JPH0692564B2 - UV activation of addition curable silicone coatings - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to ultraviolet activated curing of certain silicone coatings. More specifically, the present invention is
The present invention relates to curing of an addition-curable platinum-catalyzed silicone coating containing a dialkylacetylene dicarboxylate inhibitor by UV activation.

BACKGROUND OF THE INVENTION Silicone compositions that are curable by reaction of .tbd.SiH groups with silicon-bonded olefin groups in the presence of hydrosilation catalysts are known in the art and are described, for example, in US Pat. Nos. 2813218, 3249581 and 343636.
No. 6 specification. Since curing begins simultaneously with the mixing of the above components, the addition curable composition is typically supplied in two packages. In this case, one package contains the olefinically unsaturated polysiloxane and the hydrosilation catalyst and the other contains the organohydrogenpolysiloxane crosslinker.

When it is necessary to extend the pot life of the addition-curable organopolysiloxane composition or to formulate a one-pack addition-curable organopolysiloxane composition, a curing inhibitor may be added. Such a curing inhibitor is generally a compound that suppresses curing at room temperature but does not suppress curing at high temperatures. Such a curing inhibitor may be one that is deactivated by heat, or one that is volatile such that it is expelled from the coating composition at high temperatures.

A specific cure inhibitor that is deactivated by heat is dialkyl acetylenedicarboxylate. Such cure inhibitors are compounds represented by the formula ROOCC≡CCOOR, where R is a monovalent hydrocarbon group, and are disclosed in my US Pat. No. 4,347,346. .

An object of the present invention is to provide a curing method including a step of exposing an addition-curable platinum-catalyzed silicone coating composition containing a dialkyl acetylenedicarboxylate inhibitor to ultraviolet light. The inclusion of dialkyl acetylenedicarboxylate inhibitors effectively suppresses the hydrosilation reaction due to platinum metal catalyst-induced addition curing at room temperature, but cures effectively when exposed to UV light. Methods of curing such silicone release coating compositions are provided. The silicone coating formed in this way adheres strongly to the support (eg paper) to which it is applied, but also to materials (eg pressure sensitive adhesives) that would otherwise stick to the support. It serves to substantially detackify the support.

The silicone release coating composition of the present invention comprises the following components (a) structural formula RaR'bSiO _{(4-ab) / 2} (I) [wherein R is an organic group bonded to silicon by a C-Si bond]. A group selected from the group consisting of a monovalent hydrocarbon group, a monovalent halogenated hydrocarbon group and a cyanoalkyl group, generally having 1 to 30 carbon atoms, preferably 1 to 12 and most preferably Is a linear or branched group of 1 to 8 and R'is an olefinic hydrocarbon group bonded to silicon by a C-Si bond, but is generally a carbon atom bonded by a multiple bond. A linear or branched group having a number of 1 to 20, preferably 1 to 12 (for example, vinyl group, allyl group, methallyl group, butenyl group, pentenyl group, ethenyl group, etc.), and a is 0 to 3 preferably 0.5 to about 2
The value of b is 0.005 to 2.0, and the sum of a and b is equal to 0.8 to 3], the olefin organopolysiloxane having the unit: (b) Structural formula RaHbSiO _{(4 -Ab) / 2} (II) (wherein R, a and b are as defined above), an organohydrogenpolysiloxane having a unit represented by the formula (c), the component (a) and the component (B) 5 to 500 ppm of a platinum metal catalyst based on the olefin organopolysiloxane in sufficient amount to induce a co-reaction with (b), and (d) the olefin organopolysiloxane and the organohydrogenpolysiloxane. 0.018 to 1 relative to the silicone release coating composition in an amount effective to inhibit the hydrosilation reaction for addition curing during
It is composed of dialkyl acetylenedicarboxylate in a weight percentage. This composition has a composition of about 25-5000 at 25 ° C.
Centipoise, preferably an oil at room temperature, having a viscosity of about 300-1000 centipoise.
The above dialkyl acetylenedicarboxylate is a compound represented by the general formula ROOCC≡CCOOR (wherein R is as defined above), and the components (a) and (b) are present in the presence of a catalyst. It is used in an amount which is effective in suppressing the premature gelation due to the co-reaction with but is insufficient to prevent the curing of the composition upon irradiation with ultraviolet rays.

DESCRIPTION OF THE INVENTION The compositions of the present invention are particularly well suited for detackifying certain materials against other materials to which they would otherwise adhere (eg, glues and adhesives). . Moreover, such compositions can be applied directly to the substrate without the need for a solvent, thus avoiding all of the problems associated with paint solvents.

