MALDI-TOF study of oligomers distribution in spray-dried glyoxalated lignin for wood adhesives

Spray drying of glyoxalated lignin used in tannin/lignin adhesives for exterior- and interior-grade wood particleboard and other types of panels has been shown to be capable of maintaining its reactivity after spray drying with no decrease in performance of the adhesive once the spray-dried material is re-dissolved in water. This indicates that spray drying is a very suitable method for long-term storage of the adhesive without loss of performance. A clear variation in the distribution of oligomers in the material after spray drying has been observed by Matrix-Assisted Laser Desorption/Ionization Time of Flight analysis. One effect of the reaction that has been noticed with aging is the assembly of the monomers and lower molecular mass oligomers such as dimers into structures of higher molecular weight as a consequence of their condensation with glyoxal and the formation of glyoxylene bridges between them.     

黑液制胶合板用胶粘剂的研究

本研究用纸厂度黑液经发酵法处理后，取代部分苯酚制取碱木素酚醛树脂胶作胶合板用胶粘剂．不但部分解决了黑液的利用和污染问题，且增加了胶合板用胶种．文中介绍了胶制备工艺的研究，讨论了黑液中碱木素分子量及分布等对胶性能影响，同时与普通酚醛胶性能和成本作了比较等．     

Preparation and Characterization of Demethylated Lignin-Polyethylenimine Adhesives

Petrochemical-based adhesives such as urea-formaldehyde and phenol-formaldehyde resins are predominant wood adhesives. In this study, a new wood adhesive from lignin was developed and characterized. The new adhesive consisted of demethylated kraft lignin (DKL), a byproduct in the production of dimethyl sulfoxide from kraft lignin, and a polyethylenimine (PEI). Lap-shear specimens bonded with this new DKL-PEI adhesive system had very high shear strength and were very water-resistant. The effects of the preparation time, the curing conditions, the total solids content of the adhesive, the DKL/PEI weight ratio and the molecular weight of PEI on the shear strength and water-resistance of the resulting lap-shear specimens were studied in detail. Investigation on the curing chemistry of this new adhesive revealed that phenolic hydroxyl groups were oxidized to form quinones that further reacted with PEI. It was proposed that the curing mechanisms of this DKL-PEI adhesive were similar to the quinone-tanning processes in nature.     

Preparation and Characterization of Demethylated Lignin-Polyethylenimine Adhesives

Petrochemical-based adhesives such as urea-formaldehyde and phenol-formaldehyde resins are predominant wood adhesives. In this study, a new wood adhesive from lignin was developed and characterized. The new adhesive consisted of demethylated kraft lignin (DKL), a byproduct in the production of dimethyl sulfoxide from kraft lignin, and a polyethylenimine (PEI). Lap-shear specimens bonded with this new DKL-PEI adhesive system had very high shear strength and were very water-resistant. The effects of the preparation time, the curing conditions, the total solids content of the adhesive, the DKL/PEI weight ratio and the molecular weight of PEI on the shear strength and water-resistance of the resulting lap-shear specimens were studied in detail. Investigation on the curing chemistry of this new adhesive revealed that phenolic hydroxyl groups were oxidized to form quinones that further reacted with PEI. It was proposed that the curing mechanisms of this DKL-PEI adhesive were similar to the quinone-tanning processes in nature.     

新型镀铝复合薄膜专用胶粘剂的研究

分析了影响BOPP／VMCPP型镀铝复合薄膜剥离强度的主要因素,即：BOPP和胶粘剂的界面强度;胶粘剂和VM的界面强度;VM和CPP的界面强度,以及胶粘剂的组成、分子结构、相对分子质量分布、单体残存量等,并合成了一种新型的镀铝膜和塑料薄膜复合用聚氨酯胶粘剂;讨论了胶粘剂的相对分子质量、相对分子质量分布、固化温度和时间等因素对粘结性能的影响。试验结果表明：该胶粘剂初粘力强、剥离强度高、溶剂残留量低,适用于快速复合薄膜生产线。     

Chromatographic Analysis of the Reaction of Soy Flour with Formaldehyde and Phenol for Wood Adhesives

