Syl-Off Emulsion, Platinum-Catalyzed Silicone Release Coatings from Dow Corning

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1 Syl-Off Emulsion, Platinum-Catalyzed Silicone Release Coatings from Dow Corning Release System Information Guide Features Low silicone coat weights possible A wide range of substrates possible Cured coatings are nonblocking, non-migratory Coatings perform well with many adhesives, and a wide range of release forces is possible Food-contact options available Long bath life Good shear stability Low foaming potential Contents General Information... 1 Product Range Details... 2 Product Handling Information... 3 Application Information... 6 Formulation Suggestions General Information Syl-Off brand emulsion, platinum-catalyzed silicone release coatings consist of vinyl-functional base polymers formulated with a crosslinker, a bath-life extender and a biocide. When combined with their respective catalysts, these coatings cure via a thermally initiated addition reaction. Web temperatures above 100 C (212 F) are typically required. With silicone emulsion (water-based) coatings, uniform, low coat weights can be obtained on simple solvent coating equipment. Unlike solvent-based coatings, however, emulsions can also be used in sizepress operations and with an air knife. Thickeners can be added that allow emulsion coatings to be used on more-porous papers that would be considered unsuitable for solvent-based or solventless silicone systems. Thickeners increase coating viscosity, which reduces penetration and prevents rupturing of the emulsion film during drying. Syl-Off emulsion, platinum-catalyzed silicone release coatings offer premium release and a fast, low-temperature cure; are nonmigrating; and are nonblocking suitable for two-sided differential applications.

2 Physical Properties Syl-Off emulsion, platinum-catalyzed silicone release coatings are oil-in-water emulsions. They are typically supplied as 40 percent solids emulsions with a ph between 4 and 6, and have an average particle size of 0.5 micron. Applications Release liners for pressure sensitive adhesive laminates and tapes (both one- and two-side coated) Paper machine applications Casting papers General industrial release papers Food-grade release and packaging papers General-purpose packaging Product Range Details The Syl-Off emulsion, platinum-catalyzed silicone release coating products listed on pages 2 and 3 are available worldwide and meet the majority of global industry requirements. However, they represent only a portion of Dow Corning s silicone release technology. Contact your Dow Corning representative for information about other, locally available product options. Pressure Sensitive Release Applications Base Coatings: Syl-Off 7950 Syl-Off 7990 Syl-Off 7974 Syl-Off 7934 Syl-Off 7935 A 40 percent solids emulsion of a vinyl-functional silicone polymer in water. The coating is pre-formulated with crosslinker. Suitable for use in PSA release applications. Cured coating offers easy release at low peel speed. A 40 percent solids emulsion of a vinyl-functional silicone polymer in water. The coating is pre-formulated with crosslinker. Provides premium release performance and a fast cure speed. Suitable for use in both PSA release and bakery release applications. Suitable for in-line lamination. Should only be used with Syl-Off 7975 Catalyst Emulsion. A 40 percent solids emulsion based on a vinyl-functional silicone polymer. Designed specifically for premium bakery release applications. Should only be used with Syl-Off 7975 Catalyst Emulsion. Suitable for use on papermaking machines. A 40 percent solids emulsion based on a vinyl-functional silicone polymer. Designed specifically for filmic release applications. Should only be used with Syl-Off 7975 Catalyst Emulsion. Suitable for use during polyester film extrusion process or traditional coating operations. A 40 percent solids emulsion based on a vinyl-functional silicone polymer. Designed specifically for filmic release applications. Should only be used with Syl-Off 7975 Catalyst Emulsion. Suitable for use during film extrusion process. 2

