生物质甲醛捕捉剂廉价高效

中国工程院院士杨锦宗（大连理工大学教授）研制的以廉价、可再生的生物质为原料生产的甲醛捕捉剂，加入到脲醛树脂胶中，能有效地降低人造板中甲醛释放量，生产工艺简单，成本低、环境污染小，基本不影响人造板的质量。该成果不仅环保，而且市场潜力巨大。     

树脂型甲醛捕捉剂的研制

在常规脲醛树脂制备工艺基础上,成功制备了树脂型甲醛捕捉剂。借助13C-NMR和GPC分析方法,研究了甲醛捕捉剂的结构特点及分子质量分布。将其与自制的低物质量比脲醛树脂混合使用,考查了甲醛捕捉剂对脲醛树脂性能的影响。结果表明,该甲醛捕捉剂不含游离甲醛,已实现一定程度的树脂化。甲醛捕捉剂中大量游离尿素及一羟甲基脲等低分子质量物质的存在能有效降低刨花板的甲醛释放量,但对混合树脂的最终强度不利。添加甲醛捕捉剂对脲醛树脂的固化行为影响较小。当脲醛树脂与甲醛捕捉剂质量比为85/15、热压时间为4min时,刨花板性能较佳。     

低游离甲醛可发性液态酚醛树脂的制备

以苯酚和多聚甲醛为原料合成可发性液态酚醛树脂,考察了催化剂、甲醛与苯酚摩尔比、反应温度、反应时间和甲醛捕捉剂对酚醛树脂中游离甲醛含量及酚醛树脂黏度的影响。结果表明:以复合催化剂作为催化剂,用量为苯酚质量的5%,采用逐步升温工艺,在60~70℃条件下反应3.0 h,80℃条件下反应2.5 h,添加盐酸羟胺与尿素组成的复合甲醛捕捉剂于80℃继续反应0.5 h,得到的可发性液态酚醛树脂的游离甲醛质量分数为0.12%,黏度为3.97 Pa·s。     

改性凹凸棒土对脲醛树脂甲醛释放量的影响

通过采用三种甲醛捕捉剂对凹凸棒土进行改性处理,研究探讨了改性前后凹凸棒土对甲醛饱和蒸气的吸附量及其对脲醛树脂甲醛释放量的影响。结果表明:凹土经过改性后,可以提高其对甲醛气体的吸附量,而且作为填料加入树脂后亦降低了树脂的甲醛释放量。经甲酰胺和二乙醇胺改性试样对树脂甲醛释放量影响效果最佳。     

耐水型低甲醛脲醛树脂

兰州石化公司研究院开发 ,且通过了甘肃省科技厅组织的专家鉴定。采用多种原料和多次投料新工艺。技术上该工艺中使用了甲醛捕捉剂 ,同时选用多种助剂 (协同效应好 ) ,在降低醛浓度的含量同时延长了产品贮存期及提高粘结性能。耐水型低甲醛脲醛树脂@王沛熹     

添加型甲醛捕捉剂的功效研究

对几种代表性的添加型甲醛捕捉剂(如乙烯脲、壳聚糖、己二酸二酰肼、间苯二酚、尿素、单宁酸以及花生壳液化物等)进行功效分析,采用乙酰丙酮分光光度法分析消醛率以及消醛率随时间的变化规律;以胶合板的甲醛释放量和胶接强度为指标,探讨了甲醛捕捉剂对胶合板上述性能的影响。研究结果表明:甲醛捕捉剂在胶粘剂中的消酫效果依次为己二酸二酰肼乙烯脲壳聚糖间苯二酚,而尿素对甲醛的捕捉性能与温度和p H有关。上述甲醛捕捉剂均能有效降低胶合板的甲醛释放量(均达到E_1级标准),并且甲醛捕捉剂中己二酸二酰肼、乙烯脲和间苯二酚应用于胶合板的效果较佳,而且前两者在降低板材甲醛释放量的同时对胶接强度的影响也不大。     

