The early PAMPERSU diaper, and the other products that shared the market were bulky, heavy products composed of fluff pulp with a rayon topsheet, polyethylene backsheet, some
This product evolved to a rayon-polyester topsheet, then to an all-polyester topsheet with only minor other changes to the product design, composition, and weight. Meanwhile, the share of the total diaper changes represented by disposables continued to increase at a very high rate. It was in this time period, the early 1980's that the first stirrings of discomfort with the effect of disposables on the environment began to be heard.
It was also about the same time that Procter & Gamble and Kimberly-Clark introduced their LUV'SU and HUGGIESU contoured, elasticated diapers, respectively. These were the first products that attempted to absorb liquid exudates more efficiently. Heretofore, the rectangular, non-elasticated diapers had only brute force in the sense that they would need more weight of fluff pulp to absorb more. With these new products, the elastic at the legs meant that a reduced amount of fluff pulp would actually give higher absorbencies. Here, my definition of absorbency is the same as the mother's; if the diaper leaks, it isn't absorbent enough, if it doesn't leak, it is absorbent enough. These diapers had much higher containment than the rectangular. This was really the first instance of the disposable diaper industry being more responsible environmentally by reducing the mass of the diaper.
Before SAP, the optimum density for an all cellulose absorbent core was in the 0.007-0.010-g/cc range. In today?s diapers, the density range is from 0.020-0.030, or the core is from one third to one fourth of the thickness it once was. What does all this mean to a reduced diaper size and/or weight. Let us look at the equation. First, SAP will replace cellulose on a 5 or 6 to 1 absorbency basis (perhaps more on a retention, that is considering rewet, basis. This is, of course ignoring the relative costs. Since SAP has been on a continuous declining price line while cellulose is a cyclical material whose cost varies from $450-1000/ADMT, this economic replacement cost varies, but is about a 4 to 1 basis, that is, on an equal cost basis, 4 grams of cellulose can be removed for each gram of SAP added without any effect on product cost. Thus, we can clearly see that the introduction of SAP into disposable diapers made them more friendly to the environment because of reduced material usage. It also made the performance of the diapers much better.
There was another factor that came into play shortly after this time, which was also very environmentally friendly. This factor is the increased product density I talked about earlier. When P&G first came out with their test market of the "brick pack" in then landlocked Berlin, it was a clear sign that the market had changed forever. The product was the first compressed product. There was a reduction of 40-50% in the volume of the diapers in the bag. Not only did this compression not affect the performance of the product, it improved the rewet of the diapers. In addition, it is clear that there was a tremendous reduction in the use of plastic for bags, and corrugated for shipping. Also, a truck could now hold almost twice as many cases for shipment. Since that time, there have been further reductions in the volume of the product which means that now there are perhaps a five-fold increase in the number of diapers on a truck, and an 80% reduction in packaging usage per 1000 diapers. These factors certainly made the disposable diaper, and the industry that produced them, good citizens of the environment.
Despite all these improvements to both the functionality, and size and bulk of the diaper, it was during the time that these improvements were taking place that the movement began to have disposables outlawed. There were some statements made by environmental advocates about the percentage of diapers in the landfills, the supposed fact that they (diapers) alone would cause the landfills to prematurely fill up. As all of us know in the industry, disposable diapers are a very minor component of the solid waste stream. If I remember correctly from those days, the actual percentage of diapers was in the 1.5-2.0% range. With newspapers being the second largest component of solid waste, there was a good chance that the newspaper stories talking about diapers filling up the landfills, were, themselves, taking up more room in the landfills than the disposables they talked about. But, because of the extreme pressure mounted by environmentalists, work was begun to make diapers biodegradable, or compostable. Again, it was P&G that pioneered, and led the industry effort. As part of the group working on compostable diapers, I saw that this was a possibility. But, I believe that the FTC chided P&G about putting the claim that the diapers were compostable on the bag. They said that such a small portion of U.S. solid waste went to compost facilities, that the claim (while true) raised false expectations on the part of the consumer. P&G dutifully removed the statement from their bags. Fortunately for the industry, the hue and cry against disposables quieted down. In part, this was due to the study, which showed very little difference in energy usage between laundered cotton diapers and disposables.
