DE1696194C3 - Process for the production of organopolysiloxane-coated release paper - Google Patents

Description

R _a Si (CH ₃ ) ₃ - _a - O - [- (- SiRb (CH ₃ ) JO- O -), "(- Si (CH ₃ )., - O-)" -, "-] - Si (CH ₃ ) ^ ₀ Ra

where R is an alkylene radical, η is chosen so high that the viscosity at 2 ° C is at least 10 "cP, a ^ - 0, 1, 2 or 3, b = 1 or 2

and in the case of a = 0 a value from 2 to ^,> n

The other traps have a value from 0 to _m ,

(B) 20 to 50 parts by weight of Λ, ω-dihydroxypolydimethylsiloxane of at least 1000 cP viscosity at 2x) ° C and (C) 1 to 10%, based on the sum of the weights of the polysiloxanes (A) and (B). a ^ -Bis- (trimethylsiIoxy) -polymethylhydrogensiloxane with a maximum viscosity of 1000 cP at 20 ⁰ C, as a crosslinking agent a mixture of (D) 1 to 10%, based on the sum of the weights of the polysiloxanes (A), (B) and ( C), an organic peroxide and (E) 0.5 to 10%, based on (D), of a crosslinking accelerator from the series of heavy metal carboxylates, dialkyltin carboxylates, amines and quaternary ammonium compounds and the crosslinking of the paper coating by brief heating to 100 120 ⁰ C is carried out.

2. The method according to claim 1, characterized in that that polysiloxanes with vinyl or allyl radicals are used as alkenyl radicals R.

3. The method according to claim 1, characterized in that that dicumyl peroxide is used as the organic peroxide.

4. The method according to claim 1, characterized in that that dibutyltin dilaurate is used as crosslinking accelerator (E).

5. The method according to claim 1, characterized in that as a coating an organopoly siloxane mixture of (A) 62 to 67 parts by weight of a rt, i ') - bis (iriorganosiloxy) -polydiorganosiloxans of the formula given there, wherein R = Vi- nyl or allyl, a = 1 or 2, b - 1, m = 0 to 0.0015 η and η chosen so high that the viscosity at 2O ⁰ C for 10 to 10 »cP ', (B) 35-30 Parts by weight «,« wpihydroxypolydimethylstloxan of approximately 10 * cP viscosity at 20 ⁰ C and

(C) about 3 parts by weight of a, ro-bis (trimethylsiloxyVpolymethylhydrogensiloxane of about 15 cP viscosity at 20 ^° C., a.'s crosslinking agent

(D) and (E) 5 to 6 parts by weight Dieumylperoxyd and 8 to 10 parts by weight of dibutyltin dilaurate may be used and the crosslinking is carried out at about 120 ⁰ C.

The invention relates to the production of separating

\ a papier, that is, from paper whose surface passes through

impregnation or coating has been modified in such a way that

that sticky substances applied to it are not or only cling insignificantly.

It has long been known that one can get to this

Purpose paper with organopolysüoxaneij. usually in solution or in the form of an aqueous emulsion of such a solution, soak, brush or spray. The choice of the siloxanes to be used for this is important in addition to the adhesion-reducing effect

«There are a number of other requirements to be observed, especially if the paper is used to temporarily cover the adhesive side of self-adhesive foils and ribbons intended to serve. In this case, the adhesive properties of the foils can also be used for a long time

Contact with the backing paper is not significantly _verringer * _are, the paper is easily possible be removed from the adhesive layer of the _{films] ίβχ} ^ _{si and the} i _{ox. in layer should adhere} firmly to your paper backing. At the same time, however, this should

Siloxane layer should be flexible enough to make it home Bending or creasing the paper does not tear or crumble.

Often times it is also desirable that the Hafuings adversity limited to one side of the release paper

remains so that the other can still be glued or printed with other material.

