The quality of the cardboard core deeply of the finished products and the performance of the converting line. But what are the factors to consider when speaking about cores? ICP tells us.
Tiziano Pieretti
During the course of these last few Years, companies operating in the tissue field have registered incredible growth. Consequently, raw materials suppliers involved in the production of a finished roll have had to modify and improve machinery and product characteristics in order to be able to answer to precise market demands. This is true also of the board used to make the cores for industrial tissue rolls support. Up until only a few years ago, cores were manufactured using three lilies of paper, each of which weighing around 300 grams per square meter. The speeds of the machines used in toilet tissue converting were lower and their sizes surely not comparable to the modern XXLs. Today, almost all converters try to reduce costs to a minimum and for this reason they have concentrated towards the manufacture of cores using a lesser quantity of paper, without slowing down the production process. The present trend is to use only two board plies, each of which weighs around 200 grams per square meter. With time, the "Cinderella" board has become more and more protagonist of the tissue scene, as converters have understood that the quality of the finished toilet roll, as well as its aspect, depend also on the core. Also, low-quality board compels the expensive converting machines to forced stoppages. Many resources have been dedicated to the resolution of trim recycling problems as many converters produce tissue with their own PMs. In this case, according to the type of raw material used for the production of the board, the trims can be reused, even if contaminated by cores for industrial rolls support. As we can intuit from what has been said thus far, there are several production variables in board manufacturing and it is important to note that there is no official technical catalogue able to classify the products available on the market and thus allow a comparison.
TO THIS END, INDUSTRIA CARTARIA PIERETTI, FOR YEARS LEADER IN THE PRODUCTION OF MULTIPLEX BOARD DESTINED FOR THE PRODUCTION OF CORES FOR INDUSTRIAL ROLLS SUPPORT, has developed an internal method to fill this void and answer to the production demands of its customers. When ICP approaches a potential new customer, its internal laboratory analyzes the product supplied by the competition. Subsequently, a comparison with our standard products in relation to ICP specifications is made, trying to detect the critical points of the supply such as product absorbency or mechanical specifications.
Standard ICP specifications have been established on the basis of the numerous visits carried out at our customers' plants.
Every important variation recorded in the creation of the core produced with ICP board has been put in relation with a technical analysis of the product and subsequently inserted in a database which has allowed us to optimize the technical specifications. All this makes ICP products extremely constant in time since all production follows pre-established specifications.
PAPER PRODUCTS CAN BE DIVIDED INTO MANY CATEGORIES AND BOARD IS ONE OF THESE.
Many are the definitions for this word and the most widely used is the one according to which board is part of those papers that have a weight interval that goes from 150 to 1000 grams per square meter and beyond. This generic classification does not, however, take into account the raw material used, the type of application produced, the technical specifications, etc. In our case, we will try to define this "micro-product", that is, board for the manufacture of spiral cores for toilet rolls and kitchen towel rolls support. Let' s start with a simple explanation of the production of paper taken from the manual "Discovering the planet paper" compiled by Assocarta (the Italian Papermakers' Association):
"paper or board is obtained through a suspension of fibrous material in a concentration of around 1%. This mixture is spread out on a closed-ring wire and the water, eliminated through drainage, pressing and final drying, leaves the fibers irregularly disposed and reciprocally bonded."
In the above-mentioned definition, the type of raw material used is not mentioned. In our specific case, most converters utilize board comprised of 100% waste papers. Since we are talking about material coming from a fibrous mix that is therefore variable in content, its selection is extremely important for the constancy required by the product. It is for this reason that ICP pays particular attention to the choice of highly selective products that have a fundamental role in making a quality board. From waste paper depends its color, stiffness, absorbency and porosity. And from these characteristics depend also the cost of the board: based on he waste paper used, there will be variations due to the different cost of the raw material and to the different impact of converting costs based on lesser or greater productivity.
Since no official classification exists, ICP has defined internal standards and has named its products as follows:
MONO 500
MONO 600
MONO 700
MONO 900
DUPLEX100
DUPLEX 200
These denominations are not merely borne out of the type of stock, but have also another meaning connected to the mechanical specifications of the product itself. The "Mono" portion of the name indicates that the board is comprised of a sole mix of raw materials, while the "Duplex" types are comprised of two different types of raw material mixes. The number portion, instead, defines the degree of stiffness of the product. When speaking about cores for tissue rolls and kitchen towels support, usually the products recommended by ICP are the following:
TYPE ASPECT
MONO 500 Sole mix, Havana-brown color
MONO 600 Sole mix, Havana-brown color
MONO 900 Sole mix, white color
DUPLEX 100 Outside white color. Inside gray color
DUPLEX 200 Outside white color. Inside gray color
Besides the type of product, substance is the second parameter through which board is commercialized. From this depends the weight of each core and, consequently, the cost which is often not remunerated by the final purchaser if the roll is sold based on its sheet count. It is also true that from the weight also depend the stiffness of the core and therefore its sturdiness and strength during all the converting phases. Obviously, every production cycle presents some critical points that determine the minimum weight of the finished core, but we can safely state that most of our customers, whose objective is the creation of light-weight, two-ply cores, produce cores having an Overall weight lower than 400 grams per square meter (two plies lower than 200 grams/sq. mt). Another important value is given by the height of the reel used, for which there are differences based on country. We are, of course, always speaking about the manufacture of a two-ply, light weight core, since this is the one that presents greater difficulties (Figure 1). In this case, there are two different production techniques:
CORE COMPRISED OF TWO PLIES OF BOARD HAVING DIFFERENT WEIGHTS, WITH EXTERNAL OVERLAP. This method is recommended in the case where rewinders without core support expandable shafts are used. Of the two methods, it is certainly the more simple one and the one that allows greater production speeds. This technique is based on the use of two plies having different heights. We cannot speak of standard sizes because every country uses its own standards. The heights used go from 65 millimeters to 90-95 millimeters.
