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

Transcription

1 Release System Information Guide Syl-Off Solventless, Platinum-Catalyzed Vinyl Silicone Release Coatings from Dow Corning General Information Syl-Off brand solventless, platinum-catalyzed vinyl silicone release coatings are based on 100 percent solids reactive vinyl-functional siloxane polymers. When combined with their respective hydridefunctional crosslinkers and catalysts, these polymers form coatings that cure via an addition reaction in the presence of heat. Vinyl-functional silicone polymers contain these chemical groups: (Si-CH=CH 2 ). Hydride-functional crosslinkers contain these chemical groups: (Si-H). Different release coating combinations can be selected to meet different performance requirements such as curing temperature, release force, bath life, etc. Features Premium (easy) release Fast, low-temperature cure Relatively economical, compared to hexenyl polymer coatings A wide range of cure speeds, temperatures and release forces possible Choice of inhibitor systems to meet different processing and substrate requirements Cured coatings are durable, abrasion-resistant, nonblocking and nonmigratory continued inside Contents General Information...1 Product Range Details...4 Product Handling Information...6 Application Information...9 Formulation Suggestions...12

2 Inert against SBR adhesives; good for use with hot melts and most acrylics High release modifiers available 100 percent solids; solventless processing Food-contact-approved coating options available (specific coating recommendations and relevant regulations available on request) Physical Properties Syl-Off solventless, platinum-catalyzed vinyl silicone release coatings are based on 100 percent solids silicone fluids. They are designed to be applied to paper and film substrates using industrial coating equipment and then crosslinked (cured) to give a silicone elastomer. Appearance Viscosity Generally clear, colorless liquids From 150 to 1500 cst, depending on the formulation used Density Active Ingredients 100 percent Applications Release liners for pressure sensitive adhesive laminates and tapes Industrial release papers and films Casting papers Nonstick packaging, including packaging for rubber, asphalt and food In-line, double-sided and differential release applications Polymer Structure Both end-blocked and multifunctional polymers are available in a variety of molecular weights: x x x x x x x------x x x x x x x x x (End-blocked) (Multifunctional) In general, high-molecular-weight end-blocked polymers yield softer, more elastic coatings with easy release at low peel speeds and higher release at high peel speeds. Low-molecular-weight and multifunctional polymers, on the other hand, yield harder, less flexible coatings with less differentiation between high- and low-speed release force values. 2

3 For multifunctional polymers, the number of pendant reactive sites on the polymer chain can also affect bath life, cure, adhesive compatibility and release behavior (see Table 1). Table 1. End-blocked vs. multifunctional polymers. End-Blocked Longer bath life; slower cure; more complete cure Softer cured coating More suitable for use with solvent-based acrylic and hot melt adhesives Easy release at low peel speeds; higher (tighter) release at high speeds Multifunctional Shorter bath life; faster cure, less complete cure Harder cured coating More suitable for use with solvent-based rubber (SBR) and water-based acrylic adhesives Easy release at high peel speeds; higher (tighter) release at low speeds Systems Syl-Off solventless, platinum-catalyzed, vinyl silicone release coatings use a range of different catalyst inhibition systems to optimize bath life and cure performance for different operational temperature ranges. This range of inhibitor systems is split into two basic groups based on their performance. Table 2. system performance properties. Cure Low- (EtCH) Facilitates cure at web temperatures from 80 C (175 F) upward; good lowtemperature cure Bulk Bath Life Excellent Fair Thin-Film Bath Life Attention to coating head maintenance and cooling is required Standard- (Maleate) Facilitates cure at web temperatures from 120 C (250 F) upward; not suitable for low-temperature cure applications Good 3

