Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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This invention relates to thickened solutions of film
forming polymers t especially to thickened adhesive
compositions.
Solutions o film forming polymers are widely used as adhesives
and lacquers. They can be applied by the use of a
spreading device to spread a portion of the solution in a
thin film over a surface or they can be applied by extrusion
from a collapsible tube or from a bottle with a rubber
application orifice or the like. However, the standard
liquid adhesive and lacquer compositions have a number of
disadvan.ages, principally a tendency to run when applied
to inclined or vertical surfaces, and a tendency to "tail".
ITailing'' is the name given to the tendency of the liquid
adhesive or lacquer compositions to form strands or "tails"
~etween the work surface and the application device, whether
~t be a hand held spreader, a tube or a bottle, as the
device is removed from the work surface after appllcation
of the adhesive. "Tailing" is undesirable because it makes
neat application, (essential for model work and many small-
scale domestic uses) very difficult.
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This in~rention is based on the discovery that standard
liquid adhesive and lacquer compositions can be improved~
the ~endency to run and "tail" being reduced, by
i incorpoxa-ting a thickening or gelling ayent in the
' composition.
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Although thickening and gelling agents are commonly used in
many areas of industry, the adhesives and lacquer industry
is peculiar in that its range o solvents tend to be medium
polar solvents such as methylacetate, ethylacetate, butyl-
acetate, acetone, methylethylketone and methylisobutylketone.
The standard thickening and gelling agents for highly polar
solvents like water and for non-polar hydrocarbon solvents
are generally unsuitable for use with medium polar solvents.
However, we have discovered that the addition of an al]cali
metal salt of a C8_36(preferably C12_22~ y
ferably as a solution in a lower aliphatic alcohol (e.g.
methanol or ethanol), to standard liquid lacquer and adhesive
; compositions (e.g. to about 5-50% by weight of the total
composition) produces a thickened composition which has a
reduced tendency to run and "tail".
Accordingly, the present invention provides a method of
thickening a solution of a film-forming polymer material
in a solvent of dielectric constant in the range 570 to
50.0, comprising mixing with said solution at a temperature
above room temperature, an alkali metal salt of a C8 36
fatty acid and allowing the mixture to cool without sub-
stantial agitation. The invention provides also a film
forming composition produced by this mekhod.
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The degree of thickening achieved will naturally be related
to the concentration of fatty acid salt (:hereinafter called
"the soap") added.
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In ~encral the soap may comprise from 0.05 to 5~ by weight
of the total thickened composition.
The soap is pre~erably an alkali metal salt o~ a C12 22
fatty acid, most preferably a sodium salt. Sodium stearate
is a preferred soap.
.
Preferably the soap is mixed with the solution o~ the film-
forming polymer as a solution in a lower aliphatic alcohol,
especially methancl or ethanol. The temperature at which
the alcoholic soap solution is mixed with the so]ution o~
film-formex may be in the range 30C-80C depending on the
volatility of the sol~ents used. It m~y sometimes be
pos~ible to form the soap in situ by neutralising an added
fatty acid.
The solvent of a dielectric constant in the range 5.0 to
50.0 may be selected from the standard medium polarity
solvents used in the past for adhesive and lacquer
compositions, usually low molecular wei~ht esters and
ketones and mixtures thereof, sometimes with small amounts
of lo~er alcohols. E~amples of sllch solvents include
methylacetate, ethylacetate, butylacetata~ dibutylphthalate,
cyclohexanone, acetone, methylethylketone and methylisobutyl
ketone. Methyl and ethyl alcohol may be mixed in ~ninor
proportions with these ester and ketone solvents. The solvent
is usually a blend of individual solvents, chosen to gi-re
the desired rate of evaporation. Normal3y the dielectric
constant will be in ihe range 5.0 to 30.0, e.g. 10.0 to 25Ø
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The film-forming polymer material may be any of those used
in the past for adhesive and lacquer compositions, for
example, polyvinyl acetate, po:Lyv:Lnyl alcohol, polyvinyl
chloride, polyurethane, polyacrylate or polymethacrylate or
their esters/ polyvinylpyrrolidone, or copolymers of these
materials, as well as cellulose nitrate, cellulose ethers
and esters.
If desired, small amounts of water may be included in the
compositions of this invention, eirher as part of normal
moisture content of the organic solvents or as added
water. The water gives the thickened or gelled composition
an attractive translucent-appearance.