Of course, since we do not have to make a technical consideration, the use of sizes that are so different one from the other, causes substantial variations in core production. For example, let's take else of two corewinders set in the same way but fed with different plies of paper: one with 63-mm plies and the other with 90-mm plies.
Even if the speeds of the two corewinders were identical, we would have two different unwind speeds of the board ply (the 90-mm ply would go slower than the 63-mm one) and the two cores would have a completely different longitudinal fiber vs. transversal fiber ratio (anisotropy), due to the different working angle.
Based on our experience, we recommend to use heights with an interval of 8-10 millimeters. On the italian market, for example, we use internally a height of 72 millimeters and externally a height of 80 millimeters. The result is a very stiff and well-formed core (Figure 2).
CORE COMPRISED OF TWO PLIES OF BOARD HAVING THE SAME HEIGHT, WITHOUT OVERLAP. This method is recommended in the case of rewinders that use expandable shafts as core supports because the structure can withstand a lesser weight. In proximity of the arrows indicated in figure 3, contrary to what happens in the previous case, the pressure exerted from the outside can be contrasted only by the internal ply of the board. In our opinion, this solution offers on the one hand, the advantage that only one type of product in one height and weight needs to be warehoused, but we feel that this causes many more machine stoppages during the converting process and a grater number of trims.
ANOTHER TECHNIQUE USED BY MANY CONVERTERS IS TO USE THREE PLIES OF THE SAME HEIGHT AND TO INTERNALLY AND EXTERNALLY OVERLAP THE BOARD PLIES. This is certainly a much less recommended solution since the presence of air gaps inside and outside the core makes gluing imperfect and core stiffness often insufficient. The consequent solution is to use very high weights that compensate for the construction flaws but increase overhead costs. In figure 4, we can notice this type of problem.
THE OTHER IMPORTANT ELEMENT IN THE MANUFACTURE OF A CORE IS THE GLUE USED. Today, there are many specialized companies that supply valid and dependable products. ICP collaborates with many companies supplying glues based on vinyl (PVA), dextrin, corn starch, potato starch, casein, etc. The chemistry used to make these products allows to fine tune any type of board through small modifications. It is not however, our intention to face the theme of glues since it is not something of our province. These are just some of the crucial points inherent to the problems connected with the life of the cardboard core. The core is born first from the manufacture of the roll and, through a complicated process, must accompany the positive outcome of the product. ICP, having for years considered the production of cardboard cores for tissue as a strategic field, dedicates all its resources to trying to analyze the stresses that arise during the converting process. The result is that ICP products offer maximum guarantees and productivity to its customers.
INDUSTRIA CARTARIA PIERETTI.
Industria Cartaria Pieretti is headquartered in the town of Marlia, in the province of Lucca (Italy), where it has been producing paper for over 75 years. The company was founded in 1924 by Giuseppe Pieretti, and still today the Pieretti family holds the entire share package. In this optic, the two sons, Graziano and Luisiano continued the development started by its founder, and today this tradition continues with the new generation represented by Tiziano and Carmen Pieretti.
Production is carried out on two paper machines, one of which has been recently installed. Daily board production capacity on the two machines is about 300 tons with a turnover close to 30 million Euros. Today, ICP constitutes an important presence on the market. According to unofficial estimates, ICP supplies 70% of the board used for the manufacture of cores for toilet tissue rolls support in Italy. Furthermore, 30% of total production is regularly exported to many countries worldwide. These results have been attained also thanks to the collaboration with Fabio Perini SpA that has for many years been utilizing ICP boards to guarantee its customers constantly increasing productivity. Besides supplying materials to the Perini R&D departments to study innovative solutions (for example in the manufacture of cores for the XXL line), ICP board assists and is a guarantee of reliability in the checkouts that Perini carries out in the presence of its customers. The natural consequence is the continuous supply of ICP board which is often a competitive product. ICP's market has no limits: thanks to its high specific weight and its easy manageability, it is delivered worldwide at a highly competitive cost. Market evolution and the development of production technologies lead producers to demand dependable, high quality products. It is for this reason that, sometimes, in the country of origin, it becomes impossible for a firm to find special products such as those supplied by ICP, making it thus necessary to seek supply from companies such as ours that allow to enhance productivity and accompany the firm in its present and future development.