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
1998-02-13
2001-01-30
Szekely, Peter A. (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...
C156S327000, C156S331600, C156S331800, C427S397000, C427S421100, C427S429000, C523S150000, C524S379000, C524S385000, C524S386000, C526S303100, C526S307400, C526S307600, C526S307700
Reexamination Certificate
active
06180705
ABSTRACT:
This invention relates to a polyacrylamide-containing adhesive composition having a lower molecular weight than corresponding commercially available adhesive compositions, to a process for the production of such an adhesive composition and to its use in surface bonding processes.
BACKGROUND OF THE INVENTION
DE-OS 43 39 642 describes antislip formulations, i.e. formulations which prevent two articles from unintentionally sliding in relation to one another, which consist of at least one colophony resin and/or a derivative thereof, at least one monohydric or polyhydric alcohol, a water-soluble or water-dispersible thinning agent optionally a propellent and optionally a thickener and—for the rest—water.
It is known from “Encyclopedia of Polymer Science and Engineering”, 2nd Edition, Vol. 17, John Wiley & Sons, New York, 1989, pages 730-784, more particularly pages 753 et seq., that polyacrylamide is used in adhesive compositions, more particularly in the paper industry by virtue of its dry strength and in the building industry as a laminate adhesive. Unfortunately, the disadvantage of applying such adhesive polymers in the form of an aqueous solution is the high viscosity of such compositions. This is attributable to the high molecular weight typical of the polymer which in turn is responsible for the mechanical strength subsequently required. Experience has shown that an excessive reduction in molecular weight leads to a considerable reduction in the strength of the bond.
DETAILED DESCRIPTION OF THE INVENTION
The problem addressed by the present invention was to provide a new polyacrylamide-containing adhesive composition which would not have the above-mentioned disadvantages of a high viscosity, but which at the same time would show comparable mechanical strength.
This problem has been solved by the characterizing features of claim
1
.
Accordingly, the present invention relates to a polyacrylamide-containing adhesive composition which is characterized in that it contains a polyacrylamide with a very low molecular weight of 2,000 to 8,000 g/mole and preferably 3,500 to 5,000 g/mole, as determined by gel permeation chromatography (GPC), and in that the polyacrylamide has a Brookfield viscosity of 5 to 500 mPas in the form of a 15% by weight aqueous solution at 25° C.
In one preferred embodiment, the polyacrylamide-containing compositions contain viscosity-regulating additives, for example water and/or monohydric or polyhydric alcohols, which are preferably liquid and evaporate from the adhesive system at 25° C. in accordance with practical requirements. One particular embodiment is characterized by the use of alcohols with a solubility of more than 3 g in 100 g of water at 25° C. These alcohols may be aliphatic or cycloaliphatic, saturated or unsaturated alcohols with a linear or branched chain. They may also contain other hetero atoms, for example oxygen in the form of an ether group.
Examples are ethanol, n-propanol, i-propanol, butanol, benzyl alcohol, cyclohexanol, di-, tri- and polyethylene glycol. Dihydric and trihydric alcohols are preferred, ethane-1,2-diol, propane-1,2-diol and/or propane-1,2,3-triol (glycerol) being particularly preferred.
The above-mentioned additives may consist both of pure water and of alcohols. This additive is present in the polyacrylamide-containing composition according to the invention in a quantity of generally 50 to 95% by weight and preferably 75 to 90% by weight. In one preferred embodiment and providing the polyacrylamide-composition is applied to a water-absorbing surface, an additive mixture of water and 5 to 30% by weight and preferably 5 to 15% by weight of an alcohol, preferably glycerol, is used so that excessive waving of the paper coated with the polyacrylamide composition is avoided. The pot life can be adjusted to between 1 and 360 minutes depending on the quantity of glycerol used, i.e. 5 to 45% by weight and preferably 10 to 30% by weight, based on the polyacrylamide composition.
