Note: Descriptions are shown in the official language in which they were submitted.
6~
This invention is concerned with improvements
in and relating to rheological or flow control agents, i. e. additives
which modify the flow properties of surface coatings such as paints,
varnishes and printing inks, adhesives and laminating compositions.
.~; ' ~.
~ 8 The design and control of rheological properties is a
`~ most important aspect of the art of formulating surface coatings
such as paints, varnishes, and printing inks. In particular, the
formulator has resort to a number of devices for imparting and
~ , controlling specific patterns of non-Newtonian flow behaviour which
.; 10 may affect the behaviour of the surface coating before, during
` and after application. Means for imparting thixotropy or false-body
in various degrees constitute one of the most important groups of such ~ -
techniques. Thus it is well known that drying oils and alkyds (which
are widely usèd surface coatings media) may be modified by
reaction with poiyamide resins to provide thixotropic media which,
- inter alla, minimise pigment settlemerlt during storage, facilitate
application by brushing, and reduce the tendency of the applied
- film to sag. Other means of achieving these or combinations of
related effects comprise the use of the so-called flow control additives
. .: . .
which are mixed or milled into the surface coating at a later stage
,',: ~ ,
: of manufacture, for example after the varnish has been manufacturer,
i durmg pigmentation, or even after a paint has been pigmented. A
well known eæample of such a flow-control additive is finely powdered
hydrogenated castor oil. This has been used mainly in the so-called
; 25 decorative paints in which the principal solvent is white spirit, A
,
:' ~ '
.. . . ...
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. :., - .
major disadvantage of this material is its restricted useful
temperature range. Thus, in the manufacture of paints and the like
it is not uncommon for them to be subjected to temperatures in
excess of 60C. as, for example, during the process of ball milling
or high speed mixing. Under such c onditions hydrogenated castor
oil (HCO) tends to dissolve in the paint medium and to crystallise
out on subsequent cooling. The crystals so deposited are much
,j ~
- greater in size than the original micronised particles and are
substantially ineffective as rheological control agents. The effect
, . .
of the lICO is thus substantially reduced or even completely
lost. ~ further disadvantage is that the crystals may be visible
in the applied paint film giving rise to the defect known as seediness.
:
.: ~
Industrial paints of the kind normally dried by stoving
, ,
present a special problem because they normally contain relatively
powerful solvents such as xylol. The flow control additives of
the prior art are substantially ineffective in such systems. This
. : ~
is doubly unfortunate because there is a need to control the flow of the
paint in the applied film during the actual stoving operation. Thus one
wishes to avoid the tendency of the wet paint to run down vertical
surfaces of the painted object which is a particularly severe problem
..
during the stoving operation because of the reduction in viscosity
caused by the elevated temperature, The flow control additives of
.
, the prior art completely fail to do this at the typical stoving
temperatures of about 120 C.
, ..................................................... . .
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It has now been found, in accordance with the present
invention, that an improved rheological agent (e.g. one which may
be used at elevated temperature) may be obtained by modifying
,
HCO by blending it with certain oligomer?ic amides and using the
hlend, in finely divided form, as a paint additive. This is
.; .
-~ ~ surprising since HCO alone is intolerant of elevated temperatures
. . -
whilst the oligomeric amides alone are substantially ineffective
` as flow control agents. Decorative paints dlssolved in white spirit
and like substantially aliphatic solvents may be modified in such a way
that rheological control is exercised and seeding is avoided when the
~: :
- paint has been subjected to temperatures substantially higher than
. .~: -
those which could safely be used with HCO. It is further possible to modify
~` ~ industrial paints containing powerful solvents such as xyloI to such
a degree that flow control during stoving operationæ, typically at
. . ; ,
100 -120C is achieved.
.. ~ . .
The oIigomeric amides used in the agent of the invention
are those prepared by reaction of hydroxystearic acid with one or
., . . ~ .
more saturated aliphatic ~alpha-omega diprimary diamines containing -
2, , 6, 8 or lO carbon atoms together with one or more saturated
aliphatic alpha-omega dicarboxylic acids containing 2 - 12 carbon
:. . : : .
-,1 atoms and/or hydrogenated dimer acids, (i.e. acids obtained by
the hydrogenation of the acids obtained by the thermal dimerisation
j of unsaturated fatty acids). A preferred group of such acids
, s
comprises those containing 2, 4, 6, 8 or 10 or 12 carbon atoms.
