WO2024106246A1

WO2024106246A1 - Curable organopolysiloxane composition and layered product

Info

Publication number: WO2024106246A1
Application number: PCT/JP2023/039869
Authority: WO
Inventors: 修司遠藤; 英文田中
Original assignee: ダウ・東レ株式会社
Priority date: 2022-11-18
Filing date: 2023-11-06
Publication date: 2024-05-23

Abstract

The purpose of the present invention is to provide a curable organopolysiloxane composition which can form a cured coating film having stable release properties from an adhesive substance without impairing the adhesive properties of the adhesive substance. This composition contains: (A) a linear organopolysiloxane which has a viscosity at 25°C of 20-1500 mPa·s and has a higher alkenyl group having 4-12 carbon atoms at a terminal and in a side chain of a molecular chain; (B) a linear organopolysiloxane which has a viscosity at 25ºC of 3000-50,000 mPa·s and has, in one molecule, at least two alkenyl groups having 2-12 carbon atoms only in side chains of a molecular chain, with the content of vinyl groups (CH2=CH-) in the alkenyl groups in component (B) being 0.1-0.3 mass%; (C) an organohydrogenpolysiloxane having at least two silicon atom-bonded hydrogen atoms per molecule; and (D) a hydrosilylation reaction catalyst.

Description

CURABLE ORGANOPOLYSILOXANE COMPOSITION AND LAMINATE

The present invention relates to a curable organopolysiloxane composition and a laminate produced using the composition.

Curable organopolysiloxane compositions are capable of forming cured films that exhibit adequate release performance against adhesive substances, and are therefore used as materials for forming peelable cured films. It is known that this composition can be blended with an organopolysiloxane that is not involved in the curing reaction to reduce the peel resistance against adhesive substances. However, even with such compositions, it is difficult to sufficiently reduce the peel resistance, and there is instead an issue of reducing the residual adhesive strength of adhesive substances.

On the other hand, in recent years, there has been a demand for solvent-free or low-solvent compositions. For example, Patent Document 1 describes such a composition, which has a viscosity of 50 to 5,000 mPa·s at 25°C, both ends of the molecular chain are blocked with trimethylsiloxy groups, and the side chains contain at least two alkenyl groups each having 4 or more carbon atoms (the content of alkenyl groups in the siloxane is 0.2 to 10.0 mol% of the total organic groups). .) and a mixture of a linear diorganopolysiloxane having a viscosity of 50 to 5,000 mPa·s at 25°C, containing at least two alkenyl groups in the molecule, and both molecular chain ends capped with dimethylalkenylsiloxy groups (the content of alkenyl groups in the siloxane is 0.2 to 10.0 mol % of the total organic groups); Patent Document 2 proposes a composition containing a dihydrogenpolysiloxane, a platinum-based catalyst, and 99 to 90 parts by weight of a linear diorganopolysiloxane having a viscosity of 5 to 1,000 mPa·s at 25° C., both molecular chain terminals being blocked with dimethylalkenylsiloxy groups and the alkenyl group content being 0.2 to 10.0 mol % of the total organic groups, and The proposed composition includes a mixture of 1 to 10 parts by weight of a linear diorganopolysiloxane that is blocked with siloxy groups and has at least two alkenyl groups bonded to silicon atoms in its side chains, with the alkenyl group content being 0.05 to 0.5 mol% of the total organic groups; an organohydrogenpolysiloxane that has a viscosity of 1 to 1,000 mPa·s at 25°C and at least three silicon-bonded hydrogen atoms in each molecule; and a platinum-based catalyst.

However, there is an issue that the peel resistance of the adhesive substance changes when a release sheet having a release coating made using such a composition is left stationary with no load and when it is pressed under a constant pressure. If the peel resistance of the adhesive substance increases due to the press treatment, causing heavy peeling, its applications are limited.

Also, attempts have been made to reduce the peel resistance of the adhesive substance before and after the press process, and to suppress severe peeling. However, there is an issue that the residual adhesion rate decreases after the adhesive substance is peeled off.

JP 2000-160102 A JP 2002-201417 A

The object of the present invention is to provide a curable organopolysiloxane composition that can form a cured film with stable release properties on adhesive substances without impairing their adhesive properties. Another object of the present invention is to provide a laminate having a cured film with stable release properties.

The curable organopolysiloxane composition of the present invention comprises:
(A) a linear organopolysiloxane having a viscosity at 25°C of 20 to 1,500 mPa·s and having higher alkenyl groups having 4 to 12 carbon atoms at the molecular chain terminals and in the side chains;
(B) a linear organopolysiloxane having a viscosity at 25°C of 3,000 to 50,000 mPa·s, having at least two alkenyl groups having 2 to 12 carbon atoms per molecule only at side chains of the molecular chain, and the content of said alkenyl groups in component (B) calculated as vinyl groups (CH ₂ ═CH-) is 0.1 to 0.3 mass %;
(C) an organohydrogenpolysiloxane having at least two silicon-bonded hydrogen atoms in each molecule, and (D) a catalytic amount of a hydrosilylation reaction catalyst,
a mass ratio of the component (A) to the component (B) {component (A)/component (B)} is 90/10 to 75/25;
The ratio of the number of moles of silicon-bonded hydrogen atoms in component (C) to the total number of moles of higher alkenyl groups in component (A) and alkenyl groups in component (B) is 0.5 to 5.0.

In the present composition, preferably, the higher alkenyl group in component (A) is a hexenyl group, and the content of said hexenyl groups in component (A) calculated as vinyl groups (CH ₂ ═CH—) is 0.5 to 3.0 mass %.

In addition, in this composition, both molecular chain terminals of component (B) are preferably blocked with trialkylsiloxy groups.

This composition is suitable for forming peelable cured coatings.

