淀粉改性聚乙烯醇缩甲醛树脂的工艺研究

由于传统的PVA缩醛树脂是由PVA和甲醛制备的,所以树脂中的游离甲醛含量高。通过改变合成工艺,用淀粉对聚乙烯醇缩甲醛树脂进行改性,制得了游离甲醛含量低的树脂。考察了淀粉用量、体系pH值、反应时间、反应温度对树脂性能的影响,并采用了红外光谱对树脂结构进行了表征。根据此合成方法生产的产品具有工艺简单、游离甲醛含量低、耐水性能好、成本低等优点。     

低游离甲醛的582-2氨基树脂的研制

介绍了低游离甲醛含量的582-2氨基树脂的配方、工艺优化、氨基树脂质量指标、清漆涂膜性能。     

氨基树脂中游离甲醛的测定

一、前言丁醇醚化氨基树脂中游离甲醛含量,是考核配方、反应条件的合理性及树脂质量的一项重要指标。目前测定甲醛的一般方法,数据相差十分悬殊,因而难以准确判断树脂中游离甲醛的含量。通过试验,我们认为,准确测定的关键在于能否将树脂中的游离甲醛全部萃取入溶液中进行定量反应。本文比较了测定甲醛含量的不同方法,并采用丁醇作溶剂,取得了令人满意的结果。二、试验和结果1.测定方法的比较(1)配制甲醛标准溶液确定理论百分含量     

酶解淀粉改性三聚氰胺甲醛树脂的研究

以淀粉(S)、甲醛(F)、三聚氰胺(M)为主要原料,合成酶解淀粉(ES)改性三聚氰胺甲醛树脂(ESMF),分析了ES添加量、淀粉种类对ESMF树脂性能的影响,并对ES成分和ESMF树脂的结构进行了探讨.研究结果表明:随着ES添加量的增加,ESMF树脂的黏度、固体含量逐渐下降;游离甲醛含量下降,最低为0.186％;贮存期...     

低成本蜜胺树脂的制备

采用淀粉对蜜胺树脂改性,研究了淀粉和甲醛用量、pH值及反应温度对蜜胺树脂的稳定性和游离甲醛含量的影响,结果表明,优化的工艺条件如下:淀粉用量2 g,37%甲醛溶液用量25 mL,pH值8.5~9.0,反应温度80℃,产物蜜胺树脂游离甲醛质量分数为1.8%,可在常温下存储近3个月。     

阳离子醚化淀粉改性脲醛树脂胶黏剂的研究

在脲醛树脂的合成过程中,分别添加木薯淀粉、阳离子醚化淀粉和α-淀粉酶改性木薯淀粉,通过实验确定了脲醛树脂胶黏剂性能最优时的淀粉品种,并考察了不同添加时段与淀粉的不同添加量对树脂中游离甲醛含量的影响。结果表明,在反应后期添加6%的阳离子醚化淀粉,改性合成的脲醛树脂胶黏剂,其固化时间为45.6s,固含量为57.16%,黏度为135.96 mPa·s,游离甲醛含量为0.19%,符合GB/T 14732-2006标准,且游离甲醛的含量最低,效果最佳。     

蜜胺－脲甲醛树脂新型制法研究

蜜胺－脲甲醛树脂新型制法研究刘荣杰（西北大学化工系，西安７１００６９）涂料用氨基树脂系指一种含有氨基官能团的原料与甲醛反应、再以醇类改性制得、能溶于有机溶剂的树脂，如蜜胺（三聚氰胺）甲醛树脂、脲醛树脂等，在我国，氨基树脂的生产已有２０多年的历史，目前...     

