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低游离甲醛含量脲醛树脂胶粘剂的合成工艺研究 总被引:8,自引:4,他引:4
研究了在弱酸-弱碱-弱酸条件下,加入改性剂合成脲醛(UF)树脂胶的工艺过程。实验结果表明,甲醛与尿素的配比[即n(F)/n(U)比值]、体系pH值、尿素的加料方式和改性剂对UF树脂胶中游离甲醛的含量和胶合强度有很大的影响;当n(F)/n(U)=1.06、缩聚反应阶段体系的pH值为4.75~4.80、尿素分3批加入、反应温度为90℃、加入适量的聚乙烯醇(PVA)和三聚氰胺改性剂时,制得的UF树脂胶中游离甲醛的含量不大于0.10%(符合GB/T14 074.16-1993标准中的指标要求)、粘接强度为4.70 MPa且综合性能优良。 相似文献
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探讨了改性剂对降低游离甲醛含量、改善胶粘剂性能的作用机理,研究了三聚氰胺、聚乙烯醇(PVA)改性脲醛树脂胶粘剂(UF胶)的制备工艺和配方,实验得出:采用弱碱-弱酸-弱碱的工艺,添加适量三聚氰胺和聚乙烯醇,反应最高温度控制在90℃,反应时间2~3 h,n(尿素)∶n(甲醛)=1∶1.4,尿素按7.0∶2.0∶1.0的质量比分3次投料,可制得低毒脲醛树脂胶粘剂。 相似文献
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以硫代硫酸钠和M(三聚氰胺)作为复合改性剂,F(甲醛)和U(尿素)作为主要原料,采用弱酸-弱碱-弱酸-弱碱法合成了改性UF(脲醛树脂),并着重探讨了不同因素对UF中的游离F含量、胶合板的胶接强度及F释放量的影响。研究结果表明:合成改性UF的最佳工艺条件是反应温度为85℃,n(F)∶n(U)=1.10∶1,起始pH为5.0,M第2批加入,硫代硫酸钠第4批加入且加入量为U总质量的2%,U分批加入比例为55%、20%、15%和10%;此时UF中的游离F含量(降至0.11%)符合GB/T 14732—2006标准中的指标要求,胶合板的胶接强度(为1.05 MPa)满足国家标准中II类胶合板的指标要求、F释放量(为1.26 mg/L)达到普通胶合板通用技术条件中的E1级指标且耐水性也明显提高。 相似文献
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《中国胶粘剂》2016,(4)
选用弱酸-弱碱-弱酸-弱碱工艺制备脲醛树脂(UF)胶粘剂,研究了n[甲醛(F)]∶n[尿素(U)]、初始p H、反应温度和三聚氰胺(M)掺量对游离F含量和胶接强度的影响。研究结果表明:当n(F)∶n(U)=1.2∶1.0、起始p H为6.5、反应温度为85℃和w(M)=6%(相对于U总质量而言)时,UF胶粘剂的游离F含量(0.17%)符合国家标准要求(≤0.3%),胶合板的F释放量(1.17 mg/L)达到GB/T 9846.3—2004标准中E1级指标要求(≤1.5 mg/L),胶接强度(从0.46 MPa提高到0.97 MPa)达到了国家标准中II类胶合板的指标要求,耐水性也明显提高。 相似文献
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低游离甲醛脲醛树脂合成工艺研究 总被引:1,自引:0,他引:1
脲醛(UF)树脂是一种广泛应用于木材加工业的胶黏剂,文章采用碱-酸-碱合成工艺,探讨了甲醛与尿素的摩尔比、pH、反应温度及尿素加料方式等因素对UF树脂黏度及游离甲醛含量的影响,发展了制备低毒(游离甲醛含量0.13%)UF树脂的新工艺,并用IR对UF树脂进行了确证。 相似文献
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以一元碱Na OH(氢氧化钠)、二元碱Ca(OH)_2(氢氧化钙)、有机碱(HO—CH_2—CH_2)_3—N(三乙醇胺)和强碱弱酸盐Na_2SO_3(亚硫酸钠)作为不同的催化剂,采用碱-酸-碱法合成了UF(脲醛树脂)胶粘剂,并着重探讨了不同催化剂对UF胶粘剂游离甲醛含量、粘接强度、固化时间及固含量等影响。研究结果表明:以Ca(OH)_2为催化剂、M(三聚氰胺)为改性剂,所得UF胶粘剂的游离甲醛含量和粘接强度均达到了国家标准要求,而胶合板的甲醛释放量达到E_2级指标、耐水性明显改善。 相似文献
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环保型脲醛树脂粘合剂合成的研究 总被引:1,自引:0,他引:1
脲醛树脂是广泛用于木材工业中一种重要的胶粘剂。对降低脲醛树脂粘合剂中游离甲醛含量的措施以及改性方法进行了探讨,并在大量的实验基础上摸索出了一套简单实用的合成工艺,根据此合成方法生产的产品具有粘度好、反应条件易控制、甲醛含量低和成本低等优点,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(GB18 587-2001)。 相似文献
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D. Bertomeu D. García‐Sanoguera O. Fenollar T. Boronat R. Balart 《Polymer Composites》2012,33(5):683-692
In the last years, some high renewable content epoxy resins, derived from vegetable oils, have been developed at industrial level and are now commercially available; these can compete with petroleum‐based resins as thermoset matrices for composite materials. Nevertheless, due to the relatively high cost in comparison to petroleum‐based resins, their use is still restricted to applications with relatively low volume consumption such as model making, tuning components, nautical parts, special effects, outdoor sculptures, etc. in which, the use of composite laminates with carbon, aramid and, mainly, glass fibers is generalized by using hand layup and vacuum assisted resin transfer molding (VARTM) techniques due to low manufacturing costs and easy implementation. In this work, we study the behavior of two high renewable content epoxy resins derived from vegetable oils as potential substitutes of petroleum‐based epoxies in composite laminates with flax reinforcements by using the VARTM technique. The