Duracure C3. A delayed action diamine curative

Transcription

1 199 Benson Road Middlebury, CT USA Effective: Duracure C3 A delayed action diamine curative DURACURE C3 is a delayed action diamine curative for use with Duracast urethane prepolymers. At room temperature, it is virtually non-reactive. However, when heated to C ( F), the compound unblocks and rapidly cures the prepolymer, forming a tough elastomer. When Duracure C3 is mixed with prepolymer at room or slightly elevated temperatures, pot lives are extremely long. Specific mixtures are relatively stable below 50 C for over a month. Duracure C3 also offers significant advantages in dynamic performance vs. conventional MBCA or diol cured systems. As a liquid with low viscosity, Duracure C3 is suitable for use with conventional processing techniques such as: open casting, transfer, compression or liquid injection molding and rotational casting as well as other techniques such as dipping that require one pot systems. In addition, it is uniquely suitable for specialty applications, which require large surface areas, intricate design, microwave curing or other situations which require essentially unlimited work life and stability. The information contained herein relates to a specific Chemtura product and its use, and is based on information available as of the date hereof. Additional information relating to the product can be obtained from the pertinent Material Safety Data Sheets. NOTHING IN THIS TECHNICAL DATA SHEET SHALL BE CONSTRUED TO CONSTITUE A REPRESENTATION OR WARRANTY, EXPRESS OR IMPLIED, REGARDING THE PRODUCTS CHARACTERTICS, USE, QUALITY, SAFETY, MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Nothing contained herein shall constitute permission or recommendation to practice any intellectual property without the permission of the owner. Chemtura and the Chemtura logo are trademarks of Chemtura Corporation or one of its subsidiaries. Copyright 2007 Chemtura Corporation. All rights reserved. Page 1

2 Product Description: (These data are typical values presented to describe Duracure C3; they are not intended to serve as specifications.) Chemical Composition... Approx. 47% dispersion of methylene dianiline/sodium chloride complex in dioctyl adipate (DOA) Amino Nitrogen (A.N.), %....Approximate value: 5.60* Equivalent Weight (E.W.)... Approximate value: 250* 25 C... White Liquid free from contamination Odor... Faint amine Decomposition Temperature When mixed with polymer, C, ( F) ( ) (Depends upon the formulation) Alone in air, C, ( F) (320) 30 C... Approximate value: 2500 (Brookfield Viscometer Model, RVT, spindle No. 5, max. speed 5 rpm) Moisture Content, % Settling Characteristics... Slow separation, re-disperses readily with agitation or rolling. Always mix thoroughly before using. Roll drum for at least 24 hours before use. Particle Size, um(microns)... 5 max. Total Ash, % Free MDA (typical) * E.W. is calculated by using the Amino Nitrogen (A.N.) number on the COA and the following formula: E.W.= (14.007/A.N)x100. Copyright 2007 Chemtura Corporation. All rights reserved Page 2

3 Toxicity and Handling Precautions The ACGIH has established a TLV for MDA (the active ingredient of Duracure C3 after thermal deblocking) of 0.1 ppm for an 8-hour TWA exposure. Since MDA is complexed with sodium chloride and dispersed in dioctyl adipate, dust exposure has been eliminated and, at recommended handling and processing temperatures, vapor exposure is minimized. Methylene dianiline (MDA), the active ingredient of Duracure C3 has been shown to produce cirrhosis of the liver and kidney damage in rats and dogs in experimental studies. It is known to have caused hepatitis in industrial workers in the early 1970 s. MDA is considered to be a potential human carcinogen and it has been added to the ACGIH Appendix A- 2.Duracure C3 can cause allergic skin reactions and eye irritation. The use of protective clothing and gloves is recommended. Storage Stability The storage stability of Duracure C3 appears to be unlimited at room temperature, and at least several months at 50 C (122 F). However it is recommended that Duracure C3 be stored at room temperature. Storage at room temperature for prolonged periods does not affect the performance of the product. Duracure C3 needs to be rolled after prolonged storage to provide adequate remixing to insure homogeneity prior to use. Storage or handling above 50 C (122 F) is not recommended since the complex may dissociate and reduce working life of the polymer/curative mix. Disposal Duracure C3 is not presently regulated under the Resource Conservation and Recovery Act (RCRA), as of the Federal Register of May 19, However, disposal should be made in an appropriate manner. Duracure C3 can be disposed of by allowing it to react with isocyanateterminated polymers containing excess isocyanate groups. It may be incinerated in a halogentype incinerator or buried in an approved landfill designed for chemical wastes. Disposal must be in accordance with local, state and federal regulations. SPECIAL NOTE - Except as otherwise provided by law outside the U.S.A., the following information should be noted: The information contained herein is correct to the best of our knowledge. Your attention is directed to the pertinent Material Safety Data Sheets for the products mentioned herein. All sales are subject to Chemtura s standard terms and conditions of sale, copies of which are available on request and are printed on the reverse of Chemtura invoices. Except as expressly provided in Chemtura s standard terms and conditions of sale, no warranty, express or implied, including warranties of merchantability or fitness for a particular purpose, is made with respect to the products described herein. Nothing contained herein shall constitute permission or recommendation to practice any invention covered by a patent without a license from the owner of the patent. Copyright 2007 Chemtura Corporation. All rights reserved Page 3