The laminate of the present invention is characterized by having a cured layer formed by curing the above-mentioned curable organopolysiloxane composition on at least one surface of the sheet-like substrate.

Furthermore, the laminate of the present invention is characterized in that it has a release layer formed by curing the above-mentioned curable organopolysiloxane composition on at least one surface of the sheet-like substrate, and has an adhesive layer on the release layer.

The curable organopolysiloxane composition of the present invention is characterized by its ability to form a cured film with stable release properties on adhesive substances without impairing their adhesive properties. In addition, the laminate of the present invention is characterized by its stable release properties.

<Definition of terms>
The term "viscosity" as used in this specification means a value (unit: mPa s or Pa s) at 25°C measured using a B-type rotational viscometer in accordance with JIS K 7117-1:1999 "Plastics - Liquid, emulsion or dispersion resins - Measurement method of apparent viscosity using a Brookfield rotational viscometer".

As used in this specification, the term "side chain of a molecular chain" refers to a bonding position other than the terminal of the molecular chain, and "having an alkenyl group at the side chain of a molecular chain" means that an alkenyl group is bonded to a silicon atom other than the terminal of the molecular chain of a linear organopolysiloxane.

The term "content calculated as vinyl group (CH ₂ ═CH-)" used in this specification means the content as vinyl group when the alkenyl group is calculated as the equimolar amount of vinyl group.

First, the curable organopolysiloxane composition of the present invention will be described in detail.

[Component (A)]
Component (A) is a linear organopolysiloxane having higher alkenyl groups having 4 to 12 carbon atoms at the molecular chain terminals and in the side chains. Examples of the higher alkenyl groups in component (A) include butenyl, pentenyl, hexenyl, heptenyl, and octenyl groups, with hexenyl groups being preferred. Examples of groups bonded to silicon atoms other than higher alkenyl groups in component (A) include alkyl groups having 1 to 12 carbon atoms, such as methyl, ethyl, propyl, butyl, pentyl, hexyl, and heptyl groups; aryl groups having 6 to 12 carbon atoms, such as phenyl, tolyl, and xylyl groups; aralkyl groups having 7 to 12 carbon atoms, such as benzyl and phenethyl groups; and fluoroalkyl groups having 3 to 12 carbon atoms, such as 3,3,3-trifluoropropyl, 4,4,4,3,3-pentafluorobutyl, 5,5,5,4,4,3,3-heptafluoropentyl, 6,6,6,5,5,4,4,3,3-nonafluorohexyl, and 7,7,7,6,6,5,5,4,4,3,3-undecafluoroheptyl groups, with methyl groups being preferred. Furthermore, in component (A), a small amount of hydroxyl groups or alkoxy groups having 1 to 3 carbon atoms, such as methoxy groups and ethoxy groups, may be bonded to silicon atoms, provided this does not impair the object of the present invention.

Although there are no limitations on the content of higher alkenyl groups in component (A), when they are hexenyl groups, it is preferable that the content of said hexenyl groups in component (A), calculated as vinyl groups (CH ₂ ═CH-), is in the range of 0.5 to 3.0 mass%, or in the range of 0.5 to 2.0 mass%. This is because when the content of hexenyl groups in component (A) is at or above the lower limit of the above range, the composition cures sufficiently, preventing migration of the silicone component to the adhesive substance of the resulting cured release coating and preventing a decrease in the residual adhesion rate of the adhesive substance, whereas when it is at or below the upper limit of the above range, the resulting cured release coating has an appropriately light peel resistance.

The viscosity of component (A) at 25°C is within the range of 20 to 1,500 mPa·s, and preferably within the range of 50 to 1,500 mPa·s, 50 to 1,000 mPa·s, or 100 to 500 mPa·s. This is because when the viscosity of component (A) is equal to or greater than the lower limit of the above range, the curability of the composition can be improved, whereas when the viscosity is equal to or less than the upper limit of the above range, the resulting peelable cured coating has relatively low peel resistance and changes over time are small.

Examples of such component (A) include a dimethylsiloxane-methylhexenylsiloxane copolymer in which both molecular chain terminals are blocked with dimethylhexenylsiloxy groups, and a methylhexenylpolysiloxane in which both molecular chain terminals are blocked with dimethylhexenylsiloxy groups.

[Component (B)]
Component (B) is a linear organopolysiloxane having at least two alkenyl groups having 2 to 12 carbon atoms in the molecule only on the side chains of the molecular chain. Examples of the alkenyl groups in component (B) include vinyl, allyl, butenyl, pentenyl, hexenyl, heptenyl, and octenyl groups, with vinyl being preferred. Examples of groups bonded to silicon atoms other than the alkenyl groups in component (B) include the alkyl groups having 1 to 12 carbon atoms, aryl groups having 6 to 12 carbon atoms, aralkyl groups having 7 to 12 carbon atoms, and fluoroalkyl groups having 3 to 12 carbon atoms, all of which are listed as examples of component (A), with methyl being preferred. Component (B) has alkenyl groups only on the side chains of the molecular chain, but the groups at the terminals of the molecular chain are not limited, and it is preferred that the component (B) has a trialkylsilyl group, for example. Examples of the trialkylsilyl group include trimethylsilyl and triethylsilyl groups. Furthermore, in component (B), a small amount of hydroxyl groups or alkoxy groups having 1 to 3 carbon atoms, such as methoxy groups and ethoxy groups, may be bonded to silicon atoms, provided this does not impair the object of the present invention.

The alkenyl group content of component (B), calculated as the content of vinyl groups (CH ₂ ═CH-), is in the range of 0.1 to 0.3 mass%, preferably 0.1 to 0.25 mass%, or 0.1 to 0.2 mass%. This is because when the alkenyl group content in component (B) is at or above the lower limit of the above range, the composition cures sufficiently, preventing migration of the silicone component into the adhesive substance of the resulting cured release coating and preventing a decrease in the residual adhesion rate of the adhesive substance, whereas when it is at or below the upper limit of the above range, the resulting cured release coating has an appropriately light peel resistance and there is little change in peel resistance due to the presence or absence of press treatment.

