Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2000-09-12
2002-02-19
Michl, Paul R. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
Reexamination Certificate
active
06348528
ABSTRACT:
The invention relates to an aqueous polymer dispersion comprising from 0.1 to 10 parts by weight per 100 parts by weight of polymer of an emulsifier A) having a phosphate group, wherein said emulsifier consists at least 50% by weight of ethylene oxide and propylene oxide groups and the proportion of said ethylene oxide groups and propylene oxide groups is in each case at least 10% by weight, based on the overall amount of ethylene oxide and propylene oxide groups.
The invention also relates to the use of the aqueous polymer dispersions as binders in paints and anticorrosion coatings.
Aqueous polymer dispersions comprising an emulsifier having phosphate groups are known, for example, from DE-A-2743764, EP-A-421909 and EP-A-221498. DE-A-2743764 relates to polymer dispersions which are used in paints. The emulsifier is an alkanephosphoric acid or ester thereof. EP-A-421909 describes, inter alia, emulsifiers having phosphate groups and ethylene oxide groups. The polymer dispersions are used as binders for coating compositions. The anticorrosion coating materials of EP-A-221498 comprise a polymer with a copolymerized emulsifier. The emulsfier consists of a phosphate group, propylene oxide groups and an ethylenically unsaturated group.
EP-A-115468 discloses the use of a mixture of an emulsifier having phosphate groups and an emulsifier having ethylene oxide and propylene oxide groups.
The purpose of emulsifiers is to stabilize emulsifier monomer droplets and the polymer particles, obtained after polymerization, in the aqueous phase. The desired aim is of course to achieve a sufficient stabilization with the minimum quantity of emulsifier. Coagulation has to be avoided.
On subsequent use, the emulsifier remains in the coating composition and so also effects the properties of the resulting coating. In many cases, emulsifiers are responsible for the formation of bubbles and unevenness in the surface of the coating.
Where the composition is used as a binder for paints, the emulsifier is additionally desired to allow a high pigment concentration in the aqueous dispersion and to leave the pigment binding capacity of the polymer as high as possible. Low pigment binding capacity in the polymer leads to relatively poor mechanical stability in the coating and so, for example, to inadequate wet abrasion resistance.
In the case of anticorrosion coating materials an additional desire is for the emulsifier to contribute to the corrosion protection.
It is therefore an object of the present invention to provide emulsifiers which go as far as possible toward meeting the requirements regarding the stability of polymer dispersions and the surface quality of coatings produced from them. For paints utility, moreover, there is a desire for a high pigment binding capacity and, in the case of anticorrosion coating materials, for good corrosion protection.
We have found that this object is achieved by the aqueous polymer dispersions defined at the outset. We have also found that the aqueous polymer dispersions can be used as binders in paints and anticorrosion coatings.
The emulsifier present in the aqueous polymer dispersion is preferably a compound consisting at least 70% by weight of ethylene oxide and propylene oxide groups.
An essential feature of the emulsifier is that it comprises both ethylene oxide groups and propylene oxide groups.
The proportion of ethylene oxide groups is at least 10% by weight, preferably at least 40% by weight, based on the molar weight of the emulsifier.
The proportion of propylene oxide groups is at least 10% by weight, preferably at least 20% by weight, based on the molar weight of the emulsifier.
The molar weight of the emulsifier is preferably from 400 to 2000 and, with particular preference, from 600 to 1600 g/mol.
The emulsifier is preferably of the formula
where
R is C
1
-C
18
-alkyl
x, y, w, z are each an integer from 0 bis 30,
x+w is at least 1
y+Z is at least 1
n is 1 or 2
B is a mono- or divalent cation
a, c are each 1 or 2 with a*c=3-n
R is preferably C
10
-C
16
-alkyl. The sum x+w is preferably from 6 to 20 and, with particular preference, from 10 to 14. The sum y+z is preferably 2 to 10 and, with particular preference, from 3 to 7. Both w and z are preferably 0.
