Process for producing alkenyl aromatic foams using a combination of atmospheric and organic gases and foams produced thereby

Abstract

There is disclosed a process for producing alkenyl aromatic foams utilizing a combination of atmospheric and organic gases as blowing agent, preferably using greater than 30% by weight of atmospheric gas, and preferably also using a predetermined about of a masterbatch mix comprising a styrenic polymer, a rubbery block copolymer, and a solid blowing agent. Also disclosed are alkenyl aromatic foams produced by the process which exhibit increased densities, increased thermoforming capabilities, increased post-expansion properties, and increased retainment of the atmospheric and organic gases.

Description

[0001]This is a continuation application of application Ser. No. 08 / 163,010, filed Dec. 7, 1993, now U.S. Pat. No. 5,595,694 which, in turn, is a continuation application of application Ser. No. 07 / 995,289, filed Dec. 22, 1992, now U.S. Pat. No. 5,269,987.FIELD OF THE INVENTION[0002]This invention relates to a process for producing alkenyl aromatic foams utilizing a combination of atmospheric and organic gases as blowing agents, preferably also using a predetermined amount of masterbatch mix. The invention also relates to alkenyl aromatic foams resulting from the process, and articles made therefrom. Preferably, the alkenyl aromatic is polystyrene. The process and resulting foams of the present invention are conferred with several benefits among which are an increase in the production rate of the process, a reduction in the amount of organic gas which must be used in the process in order to obtain a foamed product having a given density, an increase in the thermoforming output of th...

AI Technical Summary

Problems solved by technology

Alkenyl aromatic foams, particularly polystyrene foams in sheet form, are presently being made from a number of blowing agents which have many undesirable characteristics.

Volatility, flammability, poor thermoforming qualities, brittle physical properties, high cost, or an adverse affect to the ozone layer are just a few.

However, potential atmospheric contamination by these by-products of foam manufacture has led workers to seek non-polluting alternative blowing agents, such as the usual atmospheric gases, e.g., nitrogen and carbon dioxide, and combinations of atmospheric gases with organic gases, e.g., the lower hydrocarbons or the freons.

However, the production rates of the processes are generally low, on the order of less than 200 lbs. / hr., and also have generally low post-expansion properties, on the order of 50% or less.

In addition, these processes require relatively high extrusion temperatures, on the order of 130° C. to 155° C. Thus, these processes are not very economical.

These patents state that the use of atmospheric gases, including 100% carbon dioxide or nitrogen as blowing agents has not been successfully employed, giving as a reason the extreme volatility of these gases, and further state that the use of these materials is said to produce corrugation and surface defects in the sheet product.

Images