Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2000-03-27
2002-03-26
Niland, Patrick D. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S457000, C524S507000, C524S839000, C524S840000, C525S123000, C525S127000, C525S455000
Reexamination Certificate
active
06362273
ABSTRACT:
The present invention relates to certain aqueous polymer dispersions containing a polyurethane polymer and a vinyl polymer.
Aqueous polyurethane dispersions which are used as or provide the basis of aqueous-based coating compositions are well known for the production of coatings on various substrates. They may be used for the provision of e.g. protective or decorative coatings since polyurethanes, depending on their particular composition, can possess many desirable properties such as good chemical resistance, water-resistance, solvent resistance, toughness, abrasion-resistance, substrate adhesion and durability. Dispersion of the polyurethane in the aqueous system has been achieved either by the use of external surfactants or, more usefully, by including appropriate chain-pendant ionic and/or nonionic groups in the structure of the polyurethane polymer. In the latter respect, such aqueous polyurethane dispersions are particularly advantageously prepared (as is by now well-known in the art) by dispersing an isocyanate-terminated polyurethane prepolymer bearing ionic and/or nonionic dispersing groups into an aqueous medium and reacting the prepolymer with an active hydrogen-containing chain extender during and/or after dispersion in the aqueous medium. In an alternative well known process, known as the “acetone” process, the prepolymer is chain-extended while dissolved in an organic solvent (usually acetone) followed by the addition of water until water becomes the continuous phase and the subsequent removal of the solvent.
It is also now well known to modify the properties of polyurethane coatings derived from aqueous dispersions thereof by incorporating vinyl polymers, and in particular acrylic polymers, into the dispersions. For example, the use of acrylic polymers may allow upgrading of the coatings by increasing their hardness. Such dispersions may include the polyurethane and vinyl polymers as a simple blend of the preformed polymer dispersions. However, several patents, for example U.S. Pat. Nos. 3,705,164, 4,198,330 and 4,318,833, EP 0189945 and EP 0308115, describe processes where the vinyl polymer is formed in situ by polymerising one or more vinyl monomers in the presence of an aqueous dispersion of a polyurethane containing anionic salt groups. Such in-situ formation of the vinyl polymer can be advantageous in that it may result in greater dispersion stability and may further improve the performance of the resulting coating in comparison to simple blending of the polyurethane and vinyl polymers.
We have now discovered certain of these aqueous polyurethane/vinyl polymer dispersions (the vinyl polymer being incorporated as a simple blend or being present as a preformed polymer when the polyurethane prepolymer is chain extended, or more preferably being formed in-situ) which provide coatings of exceptionally good block resistance and exceptionally good imprint resistance. This is especially advantageous in many wood and board (i.e. compressed and glued wood particles or fibres) coating applications, for which the invention aqueous polymer dispersions are particularly useful, where the avoidance of coated substrates tending to stick together (i.e. block), as e.g. in coated window and door frames or in stacked coated boards (during storage), is highly desirable. In addition, the invention polymer dispersions provide coatings having good resistance to many chemicals and solvents including e.g. household chemicals. Still further, the urethane component of the dispersions, which are of relatively high acid value (see following), may significantly depress the minimum film forming temperatures (MFT) of high Tg vinyl polymers which may be used in the dispersion, without reducing the hardness. Also, the in situ prepared urethane/vinyl polymer dispersions show a favourable hardness/MFT balance.
According to the present invention there is provided an aqueous polymer dispersion containing a water-dispersed polyurethane polymer and a vinyl polymer in a weight ratio of from 30/70 to 5/95 wherein said polyurethane polymer is the reaction product of:
A) an isocyanate-terminated polyurethane prepolymer having an acid value of ≧44 mg KOH/g of prepolymer (solids) and formed from reactants comprising an organic polyisocyanate component and an organic poly(isocyanate-reactive group) component in which the isocyanate-reactive groups are selected from —OH and optionally one or more of —NH
2
, —NH—, and —SH, wherein
i) at least 70 weight % of said polyisocyanate component is constituted by at least one aliphatic polyisocyanate,
ii) said poly(isocyanate-reactive group) component includes at least one acid-bearing poly(isocyanate-reactive group) compound for providing anionic groups which provide or contribute to water-dispersibility,
iii) the reactants are used in amounts corresponding to a ratio of isocyanate groups to isocyanate-reactive groups within the range of 1.4/1 to 2.9/1; and
B) an active hydrogen chain-extending compound(s).
There is further provided according to the invention a process for the production of an aqueous polymer dispersion containing a water-dispersed polyurethane polymer and a vinyl polymer, wherein said process comprises:
I synthesising an isocyanate-terminated polyurethane prepolymer having an acid value of ≧44 mg KOH/g of prepolymer (solids) from reactants comprising an organic polyisocyanate component and an organic poly(isocyante-reactive group) component in which the isocyanate-reactive groups are selected from —OH and optionally one or more of —NH
2
, —NH—, and —SH; wherein
(i) at least 70 weight % of said polyisocyanate component is constituted by at least one aliphatic polyisocyanate,
(ii) said poly(isocyanate-reactive group) component includes at least one acid-bearing poly(isocyanate-reactive group) compound for providing anionic groups which provide or contribute to water-dispersibility,
(iii) the reactants are used in amounts corresponding to a ratio of isocyanate groups to isocyanate-reactive groups within the range of 1.4/1 to 2.9/1;
II chain extending the polyurethane prepolymer using an active hydrogen chain extending compound(s) to form a polyurethane polymer;
III forming an aqueous dispersion of said polyurethane polymer;
IV incorporating a vinyl polymer into said polyurethane polymer dispersion, whereby the weight ratio of the polyurethane polymer to the vinyl polymer is within the range of from 30/70 to 5/95.
The stages II, III and IV of the process are not necessarily carried out sequentially in the order shown or as individual steps (i.e. any desired order or regime can be used), as will become apparent later. (For example, the chain extension step may be carried out simultaneously with the formation of the aqueous polyurethane polymer dispersion by dispersion of the polyurethane prepolymer into an aqueous medium containing the chain-extender, or into an aqueous medium into which the chain-extender is subsequently incorporated; also, in such embodiments, rather than, as is usual, effecting vinyl polymerisation subsequent to chain-extension it would in principle be be possible to disperse the prepolymer into an aqueous dispersion of a preformed vinyl polymer with simultaneous or subsequent chain extension of the prepolymer. Use of the “acetone” process, however, will normally entail stages II and III being separate steps and performed sequentially. It might also be possible, for example, to carry out stages II, III and IV simultaneously).
There is further provided according to the invention a coating obtainable or derived from an aqueous composition comprising an aqueous polymer dispersion as defined above.
There is further provided according to the invention a method of coating a substrate using an aqueous composition comprising an aqueous polymer dispersion as defined above.
There is further provided according to the invention a substrate having a coating obtainable or derived from an aqueous composition comprising an aqueous polymer dispersion as defined above.
(It is to be understood that the vinyl polymer component of the invention d
Martin Emilio
Overbeek Gerardus Cornelis
Smak Yvonne Wilhelmina
Avecia BV
Niland Patrick D.
LandOfFree
Aqueous polymer dispersions does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Aqueous polymer dispersions, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Aqueous polymer dispersions will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2838028