For more than 10 years now, there has been no great groundswell for outlawing disposables. But, environmental advocates have not given up. They still mount campaigns when they can. We have just seen one of these in Germany. We will probably see more.
The disposable absorbent products industry is still interested in making their products more environmentally friendly. This paper describes a possible method to do just this. My colleague, Carlos Richer, General Director of Absormex S.A. de C.V., the company that first commercialised this product in a disposable article; will now describe the material, which made this possible, and the results of the tests performed to prove the degradability of the product.
Degradable plastics! Environmentally Friendly! Haven't we heard this before? Let me ask you, do you truly believe that such plastics exist? I do not know about you, but let me tell you that I surely did not believe it when this idea was first presented to me two years ago. What has happened in the last two years that changed me from a no believer to a public supporter? How did I end up in front of this audience to talk about degradable plastics and convince you of how good they really are?
The idea of a biodegradable diaper is not new. Some of you in the audience, especially those who have been in the industry for some time, may remember what happened at the beginning of last decade. At that time, some disposable baby diapers were advertised to be "environmentally friendly", but were not able to live up to the biodegradable promise when asked for supporting evidence. Even today, there are still some diapers produced in the European market, which continue to use that same old technology that failed years ago in the US. Of course I am referring to the use of films composed of a starch/PE blend. The starch is mixed with the plastic pellets and then melted in the extrusion process to produce a starch-polyethylene film. Everybody knows that starch is biodegradable, this is unquestionable, the problem was that given enough time, starch/PE films resulted in fragments that did not change any more. As a matter of fact, the resultant fragments did not biodegrade. To make it worst, it was argued, but finally accepted, that the life cycle of a typical US diaper ends in the landfill. Under landfill conditions, the diaper with the film composed of a starch-PE blend failed to deliver its promise; it just did not biodegrade.
We all have heard of biodegradable plastics made from natural components or their derivatives; these products are currently available. We all know however that such products are extremely expensive, and definitely not practical for use in a disposable baby diaper. In addition, their properties (strength, coefficient of friction, pinhole resistance, etc) are very different than the ones we are accustomed to in the diaper industry. Finally, with the current conditions of the world as they are, it is not a good idea to use significant amounts of arable land to grow plastic precursors on the basis of either environmental or energy conservation.
In 1998, I was confronted with the following project: "Do you want to manufacture a disposable diaper using degradable backsheet and topsheets?" My immediate thought was: "Whose leg do they think they are going to pull? OK, let them think that maybe mine, I will play the game just to make sure these guys know how wrong they can be". I decided to play the role of devil's advocate. Why did I take such position?
I knew that by choosing the right questions I was going to be able to prove to these people that the project was just wrong, or at least not practical. My first list of questions was the following:
Let me start defining some simple terms:
What is degradation?Degradation is the process in which a product is capable of being chemically degraded, changing its mechanical and chemical properties. A product is degradable when it can change its properties in a time scale due to the action of heat, light or mechanical stress
What is biodegradation?Biodegradation is the process in which a product is capable of being broken down into innocuous sub-products, like CO2 and water, by the action of living things (as microorganisms). A banana peel will biodegrade into biomass, CO2 and water. Products that are susceptible of biodegradation are also referred as "bioactive".
Why are plastics non-degradable?A plastic product consists of a very large number of molecules, with a molar mass in the hundreds of thousands in the case of polyolefins. (polyethylene and polypropylene). Because of this composition, polyolefins are strong, tough, inert and not water-wettable. It is a combination of these characteristics that make polyolefins resistant to microorganisms (i.e. they are bioinert). Indeed, polyethylene is frequently used as a control standard of non-biodegradability. A simplistic analogy is to consider an ant at the middle of the terminal station, looking at 100 trains put together one after the other, and trying to find the ends of this super-train.