Such a composition is an organopolysiloxane consisting of several components which is thermally cured on the substrate onto which it is applied and adheres to it, thereby detackifying the substrate. Be useful.

The olefin organopolysiloxane having the structural unit represented by the formula (I) is generally described as follows.
Suitable for paints where it is preferred (though not essential) to contain no silanic hydrogen and contains olefinically unsaturated bonds due to double or triple bonds between two adjacent aliphatic carbon atoms And low-viscosity organopolysiloxane oils. Examples of the group represented by R in the formula (I) include an alkyl group (eg, methyl group, ethyl group, propyl group, isopropyl group, butyl group, octyl group, dodecyl group, etc.), cycloalkyl group (eg, cyclopentyl group). , Cyclohexyl group, cycloheptyl group etc.), aryl group (eg phenyl group, naphthyl group, tolyl group, xylyl group etc.), aralkyl group (eg benzyl group, phenylethyl group, phenylpropyl group etc.), those groups Halogenated derivatives (eg, chloromethyl group, trifluoromethyl group, chloropropyl group, chlorophenyl group, dibromophenyl group, tetrachlorophenyl group, difluorophenyl group, etc.) and cyanoalkyl groups (eg, β-cyanoethyl group, γ-
Cyanopropyl group, β-cyanopropyl group and the like). In addition, R is preferably a methyl group. Also included within the scope of formula (I) above are those materials in which R is a mixture of the above groups.

The group represented by R'in the above formula (I) is
Examples thereof include an alkenyl group (eg, vinyl group, allyl group, methallyl group, butenyl group, pentenyl group, etc.) and alkynyl group (eg, ethynyl group, propynyl group, butynyl group, pentynyl group, etc.). R'is preferably a vinyl group or an allyl group, and R '
Most preferably, is a vinyl group.

Olefin organopolysiloxanes within the scope of formula (I) above are known in the art and are described, for example, in Chalk US Pat. No. 3344111 and Modic US Pat. No. 3436366. Are described in detail in. Similarly, their methods of manufacture and their commercial availability are also known.

The olefinic organopolysiloxanes included within the scope of the present invention include (1) the structural formula RcR'dSiO _{(4-cd) / 2} (IV) where R and R'are as defined above. Yes,
c has a value of 0 to 2, and the sum of c and d is 0.8 to 3.0
And (2) structural formula RnSiO _{(4-n) / 2} (V), wherein R is as defined above and n is
(Having a value of 0.8 to 2.5) as a copolymer with an organopolysiloxane unit.
Thus, when the olefin organopolysiloxane used in the present invention is a copolymer of a unit within the range of formula (IV) and an organopolysiloxane represented by the average formula within the range of formula (V), Such copolymers generally contain 0.5 to 99.5 (mol)% units within the formula (IV) and 0.5 to 99.5 (mol)% units within the formula (V). Methods for making these copolymers are also known in the art. Most of such copolymers typically have the general formula Is a vinyl group chain-terminated polysiloxane represented by
R in the above formula is a monovalent hydrocarbon group containing no unsaturated bond. Illustrative groups represented by R include methyl, ethyl, propyl, butyl, and other similar saturated hydrocarbon groups, but for release paper applications typically do not include phenyl groups. Is. Also,
R'is a hydrocarbon group containing an alkenyl unsaturated bond.
Usually, R'represents a vinyl group, but may be an allyl group or a cycloalkenyl group. x and y are R'up to about 20 (wt)% of this vinyl chain terminated polysiloxane.
A positive integer selected to contain the group. The viscosity of such polysiloxanes is in the range of about 50 to about 100,000 centipoise at 25 ° C. Such vinyl group terminated polysiloxanes preferably contain up to about 20 (wt)% vinyl groups as R'groups and have a viscosity of 25.
It is preferably in the range of about 300 to about 550 centipoise at ° C. A suitable vinyl group chain-stopped polysiloxane has the general formula (Where x and y are as defined above).

In the silicone industry, methylhydrogenpolysiloxane oils are often used as crosslinkers for addition curable silicone systems. Particularly useful as crosslinkers in the present invention are those containing from about 10 to about 100% ≡SiH groups with the balance consisting essentially of dimethylsiloxy units and within the range of from about 25 to about 1000 centipoise at 25 ° C. It is a trimethyl group chain-terminated methylhydrogenpolysiloxane oil having a viscosity of.

Generally speaking, the organohydrogenpolysiloxane having the structural unit represented by the formula (II) preferably contains no olefinic unsaturated bond (though it is not essential) and contains silane hydrogen. Organopolysiloxane oils are included.

