DE1696194A1 - Adhesive organopolysiloxane coating on paper - Google Patents

Description

Adhesion-resistant organopolysiloxane coating of paper The invention concerns the production of release paper, i. H. of paper whose surface is through Impregnation or coating is changed so that sticky substances are applied not or only insignificantly attached.

It has long been known that for this purpose paper with organopolysiloxanes, usually in solution or in the form of an aqueous emulsion of such solution, soak, brush or spray. For the choice of the siloxanes to be used here In addition to the liability-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 tapes. In this case, the adhesive strength of the foils, even after prolonged contact with the masking paper, is not essential be reduced, the paper should be as easy as possible from the adhesive layer of the foils can be peeled off, and the siloxane layer should be firmly attached to its paper backing be liable. At the same time, however, this siloxane layer should be flexible enough to allow it does not tear or crumble when the paper is bent or creased.

Often it is also desirable that the non-liability is based on a The side of the release paper remains limited so that the other can work well with the other Can stick or print material.

To solve this problem, several proposals have been made so far, which agree that organopolysiloxane mixtures to be crosslinked by brief heating uses, which are essentially composed of an α, # - dihydroxy or α, # - dialkoxypolydimethylsiloxane, a methylhydrogenpolysiloxane or Organopolysiloxane resin or both last-mentioned polysiloxanes at the same time and one Crosslinking accelerator, for example a zinc, cobalt, tin or dialkyltin salt a carboxylic acid.

The release papers obtained with such coating agents are with regard to the requirements listed above, however, not satisfactory, be it that it has too great a force to detach it from an adhesive film covered with it require, be it that the adhesive strength of the film after peeling off the release paper is significantly reduced from the original value.

It has now been found a paper coating process which Desired property profile, namely little effort when peeling off the release paper, extensive preservation of the Bond strength of a covered adhesive layer, good anchoring and flexibility of the paper coating, something not previously achieved Maide can achieve. This method of making release paper by applying a coating on a paper surface that reduces the adhesion of sticky substances using an optionally dissolved in an inert solvent, if appropriate also in the form of such a solution in water emulsified, crosslinkable organopolysiloxane mixture, Adding known crosslinking agents immediately before applying the coating and subsequent heating of the paper coated therewith is characterized by that the organopolysiloxane mixture of (A) 50 to 80 parts by weight of an α, C) -Bis- (triorganosiloxy) -polydiorganosiloxane of the formula RaSi (CH3) 3-aO - [(- SiRb (CH3) 2-bO-) m (-Si (CH3) 2-O-) nm] -Si (CH3 ) 3-aRa wherein R is an alkenyl radical, n is chosen so high that the viscosity at 200 C is at least 106 cP, a = 0, 1, 2 or 3, b = 1 or 2 and m in the case a = 0 a value from 2 to b / 100, in all other cases a value from 0 to n / 100 (B) 20 to 50 parts by weight of α, # - dihydroxypolydimethylsiloxane of at least 1000 cP viscosity at 200 C and (C) 1 to 10, based on the sum of the weights of the polysiloxanes (A) and (B), α, # - bis (trimethylsiloxy) -polymethylhydrogensiloxane with a maximum viscosity of 1000 cP at 200 ° C exists 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), a crosslinking accelerator from the series of heavy metal carboxylates, dialkyltin carboxylates Amines and quaternary ammonium compounds are used and the crosslinking of the paper coating is carried out by briefly heating to 100 to 1200 C.

Preferably to be used as component (A) is one whose Alkenyl radicals R are vinyl or allyl radicals> whose viscosity is 107 to 108 cP 20 ° C and in which the number a = 1 or 2, the number b = 1 and the quotient m / n has one of the values from 0 to 15 # 10-4; as component (B) such an approximate one 107 cP viscosity at 200C; as component (C) one of 15 cP at 200C. The weight ratio (A) :( B) :( C) of these three mixture components is preferred to be selected in the range from 62: 35: 3 to 67: 30: 3.

As examples of component (D), those to be used according to the invention Crosslinking agent combinations are benzoyl peroxide, dichlorobenzoyl peroxide and tert-butyl peroxide and preferably called dicumyl peroxide. Examples of those to be used as component (E) Metal compounds are the lead, cobalt, zinc, manganese, zirconium, cerium and tin salts higher fatty acids, dioctyl tin maleate, dibutyl tin diacetate and preferably Dibutyltin dilaurate. The proportions are largely variable; they are preferably to be dimensioned in such a way that that the total mixture per 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 for easier handling, z, 9.

Xylene.

