Permeation-inhibiting release coating

Abstract

The invention relates to compositions containing at least one siloxane which comprises ethylenically unsaturated, radically polymerizing groups, and at least one hydrocarbon with ethylenically unsaturated, radically polymerizing groups, which have, when used as a separating coating, an improved barrier effect.

Claims

1. A permeation-inhibiting release coating obtained by curing a composition comprising components (I), (II) and optionally (III): (I) 20 to 90% by weight, based on a sum total of components (I), (II) and (III) of the composition, comprises silicon-free hydrocarbons which consist of carbon, hydrogen and oxygen and which have at least one ethylenically unsaturated free-radically polymerizable group and has no oxyethylene groups, wherein component (I) has a hydrocarbon to an extent of at least 80 and up to 100% by weight, based on a total mass of component (I), having two or more ethylenically unsaturated free-radically polymerizable groups and at least one aromatic group; (II) 10 to 90% by weight, based on a sum total of components (I), (II) and (III) of the composition, of one or more organomodified silicones having 50 to 500 silicon atoms, wherein 0.4 to 10% of silicon atoms optionally have ethylenically unsaturated free-radically polymerizable groups; and (III) 0 to 70% by weight, based on a sum total of components (I), (II) and (III) of the composition, of one or more organomodified silicones having 4 to 40 silicon atoms, wherein 15 to 100% of silicon atoms have ethylenically unsaturated free-radically polymerizable groups; and optionally an additive; wherein the permeation-inhibiting release coating has a permeation barrier against butyl acetate, and the permeation-inhibiting release coating has a delta-L* value of from 1 to 20.

2. The permeation-inhibiting release coating according claim 1, wherein the delta-L* value is from 1 to 18.

3. The permeation-inhibiting release coating according to claim 1, wherein the permeation-inhibiting release coating has a release force of at most 80 cN/2.5 cm, wherein a lower value of the release force is greater than 1 cN/2.5 cm, and wherein the release force is determined in accordance with FINAT Handbook 8th Edition, The Hague/NI, 2009 under the designation FTM 10.

4. The permeation-inhibiting release coating according to claim 1, wherein the ethylenically unsaturated free-radically polymerizable groups in components (I) and (III) and/or ethylenically unsaturated free-radically polymerizable groups, if present in component (II) are groups selected from an acrylic ester function, a methacrylic ester function or both.

5. The permeation-inhibiting release coating according to claim 1, wherein component (I) is present at 20 to 70% by weight, component (II) is present at 30 to 80% by weight, and component (III) is present at 0 to 40% by weight, all based on the sum total of components (I), (II) and (III) of the composition.

6. The permeation-inhibiting release coating according to claim 1, wherein the component (II) comprises a compound of formula (I):
M.sup.1.sub.aM.sup.2.sub.bD.sup.1.sub.cD.sup.2.sub.d  (I) wherein M.sup.1=[R.sup.1.sub.3SiO.sub.1/2], M.sup.2=[R.sup.1.sub.2R.sup.2SiO.sub.1/2], D.sup.2=[R.sup.1.sub.2SiO.sub.2/2], D.sup.2=[R.sup.1R.sup.2SiO.sub.2/2], a=0to 2, b=0to 2, and a+b=2, c=50 to 490, d=0 to 15, and a ratio of the sum (b+d) to the sum (c+d+2) is from 0.004 up to 0.1, the sum (c+d+2) is 50 to 500, R.sup.1 denotes identical or different aliphatic hydrocarbons having 1 to 10 carbon atoms or aromatic hydrocarbons having 6 to 12 carbon atoms, and R.sup.2 denotes identical or different hydrocarbons which have 1 to 5 identical or different ester functions, and the hydrocarbon is linear, cyclic, branched and/or aromatic.

