胶水级聚乙烯醇缩甲醛的实验条件探索

聚乙烯醇(PVA)是一种无色、无毒、无腐蚀性的水溶性有机高分子聚合物,但该产品在耐水性、黏度和抗冻性等方面尚不能满足要求,人们采用缩醛改性、酯化改性、内酯改性、疏水改性等方法对其性能进行优化,其中缩醛改性应工艺简单、改性效果明显而得到广泛应用。本文以聚乙烯醇缩甲醛实验制备为重点,探讨了水和聚乙烯醇的配比、甲醛用量、反应时间、反应温度、p H值等因素对胶粘剂性能的影响。在此基础上,提出了改进工艺的最佳条件,制备了聚乙烯醇缩甲醛改性胶液,使其在黏度、耐水性等性能方面有显著提高,并降低了胶液的甲醛含量。     

新型水溶性聚乙烯醇缩甲醛涂料的研制

在pH值为1.5~2的条件下,以聚乙烯醇和甲醛为原料,在水溶液中发生缩醛反应制备聚乙烯醇缩甲醛胶,然后向胶中添加适量的尿素和分散助剂PAAM/COB,经调配得到新型水溶性聚乙烯醇缩甲醛涂料。结果表明,颜基比为4∶1,颜、填料粉末的粒度为320目时,添加适量的尿素和分散助剂PAAM/COB,所制得的涂料游离甲醛含量低。     

降低107胶类内墙涂料中游离甲醛含量的方法

一、前言 107胶类内墙建筑涂料,是由聚乙烯醇与甲醛在酸性介质中缩醛化反应而生成的聚乙烯醇半缩醛胶(简称107胶)作为基料,混合一定量的颜料、填料等经研磨而制成的。为了提高涂料的耐水性和粘结力,必须提高聚乙烯醇缩甲醛的含量,但是聚乙烯醇缩甲醛的含量,只能通过加大反应物甲醛的浓度来提高。在反应物中甲醛量越大,生成的缩甲醛量就越多,相应地胶体中游离甲醛量越多。游离甲醛是挥发性液体,有强烈的刺激气味,对人体的呼吸道粘膜有刺激作用,施工时极为不便。尤其是长期吸入这种     

PVA缩甲醛地毯粘合剂

以聚乙烯醇(PVA)为主,用甲醛改性,再配制混合交联剂,而制得PVA缩甲醛地毯粘合剂,介绍了高缩醛化度的PVA缩甲醛胶液的制备方法,产品性能,使用方法及简易工艺流程等。     

塑型塑编布—纸粘合剂

以聚乙烯醇为基料，采用缩醛化反应方式，制备出高粘度聚乙烯醇缩甲醛，再以ＶＡＥ为主料，与聚醇缩甲等其它几种原料复配成一种水溶性的塑编布－纸粘合剂。     

耐寒型聚乙烯醇缩甲醛胶的研究

本文主要分析了聚乙烯醇缩甲醛胶耐寒性差的原因,在此基础上提出了解决耐寒性问题的两种方法,其一是高缩醛化聚乙烯醇缩甲醛,另一种是聚乙烯醇氧化改性再缩甲醛,并对这两种生产工艺所生产的胶水的性能和其用途等进行了探讨。     

催化剂对聚乙烯醇缩甲醛改性PVAc乳液性能的影响

以聚乙烯醇缩甲醛（PVF）为保护胶体,采用半连续种子乳液聚合方法,合成了固含量为18％左右的聚醋酸乙烯酯（PVAc）乳液,研究了缩醛反应的催化剂种类（硫酸H2SO4、盐酸HCl）、pH值对乳液中游离甲醛含量、缩醛度、黏度及对胶接强度的影响。采用傅里叶变换红外光谱（FTIR）、接触角测量等对乳液的结构和性能进行了表征。研究结果表明,不同的催化体系对乳液性能的影响不同。随着pH4值的降低,乳液中游离甲醛含量降低,PVF的缩醛度升高,乳液黏度和胶接强度均呈先升高后降低的趋势。催化荆种类和pH值对乳液接触角无显著影响。用H,SO。作为缩醛反应的催化剂,反应的pH值为34时,合成乳液的综合性能最佳。     

改性淀粉在降解塑料中的应用研究

介绍了改性淀粉在降解塑料中的应用 ,具体阐述了利用交联淀粉、阳离子淀粉制备可降解塑料片材 ,利用淀粉与聚乙烯醇通过甲醛缩醛化反应制备可降解塑料膜 ,利用接枝淀粉与PE、EVA共混改性制备可降解塑料的生产工艺     

聚乙烯醇缩醛树脂中残留甲醛含量的影响因素

以尿素为甲醛捕捉剂,探讨了缩醛反应时间、反应温度、甲醛和聚乙烯醇的配比、盐酸、尿素、氢氧化钠等对聚乙烯醇缩甲醛溶液中残留甲醛含量的影响。结果表明,增加缩醛反应时间,利于降低产物游离甲醛含量。缩醛反应温度太低,产品中残留甲醛含量高。当反应温度由75℃增至88℃时,残留甲醛含量呈先快后慢的下降趋势变化。随投料中甲醛用量的提高,产物游离甲醛含量直线上升。当m（盐酸）：m（PVA）由0．12增至0．29时,甲醛残余量则由0．247％降至0．216％。增加尿素用量,甲醛残余量先快速下降,然后缓慢下降。增加氢氧化钠用量,残留甲醛含量先缓慢增加,后快速增加。     

强力快干型抗冻乳白胶的研制

介绍了一种以改性的聚乙烯醇缩甲醛为基料的强力快干型抗冻乳白胶。在常规缩醛化工艺操作的基础上作了很大的改进，它在缩甲醛反应终点时利用反应物液、固相临界点的脱水现象进行水洗，洗除反应物中过多的游离甲醛，使缩甲醛胶液通过水洗，具有低温抗冻的特性和贮存稳定性。然后调节乳化剂的加入量又获得很高的粘接强度和快干的功能。这样不仅改变了用料品种、缩短了反应周期，而且使整个反应时间控制在3h以内。     

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.     

