低甲醛含量脲醛树脂粘合剂的合成方法研究

提出了降低脲醛树脂(UF)粘合剂中游离甲醛含量的措施以及改性的方法,摸索出了实用且简单可行的合成方法。根据此合成方法生产的产品具有黏度适宜、反应易控制、甲醛含量低、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。     

正丁醇改性脲醛树脂粘合剂的合成

本文对正丁醇改性脲醛树脂粘合剂的合成工艺条件进行了讨论。采用本工艺制得的粘合剂改性效果较好，且游离甲醛含量低，贮存稳定。     

降低脲醛树脂游离甲醛含量的研究

一、前言脲醛树脂粘合剂,由于制造工艺简单,价格低于其它木材加工用粘合剂,而且,具有较好的耐水、耐热及粘接性能,所以,在木材加工中作为主要粘合剂被广泛应用。然而,由于压合刨花板、胶合板、锯末板、竹合板,均在高温进行,所以脲醛树脂粘合剂的游离甲醛含量高时,势必散发大量的甲醛刺激臭味,严重地污染操作现场,强烈刺激操作人员的眼、鼻、喉,直接危害人身健康。因此,广大用户反映强烈,希望改用游离甲醛含量低,对人身无刺激的低毒性脲醛树脂。二、问题讨论为了降低游离甲醛含量,提高脲醛树脂     

低游离甲醛含量脲醛树脂胶粘剂的研究

研究了低游离甲醛含量脲醛树脂胶粘剂的合成新工艺,探讨了甲醛／尿素摩尔比、反应温度、pH值、以及加料的顺序等因素对脲醛树脂综合性能的影响,并采用三聚氰胺进行了改性,以提高耐水性及进一步降低产品中游离甲醛量。采用乙酰丙酮分光光度法测定了所制备胶粘剂中的甲醛含量。实验结果表明本工艺合成的脲醛树脂游离甲醛含量低、综合性能好,符合绿色环保的要求。     

低甲醛释放量人造板用改性脲醛树脂制备及应用研究

为了降低脲醛树脂的游离甲醛含量及其胶接制品的甲醛释放量,本研究在脲醛树脂合成过程中加入改性剂代替部分甲醛,通过尿素-甲醛-改性剂发生共缩聚反应,合成了改性脲醛树脂。研究了改性剂取代甲醛的摩尔比对改性脲醛树脂固化速度、游离甲醛含量的影响,以及在不同的热压条件下,对胶接胶合板的胶合强度和甲醛释放量的影响。研究结果表明,改性剂的加入不仅能有效降低改性脲醛树脂的游离甲醛含量及其胶合板的甲醛释放量,还能提高胶合板的胶合强度和耐水性。     

低毒耐水脲醛树脂胶的研制

本文提出一种脲醛树脂的合成方法:采用降低甲醛和尿素的摩尔比;加入改性物质聚乙烯醇;采用中低温合成工艺;在脲醛树脂的分子中引入尿素的环状衍生物。测试结果表明用该合成方法可降低脲醛树脂中游离甲醛含量,提高树脂的耐水性。     

铸造用糠醇改性脲醛树脂中游离甲醛的研究

本文分析了糠醇改性脲醛树脂中游离甲醛产生的机理,介绍了几种降低游离甲醛的可行方法。并提出了一种低游离醛糠醇改性脲醛树脂的合成方法。     

低毒耐水脲醛树脂胶的研制

本文采用降低甲醛和尿素摩尔比、同时加入改性剂聚乙烯醇和分批加尿素的方法合成脲醛树脂。可降低脲醛树脂中游离甲醛的含量．提高树脂的耐水性。     

环保型脲醛树脂合成的研究

探讨了环保型脲醛树脂的合成新工艺，综合研究了甲醛／尿素摩尔比、反应温度、pH值、以及加料的顺序对脲醛树脂胶黏剂性能的影响，并采用三聚氰胺进行了改性研究以提高胶黏剂的耐水性，同时降低产品中游离甲醛的含量。实验结果表明本工艺合成的脲醛树脂游离甲醛含量低、强度大、耐水性好，符合绿色环保型的要求。     

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     

Influence of glyoxal on curing of urea-formaldehyde resins

In the present paper, the effect of glyoxal on the gel formation within the adhesive systems based on urea-formaldehyde (UF) resins is shown. A reduction of formaldehyde content in wood-based panels by decreasing the formaldehyde/urea molar ratio in the UF resins leads to increasing of the UF resin gel time, and impairing the qualitative characteristics of the UF-based wood materials. Glyoxal is shown to speed up the crosslinking of the macromolecules as well as significant reduction of gel time of adhesive composition. The first reason is the result of reaction between glyoxal and ammonium ion leading to protons releasing. Another reason is that glyoxal and its interaction products react with macromolecules of the UF resin forming a three-dimension cross-linked structure. The gel time and the pot life of the UF resin are measured by the oscillatory viscometer. Formation of the UF cross-linked resin structure with glyoxal and a curing catalyst (ammonium sulfate) is studied using dispersion Raman scattering spectroscopy. Particleboards (PB) are produced using different amount of glyoxal and formaldehyde/urea molar ratio in the UF resin. The properties are evaluated according to the European Standards and include density, internal bond, thickness swelling moisture content and formaldehyde content.     