. ~, , .
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Accorcling to the invention, therefore, theré
is provided a rheological or flow control agent comprising a blend in
- particulate form of hydrogenated castor oil and an oligomeric
amide derived from hydroxystearic acid, one or more saturated
~,; 5 aliphatic alpha-omega diprimary diamines containing 2, 4, 6, 8 or
10 carbon atoms and one or more saturated aliphatic alpha-
omega dicarboxylic acids containing from Z to 12 carbon atoms
and/or hydrogenated dimer acids.
".. ' i ' ' , ~ .
The oligomeric amides are prepared by reacting the
components together in known manner, typically by heating
under conditions of distillation of the evolved water at temperature
of about 200C.
!
~ Proportions of reactants are such that for each
. ~ i . .
mole of hydroxystearic acid there is present 0. 05 to 0, 5 moles of
dicarboxylic acid and a quantity of diamine such as to provide
0, 8 to 1,15 amine groups for each carboxyl group present in the
acid mixture. It is preferred to use 0, 95 to 1. 05 amine groups
. .
per carboxyl group since unreacted carboxyl or amine groups tend to
: .
~ diminish the flow-control properties of our products.
,
- It is not ~nece6sary for the hydroxystearic acid to be of
,, .
high purity: the crude material produced, for example, by the
:.~ .... . .
hydrolysis of HCO may be used, and this is a considerable
economic advantage, It is to be understood that functional
''
... .
. ,
3L1~ 9
derivatives of the reactants, capable of reacting to form the
oligomeric amides may be used in place of the acids and amines
themselves. For example, the methyl esters may be used in place
- of the acids, when the by-product of the reaction will bé methanol
~ 5 instead of water.
.: . . ,
The oligorneric amides are blended with HCO by
,
melting together in a weight ratio 9: 1 to 1: 9, preferàbly 4 :1 to
1: 4, the mixed melt is cooled and allowed to solidify, and the
powdered blend is finely powdered by means, for examplej of a
fluid energy mill or microniser. The powdered blend preferably has
; an average particle size of less than 25 microns and most~preferably
not more than 20% by weight of the powder, particularly not more than
10% by weight of the powder has a particle size above 25 microns.
The rheological control agents of the invention may be
lS used in a very wide variety of surface coating compositions, e.g. paints,
.,~ . .. .
varnishes, printmg mks, adheslves and laminating agents? based on a
- wlde variety of resin systems:such as acrylic resins, alkyd and modified
:: ........................................... . . . .
alkyd resins, oleoresins, epoxy resins, polyester resins and chlorinated
; rubbers. The surface coating composition will normally also contain
a solvent for the resin component, e. g. an aliphatic or aromatic
hydrocarbon such as white spirit, solvent naptha or xylene, an
~a fr.~ rf~)
~ aliphatic alcohol or ether such as butanol or a "Cellosolv~ or
ester thereof; or a phenol. It is not nececessary however that the
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coating system contains a solvent and thus9 for example, the
surface coating cornposition may be of the solventless type, e.g.
an epoxy resin/polyamide solventless coating composition or an
. ,
unsaturated polyester based laminating composition.
;:~
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The finely powdered blend is incorporated in the
' ' ' ' . -
surface coating composition in a known manner. A convenierrt
procedure consists in first preparing an approximate 15~o w¦w
dispersion of the powdered additive in an organic medium miscible
. , , - ,
with the surface coating medium to be modified. In the case of a
. :
decorative paint this will normally be white spirit. Dispersion of
~ the additive in the organic medium is effected by high speed stirring,~
.
- durirlg which a temperature of about 35 C will typically be attained,
and allowing the dispersion to cool overnight. This dispersion i~
; ~: - . ,
then added to the paint mill-base prior to grinding and the manufacture
of the paint is completed in the conventional manner.
, . , . -
.
.-. ~ . , - .
- The quantity of additive used depends on the precise
; composition of the additive, the degree of flow control desired and
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the conditions under which it is to be operative. For the flow
control of decorative paints a typical concentration of solid additive
would be about 0. 5% calculated on the resin content of the paint.
~, ,' .
Optimum selection of additive and of additive
, - :
` ~ 5 content may be carried out by simple routine tests well known in the
art. A typical procedure applicable to decorative paints will
.. ~ . -:
first be described.
,-;: ~ , .