Likewise, although it is not essential to the process, it is essential to his convenient implementation advantageous, the mixture of polysiloxanes (A), (B) and (C) in an inert solvent such as toluene, xylene, mineral spirits, trichlorethylene or Perchlorethylene first to be dissolved in such an amount that you can use a stock solution 30 to 40 percent by weight polysiloxane content for storage. One moves then, as a rule, continue to dilute this stock solution for use and adding the crosslinking agent mixture. It then takes several hours at 200 C to until the solution ready for application to the paper noticeably thickens. This solution is used to coat the paper in a thin layer, for example by means of Roller or knife coater, and effected by heating the so coated Paper preferably to 1200 C the crosslinking, which takes place after just one minute is accomplished.

The speed and significant for the so-called migration resistance The completeness of the networking is to be regarded as surprising; she was after current level of experience at least in the reaction of the unsaturated Polysiloxane (A) not to be expected. Nor was it foreseeable that the invention performed paper coating to a considerable improvement in relation to the generally opposing properties of low peel force, d. H. low adhesion between release paper and adhesive, and extensive retention of adhesive strength, d. H. greatest possible adhesion between the adhesive and the one after it has been peeled off of the release paper brought into firm contact with the surface of another object, leads.

Each of the following does not restrict the claimed method Embodiments used as a coating base paper is glassine with a square meter weight of about 40 g.

The measured values referred to as "peel force" were determined as follows: A 24 mm wide cell glass tape with a sticky coating on one side, as commercially available under the trademark "Tesafilm 154n" pressed by hand onto the coated side of the release paper so that it is smooth and without the inclusion of air bubbles between the adhesive and the release paper. Then became the tape with the interposition of a spring balance perpendicular to the paper surface deducted at a speed of 10 cm per minute, -and the necessary Read the force on the spring scale To determine which of the adhesive tape the procedure was initially as described above; then that was glued on Tape between glass plates for 24 hours with a load of 10 g / cm2 against the release paper pressed, the temperature in a series of tests at 200C, was kept at 700 ° C in another. Then the tape was removed from the release paper peeled off, glued to and from a chrome-plated and polished metal plate with the interposition of a spring balance at an angle of 1350 again with withdrawn at a rate of 10 cm per minute. Meanwhile, on the scales read off the bond strength remaining on the tape. The associated original bond strength, measured to be 240 to 245 g in the following cases, was measured in the manner determines that an identical piece of tape must first be glued to a clean glass plate, removed again and then subjected to the test described on the metal plate became. The quotient of the adhesive force remaining after the release paper has acted and the original bond strength of the tape gives the amount of bond strength maintenance.

In the following, T1 means. weight parts; all viscosity values are measured at 200C.

Example 1 To prepare a stock solution, mix 122 T1. α, # - bis (vinyldimethylsiloxy) polydimethylsiloxane of 3 3 # 107 cP viscosity, 60 parts of α, # - dihydroxypolydimethylsiloxane of 8,106 cP viscosity, 6 T1. oC # -Bis- (trimethylsiloxy) -polymethylhydrogensiloxane from 15 cP viscosity and 312 T1. Xylene.

The viscosity of this stock solution is 5 # 104 cP, 10 T1. diluted of it one with 40 T1. Toluene and add 1 T1. a mixture of 20 parts of dicumyl peroxide, 33 T1. Dibutyltin dilaurate and 57 T1. Xylene. The solution thus obtained is carried along a glass squeegee in about 10 microns thick layer on the paper and heated this then for 1 minute at 1200C.

Peel force = 1 g; Retention of adhesive strength at 20 ° C. ### # = 71%; at 70 ° C. ### # = Example 2 The vinyl compound used in Example 1 is replaced by 122 parts of an α, # - bis (vinyldimethylsiloxy) vinylmethylpolysiloxane of the formula with m / n = 0.0015 and 4.107 cP viscosity and proceed as described there.

Stock solution viscosity = 57,000 cP; Peel force = 1 g; Retention of adhesive strength at 20 ° C. ### # = 74%; at 70 ° C ### # = 67%.

Example 3 The vinyl compound used in Example 1 is replaced by 122 Tl α, # - bis (methyldiallylsiloxy) -polydimethylsiloxane from 3.7-107 cP viscosity and proceed as described there.

Stock solution viscosity = 64,000 cP; Peel force = 1 g; Maintenance of adhesive strength at 20 ° C ### # = 86%; at 70 ° C ### # = 70%.

Example 4 Replace that in Example 3 for the preparation of the stock solution used 312 parts of xylene with 525 parts of trichlorethylene and the rest of the way as described there.

Stock solution viscosity = 1.5 # 105 cP; Peel force = 2 g; Maintenance of adhesive strength at 200C P 75%; at 700C 1 79%.

Example 5 The vinyl compound used in Example 1 is replaced by 122 parts of α, # -bis (methyldiallylsiloxy) allylmethylpolysiloxane of the formula with m / n = 0.0015 3.4 # 107 cP viscosity and proceed as described there.

Stock solution viscosity = 48,000 cP; Peel force = 1 g; Maintenance of adhesive strength at 200r ### # 4 84: at 700C t = 67%.