To solve this problem, several proposals have been made so far, which agree that one applies organopoiysiloxane mixtures to be crosslinked by brief heating, which essentially lend are composed of a \, / «- dihydroxy- or x / M-dialkoxypolydiinetbylsiloxan.einemMethylhydrogenpolysiloxan or organopolysiloxane resin or both last-mentioned polysiloxanes at the same time and one Crosslinking accelerator, for example a zinc, cobalt, tin or dialkyltin sa'i / a carboxylic acid

Those with such coating agents !! release papers obtained are with respect to those listed above Requirements, however, not satisfactory, be it that they have too great a force to detach require a covered adhesive film, be it that the adhesive strength of the film after peeling off the release paper is significantly reduced compared to the original value.

A paper coating process has now been found which achieves the desired property profile, namely low effort when peeling off the release paper, largely maintaining the bond strength of a covered adhesive layer, good anchoring and flexibility of the paper coating, to an unprecedented degree. This process for the production of release paper by applying a coating that reduces the adhesion of sticky substances to a paper surface using a crosslinkable organic poly-

i 696

ijloxan mixture, adding known crosslinking agents immediately before the application of the coating and subsequent heating of the coated therewith Paper is characterized in that the organopolysiloxane mixture from (A) is 50 to 80 parts by weight of a *, w-bis (triorganosiloxy) polydiorganosiloxane the formula

R _e Si (CH ₃ ) ₃ - «- O ■ [- (- SiR ₆ (CH ₃ )," - O -) _m

(- Si (CH ₃ J ₈ - O -) " _m -] - Si (CH ₃ ), - _n R"

10

where R denotes an alkenyl radical, η is selected so high that the viscosity at 20 ^° C. is at least 10 »cP, a = 0.1, 2 or 3, b = 1 or 2 and m

In the case of β = 0, find a value from 2 to the rest

Cases has a value of 0 to ^, (B) 20 to 50 parts by weight Α, ω-dihydroxypolydimethylsiloxane of at least 1000 cP viscosity at 20 ° C and (C) 1 to 10%, based on the sum of the weights of the polysiloxanes (A) and (B) a, w-bis- (trimethylsiloxy) -polyinethylhydrogensiloxan consists of at most 1,000 cP viscosity at 20 ⁰ C, as a crosslinking agent a mixture of (D) 1 to 10%, based on the sum of the weights of the polysiloxanes (a ), (B) and (C), of an organic peroxide and (E) 0.5 to 10%, based on (D), of a crosslinking accelerator from the series of heavy metal carboxylates, dialkyltin carboxylates, amines and quaternary ammonium compounds is used and the crosslinking of the Paper coating is carried out by brief heating to 100 to 12O ^{0 C.}

Preferably to be used as component (A) is one whose alkenyl resle R are vinyl or allyl residues, whose viscosity is 10 ⁷ to 10 ⁸ cP at 20 ⁰ C and in which the number a = 1 or 2, the number b - \ and

the quotient '"is one of the values from 0 to 15-ICh ⁴

Has; as component (B) a viscosity of approximately 10 cP at 20 ° C .; as component (C) a those of 15 cP at 20 ° C. The weight ratio (A): (B): (C) of these three mixture components is preferably in the range from 62: 35: 3 to 67: 30: 3.

As examples of component (D) of the crosslinking agent combination to be used according to the invention Benzoyl peroxide, dichlorobenzoyl peroxide, tert-butyl peroxide and preferably dicumyl peroxide may be mentioned. Examples of the metal compounds to be used as component (E) are the lead, cobalt, Zinc, manganese, zirconium, cerium and tin salts of higher Fatty acids, dioctyl tin maleate, dibutyl tin diacetate and preferably dibutyl tin dilaurate. The proportions are variable within wide limits; they are preferably to be dimensioned in such a way that the; Total mixture each 100 g of the polysiloxanes (A), (B) and (C) 5 to 6 g of peroxide (D) and 8 to 10 g of crosslinking accelerator (E) contains. These two components (D) and (E) can be used together in an inert solvent, e.g. B. xylene are dissolved.

Likewise, although it is not essential for the process, but advantageous for its convenient implementation, the mixture of polysiloxanes (A), (B) and (C) in an inert solvent such as toluene, xylene, petroleum ether, trichlorethylene or perchlorethylene initially in such an amount to solve that you get a stock solution with 30 to 40 percent by weight poly- «loxane for storage. The procedure then generally continues to dilute this stock solution for use and add the crosslinking agent mixture. It then takes ^{several hours at 20 °} C. until the solution that is ready for application to the paper thickens noticeably. With this solution, by coating the paper in a thin layer, for example by roller or knife coater and, by heating the thus coated paper is preferably 120 ^J C networking, scnon case is completed after one minute.

