DE2425186C2 - Articles with a backing, a self-adhesive organopolysiloxane layer on the backing, and a peelable anti-stick layer on the organopolysiloxane layer - Google Patents

Description

(OH) ₅ (OR ² ),

wherein R ^{2 is} selected from alkyl radicals with 1 to 8 carbon atoms, cycloalkyl radicals with 5 to 7 carbon atoms in the ring, lower alkenyl radicals with 2 to 8 carbon atoms, mononuclear aryl radicals. lower alkyl-substituted mononuclear aryl radicals having 1 to 6 carbon atoms in the alkyl group and the halogenated derivatives of the above radicals, OR ^{2 is} a lower alkoxy radical having 1 to 8 carbon atoms per radical, 5 is a value of 1.0 to 1.7, q is a value from 0 to 1, / · has a value from 0 to 1 and the sum of q and r has a value from 0.01 to 1.

The invention relates to an article with a uniform coherent pad, a self-adhesive organopolysiloxane layer on at least one side of this base and one peelable An anti-stick layer comprising a film coated with a silanol-terminated dimethylpolysiloxane liquid is coated on the self-adhesive organopolysiloxane, the self-adhesive organopolysiloxane is the condensation product of a mixture comprising an orgnaopolysiloxane resin and at least one Contains alkylarylpolysiloxane rubber.

An article of the above type is described in US Pat. No. 2,857,356. This well-known article is the self-adhesive organopolysiloxane is the condensation product of a mixture of a hydrolysis product a hydrolyzable trialkylsilane and an alkylsilicate, either in the monomeric or polymeric state is present, this Kohydrolysisproduct a large number of silicon-bonded hydroxyl groups and a linear, high viscosity liquid organopolysiloxane, the terminal, silicon-bonded hydroxyl groups. This liquid organopolysiloxane can also Contain phenyl groups. The article according to the above US-PS is intended, among other things, to have strong liability exhibit.

In such a conventional self-adhesive organopolysiloxane, however, the peel strength is between the polysiloxane and the peelable anti-adhesive layer so large that the anti-adhesive layer is often removed when it is peeled off rips. The peel strength immediately after folding is high and it is in the On the order of about 300 g / cm.

The present invention was therefore based on the object of the article of the type mentioned to the effect that the anti-adhesive layer is easier to peel off.

According to the invention this object is achieved in that the alkylarylpolysiloxane rubber is a mixture of one. Gum having a viscosity of about 200 000 to about 15 000 000 centipoise at 25 ° C and diphenylsiloxane, dimethylsiloxane and silanol and a rubber having a viscosity of about 200 000 to about 15 000 000 centipoise at 25 ⁰ C and methylvinylsiloxane, diphenylsiloxane - and is di-methylsiloxane units.

The peel strength of the article according to the invention is on the order of about 50 g / cm and this prevents the anti-adhesive layer from tearing. This easier peelability is also after accelerated oven aging, and the adhesion of such tapes to stainless test panels Steel is excellent even after prolonged oven aging.

The adhesion of the coated with a self-adhesive organopolysiloxane according to the invention Article on a substrate is made by separating the peelable anti-adhesive layer from the layer from the self-adhesive organopolysiloxane and applying the article with the layer of the self-adhesive Organopolysiloxane on the substrate.

The peelable anti-adhesive layer comprises a film coated with a silanol-terminated dimethylpolysiloxane liquid is coated, the film forming a uniformly cohesive basis of a natural substance, such as. B. tissue or Paper. It advantageously has a thickness in the range from about 0.0005 to about 0.075 mm.

The foil is on the side that sem self-adhesive Organopolysiloxane is to be turned with the

linear liquid dimethylpolysiloxane coated that contains silicon-bonded hydroxyl end groups and preferably has a viscosity of 1,000 to 10,000,000 Centipoise at 25 ° C. Suitable materials are those of the formula

has the above meaning The polymer chains can also contain some molecules, the monoorganosiloxane units the following formula:

HO-

-SiO-CH ₃

-H

10

where ρ is an integer varying from 300 to 5260. Particularly preferred is a linear diorganopolysiloxane having a viscosity of 12,000 to 90,000 in which the value of ρ varies between 770 and 1,350. In the most preferred embodiment, the linear diorganopolysiloxane has a viscosity of 15,000 to 35,000 centipoise corresponding to a value of p, which varies between 825 and 11 00 .