The viscosity of component (B) at 25°C is in the range of 3,000 to 50,000 mPa·s, preferably in the range of 4,000 to 45,000 mPa·s. This is because when the viscosity of component (B) is equal to or higher than the lower limit of the above range, the curability of the composition can be improved, while when the viscosity is equal to or lower than the upper limit of the above range, the resulting peelable cured coating has a relatively light peel resistance, and the change in peel resistance due to the presence or absence of press processing is small. In particular, when the viscosity of component (B) is low, the molecular weight is low, so that even with the same alkenyl group content, the number of alkenyl groups in one molecule is small. As a result, the reactivity of component (B) is low, and the silicone component is more likely to migrate to the adhesive substance of the peelable cured coating. In order to prevent this, a relatively high alkenyl content is preferable. On the other hand, when the viscosity is high, the molecular weight is high, so that even with the same alkenyl group content, the number of alkenyl groups in one molecule is large. As a result, the reactivity of component (B) is high, and the silicone component is more likely to remain inside the peelable cured coating. In order to promote localization of component (B) on the surface, it is effective to differentiate its relative reactivity with component (A), and a relatively low alkenyl group content is preferable for this.

Examples of such component (B) include dimethylsiloxane-methylvinylsiloxane copolymers with both molecular chain terminals blocked by trimethylsiloxy groups, methylvinylpolysiloxanes with both molecular chain terminals blocked by trimethylsiloxy groups, and dimethylsiloxane-methylvinylsiloxane copolymers with both molecular chain terminals blocked by dimethylhydroxysiloxy groups.

In this composition, the mass ratio of component (A) to component (B) {component (A)/component (B)} is within the range of 90/10 to 75/25, and preferably within the range of 90/10 to 77/23. This is because, when this mass ratio is equal to or greater than the lower limit of the above range, the curability of this composition, particularly at a low temperature of about 100°C, can be improved, and the strength of the resulting peelable cured coating can be increased, while, when it is equal to or less than the upper limit of the above range, the resulting peelable cured coating has a relatively low peel resistance. In this composition, component (B) is blended in a specific ratio relative to component (A), so that a peelable cured coating can be formed that has a relatively low peel resistance, that has a small change in peel resistance depending on whether or not a press treatment is performed, and that inhibits a decrease in the residual adhesion rate of the adhesive substance.

[Component (C)]
Component (C) is an organohydrogenpolysiloxane having at least two silicon-bonded hydrogen atoms in one molecule. Examples of groups bonded to silicon atoms other than hydrogen atoms in component (C) include the alkyl groups having 1 to 12 carbon atoms, aryl groups having 6 to 12 carbon atoms, aralkyl groups having 7 to 12 carbon atoms, and fluoroalkyl groups having 3 to 12 carbon atoms exemplified in component (A) above, and preferably methyl groups. In addition, component (C) may have a small amount of hydroxyl groups or alkoxy groups having 1 to 3 carbon atoms, such as methoxy groups and ethoxy groups, bonded to silicon atoms, as long as the object of the present invention is not impaired.

The viscosity of component (C) at 25°C is not limited, but is preferably within the range of 1 to 1,000 mPa·s, or within the range of 5 to 500 mPa·s. This is because when the viscosity of component (C) is equal to or greater than the lower limit of the above range, the evaporation of component (C) from the composition is suppressed, making the composition stable, whereas when the viscosity is equal to or less than the upper limit of the above range, the curing of the composition is promoted.

The molecular structure of such component (C) is not limited, and examples thereof include linear, partially branched linear, branched, cyclic, and resinous. Examples of such component (C) include a dimethylsiloxane-methylhydrogensiloxane copolymer capped at both molecular chain terminals with trimethylsiloxy groups, a dimethylsiloxane-methylhydrogensiloxane copolymer capped at both molecular chain terminals with dimethylhydrogensiloxy groups, a dimethylpolysiloxane capped at both molecular chain terminals with dimethylhydrogensiloxy groups, a methylhydrogenpolysiloxane capped at both molecular chain terminals with trimethylsiloxy groups, a cyclic methylhydrogenpolysiloxane, a cyclic methylhydrogensiloxane-dimethylsiloxane copolymer, a copolymer consisting of siloxane units represented by the formula: H( _CH3 ) _2SiO1 _/2 and siloxane units represented by the formula: SiO4 _/2 , and a copolymer consisting of siloxane units represented by the formula: ( _CH3 ) _3SiO1 _/2 _, siloxane units represented by the formula: H( _CH3 )2SiO1 _/2 and siloxane units represented by the formula: SiO4 _/2 .

In this composition, the content of component (C) is an amount such that the ratio of the number of moles of silicon-bonded hydrogen atoms in component (C) to the total number of moles of higher alkenyl groups in component (A) and alkenyl groups in component (B) is in the range of 0.5 to 5.0, and preferably in the range of 0.5 to 3.0, or in the range of 1.0 to 3.0. This is because when the content of component (C) is at or above the lower limit of the above range, the curability of this composition is improved, whereas when it is at or below the upper limit of the above range, the obtained release-hardened coating exhibits light release properties against adhesive substances.

