Polymer compositions

Details Polymer compositions Polymer compositions

2000-04-17

2002-07-23

Wu, David W. (Department: 1713)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Polymers from only ethylenic monomers or processes of...

C526S323200, C526S329200, C526S318400, C526S258000, C526S263000, C526S264000, C524S539000, C524S543000, C524S556000

Reexamination Certificate

active

06423805

ABSTRACT:

This invention is concerned with polymer compositions. More particularly, though not exclusively, the invention is concerned with polymer compositions suitable for use as binders for cementitious grouts.
Ceramic tile adhesives are used extensively for adhering ceramic tiles to substrates, such as the walls, floors and ceilings of bathrooms and kitchens. Once the tiles are adhered to the relevant substrate, a grout is often used to fill the spaces between the tiles and so provide an appropriate finish. Grouts may be either non-cementitious or cementitious and may be purchased as a ready-to-use, formulated one-pack system (non-cementitious) or a two-pack system (cementitious), which comprises a wet part including a polymer, water and defoamer and a dry part including the cementitious component. A variation of the two-pack system involves the use of re-dispersible powder polymer. In this case, the polymer, defoamer and cement comprise the dry component, while the wet component is water only.
Once prepared, a cementitious grout soon begins to cure, typically within 45 minutes of first mixing the cementitious component with the water. It is the curing of the grout which leads to a hard, waterproof seal between the tiles.
The process of applying the grout is a manual process, performed by professionals or DIY enthusiasts. Whether a professional or a DIY enthusiast, such artisans will, at least from time to time, experience the necessity of having to dispose of unused cementitious grout, which grout had gone-off before the artisan had had opportunity to use it. This is particularly so, for example, where the artisan had either left the prepared grout unused for an extended period of time, such as over lunch, or left the grout applied to a substrate for too long before completing the appropriate task, such as in the case of a grout, before it is smoothed to be flush with the tile surface.
The time a grout takes to cure to a point where it is no longer workable is a measure of it's open time. For example, a grout with an open time of 45 minutes may be worked for up to 45 minutes after its preparation before its performance becomes impaired due to it's cure. In other words, the grout may be used for up to 45 minutes after it's preparation before the grout becomes unworkable and must be disposed of.
It is desirable for a grout to have a very long open time, thereby reducing unnecessary waste, but this must be tempered by the requirement for the grout to cure sufficiently quickly for the bathroom or kitchen to be available for use within a short period of time after the tiling has been completed. Typically, the kitchen or bathroom must be usable within 24 hours of completing the tiling. Accordingly, within 24 hours of application, the grout must be sufficiently hard and waterproof.
The curing properties of a cementitious adhesive or grout are primarily controlled by the hydration and crystallisation process between the cement and the water in the mix. However, it is known that the cure rate may be affected by the nature of the polymeric binder employed in the adhesive or grout mix. Binders used in ceramic tile adhesives and grouts are typically based on polymer compositions wherein the polymer is a copolymer formed from a mixture of monomers comprising at least two monomers selected from the group consisting of (C
1
to C
8
) alkyl (meth)acrylates, (meth)acrylic acid, and styrene. Commercially available aqueous polymer compositions, which are formed from a monomer mix as described above and which are promoted for use in ceramic tile adhesives and grouts, include Rhoplex FM-8814K, Rhoplex E-330, Rhoplex-2200, Rhoplex MC-76 and Rhoplex MC-1834 from Rohm and Haas Company, and Acronal S-400 from BASF AG. Cementitious grouts formulated with these binders tend to have an open time in the order of 40 to 50 minutes and are sufficiently cured after 24 hours from application.
To obtain economies of scale, manufacturers prefer to produce polymers which they may sell for use in several applications and formulators prefer to purchase polymers which they can formulate into several different products. For example, it is preferred if a new polymer primarily produced for use in a cementitious grout can also be used in or as a binder in a cementitious or non-cementitious ceramic tile adhesive, a coating, such as a cementitious or non-cementitious paint, or a mastic. In this way, the potential market for the new polymer is significantly enhanced. However, this is only true if the properties of the end product are not detrimentally affected by substituting or replacing an old polymer with the new polymer. In the most preferred situation, the new polymer will not only equal the performance of the old polymer, but will also somehow improve on that performance.
EP-A-0810274 discloses binders useful in low-emission coatings, such as plasters, tile grouts and paints, especially low-emission dispersion paints, and offer improved wet abrasion resistance. The binders comprise at least one aqueous polymer dispersion having a minimum film forming temperature less than 10° C. and prepared by free-radical aqueous emulsion polymerisation of a monomer mixture comprising a) 45 to 70 parts by weight of at least one monomer whose homopolymer has a Tg (glass transition temperature) less than 20° C., b) 30-55 parts by weight of at least one monomer whose homopolymer has a Tg greater than 50° C., c) 0 to 1 part by weight of at least one monomer with acidic groups, and d) 0 to 2 parts by weight of at least one extra monomer chosen from amides of alpha, beta-unsaturated C
3
-C
6
carboxylic acids, their hydroxy-(C
2
-C
6
) alkyl-esters and/or N-vinyl lactams, with the proviso that the total of the weight parts a) plus b) amounts to 100 parts by weight.
It is the object of the present invention to provide polymer compositions which are suitable for use in or as binders in cementitious grouts and which, once formulated into said grouts, are capable of contributing to an increased open time without affecting detrimentally any other properties expected from a grout. Preferably, the polymer compositions can be used in other fields of application.
In accordance with the present invention, there is provided a polymer composition comprising a film-forming copolymer, preferably having a Tg of from −40° C. to +30° C., formed by polymerisation of a monomer mixture comprising:
a) at least one monomer selected from the group of monomers consisting of (C
1
to C
18
) alkyl (meth)acrylates, styrene, substituted styrene, acrylonitrile, butadiene, isoprene, isobutylene, ethylene, propylene vinyl acetate and other vinyl esters of (C
1
-C
12
) carboxylic acids such as VV-9 and VV-10 from Shell Chemical Company and Vinate 2-EH from Union Carbide.
b) 1 to 3% by weight of said mixture of at least one monomer selected from the group of monomers consisting of amides of &agr;,&bgr;-unsaturated C
3
to C
6
carboxylic acids and N-vinyl lactams,
c) at least 1% by weight of said mixture of at least one hydroxy-(C
1
to C
8
)alkyl (meth)acrylate,
wherein the total quantity of b) and c) constitutes from 2 to 7.5%, preferably 2 to 6%, more preferably 2 to 5%, by weight of said monomer mixture, and
d) 0 or up to 1% by weight of said monomer mixture of at least one polymerizable compound comprising functional-acid groups.
In another aspect of the present invention, there is provided a method for increasing the open time of a cementitious composition comprising an aqueous polymer composition comprising a film-forming copolymer, preferably having a Tg of from −40° C. to +30° C., formed by polymerisation of a monomer mixture comprising:
a) at least one monomer selected from the group of monomers consisting of (C
1
to C
18
) alkyl (meth)acrylates, (C
5
to C
10
) cyclo-alkyl (meth)acrylates, styrene, substituted styrene, acrylonitrile, butadiene, isoprene, isobutylene, ethylene, propylene, vinyl acetate and other vinyl esters of (C
1
-C
12
) carboxylic acids such as VV-9 and VV-10 from Shell Chemical Company and Vinate 2-EH fro

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