Raw materials. All vinyl products are made from a unique combination of vinyl resin and various additives that give these products their particular properties. For more information on the vinyl resin process, see general vinyl section. Every formulation is different, and most are proprietary. Some of the additives commonly used in vinyl wallcovering include:
- Plasticizers, which give the finished product such properties as flexibility at low temperatures, fire retardance, resistance to staining and abrasion and long-term aging. Since plasticizers tend to counteract each other, it's impossible to formulate a vinyl product with the ultimate in all properties. The balance is shifted within product lines to produce wallcoverings that emphasize certain characteristics.
- Stabilizers, which prevent the vinyl compound from degrading during high temperature processing and help protect the finished product from discoloring during its useful service life.
- Other additives, such as pigments, mildewcides, fungicides, flame retardants or smoke suppressors. Low levels of biocides are used in the vinyl compounds to inhibit the growth of various microorganisms on the product itself.
Processing/fabricating. Once the additives have been combined with the resin, the resulting material is called a vinyl compound and can be in pellet or powder form. The nature of the vinyl compound allows versatility in the production process, enabling manufacturers to meet a host of performance requirements. The next stage of vinyl wallcovering manufacturing generally consists of the following steps, which take place at relatively high speeds under carefully controlled conditions.
Resins, plasticizers, stabilizers, pigments, biocides, fire retardants and other ingredients are carefully weighed and blended. This batch of ingredients is mixed in a Banbury-mixer to create a uniform melt of the ingredients. Multiple Banbury batches are then blended and milled for uniform feed of the compound melt to the calender train. Prior to actual calendering, the batches are put through a strainer-tuber that removes any impurities from the finished product. The product then moves onto the calender, where large, temperature-controlled rolls form the compound into a thin film. Either prior to or after laminating, the vinyl sheet can be decorated using any of the previously described printing techniques.
If the final product is to be a plain, solid color material requiring no surface printing, ink-wiping or other finishing techniques, the material is "in-line-embossed" at this point, then packaged.
To create the illusion of dimension, the embossed, fabric-laminated sheet is passed through a series of inked rollers to add a color to contrast with the base film color in a process called "Spanishing" or "shadow printing." The process leaves most of the ink in the valleys of the embossed surface and removes most of it from the raised portions, creating a three-dimensional textured effect. In the printing process, a distinct pattern design is created by the use of inks applied by one or more etched print rollers. Finally, a top coat can be applied to the vinyl surface by etched rollers to add the desired sheen to certain patterns. Print inks may impart a gloss, a semigloss or a matte finish to the product. One of the decorative advantages of vinyl wallcovering is its ability to hold texture when it is embossed, whereas embossing is not permanent on a paper surface.
Once produced, the commercial product is inspected yard by yard and cut into 30- or 50-yard roll lengths, packaged and prepared for stock or shipment. Residential goods are slit to 20-1/2" to 28" widths and inspected yard by yard, packaged and prepared for stock or shipment.