Dispersions for producing paint for concrete roof tiles,...

Details Dispersions for producing paint for concrete roof tiles,... Dispersions for producing paint for concrete roof tiles,...

2000-09-11

2002-11-05

Kiliman, Leszek (Department: 1773)

Stock material or miscellaneous articles

Composite

Of addition polymer from unsaturated monomers

C428S507000, C428S505000, C525S328500, C524S457000, C524S460000

Reexamination Certificate

active

06475632

ABSTRACT:

The present invention relates to dispersions for preparing roof tile paints, to roof tile paints, and to roof tiles coated with roof tile paints.
In the course of the production of concrete roof tiles, a mortar mass is shaped and then generally colored, usually prior to curing, by coating with an emulsion paint (i.e., in the form of a dispersion). Subsequent curing then takes place together with the drying of the paint at temperatures of from 40 to 100° C. After curing, there may be a second coating with an emulsion paint or with a clearcoat, and subsequent drying.
In order that the paint does not coagulate on the uncured concrete, which is referred to as green concrete, the binder is required to possess a certain degree of stability, e.g. cement compatibility and heightened salt stability. This is generally achieved through the use of ionic and/or nonionic emulsifiers, and also by using functional monomers, such as methacrylic acid, acrylic acid, maleic acid, acrylamide, methacrylamide, ethenesulfonate and/or sulfoxyethyl methacrylate, for example. In addition to coloring, the emulsion paint has the function of preventing lime efflorescence as the concrete roof tiles cure. Another function is to prevent or reduce soil pickup, and in particular the growth of algae, on the finished roof tiles.
The use of dispersions based on (meth)acrylic esters and/or styrene for preparing roof tile paints is already known from DD 124808. EP-A-0 492 210 describes the use of certain monomers for reducing the soil pickup tendency of the concrete roof tile. For the purpose of reducing lime efflorescence, EP-A-0 469 295 claims the use of emulsifiers based on sulfonated diaryl ethers.
For the purpose of stabilization, the dispersions include hydrophilic constituents, such as emulsifiers and functional monomers such as methacrylic acid, acrylic acid, maleic acid, acrylamide, methacrylamide, ethenesulfonate or sulfoxyethyl methacrylate, for example. Owing to the hydrophobic constituents, the corresponding paint films exhibit heightened water absorption, which may lead to increased algal growth on the concrete roof tiles and, under conditions of freeze/thaw cycling, to cracking and flaking of the paint owing to the water absorbed.
For the purpose of preventing algal growth, DE-A-39 01 073 describes the use of copolymerizable tin compounds. Like the subsequent addition of algicides, however, this is ecologically objectionable.
It has now surprisingly been found that, by using carboxymethylcellulose as protective colloid, it is possible to prepare dispersions which, as binders in roof tile paints, exhibit sufficient cement stability but low water absorption in the paint film, leading to reduced algal growth, improved freeze/thaw stability of the coating, and enhanced protection against efflorescence.
The present invention provides for the use, for preparing roof tile paints, of a dispersion prepared using from 0.1 to 3, preferably from 0.1 to 1.5, percent by weight (based on the total monomer content) of carboxymethylcellulose as protective colloid, in connection with which a monomer composition comprising
a) from 85 to 99.8% by weight of acrylic esters with C
1
to C
12
alkanols, methacrylic esters with C
1
to C
12
alkanols and/or vinylaromatic monomers,
b) from 0.2 to 5% by weight of copolymerizable carboxylic acids, carboxamides, sulfates and/or sulfonates, and
c) from 0 to 10% by weight of other monomers
is polymerized in the form of an aqueous emulsion.