[Component (D)]
Component (D) is a hydrosilylation catalyst for promoting the curing reaction of the composition. Component (D) can be exemplified by platinum catalyst, palladium catalyst, and rhodium catalyst, and is preferably platinum catalyst. This platinum catalyst is a catalyst containing platinum metal, and specifically, chloroplatinic acid, alcohol-modified chloroplatinic acid, olefin complex of chloroplatinic acid, complex of chloroplatinic acid and ketones, complex of chloroplatinic acid and vinylsiloxane, platinum tetrachloride, platinum fine powder, solid platinum supported on alumina or silica carrier, platinum black, olefin complex of platinum, alkenylsiloxane complex of platinum, carbonyl complex of platinum, platinum catalyst of thermoplastic organic resin powder such as methyl methacrylate resin, polycarbonate resin, polystyrene resin, silicone resin, etc., containing these platinum catalysts. In particular, platinum alkenylsiloxane complexes such as a complex of chloroplatinic acid and divinyltetramethyldisiloxane, a complex of chloroplatinic acid and tetramethyltetravinylcyclotetrasiloxane, platinum divinyltetramethyldisiloxane complex, and platinum tetramethyltetravinylcyclotetrasiloxane complex are preferred.

The content of component (D) is a catalytic amount that accelerates the hydrosilylation reaction of the composition, specifically an amount in which the catalytic metal in this component is within the range of 1 to 1,000 ppm by mass, or within the range of 5 to 500 ppm, relative to the total amount of components (A) to (C). This is because when the content of component (D) is at or above the lower limit of the above range, the curing of the composition is accelerated, whereas when it is at or below the upper limit of the above range, the resulting peelable cured coating is less likely to cause problems such as discoloration.

The composition may contain (E) a hydrosilylation reaction inhibitor to adjust the curing rate. Examples of such component (E) include alkyne alcohols such as 2-methyl-3-butyn-2-ol, 3,5-dimethyl-1-hexyn-3-ol, 3-methyl-1-pentyn-3-ol, 2-phenyl-3-butyn-2-ol, 1-ethynyl-1-cyclohexanol, 2-ethynylisopropanol, and 2-ethynylbutan-2-ol; silylated acetylene alcohols such as trimethyl(3,5-dimethyl-1-hexyn-3-oxy)silane, dimethylbis(3-methyl-1-butynoxy)silane, methylvinylbis(3-methyl-1-butyn-3-oxy)silane, and [(1,1-dimethyl-2-propynyl)oxy]trimethylsilane; 2-isobutyl-1-buten-3-yne, 3,5-dimethyl-3-hexen-1-yne, 3-methyl-3-penten-1-yne, 3-methyl-3- Examples include hexen-1-yne, 1-ethynylcyclohexene, 3-ethyl-3-buten-1-yne, and 3-phenyl-3-buten-1-yne and ene-yne compounds; unsaturated carboxylic acid esters such as diallyl maleate, dimethyl maleate, diethyl fumarate, diallyl fumarate, bis-2-methoxy-1-methylethyl maleate, monooctyl maleate, monoisooctyl maleate, monoallyl maleate, monomethyl maleate, monoethyl fumarate, monoallyl fumarate, and 2-methoxy-1-methylethyl maleate; alkenyl siloxanes such as 1,3,5,7-tetramethyl-1,3,5,7-tetravinylcyclotetrasiloxane and 1,3,5,7-tetramethyl-1,3,5,7-tetrahexenylcyclotetrasiloxane; and benzotriazole.

In this composition, the content of component (E) is not limited, but is preferably at least 0.001 parts by mass, at least 0.01 parts by mass, or at least 0.1 parts by mass, and at most 5 parts by mass, or at most 3 parts by mass, per 100 parts by mass of the total of components (A) and (B).

This composition can be used substantially solvent-free, but may be diluted with a known organic solvent. Examples of organic solvents include aromatic hydrocarbon solvents such as toluene and xylene, aliphatic hydrocarbon solvents such as hexane, octane, and isoparaffin, ketone solvents such as acetone, methyl ethyl ketone, and methyl isobutyl ketone, ester solvents such as ethyl acetate and isobutyl acetate, ether solvents such as diisopropyl ether and 1,4-dioxane, cyclic polysiloxanes with a polymerization degree of 3 to 6 such as hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, and decamethylcyclopentasiloxane, and halogenated hydrocarbons such as trichloroethylene, perchloroethylene, trifluoromethylbenzene, 1,3-bis(trifluoromethyl)benzene, and methylpentafluorobenzene. In particular, when applying a thin coating to a sheet-like substrate such as polyolefin having low heat resistance, ether solvents are preferred from the standpoint of curing and swelling properties.

The composition may contain, as optional components, adhesion promoters consisting of alkoxysilane compounds such as 3-glycidoxypropyltrimethoxysilane and 3-methacryloxypropyltrimethoxysilane; antioxidants such as phenols, quinones, amines, phosphorus, phosphites, sulfur, and thioethers; light stabilizers such as triazoles and benzophenones; flame retardants such as phosphate esters, halogens, phosphorus, and antimony; one or more antistatic agents consisting of cationic surfactants, anionic surfactants, nonionic surfactants, and the like; and other known additives such as heat stabilizers, dyes, and pigments.

Furthermore, since the physical properties and peelability of the resulting cured film are excellent, the composition may be cured by irradiation with energy rays (also called actinic rays), such as ultraviolet rays or electron beams, particularly ultraviolet rays. In this case, curing by ultraviolet rays includes curing by ultraviolet rays alone, or curing by ultraviolet rays and heat. In order to impart good ultraviolet curing properties to the composition, the composition may further contain (F) a photopolymerization initiator. Component (F) is a component that imparts ultraviolet curing properties to the composition, and by combining heat curing by addition reaction and ultraviolet curing, there is an advantage that damage caused by heat to a plastic film substrate with low heat resistance is reduced, and the adhesion of the cured product obtained by curing the composition to the plastic film is improved. Furthermore, there is an advantage that the silicone component is prevented from migrating from the surface of the cured film obtained by curing the composition onto the sheet, and the sheet is contaminated by the silicone component (this is called silicone migration), and the migration of the silicone can be further reduced.

