Acrylic solid surface

Transcription

1 Application Guide Thermoset Chemicals Acrylic solid surface Process description Solid surface products are a type of cast polymer that utilizes high performance resins that do not require gel coating. Two types of resins are utilized for solid surface; unsaturated polyester (UPE) resin and acrylic resin. UPE based solid surface is addressed in another application guide. Acrylic solid surface products have superior stain resistance and UV stability to that of polyester. Products based on acrylic resins also can be thermoformed. A resin is mixed under vacuum with organic peroxides, pigments, and fillers to produce a flowable slurry which is poured into molds to form the desired product shape. Once the mold is filled, the resin mixture is consolidated by vibration. Processing can vary from simple batch mixing to sophisticated continuous meter/mixing. Cure can be conducted at either room or elevated temperature. General composition wt% Methyl Methacrylate (MMA) Syrup wt% Filler (ATH, color chips, etc.) Main applications Kitchen counter tops, sink basins, vanity tops, shower surrounds. Cure temperature Ambient cure : C ( F) Elevated cure : C ( F) Page 1 of 5

2 Cure temperature Ambient cure : C ( F) Elevated cure : C ( F) Cure system design For room temperature cure, there are two peroxides suitable, Benzoyl peroxide (BPO) and Perkadox PF-MT40Z. BPO is available in the form of a free flowing powder, Perkadox CH-50, and as a pourable dispersion, Perkadox 40E. Benzoyl peroxide (BPO) is used in conjunction with amine accelerators. Resins pre-promoted with amines are now commercially available. BPO can provide a long gel time making it well suited for batch casting operations. Typical initiators for room temperature cure of acrylic solid surface Product name Description Peroxide content Perkadox CH-50 Free flowing, readily soluble in MMA, BPO powder in DCHP Active oxygen (%) T s max. aaaa F ( C) SADT NFPA Class Standard packages F ( C) 50% 3.3% 77 (25) 131 ( 55) III** 50# Carton Perkadox 40E Pourable dispersion of BPO 40% 2.6% 77 (25) 122 ( 50) IV 45# Pail, 440# Drum Perkadox PF-MT40Z tert-butyl monoperoxymaleate 40% 8.9% 86 (30) 140 ( 60) III** 18 kg Plastic Pail Accelerator CTA Proprietary accelerator for N/A N/A 86 (30) N/A not 18 kg Plastic Pail Perkadox PF-MT-40 & 40Z rated Accelerator ZTA Proprietary accelerator for Perkadox PF-MT-40 & 40Z N/A N/A 86 (30) N/A not rated 18 kg Plastic Pail ** Estimated from NFPA 432 based on similar formulations. BPO/amine systems can cause some discoloration that can be noticeable in white or light colored parts. Perkadox PF-MT40Z with Accelerator CTA or ZTA is a new non-yellowing cure system, which eliminates yellowing and provides a higher degree of cure. This flexible cure system can be adapted to work in both batch casting and continuous operations. Additional levels for Perkadox PF-MT40Z range from 1.0 to 3.0%. Addition levels for CTA and ZTA range from 0.5 to 1.5%. Either Accelerator can be used to adjust the gel time, but also have an effect on the rate of cure and final conversion. The following data displays the effect of Accelerator CTA & ZTA concentration on gel time and cure in a ½ panel with 60% ATH. Accelerator CTA is especially suited for slow gel time batch processes while Accelerator ZTA is designed for faster gel time or the increased degree of cure requirements of a high speed continuous process. Page 2 of 5

3 Figure 1. Effect of Accelerator CTA/ZTA percentage 1/2" Panel, 60% ATH, 2.0 phr Perkadox PF-MT40Z Accelerator CTA (%) Accelererator ZTA (%) 0.4 The initiator and accelerator levels required are dependent upon the resin reactivity, filler loading, part thickness and temperature. Lower resin reactivity, higher filler loadings, and thinner parts can cause lower exotherms & slower cure and can demand higher levels of peroxide & catalyst to achieve the same degree of cure. Accelerator CTA levels exceeding 1.0% can cause a rapid decrease in cure efficiency while Accelerator ZTA levels can be raised up to 2.0% to achieve higher speeds and better cure. Levels of either below 0.5% can increase residual MMA dramatically. The reactivity differences between a ¾ panel with 50% ATH loading and a ½ panel with 60% ATH are shown in Figures 2 and 3. Figures 2, 3: Effect of part thickness and filler loading on gel time (2) and residual MMA (3) (2.0 phr Perkadox PF-MT40Z) Accelerator CTA (%) 2

4 In the ¾ panels, the reactivity is dramatically increased due to the mass effects. The gel time in the ¾ panels is more than twice as fast as in the ½ for the same level of CTA. At low levels of CTA, similar amounts of residual MMA are found in both ½ and ¾ panels, while at higher levels of CTA, a much higher degree of cure is found in the ¾ panels. Because of this mass effect, producing acrylic parts by batch processing can be challenging. The data previously reported is for a resin temperature of 25 C. If the resin is heated during mixing or the temperature of the processing facility, pot life can significantly decrease. Pot life can be extended with small amounts of inhibitor such as BHT. Below is an example of pot life as a function of temperature for an inhibited system. Figure 4. Estimated pot life as a function of temperature 0.50 phr CTA, 1.5 phr Perkadox PF-NT40Z, 0.4 phr BHT (10%) Temperature ( C) Molders utilizing continuous processing can attain faster gel times by using higher levels of Perkadox PF- MT40Z and Accelerator ZTA. Prototype formulations for batch and continuous manufacturing methods are presented in the table below for comparison. Page 4 of 5

5 Typical ambient cure reactivity data of acrylic solid surface (25 C) Cure system 0.5 phr Perkadox CH-50, prepromoted with amine 1.25 phr Perkadox PF-MT40Z, 1.0 phr CTA 2.0 phr Perkadox PF-MT40Z, 0.75 phr CTA 2.0 phr Perkadox PF-MT40Z, 1.5 phr ZTA Description Thickness (inches) ATH loading (%) Gel time Peak exotherm ( C) Time to peak Gel to peak Residual MMA (wt%) Batch ½ Long gel time ½ Short gel time ½ Accelerated cure for continuous ½ Additional end-use information is available in various application sheets or directly from your Akzo Nobel representative. Perkadox is a registered trademark of Akzo Nobel Polymer Chemicals BV or affiliates. All information concerning this product and/or suggestions for handling and use contained herein are offered in good faith and are believed to be reliable. Akzo Nobel Polymer Chemicals, however, makes no warranty as to accuracy and/or sufficiency of such information and/or suggestions, as to the product's merchantability or fitness for any particular purpose, or that any suggested use will not infringe any patent. Nothing contained herein shall be construed as granting or extending any license under any patent. Buyer must determine for himself, by preliminary tests or otherwise, the suitability of this product for his purposes. The information contained herein supersedes all previously issued bulletins on the subject matter covered. The user may forward, distribute, and/or photocopy this document only if unaltered and complete, including all of its headers and footers, and should refrain from any unauthorized use. You may not copy this document to a website. Akzo Nobel Polymer Chemicals BV Akzo Nobel Polymer Chemicals LLC Akzo Nobel Polymer Chemicals Ltd. Amersfoort, The Netherlands Chicago, U.S.A. Shanghai, PR China Tel Tel Tel Fax (Toll free US only) Fax Fax polymerchemicals.nl@akzonobel-pc.com polymerchemicals.na@akzonobel-pc.com polymerchemicals.ap@akzonobel.com Akzo Nobel Polymer Chemicals Page 5 of 5