The desire to make more biobased and lower-cost bonded wood products has led to an interest in replacing some phenol and formaldehyde in wood adhesives with soybean flour. Improved knowledge of the soy protein properties is needed to relate resin chemistry to resin performance before and after wood bonding. To expose the soy protein’s functional groups, it needs to be disrupted, with minimal hydrolysis, to maximize its incorporation into the final polymerized adhesive lattice. The best conditions for alkali soy protein disruption were to maintain the temperature below 100 °C and react the soy flour with sodium hydroxide at pH 9–12 for about 1 hour. A gel permeation chromatography procedure was optimized to determine conditions for selectively breaking down the high molecular weight soy protein fragments that contribute to high adhesive viscosity. This method and extraction data were used to evaluate the reaction of the disrupted soy flour protein with formaldehyde and phenol to provide a stable adhesive. The results were used to develop more economical adhesives that are ideally suited for the face section of oriented strandboard.     

Mussel adhesive protein as an environmentally-friendly harmless wood furniture adhesive

Recent adhesive technologies have focused on the development of high-quality and eco-friendly adhesives. Thus, there is a gradual shift from the currently used chemical-based adhesives toward harmless adhesives with improved quality and performance. Here, we evaluated the potential use of bacteria-produced recombinant mussel adhesive protein (MAP) as a harmless wood furniture adhesive. We formulated a MAP wood adhesive as an inclusion body type for economical preparation, and we confirmed its harmlessness through the non-detection of volatile organic compounds and heavy metals. The formulated MAP showed sufficiently strong bulk adhesive strength for the dried gluing of wood adherends. We also found that the formulated MAP wood adhesive exhibits robust adhesion in various environmental conditions, including open assembly times, incubation times, temperatures, and humidity levels. In summary, the developed recombinant MAP could be successfully used as a promising environmentally-friendly, harmless wood furniture adhesive.     

分子量对压敏胶粘接性能的影响

本文综述了分子量及其分布与压敏胶粘接性能的关系，通常粘接性能随分子量的增大而提高。当压敏胶保持足够高的分子量和较宽的分子量分布时，才能获得综合性能较好的压敏胶     

木工用氯丁橡胶胶粘剂的制备与性能研究

考查了萜烯-酚醛树脂、轻质碳酸钙、乙酸乙酯与120°溶剂油混合溶剂及其组成对木工用氯丁橡胶胶粘剂性能的影响。研究得出木工用氯丁橡胶胶粘剂的最佳配方（质量份）为：氯丁橡胶100、萜烯-酚醛树脂40、轻质碳酸钙20、由乙酸乙酯与120°溶剂油质量比67：33组成的混合溶剂550,其各项性能指标均能达到行业标准LY／T1206-2008“木工用氯丁橡胶胶粘剂”的要求。     

L型热熔胶的研制

研制的SG010-C和SG010-X型催化剂对H2敏感性好,可用于乙烯均(共)聚制备L型热熔胶。在聚合过程中,通过改变催化剂的结构和氢调,控制聚合物的熔体指数(MI)、相对分子质量分布、颗粒度和熔点等,可一步法生产出热熔胶粉末且不必进行粉碎分级。     

木焦油部分替代苯酚合成酚醛树脂胶粘剂的研究

采用简单蒸馏法，获得木焦油中150-250℃的馏分；采用气质联用仪（GC—MS）对此馏分的成分进行了分析，确定了37种化合物，其中酚类化合物的相对含量为40％，占总体木焦油的11％以上、用木焦油部分替代苯酚合成酚醛树脂胶粘剂，同时采用一次投甲醛法，对焦油替代量、反应温度、反应时间、催化剂含量等工艺参数进行了正交化试验，确定了最佳工艺条件？制得的酚醛胶的性能符合GB／T14074—2006的要求，胶合强度高达308MPa。采用木焦油的部分替代苯酚，降低了酚醛树脂胶粘剂的成本，也为木焦油的利用提供了一条途径，因此具有良好的工业前景与环境效益     

Effects of wood-surface roughness,adhesive viscosity and processing pressure on adhesion strength of protein adhesive