This component (F) can be appropriately selected from known compounds that generate radicals when irradiated with ultraviolet light, such as organic peroxides, carbonyl compounds, organic sulfur compounds, and azo compounds. Specific examples include acetophenone, propiophenone, benzophenone, xanthol, fluorene, benzaldehyde, anthraquinone, triphenylamine, 4-methylacetophenone, 3-pentylacetophenone, 4-methoxyacetophenone, 3-bromoacetophenone, 4-allylacetophenone, p-diacetylbenzene, 3-methoxybenzophenone, 4-methylbenzophenone, 4-chlorobenzophenone, 4,4-dimethoxybenzophenone, 4-chloro-4-benzyl Examples include benzophenone, 3-chloroxanthone, 3,9-dichloroxanthone, 3-chloro-8-nonylxanthone, benzoin, benzoin methyl ether, benzoin butyl ether, bis(4-dimethylaminophenyl)ketone, benzyl methoxyketal, 2-chlorothioxanthone, diethylacetophenone, 2-methyl[4-(methylthio)phenyl]2-morpholino-1-propanone, 2,2-dimethoxy-2-phenylacetophenone, diethoxyacetophenone, 1-hydroxycyclohexyl phenyl ketone, and mixtures of two or more of these. In particular, diethoxyacetophenone and 1-hydroxycyclohexyl phenyl ketone are preferred as component (F).

The amount of component (F) is not limited, but is preferably within the range of 0.01 to 10 parts by mass, or 0.01 to 2.5 parts by mass, per 100 parts by mass of component (A). If the amount of component (F) is within the above range, the silicone migration of the release cured coating obtained by curing the composition can be improved, and the physical properties such as the mechanical strength can be improved.

[Method of preparing the present composition]
This composition can be produced by simply uniformly mixing the above components (A) to (D), further component (E) and other optional components. The order of addition of each component is not particularly limited, but when the composition is not to be used immediately after mixing, it is preferable to store the mixture of components (A), (B) and (C) separately from component (D) and mix both immediately before use. In addition, by adjusting the content of component (E) in the composition consisting of components (A) to (D) and component (E), it is possible to obtain a composition that does not crosslink at room temperature but crosslinks and hardens when heated.

When the composition is uniformly applied to a sheet-like substrate and heated under conditions sufficient to crosslink component (A) and component (C) through a hydrosilylation reaction, a sheet-like substrate can be produced having a cured layer on the surface of the substrate that has excellent slip properties, transparency, and adhesion to the substrate. The cured layer obtained by curing the composition also has the advantage of being flexible and breathable, with minimal air bubble entrapment even when applied to a non-flat object. For this reason, the composition can be used extremely well in applications where both the release properties of the cured layer and the adhesion properties of the cured layer to the object to be protected are important, such as protective films for optical displays and glass surfaces.

Next, the laminate of the present invention will be described in detail.

The laminate is characterized by having a cured layer formed by curing the composition on at least one surface of the sheet-like substrate.

In the laminate, the sheet-like substrate is not limited, but examples thereof include polyesters such as polyethylene terephthalate and polyethylene naphthalate; polyolefins such as polypropylene and polymethylpentene; polycarbonate; polyimide; and films made of plastics such as polyvinyl acetate; furthermore, papers such as Japanese paper, paperboard, corrugated paper, glassine paper, clay-coated paper, polyolefin-laminated paper, polyethylene-laminated paper, and synthetic paper; fabrics such as natural fiber fabric, synthetic fiber fabric, and artificial leather fabric; and other materials such as glass wool and metal foil. The film may be a single layer, or may be composed of two or more layers made of the same or different plastics. As the substrate, plastic films, particularly polyester films, are preferred, and polyethylene terephthalate films are particularly preferred, with biaxially oriented polyethylene terephthalate films being particularly preferred. Polyethylene terephthalate films are less likely to generate dust during processing, use, and the like. Therefore, poor coating of adhesive substances on the release sheet caused by dust and the like can be effectively prevented. In addition, by applying an antistatic treatment to a polyethylene terephthalate film and using it as a substrate, problems such as poor coating of adhesive substances can be prevented.

The thickness of the sheet-like substrate is not particularly limited, but is generally 10 to 300 μm, preferably 15 to 200 μm, and particularly preferably 20 to 125 μm.

Furthermore, in order to improve the adhesion between the sheet-like substrate and the cured layer, a support film that has been subjected to a primer treatment, a corona treatment, an etching treatment, or a plasma treatment may be used. Examples of primer compositions that can be used include a condensation type silicone primer composition that contains a polydiorganosiloxane having a SiOH group at the end, a polysiloxane having a SiH group, and/or a polysiloxane having an alkoxy group, and a condensation reaction catalyst; and an addition type silicone primer composition that contains a polydiorganopolysiloxane having an alkenyl group such as a vinyl group, a polysiloxane having a SiH group, and an addition reaction catalyst.

The surface of the sheet-like substrate opposite the cured layer may be subjected to a surface treatment such as scratch prevention, stain prevention, fingerprint prevention, anti-glare, anti-reflection, anti-static, etc. The above-mentioned surface treatment may be performed after the composition is applied to the sheet-like substrate, or the composition may be applied after the surface treatment. Examples of scratch prevention treatment (hard coat treatment) include treatment with hard coat agents such as acrylate-based, silicone-based, oxetane-based, inorganic-based, and organic-inorganic hybrid-based. Examples of anti-soiling treatment include treatment with anti-soiling agents such as fluorine-based, silicone-based, ceramic-based, and photocatalyst-based. Examples of anti-reflection treatment include wet treatment by coating with fluorine-based, silicone-based, and other anti-reflection agents, and dry treatment by vapor deposition or sputtering. Examples of anti-static treatment include treatment with anti-static agents such as surfactant-based, silicone-based, organic boron-based, conductive polymer-based, metal oxide-based, and vapor-deposited metal-based.