Organohydrogenpolysiloxanes such as those represented by formula (II) above are also known in the art and are also described in Chalk US Pat. No. 3344111 and Modic US Pat. No. 3436366. It is described in detail inside.

Similar to R in the formula (I), the group represented by R in the formula (II) includes an alkyl group (eg, methyl group, ethyl group, propyl group, isopropyl group, butyl group, octyl group, etc.). A cycloalkyl group (eg, cyclopentyl group, cyclopexyl group, cycloheptyl group, etc.), aryl group (eg, phenyl group, naphthyl group, tolyl group, xylyl group, etc.), aralkyl group (eg, benzyl group, phenylethyl group, Phenylpropyl group), halogenated derivatives of these groups (eg, chloromethyl group, trifluoromethyl group, chloropropyl group, chlorophenyl group, dibromophenyl group, tetrachlorophenyl group, difluorophenyl group, etc.) and cyanoalkyl group ( For example, β-cyanoethyl group, γ-cyanoprot Group, such as β- cyanopropyl group). Within the above formula (II),
Also included are materials in which R is a mixture of the above groups. Note that R in the above formula (II) is preferably a methyl group.

Specific substances included in the range of the formula (II) include:
Mention may be made of 1,3-dimethyldisiloxane, 1,1,3,3-tetramethyldisiloxane, and high polymers containing up to 100,000 or more silicon atoms per molecule. Within the scope of formula (II) above, there is also a cyclic structure such as a cyclic polymer of methylhydrogensiloxane represented by the formula (CH ₃ SiHO) x (where x is an integer of 3 to 10 or more). Substances are also included. A specific example thereof is tetramethylcyclotetrasiloxane.

The organohydrogenpolysiloxane used in the practice of the present invention also has the formula (1) RcHdSiO _{(4-cd) / 2} (VI) where R, c and d are as defined above. A) and at least one siloxane unit per molecule, and (2) the rest of the siloxane units within the range of the formula (V) can be defined as a copolymer.

Within the scope of formula (VI) are hydrogen siloxane units (H ₂ SiO) _1.5 , methyl hydrogen siloxane units (HSiCH ₃ O), dimethyl hydrogen siloxane units and dihydrogen siloxane units (H ₂ SiO). Siloxane units are included. In such copolymers, the siloxane units of formulas (V) and (VI) are present in proportions to produce organohydrogenpolysiloxanes within the scope of formula (II) above. Generally speaking, such copolymers contain 0.5 to 99.5 (mol)% siloxane units of formula (V) and 0.5 to 99.5 (mol)% siloxane units of formula (VI).

For conventional release coating applications, such organohydrogenpolysiloxane crosslinkers are trimethyl chain terminated methylhydrogen having a viscosity of about 10 to 500 centipoise at 25 ° C and a hydrogen content of about 0.1 to 1.67% by weight. It preferably comprises a polysiloxane oil.

The platinum metal catalyst used in the composition of the present invention is ≡SiH.
It can be any of the known platinum metal catalysts that are effective for inducing the reaction of a group with a silicon-bonded olefin group and are freely miscible in a solventless silicone polymer. Such materials include, for example, the platinum-hydrocarbon composites described in Ashby, U.S. Pat. Nos. 3,159,601 and 3,159,662, and Lamoreaux, U.S. Pat. No. 3,220,972. The platinum alcoholate catalysts mentioned are mentioned. Furthermore, the platinum chloride-olefin composites described in Modic US Pat. No. 3,516,946 are also useful in the present invention.

The use of small amounts of dialkyl acetylenedicarboxylate inhibitors in solvent-free paper release coating systems can significantly extend the pot life upon addition of catalyst without sacrificing curing performance. Generally, an effective amount of such an inhibitor is 0.018 to 1.0 (wt%), and preferably 0.
It is 1 to 0.25 (weight)%. Although it is possible to obtain a sufficiently long pot life by using the inhibitor of the present invention, when cured using ultraviolet rays, the composition rapidly cures to a tack-free surface that does not cause stains or migration. Form.

Dialkyl acetylenedicarboxylate is produced by the diesterification reaction of 2-butyne dicarboxylic acid and 2 equivalents of alcohol. Such alcohols include methanol, ethanol, butanol, benzyl alcohol, allyl alcohol and mixtures thereof. Such a reaction can be represented by the following equation.