The dimethylpolysiloxane liquids can be produced by one of the known processes.

The alkylarylpolysiloxane rubbers used to produce the self-adhesive organopolysiloxane advantageously contain on average about 1.85 to 2.01 silicon-bonded methyl and phenyl radicals per Silicon atom, these radicals via silicon-carbon bonds are bonded to the silicon and have about 2 to about 75 phenyl-silicon bonds in the rubber, based on the total number of silicon bonds to organic radicals and also about 0.001 up to 0.25% by weight of silicon-bonded hydroxyl groups or alkoxy groups are present.

In general, these rubbers consist primarily of diorganosiloxane units, but they can also Contain small amounts of monoorganosiloxane units and triorganosiloxane units. A special one useful type of alkylarylpolysiloxane rubber is the linear polymer of the following formula

R ¹ OI-Si-O
R.

R ¹

45

wherein R is selected from methyl, phenyl and vinyl and η has a value of at least 500, e.g. B. from about 5000 to 500,000 or more and R ^{1 is} selected from hydrogen, alkyl of 1 to 8 carbon atoms such as methyl, ethyl, propyl, t-butyl, hexyl or octyl and vinyl. The polysiloxane within the scope of the above formula can comprise a variety of molecules of different molecular weights and different R and R 'substituents, so long as the average formula of the mixture falls within the scope of the above formula.

In addition to the linear, silafiol or alkoxy end groups containing diorganopolysiloxanes of the above formula, the rubber can also contain some Contain molecules that contain linear diorganosiloxane chains that have triorganosiloxane units at one end have the following formula:

(R) ₃ SiO ₀₅

while the other end of the chains is terminated by alkoxy or silanol groups, where R is the where R has the above meaning

In either case, the alkylarylpolysiloxane rubbers have a viscosity in the range of about 200,000 to 15,000,000 centipoise as noted above and preferably a viscosity in the range of about 500,000 to 12,000,000 centipoise, the amount of silicon-bonded hydroxyl and / or alkoxy groups at least from 0.001 to 0.25% by weight and preferably in the range of about 0.005 to 0.1 weight percent The various alkylarylpolysiloxane rubbers are known

It is essential to the invention that the alkylarylpolysiloxane rubber contain phenyl in order to achieve optimum self-adhesive properties. If z. For example, if a mixture of phenyl and methyl groups is used, then the number of silicon-bonded phenyl groups should be kept in a range such that for each 2 to 75 phenyl groups bonded directly through carbon-silicon bonds, 98 to 25 silicon-bonded methyl groups available. For example, a preferred range is from about 5 to about 15 phenyl groups per 95 to 85 methyl groups.

The organopolysiloxane resin used to produce the self-adhesive organopolysiloxane is a Polymer of two or more siloxane units with the following average formula :.

(OH) ₈ (OR ² ), RjSi O ₄ -, -, -,

wherein R ^{2 is} selected from alkyl radicals with 1 to 8 carbon atoms, cycloalkyl radicals with 5 to 7 carbon atoms in the ring, lower alkenyl radicals with 2 to 8 carbon atoms, mononuclear aryl radicals, lower alkyl-substituted mononuclear aryl radicals with 1 to 6 carbon atoms in the alkyl group and halogenated. Derivatives of the above radicals, OR ^{2 is} a lower alkoxy group containing 1 to 8 carbon atoms per radical, s has a value from 1 to 1.7 and preferably a value from 1.05 to 1.45, q has a value from 0 to 1 and preferably has a value of 0.2 to 0.55, r has a value of 0 to 1 and preferably a value of 0.2 to 0.55 and the sum of q and r has a value of 0.01 to 1 , 0 and preferably has a value of 0.2 to 0.55.

