What chemicals are used in the Dunlop process to make latex foam

Mattress Talk
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I was curious to know exactly what chemicals are used to make a Natural Latex (Dunlop) foam. Many websites that sell Dunlop Latex foam mattresses will state that they are 100% Natural Dunlop latex. This is a bit ambiguous because, and I’m going to quote a page from MFC’s website, “All latex mattresses on the market (even organic ones) contain 5-10% of natural or synthetic materials. Why? Because it’s impossible to make a latex mattress simply with the milk from the Hevea brasiliensis tree.”
In my search I have found that this is the best website for listing the chemicals used to make Dunlop latex foam.
Before it gets to the factory chemicals are added. Liquid latex is composed largely of water (60% in weight), rubber particles (35%), and other solid particles, including proteins, sugars, amino acids, lipids, and minerals. The presence of this small number of solid particles makes latex susceptible to rapid decomposition, which is caused by airborne bacteria and other microorganisms. This process leads to putrefaction and coagulation, rendering latex unsuitable for handling and further processing. To avoid decomposition, natural rubber manufacturers are therefore forced to use chemical additives, such as tetramethylthiuram disulphide, zinc oxide, and ammonia. This keeps latex in a stable liquid phase for long enough to allow the removal of excess water and its conversion into raw rubber.
In TABLE 1. GENERAL-PURPOSE FORMULATION TO PRODUCE LATEX FOAM on the linked website there are a fair amount of chemicals that are used in the Dunlop process. Secondary gelling agents can be cationic soaps, polyamides or guanidines.The antioxidant is usually a product called Wingstay L

In the table p.h.r." stands for “parts per hundred rubber” and is a common unit of measurement in rubber compounding, indicating the ratio of ingredients to the rubber content in a formulation.
To calculate the percentage of chemicals used total the p.h.r. numbers, 113.5, total the p.h.r. of all the chemicals, divide by 113.5 x 100%, 13.5/113/5 x 100% = 11.9%
88.1% of the formulation is natural latex and 11.9% are additives.
After curing the foam is removed from the mould, washed thoroughly to remove the serum and soaps and goes through heavy rollers to remove excess water. The foam is then dried.
The question remains that after the washing how much of the additives are left, and what is the percentage of natural latex in the finished dried foam? I’m not a latex foam chemist so I don’t have those answers.

@RF-Jens

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Hi BobP,
I will try to make it clear:
Latex, is it HA or LA (high ammonia or low ammonia), has a DRC (dry rubber content) of min. 60%. The rest is Non Rubber Content (NRC) around 1.4 % and water. Ammonia is a preservation chemical (same as TMTD) which is added to the latex at the plantation/centrifuge station.
We (like almost all others in the latex foam industry) are using LA-latex.
Vulcanization without chemicals is not working, that’s a fact. You need at least sulphur to get the polyisoprene molecules (the natural rubber/latex) connected.
Zinc-oxide, together with ZDEC and ZMBT (accelerator) speed up this process dramatically because these 3 working synergistically.
An antioxidant (Wingstay L, Vulkanox, ore others) is common.
A soap, for example potassium oleate, is used as foaming agent, you cannot foam latex without any soap.
The gelling agent is needed to fix the foam structure before it can be vulcanized (slowly with steam or fast with RF).
The result, if it is done well, is a non-toxic natural latex foam. See attached example.
Each factory may use a slightly different formulation, some may add some small portions of foam stabilizers, in general, it’s all the same, whether its DUNLOP or TALALAY.
Hope this helps.
Best,
Jens

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Thanks for the info. I worked as a research chemist, now retired, for Bayer in their research/production isocyanates/polyol plant in WV, but when it comes to latex foam chemistry I’m a newbie.
So back to my questions. Do latex foam manufacturers test their finished foams for chemicals used in the process? Assuming yes, what analytical methods do they use and what are their typical findings?

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Hi BobP,
In that case, you know probably more about chemistry then me.
However, I had a friend from BAYER Germany who teaches me a lot at the beginning, he told me at BAYER they have a saying: “If god wants to treat you bad, he will let you work with latex.”
Back to your question.
Factories of course do several tests for quality, detailed chemical test are beyond their capabilities. In 1996 I was co-founder of the QuL e.V., a German quality control association for natural latex mattresses, still active.
Together with the other co-founder, the ECO-Institute in Cologne, we introduced the ECO Test Certificate also for latex foam. All major players in Sri Lanka, Thailand, Malaysia, Vietnam etc. pp. has this test certificate.
As an example, please check one test from PT RubberFoam, an old one, meanwhile the criteria get more detailed and tighter, let me know your email address, don’t know how to attach a file here. Details can be found on eco-INSTITUT Germany GmbH

Best,
Jens

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Thanks again for the info. I never heard that saying in Bayer USA, might be a German thing. The eco-INSTITUT tests submitted samples of products for VOCs. Correct? The eco-INSTITUT label at a glance
So we, as consumers, when searching for a latex foam mattress should make sure that the foam in that mattress has the the Eco-Institut tested product label.

You probably have already heard that Bayer Material Science, renamed Covestro, is being sold to Abu Dhabi’s ADNOC for 14.7 billion euros ($16.3 billion), including debt. Hopefully my pension will not be affected.

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Great post! My understanding is that washing process is key to the cleanliness of the finished product, and is a sometimes (hard to track) skipped step for some companies. The highest natural rubber content that I have heard is 96.6%, (a Talalay latex via eco-INSTITUTE).

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Is the 96.6% rubber the content after vulcanization? I see a lot of online retailers referring to their latex mattresses as 100% natural latex.
During vulcanization, latex’s (natural or synthetic) polyisoprene molecules are heated and cross-linked with molecular bonds to sulfur, forming a 3-D matrix. So tecnically, correct me if I’m wrong, after vulcanization you have a product that’s called rubber but chemically different then natural latex. After washing/drying the foam to remove excess additives what is the approximate percentage of vulcanized latex rubber in the latex foam sold by online retailers?

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I think that the industry looks at the 100% natural latex claim as one that the latex foam is derived entirely from natural latex (Hevea brasiliensis) with no synthetic latex added at any point prior to vulcanization. It does not mean the product is 100% pure rubber by weight after manufacturing.

I am not a chemist or scientist in this area, but like many other things in the mattress industry (and others for that matter) the marketeers like to overstate everything.

One of my favorite misunderstood elaborations, over statements or embellishments, call it what you want, is Tempurpedic’s claim their Tempur Breeze feels 10degrees cooler all night long. Then comes the clarification:

++ LuxeBreeze® feels up to 10 degrees cooler based on the average heat index increase of TEMPUR-LuxeBreeze® compared to TEMPUR-ProAdapt® models measured over an 8-hour period. ProBreeze® feels up to 5 degrees cooler based on the average heat index increase of TEMPUR-ProBreeze® compared to TEMPUR-ProAdapt® models measured over an 8-hour period.

I am not sure what the actual measured temperatures are, but most everyday folks are led to believe, if they are hot on their current mattress, the magic of tempurpedic is going to get them 10 degrees cooler.

From my perspective is similar to when a fast food restaurant claims their burger is a quarter pounder they always add that asterisk with the clarification that it is pre cooked weight.

I suppose that the small amount of chemicals needed as a percentage of the whole maintains the classification of 100% as the standard to make the claim has the same standard for everyone.

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I would assume so, but I’ve never clarified to that extent with any latex manufacturer, and to the best of my understanding the reported percentage by eco-institute would be for a finished, consumer ready product. What are your concerns about the rubber content of the finished latex product? Is it a health concern, or a performance concern? I guess it’s a balance of things for all consumers to different degrees, like comfort vs. toxicity, sleep temp. vs. pressure reduction, etc… For myself as a manufacturer, would I choose a hypothetical lesser product, performance wise, for a 10% improvement in rubber content? Also, If I didn’t like the feel of an entirely foamless mattress (obviously subjective), what is the alternative? I do agree that the industry does play fast and loose with things like “100%” anything and “chemical free”, and wish this whole thing were somehow more simple—like mattresses were made of unfinished maple or something like that… lol.

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I can accept that, as long as the retailer states that the latex foam is made from or derived from 100% natural latex, but retailers should not be allowed to say that the latex foam in their toppers or mattresses is 100% natural latex.

A liitle Googling and found this from Savy Rest. The Myth of 100% Natural Latex “The most you will see in the industry is 95-97% natural latex in a mattress. That other 3-5% is the curing package.” This answers my question about rubber content in a finished foam. It should be worded natural vulcanized latex, but as you pointed out the word natural latex seems now to be the industry standard.

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Yes I know the some industries who do the testing of foam, they are using metallic press to see how long pressing it can last. But only some companies do other just making and selling

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I was just curious if anyone here knew what the ~rubber (vulcanized latex) content is on a finished latex foam after washing and drying.
If the latex foam has an up to date eco-INSTITUT tested label then it has met their strict requirements for emissions (outgassing), harmful substances, and odour; and I’m not concerned about VOCs from that foam.

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I am not quite sure the FTC offers a legal definition of 100% Natural Latex. Of course they do not allow erroneous misinformation either.

I would say, that in practice 100% Natural Latex does not mean the product is made of only raw tree sap. As suggested 3-5% additives are needed for vulcanization. The does not mean that the raw tree sap used was not 100%, it just means the percentage of the final produced product has some percentage of additives as part of the whole. If every manufacture uses 3-5% of additives in the process of vulcanization, and call it 100% natural latex, everyone is really on the same playing field. Sure I suppose if the FTC comes out with a policy or regulation that manufacturers must use something like 97% Natural Latex, and every manufacturer must use that language, it may actually be more confusing, and at what gain?

I am not necessarily taking a side either way but this seems to happen in many areas.

The FTC and industry certifying entities often allow small percentages of processing agents or additives provided they are necessary to create the final product, otherwise there would be not other way to make it. Plus it really does not change the nature of the product itself.

I mean, think of cotton. If they dye cotton to a specific color, technically, it is not longer 100% cotton. Certain juices, 100% Orange or Apple, (you name the juice) but they add vitamin C or what ever other vitamins they add, but it is still called 100% juice. Candles made from beeswax, but then they add fragrance oil, but it is still called 100% beeswax.

They would have to recreate the entire system of what 100% of anything is.

If the certifying bodies all the 100% category, the same rules would apply for all of those whose products require the minimal amount of processing agents.

If GOLS requires a product to contain at least 95% certified natural latex in order to be labeled as “100% natural latex,” then getting that certification serves as some sort of official proof of what the product is, and just as importantly, what it isn’t.

However, some manufacturers don’t get their latex certified, even if their product meets the requirement. That creates a different set of issues. Did they skip certification just to avoid the cost, thinking, “Why pay for something we already know we meet?” And are they still labeling it as 100% natural latex?

If they aren’t certified, then how do they prove their product is truly 100% natural latex? Without third-party certification, there’s no verified documentation, unless they keep their testing results, and then whoever is asking is relying on a company to verify their own product. So any claim becomes something consumers have to take on trust. In those cases, if a manufacturer isn’t required to report to a specific organization, unless local laws demand it, then what? Although, they are still accountable to regulatory bodies like the FTC (in the U.S.) if their claims are found to be misleading, and they may also face scrutiny from retailers or consumers who ask for proof or file complaints.

While I understand your point, in this case, I am not certain labeling 100% Natural Latex, knowing the standard for it is greater then 95%. If someone were to say, 95% vs 97% makes a credible difference, I think you have a point. I am not quite sure that difference does in fact make a credible or practical difference.

Maverick

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I would just like to see others follow Savy Rest’s lead. I doubt that the FTC, now short handed, will, as you said, “offer a legal definition of 100% natural latex.” Caveat Emptor

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Interesting, they do not use any percentages to describe their latex. They just say it meets the standard. I wonder if they do that because they feel using 100% natural is not very technically accurate or would rather just point to the certification.