应用于粉末涂料的固化反应(续)

<正>(接上期)7用氨基树脂固化氨基树脂作为涂料固化剂已被关注和研究了许多年。用于涂料工业的4种不同类型的烷基化氨基甲醛树脂是:尿素、三聚氰胺、苯代三聚氰胺和甘脲甲醛树脂。氨基树脂中存在以下官能团:     

氧化木薯淀粉改性MUF树脂的性能与固化特征

通过在三聚氰胺-尿素-甲醛树脂(MUF)合成反应的不同阶段添加氧化木薯淀粉,制备得到了不同系列树脂,分别为MUF0、MUF1和MUF2,并对其基本性能及粘接强度进行了测试和分析。为了进一步了解氧化木薯淀粉对MUF树脂固化反应的影响,借助差示扫描量热分析仪(DSC)对树脂在不同升温速率条件下的固化特征参数及固化行为进行了表征。结果表明,在合成反应不同阶段加入氧化木薯淀粉,可有效提升树脂的粘接性能并降低树脂中的游离甲醛含量,特别是在树脂合成反应的第3阶段进行添加,效果更为显著。利用Kissinger方程对不同树脂的固化动力学参数进行分析,得到了树脂固化反应的表观活化能E a,表观频率因子A和反应级数n,并建立了固化反应动力学模型。在本试验条件下,树脂经过氧化木薯淀粉改性后,虽然固化所需活化能有不同程度的提高,但可形成更高的粘接强度。     

低醚化氨基树脂合成工艺及配方的优化

以三聚氰胺、甲醛,异丁醇为原料合成低醚化度的氨基树脂,探讨了羟化时间,醚化时间,脱水方式和减压脱水时间对树脂性能的影响,采用正交实验对原料配方进行了优化,综合平衡法得出最佳合成工艺条件。     

聚乙烯醇-乙二醛缩醛树脂的合成工艺研究

由于传统的聚乙烯醇缩醛树脂是由PVA和甲醛制备的,树脂中的游离甲醛含量高.通过改变合成工艺,用乙二醛替代甲醛,与PVA缩聚制备出了游离甲醛含量低的树脂.考察了反应时间、反应温度、体系pH值对树脂粘度的影响,并采用了红外光谱对树脂结构进行了表征.     

脲醛树脂改性工艺中的酸度条件控制

普通脲醛树脂及氧化淀粉改性脲醛树脂的合成工艺中 ,酸度控制条件对合成产物稳定性、剪切强度、游离甲醛含量等性能影响的研究表明 ,缩合反应阶段尿素投入时体系pH值对脲醛树脂合成过程以及产物稳定性都有显著性影响。缩合阶段体系的pH值控制范围直接影响脲醛树脂的稳定性、粘合强度与游离甲醛含量。从脲醛树脂稳定性考虑 ,投入第三批尿素后的pH值应控制在 6 .0以上     

淀粉基生物质胶粘剂的固化与性能研究

将淀粉在硫酸作用下水解的产物用于替代甲醛与苯酚进行缩聚反应生成淀粉基酚醛树脂,然后以六次甲基四胺为固化剂进行交联固化。研究了淀粉基酚醛树脂的凝胶时间、固化反应表观活化能、冲击强度、热失重性能与断面形貌,并与甲醛基酚醛树脂性能进行比较。结果表明,淀粉基酚醛树脂的固化反应表观活化能为19.8kJ/mol,冲击强度为741J/m2,600℃质量残留率为40%,具有良好的耐热性能,游离甲醛质量分数仅为0.4%,大大低于常规酚醛树脂的甲醛含量。     

氧化淀粉改性脲醛树脂的研究

用玉米淀粉为原料,通过H2O2氧化制成氧化淀粉,糊化后加入到脲醛树脂中,制得不同氧化淀粉含量的改性脲醛树脂,与不含氧化淀粉的脲醛树脂胶粘剂的性能对比,具有游离甲醛、羟甲基含量低和粘合强度好等优点,而且成本也大大降低,表明可有效地改善脲醛树脂胶粘剂的综合性能。     

Dependence of properties of aqueous resols upon conditions of synthesis

Phenol formaldehyde resins of resol type were prepared under molar ratio phenol: formaldehyde: calcium hydroxide 1:2.7:0.1. The reaction products contained in all cases about 3.8% free formaldehyde and 1.5% free phenol. A 36% solution of formaldehyde was used for synthesis. The course of synthesis, expressed by drop of free formaldehyde contents in the reaction mixture, is presented. In aqueous resol solutions, prepared by this way, the decrease of miscibility with water was examined during storage at 10°C. It was found that the resol synthesized at lower temperature had better shelf life than that prepared at higher temperature. The presented results are of practical importance in the cases where compatibility with water is a significant processing parameter.     

