Kraft pulp sizing

Figure 7.23. Influence of storage time and storage temperature on the hydrophobicity of bleached kraft pulp sized with 0.04 wt% AKD. The hydrophobicity is given in terms of advancing water contact angle recorded when the drop base expansion was first observed to stabilize. (From ref. (24) with permission)...

Pulp type is also important and, in general, unbleached pulps are easier to size than bleached pulps. Pulps with a high cellulose content are extremely difficult to size and require as much as 10 times the amount of reacted AKD to produce similar levels of sizing to those of Kraft pulps. This effect is not easily understood and cannot be explained in terms of surface area. The presence of fillers also increases the amount of size required, and sizing efficiency has... 

Fig. 8.1.3. High-performance size-exclusion chromatograms of acetylated samples of milled wood lignin from pine (—), pine kraft lignin (—) and two samples of residual lignin isolated from pine kraft pulp (-,----). (Yamasaki et al. 1981)...

The hemicellulose adhesives were evaluated on 50- by 100-mm2 A-flute corrugated board samples. Commercial single-faced board (125 to 160 g/m2) bonded with a maize starch adhesive and liner (160 g/m2) was obtained. The liner and fluting material were prepared from virgin kraft pulp and were not surface-sized with starch. The single-faced material was cut into samples (50 x 100 m2) with the flutes in the 50-mm direction. Liner samples were cut in 60- by 110-m2 samples. 

Materials. All test papers were obtained from a single roll or were made from pulp. The following test papers were used (1) Foldur kraft paper, a bleached kraft paper made from 90% southern pine and 10% hardwood pulps, with 0.5% rosin size and 3% titanium filler (2) newsprint paper made from 80% groundwood and 20% unbleached sulfite pulp and (3) handsheets prepared from a 1 1 furnish of Weyerhaeuser New Bern softwood (NBS) and New Bern hardwood (NBH) bleached kraft pulps. 

Before the pulp can be made into paper, it is necessary to mechanically beat or refine it. It is also usually bleached with chlorine and calcium hypochlorite. Unbleached kraft pulp is used for grocery bags and heavy wrapping paper. Other materials may also be added to the pulp depending on the type of paper to be made. For book paper, fillers such as white clay and titanium oxide may be added to provide opaqueness and extra whiteness. Size may be added for stiffness and smoothness. Dyes are added for tinted papers. The specific combination of pulp and additives used to produce a particular type of paper is called the furnish for that paper. With better grades of paper, care is taken to produce a furnish that is chemically neutral (pH 7 on the acid-base scale). For a paper to have long life, it must be acid-free. 

There are three kinds at present. One is called gum rosin, which is obtained as the residue of the distillation of turpentine oil from pine resin, which is collected from pine woods. The second is called "wood rosin", which is obtained by extraction from chips of old pine stamps using a solvent. The third is the "tall oil rosin", which is obtained from the digester waste in the manufacture of kraft pulp. Rosin is produced in large amounts in America, Russia and China. At present wood rosin is mostly produced, and the tall oil rosin will gradually increase, but the production of gum rosin is decreasing. The most popular use of rosin is as size in paper production. 

Kerr and Uprichard (1976) devised a predietive mathematical model of bateh kraft pulping which incorporated other proeess variables, such as effective alkali, sulphidity and chip size, as well as the H factor. 

Fig. 3.45 TM-AFM phase images of (a) 15 min and (b) 45 min cooked spruce kraft pulp sample. Image sizes are (a) 2 x 2 pm2 and (b) 2 x 2 pm2. Reproduced with permission from [77]. Copyright 2003. Elsevier...

U Westemark, K Gustafson. Molecular size distribution of wood polymer in birch kraft pulps. Holtrforshung 48 146-150, 1994. 

Figure 7.42. High-resolution XPS (ESCA) spectra obtained for non-sized and sized bleached kraft pulp hand-sheets. Such spectra are used to quantify the amounts of, for instance, sizing agents, extractives, ketones, etc., present on cellulose surfaces...

We have tried to find a suitable level of P-PEG by adding 5 and 10% P-PEG. The results given below in table 1 are for medium size fibers of unbleached softwood kraft pulp. 

Table 1. Partition of medium size fibers, unbleached softwood kraft pulp. Results in percent...

We have sized a bleached softwood kraft pulp with AKD. We have taken a sample from this sized pulp. 

Base papers for abrasive papers are tough, sized papers made from kraft pulp and are coated with an abrasive. 

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