Although the compositions of this invention are generally
satisfactory in that they have a reduced tendency to run and
tail, we have found that with some film-forming agents, e.g.
polyvinylace~ate, especially in compositions containing
water, ~he stability cï the total thic]ened or gelled
composition is rather less than that o the same composition
without the soap or water and that occasionally metal surface
adhesion properties may be worse. However, we find that in
instanc~s where the stability is u~satisfactory, the adc~ition
of buffers o keep the pH of the composition in the range
fxom a~out 7.0 to about 9.0 ~preferably inorganic salts
~e.g. sodium salts) of weak oraanic or inorganic acids, as
or exa~lple sodium tetraborale (borax), sodium acetate,
sodium-p-hydroxybenzoicacid methylester, sodium iodate;
sodium formate and sodium succinatej,in an amount of fxom
0005~ to 20% b~ wei~ht o the whole composition ~depending
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on the pH required) restores stability with little or no
adverse e~ect on the adhesi.ve or lacquering properties
of the composition. The bu~fer substance m~y be incorporated
in the solution as a saturated solution in water, alcohol,
or other solvents. At the same time we surprisingly find
that these bufer additives, e.g. borax, sodium acetate,
sodium-p-hydroxy-benzoicacid methylester, also tend to
improve the metal surface adhesion of the composition.
i The buffer substances also appear to ir.crease the gelliny
, temperature of the co~positions of this invention (possibly
I due to a "salting out" effect which reduces the solubility
of the gelling agent ln its colloidal form). This increase
in gelling temperature may also partly explain the
stabi].ising effect of the buffers.
I, , .
~ ~ Hence, according to a preferred embodiment of the invention
,~ : there is provided a method of thickening a solution of a
~` film-forming polymer materi.al in a solvent of dielectric
constant in the range 5.0 to 50.0 contprising mi~lng with
said solution a buffer substance in an amount to ~ontrol the
final pH of the total composition within the range 7.0 to
9.0 and an alkali metal salt of a C~ 36 fatty acid,
preferably in al.coholic solution, said fatty acid salt being
mixed with the solution of film.forming agent at a
temperature above room temperature, and allowing the mixture
to cool without substantial agitation.
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The ~uffer substance is prefexab].y added in an amount
of from 0.05~ to 20~ by welght of the whole compos:ltlon
to control the pH at about 8Ø It may be added beore,
after or together with an alcohol solution of fatty
acid sall~ The temperature at which the bu~fer is added
;.s preferably at or above room temperature, and it may be
added as an aqueous solution or in some cases may be formed
i.n_situ by the addition of a weak inorganic or organic
acid followed by neutralisation e.g. with sodium hydroxide.
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The following Examples illustrate the invention:
EXAMPLE 1
Plexigum MB 319 30 ~ by wei.ght
~a trade mark of Messrs. Rohm
Darmstadt) a copolymerisate of
polymethylmethacrylate and
polyethylacrylate)
Methylacetat.e 45 % by weight
Etbyl alcohol 24.7 % by weight
Sodium st;earate , _ .3 ~ by we.i~ht
100.0 % by weight
Procedul-e:
~ix th~ methy~acetate and ethyl alcohol in a vessel fitted
with reflux condenser and add the Plexig~ with stirring
at room temperature. After about 1 hour the solution will
be homoyeneous.
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Now, ad~ the sodium stearate and continue s-tirring ~or
about 15 minutes at room temperature. Ileat to 60C and
stir (about 5 minutes) until the composition appears
homogeneous. The finished batch is p~nped into containers
and the resultant mix allowed to coo]..
EXAMPLE 2
Polyvinyl acetate with ~ Mol. 38~ by weight
weight of 130,000
Methyl alcohol 10% by weigh1:
Methyl acetate 30% by weic3hJ~
Ethyl alcohol 19.75 % by weigllt
Sodium stearate 0.25 % by weight
5% solution of borax in water 2~ gh~
100.00 % by wei.ght
Procedure:
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Mix the methyl acetate and ethyl alcohol in a vessel
fitted with ~ reflux condenser. Add the polyviny].
acetate with stirring. After aboui 2.5 hours when the
solution seems to oe homocJeneous, add the sodium stearate
as a heate~ solution in the methyl alcohol and continue
stirring for about 15 minutes until it is dispersed. Therl
heat the whole mixture to about 50C and add the 5~ solution
of borax in water. Allow the resultant ~.ix to cool.
EX~MPLE 3
Linear linked po].yureth~n2 20~ by weight
Alkylphenol resin (~,~resen*PA104) 10 % hy weicJIlt
Methylethylketone 40~ hy wei.c3h~
* Trade Mark
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s~
Ethanol 29.7 ~ by weight
Sodium stearate 0.3 _ ~ by~
; 100.0 ~ by weight
Procedure-
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Fill the methylethylketone into a vessel fitted wi.th a
reflux condenser; add the linear linked polyurethane with
stirring. After about 2.5 hours when the solution seems
to be homogeneous add the alkylphenol resin and continue
stirring for ~ hour. Then add the hot solution (50C) of
sodium stearate in ethanol slowly under stirring and heat
the whole mixture to about 60C. After reaching a full.y
homogeneous solution allow the resul~ant mix to cool.
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