Beverages including soft drinks and tea are sold in PET bottles. In Japan, more than seventy percent of empty PET bottles are collected for recycling. However, recycled plastics are characterized as having a lower performance than virgin materials and, in general, an uneven quality. Thus, most recycled plastics are used only for sheet and fiber products etc. which require low performance. Recycled plastics are not commonly used to manufacture bottles and other products that require high performance.
Plastics for exterior materials of MFPs require high performance in terms of strength and flame resistance (i.e. the exterior materials should be hard to crack and hard to burn).
Exterior parts are manufactured by an injection molding process in which plastics are heated, softened, and pressure-injected into the mold. Here, the plastics are required to be moderately soft and not too slimy when heated and to harden slowly and remain soft in the injection process so that they can fill every corner of the mold. PET (polyethylene terephthalate) is very difficult to mold because it is heat-sensitive (i.e. it readily melts or hardens against temperature changes).
To help build a sound material-recycling society, Konica Minolta set a goal to use recycled PET (derived from PET bottles whose collection rate is high) as the exterior material for its MFPs. In order to do so, it was necessary for this recycled PET to meet high performance levels.
Konica Minolta succeeded in improving the strength, flame resistance, and ease of molding of recycled PET by utilizing polymer alloy (polymer blending) technology for manufacturing composite materials with other types of plastics.
Konica Minolta found that the performance of recycled PET can be best improved with PC (polycarbonate). After reviewing the possibility of using PC, a final decision was made to use PC recycled from gallon bottles used for water servers. Konica Minolta succeeded in developing recycled PC/PET – a composite material derived from recycled PET and recycled PC. Recycled PC/PET is used for exterior parts of MFPs.
Polymer alloy technology is designed to elicit better performance by blending two or more plastic materials.
In creating a polymer alloy from recycled PET and recycled PC, it was critical to control the PET-PC interface conditions because they determine the impact strength to a large extent. If the PET-PC bonding interface in recycled PC/PET is weak, breakage occurs when force is applied, resulting in lower strength. For this reason, compatibilizer that is highly compatible with both PET and PC is added to strengthen the interface bonding.
Konica Minolta used its extensive expertise and knowledge regarding optimal temperature and other conditions for alloying, PET-PC blend ratio and additive addition, etc., to succeed in developing recycled PC/PET which has high flame resistance and is easy to mold.