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As part of an overall upgrade to maxi-mize the strength and quality of its recycled paperboard, Simkins Industries, New Haven, Conn., has spent more than $3 million to install four new formers on its No. 2 paperboard machine. In addition to the new equipment, company managers also implemented several chemical options in order to achieve the highest quality standards for its customers.
Simkins provides about 50% of the output from the New Haven mill to its own folding carton division. The balance is sold to paperboard converters who distribute it through a nationwide network of merchants with a major percentage being shipped to the Midwest. Since demand for paperboard has been flat, Simkins has had to compete based on quality. High-quality raw materials, additives enhancing performance, and new forming equipment have helped the company attract new customers.
Improvements at the New Haven mill have resulted in a better-quality paperboard that consistently scores well in laboratory tests. The improvements have also provided the strength and printability properties required by customers.
QUALITY RAW MATERIALS. Simkins Industries gets the highest performance from its recycled paperboard at the lowest cost by using eight plies. The raw material used for some of the outer plies differs from the inner plies to provide better surface properties.
The company relies on 100% recycled paper: 65% to 68% post-consumer and 32% to 35% pre-consumer. According to New Haven production manager Jim Pedersen, Simkins buys top-grade recycled paper that is free of laser-printed inks and other contaminants.
Printability is very important to Simkins, since its paperboard is used for consumer packaging such as tissue and food boxes, envelopes, medications, ornaments, apparel, and many other items that are contained in packaging designed for consumer appeal. The top layer of the paperboard, which is made from pre-consumer paper, incorporates a precoat of additives, including a cationic hybrid cornstarch. Produced by National Starch and Chemical, the Cato-Size hybrid cornstarch builds formation for subsequent surface coating holdout and helps to ensure the proper receptivity for inks. This precoat improves surface strength and sheet closure. It also runs cleanly, because it contains no amylose, which typically accumulates into a sludge and causes scaling and flaking.
About 80% of the paperboard produced at the mill is cut into sheets ranging in area from 20 in.-by-35 in. to 50 in.-by-70 in.; the remainder is fed onto rolls. The caliper of the paperboard made at the New Haven mill ranges from 18 points to 40 points. Customers can order their paperboard with either a white- or kraft-colored back.
NEW FORMING TECHNOLOGY. The papermaking pro-cess at Simkins’ New Haven mill includes pulping, screening, consistency regulations, refining, stock flow, combining, pressing, drying, calendering, starch application, and cutting. The mill operates 24 hrs/day for approximately 300 days per year and has the capacity to process 70,000 tpy of recycled paperboard.
The dry-strength additive dilution unit easily fits into the mill’s limited space (pictured: Craig Shultz, machine tender for the No. 2 paperboard machine (right) and John Keaveney, chemical sales representative).
Simkins’ No. 2 paperboard machine was originally installed in 1914. It is 126 in. wide and has a trim width of 117 in. To improve the appearance of the 100% recycled coated paperboard produced on the eight-cylinder machine, Simkins decided to install four formers in 1997 to better control fiber orientation for a stronger, better looking product.
Supplied by J.H. Horne & Sons, the new pressure formers feature hydraulic headboxes with curved lids for controlling rush-drag ratio and improving fiber orientation. The new formers were placed at the beginning and end of sheet formation to improve the appearance of the top and bottom surfaces. Two of the formers were positioned to create plies one and two, while the other two were used to form plies seven and eight. The four intermediate plies were formed using the cylinders as before. Also, each layer was couched in between to bond the plies.
The new formers are equipped with Z-block explosion chambers that provide a more favorable fiber orientation, enabling the company to produce paperboard that has a fiber orientation ratio of 2:1 (machine direction to cross direction). In addition, Simkins was able to speed up the machine by 30 fpm and the sheet profile was improved significantly.
DRY STRENGTH ADDITIVE PERFORMS. As part of the overall upgrade to maximize the strength of paperboard made from recycled paper, company managers considered several chemical options to use with the forming improvements. These options also helped with bonding issues associated with the increased speeds on the No. 2 paperboard machine.
Simkins Industries’ eight-ply paperboard is made from top-quality recycled paper.
Before adopting a new dry-strength additive, managers considered using a wheat starch. However, the capital investment for this option would require spending approximately $60,000 for a dry starch make-down and feed system. Installing such a system would have been difficult as well as costly, since there was very little room for additional equipment at the mill.
Also, the associated labor costs for making down the wheat starch would have amounted to $5,200 annually. Though a dry-strength additive was more expensive than wheat starch on a per-pound basis, it could provide the required performance for scoring, strength, and ply bonding. In addition, the capital and added labor costs were relatively minimal, making it more cost effective.
The mill ultimately chose a dry-strength additive from National Starch and Chemical known as Redibond. The additive’s dilution unit was easy to install and fit into a small area. This area was adjacent to the wet end and the 330-gal totes that contained the dry-strength additive at 30% solids. Hoses were used to carry the additive to a 126-in.-long spray boom located between a cylinder and former for plies six and seven on the No. 2 paperboard machine.
Additive benefits. The dry strength additive spray system is set up so that pressure from the pump in the dilution unit creates a mist of polymer droplets that are aimed into the nip at the bottom of the number six ply and the top of the number seven ply. Using the dry strength additive in this manner raised the strength between these plies from about 60 to 90 mullen ply bond to 113 to 120 mullen ply bond. These figures were obtained in Simkins’ quality control laboratories where stiffness, Bender, and moisture content also were tested and showed improvement.
The dry-strength additive is sprayed into the nip at the bottom of the number six ply and the top of the number seven ply.
For Simkins’ customers, it is crucial to have a high-quality, consistent paperboard that allows printing at higher speeds, according to Pedersen. To test printability with various inks, Simkins used a laboratory-sized printer. Pedersen says that customers have been pleased with the paperboard’s printing properties since the forming and additive improvements.
In addition to printing at high speeds, Simkins’ customers need to fill containers with materials at speeds of up to 280 per minute for an average size container. This requirement necessitates that the paperboard provide strength and consistent bending performance. Pedersen says that there have been no customer complaints about insufficient strength since Simkins began using the dry-strength additive early in 1998.
Secondary benefits of the new dry-strength additive included improved machine performance relating to gains in speed, drainage, retention, and drying. The No. 2 paperboard machine now produces 150 tpd of recycled paperboard. Also, because of the dry-strength additive, employees at the New Haven mill do not have to deal with plugged nozzles, which could have been a problem if wheat starch had been used. This benefit minimizes labor requirements.
Frank P. Camera is general manager for Simkins Industries, New Haven, Conn.
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