KR940011192B1 - Uv-activation of addition cure silicone coatings - Google Patents

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Description

Method of Making Silicone Peeling Coating Composition

The present invention relates to ultraviolet activated curing of certain silicone coatings. More particularly, the present invention relates to ultraviolet activation curing of platinum catalyzed addition cured silicone coatings containing dialkylacetylene dicarboxylate inhibitors.

Silicone composition materials curable by the reaction of a SiSi group with a silicon-bonded olefinic group in the presence of a hydrosilylation catalyst are described in US Pat. Nos. 2,813,218,3,249,581 and It is well known in the art as described in US Pat. No. 3,436,366. Since the above-mentioned components start curing upon mixing, the additional curable compositions contain two packages containing one olefinically unsaturated polysiloxane and a hydrosilylation catalyst and the other containing an organohydrogenpolysiloxane crosslinker ( It is common practice to provide two packasge.

Curing inhibitors may be included in the curable composition when extended shelf life of the addition curable organopolysiloxane composition is needed or when provision of a one-component addition curable organopolysiloxane composition is required. Generally, curing inhibitors are compounds that cure slowly at ambient temperature but do not delay cure at elevated temperatures. These cure inhibitors are heat inactivation cure inhibitors or are sufficiently volatile to release the coating composition at elevated temperatures.

Particular heat inactivation cure inhibitors are dialkyl acetylene dicarboxylates. These inhibitors are described in the inventor's US Pat. No. 4,347,346 and are described by the general formula ROOCC = CCOOR, where R is a monovalent hydrocarbon radical.

It is an object of the present invention to provide a silicone coating composition in which a platinum catalyzed portion containing a dialkylacetylenedicarboxylate inhibitor curable with ultraviolet light is cured.

It is a further object of the present invention to provide a method of curing a platinum catalyzed addition curable silicone coating composition containing a dialkylacetylenedicarboxylate inhibitor, comprising exposing the coating composition to ultraviolet light.

The present invention is effective in delaying platinum catalyzed addition cure hydrosilylation reactions at room temperature but effectively cures when exposed to ultraviolet light, thereby strongly adhering to the substrate (e.g., paper) to which it is applied, but typically to a substrate (e.g. A silicone composition containing a dialkylacetylenedicarboxylate inhibitor, which forms a silicone coating that does not substantially adhere a substrate to a pressure-sensitive adhesive).

The release coating composition of the present invention having a viscosity at 25 ° C. of about 25 to 5,000 cP, preferably 300 to 1,000 cP and fluid at room temperature is a, an olefinorganopolysiloxane having the structural unit of formula (I) , b. Organohydrogenpolysiloxanes having structural units of the following general formula (II), c. a sufficient amount of platinum catalyst to cause a simultaneous reaction of (a) and (b) and d. Dialkylacetylenedicarboxylates in an amount effective to inhibit the addition cure hydrosilylation reaction between olefinorganopolysiloxanes and organohydrogenpolysiloxanes, wherein the dicarboxylate is of the formula ROOCC = CCOOR, wherein R Is as defined above) and inhibits premature gelling of the catalyzed co-reaction product of (a) and (b) but is present in an amount sufficient to prevent curing of the coating composition upon ultraviolet irradiation.

상기식에서, R은 C-Si 결합에 규소 결합된 유기 라디칼이며, 1가 탄화수소 라디칼, 할로겐화 1 가 탄화수소 라디칼 및 시아노알킬 라디칼로 이루어진 그룹중에서 선택되며, 통상 R은 탄소수 1 내지 30, 바람직하게는 탄소수 1 내지 12, 가장 바람직하게는 탄소수 1 내지 8의 직쇄 또는 측쇄를 함유하고, R'는 C-Si 결합에 의해 규소에 결합된 올레핀계 탄화수소 라디칼이며, 통상 탄소수 1 내지 20, 바람직하게는 탄소수 1 내지 12의 지방족 직쇄 또는 측쇄를 함유하고 다중 결합(예 : 비닐, 알릴, 메트알릴, 부테닐, 펜테닐,에테닐 등)에 의해 결합되며, a는 0 내지 3, 바람직하게는 0.5 내지 약 2이고, b는 0.005 내지 2.0이며, a와 b의 합은 0.8 내지 3이다.