Comparative tests: The ones described below, with siloxane mixtures Coatings carried out according to the prior art show those described above Defects, namely a decrease in bond strength that increases with storage temperature the adhesive film or one that is more than a power of ten stronger, the tearing the film favors adhesion of the release paper to the covered film.

1) 67 Tl. Α, # - dihydroxypolydimethylsiloxane of 8 # 106 cP viscosity and 6 Tl. α, # - bis (trimethylsiloxy) -polymethylhydrogensiloxane of 15 cP viscosity were with 127 Tl.

Toluene mixed to a stock solution.

34 T1. of which 136 parts toluene and 1 part 1. Dibutyltin dilaurate mixed, and the solution thus obtained in the same way as described in Example 1, put on the paper and heated.

Peel force = 2 g; 161.5 g 97 g retention of adhesive strength at 20 ° C. = 67%; at 70 ° C = 40%.

240 g 240 g 2) An organopolysiloxane resin solution was used, the conventional method by hydrolysis of an organochlorosilane mixture of 195 T1. CH3SiC13, 11 T1. C6H5SiC13, 18 T1. (CH3) 2SiC12 and 3 T1. (CH3) 3SiCl in a mixture of 830 parts of water, 166 parts. Xylene and 166 T1. Butanol and following Evaporation to 51 weight percent organopolysiloxane content was produced. 393 Tl. Of this solution were 79 T1. of a mixed hydrolysis product from 10 T1. CH3SiC15 and 90 T1.

(CH3) 2SiCl2, 12 Tl. Α, # - dihydroxypolydimethylsiloxane of 1000 cP and 8 Tl. α, # - bis (trimethylsiloxy) -polymethylhydrogensiloxane in 108 T1. Isopropanol dissolved. This solution was with 600 T1. Toluene then were diluted 12 T1. Dibutyltin dilaurate mixed in. With the solution thus completed, the coating and heating carried out as described in Example 1.

Peel force = 94 g; Maintenance of adhesive strength at 20 ° C and at 70 ° C ### # = 64%.

Claims (5)

Claims 1. A method for producing release paper by Application of a coating that reduces the adhesion of sticky substances to a paper surface using an optionally dissolved in an inert solvent, if appropriate also in the form of such a solution in water emulsified, crosslinkable organopolysiloxane mixture, Adding known crosslinking agents immediately before applying the coating and subsequent heating of the paper coated therewith, d u r ch e k e It is noted that the organopolysiloxane mixture from (A) is 50 to 80 parts by weight of an α, # - bis (triorganosiloxy) polydiorganosiloxane of the formula RaSi (CH3) 3-aO - [(- SiRb (CH3) 2-bO-) m (-Si- (CH3) 2-O-) nm] - Si (CH3) 3-aRa, wherein R is an alkenyl radical, n is chosen so high that the viscosity at 200 C is at least 106 cP, a = 0, 1, 2 or 3, b = 1 or 2 and m in the case a = 0 a value from 2 to 100, in all other cases a value from 0 to n / 100 (B) 20 to 50 parts by weight of α, # - dihydroxypolydimethylsiloxane of at least 1000 cP viscosity at 200 C and (C) 1 to 10, based on the sum of the weights of the polysiloxanes (A) and (B), α, # - bis (trimethylsiloxy) -polymethylhydrogensiloxane with a viscosity of at most 1000 cP at 200 C, a mixture is used as the crosslinking agent from (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), a crosslinking accelerator from the series of heavy metal carboxylates, dialkyltin carboxylates, Amines and quaternary ammonium compounds are used and the crosslinking of the paper coating is carried out by briefly heating to 100 to 1200 C. 2. The method according to claim 1, wherein the alkenyl radicals R vinyl or Are allyl residues. 3. The method of claim 1, wherein the organic peroxide is dicumyl peroxide is. 4. The method according to claim 1, wherein the crosslinking accelerator (E) Is dibutyltin dilaurate. 5) Method according to claim 1, characterized in that the organopolysiloxane mixture from (A) 62 to 67 parts by weight of a bis (triorganosiloxy) polydiorganosiloxane the formula given there, in which R = vinyl or allyl, a = 1 or 2, b = 1, m = 0 to 0.0015 n and n is selected so high that the viscosity at 200 C 107 to 108 cP, (B) 35 to 30 parts by weight of α, # - dihydroxypolydimethylsiloxane of about 10 cP viscosity at 200 G and (C) about 3 parts by weight oc, C; 3 -Bis- (trimethylsiloxy) -polymethylhydrogensiloxane of approximately 15 cP viscosity bot 200 C consists, as crosslinking agents 1 (D) and (E) 5 to 6 parts by weight Dicumyl peroxide and 8 to 10 parts by weight of dibutyltin dilaurate are used and the crosslinking is carried out at about 1200.degree.