3 Catalysts: Syl-Off 7923 Catalyst Emulsion Syl-Off 7924 Catalyst Emulsion Syl-Off 7975 Catalyst Emulsion A 40 percent solids emulsion of vinyl-functional polymer and platinum catalyst in water. Suitable for use with Syl-Off 7950 and Syl-Off 7931 Release Modifier Emulsion. A 40 percent solids emulsion of vinyl-functional polymer and platinum catalyst in water. An extended bath-life catalyst recommended where long bath-life is required. Suitable for use with Syl-Off 7950 and Syl-Off 7931 Release Modifier Emulsion. A 40 percent solids emulsion of vinyl-functional polymer and platinum catalyst in water. A high-performance catalyst, compatible with the full range of base coating and release modifier emulsions. Release Modifier: Syl-Off 7931 Release Modifier Emulsion A 40 percent solids emulsion of a complex reactive organofunctional siloxane. May be used with any of the base polymers, or independently (along with catalyst), to raise the release force. Product Handling Information Substrates Syl-Off emulsion, platinum-catalyzed silicone release coatings have been successfully applied to a range of different papers, including: Uncoated papers such as uncoated krafts, boards, greaseproof and vegetable parchment. Thickeners may be required on some porous, uncoated papers to reduce penetration of the release coating. Coated papers such as super-calendered krafts, glassines and clay-coated krafts. The suitability of a substrate for use with the chosen release coating should be evaluated before commercial application. Application Equipment Syl-Off emulsion, platinum-catalyzed silicone release coatings can be applied using a wide range of coating techniques. When coating off paper machine, techniques such as rod, direct gravure, air knife, squeeze roll, reverse roll or trailing blade coating heads can be used. When coating on paper machine, techniques such as blade, size-press and metered size-press can be used. 3

4 Coat Weight In practice, coating baths typically range from 6 percent up to approximately 30 percent silicone solids by weight. At these levels, dry coat weights can typically be achieved between 0.3 and 1.3 g/m² ( lb per 3,000 sq ft ream). The coat weight can be varied by changing the coating parameters, the coating technique and/or the concentration of silicone in the coating bath. Coating trials should be run for each substrate used in order to optimize the formulation and process conditions and to ensure the suitability of the substrate for the application being considered. Shear Stability Although these coatings have been formulated for optimum shear stability, being emulsions, they are nevertheless sensitive to shear. It is recommended that agitation during mixing and circulation be kept to a minimum. To facilitate this, it is recommended that low-shear pumps be used to transport materials (e.g., gear, vane or diaphragm pumps). It is strongly recommended that centrifugal pumps not be used since they generate excessive shear and air entrapment. Bath Life At the recommended coating/release modifier to catalyst ratio, the static bath life of of Syl-Off emulsion, platinum-catalyzed silicone release coatings is between 12 and 24 hours at 25 C (77 F), depending on the choice of base polymer and catalyst. The effective life of the formulated bath/stock solutions, however, varies considerably with bath solids, catalyst level, temperature, and the use of thickeners and other additives. In high-temperature surroundings (the size press on a paper machine for example), the use of some form of heat exchanger is recommended to keep bath temperatures below 30 C (86 F). The ionic content and ph of the dilution water can also affect bath life. The ph range should be between 6 and 7. There is no change in bath appearance as the bath nears the end of its usable life; however, the cured coating may appear dull on the paper, and there will be a change in release performance, as well as the degree of cure of the coating. 4

