木质素及其衍生物在木材胶黏剂中应用研究进展

以天然可再生资源替代传统化石资源开发绿色环保、性能优异的木材胶黏剂是人造板行业研究的热点。木质素来源广泛、价格低廉,且分子结构中含有羟基、甲氧基、羧基等活性基团,易于功能化修饰,是合成木材胶黏剂的理想原料。本文重点综述了木质素及其衍生物在酚醛树脂、脲醛树脂、环氧树脂、聚氨酯等合成树脂木材胶黏剂中的应用与研究现状,介绍了化学改性、降解、溶剂分级纯化等预处理方式对木质素化学反应活性及合成树脂胶黏剂力学性能的影响,探讨了木质素基木材胶黏剂目前发展面临的困难和挑战,并展望了未来应用及研究方向,以期为木质素资源的高效、高值化综合利用及高性能生物基木材胶黏剂的开发提供理论与技术参考。     

木材工业胶黏剂的应用及发展趋势

随着木材工业的不断发展,木材工业胶黏剂的应用范围也在不停地扩增,种类日趋增加.阐述木材工业胶黏剂的起源,并对各种胶黏剂类型及其应用做出了大概的分析,总结了各类木材胶黏剂的优缺点并提出了相应的改进方案.根据相关行业的要求,对木材工业胶粘剂的发展趋势进行了相应的预测,期望能够为其使用和发展提供借鉴.     

双组分交联型丙烯酸酯胶黏剂的研制

采用溶液聚合的方法,以丙烯酸羟乙酯、乙酸乙烯酯、丙烯酸和丙烯酸异辛酯的混合单体及聚氨酯101-乙组分为原料,合成了双组分溶液型丙烯酸酯胶黏剂.并讨论了单体组成以及单体中丙烯酸羟乙酯与固化剂的比例大小等因素对胶黏剂性能的影响.结果表明:当丙烯酸羟乙酯为18g,丙烯酸羟乙酯与固化剂比例为1:3时性能最优;单纯增加组分中的羟乙酯成分对体系交联程度和体系性能影响不大;羟乙酯如果同固化剂共同作用,胶黏剂性能可以得到明显提高.     

葛根淀粉基胶黏剂制备与性能研究

研究开发以淀粉为主要原料的环保型胶黏剂替代"三醛类"木材胶黏剂,对彻底解决人造板及其制品的甲醛释放问题具有重要意义。以野生葛根淀粉为原料,通过降黏处理,并与聚醋酸乙烯酯和异氰酸酯复配,制备出胶合强度达到国家Ⅱ类要求的淀粉基木材胶黏剂。研究了降黏剂用量、降黏时间、聚醋酸乙烯酯和异氰酸酯用量对淀粉基木材胶黏剂胶合强度的影响。优化工艺条件下制备胶黏剂胶接胶合板的胶合强度为1.89 MPa,能够满足国家Ⅱ类胶合板强度要求。     

含环氧基和丙烯酰氧基有机硅增黏剂的制备及应用

以硅烷偶联剂为原料制备出3种加成型液体硅橡胶(ALSR)增黏剂,对比考察了这三种增黏剂对塑料及金属基材黏结效果和力学性能的影响。结果发现,含环氧基或含丙烯酰氧基的单一基团增黏剂对ALSR有一定的增黏作用,而由这两种基团制成的复合型增黏剂具有更加优良的黏结效果。三种增黏剂均可以促进ALSR的硫化,且在一定程度上提高了硫化胶的力学性能。当复合型增黏剂用量为0.8份(质量)时,硅橡胶与铝材之间的剥离强度及硫化胶的拉伸强度分别达到4.3 kN/m和5.23 MPa,与未添加增黏剂的硅橡胶相比,剥离强度提高了约40倍。复合型增黏剂对ALSR的综合改善效果要优于单一极性基团增黏剂。     

