BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to crosslinkable compositions comprising(1) organosilicon compounds which have radicals containing aliphatic carbon-carbon multiple bonds,(2) organosilicon compounds having Si-bonded hydrogen atoms,(3) catalysts which promote the addition of Si-bonded hydrogen onto aliphatic multiple bond, and(4) agents which retard the addition of Si-bonded hydrogen onto aliphatic multiple bond at room temperature.

2. Description of the Related Art

Organopolysiloxane compositions which are curable by reaction of SiH groups with Si-bonded olefinic groups in the presence of a hydrosilylation catalyst are well known. The term “hydrosilylation catalyst” is understood as meaning a catalyst which promotes the addition of Si-bonded hydrogen onto an aliphatic multiple bond. Since crosslinking begins in the course of mixing the above constituents (1), (2) and (3), it is common practice to make addition-crosslinking organopolysiloxane compositions available in two or more components, one comprising the olefinically unsaturated organopolysiloxane and the hydrosilylation catalyst and the other comprising the organohydridopolysiloxane crosslinking agent.

If it is necessary to extend the pot life of addition-crosslinking organopolysiloxane compositions or to provide a one-component addition-crosslinking organopolysiloxane composition, an inhibitor can be present. The term “inhibitor” is understood as meaning agents which retard the addition of Si-bonded hydrogen onto an aliphatic multiple bond at room temperature, but do not retard crosslinking at elevated temperatures. Inhibitors of this kind are heat-deactivatable inhibitors or are sufficiently volatile to be expelled from the organopolysiloxane compositions at elevated temperature.

The label industry produces many labels that are to be printed via thermal energy, activating encapsulated ink within a paper substrate. These are called Direct Thermal Labels. Currently, these labels are laminated to a siliconized paper or film liner, which serves only as a carrier and is thrown away after the label is dispensed. A more ideal solution is to siliconize the thermally activatable label paper and not use a liner at all, reducing cost and waste. This is not possible with current thermally curing silicone systems, as the activation temperature of the curing mechanism exceeds the activation temperature of the ink capsules in the paper, causing the label to turn from white to black or other colors during application and curing. Another non-ideal solution is the use of UV curable silicone systems. These fail to perform adequately in many applications because they do not provide good enough release of the adhesive for many labels, and because they foul the thermal print heads.

U.S. Pat. No. 5,703,190 A discloses crosslinkable organosilicone compositions containing, as heat-deactivatable inhibitors, unsaturated organic compounds with CH≡C—C(OH)CH3— end groups and one or more double bonds e.g. a compound of the formal
CH≡C—C(OH)CH3—CH2—CH2—CH═C(CH3)2

which is commercially available from BASF under the tradename “Dehydrolinalool”.

U.S. Pat. No. 5,691,435 A discloses as inhibitors for crosslinking organosilicone compositions a list of compounds, including organic compounds with a triple bond, such as acetylinic alcohols, and the above mentioned “Dehydrolinalool” (DHL).

SUMMARY OF THE INVENTION

The object of the present invention is to provide inhibitors which extend pot life by retarding the crosslinking of the addition-crosslinking compositions based on organosilicon compounds at room temperature, but which at elevated temperatures less than or equal to 75° C. permit sufficiently complete crosslinking of the addition-crosslinking compositions based on organosilicon compounds, i.e. do not impair the crosslinking rate at elevated temperatures less than or equal to 75° C., and which possess no hazard potential with regard to toxicity and handling.

These and other objects are surprisingly and unexpectedly provide by the present invention which provides crosslinkable compositions comprising(1) organosilicon compounds which have radicals containing aliphatic carbon-carbon multiple bonds(2) organosilicon compounds having Si-bonded hydrogen atoms(3) catalysts which promote the addition of Si-bonded hydrogen onto aliphatic multiple bond and(4) agents which retard the addition of Si-bonded hydrogen onto aliphatic multiple bond at room temperature of the formula
CH2═C(R2)—CR(OH)—R  (I)

whereinR is a hydrogen atom or a monovalent hydrocarbon radical having 1 to 12 carbon atoms optionally substituted with one or more hydroxyl groups,
with the proviso that R is not a hydrogen atom if R1and R2are both a hydrogen atom,R1is a hydrogen atom or a monovalent hydrocarbon radical having 1 to 12 carbon atoms or R1form together with R a cyclic hydrocarbon radical having 1 to 12 carbon atoms andR2is a hydrogen atom or a monovalent hydrocarbon radical having 1 to 12 carbon atoms.