The temperature for curing the composition on the sheet-like substrate is generally 50 to 200°C, but may be 200°C or higher if the heat resistance of the sheet-like substrate is good. There are no particular limitations on the heating method, and examples include heating in a hot air circulating oven, passing through a long heating furnace, and radiating heat rays from an infrared lamp or halogen lamp. Curing may also be achieved by combining heating and ultraviolet irradiation. When component (D) is a platinum alkenylsiloxane complex catalyst, even if the amount of platinum metal blended is 1 to 5,000 ppm per part of the total amount of the composition, a cured layer with excellent slip properties, transparency, and adhesion to the sheet-like substrate can be easily obtained in a short time of 1 to 40 seconds at 100 to 150°C.

On the other hand, for sheet-like substrates such as polyolefins that have low heat resistance, it is preferable to coat the composition on the sheet-like substrate such as polyolefins and then heat it at a low temperature of 50°C to 100°C, more preferably 50°C to 80°C. In this case, the composition can be stably cured within a curing time of 30 seconds to several minutes (e.g., 1 to 10 minutes).

　The composition can be applied to the surface of a sheet-like substrate by any method known in the art, including dipping, spraying, gravure coating, offset coating, offset gravure, roll coating using an offset transfer roll coater, reverse roll coating, air knife coating, curtain coating using a curtain flow coater, comma coating, Mayer bar coating, and other methods known in the art that are used for forming a cured layer. There are no limitations on the thickness of the release cured coating on the substrate, but it is preferably within the range of 0.01 to 3 μm, or 0.03 to 2 μm. This is because if the thickness of the release cured coating is equal to or greater than the lower limit of the above range, the adhesive substance is easily peeled off, whereas if the thickness is equal to or less than the upper limit of the above range, blocking is suppressed when the resulting release sheet is wound into a roll.

This composition is useful for forming a hardened layer that has excellent surface slipperiness and release properties against adhesive substances, and can be used particularly effectively as a release-resistant hardened coating agent for process paper, asphalt wrapping paper, and various plastic films.

Furthermore, the laminate has a release layer formed by curing the composition on at least one surface of the sheet-like substrate, and is characterized by having an adhesive layer on the release layer.

In particular, the release layer obtained by curing this composition has excellent release properties against other adhesive layers, and can therefore be used as a release layer for laminates including adhesive layers, such as process paper, adhesive packaging paper, adhesive tape, and adhesive labels. Specifically, by using this composition, a laminate can be obtained in which an adhesive sheet having an adhesive layer (or adhesive layer) on at least one side of a sheet-like substrate having a cured layer (release layer or release layer) formed by heat-curing this composition on at least one side of the sheet-like substrate is attached to the sheet-like substrate so that the adhesive layer is in contact with the cured layer.

The adhesive substance to be applied to this laminate includes various adhesives and various types of glue, and examples thereof include acrylic resin adhesives, rubber adhesives, silicone adhesives; acrylic resin adhesives, synthetic rubber adhesives, silicone adhesives, epoxy resin adhesives, and polyurethane adhesives. Other examples include asphalt, sticky foods such as mochi, glue, and chicken mochi.

On the other hand, the cured layer made of this composition, particularly when applied thickly, can be used as a slightly adhesive adhesive layer while retaining the same excellent peeling properties as when applied thinly, and is extremely useful in that it can be used as an adhesive layer for protective sheets, removable adhesive sheets, etc. Such an adhesive layer has the advantage of maintaining stable adhesion for a long period of time after application to an object, preventing misalignment or peeling, but also excellent removability even after application for a long period of time. It also has the advantage of being easy to reapply, and is less likely to cause deformation, whitening, or adhesive residue in the cured layer when the protective sheet is used for a long period of time.

A protective sheet or removable adhesive sheet having a cured layer made of this composition is used for applications such as attaching to the surfaces of components such as metal sheets, painted metal sheets, aluminum sashes, resin sheets, decorative steel sheets, polyvinyl chloride laminated steel sheets, glass sheets, etc. to protect them when transporting, processing, or curing them. It can also be suitably used as a protective sheet in the manufacturing process of various liquid crystal display panels (also called monitors or displays), the distribution process of polarizing plates, the manufacturing process and distribution process of resin components for various machines such as automobiles, food packaging, etc.

Similarly, a protective sheet having an adhesive layer made of a cured layer of the present composition is easy to reposition, and is therefore suitable as a protective sheet for various displays, such as the following. The protective sheet of the present invention is used for purposes such as preventing the surface from being scratched, being stained, preventing fingerprints, being antistatic, being antireflective, and preventing peeping, during the manufacture, distribution, and use of these displays.

Specifically, the laminate that is the surface protection sheet can be obtained by using the present composition, and is constructed by attaching a release sheet having a release layer on at least one surface of the sheet-like substrate to the sheet-like substrate, the release layer being in contact with the cured layer, the release sheet being in contact with the cured layer, the release layer being in contact with the cured layer.

The curable organopolysiloxane composition and laminate of the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples. The viscosity in the examples is the value at 25°C measured using a Brookfield DV1 rotational viscometer in accordance with JIS K 7117-1:1999 "Plastics - Liquid, emulsion or dispersion resins - Method for measuring apparent viscosity using a Brookfield rotational viscometer."

The release sheets were prepared and evaluated as follows:

<Method of producing release sheet>
Using a printability tester [RI-2, manufactured by Akebono Seisakusho Co., Ltd.], the curable organopolysiloxane composition was applied to the surface of the substrate so as to give a siloxane equivalent of 0.6 g/ ^m2 . After application, the composition was heated in a hot air circulating oven at 120°C for 30 seconds to produce a release sheet having a release cured coating on the surface of the substrate.

<Aging of release sheet (pressing treatment)>
A part of the release sheet prepared by the above method was left unloaded under conditions of 23°C and 65% RH to be used as an "untreated release sheet". The other release sheet was treated under conditions of 23°C and 65% RH at a pressure of 20 g/ ^cm2 for 20 hours to be used as a "press-treated release sheet".

