Coating processes – With post-treatment of coating or coating material – Heating or drying
Reexamination Certificate
2000-12-11
2002-04-30
Dawson, Robert (Department: 1712)
Coating processes
With post-treatment of coating or coating material
Heating or drying
C528S028000, C528S038000, C528S026000, C556S413000, C556S418000, C556S419000, C556S424000, C556S425000, C556S438000, C562S887000, C549S263000, C525S474000
Reexamination Certificate
active
06379751
ABSTRACT:
The invention relates to polysiloxanes containing carboxyl groups and intended for imparting water-repellency to substrates, in particular paper, textiles, leather or hides, in particular to leather and hides, and a process for their preparation, a water-repellent system containing this polysiloxane and a process for the production of hydrophobic substrates.
Upper leather, bag leather, apparel leather or automobile and furniture leather can be treated with softening retanning agents and water repellents so that a supple; water-repellent leather (waterproof leather) results, which does not permit penetration of water even under dynamic load. To achieve comfortable wear properties, leathers having high water vapour permeability are required. This is necessary, for example, for shoes or apparel leather.
Silicones containing carboxyl groups are disclosed in DE-A-35 29 869, DE-A-38 00 629 and WO 95/22627. These are silicones which contain carboxyl groups and whose COOH groups are linked to the silicone main chain via an alkylene group. The availability of these compounds on the industrial scale is however limited: the synthesis could be carried out, for example, by a platinum-catalyzed addition reaction of acids having unsaturated terminal groups with silicone oils having SiH functional groups, it being necessary to avoid secondary reactions by using protective groups. Finally, the protective group must also be removed hydrolytically by means of bases or acids. Such processes are also expensive. Furthermore, the stability of such emulsions during storage is still insufficient and the water-repellent effect is unsatisfactory.
DE-A-44 04 890 describes a process for imparting water-repellency to leather with polysiloxanes containing carboxyl groups in an aqueous emulsion in the presence of emulsifiers, which is characterized in that polysiloxanes, carboxyl-functionalized in a comb-like manner are used, in which the carboxyl groups are linked to the polymer main chain via spacer groups in the form of linear or branched C
2
- to C
40
-alkylene groups which can be interrupted by specific substituents. In the Examples, water-repellency is imparted to leather with polysiloxanes whose carboxyl groups are linked to the polysiloxane main chain via a (CH
2
)
10
spacer. Maeser values of 15000-30000 or 20000 to >100000 flexes were obtained by mineral salt fixation.
DE-C-196 46 916 relates to the use of carboxamido-polysiloxanes which are obtainable by reacting polysiloxanes having amino functional groups with dicarboxylic anhydrides for imparting water-repellency to materials of fibrous structure, in particular to leather and hides. The carboxyamido-polysiloxanes have a carboxyl group content of from 0.02 to 1.0 mmol/g and a molar mass Mn in the range from 2000 to 60000 g/mol. When these compounds are used, the leather treatment can be carried out in an aqueous liquor. Moreover, aftertreatment with metal salts and the use of emulsifiers and solvents is said to be unnecessary. The compounds mentioned in DE-C-196 46 916 can be prepared according to EP-A-95 676. However, as is evident from the Application Examples of DE 196 46 916, they do not reach the water-repellency values required for waterproof leather. As a rule, more than 50000 flexes are required in the Maeser test (based on ASTM D 2099-70). This is the number of flexes which the leather must withstand in a water bath under mechanical compression without water penetration. The leathers stated in DE-C- 196 46 916 become water-permeable only after a number of compressions 50% higher than the control (14600 compressions) (page 14, lines 45 to 47). Consequently, in spite of this progress, the achievable water-repellency effect is still insufficient. In the description, reference is made to the customary fixation with formic acid. The effect of imparting water-repellency can be enhanced by an aftertreatment with a divalent, trivalent or tetravalent metal salt customary in tanning, in particular with a basic chromium sulphate, with aluminium sulphate, zirconium sulphate, titanium sulphate, calcium chloride or magnesium sulphate (page 9, lines 25 to 27). In the Examples, use is also made of fixation with a chromium salt. Nevertheless, the Maeser values are still too low for many requirements. Conversely, however, this means that the fixation in the absence of metal salts is still in need of improvement.
However, with the use of carboxamido-polysiloxanes, polysiloxanes containing carboxyl groups and in particular polysiloxanes which contain free amino groups, further disadvantages still occur. The leathers dyed with customary dyes have a nonuniform colour intensity which may manifest itself in particular in the leather having two different sides. This means a colour difference between the grain side and flesh side of the leather, the flesh side appearing to have a substantially more intense colour than the grain side. The handle of the leather, too, is often silky, undesirably silicone-like or greasy when the known silicones are used.
DE-A-196 29 986 relates to a process for imparting water-repellency to leathers which have been tanned, in the absence of vegetable, synthetic and mineral tanning agents, only with polymer tanning agents and optionally, for pretanning, with aldehydes or reactive carbonyl compounds, in which polysiloxanes according to WO 95/22627 (polysiloxanes carboxyl-functionalized in a comb-like manner) are used as water repellents. For these products, too, fixation with zirconium salts is described, in order to achieve sufficient water-repellency effects.
DE-A-196 39 782 describes water-based organopolysiloxane-containing compositions which, when diluted with water, liberate essentially no alcohols and contain glycidyl ether alkyl and/or (meth)acryloyloxyalkyl groups as functional groups, each silicon in the organopolysiloxane carrying a functional group. In addition, aminoalkyl radicals are also claimed as a further functional group. The products are prepared by cohydrolysis of water-soluble organosilanes and are recommended, inter alia, for imparting water repellency to textile, leather and cellulose and starch products. Carboxyl groups are not mentioned as substituents.
DE-A-196 51 287 Al relates to ionic organosilicon compounds and their preparation and use. The claimed compounds are preferably obtained by an addition reaction of the double bond of functional acrylates or acrylamides with aminopolysiloxanes. The claimed ionic organosilicon compounds complex with transition metals and can thus bind permanently in the leather treatment (chrome-tanned leathers) and lead to a permanent hydrophilic treatment with the desired soft handle. In textile treatment, too, they have the advantage of leading to a soft handle with good body in addition to very good hydrophilic properties and very good antistatic properties (page 20, lines 21 to 27). These are in principle polysiloxanes having betaine character. Such products are however less suitable for imparting to leather water-repellency which must also withstand water penetration under dynamic loads, since the incorporated betaine groups do not lose their hydrophilic character (which however is desirable according to the statements in DE 196 51 287) and thus adversely affect the water-repellency effect.
DE-A-197 07 970 relates to polyorganosiloxanes having polycarboxylic acid functional groups. They are preferably prepared by reacting polysiloxanes having amino functional groups with polycarboxylic anhydrides, tricarboxylic anhydrides and tetracarboxylic anhydrides being used. Thus, at least two carboxyl groups are bonded to each amino group of the silicon via an amido group. This particular arrangement of at least two carboxyl groups per radical having a polycarboxylic acid function leads to high affinity of the polyorganosiloxanes having polycarboxylic acid functional groups to cationic substrates, in particular metal ions, owing to the chelate effect. Consequently, they are particularly suitable for the treatment of tanned leather (page 3, lines 2 to 5). However, the Examples pr
Hassel Tillmann
Novotny Fritz
Reiners Jürgen
Sackmann Günter
Schäfer Walter
Bayer Aktiengesellschaft
Dawson Robert
Gil Joseph C.
Henderson Richard E. L.
Peng Kuo-Liang
LandOfFree
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