Process for producing porous polyurethane coatings using polyol ester additives
The invention relates to a process for producing a porous polyurethane coatings, using a polyol ester as additives in an aqueous polymer dispersion, the process comprising the steps of a) providing a mixture comprising an aqueous polymer dispersion, a polyol ester, and an additive, b) foaming the mixture to give a homogeneous, fine-cell foam, c) adding at least one thickener to establish the desired viscosity of the wet foam, d) applying a coating of the foamed polymer dispersion to a suitable carrier, e) drying the coating. The invention further relates to a phosphorylated polyol ester.
1. A process for producing a porous polyurethane coating, the process comprising the steps of:
a) providing a mixture comprising an aqueous polyurethane dispersions having a solids content of from 20 to 70% by weight, a concentration of polyglycerol ester in the aqueous polyurethane dispersion in the range of from 0.2-15% by weight based on the total weight of the aqueous polyurethane dispersion, and an additive;
wherein the polyglycerol ester is of general formula 1:
M a D b T c Formula 1
where
M=[C 3 H 5 (OR′) 2 O 1/2 ]
D=[C 3 H 5 (OR′) 1 O 2/2 ]
T=[C 3 H 5 O 3/2 ]
a=2 to 10,
b=0 to 10,
c=0 to 3,
wherein the R′ radicals are independently identical or different radicals of R″—C(O)— or H,
wherein R″ is a monovalent aliphatic saturated or unsaturated hydrocarbyl radical having from 3 to 39 carbon atoms,
wherein at least one R′ radical corresponds to a radical of R″—C(O)—;
b) foaming the mixture to give a cell foam;
c) adding at least one thickener to establish the desired viscosity of the wet foam;
d) applying a coating of the foamed polymer dispersion to a carrier;
e) after performing step d), and without any intervening steps, drying the coating,
wherein the porous polyurethane coating has a mean cell size less than 150 μm.
2. The process according to claim 1 , wherein
a=from 2 to 3,
b=from 1 to 4,
c=0,
where the R″ radicals are independently identical or different monovalent aliphatic saturated or unsaturated hydrocarbyl radicals having from 6 to 20 carbon atoms,
x=from 2 to 3,
y=from 1 to 4,
z=0,
k=from 2 to 3,
m=from 1 to 3; and
wherein the porous polyurethane coating has a mean cell size less than 120 μm.
3. The process according to Claim [[2111 1, wherein
a=2,
b=from 1 to 4,
c=0,
where the R″ radicals are independently identical or different monovalent aliphatic saturated or unsaturated hydrocarbyl radicals having from 8 to 18 carbon atoms,
x=2,
y=from 1 to 4,
z=0,
k=2,
m=from 1 to 3, and
wherein the porous polyurethane coating has a mean cell size less than 100 μm.
4. The process according to claim 1 ,
wherein the porous polyurethane coating has a mean cell size less than 100 μm.
5. The process according to claim 1 , wherein the polyglycerol ester is used in a blend with at least one ionic co-surfactant as additives in aqueous polymer dispersions,
wherein the ionic co-surfactants is selected from the group consisting of ammonium and alkali metal salts of fatty acids, alkyl sulphates, alkyl ether sulphates, alkylsulphonates, alkylbenzenesulphonates, alkyl phosphates, alkyl sulphosuccinates, alkyl sulphosuccinamates and alkyl sarcosinates,
wherein the proportion of ionic co-surfactant based on the total amount of polyglycerol ester plus co-surfactant is in the range of from 0.1-50% by weight.
6. The process according to claim 1 , wherein the aqueous polyurethane dispersions has a solids content in the range of from 25 to 65% by weight.
7. The process according to claim 1 , wherein the concentration of the polyglycerol ester in the aqueous polyurethane dispersion is in the range of from 0.4 to 10% by weight based on the total weight of the aqueous polyurethane dispersion.
8. The process according to claim 1 , wherein the polyglycerol ester serve as foaming aids or foam stabilizers for foaming of the aqueous polyurethane dispersions, and as a drying aid, levelling additive, wetting agent and/or rheology additive.
9. The process according to claim 1 , wherein the polyglycerol ester is selected from the group consisting of diglycerol, triglycerol, tetraglycerol, pentaglycerol, dierythritol, trierythritol, tetraerythritol, di(trimethylolpropane), tri(trimethylolpropane) and di- and oligosaccharides.
10. The process according to claim 1 , wherein the solids content of the aqueous polyurethane dispersions is in the range of from 25-65% by weight.
11. The process according to claim 1 , wherein said polyglycerol ester is of general formula 2:
M x D y T z Formula 2
wherein
M=
D=
T=
x=2 to 10,
y=0 to 10,
z=0 to 3,
wherein at least one R′ radical is not hydrogen.
12. The process according to claim 1 , wherein said polyglycerol ester is of general formula 3:
wherein
k=2 to 10,
m=0 to 10,
wherein at least one of the R′ radicals is a radical of R″—C(O), and that the sum of k +m is greater than zero.
13. The process according to claim 12 , wherein
a=from 2 to 3,
b=from 1 to 4,
c=0,
where the R″ radicals are independently identical or different monovalent aliphatic saturated or unsaturated hydrocarbyl radicals having from 6 to 20 carbon atoms,
x=from 2 to 3,
y=from 1 to 4,
z=0,
k=from 2 to 3,
m=from 1 to 3; and
wherein the porous polyurethane coating has a mean cell size less than 120 μm.
14. The process according to claim 12 , wherein
a=2,
b=from 1 to 4,
c=0,
where the R″ radicals are independently identical or different monovalent aliphatic saturated or unsaturated hydrocarbyl radicals having from 8 to 18 carbon atoms,
x=2,
y=from 1 to 4,
z=0,
k=2,
m=from 1 to 3, and
wherein the porous polyurethane coating has a mean cell size less than 100 μm.