CA2136260A1

CA2136260A1 - Chemodegradable synthetic thermoplastic polymer

Info

Publication number: CA2136260A1
Application number: CA002136260A
Authority: CA
Inventors: Peter K. Wehrle; William H. Dingler
Original assignee: Individual
Current assignee: Individual
Priority date: 1994-11-21
Filing date: 1994-11-21
Publication date: 1996-05-22

Abstract

The present invention refers to synthetic thermoplastic polymers incorporating a chemodegradable inorganic filler and a degradation initiator. It may also include a secondary activator and a bio-degradable filler.

Description

BACKGROUND OF INVENTION ~( 3G ~6 o It is known that starches, modified or unmodified, have been used in the plastic industry for several years with more or less success, especially since their inherent problem, high sensitivity to moisture, requires special processing as well as special packaging.
A related process is being described in the European Patent ApplicationNo. 300 940.8, Publication No. 1 18 240.
DESCRIPTION OF INVENTION
The present invention relates to the manufacture of chemically degradable synthetic thermoplastic polymer compounds containing an inorganic non toxic filler, a non toxic degradation initiator and in some cases a non-toxic activator. These compounds can be formulated to be blown, pressed, extruded or molded and their end uses determine the relationship between polymer and filler. The finished articles may vary from micron thin flexible films to hard solid objects.
A typical formula, for a compound based on the present invention comprises the following:
20 - 85 % by Wt. of 3 polyethylene 5 - 79 % by Wt. of a carbonate 0.1 - 10 % by Wt. of a metallocene In the present formula, the thermoplastic polymer is basically the binder and is represented by a polyolefin such as ULDPE, LDPE, LLDPE, UHMPE or a blend thereof.

Af ' .~

The carbonate included in the present formula acts as a chemically degradable filler and should be of a finely divided particle size, generally 0.5 - 10 microns. It can be chosen from several, but the preferred ones are:
CaC03, K2CO3, MgCO3, Na2CO3.
An activator such as P205 can be added in small amounts and dry blended into the filler.
During the initiation process, any available moisture activates the phosphoric acid to react with the carbonate to release carbon dioxide and water. This reaction is continuous until exhaustion of the chemicals involved in the degradation process.
The metallocene with the general formula (C5H5)2M is a dicyclopentadienyl derivative of a transition metal that reacts with the carbonate to initiate the degradation process, which then becomes ongoing. The amount, as well as the types of metallocenes and carbonates used, determines the rate and type of degradation. Temperature, light, humidity, and weak acids all influence the type as well as the rate of degradation. The metallocenes available are:

(C5Hs)2 M, (CsHs)2MX1 3~ CsHsMR1 3 They all do work, but environmental reasons restrict the choice of the metal since some are toxic. Therefore M = Co. is the preferred one for its fast reactivity, but a slow reaction is achieved when M = Fe.
For specific uses, biodegradable organic fillers can be incorporated as well as plasticizers, lubricants, anti-blocking agents, pigments, dyes and other additives that improve the product, the compounding or the processing, but only if they do not interfere with the degradability of the finished product.
While the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art, especially in light of the foregoing description. Accordingly it is intended to embrace all such alternatives, modifications and variations as fall within the spirit and broad scope of the invention Page ~ WHD/94 -TESTS
Three tests were conducted to determine the rate of degradability under controlled laboratory conditions and under field conditions:
1) 20% CaC03 (mean average particle size 2 microns), 78.5% LLDP and 1.5% (CH 3(CH2)16COOH)2Co, were melt-blended in a heated internal blender for 5 min. @ 300 F. The resulting compound was then pressed in a heated Carver Platen Press to a film thickness of 2 mils and a sheet of it was then placed in heat controlled oven, set @ 70 C. After 7 days the film had degraded to such an extend that it could not be retrieved in one piece, but crumbled on removal.

2) 20% CaC03 (mean average particle size 5 microns), 77% LLDPE and 3% (CH3(CH2)~6COOH)2Co, were melt-blended in a heated internal blender for 5 min. @ 300 F. The resulting compound was then pressed in a heated Carver Platen Press to a film thickness of 2 mils and a sheet of it was then placed in a heat controlled oven set@ 70 C. After four days the film had degraded to such an extent that it could not be retrieved in one piece, but crumbled on removal. It was observed that doubling the amount of initiator accelerated the decomposition time by approximately 40%.
3) 20% CaC03, (mean average particle size 2 microns),C78.5% LLDPE
and 1.5 % (CH3(CH2)16COOH)zCo were melt-blended in a heated internal blended for 5 min. @ 300 F. The resulting compound was then pelletized and blown film was made on conventional processing equipment. 25 sheets of the degradable film were added into a windrow. This represented a distance of 20 mete~ in length. During the course of a two month period the windrow was tormc~ by a front-end loader aprox. every 3 - 4 days. By the third week it was already difficult to find even small pieces of the film in the windrow, as it was being turned. By the fifth week, any evidence of the degradable film in the windrow had vanished.
Throughout the testing period the temperatures in the windrow at both test locations were at optimum levels for a good composting rate, which made it a fair test to evaluate the breakdown of the plastic.

Claims

1. A chemodegradable thermoplastic polymer composed of:
a) 20 - 94 % of a thermoplastic polymer b) 6 - 80 % of a carbonate filler c) 0.1 - 10 % of a metallocene d) 0.1 - 3 % of a phosphoric anhydride (optional)

2. The thermoplastic material according to claim 1, where a thermoplastic polymer is selected from the group consisting of a polyethylene such as ULDPE, LDPE, HDPE, LLDPE, UMHPE etc. a polypropylene and, or a, natural polyamide

3. The thermoplastic material according to claim 1, where the carbonate is preferrably selected from a group comprising: calcium-, magnesium-,sodium-, or potassium carbonate.

4. The thermoplastic material according to claim 1. where the metallocene is selected from the first transition series of the Periodic table, preferrably No. 26 and 27 in Group VIII A.

5. A thermoplastic material as described in claim 1. that can be readily processed in conventional equipment i.e.:
Bambury, FCM,high intensity mixers,extruders,injection molders, blown film lines, or similar equipment.

6. A pelletized thermoplastic polymer, (produced according to Claims 1 to 6), designed to be used in the manufacture of garment bags, garbage bags, leaf mulch bags, disposablel diapers, landfilcovers, reforestation protection, hospital gowns or sheets, packaging material, and disposable molded articles.