甲醛捕捉剂对三聚氰胺泡沫塑料性能的影响

在三聚氰胺甲醛树脂中分别加入氧化剂型、氨基衍生物型和硫化物等甲醛捕捉剂,然后通过微波发泡制备三聚氰胺泡沫塑料,讨论了不同类型的甲醛捕捉剂对三聚氰胺甲醛树脂及泡沫塑料性能的影响。结果表明,氨基衍生物型甲醛捕捉剂不仅能有效地降低树脂中甲醛含量,还能延长树脂储存时间,其中带有脲、亚氨基和烷基基团的IH–2型氨类甲醛捕捉剂具有较高的捕捉甲醛能力,当其质量分数为5%时,树脂储存时间由2 d延长到5.3 d、游离甲醛含量由5.42%降低到0.23%,且对应的三聚氰胺泡沫塑料甲醛释放量为0.31 mg/L,低于业内称为"零甲醛"E0级产品的甲醛释放量上限值(0.5 mg/L);与未加甲醛捕捉剂的相比,加入质量分数为5%的IH–2,可使泡沫塑料的回弹率、撕裂强度、拉伸强度和断裂伸长率分别提高了12.7%,40%,31.3%和35.4%。     

固体型甲醛消除剂的合成与应用研究

以亚硫酸氢钠与氢氧化钠为原料合成固体型甲醛消除剂,以干燥器作为模拟室,在模拟室中进行甲醛消除剂捕捉甲醛的实验。考察了捕捉时间和亚硫酸氢钠与氢氧化钠的比值对甲醛消除率的影响。实验结果表明,当反应时间为40 h、NaHSO3与NaOH的比值为10时,甲醛消除率最大。     

木质素在人造板胶黏剂中的应用

综述了木质素在酚醛树脂、脲醛树脂、三聚氰胺甲醛树脂3种人造板胶黏剂中的应用进展，指出了利用无毒、稳定、价廉、可再生的木质素代替不可再生且有毒的苯酚、甲醛制取工业用人造板胶黏剂是木材用胶黏剂领域的重要研究方向。     

低毒脲醛树脂胶粘剂的研究进展

综述了低游甲醛脲醛胶粘剂的合成技术,对原料摩尔比、改性剂、缩聚工艺、甲醛捕捉剂等因素进行了讨论。     

Formaldehyde emission from PVC–wood composites containing MDF sanding dust

The main purpose of this work was to study the formaldehyde emission from wood plastic composites (WPCs) containing polyvinyl chloride (PVC), wood flour, and sanding dust of medium density fiberboard (MDF). Wood floor was replaced with 10, 15, and 20% MDF sanding dust (as a wood‐based panel waste), and the composites were manufactured by the extrusion method. Formaldehyde emission from WPCs was measured using two different methods: the desiccator method according to ISO 12460 and the flask method according to EN717‐3. Moreover, the physical and mechanical properties of the WPC samples were determined. The results indicated that the use of MDF sanding dust in formulation of WPCs leads to higher formaldehyde emission. The composites with higher content of MDF sanding dust exhibited higher formaldehyde emission. Although the PVC composites containing MDF sanding dust release formaldehyde, the formaldehyde emission values were very low. Therefore, these composites can be considered to be green composites and there is no concern in their indoor applications. J. VINYL ADDIT. TECHNOL., 25:159–164, 2019. © 2018 Society of Plastics Engineers     

Relationship between curing activation energy and free formaldehyde content in urea-formaldehyde resins

This study investigated the effect on the curing behavior, activation energy (E _a) of the curing reaction, crystalline structure, crosslinking, and free formaldehyde content of the addition of the following scavengers in urea-formaldehyde (UF) resins: medium density fiber board flour, rice husk flour, silica powder, and tannin powder. The scavenger content was 3 and 7?wt% of the UF resin solid content. The curing behavior of UF resins was monitored by differential scanning calorimetry, thermogravimetric analysis, and X-ray crystallography. The curing E _a was correlated to the free formaldehyde content of the scavenger containing UF resins. The thermal stability of the UF resins increased but the curing E _a decreased with increasing scavenger content. After curing, the crystallinity of the UF resins decreased in the presence of scavengers. The unreacted free formaldehyde content was reduced in the tannin powder containing UF resins. The degree of crosslinking affects the formaldehyde emission from wood panels bonded with UF resin. This is especially true for wood panels in service for long periods of time and exposed to high humidity conditions. Once the free formaldehyde which influences considerably the emission has disappeared, the presence of the –CH₂– groups then becomes important. Hence, an increased resin crosslinking indicates a higher concentration of –CH₂– groups present, which may hydrolyze and emit formaldehyde slowly over time.     