The basis of the tests may be a sîmple white
~ ~ :
paint pigmented with titanium dioxide at a pigment:binder ratio ~-
of 0. 75:i. A suitable grade of titanium dioxide is Tioxide R-CR2
(Tioxide is a Regis~ered Trade Mark). A suitable binder is a long
oil linseed allyd such as Synolac S0W tSynolac is a Registered~
Trade Mark). The solvent is white spirit, and 0, 5% lead and
0. 05% cobalt, calculated orl alkyd solids, are incorporated in the form
o~their naphthenates as driers,
,;,. - : : _ ' ' ' ~
The pigment and an equal weight of medium are
, ~ , . .
., ;
incorporated to provide what is known in the art as the mill base.
: To this is ~added a quantlty of the 15% dispersion of the nOw control
additive such as to provide an additive concentration of, say,
,., , : .
20 0. 5% on the total al}~d resin solids of the finished paint. This mixture
=~ is ground on a single roll mill to a Hegmann (fineness of grind)
.,
, , .
gauge reading of 8~, blended with the remaining medium and adjusted
to a viscosity of 4 poises at 25 C. and 2500 sec 1 by addition of white
spirit.
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This procedure may be repeated at different concentrations
of additive and with different additives to find the optimum formulation
appropriate to a particular paint cornposition under given conditions,
~' "' ' .
The paints may be tested after they have been
; heated to different temperatures, e. g. 40, 80, 120, and subsequently
allowed to cool to room temperature for 24 hours, by being drawn
down using a Hegmann gauge to evaluate seediness. A Hegmann
reading below 6 indicates seeding at a deleterious level, Flow
control in terms of sag resistance may conveniently be assessed
by means of the well-known dye-line sag test, In this the paint is
sheared for about 5 minutes in a laboratory mixer to break down
, .
its structure and then quickly applied to a 12" x 4" glass plate
~: . ' , '
carrying on its surface a line of white spirit soluble dye
. ~ , .
parallel to the short side. The paint is applied as a wedge
lS film of wet thickness 0. 002" to 0, 006" by means of a wedge applicator and
the plate is then stood vertically. Any sagging of the paint is
.
indicate~d by a downward movement of the dye-line. An arbitrary
measure of sag resistance may be taken as the film thickness at
: ,
which a sag of 3mm below the original dye-line is observed. (The
- 20 higher the figure, the greater the sag-resistance),
.: .
-; The adaption of the forgoing test procedure to
industrial stoving paints will be obvious to those skilled in the art,
-, However, in these systems the dye-line sag resistance test is less
satisfactory because the powerful solvents present tend to cause blurring
.
... . .
~16~689 `
of the dye-line. A more satisfactory test, readily applicable to
the assessment of behaviour in the stoving oven, is the following.
The substrate is a steel panel 12" x 4" with a line of
1/4" diameter holes, 1" apart, drilled parallel to and 1" from
one of the long edges. With the panel in a horizontal position,
a wedge film of paint is applied, by spraying, ranging from 40 to
100 microns dry film thickness across the panel. The panel is
then rapidly placed in the stoviny oven in an upright position
with the row of holes uppermost. When stoving is complete sags
^: ~
or tears of varying length, increasing with film thickness,
depend from the holes. An arbitrary measure of sagging in the
stove may be taken as the film thickness measured in microns just
" helow a 1 cm. sag. A high figure denotes good sag resistance.
A typical paint system appropriate to this test pro~
I cedure and used in our evaluations is based on titanium dioxide! (supplied under the trademark"Runa RH472'~, aplasticising alkyd
: , .:. . .
resin (supplied under the trademark "Synolac 123X") and a butyl-
ated melamine formaldehyde resin (supplied under the trademark `
~1 . . .. .
"Beetle BE615"). The solids ratio of alkyd to melamine resin is
70:30 and the pigment:binder ratio is 0.8:1.
Again it is convenient to prepare a 15% dispersion of
the flow control additive but, with a paint solvent system largely
composed of xylol, xylol is used to prepare the dispersion. -~ -
i Addition is again conveniently made to the mill base before `~
grinding,
:
,,., . ~ .
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; '' .
, . . . ..
~64689
grinding is to a Hegmann gauge reading of 8+ but final thinning
is to a viscosity of 3 poises at 25C, 2500 sec 1 using a xylol-
butanol mixture corresponding approximately to the solvent
composition in the resin mixture. In the presence of such relatively
powerful solvents, and for flow control at the temperatures
encountered in stoving, higher levels of additive are normally
required and 1-4% by weight calculated on the resin solids
' content of the paint is typical. -
: , .