The speed and for the so-called migration resistance Significant completeness of the networking is to be regarded as surprising; she was according to the current state of experience, at least with regard to the supporting polymerization reaction of the unsaturated substituents of the polysiloxane (A) is not to be expected. Just as little was to be foreseen that the paper coating carried out according to the invention 2u a considerable improvement with respect to the generally antagonistic properties of low peel force; d. H. low adhesion between release paper and adhesive, and extensive maintenance of adhesive strength, d. H. greatest possible Adhesion between the adhesive and the firm contact with it after the release paper has been peeled off brought surface of another object, leads.

In each of the following exemplary embodiments, which do not limit the claimed method Paper used as a backing is glassine with a square meter weight of about 40 g.

The measured values designated as "peel force" were determined as follows: A one-sided provided with a sticky coating, 24 mm wide Cellulose tape was coated by hand like this Side of the release paper pressed so that it is smooth and without the inclusion of air bubbles between the adhesive and Release paper attached. Then the tape was perpendicular to the interposition of a spring balance Paper surface peeled off at a speed of 10 cm per minute and the force required for this read on the spring scale.

To determine the “maintenance of adhesive strength” of the adhesive tape, the procedure described above was initially followed; then the glued-on tape between glass plates for 24 hours printed with ei.icr load of 10 g / cm ² against the release paper, the temperature being maintained in a series of experiments at 20 ⁰ C, in another at 70 ⁰ C. The adhesive tape was then peeled off the release paper, stuck to a chrome-plated and polished metal plate and peeled off from this again at an angle of 135 ° at a speed of 10 cm per minute with the interposition of a spring balance. Meanwhile, on the scales, the dem. Tape remaining bond strength read. The associated original bond strength, measured in the following cases as 240 to 235 g, was determined in such a way that an identical piece of tape was first glued to a clean glass plate, peeled off again and then subjected to the test described on the metal plate *. The quotient of the bond strength remaining after the action of the release paper and the original bond strength of the tape gives the amount of the bond strength maintenance.

In the following, "Tl." Means weight parts; all viscosity values are measured ^{at 20 ° C.}

example 1

To prepare a stock solution, mix 122 Tl. «,« - Bis ^ vinyldiraethylsUoxy ^ polydimethylsiloxane of 3 · W cP viscosity, 60 TJ. «, Ω-DihydroxypolyydJraiRthylsiloxan of 8-10 ^e cP viscosity, 6 parts. », Ω - bis (trimethylsiloxy) - polymethylhydrogensiloxane with a viscosity of 15 cP and 312 Tl. Xylene, the viscosity of this Stamralösup.g is 5 · 10 * cP.

Dilute 10 parts of it with 40 parts of toluene and add 1 part of a mixture of 20 parts of dicumyl peroxide, 33 parts of dibutyltin dilaurate and 57 parts of xylene. The solution obtained in this way is carried with a glass

squeegee in about 10 microns thick layer on the paper and then heat this 1 minute at 120 ° c. Peel force -Ig;

Maintenance of adhesive strength at 20 ^° C

172 g

= 71%;

242 g

10

Example 2

The vinyl compound used in Example 1 is replaced by 122 parts of an a, ca-bis (vinyIdimethylsiloxy) vinylmethylpolysiloxane the formula

CH ₃
i
CH ₃ -Si-O

CH = CH,

CH ₃

Si - CH ₃

CH-ClI ₂

»Lit - = 0.0015 and 4 · 10 'cP viscosity and proceeds ^a5

4 further, as described there. Stock solution viscosity = 57,000 cP; Peel force == 1 g;

Maintenance of adhesive strength at 2O ⁰ C

181_g 245 g

= 74%;

at 70 ⁰ C - ^ - = 67%. 245 g

Example 3

The vinyl compound used in Example 1 is replaced by 122Tl. a, w-bis (methyldiallylsiloxy) polydimethylsiloxane of 3.7 · 10 cP viscosity and proceed as described there. Stock solution viscosity = 64,000 cP; Peel force = 1 g;

Example 4

The 312 TI used to prepare the stock solution in Example 3 is replaced. Xylene by 525 TI. Trichlorethylene and otherwise proceeds as described there.