The objective of this research was to study the effects of wood-surface roughness, adhesive viscosity and processing pressure on adhesion strength between soybean protein adhesive and wood, and to seek the relative importance of the individual factors in determining adhesion strength. Processing pressure was found to be the most important factor in determining adhesion strength. An optimum pressure, which was about 4.55 MPa in this research, is needed for development of a strong bond. A higher pressure resulted in reduced adhesion strength, possibly due to damage to the wood surface; a lower pressure also resulted in decreased adhesion strength because of the lack of bond formation. Adhesive viscosity had greater effect on adhesion strength than surface roughness. Contact angle, which was found to be mainly determined by adhesive viscosity and surface roughness, was a major factor controlling adhesive penetration. A smaller contact angle, resulting from lower viscosity and rougher surface, produced deeper penetration, while a larger contact angle, resulting from higher viscosity and smoother surface, produced shallower penetration. An optimum penetration is needed to enhance adhesion strength by developing a three-dimensional interactive zone at the interface. Too deep or too much penetration would result in 'dry-out' at the interface; less penetration would limit the formation of the three-dimensional zone at the interface. Both cases resulted in reduced adhesion strength. Contact angles ranging from 35 to 47° provided the optimum penetration needed for good adhesion. The results of this research could be used as reference to determine optimum process parameters in plywood manufacturing when an aqueous based adhesive is used.     

环保耐水型木材用胶粘剂的研究

以过硫酸铵为引发剂制备低相对分子质量的聚丙烯酰胺,以次氯酸钠(NaClO)为氧化剂对淀粉进行氧化处理,然后将两者进行缩合反应得到聚丙烯酰胺接枝淀粉胶粘剂的主剂;最后以2-甲基氮丙啶为交联剂制备了环保耐水型木材用胶粘剂。采用傅里叶红外光谱(FT-IR)法和X射线衍射(XRD)法对中间体和胶粘剂进行了表征。实验结果表明,当w(交联剂)=3%(为淀粉胶主剂干胶的质量分数)、交联时间为3 h和w(丙烯酰胺)=7.5%(相对于淀粉的质量分数)时,制得胶粘剂的胶合强度达到5.30 MPa,耐水时间达33 h。     

Phenolic resol resin adhesives prepared from alkali-catalyzed liquefied phenolated wood and used to bond hardwood

Wood-based resol resins were prepared from both water- and sodium hydroxide (NaOH)-catalyzed liquefied phenolated wood. The effects of various reaction parameters, e.g. the concentrations of phenol and formaldehyde, temperature, and time, on the extent of yield, free phenol content, molecular weight as well as the gluability of the resol resins have been evaluated. As far as the yield, free phenol content, and molecular weight are concerned, the optimum conditions of resol resin preparation were found to be a phenol : wood weight ratio of 4 : 6, a formaldehyde : phenol mole ratio of 1.5 : 1, a temperature of 82.5°C, and time 3 h. However, these optimum conditions changed when the performance of the adhesives was considered in terms of the adhesive bond strengths for plywood joints. The yield, molecular weights, polydispersity, and gluability of resol resins prepared from water-catalyzed liquefied wood were lower compared with those prepared from NaOH-catalyzed ones. In most cases, the dry-bond strengths of the experimental plywood joints exceeded the minimum Japan Agricultural Standard (JAS) values. On the other hand, except at a higher formaldehyde: phenol ratio (i.e. 2.0 : 1 mole ratio), the plywood joints of all samples delaminated during 'boil-dry-boil' cyclic treatments. However, both dry- and wet-bond strengths of the plywood joints could be improved to exceed standard values by using an additional crosslinking agent, e.g. poly(methylene (polyphenyl isocyanate)) (polymeric MDI). The adhesive perfomance of the wood-based resol resins was explained on the basis of the adhesion between wood veneers and resol resin adhesives.     