Wherein R is an organic radical silicon bonded to a C-Si bond, and is selected from the group consisting of monovalent hydrocarbon radicals, halogenated monovalent hydrocarbon radicals and cyanoalkyl radicals, usually R having from 1 to 30 carbon atoms, preferably Containing straight or branched chains having 1 to 12 carbon atoms, most preferably 1 to 8 carbon atoms, and R 'is an olefinic hydrocarbon radical bonded to silicon by a C-Si bond, usually having 1 to 20 carbon atoms, preferably carbon atoms It contains 1 to 12 aliphatic straight or branched chains and is bound by multiple bonds (e.g. vinyl, allyl, metallyl, butenyl, pentenyl, ethenyl, etc.), a is 0 to 3, preferably 0.5 to about 2, b is 0.005 to 2.0, and the sum of a and b is 0.8 to 3.

The composition of the present invention is well suited to prevent the substrate from adhering to conventional adhesive materials such as glues and adhesives. In addition, the composition can be applied directly to the substrate without solvent, thus avoiding any problems with the coating solvents as mentioned above.

The composition is an organopolysiloxane composed of several components that can be heat cured onto the substrate upon coating and make the substrate non-adhesive.

The olefinorganopolysiloxanes having the structural units represented by formula (I) do not contain silane hydrogens (preferably but not necessarily) and do not have olefinic unsaturation by double or triple bonds between two adjacent aliphatic carbon atoms. And fluid organopolysiloxanes having a suitable branching degree for coating. In the formula (I), the radical represented by R includes alkyl such as methyl, ethyl, propyl, isopropyl, butyl, octyl and dodecyl; cycloalkyl such as cyclopentyl, cyclohexyl and cyclopeptyl; phenyl, naphthyl and tolyl And aryl such as xylyl, aralkyl such as benzyl, phenylethyl, phenylpropyl, chloromethyl, trifluoromethyl, chloropropyl, chlorophenyl, dibrodophenyl, tetrachlorophenyl, difluorophenyl and the like. Halogenated derivatives of the above-mentioned radical; cyanoalkyls such as βcyanoethyl, r-cyanopropyl, β-cyanopropyl, etc. Preferably, R is methyl and general formula (I) is R Also included are materials which are mixtures of these aforementioned radicals.

Examples of the radical represented by R ′ in the general formula (I) include alkenyl such as vinyl, allyl, metallyl, butenyl and pentenyl; And alkynyl such as ethynyl, propynyl, butynyl, pentynyl and the like. R 'is preferably vinyl or allyl, most preferably vinyl.

All olefin organopolysiloxanes within the scope of formula (I) are identified in US Pat. No. 3,344,111 to Chalk and US Pat. No. 3,436,366 to Modic; As is well known in the art. Similarly, their preparation and ease of purchase are also well known.

All olefin organopolysiloxanes within the scope of the present invention may be characterized as copolymers of siloxane units (I) of formula (IV) and organosiloxane units (2) of formula (V):

Wherein R and R 'are as defined above, c is 0 to 2, the sum of c and d is 0.8 to 3.0, and n is 0.8 to 2.5. Thus, the olefin organopolysiloxane used in the present invention is a copolymer of an organopolysiloxane having an average formula within the range of the general formula (V) and a unit within the range of the general formula (IV). Usually contains 0.5 to 99.5 mol% of units of the general formula (IV) and 0.5 to 99.5 mol% of units within the range of the general formula (V). Methods of making these copolymers are also well known in the art, most of the compositions are typically vinyl chainstopped polysiloxanes of general formula (A):

Wherein R is a monovalent hydrocarbon radical without unsaturation and suitable radicals include methyl, ethyl, propyl, butyl and other similar unsaturated hydrocarbons, but usually do not include phenyl groups for paper stripping purposes, and R ' Alkenyl unsaturated containing hydrocarbon radicals, usually representing vinyl groups, but may also represent allylic or cyclo-alkenyl unsaturated groups, and X and Y are vinyl chain-stopped olefinorganopolysiloxanes that It is a positive number to have about 20 weight% or less.