How can you make degradable plastic products?One way, at least the one I am presenting with this paper is using TDPA™ (Totally Degradable Plastics Additive). It is a technology that uses an additive package that is mixed with the plastic pellets before the extrusion process. E.P.I.- Environmental Products Inc offered this patented technology to us. Since we are not producers of raw materials, to make the treated plastics we formed strategic developmental teams with our raw material suppliers.
How does it work?Plastics treated with TDPA™ change their molecular structure after exposure to ultra-violet-light, heat and mechanical stress. Once the product is exposed to any of these conditions; just light, just heat without light, or any combination of heat, light and stress, it becomes brittle and breaks up into much smaller molecules due to an oxidative degradation mechanism. The resultant fragments have an important reduction in their molecular weight.
When the treated PE and PP plastic starts to break, literally the molecular chain fractures into smaller pieces, changing into carboxylic acids and alcohols. They may be expected to continue to reduce their length until they become "bioactive", though not totally proven at this point. These molecules are anticipated to become short enough to be assimilated by microorganisms. The resultant fragments are expected to change into biomass and into CO2 and water, leaving absolutely no toxic by-products.
What evidence do we have that they actually degrade?First thing we did was to expose the treated PE and PP samples to a weatherometer (ASTM-5208). Then we measured percent elongation and tensile properties (ASTM-1682-64)
Gel Permeation Chromatography (GPC) tests proved an important reduction in the average molecular weight of the samples.
At simulated outside weather conditions the samples not only degraded, they degraded too fast! Future trials helped us fine-tune the TDPA™ active ingredient to our current needs, to avoid insufficient shelf life. Our current product degrades in actual outside weather conditions in less than a month (23 days).
We also carried tests using forced convection ovens (ASTM-D5510-94) at different temperatures (without any light). We were able to correlate the effect of the temperature in relation to the degradation process. Using the "Arrhenius equation" as a mathematical representation of our data, we were able to forecast shelf life at different temperatures and fine tune the dilution rate for TDPA™. Gel Permeation Chromatography tests were made to the heat aged samples, proving again an important reduction in molecular weight, similar to the QUV aged samples. These experiments demonstrate that the product degrades with ultra-violet-light, and also with heat with no light, they have also helped us in forecasting the time required for degradation at different temperatures.
What evidence do we have that TDPA™ is safe to use?It was proven using extraction testing by PIRA International (UK) that TDPA™ treated films have additive extraction values low enough to meet food contact standards. We sent samples to an external Lab to check for toxicology and cytotoxicity tests. The current evidence indicated that it was completely safe to use, it meets the requirements of the Elution Test, and is characterized as one devoid of irritating and of sensitizing propensities that could be detected by the methods used in the study. The product was not classifiable as a Human Carcinogen by ACGIH, IARC, EPA or NTP. Actual usage of diapers by babies under close medical supervision indicated once again, that the product is safe to use.
What evidence do we have that our plastics degrade in the landfill?We contracted the services of the University of Georgia, under Dr. Ernest W. Tollner's leadership, to perform a battery of tests under the ASTM D-5525 "simulated active landfill test" standard. They continue to do more landfill experiments at this time.
Do they "biodegrade" in the landfill?Does a banana peel biodegrade? Do leaves from a tree biodegrade? Will a newspaper biodegrade? Will our treated plastics biodegrade in the landfill? This is a difficult question because a definite yes may be an overstatement; something we can say is that we were able to prove, using the ASTM D-5525 "simulated active landfill test", that the polyethylene film and polypropylene nonwoven degraded under simulated landfill conditions.
We were also able to see some bioactivity that suggests that the product will continue to biodegrade; we do not know at this time the extent of this biodegradation and we have no means to prove it at this time. We believe it will biodegrade in most landfill conditions, however we also recognize that if the landfill is not managed properly, even a piece of meat will not biodegrade. Does this mean that the meat is not biodegradable? Of course not! We believe that with the current trend of regulations for landfill operators, our treated plastics will biodegrade, but confirmation is still required through additional testing.
© Carlos Richer and Market Technology Service, 2000