Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2000-08-03
2002-11-26
Dawson, Robert (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C528S012000, C528S026000, C528S029000, C528S027000, C525S103000, C525S106000, C525S479000, C549S512000
Reexamination Certificate
active
06486267
ABSTRACT:
TECHNICAL FIELD
This invention relates to release compositions and, more particularly, to release compositions that exhibit relatively high release force values in combination with relatively low levels of release noise.
BACKGROUND OF THE INVENTION
Release compositions are used, for example, to coat papers or films which are used as release backing sheets (sometimes referred to as protective release sheets or release liners) overlying the pressure-sensitive adhesive used in pressure-sensitive products such as labels, decals, tapes, etc. The pressure sensitive adhesive adheres to the release coated surface of the release backing sheet sufficiently to enable the pressure-sensitive products to be handled prior to use. When such products are used, the release backing sheet is pulled off and discarded. The exposed pressure-sensitive adhesive is pressed onto a surface where the pressure sensitive product is to be placed.
It is generally desirable that release-coated papers and films exhibit a release force which is low enough to enable the release backing sheet to be easily removed from a pressure sensitive adhesive coated substrate, but not so low that the release backing sheet will become separated from the pressure sensitive adhesive prior to when desired by forces normally encountered in handling and processing such as printing, die cutting and matrix stripping. “Release force” is defined as the amount of force required to peel or separate the release-coated substrate from the adhesive.
With some applications it is necessary to employ release coatings that exhibit relatively high release force values. These are typically used in applications such as labeling wherein high-speed equipment is required. A problem that often occurs with these high-release force materials is that they also exhibit high levels of release noise. “Release noise” is defined as the noise that is made when the release-coated substrate is peeled or separated from the adhesive.
The problem therefore relates to providing a release composition that exhibits a high release force value while at the same exhibits a low level of release noise. The present invention provides a solution to this problem by providing release compositions that exhibit relatively high release force values at relatively low levels of release noise.
SUMMARY OF THE INVENTION
This invention relates to a curable release composition, comprising: (A) a compound represented by the formulae
wherein: n is a number in the range of about 1 to about 60; and T is
(B) a curable organopolysiloxane. This invention also relates to a method of making a release coated substrate comprising coating a substrate with the foregoing release composition and curing the coated composition. This invention relates to a release coated article comprising a substrate which has been coated with the foregoing release composition. The invention also relates to a multilayered article comprising a first substrate, a second substrate, a layer of the foregoing release composition which has been cured, and a layer of a pressure sensitive adhesive wherein the release layer is positioned between the first substrate and the layer of pressure-sensitive adhesive and is preferentially adherent to the first substrate, and the pressure-sensitive adhesive layer is positioned between the release layer and the second substrate and is preferentially adherent to the second substrate.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Component (A) of the inventive release composition is a compound represented by the formulae
wherein: n is a number in the range of about 1 to about 60; and T is
In one embodiment, n is a number in the range of about 4 to about 40, and in one embodiment about 6 to about 36, and in one embodiment about 6 to about 24, and in one embodiment about 6 to about 18, and in one embodiment about 8 to about 12.
An example of a commercially available material represented by formula (A-1) is available from Elf Atochem under the tradename Vikopol 24. This material has a structure corresponding to formula (A-1) wherein n is about 10. Vikopol 24 has an estimated molecular weight of 365 and a viscosity at 25° C. of about 125 centipoise. Another example is Vikopol 64 which is similar to Vikopol 24 except that n is about 32. Vikopol 64 has an estimated molecular weight of about 973 and a viscosity at 25° C. of about 300 poise.
The organopolysiloxane (B), which may be a polydimethylsiloxane, may be room temperature curable, thermally curable or radiation curable. Generally, the room temperature and thermally curable compositions comprise at least one organopolysiloxane and at least one catalyst or curing agent for such organopolysiloxane(s). Such compositions may also contain at least one cure accelerator and/or adhesivity promoter (sometimes referred to as an anchorage additive). As is known in the art, some materials have the capability of performing both functions, i.e., the capability of acting as a cure accelerator to increase the rate, reduce the curing temperature, etc., and also as an adhesivity promoter to improve bonding of the silicone composition to the substrate. The use of such dual function additives where appropriate is within the purview of the invention.
A wide variety of organopolysiloxanes (commonly called silicones) can be used in the practice of the invention. Such organopolysiloxanes are also sometimes referred to as polymeric silicone resins, rubbers, oils or fluids. These organopolysiloxanes are well known and fully described in the literature. These organopolysiloxanes are comprised essentially of silicon atoms connected to each other by oxygen atoms through silicon-oxygen linkages, e.g.,
wherein in formula (B-1) each R is an organic group, generally an alkyl group 1 to about 2 carbon atoms, and in one embodiment 1 carbon atom. The organopolysiloxanes, in one embodiment, are high molecular weight polymers or copolymers having molecular weights in the range of about 5,000 to 250,000, and in one embodiment about 8,000 to about 100,000. In one embodiment, these organopolysiloxanes are soluble in at least one hydrocarbon solvent, examples of which include xylene, toluene, methyl ethyl ketone, carbon tetrachloride, and the like. In general, any organic solvent having a boiling point equal to or less than that of xylene may be used in the compositions used in the practice of the invention. The solvent merely serves as a convenient vehicle or carrier for uniform application of the inventive release composition to a substrate. Thus, higher boiling solvents may be used but their use is usually not commercially economical. Various organopolysiloxanes are commercially available in organic solvents in various percent solids concentration. Exemplary of the silicone (organopolysiloxane) materials which can be used in forming the inventive release compositions include those disclosed in U.S. Pat. Nos. 2,258,218; 2,258,220; 2,258,222; 2,494,920; 3,432,333; and 3,518,325, which are incorporated herein by reference for their disclosures of such silicone materials.
Suitable catalysts which can be employed in the curing of the release compositions of the invention include various compounds containing metals such as tin, lead, platinum, rhodium, etc. Generally, the catalysts are tin, platinum or rhodium compounds such as the dialkyl tin esters. Specific examples of catalysts include: dibutyl tin diacetate, dibutyl tin di-ethylhexanoate, dihexyl tin di-2-ethyl hexanoate, ethyl tin trihexanoate, dibutyl tin dilaurate, octadecyl tin dilaurate, dibutyl tin diacetate, tri-butyl tin acetate, dibutyl tin succinate, various lead salts such as lead naphthenate and lead octoate, zinc octoate, zinc stearate, iron octoate, various organic peroxides such as benzoyl peroxide and 2,4-dichlorobenzoyl peroxide, and others well known in the art as curing agents or catalysts for organopolysiloxane (silicone) materials. Useful catalysts include the carboxylic acid salts of organotin compounds containing at least one carbon-tin bond. Metal complexes of platinum and rhodium are also useful. Amines and
Avery Dennison Corporation
Dawson Robert
Renner , Otto, Boisselle & Sklar, LLP
Robertson Jeffrey B.
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