Applicability of Oxidative Systems to Initiate Grafting on and Bonding of Wood

Graft polymerization techniques were applied to induce bonding in wood composites. Wood surfaces were activated with an oxidant such as hydrogen peroxide, nitric acid, peracetic acid, potassium ferricyanide or sodium dichromate. The activated wood surfaces were then chemically crosslinked with polymerizing materials such as furfuryl alcohol, ammonium lignosulfonate, mixtures of lignosulfonate with furfuryl alcohol, with formaldehyde or with maleic acid. The wood composites were pressed using conventional manufacturing conditions. The strength and water resistance properties of the wood composites were suitable for exterior structural applications. The various methods proposed to induce chemical bonding of wood are briefly reviewed.     

甲醛消除剂处理胶合板性能研究

在BL-甲醛消除剂A中加入一定量的分子筛和光触媒后,可制成新型甲醛消除剂B。研究结果表明:胶合板表面经甲醛消除剂B处理后,其甲醛释放量明显降低;当甲醛消除剂B的双面喷涂量为1.2～3.5 g/m2时,胶合板的甲醛消除率为73.5%～98.7%,其再胶接强度基本不变,并且其甲醛消除持久性较长(60 d内甲醛消除率仍不低于86.7%)。     

Composite materials manufactured from wood particles modified through a reactive extrusion process

Wood‐based composites such as particleboard and medium‐density fiberboard are currently made with formaldehyde‐containing adhesives. Since the government is continuously developing and implementing very stringent regulations to eliminate formaldehyde emissions into the environment, alternative approaches must be developed to replace these adhesives. This study examined the concept of using a reactive extrusion process as a means of developing a new, formaldehyde‐free binding system for wood composite products. The surfaces of wood particles were modified by grafting maleated polyolefins through a continuous reactive extrusion process. Chemical changes resulting from this treatment were followed by studying the Fourier transform infrared (FTIR), ¹³C nuclear magnetic resonance (NMR), and X‐ray photoelectron spectroscopy (XPS) spectra. The modified wood particles were compression‐molded into panels, which were tested for mechanical properties. FTIR, ¹³C NMR, and XPS data revealed that the chemical reactions have taken place between the hydroxyl groups of wood particles and maleated polyolefins. The mechanical property test results indicated that the composite panels compared favorably with current standard requirements for conventional particleboard. POLYM. COMPOS., 26:534–541, 2005. © 2005 Society of Plastics Engineers     

环保型脲醛胶的制备与性能研究

利用自制的甲醛捕捉剂和酸性固化剂对脲醛树脂胶粘剂进行改性,并通过喷雾干燥工艺研制出环保型脲醛粉状树脂胶粘剂。还研究了不同物质的量比、缩聚阶段多次加料不同物质的量比、反应温度、甲醛捕捉剂等实验条件对脲醛树脂胶粘剂性能的影响。制备的脲醛树脂胶粘剂性能经测试达到了国家标准。     

Urea impregnated multiwalled carbon nanotubes; a formaldehyde scavenger for urea formaldehyde adhesives and medium density fiberboards bonded with them

Multiwalled carbon nanotubes (MWCNTs) were subjected to modification by urea to use as formaldehyde scavenger in urea formaldehyde (UF) adhesive and reducing the free formaldehyde emission of the medium density fiberboards (MDFs). Morphological differences besides elemental analysis was investigated using field emission scanning electron microscopy (FESEM) and energy dispersive X-ray spectroscopy. The effect of urea impregnated MWCNTs filler on the physical, morphological and thermal properties of the UF resin has investigated. Furthermore, characterization of the mechanical properties, free formaldehyde emission and thickness swelling were carried out for the MDF panels. From the results, the free formaldehyde of the UF resins was significantly decreased. The lowest free formaldehyde was belonged to the sample with 3 wt% of scavenger which was about 71% lower than the value for neat UF resin. Accordingly, the formaldehyde emission of the fiberboards was also showed a descending trend by incorporation of MWCNTs-U to the composite structure. It was decreased from 9.67 to 3.89 mg/100 g dried board. These results indicated that the prepared nano modifier was successfully performed as a formaldehyde scavenger for the UF resin and could prevent the hazards of the free formaldehyde emission from MDF panels.     