<Peel resistance of adhesive substance>
An acrylic adhesive [Olivine BPS5127, Toyo Ink Co., Ltd.] was uniformly applied to the surface of the release cured film using an applicator to a wet thickness of 70 μm, and dried at 70° C. for 2 minutes. Then, a double-sided art-coated paper (Kobayashi Create Co., Ltd.) was laminated thereon, and a load of 20 g/cm ² was applied and the laminate was left for 1 day under conditions of 25° C. and 60% humidity. Next, a tensile tester was used to measure the peel strength when the laminated paper was pulled in the 180° direction at a speed of 0.3 m/min. It should be noted that the peel strength is required to be 150 mN/50 mm or less for both the untreated release sheet and the press-treated release sheet.

<Heavy peeling rate>
The heavy peeling ratio was calculated by the following formula, by measuring the peeling resistance of the press-treated sample and the untreated sample after the above aging process.
Heavy release rate = (peel resistance of press-treated release sheet/peel resistance of untreated release sheet)
The heavy peeling ratio is required to be 1.10 or less.

<Residual adhesion rate>
Adhesive tape No. 31B manufactured by Nitto Denko Corporation was attached to the release sheet, and the tape was left at 70°C for 20 hours under a load of 20 g/ ^cm2 . The adhesive tape was then peeled off, and the peeled tape was attached to a stainless steel plate, and the tape was left in the air at 25°C and 60% humidity for 30 minutes under a load of 20 g/ ^cm2 . The adhesive tape was then pulled at an angle of 180° and a peeling speed of 0.3 m/min using a tensile tester [Tensilon universal tester manufactured by A&D Co., Ltd.] to measure the force required for peeling (gf1). In addition, as a blank test, the above tape was attached to a Teflon (registered trademark) sheet in the same manner as above, and the force required for peeling the adhesive tape (gf2) was measured in the same manner as above. From these values, the residual adhesion rate (%) was calculated according to the following formula.
Residual adhesion rate (%) = (gf1/gf2) x 100
The residual adhesion rate is required to be 90% or more.

<Examples 1 to 6 and Comparative Examples 1 to 19>
The following components were mixed uniformly to prepare curable organopolysiloxane compositions as shown in Tables 1 to 4. The content of component (D) in the tables is the amount of platinum in component (D) that is 100 ppm by mass relative to the total amount of components (A) to (C). In addition, "component (A)/component (B)" in the tables indicates the ratio of the content of component (A) to the content of component (B), and "SiH/CH ₂ ═CH" indicates the ratio of the number of moles of silicon-bonded hydrogen atoms in component (C) to the total number of moles of alkenyl groups in components (A) and (B). The properties of release sheets produced using the curable organopolysiloxane compositions thus prepared were measured, and the results are shown in Tables 1 to 4.

As component (A), the following components were used:
(a-1): A dimethylsiloxane-methylhexenylsiloxane copolymer having a viscosity of 200 mPa·s and both molecular chain terminals blocked with dimethylhexenylsiloxy groups (content of hexenyl groups converted to vinyl groups=1.15% by mass).

For comparison of component (A), the following components were used:
(a-2): Dimethylsiloxane-methylhexenylsiloxane copolymer having a viscosity of 200 mPa·s and both molecular chain terminals blocked with dimethylvinylsiloxy groups (vinyl group and hexenyl group content calculated as vinyl group=1.10% by mass)
(a-3): Dimethylsiloxane-methylvinylsiloxane copolymer having a viscosity of 350 mPa·s and both molecular chain terminals blocked with dimethylvinylsiloxy groups (vinyl group content = 0.94% by mass)
(a-4): Dimethylsiloxane-methylhexenylsiloxane copolymer having a viscosity of 350 mPa·s and both molecular chain terminals blocked with trimethylsiloxy groups (content of hexenyl groups converted to vinyl groups=1.25% by mass)

As component (B), the following components were used:
(b-1): A dimethylsiloxane-methylvinylsiloxane copolymer having a viscosity of 5,000 mPa·s and both molecular chain terminals blocked with trimethylsiloxy groups (vinyl group content = 0.15% by mass).
(b-2): Dimethylsiloxane-methylvinylsiloxane copolymer having a viscosity of 40,000 mPa·s and both molecular chain terminals blocked with trimethylsiloxy groups (vinyl group content = 0.15% by mass)

For comparison of component (B), the following component was used:
(b-3): Dimethylsiloxane-methylvinylsiloxane copolymer having a viscosity of 35,000 mPa·s and both molecular chain terminals blocked with trimethylsiloxy groups (vinyl group content=0.5% by mass)
(b-4): Dimethylsiloxane-methylvinylsiloxane copolymer having a viscosity of 8,000 mPa·s and both molecular chain terminals blocked with trimethylsiloxy groups (vinyl group content = 0.31% by mass)
(b-5): Dimethylpolysiloxane having a viscosity of 350 mPa·s and both molecular chain terminals blocked with trimethylsiloxy groups; (b-6): Dimethylpolysiloxane having a viscosity of 5,000 mPa·s and both molecular chain terminals blocked with trimethylsiloxy groups; (b-7): Dimethylpolysiloxane having a viscosity of 10,000 mPa·s and both molecular chain terminals blocked with trimethylsiloxy groups; (b-8): Dimethylpolysiloxane having a viscosity of 2,300 mPa·s and both molecular chain terminals blocked with dimethylhydroxysiloxy groups. (b-9): Dimethylpolysiloxane having a viscosity of 13,500 mPa·s and terminated at both molecular chain ends with dimethylhydroxysiloxy groups (b-10): Dimethylpolysiloxane having a viscosity of 4,000 mPa·s and terminated at both molecular chain ends with dimethylhydroxysiloxy groups (b-11): Dimethylpolysiloxane having a viscosity of 2,000 mPa·s and terminated at both molecular chain ends with dimethylvinylsiloxy groups (vinyl group content = 0.23% by mass)
(b-12): Dimethylpolysiloxane having a viscosity of 10,000 mPa·s and both molecular chain terminals blocked with dimethylvinyl groups (vinyl group content = 0.13% by mass)

