After pretreatment of viscose rayon with 10% caustic soda solution at room temperature, it was subjected to fibrous acetylation. After such a pretreatment are fibers in a swollen state and the acetylation proceeds as by homogeneous acetylation for the acetic anhydride penetrates easily into the fibers.
The acetylation was carried out using zinc sulfate and chloride as catalysts. The mechanism is generally complicated and the reaction type varies with the concentration of catalyst, temperature of the reaction etc. Under suitable conditions the first order equation of reaction fits for the acetylation rate.
A statistical and experimental approach to the study of uneven mixing of fibres in slivers and yarns caused by drawing process. The paper discusses that theoretical distribution of fibres in slivers and yarns holds Poisson distribution: where r: number of fibres per cross-section p: proportion of coloured fibres λ: mean number of fibres per cross-section. In this paper the problems of doubling is discussed only as a modification of Cox's formula, and the next report will deal with our formula concerning the doubling operation.
This paper discusses the theoretical equations for irregular arrangement of coloured fihres_??_in the yarn cross-section. The mean number (m) and variance (σ2) of the coloured fibres are expressed by: where λ: mean number of fibres per cross-section/total doubling p: proportion of coloured fibres.
Generally speaking, the knitted fabrics are deformed by a small force, so the expansive properties of fabrics show properties more precisely than the tensile strength of the knitted fabrics. In order to test them, fabrics are made by different construction and different tensions of warp yarns of warp knitting machine. These specimens are tested by expanding method to obtain the elongation percentage and stresses. The results obtained may be shown by the following equation. αP=Ew2 or αP=Ec2 where Ew: elongation in wale direction Ec: elongation in course direction P: pressure α: factor The multiplied value of elongation in wale by course direction is constant. The following equation is obtained. Ew•Ec=βK where Ew and Ec are same as given above β:area elongation factor K: orientation factor in specimens These results show that the properties of fabrics depend more on the properties of the loop rather than on the construction of fabrics and the tension of warp threads.
Stability of 14% dimethylol-urea solution aged 8 hours at 33°C in the presence of inorganic ammonium salt catalysts ((NH4)2HPO4 NH4Cl, and NH4SCN) and organic amine salt catalysts (dimethylaniline-HCl, pyridine-HCl, and Catalyst AC) was studied. The additions of the catalysts of inorganic ammonium salt seems to make the resin solution unstable, as they caused depression of pH, accelerated methylenisation and increased formation of free CH2O. Actions of these catalysts were of about same degree as when equal mol % of them was added to the resin matter contained in the solution. By adding organic amine salt catalysts, on the other hand, resign solutions were found very stable in effects same as mentioned above, especially Catalyst AC gave the best stability.
Experiments with selected substantive dyestuffs, it has been confirmed that the crystalline regions of natural and regenerated cellulose fibres obtained by Maeda's method show a characteristic dyeability according to crystalline structure and the spatial distribution, size, and uniformity of crystallites. As a rule, under the same dyeing condition, the crystalline region from the fibre of higher crystallinity shows a better dyeability. The materials arranged in order of dyeability of the crystalline region concerned are as follows: a) Cotton, b) Tramomen, c) Curled Rayon Staple, d) Tyre Cord Rayon, e) Ordinary Rayon, f) Ordinary Rayon Staple. This may be due to the hardening of crystalline regions while drying. The smaller the crystalline region, the more remarkable is the effect of hardening. In other words, dyeability decreases as the crystalline region becomes smaller. Generally the dyeability of a crystalline region is greater than that of the fibre itself. But dyeing behavior varies according to the dyeing conditions.
By investigating the dyeability of the crystalline regions of natural and regenerated cellulose fibres by the comparative dyeing method, the following results have been obtained: (1) Under the same dyeing condition, the dyeability of a crystalline region is greater than that of the fibre itself. (2) The velocity with which the dye particles spread over the crystallized portion varies with the difference in the kind of dyestuffs as well as in crystalline structure of the fibre concerned. It may be said that, in addition to the amount of crystalline substance contained therein, the size of the crystalline regions and the degree of their orderliness may also affect the distribution of dye in the fibre. (3) In the case of an excellently crystallised fibre such as cotton, much more dye particles tend to permeate into the crystalline regions than into the noncrystalline regions containing pseudocrystalline regions. But in the case of poorly crystallised fibres such as viscose rayon or staple, the dye diffuses much slowly through crystalline regions than through the noncrystalline regions containing pseudocrystalline regions. (4) It seems most probable that the difference of the distribution of dye in the crystalline and noncrystalline regions greatly affects the shade and fastness of dyeing.
Effects of some phosphates on starch size for warp sizing were studied, and following results were obtained: (1) Addition of small amount of Na4P2O7 and Na6P4O13 to starch size improves the sizing of spun yarns, and these effects are supposed to be common to polyphosphates. (2) Viscosity of starch size drops sharply and becomes more stable by addition of these phosphates. It may be explained by dispersion of starch micelles and promotion of homogeneous dispersion of starch particles caused by electric repulsion of the phosphates which combine to starch particles by the secondary force. (3) The improvements of sizing effects were also confirmed by investigations of adhesive power and some physical properties of films prepared from starch size, besides by increasing the breaking strength and resistance for abrasion of sized yarn. (4) By addition of these phosphates, starch size easily produces clear and flexible film, and it shows improvement in sizing effects, It is supposed that this modification is due to homogeneous orientation of starch molecules and construction of their network bridge by the phosphate molecules.