КАРБАМИДОФОРМАЛЬДЕГИДНЫЕ СМОЛЫ, НАПОЛНЕННЫЕ ТЕХНИЧЕСКИМ ДИОКСИДОМ КРЕМНИЯ

The effect of silicon dioxide (SDO) on the physico-chemical properties of urea-formaldehyde resins and plywood made with the modified resins, has been studied. SDO addition to the resin increases its acidity and reactivity. This reduces the consumption of catalyst for resin curing 1,5−2,0 times, and plywood, obtained using SDO, has higher mechanical strength.Изучено влияние диоксида кремния (ДОК) на физико-химические свойства карбамидоформальдегидных смол (КФС) и фанеры, изготовленной с использованием наполненных смол. Добавка ДОК в смолу приводит к увеличе­нию ее кислотности и повышению реакционной способности. При этом снижается расход катализатора отверждения смолы в 1,5−2,0 раза, а фанера, полученная с использованием ДОК, имеет более высокую механическую прочность

Fillers and catalysts effect on the physicochemical properties of urea-formaldehyde resins

In the present research the effect of different f illers on the composition of urea-formaldehyde resins (UFR) was studied. The usage of fillers in the composition of urea-formaldehyde resins makes it possible to reduce the resin consumption by 10–20%. Aluminum silicate type of fillers cannot be used conveniently in plywood technology because resin partic les initially agglomerate; then their swelling and hydration lead to the significant visc osity growth of the adhesive especially at a filler consumption rate more than 8% by weight of the resin. Sulfate and carbonate types of fillers can be used more preferable because in this case there are no agglomeration of resin particles and no quick solidification of adhesive composition. Viscosity of the adhesive composition decreases vice-versa with th e adding of silicate type filler into the urea-formaldehyde resin. Combining of different fillers types allows controlling the rheological properties of the adhesive composition. Compounds containing ions of three-valence meta ls are effective catalysts of urea-formaldehyde resins. The usage of such catalysts in plywood technology leads to condensation time reduction of urea-formaldehyde resins at 1.8–2.3 times which opens up additional possibilities for application of low-emission resins with a low formaldehyde content. Gelatination time of adhesive compositions prepared using the new effective catalysts for the condensation process of urea-formaldehyde resins remains for 2–4 hours

Investigation of the fiber composition effect upon sack paper properties

The article presents data on production volumes of sack paper, which is produced by the world's leading companies. The main raw material for the manufacture of this product is unbleached softwood sulphate pulp having a high cost. In the present research work the fiber composition effect upon sack paper properties was investigated. This makes it possible to determine the optimal mass ratio of unbleached kraft primary fibers (kraft pulp) and seco ndary fibers (waste paper) for the manufacture of sack paper. Doptimal continuous design (Kono, 1962) for the estimating second order polynomial full models was used as the experiment design for the optimization of the pulp fiber composition. Considering the restrictions on the quality parameters speci fied in GOST 2228–81 “Sack paper. Specifications” the analysis of the obtained experimental data using the search function in Mi crosoft Excel 2007 gave the following results on the sack paper fiber composition: kraft pulp content ( X1) – 43.30% of a. d. s.; polyacrylonitrile fibers content ( X2) – 0.15% of a. d. s.; waste paper content – 56.55% of a. d. s. During the experiment it was found that an increase of polyacrylonitrile fibers content from 0.05 to 0.20% in the kraft pulp structure leads to the increase of sack paper tensile strength by 25–28% (breaking length increased from 5,700 to 7,300 m). But paper whiteness at the same time decreased by 9.7%. This made possible to reduce the content of expensive kraft pulp in the composition of sack paper by 27% (taking into account the 30,000 t/year production of sack pa per, saving of kraft pulp can reach 8,000 t/year)

Softwood kraft pulping with polyacrylonitrile fibers

This article presents data on the polyacrylonitrile (PAN) effect upon the elastoplastic and mechanical properties of kraft pulp (unbleached softwood sulphate pulp). In the present research the possibility of obtaining in vitro sulphate pulp together with reinforcing agent of polyacrylonitrile was studied. PAN consumption was varied from 0.05 to 0.20 wt % based on the dry weight of the chips. Micrographs of cellulose samples showed that PAN was distributed on the surface of cellulose fibers in the form of fine spherical shape particles and made it possible to increase the strength of kraft pulp by 15?18% (breaking length was increased from 8,480 up to 9,990 m, breaking strength ?from 93.8 up to 109.5 N, energy absorption at break ?from 76.0 up to 92.6 J/m 2 and folding endurance ?from 7 up to 13 double folds)

Filled paper pulp sizing features in the presence of polyelectrolyte

It is shown that to reduce the size of the filler particles from 3–5 microns (natural) to 0.65–0.82 microns ({[CaCO3]m· nCO3 2– · (n – x)Na + } x– · xNa + ) allows for the filling process in geteroadagulation and penetration. To obtain high elevated paper with high-hydrophobic and strength properties it is advisable to sequentially introduced into the pulp slurry, calcium chloride and sodium carbonate to obtain superfine particles of filler (consumption10% of a. d. f.), then polyethylenimine (consumption 0.075% a. d. f.) and adhesive based on alkylketenedimer AKD (consumption 0.5% a. d. f.) demonstrating flocculating and sizing effect respectively