Strength Properties of Water Resistant Papers Prepared from Carbamoylethylated Pulps and the Water-resistance Improving Mechanism

以氨基甲酸乙酯纸浆为原料，制备了耐水纸张，并对其力学性能、制浆条件及耐水性改善机理进行了研究。纸浆化学改性的步骤如下：(1)P-OH+CH_2=CH-CN*P-O-CH_2-CH_2-CN(其中P为纸浆纤维)(2)P-O-CH_2-CH_2-CN+H_2O_2*P-O-CH_2-CH_2-ConH_2(3)P-O-CH_2-CH_2-ConH_2+NaC_1O*P-O-CH_2-CH_2-CON^-C_1WET-和干拉伸强度与未处理纸浆相比，N-氯化纸浆(N-Cl-P)纸页的性能有了很大的提高。尤其是取代度为0.04的N-Cl-P纸板的湿式拉伸强度与相应未处理纸浆的干式拉伸强度基本相同。经N-氯化处理后的纸浆耐折度、耐破强度、白度和尺寸稳定性也得到改善。纤维间尿素键的形成是提高耐水性的主要机理。在碱性介质中进行次氯酸盐处理，可以有效地降低纸浆的湿强度，使其能够进行再浆。在不加热的情况下，用最低用量的次氯酸盐处理N-Cl-P废纸，制得的废纸强度性能较好。

Water-resistant paper derived from carbamoylethylated pulp was prepared, and some mechanical properties, repulping conditions and the water-resistance improving mechanism were investigated. Chemical modification of pulps was carried out by the following three steps :(1) P-OH+CH_2=CH-CN * P-O-CH_2-CH_2-CN (where P is pulp fiber)(2) P-O-CH_2-CH_2-CN+H_2O_2 * P-O-CH_2-CH_2-CONH_2(3) P-O-CH_2-CH_2-CONH_2+NaC1O * P-O-CH_2-CH_2-CON^-C1Wet-and dry-tensile strength of N-Chlorinated pulp (N-Cl-P) sheets was highly improved compared to that of untreated pulp sheets. Especially, wet tensile strength of N-Cl-P sheets with DS 0.04 was nearly equal to the dry tensile strength of corresponding untreated pulp sheets. Folding endurance, burst strength, brightness and dimentional stability were also improved by N-Chlorination of Carbamoylethylated pulp. The main mechanism of water-resistance improvement is considered to be the formation of interfiber urea bonding. The hypochlorite treatment in an alkaline medium was effective for reducing the wet strength to be able to repulp. Strength properties of the recycled sheets from the repulping pulp were fairly good when N-Cl-P sheets were treated with the lowest amount of hypochlorite within possible defibering without heating.