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Патент USA US2385560

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l’atented Sept. 25, 1945
2,385,560
UNITED STATES PATENT
oar-"ices
2,385,560
METHOD OF TESTING A PIGMENT
John K. Wise, Chicago, n1., assignor to United
States Gypsum ‘Company, Chicago, 111., a corporation of Illinois
No Drawing. Application June 16, 1941,
Serial No. 398,243
4 Claims. (01. 23-230)
The present invention relates. to an improved
forms of cellulose etherse-for example, methyl
type of coating composition, suitable for use as ~
cellulose, and the like.
a paint and the like, comprising a water-solu
It has been proposed in the past to manufac
ture water thinnable paints such as the well
known casein paints of commerce, which are
vble aminoplastic condensation product capable
of becoming insoluble in an acid-reacting medi
um, pigments nonreactive therewith, and a set
ting accelerator which comprises a compound
which is capable of hydrolyzing in the presence
\
available in dry powdered form as well as in
paste and liquid form, and the so-called resin
emulsion paints which. generally consist of a pro
of water to yield an acid-reacting solution,
tein solution in which a suitable type of alkyd
whereby the aminoplasticv condensation product 10 resin has been emulsi?ed.
will, upon evaporation of the water contained in
It is already well known that urea-formalde
the coating composition, becomes insoluble in
water so that the resulting coating composition
’ hyde condensation products can be prepared in
water-soluble form and dried to form more or
may, after a suitable period, be washed with wa
less coherent ?lms merely upon the evaporation
ter without becoming dissolved or dislodged from 15 of the water used to dissolve the condensation
the surface to which it has been applied.
product. Such ?lms, however, will again be
One of the primary objects of the invention
come dissolved or dispersed by water when it
therefore is to provide a coating composition
comes in contact therewith, so that'obviously no
which may be either in dry form or in the form
permanent paint could be produced thereby. It
vof a solution or paste and in which the binder is 20 is known that insolubilization of these amino
primarily an aminoplastic condensation product
plastic condensation products can be effected by
of the type which, while soluble in water in neu
rendering the solution slightly acid.
tral or slightly alkaline solutions, tends to become
This insolubilization'can be eifected by means
insoluble if the hydrogen-ion concentration of
either of an acid or of a substance, for instance
the solution is increased to a pH below 5. This 25 an ammonium salt, which su?iciently hydrolyzes
may be accomplished, for example, by the addi
to produce the required amount of free hydrogen
tion of either all-acid or an acid-reacting sub
ions in the solution. It has been found, how
stance or of a salt which upon hydrolysis will
ever, that there are certain limitations to the
yield free hydrogen ions. If this composition is
production of such a coating material, namely,
to be kept in liquid or paste form for any length 30 the necessity of carefully selecting the pigments
- of time, it becomes advisable to prevent the pre
which are associated therewith. In the first
mature insolubilization of the aminoplastic by
the expedient of incorporating with the composi
place, these pigments must be entirely nonreac
tive with the aminoplastic condensation prod
tion a small amount of a suitable volatile alkali
uct; but they must also be of such a nature
such as; for example, ammonium hydroxide, mor
that they will not interfere with the develop
pholine, or the like.
ment of acidity in the solution as a result of the
If such a composition is
applied to a given surface, the water as well as
presence of, or addition of, an accelerator capa
the volatile alkali will evaporate, whereafter the
ble of yielding hydrogen ions. Obviously, if the
hydrolysis of the accelerator will take place,
pigment reacts alkaline of itself or at least is
yielding free hydrogen ions which serve to in 40 capable of binding the hydrogen ions which are
solubilize the aminoplastic condensation prod
depended upon to-insolubilize the aminoplastic
uct.
,
condensation product, no such insolubilization
In its broadest aspects, the invention is par
can be effected. It therefore becomes necessary
ticularly applicable to the manufacture of what ‘
to select such pigments as will not interfere with
is known as water-thinnable paints, such as
the insolubilization of the material.
those which are designed for application to ma
In general it may be stated that suitable com
sonry, plaster, wood, fiber, or other porous sur
positions may comprise a water-soluble amino
faces, upon which the composition will dry to
plastic resin, some form of pigment such as, for
form a water resistant ?lm. Obviously, in or
example, various types of lithopone, titanium ox
der to impart the desired hiding power and color 50 ide, antimony oxide and the like, and a small
ing power to the material, suitable pigments and
quantity of an ammonium salt of a strong acid.