Effects of sucrose fatty acid ester addition on the structural,rheological and retrogradation behavior of high amylose starch-based wood adhesive

In this study, sucrose fatty acid ester (SE) was used to evaluate the characteristics of a high amylose starch-based wood adhesive. Fourier transform infrared (FT-IR) spectroscopy confirmed the occurrence of graft copolymerization reactions whereas X-rays diffraction (XRD) analysis verified the presence of amylose-SE complexes. Scanning electron microscopy (SEM) a revealed uniform distribution of spaces whereas transmission electron microscopy (TEM) showed good dispersion of latex particles with SE addition as evident by small and poly-dispersed particles in the wood adhesive. The water dynamics in the starch adhesive system was studied using low-field nuclear magnetic resonance (LF-NMR). Furthermore, the addition of SEs resulted in enhanced shear-thinning and solid like-behaviors and anti-retrogradation properties of the adhesive with incorporation of SE. These results showed that SEs could improve the rheological and anti-retrogradation properties of the wood adhesive and offers a major step forward to prepare bio-based adhesives as an alternative for petroleum-based wood adhesives.     

Effects of Adhesive Application Methods on Performance of a Soy-based Adhesive in Oriented Strandboard

A wet method and dry method of applying a soy flour (SF)–curing agent (CA) adhesive onto wood flakes were evaluated for making randomly oriented strandboard (R-OSB) and OSB. The wet method involved the thorough mixing of SF and CA prior to spraying the SF–CA mixture onto wood flakes. SF:CA weight ratio, adhesive add-on rate, hot-press conditions were optimized for enhancing internal bond strength (IB), modulus of rupture (MOR), and modulus of elasticity(MOE) of the resulting R-OSB. The highest IB, MOR and MOE were obtained at the 1:1 SF:CA weight ratio. IB, MOR and MOE of R-OSB exceeded the minimum industrial requirements at a ≥7% adhesive add-on rate, a hot-press temperature in the 170–220 °C range, and a ≥4 min hot-press time. The dry method involved spraying aqueous CA solution onto a mixture of SF and wood flakes. The dry method allowed the strengths of the resulting R-OSB to exceed the minimum industrial requirements at a higher SF:CA ratio (up to 7:1). The dry method was superior to the wet method because a higher SF:CA ratio meant a lower adhesive cost. OSBs made with the SF–CA adhesive had strengths higher than or comparable to commercial OSBs.     

集成材拼接胶粘剂的研制

本文采用接枝共聚改性聚醋酸乙烯乳液和制备异氰酸酯预聚体生产出集成材工业用拼接胶粘剂。对该胶的耐水剥离率、压缩剪切强度、木破率及施工工艺性能等方面进行了研究，并达到了同类进口胶的水平。     

单组分湿固化木材用聚氨酯胶黏剂研究

采用聚醚多元醇、聚合二苯基甲烷二异氰酸酯(PAPI)为主要原料制备了木材用单组分湿固化聚氨酯胶黏剂。研究了-NCO含量、聚醚多元醇相对分子质量、反应温度及扩链系数对木材粘接性能的影响。结果表明:在-NCO质量分数为12.29%,扩链系数为0.2时,粘接性能最好,24 h后压缩剪切强度可达20.17MPa。     

An ATR-FTIR study on penetration of resins in wood

Wood samples were treated with allylic ether resins having various molecular weights, various structures and with the use of different solvents. Using a technique based on Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR), differences in the characteristic bands of wood and resin were monitored throughout a piece of wood treated with resins and thus a penetration profile was demonstrated. ATR-FTIR showed that there were differences in the chemical composition of the wood itself at different depths from the surface. The resins could be detected at a depth of more than 3 mm into the wood after 4 days of penetration by gravity. Using a characteristic band for wood as an internal standard, it could be demonstrated that penetration depends upon the solvent used, molecular weight of the resin and also morphology of the wood.     

我国木材工业用胶粘剂的现状、存在问题及对策

本文介绍了脲醛树脂胶粘剂、酚醛树脂胶粘剂、三聚氰胺甲醛树脂胶粘剂、聚醋酸乙烯乳液胶粘剂、聚氨酯胶粘剂、热熔胶粘剂等木材工业用胶粘剂的现状和研究进展。分析了目前木材工业用胶粘剂存在的问题,初步提出了解决问题的对策。