AIRLESS SPRAY-COATING OF A SURFACE WITH AN AQUEOUS ARCHITECTURAL COATING COMPOSITION
A process for the airless spray-coating of a surface with a aqueous-containing Newtonian or non-Newtonian architectural coating composition wherein the composition can contain an associative thickener and is subjected to a pressure of from 2 to 5 bar generated such as by a hand-operated or battery operated electrical compressor and then sprayed from a slot-shaped outlet orifice ( 52 ) in a nozzle ( 50 ) to produce an outflow ( 31 ) of composition having boundaries ( 35 ) which diverge at least until it has formed a front of at least 30 mm in width. The composition preferably has a Brookfield viscosity of at least 0.5 pa.sec and a solids content of 7 wt %. Also apparatus for performing the process comprising a container containing the coating compositions together with a nozzle having an outlet orifice, a compressor and a pressure release valve actuatable in the pressure range 2 to 5 bar and preferably an auxiliary orifice upstream of the outlet orifice. The process and apparatus enable the viscous compositions to be applied quickly using low pressures easily generated by a hand compressor.
1 . A process for the airless spray-coating of a vertical surface with a viscous aqueous non-Newtonian architectural coating composition comprising a binder polymer and ingredients chosen from pigments, dyes, opacifiers and extenders which composition is suitable for coating vertical surfaces wherein
a) the composition contains a thickener and wherein the composition has a solids content of at least 7 wt %,
b) the composition is subjected to a pressure of from 2 to 5 bar and then sprayed from an outlet orifice ( 52 ) in a nozzle ( 50 ) to produce an outflow ( 31 ) of the coating composition, which outflow has non-convergent boundaries ( 35 ) at least until it has formed a front of not less than least 30 mm in width.
2 . A process according to claim 1 wherein the thickener comprises an associative thickener.
3 . A process for the airless spray-coating of a vertical surface with a viscous aqueous non-Newtonian architectural coating composition comprising a binder polymer and ingredients chosen from pigments, dyes, opacifiers and extenders which composition is suitable for coating vertical surfaces wherein
a) the composition contains an associative thickener and has a solids content of at least 7 wt %,
b) the composition is subjected to a pressure of from 2 to 5 bar and then sprayed from an outlet orifice ( 52 ) in a nozzle ( 50 ) to produce an essentially fat outflow ( 31 ) of the coating composition.
4 . A process according to claim 3 wherein the composition is passed through an auxiliary orifice ( 66 ) upstream of the outlet orifice.
5 . A process according to claim 3 wherein the composition has a Brookfield viscosity at 22° C. of at least 0.5 Pa.sec.
6 . A process according to claim 3 wherein the composition is sprayed from an outlet orifice which orifice is in the form of a slot.
7 . A process according to claim 6 wherein the slot is essentially elliptical or curtailed elliptical.
8 . A process according to claim 6 wherein the outflow takes the shape of an approximately parabolic fantail.
9 . A process according to claim 7 wherein the outflow takes the shape of an approximately parabolic fantail.
10 . A process according to claim 3 wherein the pressure is generated by a hand-operated compressor.
10 . A process accordingly to to claim 3 wherein the composition is passed through a plenum upstream of the outlet orifice.
11 . A process according to claim 10 wherein the plenum is cylindrical terminating in a hemispherical end ( 54 a ) into which a wedge shape comprising inclined planes ( 51 b ) notionally intrudes and defines the outlet orifice.
12 . Apparatus for the airless spray-coating of a surface with a viscous aqueous non-Newtonian architectural coating composition having a solids content of at least 7 wt %, wherein the apparatus comprises
a) a container containing a binder polymer, thickener and ingredients chosen from pigments, dyes, opacifiers and extenders
b) a nozzle ( 50 ) in communication with the container and comprising an outlet orifice ( 52 ),
c) a compressor capable of generating a pressure of from 2 to 5 bar and
d) a pressure release valve which releases pressure form the container in the range 2 to 5 bar
whereby generation of pressure enables composition from the container to be sprayed from the outlet orifice.
13 . Apparatus according to claim 12 wherein the apparatus comprises an auxiliary orifice ( 66 ) upstream of the outlet orifice and conduit means from the auxiliary orifice to the outlet orifice so that composition can be passed through the auxiliary orifice before being sprayed from the outlet orifice.
14 . Apparatus according to claim 12 wherein the outlet orifice comprises a slot ( 52 a ).
15 . Apparatus according to claim 14 wherein the shape of the slot is elliptical or curtailed elliptical.
16 . Apparatus according to claim 14 wherein the nozzle contains a plenum ( 54 ) upstream of the outlet orifice.
17 . Apparatus according to any one of claims 12 wherein the plenum terminates in a hemispherical end ( 54 a ) into which a wedge shape comprising opposed mutually inclined planes ( 51 b ) which notionally intrude into the hemispherical end and define the shape of the outlet orifice.
18 . Apparatus according to any one of claims 12 wherein the compressor is a hand-operated compressor.
19 . Apparatus as claimed in claim 12 wherein the compressor is a domestic appliance able to generate a pressure of from 2 to 5 bar.
20 . Apparatus as claimed in claims 12 in which the pressure generated is between 3.5 to 4.5 bar.