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
1999-09-03
2001-03-13
Yoon, Tae (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...
C524S005000, C524S831000, C523S342000, C528S501000, C528S503000
Reexamination Certificate
active
06201062
ABSTRACT:
The invention relates to a process for the preparation of dispersion powders which are free from protective colloids by spray drying or freeze drying the dispersion.
Dispersion powders which are redispersible in water and are based on vinyl ester polymers are known from the prior art and are employed, above all, for modification of hydraulically setting building material compositions. These redispersible dispersion powders are in general prepared by spray drying the corresponding aqueous dispersions of the vinyl ester polymers. To ensure the redispersibility of the spray-dried dispersion powders in water, protective colloids are added during the polymerization in aqueous dispersion and/or during the spray drying process.
EP-A 632096 (U.S. Pat. No. 5,567,750) describes the spray drying of aqueous vinyl ester polymers in the presence of polyvinyl alcohol as a protective colloid for the atomization. It is known from EP-A 78449 (Derwent Abstract AN 83-46976K) to carry out the atomization with the addition of naphthalenesulphonic acid-formaldehyde condensation products. EP-A 407889 (U.S. Pat. No. 5,225,478) describes the atomization of aqueous polymer dispersions in the presence of phenolsulphonic acid-formaldehyde condensation products. EP-A 134451 (Derwent Abstract AN 85-069875) discloses the preparation of dispersion powders by spray drying of aqueous dispersions in the presence of starches or proteins.
However, the use of protective colloids during the preparation of the redispersible dispersion powders involves a number of disadvantages. The protective colloids are relatively expensive, but must be employed in significant amounts to ensure an adequate redispersibility or blocking resistance. At the required amounts to be employed, the relative binder content of the dispersion powders is reduced and the use properties of the dispersion powders are adversely influenced. Furthermore, the addition of protective colloids can render the dispersion powders sensitive to water and influence the rheology of the redispersion.
There was therefore the object of providing a process for the preparation of dispersion powders which are redispersible in water, free from protective colloids and based on vinyl ester polymers.
An emulsifier-free dispersion powder which is free from protective colloids is known from DE-A 2222033 (U.S. Pat. No. 3,950,302). A disadvantage is that the preparation process for the polymer dispersion described therein is not reproducible.
EP-A 295727 relates to the preparation of vinyl acetate/ethylene copolymer dispersions for use in coatings, a tertiary vinyl ester (VeoVa9
R
) being copolymerized to reduce the tack. The copolymers obtainable by this process can also be employed as dispersions and dispersion powders which are free from protective colloids. The doctrine of EP-A 315278 is to carry out the copolymerization of vinyl acetate, ethylene and tertiary vinyl esters in the presence of acrylic acid esters in order to increase the conversion of the copolymerization. EP-A 518406 relates to the preparation of dispersions, which are free from protective colloids, of vinyl acetate copolymers with vinyl pivalate, one or more water-soluble comonomers being copolymerized. Although dispersions which are free from protective colloids are accessible by the procedures described therein, the polymer powders obtainable by these procedures show only a very moderate redispersibility.
The invention relates to a process for the preparation of dispersion powders which are free from protective colloids and redispersible in water, by spray drying or freeze drying of aqueous dispersions, which are free from protective colloids, of vinyl ester copolymers obtainable by free-radical emulsion polymerization of 40 to 99.5% by weight of vinyl acetate, 0 to 40% by weight of one or more alkenes, 0 to 40% by weight of one or more monomers from the group consisting of vinyl esters of C
6
- to C
12
-alkyl-carboxylic acids and (meth)acrylic acid esters of alcohols having 1 to 12 C atoms, and, if appropriate, further copolymerizable mono- or polyethylenically unsaturated monomers, and of 0.5 to 20% by weight of ethylenically unsaturated carboxylic acid amides or derivatives thereof, in the presence of 0.1 to 5% by weight of one or more emulsifiers from the group consisting of anionic and nonionic emulsifiers, and a persulphate initiator, the spray drying or freeze drying being carried out without the addition of protective colloids.
The data in % by weight here are in each case based on the total weight of the comonomers.
