Apparecchio per determinare la resistenza all’abrasione della carta.

Accartocciamento: accumulo di una pellicola nel meccanismo di una macchina fotografica o di un proiettore come risultato di una rottura o di un caricamento non corretto.

Curl
Is caused by the uneven expansion or contraction of the two sides of a sheet when it absorbs or loses water. Curling tendency is strongly influenced by sheet two-sidedness. It is also aggravated by the existence of uneven stresses and strains between the top and bottom of a sheet. There are many types of curl, most of which fall into one of two categories, either inherent curl which shows up immediately after the paper is first sheeted or converted, or moisture curl which is due to the tendency of paper to come to equilibrium in moisture content with the relative humidity of its surrounding atmosphere.

Inherent Curl
There are several known causes of inherent curl in paper. For example, the wire side and felt side of a sheet exhibit different degrees of fibre orientation, with wire side fibres tending to be more aligned in the machine direction than felt side fibres. This leads to built-in stresses in the wire side during drying since it has a greater tendency to shrink than the felt side. As soon as the paper is sheeted or converted, it curls with the grain edge bending toward the wire side and the axis of curl parallel to the machine direction. This is a most common type of inherent curl. If the two sides of the sheet receive unequal drying in the dryer section, then, upon calendering, the wetter side stretches more and a built-in curl results. Finally, paper will take on a permanent curl if it is allowed to remain wound in a roll for any considerable amount of time. This effect will be most pronounced in the inner part of the roll. This phenomenon occurs because the outer side of the sheet, which is under tension, undergoes a permanent stretching. This type of curl is often called mechanical curl.

Moisture Curl
Moisture curl occurs when paper is required to come to equilibrium with new atmospheric moisture conditions and the two sides of the paper react differently, producing a finishing, or uneven absorption of surface-size by the two sides of the sheet. Paper coated on one side only is an extreme example of paper whose sides show very different moisture absorption technologies. Coated one side paper tends to curl toward the coated side when exposed to high relative humidities because the coated side is relatively inert to water vapour and remains dimensionally stable. It the two sides of a sheet have different stresses established in them during drying, they will expand to different degrees when exposed to high relative humidities, producing a moisture curl. Uneven drying stresses arise if the two sides of the sheet dry at different rates. In general, moisture curl problems are not well understood and can be a source of much trouble to the papermaker and converter.

Accettato: Pasta epurata che esce dallo screen o dalla parte superiore del cleaner.

Accepts: Usable fibre that has passed through the screening and/or cleaning operations.

Acceptés: Pâte épurée qui sort de l’épurateur sous pression ou de la partie supérieure du cleaner.

1° Definizione
Materie prime non fibrose impiegate nel processo di fabbricazione della carta, al fine di facilitare quest’ultimo e migliorare la qualità del prodotto finale.

2° Definizione
Sostanze ausiliarie aggiunte ai pigmenti e ai leganti nelle formulazioni di patina, al fine di conferire a quest’ultima determinate caratteristiche oppure di migliorare le proprietà dello strato di patina applicato. Tutti gli additivi influenzano in maniera più o meno marcata le caratteristiche di flusso delle patine: alcuni sono utilizzati con lo scopo di provocare variazioni delle caratteristiche di scorrimento, mentre altri servono per realizzare patine più uniformi e con maggior possibilità di applicazione o per conferire proprietà specifiche ai prodotti finiti.

1^st Definition
Materials added to paper or to the papermaking furnish to modify or improve certain paper properties or to facilitate the papermaking process. This classification encompasses all materials that enter the system except fiber and water. Common additives are alum, fillers, sizing agents, dyes, wet strength resins, biocides, defoamers, retention aids, etc..

2^nd Definition
Materials added to pigments and binders in coating colour formulations, in order to modify the handling properties of the dispersion or to impart specific properties to the coating colour or to the finished coated sheet.

1° Définition
Matières premières non fibreuses utilisées dans le procédé de fabrication du papier, afin de faciliter celui-ci et d’améliorer la qualité du produit final.

2° Définition
Substances ajoutées aux pigments et aux liants dans les formulations de la sauce de couchage, afin d’apporter des propriétés spécifiques à la sauce liquide ou à la couche sèche et adapter la sauce au mode d’application utilisé.