双组分无溶剂聚氨酯胶黏剂的制备及性能研究

以聚醚多元醇和二苯基甲烷二异氰酸酯为原料,通过聚合反应制得双组分无溶剂聚氨酯胶黏剂的A组分;分别以蓖麻油、聚醚多元醇、聚酯多元醇、蓖麻油改性的聚酯多元醇作B组分。将A、B组分混合,涂布于复合膜之间,经熟化反应,制得双组分无溶剂聚氨酯胶黏剂。系统研究了A组分中的异氰酸酯基含量、B组分多元醇种类对胶黏剂的黏结强度和耐水煮性能的影响。结果表明：当A组分异氰酸酯基质量分数为17%时,胶黏剂的剥离强度最大;采用蓖麻油改性的聚酯多元醇作B组分时,胶黏剂黏结性能优异,经沸水煮3 h后,其剥离强度维持在3.7×15^-1N/mm,展现出优异的耐水煮性能。     

淀粉胶黏剂的最新研究进展

淀粉胶黏剂作为环境友好型天然胶黏剂越来越受到研究人员的广泛关注,淀粉以其资源丰富、价格低廉、使用方便等优点并以无毒环保为亮点,成为最具有开发潜力的木材用天然胶黏剂之一。综述了淀粉胶黏剂用于木材粘接的最新动态,详述了它在应用中存在的局限性和研究现状,并对淀粉胶黏剂的发展趋势进行了展望。同时还指出在提高淀粉胶黏剂的耐水性、贮存稳定性、防潮防霉性能方面仍有很大的发展空间,因而广大学者致力于淀粉胶黏剂的进一步开发研究。     

快干型聚四氟乙烯用复合胶黏剂的研制

将环氧树脂胶黏剂作为组分A、有机硅树脂胶黏剂作为组分B,两种组分复配后得到一种快干型复合胶黏剂,将其应用于聚四氟乙烯材质的黏结。对影响复合胶黏剂反应时间、力学性能、固化速率的因素进行探讨,并对该复合胶黏剂进行红外表征。结果表明:与单一型环氧树脂胶黏剂相比,复合胶黏剂的力学性能明显提高,固化速率也有一定程度提升。     

水相中合成木质素环氧树脂及其在木材胶黏剂中的应用

以木质素为原料,在水相中合成一种适用于木材胶黏剂的木质素环氧树脂。为了考察木质素环氧化反应条件对木质素环氧树脂的羟基和环氧基的影响,以及对胶合板的胶合强度的影响,采用FT-IR和31PNMR对木质素环氧树脂结构进行表征,并用TG和DTG对木质素环氧树脂的热稳定性进行分析。结果表明,环氧化反应主要发生在酚羟基上,在反应过程中,相比环氧氯丙烷,NaOH的加入量对木质素环氧树脂结构和胶合板的胶合强度影响更大。随NaOH加入量增加,木质素环氧树脂中环氧基团逐渐增多,胶合板的胶合强度呈现先升高、后降低的趋势。当木质素的羟基与NaOH摩尔比为1:1时,由木质素环氧树脂制得的胶合板胶合强度达到最大,湿强度达1.61 MPa,超过国家标准II类板的要求(≥0.7 MPa)。采用扫描电镜研究了黏接机理,发现环氧化程度提高时,固化后的木质素环氧树脂的结构更加稳定且致密,导致胶合板的胶合强度也提高。但过高的环氧化程度会增大胶黏剂的粒径,导致胶黏剂与木板不能形成更好的机械互锁结构,从而降低胶合板的胶合强度。还进一步简化了木质素环氧树脂木材胶黏剂的合成工艺,使环氧化反应后的体系无需处理即可直接应用于木材胶黏剂,减少了胶合板生产工艺流程。此外,经过30天的储存期,胶黏剂黏合强度没有明显下降。通过与商业脲醛树脂木材胶黏剂对比,其黏接强度可以达到商业脲醛树脂的水平。     

高温致活工业明胶木材胶黏剂的制备及应用

以废弃皮革中提取的工业明胶为原料,甲乙酮肟制备的封闭型水性聚氨酯为交联剂,通过在高温热压条件下解封出活性异氰酸酯基团,使其与明胶产生交联,合成出高温致活封闭型工业明胶木材胶黏剂。FTIR和DSC结果表明,甲乙酮肟分子上的羟基与聚氨酯预聚体上的异氰酸酯基团发生缩聚反应,其最大解封温度约126℃。SEM结果显示,胶黏剂经高温固化后表面更为光滑,说明明胶与封闭型水性聚氨酯组分间的相容性得到了提高。应用测试结果表明,当封闭型水性聚氨酯占明胶水溶液质量的20%时,胶黏剂的湿剪切强度高达0.97MPa,满足国家Ⅱ类胶合板的使用要求,且最佳的热压工艺条件是热压温度150℃、热压时间4min、涂胶量300 g/m2。     

