History of the Ziplock Bag

As with all great inventions and innovations - from sliced bread to smartphones - once they are widely adopted it becomes difficult to even remember a world in which they didn’t exist. Ziplock bags are the perfect example of this phenomenon. Although they’ve only been around for slightly more than half a century, you’ll find them everywhere now - and indeed, they have over a thousand and one practical uses. These ubiquitous reclosable bags, which are used for packaging, storage, shipping, and organization, now come in a wide variety of styles and sizes. But where did they come from and how did they evolve into the range of products we know and use today? 

History of Reclosable Ziplock Bags

In 1951, an inventor named Borge Madsen applied for a patent for a plastic slide fastener, which was the precursor of today’s familiar zip lock bag. His original design was slightly more complex than the current version (it had two “engaging areas” instead of the one commonly used today) and it looked more like a traditional zipper with a tab, except that it had no teeth and was made of plastic. The same year, a company called Flexigrip was founded with the intention of developing and marketing a product based on Madsen’s invention, whose patents it had purchased. Among the first applications was its use in loose-leaf binders and flat briefcases. The expense of manufacturing the “tab” style plastic zippers prohibited them from becoming widely used by consumers initially, but then Steven Ausnit - one of the founders of the family-owned Flexigrip company - came up with the idea of a “press-and-seal” type zipper. This is the type of zip lock bag fastener most commonly used today.

Until this point, Flexigrip had been using a heat seal process to attach string zipper profiles to the film before converting it into bags. The industry calls these “post-applied zipper bags” as the zipper is not integrated into the original bag film. A major leap in the evolution of the zip lock bag came in 1959, when Ausnit found out about a Japanese company - Seisan Nihon Sha - which had developed a new manufacturing process that allowed the zipper profiles to be extruded into the polyethylene film from which the bags are made - an innovation which cut the manufacturing expense in half. Within the industry, these are called “integrated zipper bags” or “integral zipper bags”. In 1961 the Flexigrip company obtained the licensing rights to the new “integral zipper” process and founded another company called Minigrip, which was created to market the now inexpensively-produced zip lock bags. Minigrip primarily focused on industrial bags with a color line trademark - a thin “Red Line” above the zipper. Around 1964, Minigrip secured an exclusive licensing agreement with the Dow Chemical Company to market ziplock bags through grocery stores and supermarkets. The now familiar Ziploc® consumer brand was launched and widely marketed in 1968. It took a few years for the product to really catch on, but by the early 1970s, the Ziploc® brand bag had become immensely popular and was being used by consumers for everything from storing sandwiches for school lunches to transporting goldfish home from the pet store. Dow Chemical eventually sold the rights of their Dow Brands, including Ziploc®, to S.C. Johnson Company in 1997.

Over the years, other consumer brands started to enter the market under the names of Hefty, Glad-Lock, and various other private-label store brands. However, the Ziploc® brand remains the largest and most well-known of all consumer brand zip lock bags. In 1978, Minigrip was acquired by Signode, Inc. Then in 1987, Signode was acquired by ITW, and Minigrip became a subsidiary of ITW. Until 2006, ITW Minigrip manufactured all their industrial RED LINE™ bags at a manufacturing plant in Seguin, Texas. As the original Minigrip “integral zipper” patents expired in the mid-1980s, many companies began to import similar-style bags from China and other parts of Asia, due to cheaper manufacturing and resin costs. ITW Minigrip started losing market share and the industrial zip lock bag market became very fractionalized, with many importers having entered the game. In order to compete with the flood of imported bags, ITW Minigrip bought a plant in Thailand and moved production of all their industrial zip lock bags there in 2006. Between 2008 and 2011, ITW Minigrip began acquiring some of the larger importers in an effort to consolidate the industrial bag market. In 2012 Minigrip was acquired by Inteplast Group, a large importer and domestic producer of all types of industrial, retail, and medical plastic bags. Minigrip is now a subsidiary of the Inteplast Group.

ClearZip® Wholesale Zip Locking Bags for Industrial Use
International Plastics, a manufacturer and distributor of plastic bags founded in 1964, was one of the largest distributors of Minigrip industrial zip lock bags in the USA. As ITW Minigrip continued to struggle in the 1990s against the tide of import bags, International Plastics developed and began importing their own industrial brand of zip lock bags called ClearZip. Capitalizing on the fractionalized import zip lock bag market, ClearZip became a dominant brand in the industrial markets. ClearZip reclosable zip lock bags are made of high-quality 100% virgin low-density polyethylene (LDPE). These bags meet or exceed FDA/USDA, GMP, AIB, and TSA requirements and are Kosher-approved for food contact. ClearZip bags are less expensive and are available in many more sizes, thicknesses, and styles than the consumer retail zip lock brands marketed by Hefty, Ziploc, Glad, etc. In fact, they are available in five different thicknesses and more than 300 sizes and styles, versus the limited range of zip lock bags marketed in grocery stores. International Plastics also offers custom printing, sizes, and configurations of ClearZip bags to meet specifications for almost any application imaginable. In 1992, International Plastics entered the medical market with the launch of Specimen Shield® Laboratory Transport Specimen Bags. These patented bags have a three-wall construction with a flip top on the back to keep the accompanying paperwork secure and separated from the specimen contents. 

Further Development and Evolution

Today, there are two basic closure types found in both consumer brands and wholesale industrial brands: the “tab” or “slider lock” zip bags, which closely resemble Madsen’s original invention; and the “press-and-seal” style bags, which are the most commonly used. The more expensive “tab” or “slider lock” zip bags are useful in situations where the user must wear gloves or where the user’s hands may become slippery with oil or grease. These are also typically used for cigars and loose tobacco, as well as food storage, such as deli bags. Along with closure styles, there have also been many developments regarding film structure, including modifications for enhanced retail presentation and longer shelf life for food storage.

Most cheese packages found in grocery stores use a laminated film structure with post-applied zippers, with tamper-evident security features above the zipper. Laminated zip bags are widely used in retail food markets. More and more food products - and even products such as laundry detergent - are being packaged in what the industry calls “stand-up pouches”. Most of these include a tamper-evident tear strip along with the familiar zip lock. The advantages to these style zip lock bags are twofold, convenience for the customers and cost savings over conventional retail packaging. There are now hundreds of patents for individual zip lock bag styles and there are a virtually unlimited amount of applications and uses for the bags. Larger markets using reclosable zip lock bags include industrial, medical, crafts, jewelry, toys, hobbies, hardware, tobacco, retail, food packaging, food storage, electrical, and others. Every industry has a use for zip-locking bags.