Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
1998-03-09
2002-09-17
Gallagher, John J. (Department: 1733)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S332000, C427S207100, C524S500000
Reexamination Certificate
active
06451141
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The production of seals and coatings and the bonding of tiles or floor coverings
The invention relates to methods of producing seals and coatings and of bonding tiles or floor coverings by applying compositions based on aqueous acrylate copolymer dispersions which have a filler content of at least 20% by weight and which are free from major amounts of volatile organic solvents, plasticizers and modified or unmodified natural resins of low molecular mass. The invention also relates to the use of such compositions as sealants, coating materials or single-side adhesives (adhesives for one-sided application).
2. Description of the Background
The development of new kinds of polymer dispersions based on acrylate more than 25 years ago saw a significant turning point in the processing of sealants and in the work involved in laying tiles and floor coverings. It was possible to provide the processor with sealants, coating materials or single-side adhesives in whose processing the risks were very greatly reduced relative to the processing of the rubber solutions which had been dominant up to that time, since only 5% rather than 75% of flammable solvents were released. Sealants, and single-side adhesives used for tiles or floor coverings, differ fundamentally from pressure-sensitive adhesives in their use and in the properties which are required for that use. Pressure-sensitive adhesives are, in general, systems having an overall high surface tack and are unfilled systems, i.e. contain no fillers. In contrast to sealants and single-side adhesives they are applied as thin films (film thicknesses of about 20 to 200 &mgr;m) and for this reason alone require very different polymer mechanics. The requirements for single-side adhesives are application of the composition to one side only, and also the ability to correct the laid tiles or floor coverings in the course of processing, the ability to remove fresh residues of composition from the tiles or floor coverings and from the tools using water, and also excellent aging resistance. These special requirements have also led to special test standards, such as the testing of peel and shear strength and the testing of the wet bonding capacity and the dry gripping capacity.
The aqueous, acrylate copolymer-based dispersions which it has been possible to obtain commercially to date as sealants or for the fixed laying of tiles or floor coverings include not only at least 20 percent by weight of filler but also relatively large amounts of organic solvents and/or plasticizers, a part of which escapes into the atmosphere as the system sets, or they include a relatively large proportion of low molecular mass resins, such as balsam resins or colophony resins. The presence of these resins, however, is a problem since they may—as compounds of low molecular mass—migrate, can be washed out, cause color changes, owing for example to oxidation or to impurities in the mixture, reduce the polymer strength, or else may be toxicologically objectionable.
SUMMARY OF THE INVENTION
It is an object of the present invention to discover improved compositions, based on aqueous acrylate copolymer dispersions containing at least 20% by weight of filler, for the production of seals, coatings, including impregnated systems, and for the bonding of tiles or floor coverings, which compositions comprise as far as possible no volatile organic solvents, plasticizers or low molecular mass resins, such as natural resins or modified natural resins, and which do not have the abovementioned disadvantages of the aqueous acrylate copolymer dispersions currently used for the methods, or which have such disadvantages only to a markedly reduced extent.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
We have found that this object can be achieved, by applying compositions based on aqueous acrylate copolymer dispersions, containing at least 20% by weight of fillers, as sealants, coating materials (including impregnating materials) or single-side adhesives, if use is made of a filler-containing aqueous dispersion of a polymer mixture comprising a) a polymer A having a K value of from 5 to 55 and a glass transition temperature of below −10° C., containing at least 50% by weight of copolymerized acrylic ester units, and b) a polymer B which is an acrylate copolymer having a glass transition temperature of from −50 to +50° C.
The invention accordingly provides a method of producing seals and coatings, including impregnated systems, and of bonding tiles or floor coverings by applying an acrylate copolymer dispersion which has a filler content of at least 20% by weight and which is free from major amounts of organic solvents, plasticizers and modified or unmodified natural resins of low molecular mass, which comprises applying an aqueous dispersion, containing at least 20% by weight of filler, of a polymer mixture comprising
a) a polymer A having a K value of from 5 to 55 and a glass transition temperature of below −10° C., at least 50% by weight of which comprises copolymerized units of at least one ester of acrylic acid, and
b) a polymer B which is an acrylate copolymer having a glass transition temperature of from −50 to +50° C.
The use of filler-containing aqueous acrylate copolymers as solvent-free single-side adhesives for floor coverings is known from EP-A 490 191. The compositions described therein, although free from solvent, necessarily include, however, a plasticizer and a resin. (Filler-containing aqueous acrylate copolymers for checked floor coverings, which are essentially free from organic solvents, plasticizers and resins, are described in EP-A 743 965. The dispersions described therein of acrylate polymers having glass transition temperatures of less than −25° C. correspond to the preferred polymers B in accordance with the present invention. EP-A 743965 does not describe a novel mixture of the polymers B with the polymers A.) In comparison to the dispersions of polymers B described in EP-A 743 965, the dispersions of the novel mixtures of the polymers B with the polymers A have improved processing properties when used as single-side adhesives for floor coverings, in terms of better fixing in the wet and dry state and of freedom from odor. Furthermore, they have surprising advantages in respect of adhesion to rubber and of a particularly high heat stability.
The dispersions used in accordance with the invention contain preferably less than 3% by weight, in particular less than 1% by weight, of the abovementioned solvents, plasticizers and natural resins. With particular preference they are completely free from these components.
The polymers A used in accordance with the invention for the mixture with the polymers B have a K value of from 5 to 55, (preferably from 5 to 30,) and a (glass transition temperature of below −10) and preferably from −20 to −60° C. and contain at least 50% by weight of copolymerized units of at least one ester of acrylic acid. (The polymers A have a polydispersity M
w
/M
n
of from 1 to 10, and preferably from 1 to 5, which is a measure of the breadth of the molecular weight distribution of the respective polymer.)
(The K values of the polymers used in accordance with the invention are determined in accordance with DIN 53726 in a 1% strength by weight solution in tetrahydrofuran at 25° C.) The glass transition temperature T
g
is determined with the aid of the DSC (Differential Scanning Calorimetry) method in accordance with ASTM 3418/82. For copolymers it can be calculated in approximation from the glass transition temperatures of the homopolymers of the corresponding monomers by the equation of Fox (T. G. Fox, Bull. Am. Phys. Soc. (Ser.II) 1 (1956) 123)
1
Tg
=
X
1
Tg
1
+
X
2
Tg
2
+
⋯
+
X
s
Tg
s
,
where X
1
, X
2
, . . . X
s
are the mass fractions of the monomers 1 to s and Tg
1
, Tg
2
, . . . Tg
s
are the glass transition temperatures of the homopolymers of the respective monomers 1 to s in kelvins. The glass transition temperatures of t
Barwich Jürgen
Däumer Bernd
Fickeisen Peter
Krobb Joachim
Wistuba Eckehardt
BASF - Aktiengesellschaft
Gallagher John J.
LandOfFree
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