Having successfully industrialized the red synthetic dye alizarin, it was inevitable that Mitsui Coal Mine would move on to research and development of indigo.
Synthesizing indigo, however, required a considerable amount of research. The fact that research got underway in 1913, at the height of World War I, also meant that it was impossible to draw on German technology. Relying instead on existing documents, Mitsui was the only company to continue with research. Research was also spurred along by rivalry with the Sumitomo Group, which was conducting government-subsidized research into synthetic dyes.
In the face of criticism from management of the Mitsui Coal Mine, who were concerned about “squandering profits from coal”, Mitsui executive Takuma Dan remained focused and determined. “I believe that dyes represent the next generation. While we have achieved much, it will take time until we start to make a profit.” Dan quashed any opposition and proceeded to perfect indigo. Production got underway in 1932.

The denim boom took hold in 1976, sending demand for indigo soaring. Having expanded production facilities to keep pace with current trends, the company increased annual production to 800 tons, and again to a maximum of 1,100 tons in 1981. The introduction of new equipment such as alkali condensers and spray dryers enabled production to be increased even further, all the way up to 1,450 tons.
Unfortunately, Mitsui’s manufacturing methods couldn’t compete with those in Germany, in terms of raw material, production efficiency, or cost. Companies producing indigo at far lower prices started to appear in China too, resulting in a gradual loss of competitiveness. Production was suspended in 1997 and plants closed down in 1998. 65 years of indigo production came to an end.

After the war, a national policy was set out to increase production of chemical fertilizer, in an effort to tackle food shortages. To achieve that goal, it would be necessary to increase production of ammonium sulfate. As there was a shortage of the raw material sulfuric acid however, the only viable alternative was the mass production of urea, a synthetic fertilizer made from ammonia and carbon dioxide.
Toyo Koatsu Industries responded by building the world’s first mass production urea plant in Hokkaido in 1948 (now Hokkaido Mitsui Chemicals). The company was already producing urea in Omuta and Hikoshima, but costs were starting to hamper production. Realizing that building a facility capable of producing large volumes would enable it to produce urea for more or less the same cost as ammonium sulfate, the company set about constructing a plant in Hokkaido. It also improved manufacturing processes in Omuta and in 1950 installed urea manufacturing facilities. It took a lot of hard work, even at the Hikoshima Plant, which had escaped damaged by the war, but installing and expanding new facilities played a key role in the recovery process.
That was how Toyo Koatsu Industries managed to grow into a major chemical fertilizer manufacturer in just a short space of time.

As Japan’s rapid economic growth continued, facilities continued to expand in scale during the latter half of the 1960s. In 1969, the company completed a plant capable of producing 1,000 tons of ammonia and 1,750 tons of urea at its Osaka Works (now Mitsui Chemicals’ Osaka Works).
In 1961, the engineering wing of Toyo Koatsu Industries broke away to become Toyo Engineering, in order to accelerate exports of urea technology to the world.
Through Toyo Engineering, a total of 147 plants in 30 different countries currently use licensed urea technologies based on Mitsui Chemicals technologies (as of March 2010). We intend to keep on rolling out our technologies to other countries in the future.

Demand for petrochemical products in Japan continued to grow. The new Cabinet established by Prime Minister Hayato Ikeda in July 1959 set out an “income doubling plan” in December that same year, spurring on rapid economic growth. The government supported development of large-scale petrochemical facilities with the aim of becoming “globally competitive”.
MPI meanwhile launched its Phase II Plan to expand the scale of its Iwakuni Works (now the Iwakuni-Ohtake Works). As there was limited land available on the company’s Iwakuni site, it decided to establish ethylene and new project plants at an adjacent Ohtake site by the Oze River. Construction began in 1961 and continued through to 1963. By the time the works was finished, it had a total area of approximately 924,000m².
As demand continued to soar, MPI launched a Phase III Plan, aimed at streamlining the works. The petrochemical industry was transforming from domestic production to a new era of large-scale facilities.

Technology to manufacture polyethylene was licensed from Mitsui Chemical Industry to MPI in 1956. The company launched HI-ZEX in 1958. Operations were structured so that HI-ZEX manufactured by MPI was sold by Mitsui Chemical Industry. As Mitsui Chemical Industry was conducting ongoing market research and compiling comprehensive production and sales plans, prior to the start of polyethylene production, it made sense to divide up production and sales within the group. Sales were sluggish initially at around 150 to 200 tons per month. The hula-hoop boom of 1958 drove sales to 1,259 tons by November that year. Individual companies within the Mitsui Group worked to expand operations of not only HI-ZEX but other products as well.

While the Mitsui Group continued with plans for the Chiba Works in eastern Japan, Toyo Koatsu was looking at petrochemical production in western Japan, in the coastal industrial area of Sakai overlooking Osaka Bay. Plans became concrete in 1963 when the company finalized what it referred to as its “Pre-Sakai Plan”, aimed at securing a share of the petrochemical market in western Japan. This led to the establishment of the Osaka Works in 1964.
At the time, numerous companies were looking at production possibilities in western Japan. As well as working on its Pre-Sakai Plan, Toyo Koatsu also teamed up with Mitsui Chemical Industry and General Sekiyu and submitted plans to the government for commercial production of derivatives, primarily via ethylene production facilities with an annual production of 100,000 tons. A petrochemical plan for western Japan had also been drawn up by other companies based in the area, plunging the situation into chaos. The government stepped in however and instructed the two sides to combine their plans into one, in order to rationalize and increase the scale of operations. After reaching an agreement, Osaka Petrochemicals was established in 1965, with investment from Toyo Koatsu, Mitsui Chemical Industry, and Kansai Petrochemical.

Eagerness to invest in Japan’s petrochemical industry showed no signs of slowing, even during the recession from 1964 to 1965. With no room to build more plants at its Iwakuni-Ohtake Works, MPI made plans to construct in Chiba. Just a stone’s throw from Tokyo, Japan’s biggest consumer market, Chiba was a prime location in terms of marketing.
As part of plans to develop the Keiyo Industrial Zone, between Chiba and Tokyo, construction got underway in the Goi, Anegasaki, and Sodegaura areas of Chiba prefecture. MPI played its part too. Following land reclamation, civil engineering, and plant construction work, the new Chiba Works (now the Ichihara Works) was completed in 1967.
With a systematic, functional layout, the Chiba Works helped streamline the flow of raw materials and products, and even factored in the need to expand in the future. It was based largely on experience and expertise from the Iwakuni-Ohtake Works, and had an ethylene plant with an annual production of 120,000 tons, the highest in Japan at the time. The fact that it was built as a polyolefin mass production facility right from the start was one of the Chiba Works’ biggest advantages. A great deal of thought went into preventing pollution too, with drainage checked and separated into oily and non-oily fluids via a general purpose oil separator.