Stock solution viscosity = 1.5 x 10 ^s cP; Peel force = 2 g;

3S 179 E.

Holding force at 20 ⁰ C - - = 75%;

240 g

40

Maintenance of adhesive strength at 20 ^° C

210 g 244 g

= 86%;

35

at 70 ° C - Li = 70%. 244 g

CH ₂ = CH - CH ₂

CH ₃ - Si - O CH ₂ = CH - CH ₂

at 70 ⁰ C - ^ - = 79%. 243

Example 5

The vinyl compound used in Example 1 is replaced by 122Tl. a, w-Bi5i- (methyldiallyl $ i] oxy} · allylmetiiylpolysiloxane of the formula

CH ₂ - CH = CH ₂

I.
- Si - CH ₃

CH ₂ - CH - CH ₁₁

with - = 0.0015 and 3.4 · 10 'cP viscosity and ver η

also drives as described there. Stock solution viscosity = 48,000 cP; Peel force - lg;

Klebkrafterhaltung at 2O ⁰ C - = 84%;

244 g

at ₇ o ° C

244 g

67%.

Comparison

The ones described below, with siloxane mixtures Coatings carried out according to the prior art show those described at the outset Defects, namely a decrease in the adhesive strength of the adhesive film which decreases with the storage temperature

or one that is more than a power of ten that favors tearing of the film; n the stapling of the Release paper on the covered film. 1. 76Tl. α, ω-Dihydroxypolydimethylsupxan from

8 · 1Ο ^β cP viscosity and 6 Tl. «, W-bis- (trimethylsiloxy) -polymethylhydrogensiloxane of 15 cP viscosity were with 127Tl. Toluene mixed to a stock solution.

34Pcs. of which were 136TJ. Toluene and ITl. D'ibutyltin dilaurate mixed, and the resulting solution in the same way as described in Example 1, applied to the paper and heated.
Peel force = 2 g;

Maintenance of adhesive strength at 2O ⁰ C

161.5 g

240 g

^B - = 67%;

at 7O ⁰ C

240 g

= 40%.

2. An organopolysiloxane resin solution was used which, according to the customary method, was obtained by hydrolyzing an organochlorosilane mixture of 195 parts of _{CH 3 SiCl 3} , HTl. QH ₄ SiCl ₃ , 18Tl. (CH ₃ ), SiCl ₂ and

3 Tl. (CHj) ₃ SiCl in a mixture of 830 Tl. Water, 166 TI. Xylene and 166 parts of butanol and subsequent evaporation to 51 percent by weight organopolysiloxane content was prepared. 393 parts of this solution were mixed with 79 parts of a mixed hydrolysis product of 10 parts CH ₃ SiCl ₃ and 90 parts (CH ^ jSiCl ,, 12 parts α, ω-dihydroxypolydimethylsiloxane of 1000 cP and 8 parts λ, ω - bis - (Trimethylsiloxy) - polymethylhydrogensiloxane dissolved in 108 parts of isopropanol. This solution was diluted with 600 parts of toluene, then 12 parts of dibutyltin dilaurate were mixed in. Coating and heating were carried out as described in Example 1 with the resulting solution.
Peel force = 94g;

Maintenance of adhesive strength at 20 ^° C

and at 70 ⁰ C --5Ii =
241g

509613/83

Claims (1)

1 $ 96 194 claims: 1. A process for the production of release paper by applying a coating that reduces the adhesion of tacky substances to a paper surface using a solution of the crosslinkable organopolysiloxane mixture dissolved in an inert solvent, optionally also in the form of the solution of the crosslinkable organopolysiloxane mixture emulated in water, adding known crosslinking agents immediately before applying the coating and subsequent heating of the coated paper, characterized in that an organopolysiloxane mixture is used as the coating (A) 50 to 80 parts by weight of an α, cu-bis (triorganosiloxy) -polydiorganosiloxane of the formula