In order that the invention may be well understood
, .. :
the following preparations and Examples are given by way of
illustration only. ~ ~
` . 1: ': ~ '
Preparations 1 -15,
.
The oligomeric amides detailed in Table 1 were all
prepared by heating I mole of hydroxystearic acid with the designated
dicarboxylic acid and diamine in the molar proportions stated, at
... . .
200 C. under conditions of distillation of the liberated water for
about 4 hours or until the reaction was substantially complete as
,
indicated by measurement of acid value.
,, ,
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, .. . . .
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Oligomeric Dicarboxylic Dicarboxylic Diamine Diamine
amide No. acid acid moles molec :
Sebacic 0,1 Ethylene 0. 6 .. :
diamine ~ ~
.
2 Sebacic 0. 25 Ethylene 0. 75
dlamine ~ : ;
; 5 ` 3 Adipic 0. 25 Ethylene ~ 0, 75 ~- . diamine
' ~ 4 Suberic 0. 25 Ethylene 0. 75
:` diamine
:~ .
., Sebacic. : 0, 5 Ethylene 1. 0
diamine ~ -
.
. . .
. ~ : 6 Sebacic 0.1 Hexamethylene :
diamine ~ 0. 6
'~" Oxalic ~ 0. 5 ~ Ethylene 0. 75 -
diamme ~:
~' 10 : 8 Azelaic: ID. 5 :Ethylene 1. 0
diamine
9 : Succinic ~ 0.-1 ~ Ethylene ~ ~ 0. 6
dlamine~ :
: Hydrogenated ~ 0,1 Ethylene 0, 6
dlmer ~ ~ ~ diamine ~ ~
Hydrogenated : ~ 0. 25 Ethylene 0. 75 -~ ~:
dimer : ~ : diamine : ;
. `: 12 Dodecane di~ic 0. 05 Ethylene : 0. 55
diamine
,. . .
¢'~ ~ ~: 15 13 Dodecane dioic 0. 5 Ethylene 1. 0 ~ :
. ~ ~ . diamine
14 Sebacic 0. 1 1, 4 Diamino
,: ~ butane 0. 6 ~ ,
,: :
Glutaric 0.1 Ethylene 0, 6
diamine
.
,, ~ .
.
/ I . ,
.. . . . . .
~691 ~;85~
Examples 1 -15 oligomeric amide - MCO blends.
The oligomeric amides and HCO in the stated
proportions were heated together until just molten and well
mixed. The melt was allowed to cool and solidify. The solidified
mixture was broken up in a mortar and then comminuted by
treatment in a laboratory grinder. The grinding was less efficient ~-
than that which can be obtained in a microniser and the flow- ~ `
contro] effectiveness of the products was therefore below ~`
optimum. Even so, the products were found to be superior to the
micronised flow-control additives of the prior art (see following
sections) .
Typical blends are listed in Table 2.
! , ~
Blend No,Oligomeric Oiigomeric HCO Capillary mp of blend
~, amide No. amide wt. % wt. % C
1 1 '35 65 . 120-130
2 2 ; ~ 35 65` ~ ~ 170-190
.:
~ ~ 3 3 35 - 65 160-1~5 ~ ~
, -
' 165~215
,
9 ~ 35 65 , 123 130
6 15 35 65 125-143
7 10 35 65 112-125
8 12 35 65 ~ 125-135
g 13 35 65 205-235
14 35~ 65 160-175
11 1 10 ~0 114-170
~?~
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~L06468~
12 1 25 7S ) 128-170
13 1 35 65 ) 158-170
14 1 60 40 ) 158-170 -
(X 15 6 ;35 6i5 ) 143-155
: , ' ' ' ~ ' '
Effect of temperature on the dyeline sag resistance of
decorative paints modified with t flow control additives of the invention.)
,~ . .
'' ' ', ,
,/ The simple Tioxide R-CR2/Synolac 50W paint
.
described above was prepared using different powdered blends as
,
flow control additive at the level of 0. 5% on alkyd soIids. After
manufacture the paints were heated~to ~7arious temperatures to
simulate various degrees of overheating and allowed to mature
at room temperatur~e for 24 hours before testing ior sag resistance ;
by the dye-Ilne method described. Results in Table 4 are given as
wet film thickness in thou~ands of an mch~at which a 3 mm sag occurred.