Interfacial factors affecting polymeric diphenylmethane diisocyanate/wood bond strength

Polymeric diphenylmethane diisocyanate (pMDI) has been used for making wood board composites for over 30 years, although its growth in application has been limited mainly by the perception that it is a high‐cost alternative to formaldehyde‐based adhesives. Increased use of pMDI adhesive in making wood composites will require optimization of the process variables involved. One such factor is the unresolved question of the interfacial aspects most responsible for building strong wood composites. Some argue that adhesive surface coverage is primarily responsible for board strength; others assert that penetration of the pMDI into the wood matrix is a primary characteristic of strong boards. This article will provide evidence that the interfacial aspect most important in building board strength is surface coverage of the wood particles or fibers. Experiments controlling the depth of pMDI penetration into wood matrices and then measuring their adherend strength were performed. We also calculated the potential efficiencies to be obtained from maximizing the surface coverage and minimizing the matrix penetration using a spherical sector model. Neither high nor low pMDI viscosity offered a significant advantage in surface covering pine or oak, although it is speculated that minimizing the droplet size of pMDI in the resination step could lead to substantial efficiency improvements in adhesive coverage. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 449–455, 2005     

Technological performance of formaldehyde-free adhesive alternatives for particleboard industry

Due to their high reactivity, chemical versatility and economic competitiveness, formaldehyde-based poly-condensation adhesives are used in huge amounts - in 2010 in the order of 20 million metric tons - around the globe, primarily in the wood-processing industry. Since the 1970s formaldehyde emissions from products made thereof came under pressure and were reduced continuously. The discussion intensified again initiated by the latest European CLP (classification, labelling and packaging) regulation, which came into force in 2016, classifying formaldehyde as a Carcinogen Category 1B compound. In view of potential and even stronger future restrictions of formaldehyde use, appropriate alternatives to substitute formaldehyde-based adhesive systems such as urea formaldehyde would have to be developed and implemented in the wood processing industry. The present review represents a critical appraisal of formaldehyde-free adhesive systems for particulate wood composites production proposed in literature so far. Adhesive systems analyzed here include both synthetic and renewable-based adhesives. The core of the review is an assessment of the individual adhesive systems based on selected technological (product and process) parameters relevant for wood-particleboard production. Based on this data we evaluated their potential to identify suitable alternative adhesives having a certain probability to meet the requirements of a large-scale processing industry sector. As an overall conclusion, there are still many challenges to overcome to replace formaldehyde. Except for pMDI-based systems, most of the alternative adhesives are considerably less reactive, which would result in dramatically higher production costs. Furthermore, the availability of most components proposed to produce alternative adhesives are currently not available in the necessary quantities. Moreover, toxicological investigations on alternative systems are still missing. As several components replacing formaldehyde are also toxic or hazardous to different extents, it cannot be guaranteed that the individual proposed alternative adhesives are safer during processing and service life compared to conventional systems. Due to the nature of the organic material wood, particleboards will always release a certain amount of formaldehyde, even when produced with formaldehyde-free adhesives.     

Properties of softwood polymer composites impregnated with nanoparticles and melamine formaldehyde furfuryl alcohol copolymer

Wood polymer composites (WPC) based on nano SiO₂ and nanoclay were prepared by the impregnation of melamine formaldehyde‐furfuryl alcohol copolymer, 1,3‐dimethylol 4,5‐dihydroxy ethylene urea, a crosslinking agent, and a renewable polymer. Surface modification of SiO₂ and formation of composites were characterized by Fourier Transform Infrared Spectroscopy (FTIR). X‐ray diffractometry (XRD) studies indicated a decrease in crystallinity of the composites. The crystallinity index value of wood cellulose decreased from 63.8 to 30.8 as determined from FTIR and XRD studies. Scanning Electron Microscopy was used for morphological characterization. Transmission Electron Microscopy (TEM) showed uniform distribution of nano SiO₂ and nanoclay in the composites. Remarkable reduction in water uptake capacity was observed for the treated wood samples. It was found to reduce from 142.2% to 30.2%. Both tensile and flexural properties increased upto 76.5% and 23.6%, respectively in the WPCs. An improvement in chemical resistance, flame retardancy and thermal stability were observed in the composites as a result of treatment. POLYM. ENG. SCI., 54:1019–1029, 2014. © 2013 Society of Plastics Engineers