4 Product Range Product Details Range Details Base Coatings: Most of the Syl-Off solventless, platinum-catalyzed vinyl silicone release coating products listed below 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 additional, locally available product options. Syl-Off Polymer Syl-Off Polymer Syl-Off Polymer Syl-Off 7395 Coating Syl-Off 7610 Coating Syl-Off 7817 Coating A 100 percent active solids silicone polymer containing a low-viscosity vinyl, end-blocked-only functional silicone polymer. Formulated without a catalyst. Provides fast cure and low release force at low peel speeds. A 100 percent active solids silicone polymer containing a low-viscosity vinyl, end-blocked and pendent-functional silicone polymer. Formulated without a catalyst. Provides fast cure, low release force at low peel speeds and a flat release profile. A 100 percent active solids silicone polymer containing a high-viscosity vinyl, end-blocked-only functional silicone polymer. Formulated without a catalyst. Provides fast cure and very low release force at low peel speeds. A 100 percent active solids silicone polymer containing a medium-viscosity vinyl, end-blocked-only functional silicone polymer. Formulated with platinum catalyst. Provides good bath life and low release force at low peel speeds. A 100 percent active solids silicone polymer containing a high-viscosity vinyl, end-blocked and pendent-functional silicone polymer. Formulated with platinum catalyst. Provides good bath life, low release force at low peel speeds and a flat release profile. A 100 percent active solids silicone polymer containing a high-viscosity vinyl, end-blocked-only functional silicone polymer. Formulated with platinum catalyst. Provides good bath life and very low release force at low peel speeds. Low- Low- Low- Standard- Standard- Standard- 4

5 Crosslinkers: Syl-Off 7048 Crosslinker Syl-Off 7678 Crosslinker Syl-Off Crosslinker Catalyst: Syl-Off 4000 Catalyst Release Modifiers: A 100 percent solids silicone crosslinker that is suitable for use with most Syl-Off solventless coatings. Recommended where optimum anchorage to substrate is required. A 100 percent solids silicone crosslinker. Suitable for use with most Syl-Off solventless coatings. Recommended where optimum cure performance and bath life are required. A 100 percent solids silicone crosslinker. Suitable for use with most Syl-Off solventless coatings. Recommended where a combination of good cure and anchorage is required. A reactive organo-platinum complex (5,200 ppm platinum) dispersed in polysiloxane. The standard catalyst included in Syl-Off solventless platinum-catalyzed release coatings. May be used to reduce cure temperature required when coating temperature-sensitive substrates. Can also be used to obtain more complete cure at a given temperature, or to optimize machine capacity by speeding cure, or to overcome substrate inhibition. Syl-Off Resin Syl-Off Resin Syl-Off 7612 Modifier Syl-Off 7780 Modifier High-Speed Process Aids: Syl-Off 7137 High Speed Crosslinker Syl-Off 7138 High Speed Crosslinker A 100 percent active solids release modifier resin compatible with vinyl-functional polymers. Formulated without a catalyst. Offers stable release and fast cure. Recommended for moderate release modification. A 100 percent active solids release modifier resin mixed with mono-olefin. Compatible with vinyl-functional polymers. Formulated without a catalyst. Very high efficiency modifier for use at lower temperatures. Recommended where extreme modification of release is required. A 100 percent active solids release modifier resin compatible with vinyl-functional polymers. Formulated with catalyst. Offers stable release and good bath life. Recommended for moderate release modification. A 100 percent active solids release modifier resin mixed with mono-olefin. Compatible with vinyl-functional polymers. Formulated with catalyst. High efficiency modifier with good bath-life performance. Recommended where high modification of release is required. A silicone fluid used as an additive to reduce misting during high-speed silicone roll coating. Designed to have no adverse effect on coating properties. Contains reactive SiH groups that crosslink into coating during cure. Suitable for use with coatings containing Syl-Off 7048 or Syl-Off Crosslinkers. A silicone fluid used as an additive to reduce misting during high-speed silicone roll coating. Designed to have no adverse effect on coating properties. Contains reactive SiH groups that crosslink into coating during cure. Suitable for use with coatings containing Syl-Off 7678 Crosslinker. Low- Low- Standard- Standard- 5