4 Compounding and Curing Characteristics Due to the blocked nature of the curative, mixtures of Duracure C3 and prepolymer must be heated to initiate the cure. The time necessary to cure a given part depends upon the time for the innermost section to reach the unblocking temperature of 115 to 160 C ( F). Once this takes place, the mixture cures rapidly due to the fast reaction between free MDA and the isocyanate groups. Films only a fraction of a millimeter (a few mils) thick, as used in adhesives, are cured in seconds, while 1.9 mm (75 mil) thick test slabs are cured in 2 to 10 minutes, depending on the temperature and polymer used. Table I COMPARISON OF DURACURE C3 VS. MBCA & 1,4-BD Duracure C3 MBCA 1,4-BD Prepolymer Duracast E900...AdipreneL100 Vibrathane B821 Equivalent Weight...250* Decomposition Temp., C Amino Nitrogen, % Mixing & Curing Polymer Mix Temp. o C ( F) 85 (185) (212) 82 (180) Curative Temp., o C ( F) R.T. 115 (240) R.T. Vulcanizate Properties Hardness Shore A % Modulus, psi % Modulus, psi Tensile, psi Break, % Tear, Split, pli Tear, Trouser, pli Bashore Rebound Compression Set, Method B 22 hrs.@158 F (70 C) 27%...27%..20% * The curatives are used at 95% of theory. Current EW is calculated by using the Amino Nitrogen (A.N.) number on the COA and the following formula: E.W.= (14.007/A.N)x100. Copyright 2007 Chemtura Corporation. All rights reserved Page 4

5 Post cure Post curing is highly recommended for applications requiring minimum compression set. Compression set improves significantly after the vulcanizate is postcured overnight (16 hours) at 100 C (212 F), particularly with lower curative levels (85 to 90%). Further reduction in compression set can be obtained by conditioning the vulcanizate at room temperature. Catalysis of Duracure C3 Polar compounds such as glycerol or urea have catalytic effects with Duracure C3. The addition of glycerol (at levels approximately 0.5% of resin) lowers the complex breakdown temperature leading to rapid cures as temperatures are increased above 70 C. The role of these catalysts is to reduce the unblocking temperature of the methylene-dianilinesodium chloride complex, not to increase the inherently rapid reaction between MDA and isocyanate groups. Processing Duracure C3 curing agent can be processed satisfactorily using batch mixing techniques or automatic mixing equipment for processing liquid urethane elastomers. Batch Mixing Adiprene and Vibrathane prepolymers should be warmed to C ( F), depending on the polymer, and then degassed. Duracure C3 can be kept at room temperature or warmed to 50 C (122 F). However it is recommended that Duracure C3 be kept at room temperature. Care must be taken not to overheat (above 50 C [122 F]) even a portion of the Duracure C3, because the complex may prematurely decompose. Oven heating with rolling is most satisfactory for warming Duracure C3, if required. The procedure sometimes used with MBCA, i.e., heating for a short time on a hot plate, must not be followed with Duracure C3 because local overheating causes local decomposition, resulting in shorter working life of the polymer/curing agent mix. Since Duracure C3 is a dispersion, it requires thorough agitation to achieve a satisfactory mix. Prior to use, the container of Caytur 31 should be rolled, at least 24 hours, until the container bottom shows no sediment after being inspected with a rod. Duracure C3 should be added to the warm polymer only with agitation, then thoroughly blended in with a spatula or motor driven agitator. Mixing should be done gently and carefully to avoid entrapping air. The mixed compound may then be poured into preheated molds and cured as usual. Soft and sticky areas on the surface of the vulcanizate indicate poor mixing, non-homogeneous Caytur or off-ratio condition. If required, the mixture of Duracure C3 and prepolymer can be conventionally degassed at C (140 F to 150 F) by conventional techniques. Copyright 2007 Chemtura Corporation. All rights reserved Page 5

6 Machine Mixing Suggested temperatures for machine mixing are: 70 to 95 C (158 to 203 F) for the polymer and 20 to 50 C (68 to 122 F) for Duracure C3. The polymer should be degassed. As noted earlier, the chemical stability of Duracure C3 decreases substantially above 60 C (140 F), so it should not be processed above that temperature. Microwave Curing The use of microwave energy to cure polyurethanes is quite rare. However, fabricators have been known to use microwave energy to preheat a batch of prepolymer before they add the curative. We believe that microwave curing is particularly suitable for curing of urethanes using curatives. The microwave energy can bring the curative-resin blends to temperatures high enough to deblock the complex quickly. With Duracure curatives and Duracast prepolymers, uniformly cured products can be fabricated using microwave energy. This type of curing could be easily adapted for quick, efficient and continuous curing of polyurethane sheeting, belting and coated products. Energy savings coupled with highly increased rates of productivity could translate into significant cost benefits for the processor. In summary, Duracure C3 is a curative for Duracast prepolymers which in comparison to conventional curatives provides; High performance parts Outstanding pot life (desirable for LIM, large rolls, large complex molds, rotational casting, etc.). Fast curability. Wide latitude in processing characteristics. Eminent suitability for microwave curing (ideal for belting, sheeting and fabric coating). Long term ambient stability when mixed with prepolymers. Copyright 2007 Chemtura Corporation. All rights reserved Page 6