HOOCC ≡ CCOOH + 2ROH → ROOCC ≡ CCOOR + 2H ₂ O or HOOCC ≡ CCOOH + CCOOH + ROH + R'OH → ROOCC ≡ CCOOR '+ 2H ₂ O
Examples thereof include dimethyl acetylenedicarboxylate, diethyl acetylenedicarboxylate, dibutyl acetylenedicarboxylate, methyl butyl acetylenedicarboxylate, and methyl ethyl acetylenedicarboxylate. Particularly useful in the practice of the present invention are diesters where R is a methyl or ethyl group.

An effective amount of dimethyl acetylenedicarboxylate is very readily soluble in silicone oils, and it has a boiling point above 200 ° C at atmospheric pressure and thus exhibits little volatility. Moreover, dimethyl acetylenedicarboxylate is readily available commercially. Furthermore, the total inhibitor concentration in the dimethylacetylene dicarboxylate-containing polysiloxane is extremely low, resulting in a significant reduction in overall cost. In addition, small amounts of dimethyl acetylenedicarboxylate as used in the present invention will be almost completely contained in the crosslinked polymer. Therefore, no free dimethylacetylene dicarboxylate remains after the composition is cured.

Dimethylacetylene dicarboxylate also effectively suppresses the platinum-catalyzed condensation curing reaction of polysiloxane compositions having silanol functional groups, as well as curing compositions having both silanol and vinyl functional groups. Suppress effectively. The base polymer of such compositions can be, for example, a silanol chain-terminated diorganopolysiloxane having pendant vinyl groups along the siloxane backbone.

In the method of the present invention, the silicone coating composition is cured by the following method.

(A) (a) RaR'bSiO organo with _{(4-a-b) /} olefin organopolysiloxane having a unit represented by _{2 (b) RaHbSiO (4-} a-b) / 2 in unit represented Hydrogen polysiloxane (wherein R is a group selected from the group consisting of a monovalent hydrocarbon group, a monovalent halogenated hydrocarbon group, a cyanoalkyl group, and a mixture thereof, and R ′ is an olefinic hydrocarbon group. A hydrogen group, a has a value of 0 to 3, b has a value of 0.005 to 2.0, and the sum of a and b is equal to 0.8 to 3), (c) the olefin organopolysiloxane To 5 to 500 ppm of platinum metal catalyst, (d) 0.018 to 1% by weight relative to the silicone release coating composition, and effective for suppressing premature gelation, but curing at high temperature Indicated by the general formula ROOCC≡CCOOR in an amount that is insufficient to prevent Providing a silicone release coating composition comprising a dialkyl acetylenedicarboxylate, wherein R is as defined above, and having a viscosity of 25 to 5000 centipoise at 25 ° C .; A silicone release coating having a thickness of 0.05 to 4.0 mils is formed by applying the silicone release coating composition on the surface, and (C) in order to overcome the curing inhibiting action of the dialkyl acetylenedicarboxylate. A method for detackifying a surface that would otherwise be tacky, comprising the steps of curing the silicone release coating with a sufficient amount of ultraviolet light.

The above components can be mixed in any order and can be cured by UV irradiation. Those skilled in the art should be familiar with UV curing, and the appropriate spectral range, luminous flux and irradiation time to achieve such curing will be readily determinable.

A preferred use of the composition as described above is as a release coating on a support. In that case, the composition as described above may be mixed, coated on a support as a thin film, and then cured by irradiation with ultraviolet rays. The support may be non-porous (ie, glass, plastic, metal foil, etc.), but is preferably porous (eg, paper or other fibrous material).

To enable those skilled in the art to better practice the invention,
Examples will be shown below. These examples are for illustrative purposes and should not be construed as limiting the scope of the invention.

Description of the Preferred Embodiments Example 1 A vinyl-group-terminated linear dimethylpolysiloxane oil having a viscosity of 500 centipoise is mixed with varying amounts of Karstedt platinum catalyst and dimethylacetylene dicarboxylate (DIMAC). did. Within 2 minutes of mixing, each composition had a bright orange yellow color. The compositions thus obtained and their component contents are shown in Table 1.

Example 2 Vinyl group chain-terminated linear dimethyl-methylvinylpolysiloxane containing 3.7 (wt)% D ^V i units and having a viscosity of 400 centipoise was mixed with varying amounts of Karstedt platinum catalyst and dimethyl acetylenedicarboxylate. (DI
MAC) mixed with. Within 2 minutes of mixing, each composition had a bright orange yellow color. The compositions thus obtained and their component contents are shown in Table 2.