7. The permeation-inhibiting release coating according to claim 1, wherein the component (III) comprises a compound of formula (II):
M.sup.1.sub.eM.sup.3.sub.fD.sup.1.sub.g D.sup.3.sub.h  (II) wherein M.sup.1=[R.sup.1.sub.3SiO.sub.1/2], M.sup.3=[R.sup.1.sub.2R.sup.3SiO.sub.1/2], D.sup.1=[R.sup.1.sub.2SiO.sub.2/2], D.sup.3=[R.sup.1R.sup.3SiO.sub.2/2], e=0 to 2 , f=0 to 2, and e+f=2, g=0 to 38, h=0 to 20 and a ratio of the sum (f+h) to the sum (g+h+2) is from 0.15 up to 1, the sum (g+h+2) is from 4 to 40, R.sup.1 denotes identical or different aliphatic hydrocarbons having 1 to 10 carbon atoms or aromatic hydrocarbons having 6 to 12 carbon atoms, and R.sup.3 denotes identical or different hydrocarbons which have 1 to 5 identical or different ester functions, and the hydrocarbon is linear, cyclic, branched and/or aromatic.

8. The permeation-inhibiting release coating according to claim 1, wherein component (III) comprises ester groups that are not free-radically polymerizable.

9. The permeation-inhibiting release coating according to claim 1, wherein ester groups that are not free-radically polymerizable are not present in component (II) and ester groups that are not free-radically polymerizable are present in component (III) in a numerical proportion of 5 to 15%, based on the number of all ester functions in component (III).

10. A method for preparing the permeation-inhibiting release coating according to claim 1, the method comprising: radiation-curing the permeation-inhibiting release coating.

11. A topcoat for thermal papers, comprising: a permeation-inhibiting release coating obtained by curing a composition comprising components (I), (II) and optionally (III): (I) 20 to 90% by weight, based on a sum total of components (I), (II) and (III) of the composition, comprises silicon-free hydrocarbons which consist of carbon, hydrogen and oxygen and which have at least one ethylenically unsaturated free-radically polymerizable group and have no oxyethylene groups, wherein component (I) has a hydrocarbon to an extent of at least 80 and up to 100% by weight, based on a total mass of component (I), having two or more ethylenically unsaturated free-radically polymerizable groups and at least one aromatic group; (II) 10 to 90% by weight, based on a sum total of components (I), (II) and (III) of the composition, of one or more organomodified silicones having 50 to 500 silicon atoms; and (III) 0 to 70% by weight, based on a sum total of components (I), (II) and (III) of the composition, of one or more organomodified silicones having 4 to 40 silicon atoms, wherein 15 to 100% of silicon atoms have ethylenically unsaturated free-radically polymerizable groups; and optionally an additive; wherein the permeation-inhibiting release coating has a permeation barrier against butyl acetate, and the permeation-inhibiting release coating has a delta-L* value of from 1 to 20.

12. The topcoat according to claim 11, wherein the thermal paper is self-adhesive and is designed as adhesive tape.

13. A radiation-curing coating composition for preparing a permeation-inhibiting release coating having a permeation barrier against butyl acetate, the permeation-inhibiting release coating comprising components (I), (II) and optionally (III): (I) 20 to 90% by weight, based on a sum total of components (I), (II) and (III) of the composition, comprises silicon-free hydrocarbons which consist of carbon, hydrogen and oxygen and which have at least one ethylenically unsaturated free-radically polymerizable group and have no oxyethylene groups, wherein component (I) has a hydrocarbon to an extent of at least 80 and up to 100% by weight, based on a total mass of component (I), having two or more ethylenically unsaturated free-radically polymerizable groups and at least one aromatic group; (II) 10 to 90% by weight, based on a sum total of components (I), (II) and (III) of the composition, of one or more organomodified silicones having 50 to 500 silicon atoms; and (III) 0 to 70% by weight, based on a sum total of components (I), (II) and (III) of the composition, of one or more organomodified silicones having 4 to 40 silicon atoms, wherein 15 to 100% of the silicon atoms have ethylenically unsaturated free-radically polymerizable groups; and an additive, wherein the permeation-inhibiting release coating has a delta-L* value of from 1 to 20.