The carboxymethylcellulose used preferably comprises water-soluble carboxymethylcelluloses having a degree of substitution of from 0.4 to 2.9, with particular preference from 0.4 to 1.5, and in particular from 0.6 to 1.4, the degree of substitution referring to the average number of carboxymethyl groups introduced per anhydroglucose unit. It is preferred to use carboxymethylcelluloses whose 2% strength aqueous solutions possess a Brookfield viscosity (20 rpm) at 25° C. of less than 2000 (with spindle 3), with particular preference less than 500 (with spindle 2), and in particular less than 100 (with spindle 1) mPas. The carboxymethylcellulose is used preferably in the form of its ammonium salt or alkali metal salt. Examples of suitable commercial products are Blanose 7M®, Blanose 7UL®, Blanose 7EL® and Ambergum 3021® from Aqualon. The carboxymethylcelluloses of the invention may also comprise further constituents, especially alkyl or hydroxyalkyl radicals having 1 to 4 carbon atoms, alkyloxyalkyl radicals having 2 to 6 carbon atoms, or dialkylamino radicals having a total of 2 to 6 carbon atoms. Examples of suitable compounds are methylcarboxymethylcellulose, ethylcarboxymethylcellulose, hydroxyethylcarboxymethylcellulose, hydroxypropylcarboxymethylcellulose, methoxyethylcarboxymethylcellulose, ethoxyethylcarboxymethylcellulose and diethylaminocarboxymethylcellulose.
Monomers a) used comprise acrylic and methacrylic esters of C
1
to C
12
monoalcohols, such as ethyl acrylate, butyl acrylate, n-octyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, butyl methacrylate, cyclohexyl methacrylate and isobornyl methacrylate, and/or vinylaromatic monomers such as styrene or vinyltoluene, for example. Use is made of those combinations, known to the skilled worker, of softening monomers, such as butyl acrylate and 2-ethylhexyl acrylate, for example, with hardening monomers, such as methyl methacrylate and styrene, for example, so that the glass transition temperature of the corresponding copolymer is situated preferably in the range from −10 to 60° C., with particular preference in the range from −5 to 50° C., and in particular in the range from 0 to 40° C.
If operating by the technique of multistage emulsion polymerization, the hardening and softening monomers and the ratio of the phases should preferably be combined such that the dispersion possesses a minimum film-forming temperature in the range from 0 to 50° C. and the corresponding dispersion films possess an elongation at break of more than 150% for a film thickness of 100 &mgr;m.
As far as copolymerizable carboxylic acids, carboxamides, sulfates and/or sulfonates b) are concerned, preference is given to the use of acrylic acid, methacrylic acid, itaconic acid, acrylamide, methacrylamide, sulfoalkyl (meth)acrylates, such as the potassium salt of sulfopropyl methacrylate (=SPM from Roschig) and/or sulfoalkyl(meth)acrylamides, such as the sodium salt of acrylamido-2-methylpropanesulfonic acid (=AMPS from Lubrizol), for example.
Monomers which may be used as said other monomers c) are monomers containing keto groups, such as monomers containing acetoacetoxy groups, for example, examples being acetoacetoxyethyl methacrylate, acetoacetoxybutyl methacrylate, acrylamidomethylacetylacetone and vinyl acetoacetate, and polymerizable derivatives of diacetone, such as diacetoneacrylamide and diacetonemethacrylamide. Further compounds which may be used as monomers c) are hydroxyalkyl(meth)acrylates, glycidyl(meth)acrylates, alkoxyvinylsilanes, (meth)acryloyloxyalkylsilanes, (meth)acryloyloxyalkyl phosphates, and polymerizable ethyleneurea derivatives, such as N-(&bgr;-(meth)acryloxyethyl)-N,N′-ethyleneurea and N-(&bgr;-acrylamidoethyl)-N,N′-ethyleneurea, for example.
In order to improve the soil pickup behavior, dispersions whose other monomers c) include monomers containing keto groups may be admixed with polyfunctional carbohydrazides containing at least two hydrazide groups, such as adipohydrazide, oxalohydrazide, isophthalohydrazide and polyacrylopolyhydrazide, for example. It is preferred to use an equimolar ratio of hydrazide groups to keto groups.
The polymerization is conducted in accordance with the common techniques of emulsion polymerization, in which the monomers are emulsified in the aqueous phase in the presence of emulsifiers, initiators and the protective colloid and are polymerized at temperatures from 60 to 95° C. The emulsion polymerization may be conducted in accordance with the common techniques, known to the skilled worker, such as batch, monomer

Affiliated with

Also associated with

Rating

Dispersions for producing paint for concrete roof tiles,... does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Dispersions for producing paint for concrete roof tiles,..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Dispersions for producing paint for concrete roof tiles,... will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2985296