The viscosity of such olefinorganopolysiloxanes ranges from about 50 to about 100,000 cP at 25 ° C. Preferably, the vinyl chainstopped olefinorganopolysiloxane contains up to about 20% by weight of the vinyl group represented by R 'and the viscosity of the polymer is in the range of about 300 to about 550 cP at 25 ° C. Preferred vinyl chainstopped olefinorganopolysiloxanes have the general formula (B):

Wherein X and Y are as defined above.

Methylhydrogen fluids are often used by those skilled in the silicone art as crosslinkers for addition cured silicone systems. Trimethyl chainstopped polymethylhydrogensiloxane fluids having a viscosity of about 25 to about 1,000 cP at 25 ° C. having a SiH group of about 10% to about 100% and essentially the remainder being dimethylsiloxy units are used for the present invention. It is particularly useful as a crosslinking agent.

Organohydrogenpolysiloxanes having structural units represented by formula (II) are free of olefinic unsaturations (preferably but not necessarily) and broadly include fluid organopolysiloxanes containing silane hydrogen. Organohydrogenpolysiloxanes represented by formula (II) are also well known in the art, as particularly identified by US Pat. Nos. 3,344,111 and 3.436,366 to Chalk, which is incorporated herein by reference. It is.

Similarly to R in general formula (I), the radical represented by R in general formula (II) may be selected from alkyl such as methyl, ethyl, propyl, isopropyl, butyl octyl, and the like; Cycloalkyl, such as cyclopentyl, cyclohexyl, cycloheptyl; Aryl such as phenyl, naphthyl, tolyl, xylyl; Aralkyl such as benzyl, phenylethyl, phenylpropyl; Halogenated derivatives of these radicals, including chloromethyl, trifluoromethyl, chloropropyl, chlorophenyl, dibromophenyl, tetrachlorophenyl, difluorophenyl and the like; And cyanoalkyl such as β-cyanoethyl, r-cyanopropyl, β-cyanorofil, and the like. Substances in which R is a mixture of the above-mentioned radicals are also included within the scope of formula (II). The R group of the general formula (II) is preferably methyl.

Materials included in formula (II) include 1,3-dimethyldisiloxane, 1,1,3,3-tetramethyldisiloxane, as well as high molecular weight polymers containing 100,000 or more silicon atoms per molecule. Cyclic materials such as cyclic polymers of methylhydrogensiloxane of general formula (C) are also included in the scope of general formula (II).

(CH ₃ SiHO) _x (C)

Wherein x is a number from 3 to 10 or more.

In particular tetramethylcyclotetrasiloxane.

The organohydrogenpolysiloxanes used to practice the invention may also be characterized as copolymers containing at least one unit per molecule of formula (VI).

Wherein R, c, d and n are as defined above and the remaining siloxane units in the organopolysiloxane are in the range of formula (V).

Siloxane units such as hydrogen siloxane unit (H ₂ Si0) _1.5 , methylhydrogen siloxane unit (HSiCH ₂ O), dimethylhydrogen siloxane unit and dihydrogen siloxane unit (above (H ₂ SiO)) are represented by general formula (VI). In these copolymers, the siloxane units of formulas (V) and (VI) are present in an amount such that hydrogen polysiloxanes are formed within the range of formula (II). In addition, these copolymers contain 0.5-99.5 mol% of siloxane units of general formula (V), and 0,5-99.5 mol% of siloxane units of general formula (VI).

For conventional peel coating purposes organohydrogenpolysiloxanes, which are essentially trimethyl chain-stopped methylhydrogenpolysiloxane fluids having a viscosity at 25 ° C. of about 10 to 500 cP and a hydrogen content of about 0.1 to 1.67% by weight. Crosslinkers are preferred.

The precious metal catalyst component used in the compositions of the present invention is effective in catalyzing the reaction between silicon-bonded hydrogen groups and silicon-bonded olefinic groups. All well known platinum-metal catalysts which can be freely miscible in the solvent-free silicone polymer are included. These materials include, for example, platinum carbide complexes (see US Pat. Nos. 3,159, 601 and 3,159,662 to Ashby) and platinum alcoholate catalysts (Lamoreaux, US Pat. 3,220,972]. In addition, platinum chloride-olefin complexes (see, for example, US Pat. No. 3,516,946 to Modic) are also useful in the present invention. All of the aforementioned U.S. patents are incorporated herein by reference.