., : ~ : ~
Blend No. Dyeline sag after heating to l ;
Room temp. ~ l20r,
2 0 - 2 2 C
(no heating~
1 2,5 3,2 3,5 2,7
2 ~ 3.0 3.7 4.3 3.0
. ~- .
3 2. 5 3. 0 4. 9 5. 9
4 2,5 3,0 3,5 4, g
2. 5 2, 9 2, 9 3. 3
6 3.0 3.4 3,1 3,7
7 . 2.5 2,5 2,9 2.8
l3
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... , , . '
~64f~
8 2.6 2.5 2,8 2.5
9 2,5 2.8 3,2 3,7
2.5 2.5 5.8 5.8
11 2.5 3.~ 6.0 6.0
12 2,6 3.5 6.~ 6.0
13 2.8 3.5 4.5 ~.0
14 3,0 4.0 3.3 3.7
- ~ 15 2.8 3,5 3,5 4,5
Control A 3. 0 3. 5 3, 0 2. 5
Control B 2, 5 3, 0 4. 4 2, 6
i Control C 2,5 2.5 2,5 2.5
(~ontrol A was HCO, micronised
Control B was a commercial product according to U. S, Patent
- No. 3, 203, 820 micronised
.
Control C was the original paint without llow control additive.
Eff~ct of temperature on seeding of decorative pa nts modified with `~
: ,
(flow control additives of the invention).
The paints were prepared, heated and matured as
described above. They were then drawn down on a Hegmann gauge,
Readings of 8 or higher (that of the original paint) were recorded ~ -
as "smooth", 6-8 as "slightly seedy", below 6 as "seedy".
Occasionally the action of the drawdown blade caused a further
film defect: the paint film was disrupted and became discontinuous.
In such cases the result "broken filrn" is recorded.
1~ '
, .......................... . .
~6~168~
.
TABLE 5.
.
Blend No, Condition of film on Hegmann
drawdown after heating to
F~oom temp. 40C 80C 120C
- 20-22 C
(no heating)
: 1 Smooth Smooth Smooth Smooth
: 2 Smooth Smooth Smooth Smooth
:
3 Smooth Smooth Smooth Smooth
:.
4 Smooth Smooth Smooth Smooth
Smooth Smooth Smooth Broken :
film.
6 : Smooth ~ Smooth ~ Smooth Smooth
7 Smooth Smooth ~ . Sl. seedy Sl. seedy
8 Smooth ~ ~ Smooth~ Smooth ~ Sl. seedy
9 Smooth : ~; Smooth: ~ Smooth Smooth
15: 10 Smooth~ : Smooth:: Smooth Smooth
Smootb ~~ Smooth~ Smootb Broke
12 : Smooth ~ ;: SmoothSmooth Smooth
13 ~ ~~ Smooth ~ ; Smooth : Smooth Smooth
, .
14 Smooth~ Smooth~ Smoath ~ Broken
Film
Smooth Smooth Smooth Smooth : :
Control A Smooth Smooth Seedy Seedy
~:
.~ Control B Smooth Smooth Broken Seedy
film
, . .
Control C Smooth Smooth Smooth Smooth
se of a typical additive in an industrial stoving paint,
The paint was prepared by the procedure described according to the
~,., ~, '.
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~6~1689
following formulation~ (parts by weight). ~-
Titanium dioxide (supplied under
the trademark Runa RH472)26.60
Plasticising alkyd in xylol
(Synolac 123) 46.65 :~
Butylated melamine-formaldehyde
; resin in n-butanol (supplied under
the trademark Beetle 615)16.60
15% dispersion of additive (Blend No. 2) 2.20
Xylol 4-75
n-butanol 3.20
10This was thinned to a viscosity of 3 poises at 25C.
2500 sec 1 using a mixture of 3 pbw xyIol and 1 pbw n-butanol. ~;~
The level of additive employed was 1% w/w on res~in solids.
Seeding tests were carried out in the aforesaid manner
against Control D and Control E with the following results.
(Control D contained 1% on resin solids o a commercial additive
according to U.S. Patent No. 3,203,820, micronised; Control E
.1 : '-
contained no additive).