B is preferably a monovalent cation, especially of Na, K, NH
3
or H; accordingly, c=1 and a=1 or 2.
Compounds of this kind are obtainable, for example, under the trade name Lutensit® (BASF).
The aqueous polymer dispersion of the invention comprises the emulsifier preferably in amounts of from 0.1 to 5 parts by weight and, with particular preference, from 0.2 to 3 parts by weight per 100 parts by weight of polymer.
The polymer consists preferably of
a) from 40 to 100% by weight, preferably from 60 to 100% by weight and, with particular preference, from 80 to 100% by weight of at least 1 principal monomer and
b) from 0 to 40% by weight, preferably from 0 to 25% by weight, with particular preference from 0 to 15% by weight of further copolymerizable monomers.
Principal monomers a) are selected from C
1
-C
20
-alkyl (meth)acrylates, vinyl esters of carboxylic acids of up to 20 carbons, vinylaromatic compounds of up to 20 carbons, ethylenically unsaturated nitriles, vinyl halides, vinyl ethers of alcohols of 1 to 10 carbons, aliphatic hydrocarbons of 2 to 8 carbons and 1 or 2 double bonds, or mixtures of these monomers.
Examples that may be mentioned are C
1
-C
10
-alkyl (meth)acrylates, such as methyl methacrylate, methyl acrylate, n-butyl acrylate, ethyl acrylate and 2-ethylhexyl acrylate.
In particular, mixtures of the alkyl (meth)acrylates are also suitable.
Examples of vinyl esters of carboxylic acids with 1 to 2 carbons are vinyl laurate, stearate, propionate and acetate and also Versatic acid vinyl ester.
Suitable vinylaromatic compounds are vinyltoluene, &agr;- and p-methylstyrene, &agr;-butylstyrene, 4-n-butylstyrene, 4-n-decylstyrene and, preferably, styrene. Examples of nitriles are acrylonitrile and methacrylonitrile.
The vinyl halides are chloro-, fluoro- or bromo-substituted ethylenically unsaturated compounds, preferably vinyl chloride and vinylidene chloride.
Examples of vinyl ethers are vinyl methyl ether or vinyl isobutyl ether. Preference is given to vinyl ethers of alcohols of 1 to 4 carbons.
Hydrocarbons of 2 to 8 carbons and two olefinic double bonds that may be mentioned are butadiene, isoprene and chloroprene.
Suitable monomers (a) are preferably the alkyl (meth)acrylates, preferably C
2
-C
10
-alkyl acrylates and methacrylates, and the vinylaromatic compounds, and also mixtures of these compounds.
Very particular preference is given to methyl methacrylate, n-butyl acrylate, n-hexyl acrylate , octyl acrylate, 2-ethylhexyl acrylate and styrene, and also mixtures of these monomers, as monomers (a).
Further monomers b) are, for example, hydroxy-containing monomers, especially C
1
-C
10
-hydroxyalkyl (meth)acrylates, (meth)acrylamide, ethylenically unsaturated acids or acid anhydrides, especially carboxylic acids, such as (meth)acrylic acid or itaconic acid, or dicarboxylic acids, such as maleic acid or fumaric acid. Examples of further monomers b) also include crosslinking monomers, such as butanediol diacrylate or divinylbenzene.
The polymer can also be of multistage construction. In this case the stages differ in their monomer composition. The monomers of one stage are preferably polymerized to the extent of at least 80% by weight, with particular preference at least 90% by weight, based on the sum of the monomers of the respective stage, before beginning with the addition of the monomers of the next stage.
A multistage construction is not necessary in the context of the present invention. However, it has been observed that a multistage construction results in a lower minimum film-forming temperature with simultaneous good blocking resistance (virtually no sticking of coated substrates to one another on stacking).
Particular preference is given in this context to a two-stage construction.
The stages called I and II below contain preferably th
Dersch Rolf
Haunschild Alexander
Ley Gregor
Rau Maria Gyopar
Schlarb Bernhard
BASF - Aktiengesellschaft
Michl Paul R.
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