6 Product Handling Product Information Handling Information Substrates Syl-Off solventless, platinum-catalyzed vinyl silicone release coatings have been successfully applied to parchment; glassine; super-calendered, clay-coated and poly-coated krafts; plastic films and metal foil. Corona treatment may be needed to improve anchorage to polycoated krafts or films. The use of Syl-Off 7048 Crosslinker improves anchorage to clay-coated and poly-coated krafts as well as to plastic films. The suitability of a substrate for use with the chosen release coating should be evaluated before commercial application. Application Equipment Syl-Off solventless, platinum-catalyzed vinyl silicone release coatings are designed to be applied using precision coating equipment such as three-roll offset differential gravure and multi-roll smooth roll coaters. Solventless coatings may also be blended with aliphatic solvents to a desired solids concentration and then applied using conventional solvent coating equipment. Coat Weight Without experimentation it is difficult to establish precise recommendations for the correct amount of silicone coating to be deposited on the substrate. Deposition values are dependent on a combination of the viscosity of the coating formulation, the coating equipment used, equipment operation and substrate. A recommended starting point is 1 g per m² (0.62 lb per 3,000 sq ft ream); this can be adjusted to meet substrate and end-use application requirements. Coating trials should be conducted for each substrate and coating formulation used. Bath Life Coatings containing the low-temperature inhibitor have an average static bath life that exceeds 8 hours under normal ambient conditions. In practice, the actual useable bath life will be significantly shorter due to actual process temperatures and loss of inhibitor through atmospheric exposure. It is recommended that formulated coating baths be used within 4-6 hours. 6

7 Coatings containing the standard-temperature inhibitor also have an average static bath life that exceeds 8 hours under normal ambient conditions. In practice, the actual useable bath life will still be significantly shorter due to actual process temperatures and loss of inhibitor through atmospheric exposure, but superior to that of the low-temperature inhibitor systems. It is recommended that formulated coating baths containing the standard-temperature inhibitor be used within 4-6 hours. Bath life can vary significantly depending on the coating formulation and the test method used. Bath-life trials should be conducted for each formulation. Formulation Advice Crosslinker:Coating Ratio Good cure can be achieved with crosslinker:coating ratios (calculated and represented as moles SiH:moles Vi or SiH:Vi ratios ) ranging from 1.3:1 to 2.0:1. In some cases where anchorage or cure cannot be achieved within this range, it may be desirable to use higher SiH: Vi ratios, though this is also dependent on the type of vinyl polymer used. See the Formulation Suggestions section on page twelve. Catalyst Syl-Off solventless, platinum-catalyzed vinyl silicone release coatings require the presence of the platinum catalyst to promote the crosslinking or cure reaction. All of the Syl-Off coatings and modifiers containing the standardtemperature inhibitors are already pre-blended with platinum catalyst; but additional catalyst may be added to speed up the cure at lower temperatures or to counteract the inhibition effect from certain substrates. None of the Syl-Off polymers and resins containing the low-temperature inhibitor contain any of the platinum catalyst, so it is essential to include some Syl-Off 4000 Catalyst in the formulation to achieve cure. See the instructions in Bath Preparation on page eight for further information on catalyst addition or consult your Dow Corning Technical Service representative. 7