Small amounts of dialkylacetylenedicarboxylate inhibitors allow exceptionally long term catalysis pot-life without compromising cure performance in solventless paper stripping systems. Typically, the effective amount of the inhibitor is in the range of about 0.02% to about 1.0% by weight, preferably 0.1% to 0.25% by weight. With the inhibitor of the present invention, the composition cures quickly when cured with ultraviolet light, despite inducing adequate pot life, so that the composition cures as a non-adhesive surface free from stains and migration.

Dialkylacetylenedicarboxylates are produced by the diesterization reaction of 2-butynoic dicarboxylic acid with two equivalents of alcohol such as methanol, ethanol, butanol, benzene alcohol, allyl alcohol or mixtures of these alcohols. These reactions can be represented by the following schemes.

ROOCC≡CCOOR+2H₂O 또는HOOCC≡CCOOH + 2ROH

ROOCC≡CCOOR + 2H ₂ O or

ROOCC≡CCOOR'+2H₂OHOOCC≡CCOOH + ROH + R'OH

ROOCC≡CCOOR '+ 2H ₂ O

The effective concentration of dimethylacetylenedicarboxylate should be at a level that is well soluble in the silicone fluid, which does not volatilize violently since the boiling point is above 200 ° C. at atmospheric pressure. In addition, dimethylacetylenedicarboxylate is readily available. The total cost is also reduced as the concentration of the total inhibitor in the dimethylacetylenedicarboxylate-inhibited polysiloxane is significantly lowered. In addition, small amounts of the dimethylacetylenedicarboxylate inhibitors used according to the invention will be substantially completely included in the crosslinked polymer. Therefore, free dimethylacetylenedicarboxylate does not remain after the polymeric composition has cured.

Dimethylacetylenedicarboxylate will also effectively inhibit the silane catalyzed platinum catalyzed condensation curing reaction of the polysiloxane composition, as well as inhibit the silane from curing these compositions exhibiting both functional and vinyl functional groups. The base polymer for these compositions may be, for example, polydiorganosiloxane, chain-stopped silanes having pendant vinyl groups along the siloxane chain.

The components may be mixed in any order and may be exposed to curing UV radiation. Those skilled in the art are familiar with ultraviolet curing and can easily determine the appropriate spectrum, flux and exposure time.

A preferred use of the abovementioned compositions is as a release coating on a substrate. The composition is mixed, applied in a thin film on the substrate, and cured by exposure to ultraviolet light. The substrate may be nonporous, such as glass, plastic, metal foil, etc., but porosity, such as paper and other fibrous materials, is preferred.

In order to enable those skilled in the art to better practice the present invention, the following examples are illustrated but are not intended to be limiting.

Example 1

A vinyl chainstopped linear polydimethylsiloxane fluid having a viscosity of 500 cP is mixed with various amounts of Karstedt platinum catalyst and dimethylacetylenedicarboxylate (DIMAC). Within 2 minutes of mixing a deep yellowish orange color appears in each composition. Table 1 shows the compositions to be mixed and the components thereof.

TABLE 1

Example 2

A vinyl chainstopped, dimethyl, methyl-vinyl, linear silicone polymer having a viscosity of 400 cP with 3.7 wt% D ^V1 units is mixed with various amounts of Karstedt's platinum catalyst and dimethylacetylenedicarboxylate (DIMAC). Within 2 minutes of mixing a deep yellowish orange color appears in each composition. Table II shows the mixed compositions and components thereof.

TABLE II

Example 3

Each of the compositions 1-6 was mixed with a linear trimethylsiloxy chainstopped poly (dimethyl-methylhydrogen) siloxane having a viscosity of 350 cP having 50% by weight of D ″ units at a weight ratio of 9: 1. Bath compositions 1 to 6 are coated onto aluminum Q panels, polypropylene films or 40 # / ream SCK paper substrates.The coated substrates are exposed to ultraviolet light in an oven or air as shown in Table III.

