TopDown A Historical Review of Silicones

Silicones are industrially produced compounds derived from the element silicon. Although silicon is the second most common element in the earth’s crust, its high affinity for oxygen means that it is only found in compounds with oxygen, namely as the silicates and silicon dioxide that make up minerals and sand. Elemental silicon was discovered at a relatively late stage because of the very high silicon-oxygen bond energies. In 1823, the chemist Jöns Jakob Berzelius obtained amorphous silicon by reducing silicon dioxide with carbon in the presence of iron. When hydrochloric acid was added to dissolve the iron, the reaction mixture was found to contain silicon in powder form. However, it was to be more than 100 years before this newly discovered element would embark on its triumphal march. For a long time, the main stumbling block preventing the production of metallic silicon chunks was the high melting point of 1410 °C. Nor was there a suitable process capable of producing silicon in large quantities.

Not until the discovery and widespread use of electricity was it possible to generate the high heat of fusion of silicon or an economic process for its manufacture. Despite these difficulties, a number of chemists were researching the chemistry of silicon in the 19th century. They were hoping to develop a chemistry of silicon to rival that of carbon.

TopDown Discovery of Silicones

It was the English chemist F. S. Kipping who, at the start of the 20th century, really dedicated himself to silicon chemistry. He synthesized a large number of Si-C compounds that do not occur naturally. His products were mostly resinous products that would not crystallize and would not distill. The first silicones had been discovered!

Kipping’s first syntheses concerned chloro-organosilanes, which he would hydrolyze. By analogy with chloroalkyl compounds, he expected hydrolysis to yield the corresponding alcohols. However, the hydrolysis products, silanols, spontaneously condensed to larger units, with the release of hydrogen chloride gas. At that time, none was intererested in either the properties or the applications of these compounds and so Kipping did not pursue the matter any further.

TopDown The Breakthrough in Silicones

In the early 1940s, the USA started researching and testing the properties of silicones to help with the war effort. Initial interest focused on their hydrophobic properties and protective action against static electric discharges. Consequently, the first silicone product was a paste that protected electrical sparking equipment in airplanes. The producer was Dow Corning. It processed silicone precursors obtained from General Electric. At GE in 1940, Eugene G. Rochow discovered a synthesis route for chloromethylsilanes that utilized silicon and chloromethane (methyl chloride) as its starting reagents. Independently and at the same time, the German chemist Richard Müller discovered a similar synthesis route, now called the Müller-Rochow synthesis.

From then on, there was no stopping silicones. It was now possible to produce silicone precursors cheaply. From then on, the goal was to incorporate specific organic groups to expand the silicones’ range of applications.

TopDown The Discovery of Silicone Chemistry in Germany

The development of silicone chemistry in Germany is synonymous with the name WACKER, whose headquarters are located in Munich. WACKER’s German silicone production sites are the plants in Burghausen (Bavaria) and Nünchritz near Dresden.

After World War II, it was difficult for WACKER to start up its silicones business again because the allies had confiscated all chemical patents.

The USA had a huge headstart in terms of expertise. WACKER had to start off by acquiring patent licenses. However, it still had to develop its own chemical and process engineering expertise.

A prominent figure in this regard was S. Nitzsche, who devised a silane synthesis for the company. The first round-the-clock silane furnace started operating in Burghausen in 1949. WACKER chemists then set about modifying the silicone backbone with methyl, phenyl, vinyl, amino and other functional groups to expand the range of applications of the new polymers.

Today, WACKER is a world leader in silicones. It sets trends in the fields of research, analysis and environmental protection.

A chronological overview of WACKER’s rise is presented in the following table.

TopDown Chronicle of WACKER SILICONES

1913 Foundation of the Consortium für elektrochemische Industrie GmbH
1914 Foundation of Wacker Chemie AG on October 13

Start of silicones research in Burghausen


First silane furnace comes on stream in Burghausen (see photo above)


First pilot plant for silicones
Silicone fluids and resins developed
Work starts on optimizing the direct synthesis of chloroethylsilanes


Expansion of silicone production
Product range extended to include impregnating agents for the textiles industry, release agents for the rubber industry, antifoams and emulsions


First masonry protection agents launched
Start of HTV rubber production
Sales of silicones reach DM 2.1 million