Investigation of Adhesion Performance of Aqueous Polymer Latex Modified by Polymeric Methylene Diisocyanate

Aqueous polymer isocyanate (API), which has good adhesive properties at ambient temperature and excellent resistance to warm/boiling water, and is friendly to the environment, is widely used in the timber-processing industry. To prepare high performance API, vinyl acetate homopolymer and copolymer emulsion were respectively cross-linked by three types of polymeric methylene diisocyanate (p-MDI). The potlife, curing time, bonding strength, and water resistance of API adhesives were tested with different cross-linkers and varying loadings (5–20%). Also the effect of polyvinyl alcohol (PVOH) content of aqueous vinyl latex on the performance of API was investigated. It was shown that the potlife and curing time of API were obviously influenced by the types of cross-linker and its loading. Correct loadings of p-MDI as crosslinker can remarkably improve the adhesive performance of aqueous polymer emulsion at ambient temperature. Excess cross-linker cannot maintain such an effect of strengthening and may decrease considerably the bond properties of API. The warm- and boiling-water resistance of API improved markedly with increasing cross-linker loading, where emulsifiable isocyanate gave better cross-linking performance, and p-MDI mixed with organic solvent was the secondbest. With the increase of PVOH content, the curing time of API increased, but no statistically apparent differences in the potlife of API were found. The bonding performance of API was improved as PVOH content increases, but excess PVOH also weakenes the warm- and boiling-water resistance of the joint.     

环保型木材复合用胶黏剂的研制

环境污染问题,现已受到人们的高度重视,像木材复合板中甲醛释放量严重超标,污染严重,给人们身体健康带来很大的危害。针对这一情况,我们研制出相应的绿色环保型胶黏剂,文章中介绍了木材复合板用胶黏剂的合成方法,讨论了原料配比,反应温度,A组分与B组分对胶黏剂性能的影响,本研制出胶黏剂由于不含甲醛等有害气体,性能优于现有乙烯和醋酸乙烯共聚乳液和聚醋酸乙烯乳液,因此在木材复合板加工工业中市场前景广阔。     

Investigation of Adhesion Performance of Aqueous Polymer Latex Modified by Polymeric Methylene Diisocyanate

Aqueous polymer isocyanate (API), which has good adhesive properties at ambient temperature and excellent resistance to warm/boiling water, and is friendly to the environment, is widely used in the timber-processing industry. To prepare high performance API, vinyl acetate homopolymer and copolymer emulsion were respectively cross-linked by three types of polymeric methylene diisocyanate (p-MDI). The potlife, curing time, bonding strength, and water resistance of API adhesives were tested with different cross-linkers and varying loadings (5-20%). Also the effect of polyvinyl alcohol (PVOH) content of aqueous vinyl latex on the performance of API was investigated. It was shown that the potlife and curing time of API were obviously influenced by the types of cross-linker and its loading. Correct loadings of p-MDI as crosslinker can remarkably improve the adhesive performance of aqueous polymer emulsion at ambient temperature. Excess cross-linker cannot maintain such an effect of strengthening and may decrease considerably the bond properties of API. The warm- and boiling-water resistance of API improved markedly with increasing cross-linker loading, where emulsifiable isocyanate gave better cross-linking performance, and p-MDI mixed with organic solvent was the secondbest. With the increase of PVOH content, the curing time of API increased, but no statistically apparent differences in the potlife of API were found. The bonding performance of API was improved as PVOH content increases, but excess PVOH also weakenes the warm- and boiling-water resistance of the joint.     