8 Release Modifiers Release modifiers (or resins ) may be added to increase the peel force required to separate the release liner from the adherent. The greater the amount of release modifier added, the greater the increase becomes. Actual results will vary depending on the exact formulation used and other factors such as adhesive and substrates. For more details, see the section on Release Performance on page ten. High-Speed Process Aids To reduce misting during high-speed silicone roll coating, it is recommended to mix some of the Syl-Off 7137 or 7138 High Speed Crosslinker into the base polymer prior to the addition of the primary crosslinker. Testing should be done to optimize the level of this process aid required, but it is recommended to stay within an addition range of 0.5 to 2.0 weight percent (based on the total bath). Syl-Off 7137 High Speed Crosslinker contains approximately 0.95 weight percent SiH and should be used in formulations where Syl-Off 7048 or Crosslinkers are used as the primary crosslinker. Syl-Off 7138 High Speed Crosslinker contains approximately 0.67 weight percent SiH and should be used in formulations where Syl-Off 7678 Crosslinker is used as the primary crosslinker. If the adhesive being used is sensitive to SiH functionality, it is advisable to adjust the crosslinker levels to compensate for the SiH levels present in the High Speed Crosslinker. Contact your Dow Corning Technical Service representative for additional formulation advice. Bath Preparation Equipment should be clean and dry. Stainless steel equipment is preferred for handling solventless silicone release coatings. The components should be mixed in the following order and then stirred for minutes (in total) to ensure homogeneity: 1. Blend coating and release modifier; mix thoroughly. 2. Add high-speed process aid (if needed) and crosslinker; mix thoroughly. 3. Add catalyst (if needed) while mixing; mix thoroughly. NOTE: The platinum catalyst is sensitive to contamination to a large range of compounds containing nitrogen, sulfur, tin, phosphorus, arsenic, antimony, selenium, tellurium and by some residual solvents and monomers. To prevent catalyst poisoning and inhibition of cure, good coater hygiene must be maintained. A more complete list of inhibiting agents is available from Dow Corning Corporation. 8

9 % Extractable Silicone Application Application Information Information Cure Performance Polymer structure, inhibitor system, time, temperature, type and age of substrate, catalyst level, coat weight, and degree of surface penetration can all affect the cure performance of Syl-Off solventless, platinum-catalyzed vinyl silicone release coatings. Due to the large number of variables involved, it is difficult to predict the temperature and machine speed settings required to achieve good cure of the silicone for any specific coater. As an indication, however, Figure 1 shows the impact of changes in web temperature and dwell time on the cure of a low-temperature inhibitor formulation as measured by silicone extractables. For the standard-temperature inhibitor system, the trends would be similar except that the web temperatures would need to be shifted up by 10 to 20 C (50 to 68 F) or so. Figure 1. Impact of temperature and dwell time on cure performance of low-temperature inhibitor system. Web ( C) Dwell Time, seconds Overcoming Cure Inhibition Some additives used in the manufacture of films and clay- and polycoated krafts as well as the pre-coat found on most glassines and super-calendered krafts can adversely affect cure by inhibiting or, in some cases, poisoning the performance of the platinum-based catalyst. 9

10 Furthermore, when using offset roller systems to apply platinumcatalyzed coatings, care should be taken with the choice of rubber used for the coated rubber rolls. Materials used to vulcanize the rubber may also inhibit the cure of the silicone coating by influencing the performance of the platinum catalyst. In some cases, where the effect on the platinum catalyst is only minor, this cure inhibition may be overcome through the use of higher levels of Syl-Off 4000 Catalyst. However, before attempting to remedy such problems by adding more catalyst, it is recommended that the process and raw materials be analyzed to determine the source of the inhibition and whether it can be overcome or minimized through other means. Addition of extra catalyst should only be used as a last resort. Release Performance Different coatings in the Syl-Off solventless, platinum-catalyzed vinyl silicone release coatings family can be selected for different applications depending on the release performance required. The key coating variable impacting release performance is the choice between multifunctional vinyl polymer and end-blocked-only vinyl polymer. Figure 2 shows the difference in release profile of a multifunctional vinyl vs. end-blocked-only polymer when evaluated against a standard waterbased acrylic PSA. The graph illustrates how an end-blocked-only polymer tends to give a rising release profile (release force increases with increasing delamination speeds), Figure 2. Comparison of release profile of a water-based acrylic PSA from an end-blocked vs. multifunctional silicone release polymer. Release Force (cn/25 mm) E nd -B lo c k e d P o lym e r M ultifunctio na l P o lym e r Delamination Speed (m/min) 10