5 Formulation Advice Base/Catalyst Ratio Syl-Off emulsion, platinum-catalyzed silicone release coatings for pressure sensitive release are 40 percent active silicone solids as supplied. Good cure performance can be achieved with coating:catalyst ratios ranging from 80:20 to 95:5. Note that while raising the ratio of catalyst will improve the cure performance, it will simultaneously reduce bath life. Release Modifier To achieve a release coating with tighter (higher) release, release modifiers may be used to replace some or all of the base coating (as long as the same level of catalyst is maintained so the ratio of base + release modifier:catalyst is constant). Thickeners Thickeners may be added to the bath to aid in the coating process, film forming and/or degree of penetration of the coating. Suitable thickeners include hydroxy ethyl cellulose (HEC). Any thickener, however, should be thoroughly evaluated prior to commercial use. Typically, thickeners are used in a range from 2 to 10 percent by weight, based on silicone solids. The optimum level should be determined by thorough evaluations to determine the impact of the thickener on all aspects of release coating performance, including cure, bath life and release. Antifoams These Syl-Off emulsion release coatings have been formulated to give a minimum of foam during mixing and processing. The use of certain process equipment, however, such as some gravure rolls, Meyer bars and certain paper machines, may lead to the creation of foam, which can impair bath life and/or coverage in some cases. In these situations, the use of very low levels of Syl-Off EM 7989 Antifoam is recommended. A level of between 0.1 and 0.5 weight percent (based on the overall bath) is recommended. Bath Preparation To prepare a Syl-Off emulsion, platinum-catalyzed silicone release coating bath, follow these steps: 1. Combine the required amount of water with thickener and/or antifoam (if required). 2. Blend the selected base emulsion with the release modifier emulsion (if required). 3. Add this blend to the water mixture and mix thoroughly (using a minimum amount of shear). 5

6 4. Add the required amount of catalyst emulsion to the bath and mix thoroughly again (all the time using a minimum amount of shear). Alternatively: 1. Combine the required amount of water with thickener and/or antifoam (if required). 2. Add the selected base emulsion to the water mixture. Add the release modifier emulsion (if required) to the water mixture and mix thoroughly (using a minimum amount of shear). 3. Add the required amount of catalyst emulsion to the bath and mix thoroughly again (all the time using a minimum amount of shear). Note: The platinum catalyst is sensitive to contamination from a range of different materials and, in particular, to compounds containing nitrogen, sulfur, tin or phosphorus. To prevent the catalyst from being poisoned and inhibiting cure, all handling equipment, transfer pumps and piping must be cleaned of contaminants prior to coming in contact with the coating formulation. Always thoroughly rinse all surfaces with water after cleaning. Application Information Pressure Sensitive Release Applications Cure Performance Many different factors can influence the cure performance of Syl-Off emulsion, platinum-catalyzed silicone release coatings, including: Temperature and type of oven Dwell time in the oven Type and age of substrate Coat weight Degree of surface penetration of coating There are also other factors relating to the bath formulation that can affect cure performance. First and foremost is altering the ratio of catalyst to base emulsion (increasing the catalyst improves cure speed but will negatively influence bath life). Some additives included in the silicone coating formulation (such as thickeners and film-forming additives) may also adversely affect cure performance. 6

7 Figure 1 illustrates the cure performance of a typical emulsion coating in terms of percent silicone extractables vs. machine speed, dwell time and exit web temperature (extractables being the amount of uncured silicone that can be extracted from a cured sample). Figure 1. Cure performance of emulsion systems in terms of extractables (180 C air temperature) Extractables, % Line speed, m/min 200 Dwell time, sec Traditional Syl-Off 7990 and Syl-Off 7975 Catalyst Emulsion Figure 2 illustrates the impact of changing the ratio of base/catalyst emulsion on the cure performance. Figure 2. Impact of catalyst ratio on cure performance of emulsion coatings / /10 85/15 Silicone Extractables, % Line speed, m/min 300 Dwell time, sec 2.4 Exit web temp, C Note: Exact extractables values will differ depending on the coating:catalyst combination used. 7

8 Release Performance Different base coatings can be selected for different applications depending on the release performance required. Figure 3 illustrates the impact of Syl-Off 7931 Release Modifier Emulsion on the release performance (at 10 m/min peel speed) of an acrylic PSA tape at different levels of release modifier addition. Figure 3. Release performance of Syl-Off 7931 Release Modifier Emulsion from acrylic PSAs Syl-Off 7931 Release Modifier Emulsion, % Test conditions: Release of tesa 7475 adhesive tape from glassine liner hand-coated with a Syl-Off 7950 /Syl-Off 7931 Release Modifier Emulsion/Syl-Off 7923 Catalyst Emulsion system; coating:catalyst ratio 85:15; coating cured for 30 seconds at 150 C (302 F); 1-day liner aging at room temperature; liner pulled from laminate at 180 and 10 m/min delamination speed. 8