, fillers are also admixed therewith.
Suitable for this purpose are ammonium chloride,
It is also within the scope of the invention to
ammonium sulfate, and ammonium nitrate.
add other ?lm-forming substances, such as, for
In order to determine what pigments will be
example,
water-soluble
gums,
water-soluble
55 suitable for this purpose. the following test may
2,
2,386,580’
be used: 20 grams of the pigment or ?ller which
is to be used in the paint is suspended in 50 c. c.
of distilled water containing either 5 c. o, of 4%
materials may be added as further binders, par
ticularly to improve the resistance of the coat
ing to crazing or check cracking.
-
Among the aminoplastic condensation products
formalin or 14 gramsof a water-soluble urea
formaldehyde resin, and the hydrogen-ion con
are to be‘included the well-known types of urea
centration of the thus formed suspension (that
aldehyde condensation products, such for exam- '_
is, its pH) is measured by a suitable method-for
ple as urea-formaldehyde condensation products,
example, by means of a glass electrode and there
thiourea aldehyde and formaldehyde. condensa
with associated electronic devices. The suspen
tion products, substituted thiourea aldehyde con
sion should preferably be close to neutrality, hav 10 densation products, and the like, provided they
ing a pH of, say, from 6 to 7. An ammonium
are capable of insolubilization in the cold in an
chloride solution of known concentration is then
acid environment. By the term “urea-aldehyde
gradually added to the suspension, using for this
condensation produc ” it‘is intended to cover all
purpose a su?icient amount of ‘ammonium chlo
of these urea-aldehyde condensation products
ride to be equivalent to about 5% of ammonium
considered as a genus. This term has been ap
chloride on the basis of the suspended pigment
plied to these materials for some years past, and
it is generally understood among chemists as
meaning the condensation products of urea or
carbamide and analogous compounds. For most
or ?ller. The hydrogen-ion concentration of the
solution should thereupon increase to the extent
that the pH thereof drops, say, down to some
where between 4 and 5. If the pigment will pre
purposes the simple urea-aldehyde condensation
vent the development of the acidity-that is, the
product is suitable. This is now a commercially
decrease in the pH-such pigment will be un
suitable for the purposes of the present invention.
It has also been discovered that the degree of
development .of acidity, by for example an am
monium salt, can be somewhatincreased by the
presence in the ?nished product-that is, the
paint-of a very small amount of free formalde
available product that may be freely purchased
on the open market.
As actual examples of compositions which may
be made within the scope of the presentinven
tion may be mentioned the following:
Example 1
Parts by weight
hyde, this being particularly true in the presence
of pigments.
~
If the composition of the present invention is
Urea formaldehyde resin (water soluble) _..__ 392
30 Concentrated ammonium hydroxide ______ __
to be made up into paste form so that it may be
sold in cans, ready for dilution by the user, two
expedients may be employed to keep the mate
rial from becoming insoluble in the can. The ?rst
expedient is to keep the accelerator out of the
composition and to furnish it in a separate con
tainer so that it may be added to the paste by
the user Just prior to application to the surface
that is to be painted. The second expedient, and
the one which is preferred, is to add to the paste
a small amount of a volatile alkali such as am
25
Pigment, e. g., antimony oxide ____________ __ 400
Mica _
40
Clay
360
Ammonium chloride ___; ________________ __
Water
3'
16
385
Example 2
Parts by weight
Urea formaldehyde resin (water soluble) _____ 14
Pigment, such as lithopone or other zinc sul
?de pigment __________________________ __ 46
Water
25
monium hydroxide, or morpholine, whereafter
Ammonium chloride _____________________ __ 3
the accelerator material is added. Usually this
Both of these formulas are for stiff pastes.