Examples of the siloxane units used in the organopolysiloxane resins may be present are the following:

C ₆ H ₅ SiO ₃ Z ₂ ,

CH ₃ SiO ₃ Z ₂ /

(CH ₃ ) CeH ₅ SiO,

(C ₂ Hs) ₂ SiO,

C ₃ H ₇ SiO ₃ Z ₂ ,

(C ₃ H ₇ ) C ₆ H ₅ SiO,

(CH ₂ = CH) CH ₃ SiO,

(CF ₃ CH ₂ CH ₂ ) CH ₃ SiO,

C ₆ HnSiO ₃ Z ₂ ,

CF ₃ C ₆ H ₄ SiO ₃ Z ₂ ,

CH ₃ C ₆ H ₄ SiO ₃ Z ₂ and

(C ₆ Hs) ₂ SiO,

(CH ₃ J ₂ SiQ,

C ₂ H ₅ SiO ₃ Z ₂ ,

(C ₂ H ₅ ) C ₆ H ₅ SiO,

(C ₃ H ₇ J ₂ SiO,

CH ₂ = CHSiO ₃ Z ₂ ,

CH ₂ = CHCH ₂ SiO ₃ Z ₂ ,

ClCH ₂ CH ₂ SiO ₃ Z ₂ ,

CI ₂ C ₆ H ₃ SiO ₃ Z ₂ ,

(C ₆ H ₅ ) CF ₃ CH ₂ CH ₂ SiO,

C ₆ H ₅ CH ₂ SiO ₃ Z ₂

In particular, R ^{2 is} selected from lower ones

• alkyl radicals such as methyl, ethyl, propyl, butyl and octyl; Cycloalkyl radicals having 5 to 7 carbon atoms in the ring, such as cyclopentyl, cyclohexyl and cycloheptyl; lower alkenyl groups such as vinyl and allyl; mononuclear aryl radicals such as phenyl, tolyl and XyIyI; lower alkyl-substituted mononuclear aryl radicals such as benzyl and phenylethyl and the halogenated derivatives of the above radicals, e.g. B. chloromethyl, beta-chloroethyl, chlorophenyl, dibromophenyl and trifluoromethylethyl. ^{R 2} is preferably selected from methyl, ethyl and phenyl.

The lower alkoxy radical OR ² is selected from lower alkoxy radicals having 1 to 8 carbon atoms, such as methoxy, ethoxy, propoxy and isopropoxy, which at the same time represent the preferred embodiments for this radical.

The ratio of the organic substituents R ² to the silicon atoms in the above-described siloxane resin is in the range from 1.0: 1 to 1.7: 1 and preferably in the range from 1.05: 1 to 1.45: 1.

In addition, the resin should be at least 0.25% by weight Contain silicon-bonded OH and / or (OR) groups. The resin can be much higher Have percentage content of OH groups and it can contain at least 5 wt .-% OH groups.

It has been found advantageous to add about 0.5 to about 6 parts by weight of the alkylarylpolysiloxane rubber per Part by weight of the organopolysiloxane resin to be used. Preferably in the context of the present Invention about 1 to about 3 parts by weight of the alkylarylpolysiloxane rubber per part by weight of the organopolysiloxane resin used.

The self-adhesive organopolysiloxane is usually in layer thicknesses from about 0.02 to about 0.125 mm and preferably from about 0.025 to about 0.075 mm used. Of course, other layer thicknesses can also be used, depending on the intended application of the self-adhesive article.

The uniformly cohesive base to which the self-adhesive organopolysiloxane is applied can be selected from a variety of substrates depending on the intended application of the article. The self-adhesive article can be an adhesive tape in the form of a rolled-up roll, be a foil or any other desired configuration.

The base can consist of any material suitable for carrying the self-adhesive adhesive. Examples of such suitable materials are glass fabric, silicone-coated glass fabric, synthetic polymeric films such as polyimides, polyamides, silicones, polytetrafluoroethylene and polychlorotrifluoroethylene, polyethylene, polypropylene, copolymers of acrylonitrile, butadiene and styrene, polyesters such as polyethylene terephthalate, such as metal polymers and acetal polymers, such as are metallic substrates Aluminum foil and copper foil as well as polymer coated papers such as polyethylene coated papers are useful. The articles of the invention can be made by mixing the organopolysiloxane resin with the alkylarylpolysiloxane rubber and cocondensing or reacting the two with one another at elevated temperatures. In general, the resin and the rubber at temperatures between about 100 and about 15O ⁰ C for V2 to 6 hours to be reacted with each other, until a product of the desired tack and cohesive strength obtained. After the rubber and resin have reacted with each other, that can

Dissolve in an aromatic solvent, such as benzene, toluene or xylene, to produce a product Form solution that is about 2,000 to 200,000 centipoise. Generally the solutions contain one Solids content from about 40 to about 70% by weight.