9 Bakery Release Applications Syl-Off 7974 is suitable for bakery release applications when used with Syl-Off 7975 Catalyst Emulsion. This release coating is suitable for a wide range of different food release applications, as well. The coating can be applied using off-machine coaters that employ a variety of coating techniques (direct and offset gravure, Meyer rod, air knife and squeeze-roll coaters). It can also be applied on the paper machine using size-press or metered size-press coating heads. The formulation of this system has been optimized in terms of water repellency and release performance to meet the needs of a range of different bakery products following different test protocols. Food-Contact Information These products may comply with certain FDA, BFr, Kosher or other regulatory agency requirements for food-contact applications. Contact your local Dow Corning representative for current compliance information. Limitations These products are neither tested nor represented as suitable for medical or pharmaceutical uses. Health and Environmental Information To support customers in their product safety needs, Dow Corning has an extensive Product Stewardship organization and a team of Health, Environment and Regulatory Affairs specialists available in each area. For further information, please consult your local Dow Corning representative. 9

10 Formulation Suggestions Formulations Syl-Off emulsion, platinum-catalyzed silicone release coating components can be combined and adjusted in several ways to meet various processing and performance challenges. The typical formulations that follow are intended merely to serve as reference points for further discussion. Dow Corning does not warrant their merchantability, fitness for use, performance, efficacy, safety or freedom from patent infringement. It is your responsibility to thoroughly test any formulation before use. For specific formulation advice, contact your Dow Corning Technical Service representative. Formulation Syl-Off 7950 (A) Off-machine coating. Standard performance 12% solids (by weight) 27.0 Syl-Off 7990 Syl-Off 7974 Syl-Off 7935 Syl-Off 7931 Release Modifier Emulsion Syl-Off 7923 Catalyst Emulsion 3.0 Syl-Off 7975 Catalyst Emulsion Syl-Off 7989 Antifoam Water

11 (B) Off-machine coating. Fast curing performance 12% solids (by weight) (C) Off-machine coating. Modified release 12% solids (by weight) (D) On-machine coating. Bakery release 12% solids (by weight) (E) In-line film extrusion coating. Filmic release 10% solids (by weight) (F) Off-machine fast curing. Bakery release 8% solids (by weight)

12 For Information and Assistance For product information, application troubleshooting, product samples and formulation advice, visit dowcorning.com/psi or call one of our global Technical Information Centers: The Americas Asia Europe English +49 (0) German +49 (0) French +49 (0) LIMITED WARRANTY INFORMATION PLEASE READ CAREFULLY The information contained herein is offered in good faith and is believed to be accurate. However, because conditions and methods of use of our products are beyond our control, this information should not be used in substitution for customer s tests to ensure that our products are safe, effective and fully satisfactory for the intended end use. Suggestions of use shall not be taken as inducements to infringe any patent. Dow Corning s sole warranty is that our products will meet the sales specifications in effect at the time of shipment. Your exclusive remedy for breach of such warranty is limited to refund of purchase price or replacement of any product shown to be other than as warranted. DOW CORNING SPECIFICALLY DISCLAIMS ANY OTHER EXPRESS OR IMPLIED WARRANTY OF FITNESS FOR A PARTICULAR PURPOSE OR MERCHANTABILITY. DOW CORNING DISCLAIMS LIABILITY FOR ANY INCIDENTAL OR CONSEQUENTIAL DAMAGES. Dow Corning and Syl-Off are registered trademarks of Dow Corning Corporation. We help you invent the future is a trademark of Dow Corning Corporation. All other trademarks are the property of their respective owners. 2006, 2011 Dow Corning Corporation. All rights reserved. Printed in USA AGP11639 Form No B-01