade4uate ~ater , ,'
vapour pexmeabilit~ prior to fi.nishi~g so that after
appllcatlon o~ the fi~ishi~g the p~oduct still has a , '~ ' .
20~ su~floient,water vapour permeability for use in
shoe~uppers. However, for cereain uses the product ,.. '~.
; is somewhat stiffo ~he stiffness of such a materiaI ."
could be rèduced b~ xeducing the thickness of the
strength impaxting substrate but we have found tha~
:25 ~this results i~ a product havl~g~inade~uate tear
strength and.in additioQ a product below 1.5 mm,
thick has~ ade~uate ~substance fox commerc:ial u,se as
: :a~men'~s shoa uppera
Thus in these k~own materials the ratio of cut ';~ ;
30 tear stxength to stif~ness (as de~ined herein) is ,~
', K~NK/Sd~R
~ ~ 1.':- , '"
- 1~5~196
usu~ .y about 2 to 3.4.
W~ have discovered that by reducin~ the
thi.ckness of the substjrate :Layer and at the same
ti~nc givin~ it a stronger structure and by formin~
a ~ur-ther suxface layer (whlch will be termed
herein the flesh layer~, on the face o~ the
substrate remote from the topcoat layer substantial
reduction i~ stiffness can be ach.ieved whilst
, maintaining ade~uate tear strength and water vapour
per~eability and product thickness.
It is thus a~ object o~ the present invention
to produce water vapour permeable materials free
' ~ from ~ibrous reinforcement having ratios of cut
tear stre~gth to stiffness in excess of 4 and
15 desirably in excess of 5~ -
~ ,
U.S. Patent 3284274 discloses that in making
manmade suedes and smooth surface leather-like .
materials for shoe uppers a layer o:~ cellular honey-
comb like macroporous polymer material may be applied
to both sides of a flexible porous substrate which
can be a~sheet of non-fibrous porous pol~meric .
material such as a tough microporous filmc
We have found that unless the su~strate is made
both denser a~d thicker than either the fleshcoat
~layer or the topcoat layer the desirable improvement . ~ ;~
in the ratio of cut tear strength to stiffness is ~
not obtained. .;-
hus according to the prèsent inventio~ a water
vapour permeable so~t flexible sheet material .;:~1
I ~ ~ 30 suitable for use as the upper o~ a sh~e ;.n place o~ `~
', , , -
KDI~/SdeR
. :
:, 1
5~ 9 ~
lea-ther is at lea~t 0.8 mmO e.g., 1.0 - 2.0 ox 009 -
l.rf ~ thick and has at 1ea~Jt three superimposed
' pOXOllS layers of elastomeric polymer the material
being ~xee ~rom fibxous re:in~orcement and havlng ~n
5. elo~gation at break in excess of 200~o a~d comprises a
strength imparting poxous elastomexic polymer sub-
strate layex ~po~d between a porous elastomeri¢
polymer ~leshcoat layer and a porous elastomeric poly-
mer topcoat la~er9 the substra-t~ laye~ having a higher
10. de~si-ty than the ~leshcoat ox topcoat layers a~d
being thicke.r than either the ~leshcoat or the topcoat
layers and the combi~ed thick~ess o~ the fleshcoat
and the topcoat la~ers being in the range 30% to 175%
, . .
o~ the thickness o~ the su~stxate layer, e.g., 65to ~;
15~ to 125% especially 70% to 110% Of the thickness o~
the substrate layer a~d desirabl~ the thic~ess o~
~ th~ topcoat layer being in the range 150% to 50% o~
;~ the thickness of the ~leshcoat layer. ~he thickness
o~the ~opcoat ma~ be in th~ range 10% to 95% e~g. 30~ -
~ ~ . :- .
20. to 80% o~ the ~hick~ess o~ the substrate. ~he flesh~
coat may be in the range 10~ o~ 20~o -tO 95~o o~ the
~ , . . .
thick~eæs of the s~bstrata,
~h~ ratio o~ the thick~ess o~ -the topcoa-t to the ;~
." . "
thickness o~ the substxate desirably lie~ ~ithin the `~
25. range l~5:1 to 0.5~1 more particularly 1.2:1 to 0,8:1
.
a~d iæ pre~erably about 1:1, thuæ the material is ~ -
su~stantially symmetrical about the plane through the
... . .
centxe o~ the inner (~ubstrate) layer~
In a pxsfe.rred foxm o~ -the inve~tion ~he strength
30. imparting porous elastomeric polymer substrate layex
'
KDNK/~RC - 4 -
.~.. .... . . . .
~05'~
has compact voids randomly distributecl through the layer
intercommunicating via pores penetrating the walls be-
tween the voids, and the fleshcoat layer is microporous
having compact voids randomly distributed through the
layer intercommunicating via pores penetrating the walls
between the voids, and the topcoat layer is microporous
having compact voids randomly distributed through the
layer intercommunicating via pores pene*rating the walls
between the voids, and the substrate is characterised by
having wall thicknesses between the voids generally
greater than those in the fleshcoat or the topcoat.
The inven~ion enables preferred materials to be
made which are further characterised by having a cut tear
strength (as defined herein) of at least 1.5, e.g., at
least 2.3 kg. and a ratio of cut tear strength to stiff-
~ness Cas defined herein) of at least 4.2, e.g., in the
range 5.0 to 10.5 or preferably 6 to 10 and a stiffness ;~
,
(as herein defined) of not more than 0.65 and preferable
in the range 0.25 to 0.60, e.g., 0.30 to 0.50.
According to a preferred form of the present in- ; ~ ~
vention the substrate layer consists of a porous matrix of ~ -
elastomeric polymer affording a plurality of compact voids
intercommunicating by pores, the said substrate layer ,
being from 0.5 to 1.2., or 1.5 e.g., 0.6 to 1.0 mm pre-
ferably 0.7 to 0.9 mm thick and having a total void volume
or porosity in excess of 50% and at least 65% of the poro-
sity being provided by pores and the voids with which the
said pores interconnect, the said pores having diameters
of at least 5.0 microns and preferably less than 20 microns `
as determined by mercury intrusion penetrometry. T~e
mean pore diameter of the substrate
: :
- 5 -
~'' ' '
-- . : ,:
, ~ , ,. .
~ ~5~ 19 ~
layer is pre~erably in the range 5 to 20
m~cro~s~ preferably 7 to 15 microns, e.g., lO
to 12 microns as de-termlned by mercury intrusion
penetrome-tr~.
~`he fleshcoat and topcoat layers are ~ -
preferably integrally adhered -to the substrate layer.
~he fleshcoat and topcoat layers preferably have
thicknesses in the range 0.20 to 0.45 mm. ~he top-
coat la~er and the ~leshcoat layer desirably have
densities of less than 0O40 grams per cc., e.g.,
in the range 0.2 to 0. 4 9 e.g., Oa 25 to Q.35O
~he elastomeric polymer is preferably a~ `-
elastomeric polyurethane hut can be used i~ admixture
with other thermoplastic polymers such as polyvinyl -
chloride and its co-pol~mers and acr~lonitrile
pol~mers and co polymers
~he preferred polyurethane polymers are
essentially linear polyurethanes produced ~rom a
diisocyanate, a monomeric diol and a polyester or a
- 20 polye-ther o~ molecular weight l,000 to 3,000, the ~ `
polyurethane having a~ i~trinsic viscosity in
.~ , .
dimethyl formamide of at least 0.8 ~ /g.
However, the preferred polymer is a polyester
based pol~urethane materiaI having a Shore hardness
- 2', of 75A or 90~ to 60D preferably at least 98A as a
soli~ continuous sheet at 25C. ~his material may be
used for all three layers. Eowever, in a pre~erred
product it is used only for the strength imparting
substrate la~er and a pol~urethane having a lower
~0 Shore hardness than -the substrate polyurethane and
6 -
KDNK/~deR
., .~ .
9 ~
thus a ~ofter feel i.s used for the topcoat layer
and. the flesh layer. ~his softer material may have
a nitrogen content of about 2.5/o or Z.8 to 3.0 or
3.5 to 4~0~0n ~his soft material can be made b~
increasi~g the ratio of polyester to glycol
result.ing in a lower re~uirement o~ diisocyanateO
The polyurethane for the substrate preferably has
a higher nitrogen co~te~t, e.g., at least 4.~/o or
405% or moren ~he soft polyurethane for the top~
coat la~er and the flesh layer may be based on a
polyether polyur~thane instead of a pol~ester -~
polyurethane.
In one form of the in~ention~ the polyurethanes
.
used for the topcoat, fleshcoat ~ld substxate are
made ~rom the same polyester~ diol and diisocyanate
a~d the polyurethane used for the substrate has a
- nitrogen content o~ at least 4~o whilst the polyure~
thanes used for the topcoat and fleshcoat have lower
~`~ nitro~en conte~ts than the substrate polyurethane. ~-
~he subs~rate layer preferabl~ has a porosity in
the range 5~0 to 65% and less than 7% of -the total
porosity is provided b~ pores and -the voids with which `
they interconnect the said pores ha~ing diameters in
excess of 100 mi.crons and at least 50~ of the total -~ `
~ . .
pGrosity is provided by pores a~d the voids with
which they interconnect the said pores having
- ,
diameters in the ran~e 6.4 to 17.5 microns~
;,
he substrate layer when a cut cross-section is ` `-
viewed is preferably further characterised b~ compact
voids the ma~ority of which ha~e maximum dime~sions
- 7 -
KDNK~deR
:~ .
in the plane of the cross-section of 30 to 100
microns, the majority of these voi.ds having
shortest transverse dimensions i~ the plane of
the cut surface of 1/~ their maximum dimension
and above, the shapes of the ~oids being non-
spherical and though i..rregular in outline compact
in shape, the voids being separated by more dense
regions ~which can be considered as thicker walls~
~-:
- . . which contain smaller pores visible at 150-fold
magni~ication the majority of which are 1 to 30
micro~s across and spaced apart by 1 to 10 microns -
the majority of these denser regions being of 30
to 100 microns across between adjacent`larger voids~
~he microporous ~leshcoat and topcoat layers
15 when a cut cxoss-section i9 viewed are preferably :
charac~erised by irregular shaped through compact
voids from 5 to 75 microns across the majority -~ `
being 20 to 50 microns across the ~aid voids being
def:ined or surrounded b~ thin walls 1 to 5 microns /`~;
thick the voids intercommunicating by pores passing
through these thin walls~
: ~ ~he ~ovel product may be made by a process
` comprising depositing a layer o~ coagulable -
elastomeric pol~mer Pleshcoat composition on a
porous support to form the fleshcoàt layer, then
prior-to coagulation depositing a layer o~ coagulable ~:`
elastomeric polymer substrate composition on top of
the layer o~ ~leshcoat composition and then prior to ` ~ ~ `
ooagulation depositing a layer of coagulable
elastomeric t~ coat co~position on top of the layer
- 8 -
KDNE/SdeR
-,'
1~5'~
of subs~rate composition, and then coagulating
the composite material to an integrally adhered
microporous three~layer structure free from
fibrous rein~orcement at least the substrate com- ;
position an~ at least one o~ the flesbcoat or top-
coat compositions containing a removable particulate
filler, the filler in the said fleshcoat or topcoat
compositi~ns having an average particle size smaller
than that used in the substrate composition.
lU~he elastomeric polymers are pre~erably
elastomeric polyurethanes of intrjnsic viscosity o~ at
least 0.8 e.g.9 1.0 to 2.0 or 1.0 to 1.~ decilitre~/g.
{measured i~ dilute solution in dimethylform~mide). -
~he polyurethanes of the fleshcoat and topcoat layers
15 are desirabl~ so~ter than that of the substrate layer, ` ; ~`;
e.g., the substrate po}ymer as a th m void free film
~ 0.2 to 0~4-~mm. thick may have a modulus at 25%
-~ ex*ension of at least 55 kg/cm2, e.g., 60 to 100 or
70 to 80 a~d the ~leshcoat and topcoat polymers as a
thin void free film 0.2 to 0.4 mm. thick ma~ ha~ a
modulus at 25% extension of less than 55 kgO/cm2, - -~
- e.g., 30 to 45 or 50 kg/cm2.
~he ~ubstrate composition preferably comprises
,, , ~. .
the substrate polyurethane dissolved in a polar
organic sol~ent, e.g., dimeth~lfo~mamide, at at
least 20~o b~ weight concentration, eOgo ~ 25% to 4~/q
e.g.1 30% to 35% with a~particulate dissol~able
filler, e.g., a water soluble inorganic salt dis-
persed therethrough, which is substantially insoluble
30 in the organic solyent, &nd the filler has an average ~; -
~ 9 ~ -
~ K~NK/SdeR -~ -
.,,. ~ 1~ ~.
' ~
~3~ LC~6
particle size as determined by Coulter counter
measurements in the range 20 to 200 microns~ e.g.
25 to 75 or 50 microns and the ratio of filler to
polymer is in the range 1.8 : 1 to 2.7 : 1, e.g., ~
1.9 : 1 to 2.2 : 1 parts by weight. More particu- ~ -
larly it is preferred to use a particle size of ~ ;~
30 to 95 microns with a filler to polymer ratio in ~ ;
the range 1.8 : 1 to 2.8 : 1 at the 30 micron salt -
particle size and in the range 1.8 : 1 to`4.0 : 1
at about the 95 micron particle size.
As taught in the specifieation of British
Patent No. 1465,557 working in this range produces
a material of improved strength. Attention is
particularly directed to its teaching as to the
preferred formulations for a substrate for an
artificial lea1her and the disclosure concerning
preferred filler particle sizes. It is pre~
ferred to miake use of this teaching in connection
with the substrate for the present in~entionO ~ ~;
The flesh and topcoat compositions
similarly contain dispersed filler but it is pre-
ferred that the filler should have an average part~
icle size below 20 microns, eOgO~ in the range 1 to 15
.~ - .
. . .
or 5 to 10 microns. The ratio of filler to polymer is -~
preferably at least 2.5 : 1, eOgO~ in the range
3 : 1 to 6 : 1 parts by weightO ~ ~ ~
' ~ ~''` '
-10-
~L05'~g~;
The polymer composition is preferably pro- ~
duced by forming the polymer in solution from low mole- ;
cular weight reactants in solution to produce a
polymer solution of the desired concentration and
then mixing the particulate filler (which is prefer-
ably wa~er soluble) into the polymer solution, e.g.,
with a high energy mixer. The blend is then co-
agulated to self-supporting form by means of a non-
solvent liquid, e.g., it is preferably extruded on- ~
to a porous belt and contacted with non~solvent,
e.g., water ~e.g., at 20C. - 60C.) or water solvent
blends~ er~g.l of 5% to 30%~solvent content, having a
non-solvent action, e.g., by immersion in the liquid
non-solvent. The non-solvents used can contain ~ -~
proportions of dissolved filler, e.g., in continuous
operation contents of as high as 15% or so of filler
can be tolerated. Pure non-solvents are equally ~;
;: `:
effective.
The coagulated self-supporting layer is
then preferably stripped from the belt whilst wet and
immersed in non-solvent, e.g., heated to, say, 60C.,
and the dissolvable filler leached out ~o a
''`, .'~,'. .;,
' ~
.~'`-~ .
" , ' . ~' " '
~ ~5~ ~9 6
sa-~isfa.cto.ry level, e.g., not mo.re than 1,000 mg. ~ ~
of filler per s~uare metre of sheet should remain. ~ ;
The leached. layer is then dried and can be
given c~ny appropriate finishing operation.
5. ~he preferxed density of the substrate layer
of :the product is betwee~ 0.4 and 0.7 gr. per cc.
;:
thollgh it ma~ be up to 0.8 for cextain uses. .
: It is pre~erred to use flller particle sizes
and filler to pol~mer ratios such that the density
I lOo of the substrate layer remains within the range
0/4 to 0O5 or 0055O ~h~s with the lower end. of the
ran~e o~ permi-t-ted particle sizes the lower end of -:
the permi.tted range o.~ ratios of filler to polymer ~
~ .
: - . . . .-
.. ~.. ..
- '.. ' ~ , .
` :
KD~/SdeR -12~
, ' ~ ~ ! , . . , , , ' , . . .
5~
is preferably used and at the hi.gher end of the
range o~ particle sizes the higher end of the
xange of ratios of fi.ller to polymer is pre~er-
abl~ used, e.g., with a~erage particle sizes of
20 to 30 microns the filler ra-tio is preferably
1.9 : 1 to 2.1 : 1 with ~0 to 60 micron filler
f.rom 2~1 : 1 to 2.2 : 1, 2.3 : 1 or 2.4 : 1 and
with filler paxt.icle sizes above 60 microns salt
ratios of abo~e 2.2 : 1 or 2~ 4 : 1
~he invention may be put into pract.ice i~
; various wa~s and certain specific embodime~nts will
be described by wa~ of example with reference to
the accompan~lng photomicrographs which are all
vertical cross-sections through microporous sheet
materials at 55-fold magnification and in which:
~i~ures 1 to 8 are of three~layer materials `~
in accordance wi~h the invention described in
~Examples 1 to 8 respecti~e, and ~-
Figure 9 is a diagrammatic side elevation. o~
a test rig use~ for determining the stiffness of
ma~erials described hereiu.
~'he photomicrographs of Figures 1 to 8 were
~, ~
;~ taken on a Cambridge Instxuments ~imited.
Stereoscan Mark 2 electron microscope. ~he
; ~ 25 photomicrographs were prepaxed ~y cutting a smooth ~`
clean cross-section through the sheet samplesO
~` ~he cut surface was then coated with a thin metallic,
e.gO, gold or palladium reflecting layer as is con~
ventional in preparing samples ~or electron photo- ~ -
mi~rograph~. A stream of electrons was then directed
: . ; ~-,:~:,
- 13 - ;
KD~KfSaeR
,
, .'.' :~'
5'~1~3
onto the cut surface at 45C. and the electrons
reflected ~rom the surXace also at 45C. were
colLected and used to produce an optical image ~;
which was photographed~ It will be apprecia~ea
that the depth oP focus of such photographs is ~ ~ ~
very much ~reater than i~ optical photography and ~ ~ -
thus that in e~ect one is able to see into the
voids and cavities~
~ ;:"
In the examples a vaxiet~ oX polyurethane
pol~mers are used~ ~hey were made in solution in
dimethy1formamide :~rom a polyester or polyether by ~^
reaction with a diol and a diisocyanate under an
inert atmosphere.
rethane~
880 parts (I~ o~ pure N,N-dimeth~lformamide . `;
uere placed in a 1,500 parts (II) reactor ~lushed
with dry nitrogen. 0.027 parts ~I~) of paratolue~e
sulphonic acid a~d 0.020 parts (23 oI dibu~yltin
dilaurate were dissol~ed in the dimeth~l~o~amideO
205.0 parts (III) o~ Desmophen~2001 polyester ~a~
hydroxyl-terminated pol~estex o~ 2,000 molecular ~5~`
weight, ha~ing an acid number of less than 2 and
a hydro~yl number of about 55 mgO KQH~per g~ made
from about 1~m~1 butane diol -1,4,;1~12 mol
~; 25 ethylene gl~col and 2 mols adipic acid) and 48
parta~(IV~ of butane diol -1,4 were then~added and
d1ssolved i~ the mixture a~d the temperature o~ the I
mixture adjusted to 25C.
171.6 parts (~) o~ 4,4-diphen~lmethanediiso-
~;; ; 30 cyanate were then added bit by bit care being taken
D~SaeR~ -
~trade~ ~)7qrk
. ..
:~, ~ ' , 1,, ~ `.
, : , .
.
05~
to keep the temperature from rising above 50C.
Once the addition was complete the mixture was
heated to 60C. and maintained at that tempera-
ture for 1-~ hours with stirring. ~he excess
unreacted isocyanate content ~as then determined ' ,
by titration of an ali~uo to Su~ficient butane
diol ~3.0 parts (VI~) was then added to react ' ~ ~,
esse~tially stoichiometrically with the unreacted
isoc~anate. ~he mixture was then maintained at
60Q. with stirring'and the viscosity measured
periodically unti] it had risen to a value of ~ -
about 3,500 poise (Brookfield 5 or 6 spindle) as ;,
corrected to 24C. 4010 parts (VII) of butane `;,
- diol 1,4 were then added as capping agent to
; 15 terminate the I~eactio~ dissolved in 3.5 parts ~VIII) ~'
of N7N-dimethyl~ormam'ide. ''
,~, .
~~he nitrogen content was about 4~5Yo and the `',~
.,
polyester con~ent about 50YO~ The pol~urethane had
I ~ a Shore hardness of 55D as a solid continuous sheet " ;~
~, ~ 20 at 25C
he polyurethane has the following physical
properties~
,, ~he solution has-a viscosity of 4,100 poise at
` ~ 330~/o solids at 24C. (Brook~ield RV~ No. 7 spindle
2.5'rpm); an intrinsic viscosity of 1.08 decilitre/ , '~
gram;`''and a k' of 0.60~ A void free film cast from
th~solution by slow e~raporation of the solvent has ,',~
a tensile,modulus (kg/cm2) at 5%, 25yo~ 50Yo and lO~o
elongation of 2703, 74.5, 95~8 and 120 respectively;
a tenslle strength (kg~cm2) of 589; an elongation a-t
- 1
~DN~SdeR ' ''~
.
~ ~:
96
the crystalline point of 48~XJ and at br~ak of
615%; a cut tear strength of 180 kg/cm and a
tear strength to 25% modulu~ ratio of 2.4. ;;;.
~ hane 2 : ~.
~his is made in the same way as Polyurethane 1 ~ -.
but the amounts of the reactants are varied. .~ ~.
DM~ is 900 parts,
paratoluene sulphonic acid (IX) is 0.06 parts, . ~. -
dibu~yltin di.laurate (X) is 0.027 parts, ;~
Desmophen 2001 .
polyester (IIX) is ?82~4 parts, .
butane diol (IV) is 30.0 parts,
4,4'-diphenylmethanediisocyanate (V) is
132.6 parts~
butane diol (VI) is 5 parts, ..
butane diol ~VII) is 5 parts, and `. ~`~
DMF (VII:[) is 100 parts-.
~ his gives a polymer with 3.3yO nitrogen
-~ ~ co~tent
~he solution has a visooslty at 33.2% solids "~
at 24C~`of 4,100 poise; an intrinsic viscosity of
i . -
1.145; a k' of 0~48. A film cast from the solution
as for polyu-rethane 1 has a tensile modulus (kg/cm2)
, ~
. at 10~o7 25% and 50~o of 23.5, 37O9 and 49.6 respec~
: 25 tively; a tensile strength (kg/cm2) of 465; an .. .
; elongation at the-crystalline point of 620 at break ..
of 710%; a cut tear strength of 113 kg/cm and a
- tear strength to 25Yo modulus ratio o~ 2.98. x~
ne 3
~his is made in the same way as pol~ure~hane 1
- 16
KDi~/SdeR
: ~
~ .
- 1,
~ 05'~
but the clmOUnt. of the reactants ~re varied and
Bayer polyester Desmophen trial product I~ 1816 ~ ;
is us~d i.nstead of Desmophen 20010 PU 1816 is a
hyaroxyl texminated polyeste~r of 2,250 molec~lar
weight, having an acid number of less than 2 and
a hydroxyl nu~her of 50 ~2 mgO KOH per gram and is
similar to Desmophen 2001 apart from its diol
compo~en-t.
DMF (I) is 900 parts,
paratoluene sulphonic acid (I~) i.s 0.06 parts,
dibutyltin dilaurate (~) is 0.027 parts, ~ ~-
i - . ~.
polyester PU 1816 (Il:I) is 271.3 parts,
buta:ne aiOl (IV) is- 3~.0 parts,
4,4'-diphenylmethanediisoc~anate ~V) is ~ -
140.6 parts,
butane di.ol ~I) is 5.1 parts,
butalle diol (VII) is 5.0 parts, and
~! ~ DM~ (VIII) ls 100 parts.
.. . . ..
hie gives a polymer with a 3.5Yo nitrogen
20 contenl.~ -~
- ~he solution has a viscosity at 33~2~o solids -
at 24C~ o~ 3~400 poise; an intrinsic viscosit~ of
1.11; a~d a k' of 0~49 A film cast from the
solutio~ as for polyurethane 1 has a tensile
~` ~ 25 modulus (kg/cm2) at 10/o~ 25% and 50% of 19~0, .
36vO and 4~.2 respectivel~; a tensile strength
i " (kg/cm2) of 519; an elongation at the crystalline ;
~ ~ point o~ 560'~o and at bxeal~ o~ 61~0~o; a cut tear
; ~ ~ strength Of 143 k~/cm and a tear strength to ~5%
:
:` 30 modulus ratio of 3~98~ ` `;
- 17 -
KDN~/Sde~
,-.
..
. . .
5~JI9~; ',
~o~4
~his i5 made in the same way as polyurethane 1 .;
except that the dibutyl-tindilaurate catal~rst, - .-
component (X), is omltted~ ~he reacta~ts are as , : -
5 follows~
. ,: . .
DMF (I) 900~.00 parts
Paratoluene sulphonic acid (IX) 0.06 parts
Polymeg 1930 polyether (~.II) 254.20 parts .
Butane d.iol (IV) 38.30 parts `-.
lO 4,4'-di.phenylmethanediiæocyanate 152.70 parts
Buta~e diol (Vl) 3O~0 parts
Butane diol ~VII~ 5.00 parts . ~.
DM~' ~VIII) 20.00 parts ~ .
~hls gives a polymer with a 3~8Yo nitroge~
15 content, .Polymeg 19~0 is a hydro~yl terminated
,
poly-tetramethyle~e glycol havi~lg a molecular `.
weigh-t of 1930, a hydro}~yl number of 53 to 59 and
a very low aci.d numbe.r not in excess of 0.05 mg.
KOH per gram~ It has a meltirLg point of 38C. and ..
: 20 : a specific gravity of 00985 grams per cc at 25C.
q!he pol~mer solution has a viscosity at 33.2%
solids at 24C. o~ 4,400 poise; arL intrillsic
viscosity of 0.88 dl/g; and a k' of 0065. A film
oast from the solution as for pol~urethane l had a
teIlsile modulus (kgfcm2~ at 5%, 25%~ 50% and 100%
exte~sion of 9.~, 37.4, 50.8 and 66.9 respeGtively;
- a tensile stren&~th (kg/cm2~ of 447; an elongation
at the cr;ystalli~e` point of 680/~ and at brea~ o~
: ~- ~ .. .
715Jo~ a cut tear strength of 95.8 kg~cm and a tear
; ~ 30 strength to 25% modulus ratio of 2.55. :
KD:NK~SdeP.
tr~cle.
:, ... :
~; .
'.rhe Remov~b].e Filler
. . ~
Sodil~n chlo.ride ~or incleed other e~uivalent
preferc~ly wate.r soluble removable filler) ~jas
ground in a pin and disc mill with air clas~
cation to separate out fines and return oversi~e
particlcs for regrinding. ~he sodium chloride
powder befoxe dispersing in the polymer solution
had its particle size determined by the Coulter
counter techni~ue. . ~ ~
~ou~.ter counter measurement of particle size .~ -
is a well known techni~ue and is widely used and
; described in th~ literature, for example, in the ~ :
book 'q'he Coulter Principle of Particle Size :
Measu.rement' by To Allen and K~ Marshall~ available
:
in the National Library o~ Science and Intention
(Patent Office Branch) in ~ondon~
However, a brie~ description of the techni~ue
will now be given. The sodium chloride whose
. .
. particle size is to be measured is suspended as a - ~-~
~ery dilute suspension in a saturated 4% solution
~; o~ ammouium thiocyanate in isopropanol which is
previousl~ saturated with sodium chloride.
~he mixture is subaected to ultrasonic
vibration to ensure that none of the particles have
~ 25 agglomeratedr
.. ?he suspension is the~ plaeed i~ the measuring ~ :
` chamber OL -the apparatus which is descxibed i~ U.SO - :.
Patent 265650~. An electrode is placed in the .. .. ~-
; ~ chamberO A tube containing another electrode and
.
19 - .
; KD~/BdeR
. 1~5~ 6
having a ve~y small orifice appropriate to the
paxticle size is i.mmersed irL the suspension which
is then drawn through the tube~ For salt of 9
to 126 microns a~erage particle si~e a tubs having - .
an orifice of 280 microrLs is used. ~ach ~ime a
particle passes through the orifice a vol-tage pulse ~ ;
propoxtional to p~rticle volume is produced, the
larger the pulse the larger is the particle ;~
The electronic circuit of the irLstrument can -. ;
10 be arranged so as to count only pulses having a .
.volume withi~ a certairL range and the number of
pulses withi~L a given time within each range is
counted ~or a series o~ ranges. ~he results are
: therl ad~usted to give a distribution of particle
- ~
siz~ by weight.
~he concentration of the particles in the sample
. is arran~ed to be below the so-called 'coincidence .
leve!l', namel~, the concentratioxL at which the proba~
bili.ty o~ more than oxLe particle passing ~rough the . :
- : 20 orifice at the same time and being counted as a single
.. ~ part;icle becomes si~Li~icant, ~hus ~or salt o~
OEticle size about lO microns a 0.05 to 0.1% b~
: wei~h~ suspension is used, for about 50 mi~rons O.l to
:
: 0.3% by weight is used ana ~or about 90 microns, about
0.3 to 0.5~o b~ weight is used.
AIl:the values o~ avexage particle size given i~
the spe~ification re.~er to measurement with a Coulter
~ ~ .
~ ,
: counter industrial model ZB with a volume converter
: model M2 using a tube with an orifice o~ 280 microns
: 30 except in co~nectio~ with ~able 30
- 20
KD~/Sde~
.
j ~
, - : - , . ~: .
I ~ :
~05;2~L9~
~ or any given average particle size the
negative deviation value is the particle size below
which only 16% by weight of the to~al mass is
located and the positive deviation value is the
5. particle size above which only 16% by weight of the ;;
total mass is located~ q'he positive and negative
deviations from the average do not have to be e~ual.
~he average particle size is the size at which 50%
by weight ~alls on either side of the ~alue give~.
IO. q~us at least 84~o b~ weight of the filler
desirably has a particle size of at least 10, 15 or
30 microns and at least 68% by weight has a particle
size in the range 15 to 100 or 25 to 75 microns and
especiall~ 30 to 70 microns. `~
15. Desirabl~ also the posltive and nègative
deviations~are less than 50/o, e.g.) in the range up
to 45%, e.g~, 30 to ~5YoO
~ : , .
~.
.: i ,. .
. . ~: : : ,.i
' i ' '; . . ,
. - ~
.. .. .
i-: :.
.: :
: i ~ ::
i . , , " ;,. . .. .
~ KD~K/5deR -21~ ~ ~
.. ..
-
. : : ,; ,
~'
,
- . . . .: .. . . .. . .
1~5'~ ~L96
Exa~le 1
~ hi~ is an example of a three-layer product
in accordance with the inventio~0
~ he substrate 15 has a coarser pore structure
than the topcoat 16 and fleshcoat 17 which are
made fxom a so~ter polymer (polyurethane 2
described above~ than the substrate.
_ ~he method used to ~orm the composite adhered -~
layers is as ~ollows:
A ~leshcoat paste is doctor knife spread first ~ ;.
onto a porous polyethylene sheet, a substrate paste
.
is the~ spread over the layer of ~leshcoat paste a~d ; ~ ;
a topcoab paste æ -then spread over the substxate
paste. ~he adhered superposed layers o~ pastes
on the porous support are then immersed in pure
stationar~ water (water solvent salt blends are
e~ually e~ective) at ~0C. for~l hour with the
coated face downwards to coagulate the pol~mer i~
the pas~e to self-supportiug ~orm. ~he composite
three-layer material i6 then stripped from the
support without rupturing a~d immersed in stationary
water at 60C. for 5 hours to substa~tially
completely remove the DM~ and reduce the sodium-
c~loride content to a very low level, i.e.~ well `~
below 1000 mg/s~. metre, so as to give accurate
de~sity measuremen~s.
~he material is the~ dried at about 70C. in
an air oven for about 2 hours. Its propertles are
gi~en in ~able 1 below.
30 ~ ~he substrate paste 1 is made by mixing and
2 2
~K/SdeR `~
. .
::
~ 5 ~
milling ~he polyurethane solution descrlbed above
as pol~urethane l (diluted to 3~J0 resin concentra- ~-
tio~) with 1.90 parts per part of polyurethane of
sodium chloride particles havin~ an average particle
siæe of 27 microns (negative deviation 12 microns;
positive deviation 21 microns) followed b~
de-airing under ~acuum.
_ ~he topcoat and fleshcoat paste l ls made with
the polgurethane solution described above as
polyuretha~e 2 (diluted to 25% resin concentration)
mixed and milled with 3 parts per part o~ polyure- `
thane of sodlum chloride particles havin~ an a~erage
particle size o~ 9 micxons ~negative deviation -3
microns; positive deviatio~ +4 microns) followed by
15 de-airing under vacuum. - -
The properties of the material are given in
able l. -
A single layer material made ~rom the same
paste as substrate paste l and in the same manner
but at a considerably increased thickness ~1.4 mm.)
has its p~operties listed in ~able 3 and the
results of mercury intrusion pènetrometry listed in
~able 4
This is ~n example of a three-layer product
similar to Example l but having a ~hicker substrate
18 of less coarse st~ucture.
he material is made in the same wa~ as
Example l~ the only dîfferences being the use o~
_ 23 ~ -
RD~R/SaeR
:
- 1
~ 96
sodiu~ chloride having an average particle size
of ll~ microns (ne~ative deviation 6 micron~;
positive de~iation 15 microns) in the substrate
paste.
~he properties of the materi~l are given in
~able l.
A single layer material made from substrate
- paste at the same thickness had a densit~ of 0~56.
- ~
This is an example of a three-layer product
similar to Ex&mple 1 but having & di~ferent polymer
- in the topcoat and fle~shcoat layers.
~he method and formulations are the same as
for E~ample 1, the o~l~ dif~e~ence bein~ that the ;
; ~ 15 polyurethaIle solution desc~ibed above as polyure~
thane 3 is used in the M eshcoat and topcoat la~ers ~ ;~
and the la~ers are of different thicknesses.
~he properties of the material are given i~
~able l.
0 ~
~his is an eæample o~ a three-layer material
- similar to Example l but having a different polymer, ~:~~ namely, polyurethane 3, described above, in the ~ -~
. . . ~
~, ~ topcoat a~d fleshcoat pastes. ~lso the substra~e
paste is made with coarser sodium chloriae of
average particle size 31 microns (negative
deviation 12.5 microns; positive de~iation 18
~ miCxons? and with 2.0 parts o~ salt per part of `~
polymer. Apaxt from-~his the method and `~
; 30 for~ulations are as in E~ample l. ;~
~DNK/SdeR
,
1 :
"",i,.,,,'" ~, ~" ~ ,,", "~ " ~ "'~ "
96
The properties of the mateIial are given in
Table 1
Ex ~ _ 6
'~his is an example of a -three-layer material
similar to Example 1 but having a different polymer, ~`
n~nely, polyurethane 3 clescribed above, in the
topcoat and fleshcoat pastes. Also the substrate
p~ste is made with coarser sodium chloride of
average particle size 49 microns (negative
deviation 18.5 microns; positive deviation 31
microns) and with 2.2 parts o~ salt per part of ~
polymer. Apart from this the method and formula- ~ -
tions are as in Example 1. `~
~he propertiès of the material are gi~en in
~able 1.
Exarnple 6A
A single layer material made from a su~strate
paste closeiy similar to the substrate paste of
~i Example 6 (diffexing only slightly in salt particle `
; ~ 20 size~using the same method but at considerabl~
increased thiclness has its pxopexties listed i~ -`
~able 3 and the result o~ mercu~y intrusion ~;~
penetrometry listed in ~able 4. -
~his is an e~ample o~ a three-layer material
: .
similar to Example 1 but having a di~erent pol~mer,
namely~ po]yurethane 1 described above, :in the ;~
tQpcOat and fleshcoat pastes.
~he method and ~ormulations ~re the same as
.. :
30 Example 1 eæcept that in the substrate paste lo90 `~
KD~K/SdeR
1' : '
`
105~
parts of sodi.um chloride are used per part of
pol~urethane.
'~he properties of the material are given in~ :
~able 1. ~
5 ~ le ~ ::
'~his is an example of a three-layer material
simi.la.r to Example 1 but using smaller particle
size salt in the substrate and a harder pol~mer in
t~e fleshcoat and topcoat layers, namely, the
same polyurethane 1 as used for the substrate~
~he ~leshcoat, substrate and topcoat were
laid doN~, coagula-ted, leached and dried in a ~ r
similar ~anner tothat described in ~xample 1. ~
~he substrate ~o~mulation di~ers from ~ ~:
15 Example 1 in using sodium chloride of 17 microns . ~.
- a~erage particle size and 2.05 par-ts of sodium ~ -
. chloride per part of pol~ret;haneO The fleshcoat
~, .
and topcoat formulations are the same as those ~ .
used in Example l apart ~rom the different
.. 20 polyurethane.
~ ~he properties o~ the product are give~ in~ :
: ~ ~able 1.
: All these examples have elongations at break
in the range 375% to 500/a.
25 _ DLD~ to ~0 ~ ;~
urther examples illustrating the e~eGt of
varying substrate thickness~(EXamples 10 to 13 and
~ 1~ to 17) and salt ratio (~xamples 18 and 19,.20~ ;
: and 21 and 22 to 24) are gi~en below in '~able 1. ~ .
All these examples have elongations at break
26 _
KDN~/SdeR
~o~
in the ran~e 375~o to 5Q~/o. `
~i ' :
These are further examples illustrating (in
Example 25~ the use of a polyethel polyurethane
(polyurethane 4 above) in the outer layers and in
the other examples the effect of changing the layer -
thickness ana density relationships~
... . .
~he details of salt ratio, polymer layer ~` -
thickness~ salt par-ticle slze and physical proper- ~ i
~0 ties are given in ~ables 2A and 2R below.
Comparison of Examples 26 and 27 demonstr~të
that only a very sli~ght improvement in out tear/
sti~fness is o~tained by disposing the standard
topcoat as two thinner layèrs on either ~ace of the
.
substrate. Comparison of Examples 28 and 27
ndlcate~ that the use of coarser salt in the sub
strate v~ mark~dly improves the cut tear/ `
stiffness ratio and comparison of E~ample 28 with
~ ; .. ,
; Example 29 demonstrates the further improvement
20 obtained on reducing ~he thickness of the substrate. `
~omparison of the pairs of Examples 27 and 30
and 29 and 31 respectivaly indicates the drastically
~ - .
lower cut tear/stiffness ratio which results when -~
`~
~ the substrate layer is not thicker and more dense - ~-
; -~ 25 than the fleshcoat and topcoat layers.
l 27
~ KDNK/Sde~
' - `~`,' '' ' ;-;
~ ,
..... _ .. . .. . . . . , .
Examples 5 and 6 and 25 we:re compared for
their resistance to hydrolysis~ 2 inch by 2 inch
samples were separately s-tored-in the vapour
contained in a closed cham~er held at 90C., the
li~uid phases in the two chambers being distilled
water and 0~085 g~l a~ueous ammonia. ~he samples
were examined daily for the first appearance of
surface cracks on hand flexing, the first value
~uated, and fox crumbling o~ the material on hand
~lexi~g, the second value ~uoted. ~he ma-terial o~
h~amples 51 6 and 25 showed sur~ace cracki~g after
17, 17 and 21 days in the ammonia vapour and 3~,
33 and 46 days in the water vapour and crumbled
(to~al failure) after 18, 18 a~d 29 days in the
:
15ammonia vapour and 36, 38 and 50 days in tho water
vapour.
: :
~ ~ s demonstrates the improved hydrolysis
; ~ resistance of a material having polyether polyure~
thane in the ou-ter layers. ~; -
:: : , ~ '
` , :
. ~ ~
",~
~N~/sdeR
' :, , 1 ~ ~ ,
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i
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o o o o ~o ~ o ~ : l
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t~
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u~ ~ u~ ~D ~ o ~ ,~
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~ ~ c~ . c~l c~l C\l C~ C~ C~l C~t C\l C~l C~l
- _ _ _ _ _ _ .
.~ a.I~a~/sw~ 'I ~ ~I o~ ~ ~ ~ ~ CO t- o~
~ j I < Z ~ a',~ c~ co co ~ ~ ~ 0 co c~ T
!t ' SWIII 1!~ CO 1~ 0 1-~ 0 C~l N ~1 o~
-~sau~T~ c~
BO~ T~sal~l o o o o o o o o o o O o . .
. . ,- ..
o ~ ~ O C~l O U~ U~ C~
j ~ ssau~loFtl~ o CJ~ co co co co co c~ cr~ cO
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.,; 11}1~ ~ ~ ;t ~ Cl) C~Ji~ ~ ~) 0 ;t O .
; ' ? - ¦ SSaU~IOTl~. . . ~ ia: - i
~o~ dc)ico o o o o o o o o o o o
--~ . _ - .'
t ~ . . u~ ~o ~ o;5
:~' `c ' , ssauYo~, ~ ~0 ~0 ~ u~ 0 ~0 ~0 ;~ U~ ~ . ,, '; ~"
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a~Bl~sqns . ~ :
la~ od re re I tre r~ -I r-l . r~l rl rt rt r~
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: I . 29
- . . . . . .-. -.-
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- 30 -
~L05f~9~
~ ___ .... _ . _ .. ,
a~l'lr 3~/S1122.~
Z ~ ~3-~ a,~ ~ ~ 2 cu t~
- ' 1'e~lT,
__
-CSU3p t~ t~ C\l t~
20 ~ I I
SS3U~ . d~ r-l C~l C~
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TSU~p ~ ~ t~ t~
a~sqns oooooo .,. :~
ss3u~1~F~I~ 0~ r-lr-l
sqns . O O
O r-l r-l r-l O O O : : -
suap r-l Ci~ t
O O O O O O . :':
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SSaU~I~)Fq~ O ~ J ~ r~
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I ssa~ Ft~ u~ ~ ~ ~ u
l~2~0~; r; r-i ~i r;r-i r; rt )`
.. F~? ..._ ; `~
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- 0F~r2~ r-l r-l r-~ r-lr-l ~I r-~
"2S t~'~ 1~ t~ ~ t~
o -~
a~ Oa ~ r~ r~ r~ r-l
o~e.I rl r-l r~ r!r-l r~-l r~l .~ -
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,Qe FS C~J N C~J N C~
al~F~Xed L~ r-l r-~
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a~e~c~sqn~ c~l o o o o o o .~
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a ~ e2~s qns r-l r-l r-l r-l r-l r-l r~l
ald~ex~ u~ N C~ CO ~ O r~
- '. . :'': , :
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-- 31 ~ : -
KDN~/S~eR -
' ,~, . .
1;
- ..
L96
. ..
~l~ea.xq ~ o o o o o o '
UOF~UO'~ ~ I ~ -~
___ . .
IaI'',.S C) ~ ~ O o~
a~ a~
~:~
... . _
~ L- I I I I I ~ ~ -
P~
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o o o o oo U~
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'O O O O' O O ,'~
~ ~ ~ o o'
~: : ~i `~
C~l N C\l N N
:: : : ` :; :' ~.:
~`: :' -
~.D~I~/SdeR
-- ~.,
. ;, .
:
:
~o~
~otes on Table-~ 1, 2A and 2B
Cut tear o.r tear propagatio~ st.reng~h is
me;asured as descri.bed belol~ u~der (~I) in connecti.on
with ~ab:le 3r
Stiff~ess is measu.red by the following m~thod.
'.rhe method seek~ to represe~t the forces.
xe~uirea by the tendo~s of the foo-t to deform a
fold in a shoe vamp. Referri~g to ~igure 9, a
sample of material 50 which is 7 cm. long by 4.5 '~ -~
cm. wide is c:Lamped in a jig 51 with its outer or
topcoat sur:~ace, e.g., 13 bowed outwardly and a
length 529 53 of 20 cm~ from each e~d e~closed
within the clamp~ the ends within the clamp being
20 cm. apart so as to form an in~erted U~shaped ;~
trough~
~he jig is located in an Ins-tron tensile
testing machine and 15 cm. diameter metal rod 55 . '~
~ixed into -the cross head and lowered at a rate of '~
2.5 cm/min~te o~to ~he top 5~ of the inverted
U-shaped sample, -the rod bein~ parallel to the plane
bottom ends of the sample and perpe~dicular to the . ~ ~
longitudinal axis of the in~erted U~shaped txough .'~;`';,' .
(See Fi~ure 9). ~he stiffness is defined'as -the .
laod re~uired to make an inde7lta-tion ~.5 mm~. deep . '-
. ...
in the bottom of the inverted ~-shaped'sample. 25%
iti.al modulus and wa-ter vapour permeabil:it~ are -~.- '.
measured as descr;ibed below for '~able 3. .
WVP A is the value for the mal;erial before ;~
surface finishing,
WVP B is the ~alue for the material after
_ 33'~
' KD~/SdeR '~ :
~ 5~1916
surf~ce fini~hin~ he same surlace finishin~r
trea-tment is given to each sa~ple. It imparts
improved resistance -to p~netration by li~uid ~ -
water and to soilin~ and converts the sur~ace
from a dull matt finish to a lustrous deeper
coloured finish~ and imparts a grain appearance
to the treated surface, and confers upo~ th~
_ product a leatherlike break.
~he spraying is carried oùt as follows:- ~
1~.9 parts of a 31% solution of polyester ~ ;
polyurethane made as above (polyurethane 1~ is
thoroughly mixed with 7.1 parts of DMF and 0.4
parts o~ ~ perba black. 7.52 parts of the i~
resulting blend is mixed with 43.24 parts of ;~
additional ~M~ ~4.53 parts of c~clohexanone and
14.71 parts o~ acetone~ ~hi.s ~i~ture is spr~yed;~
onto the sheet material while hot air is supplied
fxom a fish-tcail, being directed against the sur~ace
of ~e sprayed sheet. ~he temperature of the air`~ ;~
measured two inches inside the ~ishtail is about
~- 110C. but after it leaves the fishtail it mixes
~;~ with the cooler ambie~t air so that the temperature
o~ the hot air blast just abo~e (e~g~, 1 inch above~
the surface of -the sheet is probably about 80C.
2~ In the spraying operation the solution is
atomised with air under pressure (80 psig~ in a
standard spray ~ m situated 12 inches above the
microporous sheet~
Just as it is leaving the sprc~y zone the
....
~ 30 sprayed sheet encoun-texs a blast of ho-t air directed
.
~D~ de~
.:'-' '' :'
~ . .. .
'
. '
~Q5~9~,
at its upper surface at a small angle (e.g., an
angle of some 15 so that the blast is almost
parallel to the upper surface of the sheet~ '~he
aix is supp]ied from a flatte~ed tube (a
'Eishtail') whose outlet is about 2 i~ches above
the sheet a~d about 1~ inches from the centre ot'
the spray gUll~ measured horizontally along the
path of the moving sheet, which is moving at 5
feet per minu-te. ~he hot air blas-t serves to
10 fuse the DMF-containing pol~ure-thane at the
surface of the sheet.
~he sheet -then passes through a hot air oven
(having an alr temperature~ in a fixst æone of
g3a. and in a second æone o:E 12la~ ) to drive of~
Yy ~ 15 residual ~MF: thè rssidence time in the oven is ~;
~- three minutes. ~he product has a black lustrous
bu-t fi~e~grained appearance li~e -that of smooth
fine black ~al~ Its thic~ness is about the same
~ as that of the original sheet. ~he increase in `~
- 20 dr~ weight is about 1 to 2 g~ams~s~. metre. `~
~ ~ All the eæamples have values after finishing
; of 50 or more and these values are all ~uite satis~
factory for shoe upper purposes since values as low `~
as 40 are ~uite suf~icient to produce comfortable
25 men's-shoes~
~ .:: .: .
Alt-ernative or additional fi~ishing processes
such as coat:ing~ printi~g and embossing ca~ also ~ ~
be emplo~ed~ ~ -
.. ..
: ': '
'
KD~ng/~deR -35~ ;
'
Density measurements in Tables 2A and 2B were obtained
by splitting the layers away from each other with a band knife
splitter and measuring the thickness and weighing the sample.
Example 32
A material was made in accordance with Example 1 using
as the topcoat and fleshcoat polymer polyurethane 3 and polyure*hane
1 as the substrate polymer.
The topcoat and fleshcoat formulations were as in Example
3. The substrate formulation contained 32.5% polymer by weight based
on polymer and solvent, 2 : 1 parts by weight of sodium chloride
based on polymer; the sodium chloride had an average particle si~e
of 40 microns as measured by Coulter counter.
The unfinished material was split on a band knife split-
ting machine and the properties of the separated topcoat, substrate
and fleshcoat layers measured. -
The topcoat and fleshcoat layers were microporous layers
about 0.35 mm. thick whilst the substrate was about 0.75 mm. I
thick. I
The tensile strength of the substrate was over three
~imes that of the stronger of the two other layers, namely, about
6 kg./cm., and its initial modulus over ten times that of the ;~
stronger of the two other layers, namely, about 1.5 kg./cm.? but
its elongation at break was of the same order as the values for - -~
the other two layers, namely, in the range 300 to 450%.
~;'' ''` ' ,' '
'' ~ "
- 36 - ~
~i(35l~g6
L~ 3
. ' ' - ._
EXA~LE lA 6A
-- .
Average salt part.icle - 2715(4) 50
siæe (B) - - - :~ ~
Posi-ti~e deviation ~10( ~17 . ,~ .
.;. Negative de~iation -lO( ) -17
. . S~l-t/resin ra~io (A) l.90:l 2.20
Dens~y (~) 0~45 . 4
.~ ~hickness (mm) ' l~ 40 1~ ~3
Weigh-t (g/sq.m) 652~5(2) 652,5(2? ;;
ear Prop~ga-tion (Hj l.83(l) : 2.~7(~
(Cut Tear) l,92(2) 2.50(2)
` ~ot ch tear (~) 4.l7~2) . ~. 45(2) ~;
:. . . - ~ear.Propaga-tion/ (z) 2 .
.' notch tear 46~o ` 56qot ) . - ~ -
ensile s~reng~h (D) -ll,9(2) l~.5(2)
Initial modulus (~) 2.3(2) . 2.3~2) - ;~
: W.Y.P. ~ (G) . l~0 .~ l25 ~-
i . . Porosity (M) 6~ 5~05
. Mean po~e (N~ 7,2 . lO
diameter.
., - - . ,. - .
- . .
., , . ... . . . - ... . . ~.
- ~ 37
.. - R~ K~saeR .
., . ... . . , . - . :
.. ': . - . ~.. :
........... ,. .. , . .. :.. : .,.. , ,. . . .. . , .. ,, ,. ; .,
~ 6
Notes on Tc~
(l) results uncorrected
(2) resull,s adjllsted to 1045 ~n~ thickness and
00l~5 gr/cc density.
(A) 'rhis is the ratio in parts by weight.
(B) '~hese valucs are measured by ~edimentometry.
This gives values in very close agreement to
those obtained by use o~ a Coulter counterO
~ 4) '~his is the average particle size.
(5) Th;s is the positive deviation.
~6) '~his is the negati~e deviation.
(C) grams pex cc. obt-ained b~ weighing a measured
a:rea of` the sheet product of measured `~
thicknessO , .,
(D) kg. per cm.
(E) At 25yo extention in kg. per cm~
~F) kg~
(G) Water vapour permeabilit~ in grams per s~. metre ~ -~
per hour at lOOyo relati~e humidity and 37C. ` -~
~D), (~ ), (G) and (~3 are measured b~ the ~ethods
set out in Belgian Patent 732~82.
(H) Cut tear or tear propagation is measured in `
kg. and the measurement is carried out on a
i ~ ~ tensile test machine o~ the constant rate of ~ -
`~ 25 - tra~erse type, e.g~, as described :;n Belgian ;
~; . ", . .
Pate~t 732~82, eOg~ ~ an Instron tensile testing
~ machine. 'rhe sample used i5 cut with a single
; ~ stroke of a press with a kni~e edged
rectan~ular punch having parallel long sides
75 mm~ long and parallel short sides ~5 mm. longD
2~ _
KI~ deR ~ ~
~5~ ~ 6
cu-t 20 mIQ. long is rnade in the specimen
wi~h a sharp knife running from the middle ~:
Or one short ed~e parEIll.cl to the long edges~
The jaws of the tensi.le machine are set 20
rnm. apart and one edge 22.5 mm. long is
gripped in one jaw and the other edge 22.5
mm. lo~g is grippcd in the other jaw. The
specimen;is sub~ected to an increasing load
by separating the j~ws at 10 cmO per mi.nute
un~il the specimen is torn along the cut.
~he cut tear stre~gth of the product is
defined as the average e~uilibriurn value of
the maximum load which is recorded~
(M) ~ irst -the apparent volurne of the
sample is determined b~ geometry~ ~he true ~- ~
volurne o~ solid i~ the sample is determined by ~ ~`
evacuation of the sample followed by intro~
duction o~ helium to atmospheric pressure and `~
the volume so int.roduced is measured~ ~he
dif~erence between the apparent and true
volume gives ~he t~al voi.d volume or porosi~y
. ~ ~
` (N) ~ - ~he term
~ . .
pore size or pore diameter used herein is the `;~
value ob-tairled b~ the following experimental
; method. Pore size in this sense is not t-he
maximum dimension o~ the voids in the material
but re~lects the dimensions of the holes or
pores in the walls surrounding or de~inirlg the
voids9 which holes provide intercommurlication
39
EDNK/SdeR
:1~5~196
betwecn the voids.
~he pressure re~uired to fo~ce mercury through ..
a pore is inve.rsely proportional ~o the pore
diameterO '~he volume of mercury forced ~hrough
the pore i~to the vold is e~ual to -the volume ,~
o~ the pore and the void. ~he porosit~ o~ a:'
sample is plotted a~ainst the pore size by' ~ ~ ",','
observation of the volume of mercury which can .,
'be forced into the sample from all sides at set ;~
pressures. ~he to-tal vold volume (see ~
above~ is composed of pores and larger voids
e~tered b~ such pores cover.ing the full range o~
pore diame-ters each of which re~uires ~ercu.ry at ,~
de~'ini-te pressu.res to :~ill it. By pre~setting ,~
the mercury pressures (P) the volume (V) of. ~`
. mercury forced in is determined ànd hence the .'.
.~ . ratio at that pressure of , '~ ~-
Vp . ` ~
20is determined. ~his is the porosity at that
~:~ ' , pore size~ ~ altering the mercury pressure
the porosity can be plotted as a function of .
~ pore diameter. ~his will level off at some
;` value which is the to-tal porosity of the samplet ~ :
~.
iOeO~ all pores ana voids are filled with mercury. .,' '
0.0~ micxons is considered as the lowest diameter. `'~:
~ - ~
he value so obtained is in very close agraement .
~` , to other'methods but has the advantage of
show.ing the rarlge o~ pore diameters. ~he poi.nt
~ of inflectio-n i~ the curve is taken as the mean
.. ., .~
KDN~SdeR
'c.
1 ~
',: -
~ ~S'~ 6pore d~ameter.
q'he initial pressure used was 5 psi absoluteO
Water vapour permeability is measurcd as
~ollows: ~ '
5~ h 3~ mm. high 70 mm. diameter jar wlth the top '' , ,
closed with a screw-on cap having a 60~5 mm.
diameter hole in it occupied by a 67.5 mm~ diametex
sample of the microporous material is used in an , ,
air~conditioned cabinet maintained at 37 flC. and `~
, !, ~ .
at zero relative hu~idity by mea~s of ~ilica gel. ~, ''
25 mm. of distilled water are placed within ` '',~
the jar and the change in weigJ,~t 'w' i~ a speci~ied ;,;~
~- i
time 't' measured 4 hours a~ter placing the àar in
the cabinet and again at least 5 hours later is
. :
recoxded. The water ~apour pe~neability 'wvp' ,'~
. . .
- 336.6 w grams per s~uare metre per,hour at 100% ~-
~, ~ t ,~-
H and ~7C. , ,-
~.
; , .
.,
., :
- . .. ~ ,
,:
^,
. :- . ~ , :
: ~ ,
,: -: - ~
41
K~ de~
:
., .
~.: `' ~ ~ ;-
~s~
~BL E` 4
. .
.
E{a~nple lA 61
D ~ ~ D
100 ~ 6.~ 6.~ 1 1.7 1.7
_ . _ - .
~ 7 . 9 1. '; 1. 6 2 .'1 1
5 0 5 rl 9 0 ~ ~ 6 2 . ~
~ _ . ..
~5 ~7 0.8 2 3.4 0.7
6 9.5 0.~ 3 'j.0 1.6 ~ - ~
, . .
l'j,~ 6 9 5 0 3.3 5.6 0.6
~0 6 12.7 3.2 30 50.4 ~4,8
G.~ 40.5 64.3 51.6 ~1.5 G9~8 19.
. _ ~' 97 7, ~3 13 . ~ 4 5 7 5 . 7 5 . 9
~ , . ~- .
3 . 2 55 B7 . 3 9 . 5 ~7 . 5 79 . 8 ~
. , ~- .,. -
' 2.0 ~j7 90.5 3.2 '~9 ~2.4 2.6 ;~
. .;;. , ~.
1. 6 j7 90 ~ 5 0 508~r ~ 7 ~ ;
___ . _. ~
- ~ 1.0 ~i~ 92 1.5 '~1 8~.7 1.6~, ., . ~_
0~3 59 9~7 1.7 51 ~5.7 0
. ~, . . . , _
0.75 59 93.7 0 52 ~37.~ 1.7 ~
~, : , , , .............. I ~ `
O.S 50 95 1.3 ~ 4~9 2.5
0.4 60 95 0 5~ 92.~ ~.5 ; ~ ~ -
. .. .~
0. 2 62 - 9~ ~3 97 .~ '5 .1 -
. . ~
0.1 62 9~ _ 59 99,2-1.7
0. 0~5 62 . ~ g8o 9 0 . 5 59 99 . 2 0 - ~ -
. . , . ~_~
0.05 63 1001.1 ~9 99.2 0
0 . 03~ 6 3 1000 ~ ~ 9 , I ~, ~ . O ~r~
42
- ~DNKfSdeR
: ,
~2~
~ble 4 ~ ;
Column A i~ the Yo porosity of the sample due
to pores greater than the value in microns given
in the lefthand colu~n. ~his includes both the
pores and the voids with l~hich the poxes
coolmullicate. ' :''
Column B is the /0 of -the total porosity which
the value on the same line in Column A represe~ts,
eag., for Example lA, 4yO o~ the poxosity is due to
por~s greater th~m 100 microns and this represents
G.4Yo of the total porosity of 63% of Example 1.
~oll~nn C is -the dif:~erence between the value -
. . .
on the line and the one in the line above for Column
~ B and thus represe~ th~ % o~ total porosity which
is due to pores belween the value i~ that line a~d
,
the one above, eOgO~ ~or EæamplelA, 1.5% of the
total porosity is due to pores which are grea~er ~ -
than 75 microns but not grea-ter than 100 microns. ;~
Considering ~able 3 in detail in Example lA,
..
~ 20 52% of the porosity is due to pores between 604 - `~
,~.
~ and 10 microns, 13.5% between 5.0 and 6~4, i.e~
,
: : 65.5/a between 5 and 10 microns and 9.5% between
; 3.2 and 5.0 microns, i.e., 75% between 3.2 and 10
microns; 6~.3% is between 500 and 17.5 microns; ;
?5 the average pore diameter is 7.2 microns.
or Example GA, 40% is between 12 a~d 1705
- microns~ 5~o is between 10 and 12 microns, iOe.~ 45%
between 10 and 17.5 microns ana 19% is between 6.4
. i ~ - . ~ .
~ and 10 microns, iOeO, ~o betwee~ 604 and 17.5
, ,
30 microns; 7001% is between 500 and 1?-5 microns;
. ~ 43 ~ :
- ED.l~JSdeR
,
.' ' ,
~0~
the average pore diameter is 10 microns.
The examples described above are made on a porous
polyethylene support.
One particular material suitable for use as the ~;
porous support which is both self supporting and has a ~ -
degree of flexibility and gives a very good flesh surface
appearance, is a porous liquid permeable sintered polymeric ~ -
plastics material especially one made from high density
polyethylene and preferably having an average pore size of
50 microns and more broadly 25 to 100 microns as measured
by the method described in B~S~So 1752: 1963 using n-propyl
alcohol.
The porous polyethylene ~or other suitable porous
support which may be a tensioned woven belt and can be made ~ ;
of polymer or metal or combinations thereof) is very
suitably one sold by Porvair Limited under the Trade Mark
Vyon (filter grade). ~ ~
This material is formed b~ spreading an even layer of `~ -
Ziegler high density polyethylene powder on a smooth metal
surface and then placing the smooth metal surface and the
layer in a suitably heated oven to cause the particles to
sinter. The s`urface of the resultant sintered sheet which
was in contact with the smooth metal surface is smoother
than the other face and it is on this smoother ace that the ~ ;
layer iS formed.
The porous support used in the Examples was a material -
of this sort having a permeability of 30 to 60 cu~ic feet -~
of air/minute at a pressure of 2n static water guage.
- ; . .
The material in accordance with the present invention
' ' ~ ' '
44
~S'Z~96 ~ ~
. -'
is preferably composed of elastomeric polyurethane and the
invention is illustrated by use of a :Linear polyester based
polyurethane of high elongation at br~c~k e.g. hundreds of
per cent such as at least 300%, 500% or 700%.
The substrate itself also has a high elongation at
break e.g. at least 200% and usually 300% to 500% or more.
However, many other polymers can be coagulated to
porous form from solvent, and solvent/non solvent systems `
and it is believed that such other polymers could be formed
into the novel product described herein. Further discussion
;~ of the polymer is given below. ;
The particular strength and wear characteristics
required for the end use of the man made leather like
material will determine the particular polymer formulation
to be used for the substrate layer.
For shoe uppers high abrasion resistance and tear `
strength combined -~ith a reasonable extensibility and
initial modulus to provide proper wear comfort on the foot
are required.
Many thermoplastic polymers can be used~ for such
purposes for example polyvinylchloride and its copolymers,
acrylonitrile polymers and copolymers and polyurethanes or
blends of one or more oP these. However we prefer elasto~
meric polyurethanes.
The elastomeric polyurethane may be used on its o~
or as blends with minor proportions say up to 49%
preferably less than 20% of poly~inyl chloride and other
polymers and copolymers such as nitrile rubbers including
solid copolymers of butadiene and acrylonitrile. 1
; ~45~
.... .. ..
~ O ~ 3
Other polymers which have been suggested for use in
man made leather like materials include polyacetal resins~
vinyl halide polymers (including copolymers with other
ethylenically unsaturated monomers), polyamides,
polyesteramides, polyesters~ polyvinyl butyral,
polyalphamethylstyrene, polyvinylidene chloride~ polymers
of alkyl esters of acrylic and methacrylic acids,
chlorosulphonated polyethylene, copolymers of bu~adienee
and acrylonitrile, cellulose esters and ethers, polystyrene
and other polymers made from monomers containing vinyl
groups, and blends of them with elastomeric polyurethanes
1~ can be used.
The preferred polymer however are!elastomeric
polyurethanes having recovery properties intermediate between
pure rubbers and pure thermoplastic materials at room
temperature.
The article by Schollenberger Scott and Moore in
~ubber Chemistry and Technology~ Yol. XX~V, No. 3, 1962 ~ ~
pages 742 to 752 at page 743 and in Figure 3 indicates the - ~ ;
long so-called half lives of the polyester urethanes made
from adipic acid, 1,4 butane diol and diphenyl methane ~
`i` p,p~ - diisocyanate by the methods disclosed in U.S. Patent
Specification NoO 2871218 and sold under the Trade Mark
ESTANE 5740. These two disclosures are incorporated herein
, " .
by reference.
Polyurethanes may be based on a wide variety of ~ ;;
precursors which may be reacted with a wide variety of
polyols and polyamines and polyisocyanates. As is well
known the particular properties of the resulting polyurethanes
_46-
'
1~5~
to a large exten$ can be tailored by suitable choice of the
reactants, reaction sequence and reaction conditions.
The preferred polymers are elastomeric polyurethanes
based on a linear~ hydroxyl terminated polyester ¦although
a polyether or a polyether/polyester blend may be used)
and a diisocyanate~ with a small addition of a difunctional
low molecular weight reactant. The last mentioned component
may be added either with the other reactants at the start
of a one-step polymerisation or at a later stage when it
will act primarily as a chain extender.
This type of polyurethane having thermoplastic
properties is particularly preferred for use in producing ~ `
sh~e uppers. Particularly preferred polyurethanes are
those derived from polyesters by reaction with diols and
diisocyanates. As is known from United States Patent ~ ~ -
Specification No. 2871218 men~ioned above many diffent
polyesters~ diols and diisocyanates can be used, but a
particularly suitable polyurethane system is one in which a
polyester made f~^om ethylene glycol and adipic acid is
reacted with 1,4 - butylene glycol and with 4,4~-diphenyl
methane diisocyanate. ~;
In the system in accordance with the above
specification the mole ratio of polyester and diol can vary
between quite wide limits but the combined mole ratio of
polyester and diol is arranged to be essentially equivalent
to the mole ratio of diisocyanate so that the resultant
polymer is essentially free of unreacted hydroxyl or
isocyanate groups.
Polymers of this type but having an improved Shore
hardness can be made by using a sli~ht excess of
diiosocyanate and also by using a copolyester as by replacing
part of the ethylene glycol in the above system by
1, -butylene glycol
A further alternative polyurethane system which has
been found particularly suitable~ uses polyester derived from
caprolactones. Such polyurethanes are described in British
Patent Specification No. 8596400
The polymers may be produced by a bulk polymerisation
process and subse~uently dissolved in suitable solvents or
may be prepared directly in solution by a solution `
polymerisation process.
The polymer can include conventional stabilizers, ;`
filler~,~ processing aids~ pigments, dyes additives and
surface active agents for example proofing or wetting agents,
,.
and when the polymer content is ~uoted in the claims this -~
includes any such additives which may replace up to 15% w/w
of the polymer. ;~
A particularly preferred polyurethane is that made by
the novel solution polymeri ation process disclosed in
United States Patent Specification Serial No. 3709864 ~`;
Belgian Patent No. 7424710 Such polyurethanes are charac~
terised by having intrinsic viscosities in the range 0.9
to 1.40
The intrinsic viscosity is determined in highly dilute
solution in analy~ical grade DMF which has been thorougly ;
dried by storage under a nitrogen atmosphere over a molecular
sleve (Linde 5A). Four measurements at 25 C corresponding to ~ ;
four~ approximately equally spaced~ concentrations are madè
-48-
~ .~, . . ~ - , . .. . .. . . .. . .. .. ..
and intrinsic viscosity and polymer solvent interaction
parameter are determined by the Huggins equation:
[~ ~ +
where ~ ~ is the specific viscosity and C is concentration
expressed in g/100 ml, and ~ is the intrinsic viscosity~
For usb in making shoe upper materials the preferred
polyurethanes have melting points of at least 100C
preferably above 150C (eOg. about 170 to 200 C~ as measured
by differential thermal analysis or differential scanning
calorimetry). When formed into a smooth void-free thin
film 0.2-0~4 mm in thiclcness (by carefully casting a degassed
solution in dimethylformamide and then carefully ~
evaporating off the solvent in a dry atmosphere) they -
.~:
; ~ have the properties described below; a tensile strength
of at least 210 kilograms per s~uare centimeter
(preferably at least 350 e.gO about 420 to 600) ~ -
a per cent elongation at break of at least 300% (pre~
ferably at least 400% e.g. about 500 or 700%3 a 100%
secant modulus ~stress divided by strain at 100% elong- ;~
~, ,, -.
ation of at least 28 kilograms per square centimeter
(preferably at least 84, e.g. about 110 to 134~o These
mechanical properties are measured by ASTM D882-67.
The preferred polyurethane (again tested as
a thin film made as described above) recovers completely
from a 5% elongation at room temperature (23C) but prefer4
ably does take on a permanent set (one measured for example j; -
as in an ASTM D412-66) after 100% elongation. This set is
usually within the range of about 5 to 20%~ as in the range
,
-49- I; ~ `
105~;:196
of about 10 to 20%, e.g. about 15~. The ~'permanent set~
is usually measured an hour after the release of stress;
for example, a material which shows a tension set of some ~ `~
24-26% immediately on release of the clamps after being
held at the 100% elongation for 10 minutes will ~ave a;iten~
sion set of 14% measured 1 hour after the release of the
clamps. (In the measurement a film specimen 1 cm wide with ``~
a gauge length of 5 cm is strained to the 100% elongation
at a rate of 254% per minute). Preferably the material for
the substrate layer haa a Shore hardness of at least 75A
(more p~eferably about 90A to 60D), measured by ASTM D vo6-67.
The use of polar organic solvents has been mentioned.
Many polar organic solvents could be used but DMF iS
preferred. ~ ~-
The particular solvent which is used can va~y
depending on the particular polymer composition non solrent
and removable filler which are being used. The solvent` "~
should not react with the other components oP the system
although it can form complexes with the non solvent e.g.
hydrates when the non solvent is water as lS believed to be ;~
the case with DMFo Also the solvent must be miscible with
the non solvent, preferably completely so, and must be able
: ,: , ~; ~ .,- :
to be extracted from the coagulated polymer. ~-
Solvents which could be used instead of DMF
include amides~ esters~ ketones~ sulphones~ and phenols~
however preferred alternatlve solvents to DMF are dimethyl
sulphoxide, N-methyl pyrrolidone, and dimethyl acetamide
and blends thereof with cheaper solvents such as toluene
and xylene which although not solvents for the poly~
_
urethane on their own do not act as non solvents when
mixed with dimethylformamide.
The non solvent to be used will also vary depending
on the particular polymer composition, solvent and removable :~
filler!which`~-are being used. Again the non solvent should
be chemically inert ~o the polymer and removable filler
though it may be a solvent for the removable filler and ~ ;
may form complexes with the solventO The non solvent should
be miscible with the solvent and should be a non solvent for
the polymer i.e. when added in excess to a solution of the
polymer it shoul~ coagulate the polymerO
Suitable inert non solvent liquid include methanol~
ethanol~ water~ hydrocarbons such as benzene~ toluene~ chlorinated ~ ~;
hydrocarbons, such as tetrachloroethylene and chloroform, polyol9
such as ethylene glycol~ glycerol~ and l~ trimethylolpropane
and glycol monoalkyl ethers and mixtures thereof which are ;~
mixible with the solventO However the preferred non solvent
is water since it presents no recovery problems and is far
cheaper than any of thealternatives;and moreover since it is
a very good solvent for tbe preferred removable fillers~ namely ;
inorganic salts such as sodium chloride, it can also be used ~`
as the non solvent for the actual coagulation step of the processO ;
The removable filler lS preferab-~y a water soluble
solid or a solid which can be dissolved by a non solvent ;~
compatible with the polymer. The removable filler could be
one~ e.g. a carbonate or bicarbonate~ which can be removed
by chemical action of the coagulating non solvent e.g. a `~ ~ -
. ~. :
dilute aqueous acid or by thermal decomposition e.g. ammonium
carbonate or bicarbonate but it should be chemically inert ~ ~ ;
-51-
during the actual coagulation stage to ensure that no gas
bubbles are produced in the coagulated microporous structure.
IYhilst such alternatives are possible they add complications `~
to the process and are not preferred. -
The preferred removable fillers are water soluble ~ -
inorganic salts e.g. the alkali metal and alkaline earth ~;
metal and ammonium salts e.g. chlorides and sulphates or
nitrates~ especially sodium and potassium chlorides and
sulphates and ammonium sulphate, sodium chloride being
,::
10 preferred on grounds of cheapness, relative solubilities~
and ease of availability
;. ~'
,',~
i` ~ "`'~ ', . ~: '
.: : . ,,
..
i, ,- ~ . -. ,,
,: .. ~ , ~ -
:. ::.: :
. ~ ~
; :^ , ~: :
- -52-
It has been mentioned above that the topcoat
and ~leshcoat layers are integrally adhered to the
substrate,
As car be seen from an inspection o~ the photo-
5 micrographs, this adherence is no-t produced by a more
dense layer at the lnterface between the layers but
rather the walls between the voids continue unmodified
apart from a change in wall thickness from one layer to
the other. This desirable highly permeable structure - ~ '
10. results from the preferred simultaneous coagulation'~
technique whereby all three l~yers are deposited prior
to any coag~lation and then the unitary structure is ;~
e~posed to the coagulant.
The topcoat, as mentioned above, is preferably
150 given a ~inishing treatment. The preferred form of this
treatment in~olves the formation of a thin densified
but still permeable zone at the outer sur~ace of the
~ topcoat layer. This densified layer is normally for
- grain leather-like products no-t more than 30 microns -thick
.~
; ~ 20. and is~usuall~ less than 20 micronB thick, eOg. 1 to 15 ;`~
or 3 to 10 microns thick.
The surface of -the material when finished by~ `
the technique described above has -the following general
characteristics when examined mi~roscopically. It has
250 a thin fused sur~ace la~er typically 1 to 15 microns
-' thick with fewer pores penetrating its surface than the
untreated material, i.e., less than abou~ 300 pores
¦ visible at 2GOx magniflcation i~ an area 360 microns
by 360 microns.
3- The'material typically has less than 200 pores~
, ~ .
, : -
, ~' KD~/FC0' -53- l ~
~'~7
~s~p~
e.g. not more than 100, e.g., 10 to 100, and mostly .`~
30 to 703 e.g., about 50 visible at 200x magnification
~ , -
in an area 430 microns by 430 micronsi~ mese pores
; are located in shallow craters typically 5 to 20, ~`
: -. .
` 5. e.g. 10 microns deep and 20 to 90, e.g. 50 microns
wide. The pores in the bottom of a crater typically `~
_ have a bridged appearance provlding access to a number
of pores in the interior of the material. The
pores which remain are typically 5 to 30, e.g., ahout
10. ~0 microns in diameter and are thus generally larger
than the pores in the unsprayed material~
- Each crater may contain a number of such pores
` typically 3, 5, 6, 8 or 10.
All the materials made by these techniques
75. have a ~ood grain break or crease pat~ern exhibiting
a fine pattern of creases at the line of the fold
~ . . - .
when the material is folded sharply with the topcoat
ii~ on the inside of the ~old.
t
r.'~
~ ', .. .
KDNK/FC0 -54~
' ,; , ' '~.
,
1~, . ~ ,,
'" ' ~