脲醛树脂胶黏剂低毒化改性剂研究进展

低毒化改性剂是指为了降低脲醛树脂及其制品毒性而在胶黏剂合成过程的不同阶段加入或在胶黏剂使用前加入的各种添加剂。从脲醛树脂胶黏剂游离甲醛的界定及其人造板甲醛释放机理、低毒化改性剂的国内外研究现状、低毒化改性剂的作用机理与选用原则等几个方面，综述了近几年来脲醛树脂胶黏剂低毒化改性剂的研究进展；并介绍了几种比较常用的单一类和复合类低毒化改性剂的降醛机理、作用效果及其使用方法，最后对低毒化改性剂的未来研究做了展望。     

脲醛树脂胶粘剂研究进展

从脲醛树脂胶粘剂的配方改进、胶粘剂合成工艺改进、甲醛捕捉剂的添加等几个方面,综述了近几年来脲醛树脂胶粘剂及其制品低毒化研究新进展。     

弱酸性条件合成脲醛树脂工艺的探讨

探讨了在弱酸性条件下合成低甲醛释放量的脲醛树脂工艺的可能性。同时，对不同pH值条件下合成脲醛树脂的工艺及其性能进行了研究，并采用傅立叶红外光谱和化学方法对脲醛树脂的官能团进行了分析，同时定性分析了不同pH值条件下合成树脂的热学性能。研究表明在弱酸性条件下合成脲醛树脂的树脂性能和其胶合板的力学性能达到国家标准并且其胶合板甲醛释放量达到GB／T17657—1999中的E，级标准。弱酸性条件下合成脲醛树脂的工艺不仅能降低生产成本，还能生产性能优异的脲醛树脂胶黏剂。     

Reduction of Formaldehyde Emission from Particleboard by Phenolated Kraft Lignin

The aim of this study was the reduction of formaldehyde emission from particleboard by phenolated Kraft lignin. For this purpose, the lignin was extracted from black liquor and then modified by phenolation. During the urea formaldehyde (UF) resin synthesis different proportions of unmodified and phenolated Kraft lignins (10%, 15%, and 20%) were added at pH = 7 instead of the second urea. Physicochemical properties and structural changes of resins so prepared, as well as the internal bond (IB) strength and formaldehyde emission associated with the panels bonded with them were measured according to standard methods. The Fourier transform infrared (FTIR) analysis of lignin indicated that the content of O–H bonds increased in phenolated lignin while the aliphatic ethers C–O bonds decreased markedly in the modified lignin. Since both synthesis of UF resins and lignin phenolation are carried out under acid conditions, phenolation is an interesting way of modifying lignin for use in wood adhesive. The panels bonded with these resins showed significantly lower formaldehyde emission compared to commercial UF adhesives. The UF resin with 20% phenolated lignin exhibited less formaldehyde release without significant differences in internal bond strength and physicochemical properties compared to an unmodified UF resin. XRD analysis results indicated that addition of phenolated lignin decreased the crystallinity of the hardened UF resins.     

竹碎料板用低毒脲醛树脂的合成工艺研究

在脲醛树脂(UF)的制备过程中,采用三聚氰胺对UF进行改性,制得低毒UF。结果表明:该低毒UF的固含量为49.88%,游离甲醛释放量仅为0.2026%;采用这种低毒UF胶粘剂压制的竹碎料板,其静曲强度为22.6MPa,弹性模量为2056MPa,内结合强度为0.58MPa,2h吸水厚度膨胀率为2.57%;该低毒UF是一种综合性能良好的木材用胶粘剂,其应用前景非常广阔。     

Renewable polyol‐based polycarbamates and polycarbamate–formaldehyde thermosetting resins

Several polycarbamates and polycarbamate–formaldehyde (CF) resins were synthesized, and their properties were investigated aiming at developing of useful thermosetting polymer materials from simple polyols including those derived from renewable resources. Polycarbamates synthesized from polyols using two‐step laboratory routes showed good storage stabilities making them suitable as large volume industrial chemicals. Furthermore, syntheses and ¹³C‐NMR studies of CF resins showed the formation of oligomeric resins having hydroxymethyl and methylene groups with thermosetting curing properties that are similar to those of current urea–formaldehyde (UF) resins. Dynamic mechanical analysis studies showed somewhat slower curing rates for CF resins compared to UF resins. Bonding of particleboard and internal bond and free formaldehyde content measurements indicated high‐bond strength values and very low‐formaldehyde emission potentials for CF resins. The higher functionalities of CF resins appear to be the basis of good performances. Further investigations on scalable synthesis methods for polycarbamates and on the expansion of CF resins' bonding capabilities would need to be investigated in the future. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Urea formaldehyde resin with low formaldehyde content modified by phenol formaldehyde intermediates and properties of its bamboo particleboards

Phenol formaldehyde reaction solution (PFS) was used to synthesize urea–formaldehyde resins (PFSUF resins) with low formaldehyde content. In addition, the prepared PFSUF resins were used as adhesives to bond bamboo particleboards. Mechanical properties, fracture morphology, water absorption ratio, and dimensional stability of bamboo particleboards have been studied by tensile tests, SEM tests, water absorption analysis, and swelling ratio analysis, respectively. The results demonstrate that the main ingredient of PFS is phenol formaldehyde intermediate 2,4,6‐trimethylolphenate and proper amount of PFS can be used to reduce the formaldehyde content of UF resins effectively. The results also show that bamboo particleboards bonded with PFSUF resins exhibit better mechanical properties, water resistance, and dimensional stability than that bonded with pure UF resin. However, the results of TG and mechanical properties analysis exhibit that alternative curing agents to ammonium chloride should be studied to improve the curing properties of the PFSUF resins with low formaldehyde content. Taken together, this work provides a method of preparing environment‐friendly PFSUF resins with low phenol and low formaldehyde content and the prepared resins have potential application in wood industry. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42280.