Suitable alkenes are, for example, ethylene, propylene and butadiene, preferably ethylene and butadiene, in particular ethylene.
Preferred vinyl esters having 6 to 12 C atoms are vinyl ethylhexanoate, vinyl laurate and vinyl esters of alpha-branched, tertiary carboxylic acids having 9 to 11 C atoms, such as VeoVa9
R
, VeoVa10
R
or VeoVa11
R
. The vinyl esters of alpha-branched, tertiary carboxylic acids having 9 to 11 C atoms are preferred.
Preferred carboxylic acid amides are acrylamide and methacrylamide. Preferred carboxylic acid amide derivatives are N-methylolacrylamide, N-methylolmethacrylamide, N-butoxymethylacrylamide, N-butoxymethylmethacrylamide, N-isobutoxymethylacrylamide and N-isobutoxymethylmethacrylamide. Particularly preferred amides are acrylamide and methacrylamide; in particular acryl-amide.
Examples of methacrylic acid esters or acrylic acid esters are their methyl, ethyl, propyl, n-butyl, i-butyl, t-butyl and 2-ethylhexyl esters. Examples of further copolymerizable mono- or polyethylenically unsaturated monomers are styrene, vinyl chloride, acrylic acid, methacrylic acid, fumaric acid and maleic acid and monoesters and diesters thereof, maleic anhydride, 2-acrylamidopropanesulphonic acid and vinylsulphonic acid. Examples of polyethylenically unsaturated comonomers are divinyl adipate, 1,9-decadiene, allyl methacrylate, triallyl cyanurate and crosslinking comonomers, such as acrylamidoglycolic acid (AGA), methacrylamidoglycolic acid methyl ester (MAGME) and polyglycol dimethacrylate. Further examples are Si-containing monomers, such as gamma-acryloxypropyl-triethoxysilane or vinyltriethoxysilane.
In a preferred embodiment, the comonomer phase comprises 60 to 98% by weight of vinyl acetate, 0 to 30% by weight of ethylene and 2 to 10% by weight of ethylenically unsaturated carboxylic acid amides or derivatives thereof.
The preparation by the process of aqueous emulsion polymerization is carried out at a polymerization temperature of in general 35° C. to 95° C., preferably at 40° C. to 80° C. Persulphates which are suitable for initiation of the polymerization are sodium persulphate, potassium persulphate and ammonium persulphate. The amount of initiator is preferably 0.01 to 1.0% by weight, based on the total weight of the comonomers. In a preferred embodiment, the persulphates are employed in combination with the corresponding amount of reducing agent. Suitable reducing agents are, for example, alkali metal formaldehydesulphoxylates, hydroxymethanesulphinic acid, ascorbic acid or sodium sulphite.
Suitable anionic emulsifiers are, for example, alkali metal salts of di-C
4
- to -C
12
alkyl esters of sulphosuccinic acid; alkali metal and ammonium salts of C
8
- to C
12
-alkyl sulphates, of ethoxylated alkanols having a C
12
- to C
18
-alkyl radical and a degree of EO of 3 to 50, of ethoxylated C
4
- to C
10
-alkylphenols having a degree of EO of 3 to 50, of C
12
- to C
18
-alkylsulphonic acids, of C
9
- to C
18
-alkylarylsulphonic acids and of sulphonates of ethoxylated, linear and branched C
8
- to C
36
-alkyl alcohols having a degree of EO of 3 to 50 are also suitable. Suitable nonionic emulsifiers are, for example, ethoxylated fatty alcohols having a C
8
- to C
36
-alkyl radical and a degree of ethoxylation (degree of EO) of 3 to 50; and ethoxylated mono-, di- and trialkylphenols having a C
4
- to C
10
-alkyl radical and a degree of EO of 3 to 50.
The polymerization is preferably carried out in the presence of an anionic emulsifier or of combinations of an anio
Braunsperger Robert
Figge Reiner
Weitzel Hans-Peter
Brooks & Kushman P.C.
Wacker-Chemie GmbH
Yoon Tae
LandOfFree
Method for producing protective colloid-free dispersions and... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for producing protective colloid-free dispersions and..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for producing protective colloid-free dispersions and... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2524190