FR2692583A1 - Procedure for increasing photo-degradability of plastics - adding titanium di:oxide or ferrous stearate to increase absorption of solar photons - Google Patents

Abstract

The procedure for increasing the photo-degradability of plastics consists of introducing an additive during the mfg. process which increases the number of solar photons with a wavelength of over 295 nm so that it is slightly above the normal level for the plain plastic. The procedure can be applied to high- or low-density polyethylene, a polypropylene copolymer or a homogeneous polypropylene, and the additive can be either of Ti02 or ferrous stearate. Prods. such as a wrapping material made from the photodegradable plastic should be marked with the date of mfr. and of final use. USE/ADVANTAGE - Suitable for wrapping and other purposes. Ensures faster and more complete breakdown of plastics.

Description

 Application of a photochemical reaction.

The present invention relates to the application of an additive
photodegradable for the manufacture of all semi-finished, finished products
or raw material of high or low density polyethylene, or
polypropylene copolymer or homogeneous making them photoded
gradants.

Currently, in the management of packaging waste
in plastic, we can distinguish two main ways:
- reuse.

 - elimination.

 Reuse can be done by internal recycling, chemical regeneration, re-molding.

All these processes require very significant investments (degassing extruders) and where the inevitable contamination of waste forces manufacturers to scrupulous filtration.

Disposal can be done by controlled landfilling, incineration
(with or without energy recovery), pyrolysis and degradation.

- Incineration remains difficult to implement because it
requires specific sorting and, for the same polymer,
there can be dozens of different grades. The
energy recovery in the form of heat does not reach
than 60% and this solution is not perfect because
materials go up in smoke and thus pollute the atmosphere sphere (example: PVC gives off chlorhy-
drique). This same acid damages the boilers and
special procedures are needed to prevent damage
rations.

- The yield of recovery by pyrolysis remains
still uncertain because very linked to the price of oil. Of
more, pyrolysis requires the creation of important units
your.

Degradation can take place in the following forms:
- Aquadegrability
- Biodegradability
- Photodegradability
Water damage is only used for bagging
hospitals.

Biodegradability supposing the complete destruction of
containing by living microorganisms, you cannot
predict when the process will start which can
occur during storage, transport, or
distribution. This property is incompatible with the
packaging function.

The method of the invention is characterized by the additional absorption of solar photons (whose wavelength is greater than 295 nanometers) by an adjuvant.

This additive is added in concentration such as the number of solar photons (whose wavelength is greater than 295 nanometers)
is a little larger than the number of photons naturally
absorbed by the virgin polymer.

The adjuvant used will be titanium dioxide or a stearate of
iron, which after absorbing the sun's rays will give birth
to free radicals within the polymer. The flow of these radicals
products is controlled, mainly by the light intensity
absorbed. These free radicals are capable of creating
macroradicals that will oxidize to give birth to
groups (hydroperoxide, alcoholic, cetonic, acid .....).

Certain groups, such as hydroperoxides and ketones can absorb sunlight: there is therefore a photochemical reaction, which causes the polymer chain to break.

 There is therefore destruction of the polymer in small fragments.

This degradation will be controlled by the percentage of adjuvant used and the thickness of the plastic packaging for a desired degradation period.

 The expiration date will be affixed on all products made photodegradable.

A tolerance of uncertainty over the duration of use of these products will also be affixed (more or less equal to one third).

Example.

For packaging with a degradability of three months:
Manufacturing date: 01/01/92
Expiration date: 03/01/92

Claims (5)

 Claims.  ultra-violet.  finished or raw material photodegradable by a ray  1) Application of an additive to make all finished products semi 2) Application according to claim 1 characterized with regard to the basic plastic. This can be e  high or low density polyethylene. 3) Application according to claim 1 or claim 2 characterized with regard to the basic plastic.  It may also be made of polypropylene copolymer  or homogeneous. 4) Application according to the preceding claims characterized  by the additive making the product photodegradable This  could be titanium dioxide.  5) Application according to the preceding claims characterized  by the additive making the product photodegradable. This one  could be an iron stearate.