Process to produce separation dispersions and their use

Details Process to produce separation dispersions and their use Process to produce separation dispersions and their use

2000-06-05

2003-07-08

Cain, Edward J. (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...

C524S804000

Reexamination Certificate

active

06590024

ABSTRACT:

The present invention is a further development of the method described in DE 28 45 541 and relates to the manufacture of glue-resistant coatings on the reverse side of pressure sensitive adhesive items, which, by a coating with a release layer produced by a hydrous dispersion, exhibits a hydrophobic and glue-resistant surface. These types of coatings are often used in the manufacture of pressure sensitive, adhesive tapes and labels. These items usually consist of a flat carrier material, for example, films, textiles or types of paper that have a pressure sensitive, adhesive coating on one or both sides. In order to protect this coating from sticking together, which is undesirable, it is given a non-adhesive covering until the time of usage. In the case of pressure sensitive, adhesive ribbons/tapes, the reverse side of the carrier material, having been given a non-adhesive finish, can function as a cover. A negative effect on the adhesive layer by a process of diffusion or a reduction of the non-adhesive effect during storage, in particular, through the influence of high temperatures and humidity is not desirable.
In numerous applications using pressure sensitive, adhesive coverings, additional and special demands are placed on the non-adhesive layer on the reverse side. For example, in the case of pressure sensitive, adhesive ribbons/tapes, the non-adhesive layer must have a defined remnant of adhesion to the pressure sensitive, adhesive layer, so that during transport, storage and use the coils remain in place. On the other hand, however, [they must be] sufficiently easy to unwind and cut to length either manually or automatically. Frequently, these types of coatings take on other essential functions for the application at hand. When using textiles as carriers, for example, in the area of wound/injury care, in addition to the release effect, the [need for] a hydrophobic surface that breathes using these types of coatings presents a special requirement. In the case of crepe papers, which are frequently used as the carrier material for cover tapes, reinforcement of the paper is required for the special demands in the paint and varnish industry, in order to increase tear resistance by means of these types of coatings when the tape is wet. In addition, they [are supposed to] protect the surface of the paper against wear and tear caused by rubbing, in both wet and dry conditions. A further requirement is that the non-adhesive coating has to have a firm adhesion for sprayed on paint and varnish formulations, so that drops from the residue of the sprayed on substance does not soil the treated surfaces. The use of release [strata]/films based on organic silicone or fluorine, which are frequently employed in pressure sensitive, adhesive items is undesirable, particularly in this field of the industry.
When one considers that this complex profile of requirements must be met when using the most diverse pressure sensitive, adhesive coatings, then the number of release agents already suggested is understandable.
In U.S. Pat. No. 2,269,712, shellac or nitrocellulose and other cellulose derivatives are suggested for coating the reverse side of pressure sensitive, adhesive cover tapes made out of paper. These types of coatings are not suitable for the present day requirements, because they possess very little non-adhesiveness and therefore it is very difficult to succeed in cutting a specified length from the roll. Besides, these materials are coated with solutions [made] of organic solvents, which is undesirable today for economic and environmental reasons.
U.S. Pat. No. 3,438,794 describes the use of carboxymethylcellulose in a mixture with water soluable salts from aliphatic sulfonic acids with long KW chains for the same purpose. Furthermore, U.S. Pat. No. 2,358,831 teaches the use of soaps and U.S. Pat. No. 2,032,845 the use of wax as release agents. These products are not suitable for present day needs and requirements, because the release effective components, for example soaps or waxes are low molecular substances capable of diffusion, which markedly reduce the adhesion of the various pressure sensitive, adhesive coatings soon after the pressure sensitive, adhesive rolls have been stored for only short periods of time.
In order to avoid these problems, low molecular non-adhesive substances are applied to the surface of the paper according to U.S. Pat. No. 2,803,557 and converted there to polymeric Werner chromium complexes of stearic acid. This process is expensive, causes undesirable color changes and is questionable from a toxicological point of view due to the use of the chromium compounds.
Polymer release agents have been known for a long time. In DE-PS 872 621, copolymer acrylates are described whose release effect is achieved by large quantities of higher homologous forms of acrylic esters. The patent applications DE-AS 1 594 057 and DE-AS 1 300 852 are based on similar raw materials.
Aside from copolymers based on acrylic esters, copolymers made from olefins and vinyl ethers with maleic acid anhydride are also known. The release effect is accomplished by a polymer-analogous conversion of anhydride groups with stearyl alcohol or stearyl amine, as described in DS-AS 1 075 772 and U.S. Pat. No. 3,342,625. U.S. Pat. No. 4,029,843 teaches, for example, to use a copolymer of octadecene or n-hexene with maleic acid anhydride for this purpose.
Polymeric additions are also performed to produce release layers. The polymeric addition of long-chained diamines and/or dioles on diisocyanates is known, as described in U.S. Pat. No. 3,970,599, or the conversion of prepolymers carrying isocyanate groups with hydroxyl groups or amino groups of special organosilicones according to U.S. Pat. No. 3,997,702. In this connection, the conversion of polyvinyl alcohol with stearyl isocynate is also known.
Almost all of the release agents mentioned above are produced in organic solvents and are of little interest today because of the expenses involved and the [requirements of] conditions established for environmental protection. Water-based preparation [methods] are especially desirable in the case of absorbent carrier materials, like crepe papers, which are most frequently used for cover-up, pressure sensitive, adhesive tapes. However, references to water-based systems are seldom found in the literature and usually pertain mostly to secondary dispersions, which have to be produced in an involved manner by removing the solvents. A further disadvantage is the relatively low softening range, which clearly decreases the release effect at high storage temperatures. Finally, the relatively high costs of the raw materials for the higher homologous forms of the corresponding vinyl esters and vinyl ethers that can be polymerized are not advantageous for the practical use of these types of materials. Release agents based on copolymers made of styrene with maleic acid adhydride and a successive polymer-analogous conversion of the anhydride groups with stearyl amine are a good compromise, as described in U.S. Pat. No. 3,342,625 mentioned above. Non-adhesive polymers having softening areas >100° C. with acceptably low raw material costs are produced by this method. The disadvantage, in this case, is that polymerization occurs in aromatic solvents that pose toxicological risks, for example toluene.
DE 28 45 541, mentioned at the beginning, sets forth a further improvement in which release effective copolymers can be produced, through direct emulsion polymerization in an alkaline aqueous medium, that consists of vinyl compounds, for example, styrene with stearyl derivatives of maleic acid, without the use of solvents. In addition, maleic acid anhyride is converted in a preliminary step to maleic acid monostearyl amide with stearyl amine, for example, and then radically polymerized in an aqueous, ammonia solution with a pH of 9. Due to the formation of ammonium salts, the maleic acid monostearyl amide has the capability to act as an emulsifier fo

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