Modification of phenol–formaldehyde resol resins by lignin,starch, and urea

Lignin‐based chemicals, starch, and urea were used as modifiers for phenol–formaldehyde resol resins. The effects of the addition stage of the modifiers used in the synthesis of the resins and the type of modification reagent on the structures of the resins and their molar masses and reactivities were investigated. The modifications with corn starch and lignin promoted condensation; this was verified by increased molar masses and high ratios of methylene bridges to the sum of free ortho and para aromatic groups with respect to the corresponding reference resin without a modification reagent. The later the modifier was added to the resin condensation mixture, the more methylene bridges were formed with respect to the amounts of free ortho and para aromatic groups. In addition, when urea or wheat starch was added in the later condensation stage, the final condensation also reached high stages. The modifications with lignosulfonate and starch, as well as the early addition of urea, enhanced p–p′ bridge structures. The lowest condensation stage and, therefore, the highest reactivity were found when wheat starch was added with the starting reagents. The curing heat of the wheat‐starch‐modified resins decreased according to the deferred addition point of starch. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 582–588, 2003     

低游离醛高羟甲基含量酚醛树脂的合成

通过实验,以CaO作催化剂合成了低游离醛高羟甲基含量酚醛树脂。采用正交试验方法研究了催化剂用量、反应温度、反应时间对酚醛树脂的游离醛含量、羟甲基含量2个指标的影响。当n(苯酚)∶n(甲醛)=1∶1 2～1 3时,最优工艺条件为:n(催化剂)∶n(苯酚)物质的量比0 02、反应温度70℃、反应时间3h。     

Melamine‐bridged alkyl resorcinol modified urea–formaldehyde resin for bonding hardwood plywood

A powdery product was obtained by the reaction of methylolated melamine with alkyl resorcinols to form melamine‐bridged alkyl resorcinols (MARs). The effects of the addition of this powder on the bonding strength and formaldehyde emission of urea–formaldehyde (UF) resins were investigated. Three types of UF resins with a formaldehyde/urea molar ratio of 1.3 synthesized by condensation at pH 1.0 (UF‐1.0), pH 4.5 (UF‐4.5), and pH 5.0 (UF‐5.0) were fabricated. The addition of MAR to UF‐4.5 and UF‐5.0 for bonding hardwood plywood enhanced the bonding strength and reduced formaldehyde emission. For UF‐1.0, the addition of MAR adversely affected the bonding strength. However, the UF‐1.0 resin yielded the lowest formaldehyde emission of all of the UF resins in the study. The effects of the MAR addition were related to the molecular structures of the UF resins. UF‐1.0 contained a large amount of free urea, a considerable number of urons, and a highly methylene‐linked, ring‐structured higher molecular weight fraction and had a smaller number of methylol groups. Therefore, the addition of MAR was considered to cause a shortage of the methylol groups, which in turn, led to incomplete resin curing. In contrast to UF‐1.0, UF‐5.0 contained a smaller amount of free urea and a linearly structured higher molecular weight fraction and had a larger number of methylol groups. In this case, MAR was considered to effectively react with the methylol groups to develop a three‐dimensional crosslinked polymer network to enhance the bonding strength and suppress the generation of free formaldehyde to reduce formaldehyde emission. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

环保型脲醛树脂粘合剂合成的研究

脲醛树脂是广泛用于木材工业中一种重要的胶粘剂。对降低脲醛树脂粘合剂中游离甲醛含量的措施以及改性方法进行了探讨,并在大量的实验基础上摸索出了一套简单实用的合成工艺,根据此合成方法生产的产品具有粘度好、反应条件易控制、甲醛含量低和成本低等优点,树脂的甲醛含量达到国家室内板用粘合剂游离甲醛含量标准(GB18 587-2001)。