TABLE III

* Unexposed areas should be across the coating.

* "Thin film" is about 5 mu.

From the above results, it can be seen that the -D ^V1 -unit present in the base polymer exhibits slower curing compared to the M ^{V1 -functional} fluid. As long as the amount of curing inhibition DIMAC is present, high Pt concentrations do not promote curing.

Example 4

This experiment is to demonstrate that ultraviolet light causes hardening of the Pt / DIMAC addition curing system without thermal assistance. A low intensity ultraviolet light source (UV Products, Inc. table top lamp, 115 volts, 0.35 amp.) Is placed 1 3/4 inch apart on an aluminum substrate coated with bath composition 1 to 2 mils thick. The UV flux is determined to be ⁶ J / cm ² hr. No significant difference can be detected between room temperature, i.e., the temperature measured on the substrate after exposure to 24 ° C. and a low intensity light source for 15 minutes. 2.5 hours exposure (ie 15 J / cm ² total flux) allows the coating to cure as a well fixed rubbery surface free of stains. Linking this observation to Experiment 3 “Non-exposed” observations reveals the ultraviolet properties of the present curing mechanism.

Example 5

The pot life of the bath compositions 1 and 3 to 6 is investigated by observing the viscosity as a function of time at a given temperature. Table IV shows the time / viscosity relationships at 25 ° C.

Table IV

Table V shows the time / viscosity relationships at 4 ° C.

TABLE V

Claims (6)

A. (A) an olefinorganopolysiloxane having units of formula (I) in an amount providing an olefinic hydrocarbon content of 0.1 to 20% by weight, (b) providing a hydrogen content of 0.1 to 1.67% by weight. Organohydrogenpolysiloxanes with units of the general formula (II), (c) from 25 to 100 ppm, based on olefin organopolysiloxanes, for the simultaneous reaction of (a) and (b) 0.02 to 1.0% by weight of the dialkylacetylenedicarboxylate of the general formula ROOCC≡CCOOR of the platinum catalyst and (d) the silicone coating composition, wherein the dialkylacetylenedicarboxylate is effective for inhibiting premature cure but curing at elevated temperature Is present in an insufficient amount to prevent), to prepare a silicone release coating composition having a viscosity of 25 to 5.000 cP at 25 ° C., B. Applying the silicone release coating to a thickness of 0.05 to 4.0 mil on a suitable surface Cloth C. Curing the silicone release coating with an amount of ultraviolet light effective to overcome the curing delay characteristics of the C. dialkylacetylenedicarboxylate (the temperature of the coating during curing is maintained in an insufficient range for thermal curing of the coating to occur. ) So that the surface is not adhered by a material that is typically adhesive to the surface.

Wherein R is selected from the group consisting of monovalent hydrocarbon radicals, halogenated monovalent hydrocarbon radicals, cyanoalkyl radicals and mixtures thereof, R 'is an olefinic hydrocarbon radical, a is 0 to 3 and b is 0.005 To 2.0, and the sum of a and b is 0.8 to 3. A dimethylvinyl chainstopped, dimethylmethylvinylpolysiloxane copolymer according to claim 1 wherein the olefin organopolysiloxane has a viscosity at 25 ° C. of 300 to 1.000 cP and a vinyl content of 0.1 to 20 wt%. How it is fluid. The process according to claim 1, wherein the organolilidegenpolysiloxane is a trimethyl chainstopped methylhydrogenpolysiloxane fluid having a viscosity at 25 ° C. of 10 to 500 cP and a hydrogen content of 0.1 to 1.67 wt%. The method of claim 1 wherein the dialkylacetylenedicarboxylate is selected from the group consisting of dimethylacetylenedicarboxylate and diethylacetylenedicarboxylate. The method of claim 1 wherein the radical group represented by R also contains hydroxyl radicals. The process of claim 1 wherein the olefinorganopolysiloxane is a dimethylvinyl chain-stopped dimethylmethylvinylpolysiloxane copolymer fluid having a viscosity at 25 ° C. of 1,000 to 100,000 cP.