In addition, a tackifier is also added to the polyacrylamide-containing compositions according to the invention, colophony resin with an average molecular weight below 2,000 g/mole being particularly mentioned in this regard. Colophony resin is obtained, for example, from the crude resin of conifers. It consists predominately of unsaturated carboxylic acids with the empirical formula C
20
H
30
O
2
, such as abietic acid and isomers thereof. However, more or less neutral substances, such as fatty acid esters, terpene alcohols and hydrocarbons, may also be present. A derivatized colophony resin is preferably used, for example a hydrogenated or disproportionated colophony resin, the object of the derivatization (for example saponification or addition of maleic acid) being above all to increase solubility in water. Useful colophony resins and derivatives thereof are balsam, tall oil and wood resins. Water-soluble balsam resin derivatives with a solubility of at least 3 g in 100 g of water at 25° C., which are marketed under the name of “Flexin® D”, are particularly suitable. Water-soluble colophony derivatives, more particularly saponified derivatives, are preferably used.
Suitable thinning agents—another sub-group of additives—are alkali metal or alkaline earth metal benzene sulfonates containing up to 18 and, more particularly, 1 to 4 carbon atoms in the alkyl group, but especially the sodium salt of propyl benzene sulfonate.
In addition, it is also possible—providing the polyacrylamide compositions according to the invention are to be used for spraying, but are not to be sprayed by means of a mechanical pump spray—to use a propellent selected, for example, from the usual hydrocarbon propellent gases known per se, such as propane, butane or mixtures thereof, which are optionally used together with ethanol or dimethyl ether. Carbon dioxide may also be used to spray the polyacrylamide compositions.
In addition, there are various other auxiliaries and additives, for example dyes and light stabilizers.
In the context of the present invention, the term “polyacrylamide” is mainly intended to apply to copolymers containing acrylamide and, in the extreme case, to polyacrylamide itself. These polyacrylamides have a copolymer content of up to 15% by weight and, more particularly, up to 5% by weight. Acrylamide-containing copolymers are understood to be cationic polyelectrolytes with which water-soluble polymers having a positive electrical charge are obtained. Examples include diallyl dimethyl ammonium chloride, diallyl diethyl ammonium chloride, diethyl aminoethyl methacrylate, dimethyl aminoethyl methacrylate, methyl acryloyloxyethyl trimethyl ammonium sulfate, methacryloyloxyethyl trimethyl ammonium chloride and 3-(methacrylamido)-propyl trimethyl ammonium chloride and the salts of acrylic acid or methacrylic acid, more particularly sodium acrylate. In addition, amphoteric water-soluble polymers, such as the known polybetaines, polyampholytes and interpolymer complexes, may also be added to the polyacrylamide-containing compositions according to the invention. Further information on polymers of this type can be found in “Encyclopedia of Polymer Science and Engineering”, Vol. 17, 1989, keyword: water-soluble polymers, more particularly pages 770 to 778.
The concentration of the individual components in the polyacrylamide-containing composition according to the invention is generally 5 to 50% by weight and preferably 10 to 25% by weight of at least one polyacrylamide, 50 to 95% by weight and preferably 75 to 90% by weight of a viscosity-regulating additive, 0 to 20% by weight and preferably 0 to 10% by weight of at least one tackifier and 0 to 25% by weight and preferably 5 to 15% by weight of at least one water-soluble or water-dispersible thinning agents.
The present invention also relates to non-waving adhesive compositions, more particularly spray adhesives and paper adhesives, which contain the polyacrylamide composition mentioned above, i.e. 5 to 50% by weight and preferably 10 to 25% by weight of at least one polyacrylamide, 50 to 95% by weight and prefer
Huebner Norbert
Mueller Wolf-Ruediger
Peters Bernd Willi
Schieferstein Ludwig
Harper Stephen D.
Henkel Kommanditgesellschaft auf Aktien
Jaeschke Wayne C.
Murphy Glenn E. J.
Szekely Peter A.
LandOfFree
Polyacrylamide with low molecular weight does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Polyacrylamide with low molecular weight, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Polyacrylamide with low molecular weight will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2554951