The solution can then be applied to the desired support in any suitable conventional manner as by brushing, spraying, coating under Using a knife and the like. The organic solvent is then evaporated and a A film of self-adhesive organopolysiloxane forms on the surface.

It may be desirable to incorporate a free radical-generating peroxide catalyst into the mixture to be reacted in order to make the self-adhesive organopolysiloxane thermosetting, which enhances the adhesive properties at elevated temperatures solvent further heated to temperatures of about 150 to about 250 ⁰ C Some suitable organic peroxide catalysts include benzoyl peroxide and dicumyl peroxide. The peelable anti-adhesive layer made of a film coated with silanol liquid, e.g. B. a paper film or a material such as is suitable for the documents described above, can be applied to the self-adhesive organopolysiloxane. The self-adhesive organopolysiloxane adheres to the coated anti-adhesive layer in an easily removable manner. The layer protects the surface of the organopolysiloxane from contamination and from sticking to undesired substrates until this layer is later removed prior to use. This can be done by carefully peeling it off without damaging the self-adhesive organopolysiloxane. The release film is removed from the self-adhesive organopolysiloxane without leaving any residue of the film, and the article is then pressed against the surface to which it is intended to adhere.

The invention is explained in more detail below with the aid of examples in which the amounts are by weight unless otherwise stated.

example 1

Adhesive tapes according to the present invention were made

Invention made by having an approximately 0.075 mm thick polyethylene terephthalate tape as a base a self-adhesive siloxane composition comprising the following ingredients:

A. 50 parts of resin solids of a resin copolymer, based on 1 mole of SiO ₂ , reacted with 0.5 to 0.6 moles of (CH ₃ ) 3SiO./2,

B. 38 parts of a polysiloxane copolymer rubber containing silanol end groups, which is 5.3 mol% Diphenylsiloxane and 94.7 mol% of dimethylsiloxane contained the polymer having a viscosity of more than 10,000,000 centipoise and

C. 12 parts of a copolymer rubber with 0.2 mole percent methylvinylsiloxane, 5.3 mole percent diphenylsiloxane and 94.5 mole percent dimethylsiloxane having a viscosity greater than 10,000,000 centipoise.

Ingredients A, B and C were prepared as a solution in xylene at 55% solids. It became a primary organic amine in an amount, .vpn 10 to 20 ppm, based on the total solids content.,

used to mix the above at the reflux temperature (145 to 155 ° C) for a time of 1/2 to 6 Catalyze hours. It became about 1 part of benzoyl peroxide per 100 parts of silicone solids added.

The xylene solution was applied to the base by coating using a knife. The coated article is then heated for 2 minutes at 90 to 95 ⁰ C, to evaporate the solvent and then was heated for 5 minutes on 150 175 ° C in a forced air oven, to cause the reaction with the benzoyl peroxide. The self-adhesive coating was about 0.025 mm thick.

A sheet of paper coated with a commercially available silanol-terminated dimethylpolysiloxane liquid (Viscosity 16,000 centipoise at 25 ° C) was coated as above The resulting coated tape is pressed on using a 4.5 kg roller. The peel strength between the self-adhesive organopolysiloxane and the peelable sheet was then with a Scott tester measured with two mounting clamps. The separation of the release sheet was done by hand started and then the part with the self-adhesive organopolysiloxane and the polyester backing on the one clamp is attached and the release sheet is attached to the other clamp. The top clamp was on one The scale was attached which indicated the force and the lower clamp was attached to a mechanism which moved away from the upper clamp at a rate of exactly 30 cm / min. The peel strength the adhesive from the release sheet was only about 50 g / cm. It follows that the peelable sheet can be easily removed from the adhesive.