; Additive Condition of film on Hegmann
~, drawdown after heating to ~
Room temp. 40C 80C 120C
- ~0 2~-22C
(no heating)
l Blend No. ;
?~ 2 Smooth Smooth Smooth Smooth -~
~, ;
Control D Smooth Smooth Seedy Seedy ;~ ~ ~
.,
Control E Smooth Smooth Smooth Smooth
1, ~no additive)
., . :,
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: .
.: :
'~ 30
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- 16 ~
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.
.
In the stoving te~t using the drilled steel panels, film
thicknesses measured just below a 1 cm sag were
Blend No. 2 80 microns : .
Control D 65 microns
Control E 50 microns
~::
The action of the additive of the invention and its
uperiority ov.er the products of the prior art is thus f~learly
.
S
demonstrat.ed~
, . .
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~64~9 -~:
Example 16
A thermosetting hydroxy acrylic coating composition is
prepared from titanium dio~ide (supplied under the trademark
"Runa" RH 472) ahydroxy acrylicresin (suppliedunder thetxademark
'!Synocryl" 823S) and a butylated melamine formaldehyde resin
(supplied under the trademark "seetle" BE 615). The solids
ratio of acrylic polymer to melamine resin is 4:1 and the pigment
binder ratio is 0.8:1Ø The paint is made up following the pro~
cedure outlined above for the plasticising alkyd resin composi- ~ ~;
tion bu-t using a 3:1 by weight xylol/butanol solvent blend as -
thinner. The Elow control additive (blend 2) is added as a 15~ -
dispersion in xylol. (1% by weight of the additive based on the
total solid resin content of the paint). Using the imprved test
described above the following results are obtained.
film thickness below a
1 cm sag
` Hydroxy acrylic paint with no flow
control additive 45-50
Hydroxy acrylic paint with flow control
additive 80-85
Example 17
A high ~uild chlorinated rubber finish was prepared
according to the following formulation:
.. ..
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., '~ .
'`';
~, .
;
- 18 -
~ ..
,
1~4~8~
Titanium dioxide (supplied under the trademark
(Runa RH 472) 12.6
Blanc Fixe 12.6
Chlorinated paraffin plasticiser (supplied
under the tr~demark Cereclor 42) 6.1
Chlorinated paraffin plasticiser (supplied
under the trademark Cereclor 70) 12.2
Chlorinated rubber (supplied under the trade-
mark Alloprene R10) 18.4
Xylol 28.8 ~
15% Dispersion of flow control additive (Blend ~ ;
`~ No. 2) in xylol 9.3
:~ 10
The paint was prepared by high speed stirring in the
course of which the temperature rose to 55C. This formulation
was compared with two others
! (i) halving the level of flow control additive
(ii) omitting the flow control additive ¦~
applying the coatings by brush to abraded steel panels at film
thicknesses of 4 thou. The panels were then stored vertically.
Sagging was assessed visuallyi the coating containing no additive ~ -
sagges badly at both 4 thou and 10 thou film thickness; the
remaining films showed no visual evidence of sagging at either
film thickness.
;:
. 30 i:
,, ` j~
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: . :, .
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1~64~
Example 1~
.,
Two laminating compositions were prepared from a
commercially available unsaturated polyester composition(Synolac
~; ~ 6 34 5) comprising 67% of an unsaturated polyester resin .
In the first composition 0. 5 parts by weight of a flow control
additive (Blend No. 2) was milled in 10 parts by weight of the unsaturated
polyester solution by high speed dispersion. During the course of this
mi2~ing the temperature rose to 40/45 C. This paste was then let down
with 90 parts by weight of unsaturated polyester solution.
:;~ ' ' ' ' -' ;~
A second composition was an unmodified aliquot of the
unsaturated polyester solution.
':,
,
- The viscosity of these two compositions was measured on ~
a Brookfield Viscometer model RVT using a number 2 spindle, at ~ ~-
25 C.
Sample with Sample without
additive additiv~_
Viscosity (spindle speed 5 rpm) 9. 2p 4. 0p
Viscosity (spindle speed 5 rpm) 4 . 2p 4, 05p
Thixotropic index (viscoslty at 5rpm) 2 19
(viscosity R t 50 rpm)
,
': :
The behaviour of these two compositions was exemplified
in a laminate of two layers of 1, 5OZ ft 2 at a reson to glass ratio of 2. 5: 1.
The sample with additive showed only slight signs of drainage in areas
,
.
~ o
"
,. .. .. .
4~61~9
.
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where resin excess at the surface; the sample without additive exhibited
severe drainage under similar conditions.
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