淀粉在木材胶粘剂中的应用

介绍了淀粉在木材胶粘剂中的应用,主要论述了淀粉作为改性剂可以有效地改善脲醛树脂胶的预压及胶合性能,可以加快聚醋酸乙烯酯的固化速度及提高耐水性。以淀粉为原料合成木材用胶粘剂主要通过加入异氰酸酯、三聚氰胺和苯酚衍生物改性或将淀粉氧化成双醛淀粉通过缩聚改性。     

改性聚醋酸乙烯乳液拼板胶的研制

研究了甲苯二异氰酸酯 -三羟甲基丙烷加成物及其用量对聚醋酸乙烯乳液拼板胶粘合性能的影响。     

单组分聚醋酸乙烯D3级木工胶的研究

以乙二醛改性PVA(聚乙烯醇)为保护胶体、VAE(乙烯-醋酸乙烯共聚物)乳液为种子乳液和VoeVa10(叔碳酸乙烯酯)为共聚单体,采用种子乳液聚合法和酮肼(DAAM/ADH)交联体系合成了改性PVAc(聚醋酸乙烯)胶粘剂。研究结果表明:当乙二醛改性PVA的缩醛度为15%、m(VoeVa10)∶m(VAc)=10∶100、w(VAE)=10%(相对于乳液总质量而言)和m(ADH)∶m(DAAM)=(0.5～1.5)∶1时,制成的单组分环保型改性PVAc乳液胶粘剂具有良好的耐水性和粘接强度,完全满足欧洲DIN EN 204—1991 D3级木工胶的标准要求。     

淀粉基木材胶黏剂的制备与性能

以玉米淀粉为接枝骨架,过硫酸铵为引发剂,与接枝单体乙酸乙烯酯-丙烯酸丁酯进行接枝共聚反应,制取淀粉基木材胶黏剂。对得到的淀粉接枝共聚物进行了表征分析及性能研究。IR谱图表明,样品除了保持淀粉的特征吸收峰外,在1730—1740cm。之间出现了羰基特征吸收峰。X-粉末衍射图表明,样品多为弥散峰,证明淀粉接枝共聚物基本为少量结晶态与无定形态共存的结构。TG、DTA曲线证实了接枝共聚反应的发生,且淀粉接枝共聚物的热稳定性优于纯玉米淀粉。性能测试结果表明,制备的胶黏剂具有较好的高温稳定性、粘接性,各项指标已达到了国家标准HG／T2727—95中聚乙酸乙烯酯木材胶黏剂的性能指标,特别是压缩剪切干强度远远超过了国家标准。     

丙烯酸酯改性PVAc乳液胶粘剂及其热性能研究

以丙烯酸丁酯(BA)和丙烯酸(AA)作为醋酸乙烯酯(VAc)的改性共聚单体,采用半连续种子乳液聚合法制备改性聚醋酸乙烯酯(PVAc)乳液,并以此作为木材胶粘剂。研究结果表明:以粘接强度、吸水率和黏度为考核指标,采用单因素试验法优选出改性乳液的最佳单体配比为w(BA)=15%、w(AA)=3%(均相对于VAc质量而言);改性乳液的平均粒径为200⁴00 nm,粒径分布较均一;引入BA和AA后,改性乳液的Tg(玻璃化转变温度)变化较明显,改性胶膜的热稳定性随改性单体含量增加而略有增大,当w(BA)≥5%、w(AA)≥1%时,改性胶膜的起始热分解温度比VAc均聚物提高了60℃左右。     

Effect of citric acid,PVOH, and starch ratio on the properties of cross-linked poly(vinyl alcohol)/starch adhesives

The properties of tapioca starch adhesives were improved by cross-linking and the cross-linked adhesive compared with pure tapioca starch and poly(vinyl alcohol) adhesives. The effect of starch ratio, type of PVOH, and adding citric acid were important factors on the cross-linked adhesives. Wood adhesives made from cross-linked PVOH/starch were prepared by PVOH and tapioca starch, using hexamethoxymethyl melamine (HMMM) and citric acid (CA) as a cross-linking agent and catalyst, respectively. The effect of CA, PVOH/starch ratio, and type of PVOH such as medium (M PVOH) and high molecular weight (H PVOH) were investigated. The condition of the cross-linking reaction was 175?°C for 15?min. The structural properties of cross-linked adhesive were investigated by FT-IR spectroscopy. The results were confirmed in terms of thermal properties with a differential scanning calorimeter (DSC) and the shear strength of the adhesive. The cross-linked adhesive resulted in the increase of T _g and showed good blend compatibility with all of the cross-linked adhesives. The adhesive strength significantly increased when using CA as a catalyst in the cross-linking reaction. The optimum contents of the cross-linked PVOH/starch adhesives were 1:1.8 for M PVOH and 1:0.5 for H PVOH.