Example 3 9: 1 each of Compositions 1-6 with trimethylsiloxy group chain-terminated linear dimethyl-methylhydrogenpolysiloxane containing 50 (wt)% ^DH units and having a viscosity of 350 centipoise. Were mixed in a weight ratio of. The coating compositions 1 to 6 thus obtained were coated on an aluminum Q panel, polypropylene panel or No. 40 SCK paper support. For the support after coating, as shown in Table 3,
Ultraviolet irradiation was performed in a dryer or in the air.

According to the above data, the D ^V i units present in the base polymer appear to retard the cure compared to the M ^V i functional oil. Also, as long as an effective amount of DIMAC is present, increasing Pt concentration does not accelerate curing.

Example 4 In this example, ultraviolet rays without Pt / DIM without thermal auxiliary means were used.
It is for confirming that the curing of the curing system to which AC is added is started. A low intensity UV source [UV Products, Inc. (UV Products) at a distance of 13/4 inches from the aluminum support having a coating composition of coating composition 1 having a thickness of 2 mils.
Products, Inc.) table lamp, 115V, 0.35A] was installed (unfocused). The luminous flux of ultraviolet rays is 6 J / cm ² per hour
It was set so that No significant difference was observed between room temperature (24 ° C) and the substrate temperature measured after irradiation with a low intensity UV source for 15 minutes. After about 2.5 hours of irradiation (ie irradiation giving a total luminous flux of 15 J / cm ² ), the coating cured and formed a well-fixed, rubbery surface that did not stain. Considering such an observation result with the observation result of the “shadow portion” in Example 3,
It is confirmed that the curing mechanism in this case is activated by ultraviolet rays.

Example 5 The pot life of Coating Compositions 1 and 3-6 was investigated by measuring the viscosity at a given temperature as a function of elapsed time. First, Table 4 shows the relationship between the elapsed time and the viscosity at 25 ° C.

Table 5 shows the relationship between the elapsed time and the viscosity at 4 ° C.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location C09D 5/00 PNV 6904-4J 183/05

Claims (6)

[Claims] 1. A. (a) Structural formula RaR'bSiO
Olefin organopolysiloxane having units represented by _{(4-ab) / 2} (b) Structural formula RaHbSiO Organohydrogenpolysiloxane having units represented by _{(4-ab) / 2}
(Wherein R is a group selected from the group consisting of a monovalent hydrocarbon group, a monovalent halogenated hydrocarbon group, a cyanoalkyl group and a mixture thereof, and R ′ is an olefinic hydrocarbon group. , A has a value of 0 to 3, b has a value of 0.005 to 2.0, and the sum of a and b is equal to 0.8 to 3), (c) reaction of (a) and (b) 5 to 500 ppm of platinum metal catalyst based on the above-mentioned olefin organopolysiloxane, (d) 0.018 to 1% by weight based on the silicone release coating composition, and premature gelation. An amount of a dialkyl acetylenedicarboxylate of the general formula ROOCC≡CCOOR that is effective to inhibit but is insufficient to prevent curing at elevated temperatures, where R is as defined above. And a viscosity of 25 to 5000 centipoise at 25 ° C. A silicone release coating composition having: (B) a silicone release coating having a thickness of 0.05 to 4.0 mils is formed by applying the silicone release coating composition on a suitable surface, and then (C) ) For an adhesive material, which is characterized by comprising various steps of curing the silicone release coating film by using an amount of ultraviolet rays sufficient to overcome the curing inhibiting effect of the dialkyl acetylenedicarboxylate. A method for detackifying a surface. 2. The olefin organopolysiloxane is
Viscosity of 300-1000 centipoise and 0.1-2.5 at 25 ℃
A process according to claim 1 which is a dimethyl vinyl chain terminated dimethyl-methyl vinyl polysiloxane copolymer oil having a vinyl group content of (wt%). 3. The organohydrogenpolysiloxane has a viscosity of 10 to 500 centipoise at 25 ° C. and 0.1 to 1.67.
The method of claim 1 which is a trimethyl group chain-terminated methylhydrogenpolysiloxane oil having a hydrogen content of (wt%). 4. A method according to claim 1 wherein said dialkyl acetylenedicarboxylate is selected from the group consisting of dimethyl acetylenedicarboxylate and diethyl acetylenedicarboxylate. 5. A process according to claim 1, characterized in that the group represented by R also contains a hydroxyl group. 6. The olefin organopolysiloxane of claim 1, which is a dimethylvinyl group chain-terminated dimethyl-methylvinylpolysiloxane copolymer oil having a viscosity of 1,000 to 100,000 centipoise at 25 ° C. Method.