is an ammonium salt, preferably ammonium chlo 45
However,
the second formula may be made up
ride. It is, of course, obvious that a small amount
in dry form merely by omitting the water and
of sodium hydroxide could be employed together
may be employed by the user by stirring the mix
with the ammonium salt so as to liberate a small
ture into water until it is dissolved. If it is de
quantity of ammonia. In any event, the purpose
sired to preserve the second composition for any
is to keep the composition substantially neutral
while in the can, before use. What happens when 50 length of time, it is desirable to add su?lcient
ammonium hydroxide thereto to render it faintly
such a composition is applied to the surface to
alkaline.
be coated is substantially as follows: The water
In the above formulas, equivalent amounts of
evaporates, carrying with it the still more vola
thiourea-aldehyde condensation products may be
tile ammonia which is evolved from the am
monium hydroxide, so that at about the time the 55 substituted, and it is also possible to use dicy
andiamid condensation products in lieu thereof.
composition is nearly dry practically all the am
However, as the ordinary urea-formaldehyde con
monia has escaped. Thereafter, the residual am
densation products are the least expensive of this
monium salt will hydrolyze, yielding. free hydro
group, they are generally preferred.
gen ions which then will effect the desired insolu-.
While all pigments are not necessarily adapted
60
bilization of the aminoplastic condensation prod
uct. If desired, a small amount of free formal
dehyde may also be present in the solution or
paste, as already indicated hereinabove.
The pigments, coloring matter, ?llers, and the
like may be added to an aqueous dispersion or 65
solution of the aminoplastic condensation prod
uct, or all of the ingredients may be introduced
either conjointly or individually into the water,
for use in connection with the coating composition
of the present invention, their adaptability can
readily be determined in'accordance with the tests
hereinabove outlined.
The methods of mixing and the proportions of
?llers and pigments are, of course, capable of
wide variation, depending upon the color and hid
ing power of the paint and also whether it is
to be used as a ?nal coating or an initial or prim
whereafter the mixture may be agitated, as in
ing composition.
70
a mixing kettle Or the like, to obtain a uniform
Saving for himself such modi?cations as fall
mixture therewith. A very advantageous pro
within the scope of the art to which this inven
cedure is to follow the mixing by running the
tion appertains, applicant claims:
paint through an ordinary paint mill in order to
1. Process of determining the suitability of a
remove lumps and undispersed particles. Other 75 pigment
for use in a coating composition con
2,886,660
taining a water-soluble urea-formaldehyde con
densation product capable of becoming water-in
soluble in an acid-reacting medium which process
comprises suspending a quantity ofv said pigment
in an aqueous solution of a substance capable of
3
consisting of the chloride,'sulphate and nitrate,
and after a short interval of time measuring the
hydrogen-ion concentration of the suspension to
determine whether it will be within the range of
about pH 4 to pH 5; failure to attain such a de
gree of acidity being indicative of the unsuit
ability of the pigment because of its interference
with the development of suiilclent acidity to effect
the desired hardening of the said condensation
furnishing free formaldehyde thereto, adding
about 5% by weight (as calculated on the dry
weight of said pigment) of a salt of ammonium
capable of liberating free strong mineral acid, 10 product.
said salt being selected from the group consist
3. The process of claim 2 in which the ammoni
ing of ammonium chloride, ammonium sulphate
um salt is the chloride.
and ammonium nitrate, and measuring the hy
4. Process of testing a pigment as to its suit
drogen-ion concentration of the suspension;
ability for use in a urea-formaldehyde coating‘
whereby if the hydrogen-ion concentration of
composition which comprises suspending the pig
the suspension falls within the range of about
ment in the relative proportions of about 20 parts
pH 4 and pH 5, the suitability of the pigment
by weight thereof in about 50 parts by weight
for the intended use is established.
0! water containing about 5 parts of a 4% for
2. Process of testing a pigment for its poten
malin solution, adding about 1 part by weight
tial property of interfering with the hardening 20 of ammonium ‘chloride, and measuring the hydro
of aqueous solutions of urea-formaldehyde con
gen-ion concentration of the resulting mixture,
densation products by the development of acidity
which, if it falls within the range of about pH 4
therein which comprises suspending the pigment
to about pH 5, indicates the suitability of the
that it to be tested in an aqueous solution con
taining formaldehyde, adding an acid-yielding 25
ammonium salt thereto selected from the group
pigment.
JOHN K. WISE.
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