The first RTV rubbers developed
Synthesis route found for phenylsilanes


Expanson of silicones production, construction of distillation towers and tank farms for silanes
Product range now numbers 200
Sales of silicones reach DM 7.8 million


Development work starts on silicone joint sealants sold under the brand name ELASTOSILâ
First combination resins for the coatings industry


Sales of silicones reach DM 37.8 million


Direct synthesis switched to the fluid-bed process
Pure silane distillation comes on stream
WACKER Chemical Corp. New York acquires a 33 % holding in SWS Silicones Corp. Adrian/Michigan, USA


New generation of addition-curing silicone rubbers
Start of pyrogenic silica production HDKâ in Kempten, Germany


WACKER Mexicana: Start of silicones production


New silicone plants for synthesis and distillation in Burghausen; extended in 1974


Methanolysis plant comes on stream


Foundation of Bayplan, a Bavarian company specializing in masonry protection


Silicone rubber in the ascendancy
The decisive component HDK® is now also produced in Burghausen


Start of silicones production at WACKER Quimica do Brasil Ltda


Substantial expansion of capacity of silicone plants


WACKER Chemical East Asia, Tokyo: Production of RTV- and HTV silicone rubbers


WACKER holding in WACKER-Stauffer Silicones Corp. increased to 50 %


Foundation of WACKER Silicones Corp., Adrian, Michigan, USA, as 100 % subsidiary
Foundation of Drawin Vertriebs GmbH, Ottobrunn, Germany, for small-scale silicones sales
Creation of the WACKER silicone prize for outstanding research achievement in organosilicon chemistry


Restructuring: silane, silicone and silica activities amalgamated into the Silicones Division
In Burghausen, industrial plants for methylsilicone resins and phenylsilanes come on stream


Silicones in high-tech SEMICOSILâ in electronics, POWERSILâ in the power transmission and distribution industry, silanes for pharmaceutical syntheses


Silicones production starts at Wacker-Chemie Italia SpA.
Start of hot-rubber compounding in WACKER Quimica Iberica


Quality management system certified to ISO EN 9001


Production of LC pigments starts
Sales of the Silicones Division: DM 1.4 billion
Employees: 3,000
100 % acquisition of SILMIX SpA, Italy
Wacker Silicones celebrates 50 years


In Japan, silicones production is concentrated at the Akeno site

Wacker Silicones Corporation, Adrian, USA, a wholly owned subsidiary of Wacker Chemie AG, Munich, and Kelmar Industries, Duncan, South Carolina, USA, agree to found a joint venture for specialty silicones
Founded in 1988, Kelmar Industries, which has 66 employees and focuses on the production and marketing of textile auxiliaries based on silicones, posts sales of around USD 30 million in fiscal 1996/1997
1998 On November 27, 1998, Wacker-Chemie signs a contract to acquire the Nünchritz plant (in Saxony) of Hüls AG for the benefit of the Silicones Division
1999 Asahi Chemicals Industry Co.Ltd., (Asahi Kasei) in Tokyo, Japan, and Wacker-Chemie sign a 50/50 joint venture agreement on September 17, 1999, to develop, manufacture and market silicone products. The new company is called Wacker Asahikasei Silicone Co., Ltd, and is headquartered in Shinjuku-ku, Tokyo

Shanghai Technical Center. The technical service center, a joint project with Wacker Polymer Systems, officially opened its doors. This center will support the expansion of Wacker activities in Asia’s rapid-growth silicone markets – particularly in the construction sector.

In June 2000, an innovation and advisory center for silicone applications in the cosmetic industry was opened in Burghausen.

2001 WACKER SILICONES launched a range of silicone rubber in pellet form.
2002 The expansion project at the Nünchritz site in Germany (begun in 2001) continued on schedule in 2002.
2003 On March 10, 2003, a symbolic groundbreaking ceremony launched the expan-sion of the monomer plant.

Sika AG, based in Baar, Switzerland, acquires WACKER's structural silicone sealants and adhesives business.

A new silicone-emulsion production facility goes on stream in Shanghai, China

2005 WACKER and Dymatic set up a joint venture in Shunde (China) for the manufacture and marketing of silicone products used in the textile, leather and fiber industries.
2006 WACKER enters into a joint venture with Dow Corning to manufacture silicone precursors in Asia.