As component (C), the following component was used:
(c-1): Methylhydrogenpolysiloxane having a viscosity of 20 mPa·s and both molecular chain terminals blocked with trimethylsiloxy groups (content of silicon-bonded hydrogen atoms=1.58% by mass)

As component (D), the following component was used:
(d-1): 1,3-divinyltetramethyldisiloxane solution of platinum 1,3-divinyltetramethyldisiloxane complex (platinum content = 6,500 ppm)

As component (E), the following component was used:
(e-1): 1-ethynyl-cyclohexan-1-ol

The results in Tables 1 to 4 show that when a dimethylsiloxane-methylvinylsiloxane copolymer with a vinyl group content of more than 0.3% by mass and both molecular chain terminals blocked with trimethylsiloxy groups was used as component (B) (Comparative Examples 1 and 2), the peel resistance after press processing became heavy, i.e., the peeling became heavy. Also, even when a dimethylsiloxane-methylvinylsiloxane copolymer with a vinyl group content of 0.3% by mass or less and both molecular chain terminals blocked with trimethylsiloxy groups was used as component (B), it was found that it was difficult to achieve a sufficiently light peeling when the component (A)/component (B) ratio was outside the range of 90/10 to 75/25 (Comparative Examples 14 and 17), and the residual adhesion rate was also found to decrease significantly (Comparative Examples 15, 16, 18, and 19). Furthermore, it was found that when dimethylpolysiloxane with both molecular chain ends blocked with trimethylsilyl groups (Comparative Examples 3 to 5) and dimethylpolysiloxane with both molecular chain ends blocked with dimethylsilanol groups (Comparative Examples 6 to 8) were used as component (B), the tendency to heavy peeling was strong and the residual adhesion rate was significantly reduced. Furthermore, when a dimethylsiloxane-methylvinylsiloxane copolymer with a vinyl group content of 0.3 mass% or less and both molecular chain ends blocked with dimethylvinyl groups was used as component (B) (Comparative Examples 9 and 10), the heavy peeling rate and residual adhesion rate were good, but the peel resistance became heavy. Furthermore, when a dimethylsiloxane-methylhexenylsiloxane copolymer with hexenyl groups only on the side chains of the molecular chain was used as component (A) (Comparative Example 13), the tendency to heavy peeling was strong and the residual adhesion rate was also low.

In contrast, the present invention (Examples 1 to 6) showed low peel resistance, low heavy peel rate when the release sheet after hardening was pressed, and no decrease in residual adhesion rate.

The curable organopolysiloxane composition of the present invention is suitable as a composition for forming a peelable cured film, since it can form a cured film with stable release performance on adhesive substances without impairing their adhesive performance. That is, even when the composition is coated on a sheet-like substrate, such as polyethylene laminated paper, and the release sheet obtained by curing the composition is laminated and pressed, the release layer made of the composition has a small release difference from that of the unpressed composition, has stable release performance, and is capable of suppressing a decrease in the adhesiveness of the adhesive substance, so that a laminate having a release layer and an adhesive layer using the above composition, such as a peelable adhesive tape/sheet, can be provided.

Claims

(A) a linear organopolysiloxane having a viscosity at 25°C of 20 to 1,500 mPa·s and having higher alkenyl groups having 4 to 12 carbon atoms at the molecular chain terminals and in the side chains;
(B) a linear organopolysiloxane having a viscosity at 25°C of 3,000 to 50,000 mPa·s, having at least two alkenyl groups having 2 to 12 carbon atoms per molecule only at side chains of the molecular chain, and the content of said alkenyl groups in component (B) calculated as vinyl groups (CH 2 ═CH-) is 0.1 to 0.3 mass %;
(C) an organohydrogenpolysiloxane having at least two silicon-bonded hydrogen atoms in each molecule, and (D) a catalytic amount of a hydrosilylation reaction catalyst,
a mass ratio of the component (A) to the component (B) {component (A)/component (B)} is 90/10 to 75/25;
the ratio of the number of moles of silicon-bonded hydrogen atoms in said component (C) to the total number of moles of higher alkenyl groups in said component (A) and alkenyl groups in said component (B) is 0.5 to 5.0;
A curable organopolysiloxane composition.
2. The curable organopolysiloxane composition according to claim 1, wherein the higher alkenyl groups in component (A) are hexenyl groups, and the content of said hexenyl groups in component (A) calculated as vinyl groups (CH 2 ═CH-) is 0.5 to 3.0 mass %.
The curable organopolysiloxane composition according to claim 1 or 2, in which both ends of the molecular chain of component (B) are blocked with trialkylsiloxy groups.
The curable organopolysiloxane composition according to claim 1 or claim 2, which is used to form a peelable cured coating.
The curable organopolysiloxane composition according to claim 3, which is used to form a peelable cured coating.
A laminate having a cured layer formed by curing the curable organopolysiloxane composition according to claim 1 or 2 on at least one surface of a sheet-like substrate.
A laminate having a cured layer formed by curing the curable organopolysiloxane composition described in claim 3 on at least one surface of a sheet-like substrate.
A laminate having a release layer formed by curing the curable organopolysiloxane composition according to claim 1 or claim 2 on at least one surface of a sheet-like substrate, and having an adhesive layer on the release layer.
A laminate having a release layer formed by curing the curable organopolysiloxane composition described in claim 3 on at least one surface of a sheet-like substrate, and having an adhesive layer on the release layer.