11 whereas a multifunctional polymer tends to give a flat release profile (release force remains the same/increases only slightly with delamination speed). Effect of Release Modifiers The different release modifiers in the Syl-Off solventless, platinumcatalyzed vinyl silicone release coatings family fall into two basic types: standard release modifiers offering moderate release modification, optimum cure performance and ease of handling; and high-efficiency release modifiers offering extreme release modification. The choice of modifier type should depend on the level of release modification desired. Figure 3 shows the difference in performance for the two release modifier types when laminated against a hot melt PSA. Food Contact Information These products may comply with certain FDA, BfR, Kosher or other regulatory requirements for food contact applications. Contact your local Dow Corning representative for current compliance information. Limitations Figure 3. Comparison of the release performance of different types of release modifiers from a hot melt PSA (at a delamination speed of 0.3 m/min). These products are neither tested nor represented as suitable for medical or pharmaceutical uses. Health and Environmental Information Release Force (cn/25 mm) To support customers in their product safety needs, Dow Corning has an extensive Product Stewardship organization and a team of Product Safety and Regulatory Compliance specialists available in each geographical area. For further information, please consult your local Dow Corning representative Standard Modifier High-Efficiency Modifier Release Modifier Level (wt%) 11

12 Formulation Formulation Suggestions Suggestions Formulations Syl-Off solventless, platinum-catalyzed vinyl silicone release coating components can be combined and adjusted in several ways to meet various process and performance requirements. The formulations provided in the following tables are intended merely as reference points for further optimization and 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. The choice on whether to use the low-temperature inhibitor system or extended bath-life inhibitor system depends on a combination of process conditions and substrates. The extended bath-life inhibitor may be the preferred option under difficult process conditions; but if low curing temperatures are required, the low-temperature inhibitor is the only option. The two inhibitors should NOT be mixed. For specific formulation advice, contact your Dow Corning Technical Service representative. Table 3. Typical formulation information low-temperature inhibitor. Low- Formulations (A) Easy release, rising release profile (B) Easy release, gently rising release profile (C) Easy release, flat release profile D) Easy release, fast cure, flat release profile Syl-Off Coating 98.0 Syl-Off Coating Syl-Off Coating 98.0 Syl-Off Resin Syl-Off Resin Syl-Off Crosslinker Syl-Off 7048 Crosslinker 4.1 Syl-Off 4000 Catalyst Note: Numerical values refer to parts (by weight) per 100 parts of coating, release modifier or additive as supplied. 12

13 (E) Moderate release modification for typical label release (F) High release modification for two-side tape application

14 Table 4. Typical formulation information standard-temperature inhibitor. Standard- Formulations (A) Easy release, rising release profile (B) Easy release, flat release profile (C) Easy release, better anchorage and cure for claycoated substrates (D) Moderate release modification for typical label release Syl-Off 7395 Coating Syl-Off 7610 Coating 100 Syl-Off 7612 Modifier 20 Syl-Off 7780 Modifier Syl-Off 7048 Crosslinker Syl-Off Crosslinker Note: Numerical values refer to parts (by weight) per 100 parts of coating, release modifier or additive as supplied. In general, the ratio of SiH:SiVi recommended here is in the range of 1.5:1 for multifunctional polymers and 1.75:1 for end-blocked polymers. Increasing SiH level will improve cure performance, but may have a negative impact on the release performance (particularly for some crosslinkable acrylic PSAs). Conversely, decreasing the level of SiH will improve release stability to some extent, but may also have a negative effect on the cure performance. 14

15 (E) High release modification for two-side tape application

16 For Information and Assistance For product information, application troubleshooting, product samples and formulation advice, visit 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 Dow Corning s 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 the product will meet the Dow Corning 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 CONSEQUEN- TIAL 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 Dow Corning Corporation. All rights reserved. Printed in USA AGP7834 Form No