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。     

Adhesives and coatings based on poly(vinyl acetal)s

Phenolic resins such as resole phenol– and cresol–formaldehyde, as well as low-molecular-weight epoxy resin based on bis(4-hydroxy phenol) cyclohexane were prepared and modified with various types of the prepared poly(vinyl acetal)s. Poly(vinyl formal), poly(vinyl isobutyral), and poly(vinyl propional) were used. This study indicated that the optimum conditions for curing phenolic or epoxy resin–poly(vinyl acetal)s adhesive compositions are of an equal weight ratio or a 2 : 1 weight ratio in the presence of phthalic anhydride (10 or 20 wt %) of resin content as a curing agent at 150°C for 20 or 60 min, respectively. The effect of acetal type on the tensile shear strength values of resin samples, cured under the previously mentioned optimum conditions for different times, was investigated. The effect of structure of cresol–formaldehyde and epoxy resins was also studied. Metallic and glass coatings from the previous pure resins and their formulated mixtures were also prepared and evaluated as varnishes or paints. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 1769–1777, 1998     

Reactive acid curing waterborne microparticles

This paper describes and evaluates different techniques for introducing acetal functional groups on waterborne microparticles. Aqueous dispersions of microparticles consisting of 70 wt.% styrene and 30 wt.% ethylacrylate were prepared by emulsion polymerization. Copolymer particles and core-shell particles were produced. The particle diameters were varied in the range from about 50 to 150 nm. The particles surfaces were modified by introducing an acetal functionality. Surface functionalization was performed in two different ways. Surface reactivity was introduced by the use of an acetal functional group containing an acrylic monomer in the polymerization step. The acetal functional groups were also introduced through post-polymerization grafting techniques. The particle surfaces were modified by introducing an acetal functionality, suitable for waterborne acid curing binder systems. The functionality in question is a diacetal, which recently has proved to undergo acid catalyzed crosslinking at ambient temperatures [1]. Acetal functionalized microparticles might replace amino resins. Crosslinking between amino resins produces formaldehyde but crosslinking based on acetals does not produce formaldehyde.     

环境友好聚乙烯醇粘合剂研究

由于较强的粘结力,聚乙烯醇粘合剂有着广泛的应用,但大部分是聚乙烯醇缩醛类。文章研究了聚乙烯醇与硅氧烷交联剂反应制取环境友好型粘合剂,并探讨了影响其性能的因素。实验结果表明,交联后的聚乙烯醇粘合剂性能优于聚乙烯醇缩醛粘合剂,而且无毒无害,是一种优良的环保材料。     

醇醛—脲醛复合氧化纤维素胶泥粘合剂的研制

本工艺通过复合、脲醛处理、氨处理等办法，使缩醛粘合剂转态，最大限度地限制了类似普通缩醛类粘合剂甲醛的释放，拓宽了两种缩醛粘合剂的用途。     

Development of a new advanced process for manufacturing polyacetal resins. Part III. End-capping during polymerization for manufacturing acetal homopolymer and copolymer

Conventionally, acetal homopolymer or copolymer is obtained by the polymerization of formaldehyde or trioxane, following the end-capping using acetic anhydride or unzipping of the unstable polymer end fraction. First, Asahi Chemical developed a new process to obtain an end-capped polymer during polymerization of highly purified formaldehyde using acetic anhydride as the chain-transfer agent. Use of highly purified formaldehyde and endcapping during polymerization using acetic anhydride as a chain-transfer agent or an endcapping agent will provide a simple process for manufacturing acetal homopolymer. The polymerization mechanism was confirmed by infrared spectroscopy analysis and proton NMR analysis of the polymer obtained. Second, for the acetal copolymer, purified trioxane was copolymerized with ethylene oxide in the presence of methylal, which gave an endcapped polymer with high thermal stability. Two new intermediates from the initiation reaction of the copolymerization, 1,3,5,7-tetraoxacyclononane (TOCN) and 1,3,5,7,10-pentaoxacyclododecane (POCD), were isolated and a new initiation mechanism was proposed. © 1993 John Wiley & Sons, Inc.     

缩醛类树脂在油田堵水中的应用初探

本文讨论了缩醛类树脂在油田堵水中的应用,分析了国内外发展现状,并对脲醛和呋喃树脂技术及其施工工艺进行了探讨,结果表明缩醛类树脂是一种耐温抗盐、高强度和封堵能力极强的封堵材料。     

木质素在胶粘剂中的应用研究进展

介绍了木质素的结构、分类与性能以及改性方法,综述了木质素在酚醛树脂胶粘剂、脲醛树脂胶粘剂、三聚氰胺甲醛树脂胶粘剂、环氧树脂胶粘剂以及聚氨酯胶粘剂中的应用研究进展,并对今后的研究方向作了展望。     

Low‐volatility acetals to upgrade the performance of melamine–urea–formaldehyde wood adhesive resins

1,1,2,2‐Tetramethoxyethane (TME), a high boiling point acetal derived from glyoxol, lhas been shown to upgrade the performance of melamine‐urea‐formaldehyde (MUF) and some UF resins used for wood adhesives. This affords the possibility of decreasing the percentage of resin used in the preparation of wood panels without volatilizing the TME acetal used.