14. The radiation-curing coating composition according to claim 13, wherein the additive is at least one selected from the group consisting of a photoinitiator, a photosensitizer, a filler, a pigment, a solvent, a phosphorus-containing compound which polymerizes under UV light, a stabilizer, an anti-misting additive and an amine synergist.

Description

EXAMPLES: COMPONENTS

(1) Component I:

(2) K-I-1: SR 489, tridecyl acrylate, Sartomer, France K-I-2: Ebecryl® 11, (a polyethylene glycol 600 diacrylate with Mw 700 g/mol), Allnex, Belgium K-I-3: PETIA, (a mixture of pentaerythritol tri- and tetraacrylate), Allnex, Belgium K-I-4: Ebecryl® 150, (a bisphenol A derivative diacrylate), Allnex, Belgium K-I-5: Ebecryl® OTA 480, (a propoxylated glyceryl triacrylate), Allnex, Belgium K-I-6: Ebecryl® 605 (a mixture of 80% bisphenol A diepoxyacrylate and 20% tripropylene glycol diacrylate), Allnex, Belgium K-I-7: Laromer® TMPTA, trimethylolpropane triacrylate, BASF, Germany

(3) Ebecryl® is a trademark of Cytec Surface Specialties S.A. Anderlecht, Belgium Laromer® is a trademark of BASF Ludwigshafen, Germany
Component II: E-II-1: An exclusively terminally modified silicone with N=50, where N is the number of silicon atoms in the molecule. Prepared by process described in U.S. Pat. No. 6,211,322 via a corresponding hydrogensiloxane by hydrosilylation with trimethylolpropane monoallyl ether and subsequent esterification with acrylic acid, to give 4 acrylate groups per molecule; correspondingly, 4% of the silicon atoms are acrylated. E-II-2: An exclusively terminally modified silicone with N=100. Prepared as E-II-1; correspondingly 2% of the silicon atoms are acrylated. E-II-3: An exclusively terminally modified silicone with N=200. Prepared as E-II-1; correspondingly 1% of the silicon atoms are acrylated. S-II-1: An exclusively laterally modified silicone with N=100. Prepared by process described in U.S. Pat. No. 4,978,726 via a hydrogensiloxane with 6 pendant SiH groups, by hydrosilylation with allyl glycidyl ether and subsequent ring opening with acrylic acid, to give 6 acrylate groups per molecule; correspondingly, 6% of the silicon atoms are acrylated. S-II-2: A terminally and laterally modified silicone with N=150. Prepared by process described in U.S. Pat. No. 6,211,322 via a hydrogensiloxane having 6 pendant and 2 terminal SiH groups, by hydrosilylation with 5-hexen-1-ol and subsequent esterification with acrylic acid, to give 8 acrylate groups per molecule; correspondingly, 5.3% of the silicon atoms are acrylated.
Component III: S-III-1: An exclusively laterally modified silicone with N=40. Prepared by process described in U.S. Pat. No. 4,978,726 via a hydrogensiloxane with 6 pendant SiH groups, by hydrosilylation with allyl glycidyl ether and subsequent ring opening with acrylic acid, to give 6 acrylate groups per molecule; correspondingly, 15% of the silicon atoms are acrylated. S-III-2: An exclusively laterally modified silicone with N=20. Prepared by process described in U.S. Pat. No. 4,978,726 via a hydrogensiloxane with 6 pendant SiH groups, by hydrosilylation with allyl glycidyl ether and subsequent ring opening with a mixture of 15% acetic acid and 85% acrylic acid, to give 5.1 acrylate groups per molecule; correspondingly, 25.5% of the silicon atoms are acrylated.

EXAMPLES: COMPOSITIONS

(4) TABLE-US-00001 TABLE 1 Exemplary compositions, content figures in % by weight based on the sum total of components listed Components I Component II Component III Content Content Content Example [wt %] [wt %] [wt %] A K-I-5 5 E-II-2 95 0 B K-I-5 10 E-II-2 90 0 C K-I-5 50 E-II-2 50 0 D K-I-5 90 E-II-2 10 0 E K-I-5 95 E-II-2 5 0 F K-I-5 50 E-II-1 50 0 G K-I-5 50 E-II-3 50 0 H K-I-5 50 S-II-1 50 0 I K-I-5 50 S-II-2 50 0 J K-I-5 20 E-II-2 60 S-III-1 20 K K-I-5 20 E-II-2 60 S-III-2 20 L K-I-5 20 E-II-2 20 S-III-2 60 M K-I-2 50 E-II-2 50 0 N K-I-3 50 E-II-2 50 0 O K-I-4 50 E-II-2 50 0 P K-I-6 50 E-II-2 50 0 Q K-I-7 50 E-II-2 50 0 R K-I-4 20 E-II-2 50 0 K-I-7 30 S K-I-4 20 E-II-2 50 0 K-I-5 30 T K-I-5 25 E-II-1 50 0 K-I-1 25 U 0 E-II-2 70 S-III-2 30 V 0 S-II-2 70 S-III-2 30 W 0 S-II-1 100 X 0 0 S-III-2 100

EXAMPLES: PERFORMANCE TESTING

(5) To produce radiation-curing coating compositions, 100 g of each of the compositions were combined with 2% of photoinitiator TEGO® A18 from Evonik Industries AG. The coating compositions were stirred manually with a spatula until there was no longer any visible in homogeneity.

(6) The coating composition was applied to Mitsubishi thermal paper type LL 8077, which has no protection layer on the thermal layer, of 50 cm width, that had previously been subjected to corona pretreatment with a generator output of 1 kW. The application was effected using a 5-roll coating unit from COATEMA® Coating Machinery GmbH, Dormagen, Germany with a weight per unit area of about 1.2 g/m.sup.2 and cured by the action of UV light from a medium-pressure mercury vapour lamp from IST® Metz GmbH, Nürtingen, Germany at 60 W/cm and at a lineal speed of 100 m/min under a nitrogen atmosphere with a residual oxygen content of less than 50 ppm.

(7) The coated samples were subjected to a testing of the quality of the release coating, barrier effect and release force.

(8) Quality of the release coating: The coating must cover the entire area and be sealed. This was determined by means of staining the coating with an ink composed of 0.1% methylene blue in water with a contact time of one minute. At the end of the contact time, the ink was drained off and removed completely with a tissue by dabbing. If the coating is provided with defects, the ink penetrates through these defects into the paper fibre and stains the white surface blue. The staining need only be a low marking in order to produce a coating suitable for the test. If the coating is not fully covered, the barrier effect cannot be sufficiently evaluated. The degree of blue staining is evaluated by a trained panel. The evaluation is categorized into grades from 1 to 3, where 3 is inadequate.

(9) Grade 1=very well sealed layer, no blue spots visible.

(10) Grade 2=still acceptable coating, few blue spots observable.

(11) Grade 3=inadequately sealed layer, many blue spots visible.

(12) The investigation of the barrier effect and release effect is carried out only using coatings of quality grade 1.

(13) Baffler effect: By applying 0.5 ml of butyl acetate to the cured release coating, the barrier effect is assessed. For this purpose, the solvent is applied to the surface at 25° C. and a relative air humidity of 40% for an exposure time of 20 seconds and is removed by soaking up with absorbent paper as far as possible without pressure and, after ventilation at room temperature in the hood, the effect on the heat-sensitive layer is assessed alter 30 minutes. If the coating does not have a good barrier effect, butyl acetate penetrates through the coating through into the paper fibre and activates the dye layer, whereby the white paper surface is stained grey to black. For a good barrier effect, the staining must only be a low marking. For the evaluation, an SP62 spectrophotometer from X-Rite, Michigan is used. With the spectrophotometer, L* values prior to treatment with butyl acetate (blank value) and alter treatment with butyl acetate are determined and the difference delta-L* values used for the evaluation. The release coatings according to the invention preferably have delta-L* values of 0 to 20 and are accordingly permeation-inhibiting in the context of the invention.

(14) Release force: The release effect with respect to adhesive materials, in industrial application usually adhesive tapes or labels, is expressed by the release force, with a low release force describing a good release effect. The release force is dependent on the quality of the release coating, on the adhesive and on the test conditions. For evaluation of release coatings, therefore, identical adhesives and test conditions ought to be present. To determine the release forces, the adhesive tape TESA®7475, trademark of tesa SE, Germany, Hamburg was used at a width of 2.5 cm. This test is carried out in accordance with FINAT Handbook, 8th Edition, The Hague/NL, 2009 under designation FTM 10, with the modification that the storage is carried out at 40° C. under pressure.

(15) The results of the barrier effect and the release forces are set out in Table 2. For all examples, release coatings with a quality grade 1 were used.

(16) TABLE-US-00002 TABLE 2 Results of the exemplary compositions, stated are the barrier effect (delta-L* values using SP62 spectrophotometer) and release forces (RF) using TESA ®7475 in cN/2.5 cm after storage at 40° C. for 24 hours. RF (TESA 7475) Barrier effect Example [cN/2.5 cm] (Delta-L*) Inventive A 6 32.9 no B 8 18.21 yes C 9 5.92 yes D 49 3.54 yes E 160 3.12 no F 15 4.71 yes G 6 8.95 yes H 12 8.74 yes I 8 7.13 yes J 9 16.41 yes K 8 14.3 yes L 55 13.13 yes M 10 25.31 no N 13 13.17 yes O 17 19.23 yes P 10 9.13 yes Q 13 9.86 yes R 14 11.15 yes S 12 7.31 yes T 13 35.4 no U 6 38.3 no V 5 39.8 no W 10 34.9 no X 255 23.53 no

(17) It is evident from Table 2 that compositions according to the invention have a good barrier effect against butyl acetate and at the same time a good release effect. Non-inventive compositions have a poor barrier effect with good release effect or even poor results for both properties.

(18) Whereas composition B, C and D have good barrier effect, composition A lacks this property. Although composition E has a good barrier effect, it does not have a good release effect however. Compositions A to E show that a higher proportion of component II has a positive effect on the release behaviour but a negative effect on the barrier effect.

(19) It is further evident that the inventive examples of component II in compositions F, G, H and I all show a good barrier effect with good release behaviour. Compositions J, K and L additionally comprise component III, whereby the barrier effect is not affected or only slightly negatively affected.

(20) It is further evident that the compositions M to Q and R, S, T, which comprise different components I, or mixtures thereof, enable different barrier effect.

(21) For instance, the composition M is without a good barrier effect since the organic acrylate component K-I-2 is highly incompatible with the silicone component II. This incompatibility is caused by the oxyethylene groups in component K-I-2. Mixture M is therefore a significantly biphasic system. Since such components I having oxyethylene groups only mix sparingly in the silicone component II, they enable only an inadequately stronger crosslinking, or none at all, of the weakly crosslinking silicone component II per se. Such mixtures are evidently lacking good barrier effect, such as in example M. These mixtures are therefore non-inventive.

(22) It is further evident that composition T, which comprises a high proportion of component I having only one ethylenically unsaturated free-radically polymerizable group, and is therefore non-inventive, cannot achieve a good barrier effect.

(23) Compositions U, V and W are examples of component II, compositions U and V also comprising component III which do not comprise component I. They all do not show a good barrier effect. This applies also to composition X, which is an example of component III and, besides the poor barrier effect, does not have good release behaviour.

(24) By using the compositions according to the invention, success is achieved in simultaneously obtaining a good barrier effect and a low release force.