The article coated with the self-adhesive organopolysiloxane was after removal of the The release sheet was tested for peel strength from a stainless steel panel according to ASTM Standard D-1000. This test is similar to that described above, with the steel plate on one of the Clamps of the Scott tester is attached. Even after the oven was aged for two weeks, the Peel values were high and were between about 400 and 470 g / cm.

In addition had protected with a peelable layer ribbons, which were prepared according to the present invention, even after two weeks of aging oven at 6O ⁰ C nut has a peel strength of about 50 g / cm when applying a pressure of about 0.0175 kg / cm ² .

Comparative example 1

For comparison purposes, the method of Example 1, however, repeats a silanol end group instead of the alkylarylpolysiloxane rubber used there having methyl rubber used. The peel strength against the release sheet was greater than about 300 g / cm and the paper kept tearing when trying to remove it from the adhesive-coated Peel off the pad.

Example 2

The procedure of Example 1 was repeated, but using the following self-adhesive organopolysiloxane used:

A. 50 parts of resin particles of a resin copolymer, based on 1 mole of SiO ₂ , reacted with 0.5 to 0.6 moles of (CH ₃ ) 3SiO, / 2,

B. 40 parts silanol-terminated polysiloxane exhibiting at 5.3 MOI ⁰ Zo Diphenyisiloxan and 94.7 mol% dimethyl siloxane, wherein the copolymer had a viscosity of more than 10,000,000 centipoise, and

C. 10 parts of the following mixture:

(i) 72 parts of a polymer with 0.2 mole percent methylvinylsiloxane, 5.3 mole percent diphenylsiloxane and 94.5 mole percent dimethylsiloxane, the original viscosity being greater than Was 10,000,000 centipoise,

(ii) 18 parts of fumed silica with a surface area greater than 250 m ² / g,

(iii) 8.5 parts of a processing aid, which consists of 30 mol% diphenylsiloxane and 70 mol% Was composed of dimethylsiloxane and had a viscosity of 30 to 60 centipoise and

(iv) 2.5 parts octamethylicyclotetrasiloxane.

Ingredients A, B and C above were made into a solution in xylene at 60% total solids processed. An alkali catalyst such as NaOH was used in an amount of 10 to 25 ppm based on the total solution weight, at reflux temperatures of 145 to 155 ° C, used to form a To effect copolymer of the resin and the rubbers in a time of 1/2 to 6 hours. It became a Adhesive tape was obtained from which the release liner was easily removed without tearing.

The amount of silicon-bonded aryl groups in the copolymer rubber can also be varied. So when using 13 mol% Diphenyisiloxane and a layer about 0.028 mm thick self-adhesive organopolysiloxane on an approximately 0.075 mm thick polyethylene terephthalate film the very obtained low peel strength on the order of 5 g / cm a

Claims (2)

Patent claims: 1. Article with a uniform, cohesive Underlay, a self-adhesive organopolysiloxane layer on at least one side of this Backing and a peelable anti-adhesive layer comprising a film with a silanol end group containing dimethylpolysiloxane liquid is coated on the self-adhesive organopo- "> lysiloxane, the self-adhesive organopolysiloxane the condensation product of a mixture is an organopolysiloxane resin and at least contains an alkylarylpolysiloxane rubber, characterized in that the alkylarylpolysiloxane rubber a mixture of a rubber having a viscosity of about 200,000 to about 15,000,000 centipoise at 25 ° C and diphenylsiloxane, Dimethylsiloxane units and silanol end groups and a rubber having a viscosity of from about 200,000 to about 15,000,000 centipoise 25 ° C and methylvinylsiloxane, diphenylsiloxane and dimethylsiloxane units 2. Article according to claim 1, characterized in that the alkylarylsiloxane rubber on average contains about 1.85 to 2.01 silicon-bonded methyl and phenyl radicals per silicon atom, these residues via silicon-carbon bonds are bonded to the silicon and have about 2 to about 75 phenyl-silicon bonds in the rubber, based on the total number of silicon bonds to organic radicals and also about 0.001 to 0.25% by weight of hydroxyl groups or alkoxy groups bonded to silicon are present and the organopolysiloxane resin consists of units of the following average formula: