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Halogen free flame retardants

Non toxic flame retardantsFlame retardants are substances or compounds that are added to other materials, such as plastics, coatings and textiles to prevent or delat the the spread of fire. The first applications of flame retardants predate the Gregorian calendar. Egyptians soaked wood in alum (potassium aluminium sulphate) around 450 B.C. and timbers were painted with vinegar arounsd 360 B.C. to increase their resistance to fire. Since then, many other materials have been used as flame retardants including clay, hair and gypsum. In 1735, Obadiah Wilde received British patent 551 for his mixture of alum, borax (sodium borate) and ferrous sulphate, which he used to improve the flame retardancy of paper and textile. His invention was first applied to improve safety of canvas used in theatres and public buildings.

Today, global demand for flame retardants has exceeded 2 million tons per year. A major part of this demand comes from the global plastic industries. Since all carbon-based materials are combustible, and the use of plastics is so widespread, there is a need to decrease the risk of fire related accidents. If it is not possible to select a polymer that is inherently flame retardant (e.g. polyamide), adding a flame retardant is a solution. The flame retardant can be mixed with the base material or chemically bonded to it. Broadly speaking, flame retardants can be devided in three groups, (1) inorganic or mineral flame retardants and (2) halogenated compounds. While the performance of halogenated flame retardance is excellent, many of these chemicals are associated with health and environmental problems. As a result, several brominated and chlorinated flame retardants have been banned in the past. Examples of banned compounds include polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs) and Decabromodiphenyl ether (DecaBDE).

Companies looking for less toxic products, often try to make changes to the articles materials and design or to select safer (inorganic) chemicals. Examples of such chemicals include aluminium trihydroxide (ATH), a mixture of huntitite and hydromagnesite and magnesium (di)hydroxide (MDH). These mineral flame retardants are non-toxic and work by decomposing endothermically. This means that at a certain temperature, the compounds fall apart thereby adsorbing heat and releasing water vapor. The oxides that are formed results in a protective layer that provides a smoke suppressing effect. Despite the obvious advantages of mineral flame retardants, it is not always possible to replace halogenated flame retadants. To reach flammability standards in demanding applications, mineral flame retardants need to be added in very high dosage levels (up to 80 w/w%).

If the use of mineral flame retardants is feasible, the most suitable compound is often selected based on its decomposition temperature. Aluminum Trioxide is generally cheaper than Magnesium Hydroxide, but starts to decompose at 180 oC making it unsuitable for thermoplastics like polypropylene which are molded at 200 oC. For these materials, magnesium hydroxide is often selected based on its stability up to 340 oC. Kisuma Chemicals is a renowned supplier of magnesium hydroxide products, which are marketed under the brandname Kisuma 5®.

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For more information about the use of magnesium hydroxide products to improve flame retardancy of your products, contact our Marketing and Sales department today.

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Brochure TDS MSDS
 Brochure Kisuma 5  TDS Kisuma 5A  SDS Kisuma 5A

 

 

Acid scavengers in polyolefins

Acid scavengerPolyolefins, also termed polyalkene, are polymers produced from simple olefins, such as polyethylene (produced by polymerizing ethylene) or polypropylene. The history of polyolefins starts with the accidental discovery of polyethylene by Hans von Pechmann in 1898. The German chemist synthesized it by heating diazomethane, which was also discovered by Von Pechmann in 1894. The white, waxy substance that he had created, was first named polymethylene. Due to the instability of diazomethane, however, no industrial relevant synthesis method could be developed based on the discovery of Von Pechmann. This would take three more decades, until Michael Perrin, a chemist at Imperial Chemical Industries (ICI) developed a reproducible synthesis in 1939 that was based on applying extremely high pressure to a mixture of ethylene and benzaldehyde. The foundation of this method was established in 1933 by two other ICI chemists: Eric Fawcett and Reginald Gibson. The method of Perrin made the first industrial production of Low Density Polyethylene (LDPE) possible in 1939, but the real breakthrough was the introduction of catalysts that allowed the polymerization at much lower temperatures and pressure. The first step for this was taken by Robert Banks and J. Paul Hogen of Phillips Petroleum, who developed a chromium trioxide based catalyst in 1951. Karl Ziegler’s catalyst, based on titanium halides and organoaluminium compounds, resulted in a synthesis method at even milder conditions. When Giulio Natta became aware of the Ziegler catalyst, he noticed the potential of the catalyst to polymerize α-olefins such as propylene stereoregularly. This resulted in the development of highly crystalline, stereoregular polymers that were previously not possible.  In the 1970’s, the catalyst of Ziegler was improved further by the incorporation of magnesium chloride. Homogeneuous catalyst systems, metallocenes, have been reported in 1976 by Walter Kaminsky and Hansjörg Sinn. In 1963, Ziegler and Natta were both awarded the Nobel Prize in Chemistry for their groundbreaking work. From the mid-1950's onward, the Ziegler-Natta catalyst have been used to produce various polyolefins.

Today, the worldwide production volume of plastics, elastomers and rubers produced from olefins with Ziegler-Natta or related catalysts exceeds 100 million tons per year. Polyolefins plastics are used in an extremely wide variety of applications, including packaging, cable insulation, clothing and medical goods. Before a polyolefin material from the reactor is suitable for its intended application, it needs to undergo several processing steps. The elevated temperatures, shear and exposure to oxygen can cause degradation processes that have a major impact on the polymer melt as well as the mechanical and aesthetic properties of the final article. By selecting the right stabilizing additives, these negatives effects can be largely prevented. The basis of a typical additive package for polyolefins include primary (phenolic-) and secondary antioxidants (phosphites or phosphonites) and acid scavengers. A common acid scavenger used in polyolefins is synthetic hydrotalcite, a material that is being used as stabilizer in polyolefins under the brandname DHT-4A since the late 1970's due to the pioneering work of Kyowa Chemical Industry. The key functionality of hydrotalcites is the irreversible adsorption of acidic catalytic residues. By doing so, hydrotalcites prevent many damaging side effects, most notably corrosion of processing equipment and degradation of the polymer itself. Furthermore, hydrotalcites, and especially high quality materials such as DHT-4A, can synergisticaly improve the performance of other additives and pigments in the formulation. A good example of this effect is the improved performance of Hindered Amine Light Stabilizers (HALS) in the presence of hydrotalcite, resulting in increased weatherability of the polyolefin article.   

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For more information about the history and use of hydrotalcites in polyolefins, please do not hesitate and contact our Marketing and Sales department right away.  

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Brochure TDS MSDS
  TDS DHT-4A SDS DHT-4A

 

 

Hydrotalcite in PVC stabilizer systems

Automotive cablePolyvinyl chloride (PVC), is the most produced plastic polymer in the world after polyethylene and polypropylene. The polymer was discovered in 1872 by Eugen Baumann when he observed that some vinyl chloride in a flask had started to polymerize in a white solid during exposure to the sun. However, the use of PVC in commercial products became more widespread only after the B.F. Goodrich Company had developed a method to plasticze the rigid, brittle polymer by blending PVC with several additives.

PVC is a relatively low cost polymer with good chemical and biological resistance and excellent workability. However, the unmodified polymer must always be converted into a compound by blending it with additives such as heat and UV stabilizers, flame retardants, smoke surpressants, plasticizers, processing aids, impact modifiers, thermal modifiers, pigments and fillers. The choice of additives depends on the required functionality, dictated by the respective application.

When exposed to heat (> 100o C), HCl is eliminated from the polymer backbone. This HCl triggers a further autocatalytic degradation process, causing rapid discoloration and embrittlement of the PVC. Heat stabilizers can greatly increase the heat stability by various mechanisms, such as scavenging of released HCl molecules. The type of heat stabilizer that is used depends on the application and required heat stability. Lead compounds were among the first stabilizers to be adopted by the PVC industry but due to health concerns, the industry has voluntarily committed to phasing out of lead compounds (VinylPlus voluntary commitment) in the EU-27 by latest end 2015. Hydrotalcite-like materials, such as the Alcamizer products from Kisuma Chemicals, are a crucial for the heat stabilisation of non-toxic alternatives for heavy metal compounds for PVC, such as Calcium Organic Stabilizer systems. This makes Hydrotalcites especially popular in high end applications such as high temperature automotive cables.

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For more information about the history and use of hydrtotalcites in PVC stabilizer systems, visit the Alcamizer product section or contact our Marketing and Sales department right away.

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Brochure TDS MSDS
  TDS Alcamizer 1 SDS Alcamizer 1

Applications

Kisuma Chemicals tests heat stability of Alcamizer in PVC compounds for customersOur non-toxic magnesium compounds find their way mainly to the engineering plastics and polymer processing industry. Their main applications include:

  • Heat stabilization of PVC products, as a replacement for lead containing compounds. Our hydrotalcite-like compounds specialy produced for application in a PVC matrix are the (co)-stabilizers of choice in Calcium Organic Stabilizers (COS) systems. These products are marketed under the brandname Alcamizer® and are used in COS systems for rigid as well as flexible PVC applications.
  • Flame retardancy of e.g. wire and cables used in automotive and ICT applications, as an alternative for bromine or phosphorous based compounds. Our flame retardant grades magnesium hydroxide, brandname Kisuma 5®, are unmatched in terms of quality and performance. Both production and application of these materials are covered by numerous patents.
  • Halogen scavenging in polypropylene and other bulk polymers. DHT-4A® and other materials from this family are hydrotalcite-like compounds applied as halogen scavengers in e.g. polyolefin systems. These materials are used to scavenge corrosive acidic residues from polymerization catalysts such as Ziegler-Natta, Friedel Craft and Mettalocene catalysts.

Besides these well known applications, to which we are and will always be an extremely dedicated supplier, we are highly interested in all developments with specialty magnesium compounds, particularly Hydrotalcite. From our factory in the Netherlands, we are able to support our customers in development projects that involve existing, but also newly developed hydrotalcite products. The intrinsic properties of our hydrotalcites are interesting for a range of applications, including anti-corrosion in Coatings, Adhesives, Sealants and Elastomers (CASE), Catalysts and Catalyst Supports, Controlled release and Sorbents.

 

 

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The Netherlands
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