Company history

Sekisui Chemical was not founded on a business idea. In March 1947 a group of employees of Nippon Nitrogen Fertiliser (today Chisso), which had lost its Korean plants in the defeat and could not absorb the returning staff at home, set up Sekisui Sangyo as one of several vehicles to take them in. Capital was ¥100,000. In January 1948 the new company took over Nippon Nitrogen’s Nara plant, began what was Japan’s first automatic injection moulding, and renamed itself Sekisui Chemical.

That origin fixed the shape of everything after it. Where most of Japan’s general chemical firms diversified downstream from petrochemicals, Sekisui had no raw material of its own: the only way to grow was to find another use for resin, and then another. Plastic tape, selling from late 1949, put the company on its feet. Ueno Jiro became president in September 1951 and drove expansion hard — rigid PVC pipe from the Kyoto plant in 1952, displacing metal pipe; listings in Osaka (1953) and Tokyo (1954); Ritto for pipe and building materials and Mizuguchi for polyvinyl butyral interlayer film in 1960; and in 1964 Tokuyama Sekisui, which finally gave it PVC resin of its own and a chain running from monomer to moulded part.

Repeated rights issues lifted capital to ¥8.55 billion, sales multiplied fifty-eight times in fifteen years, and by 1964 the press bracketed the company with the era’s other prodigies as “Sony, Honda, Sekisui.” The trouble was that nothing it made was hard to copy.

Rivals poured into PVC pipe and corrugated sheet, overproduction crushed prices, and the North American venture Ueno had launched in 1963 — foam polystyrene sheet, sold as “the third paper” — ran into Dow and Monsanto, whose research budgets were of another order. Left holding inventory, Sekisui posted a loss in 1965 and fell out of the ranks of growth companies; Ueno moved up to a chairmanship without representative authority. In March 1967 Obata Kenzo arrived from Asahi Kasei — like Sekisui, a descendant of the old Nippon Nitrogen group — to rebuild it, selling off loss-making lines and, in July, halving the capital outright. Within two years the debt was written down and the dividend restored.

Out of that retrenchment came the decision that defined the company. In February 1971 Sekisui launched Sekisui Heim, a steel-framed unit house: the body of the home built as boxes on a production line and craned into place on site. It was the resin-conversion business reasoned outward — a firm that had spent twenty years standing up mass-production plants for one product family after another now applied the same logic to the largest consumer product there is. Crucially, it had no one who could draw an architectural plan, and that ignorance is what allowed it to treat a house as a factory good rather than a building site.

Production capacity followed immediately, with Nasseki Kogyo in October 1971 and Sun-S Heim in March 1972 (both now Sekisui Heim Industry). Housing sold through channels that had nothing in common with pipe or mouldings, and it would in time become the group’s largest source of profit.

From 1977 the task was to make each business stand on its own. A divisional structure introduced in May of that year separated housing, plastic mouldings and environmental products (pipe and building materials) into self-managing units. Housing widened its range with the timber-framed Two-You Home in March 1982 and a new Gunma plant that April, and in December 1983 Sekisui America Corporation began the move abroad from a base first consolidated at home.

The research estate expanded in step, and along the same fault line: the Applied Electronics Laboratory (1987), the Housing Research Institute (1990) and the Kyoto Technology Centre (1992) gave the two halves of the company — houses and functional materials — laboratories of their own. Growth by acquisition was, at this stage, modest and domestic: Komatsu Kasei in 1997 for pipe, Hinomaru in 2000 for the Kyushu sales network.

In March 2000 seven divisions were folded into three — Housing, Urban Infrastructure & Environmental Products, High Performance Plastics — with a separate new-business unit alongside. It was the frame the company still runs on.

In March 2001 the three divisions became three companies — Housing, Urban Infrastructure & Environmental Products, High Performance Plastics — under an internal company system that has not been reorganised since. The design is legible: housing earns the money, infrastructure captures domestic renewal demand, and high performance plastics opens the growth fields of electronics, mobility and medicine. What is equally legible is the method. Sekisui does not restructure the frame; it adds outside it, and it adds by buying.

Korea’s Youngbo Chemical came in 2003; Daiichi Pure Chemicals in 2006 became Sekisui Medical and gave High Performance Plastics a life-science leg; in 2009 the polyvinyl alcohol resin business bought from Celanese secured the feedstock for interlayer film, an upstream move a converter would once have been unable to make. Then a decade of steady acquisition: the diagnostics business of Genzyme in 2011, Mitsubishi Plastics’ pipe operations in 2012, a Thai unit-housing plant in 2013, Eidia from Eisai in 2015, Polymatech Japan in 2017 for automotive materials, Soflan Wiz the same year for fire-resistant products, and Singapore’s Veredus Laboratories in 2018.

By the end of the period, medicine and mobility existed as real businesses — but they had all entered from outside, appended to a structure that itself never changed.

2019 brought a change of register. An April reorganisation of head office created an ESG Management Department, putting non-financial targets such as greenhouse-gas reduction inside the management system; in November the company bought AIM Aerospace of the United States, now Sekisui Aerospace, to scale up mobility materials. In June, Kato Keita, a strategist from the high-performance-plastics side, became president — and met the collapse of housing demand under COVID in his first full year. Alongside the move to the Tokyo Prime market in April 2022 he set out Vision 2030, committing the company to raising the share of revenue from businesses aimed at social problems: medicine, mobility, perovskite solar.

In January 2025 Sekisui established Sekisui Solar Film to design, make and sell perovskite cells — light, flexible, film-type panels that can go on building façades and roofs too weak for silicon. The technology is the company’s own history turned into a power device: decades of film-lamination know-how from laminated-glass interlayer, applied to generation. It also fits none of the three companies. It is a fourth field.

Revenue of about $8.2B (¥1.23tn) and roughly ¥100 billion of operating profit in the year to March 2025 mark what the three-company frame has accumulated. But Japan’s shrinking population points the housing market down over the long run, and the largest earner has the least room left to grow. Whether the acquired medical and mobility businesses, or the perovskite venture launched in 2025, mature into a replacement pillar in time — and how to reform the housing business while paying for a fourth field — is the problem Kato’s management has taken on.