Plastics Process Analysis, Instrumentation, and Control

To adddress this problem, a manufacture method has been proposed in which a replica is formed based on the stamper mold original plate (61). The replica is used as a stamper mold in the UV optical nanoimprint step.

This method for manufacturing a polymer-made imprinted film with a fine structure having a minimum processing size of 1,000 nm or less includes (61):

1 A step of forming a coating film on the surface of a fine structure having a fine concavo-convex pattern of 1,000 nm or less and being composed of a polymer formed by polymerization,

2 A step of pressing the imprinted film with fine structure to a polymer precursor monomer or a composition of a polymer precursor monomer and polymerizing the polymer precursor monomer or the composition of a polymer precursor monomer, and

3 A step of releasing the imprinted film with fine structure from the polymer of the polymer precursor monomer or the composition of a polymer precursor monomer to transfer the fine concavo-convex pattern on the surface of the imprinted film with fine patterns to the polymer.

The above-described methods (59–61) for manufacturing a molded product with fine pattern are methods of performing a transfer-molding by pressing a heated polymer substrate or a molten polymer to a stamper mold having a fine structure. Such methods require the pressurization of a stamper mold having a nanoscale fine structure. A high degree of concern exists of breaking the stamper mold.

On the other hand, in electronic devices, optical devices, recording media, and biodevices, an attempt has been made to further improve their functionality by a molded product with a fine nanostructure, so there is a demand for a manufacturing method capable of manufacturing a molded product with fine nanostructure stably using various materials (58).

A method for manufacturing a molded product with a fine structure consists of the following steps (58):

1 In a temperature-controlled stamper mold having a fine structure containing a concavo-convex pattern having a width of 10 nm to 1 µm, forming a thermoplastic molten polymer layer to be in contact with the fine structure of the stamper mold which was kept at a predetermined temperature,

2 Holding the thermoplastic molten polymer layer for a predetermined time so as to transcribe the fine structure of the stamper mold to the thermoplastic molten polymer layer under gravity,

3 Cooling and solidifying the transcribed thermoplastic molten polymer layer, and

4 Subsequently releasing the solidified thermoplastic molten polymer layer from the stamper mold.

This method for manufacturing a molded product with a fine structure can economically manufacture a molded product with fine structure containing a concavo-convex pattern in high productivity without requiring pressurization (58). Moreover, it is possible to manufacture a molded product with fine structure which has a large area, which is rich in homogeneity, and which does not have internal strain, birefringence, and orientation. Furthermore, it is possible to manufacture such a molded product with a fine structure having a width of about 10 nm and a high aspect ratio. Since it is possible to perform the molding without any pressurization, damages such as abrasion and breakage of the fine structure of a stamper mold should be low, so that the life of the stamper mold can be lengthened.

The current issues of plastic waste pollution in the world have been handled in a monograph (62). This monograph covers most aspects of plastic, from its chemical makeup and manufacture to its various recycling possibilities and, in many cases, its final, unfortunate resting place in a landfill, soil, and the sea. Also, the economic, ecological, and technical aspects of plastic waste handling have been discussed in a monograph (63).

Waste plastics, that is, synthetic polymer-containing substances, are an environmental issue because of the problems associated with disposing of a large volume of non-biodegradable material.

It has been estimated that plastics account for about up to 15% by weight and 25% by volume of municipal solid waste produced in the United States (64). Increasing amounts of scrap and waste plastics have created an ever-expanding disposal problem for both industry and society in general. The increased popularity of bottled water has led to a huge increase in the amount of plastic bottles appearing in the municipal solid waste stream. The amount of plastic bottles sent to landfills has increased so much that several cities on the West Coast of the United States are considering bans on the sale of water in disposable plastic bottles.

Incineration, landfilling waste-to-energy and recycling are the main techniques used for the disposal of plastics (64). However, there are many problems associated with disposing of plastics.

One problem is that it takes a large amount of energy to incinerate plastic and the incineration process produces many products that are harmful to humans and the environment such as carbon monoxide, carbon dioxide, chlorine, and other hydrocarbons. These gases may also contribute to the global warming problem.

Another problem is that placing plastics in landfills takes a large amount of energy and landfill space. It takes many gallons of gasoline to bury a ton of plastic with machinery such as bulldozers in a landfill. Landfill space is increasingly becoming more scarce due to environmental problems associated with storing municipal wastes.

Another problem is that waste-to-energy conversion using plastics is not very efficient. Typically the energy used to convert fossil fuels to plastic is lost when plastics are burned for energy since waste-to-energy combustion is a relatively inefficient means of energy recovery (64).

Plastic debris in the marine environment is widely documented, but the quantity of plastic entering the ocean from waste generated on land is unknown. The mass of land-based plastic waste entering the ocean was estimated (65).

Waste estimates for 2010 for the top 20 countries ranked by the mass of mismanaged plastic are collected in Table 1.3.

Table 1.3 Plastic waste from various countries (65).

It was calculated that 275 Mt of plastic waste was generated in 192 coastal countries in 2010, with 4.8 to 12.7 million Mt entering the ocean. The population size and the quality of the waste management systems largely determine which countries contribute the greatest mass of uncaptured waste available to become plastic marine debris. Without waste management infrastructure improvements, the cumulative quantity of plastic waste available to enter the ocean from land is predicted to increase by an order of magnitude by 2025 (65).