curing behavior of the different epoxy resins is compared in terms of the gel point and exothermicity profile by differential scanning calorimetry (DSC). In addition, overall performance of flax‐epoxy composites is compared with standardized mechanical (tensile, flexural and impact) and thermal (Vicat softening temperature, heat deflection temperature, thermo‐mechanical analysis) tests. The curing DSC profiles of the two eco‐friendly epoxy resins are similar to a conventional epoxy resin. They can be easily handled and processed by conventional VARTM process thus leading to composite laminates with flax with balanced mechanical and thermal properties, similar or even higher to a multipurpose epoxy resin. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers 相似文献
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M. Hart G. Fuller D.R. Brown C. Park M.A. Keane J.A. Dale C.M. Fougret R.W. Cockman 《Catalysis Letters》2001,72(3-4):135-139
A series of macroporous sulfonated poly(styrene-co-divinylbenzene) ion-exchange resins with varying levels of sulfonation have been prepared. The acidities of these resins have been measured calorimetrically by ammonia sorption. Catalytic activities have been measured in two liquid-phase reactions: the dehydration of 1-hexanol under flow conditions and the hydration of propene as a batch process. The molar enthalpies of ammonia sorption show that the strength of the acid sites increases as the level of sulfonation is increased; catalytic activities follow the same trend. The most active resins are those that have been sulfonated at levels above one sulfonic acid group per aromatic ring (persulfonated). These persulfonated resins also show higher thermal stabilities than conventional resins (sulfonated at just below one acid group per aromatic ring). 相似文献
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Chenyu Han Zhengmei Luo Xinlong Su Yanhua Chen Zhaojin Yang An Mao Hong Lei Xiaojian Zhou Hui Wan Guanben Du 《应用聚合物科学杂志》2023,140(4):e53378
Based on the difference in the reaction rate of different groups of urea-formaldehyde resins and isocyanate resins, this study designed two different urea-formaldehyde resins: a normal urea-formaldehyde resin (UF) and one with high mono-hydroxymethylurea content (UF*) to react with polymeric methylene diphenyl diisocyanate (pMDI) resin. The difference in mono- and di-hydroxymethyl urea content between UF and UF* resins was analyzed by nuclear magnetic resonance (NMR) spectroscopy, and results showed that the mono-hydroxymethyl urea content of the UF* resin was much higher than that of the conventional UF resin. The fourier transform infrared spectrometer (FTIR) analysis of differences between UF* and UF resin showed that the UF* process did not change the main structure of the conventional urea formaldehyde resin. Differential scanning calorimeter (DSC) analysis showed that the curing temperature of the hybrid UF*-pMDI resin was reduced 27.3°C compared to that of the UF-pMDI resin. When these hybrid resins were used to bond plywood respectively, test results showed that the UF*-pMDI resin improved the dry and wet bonding strength by 2.6% and 3.9%, respectively, compared with the UF-pMDI resin under the condition of hot pressing time (3 min) and temperature (140°C), meeting the requirement of Chinese standard of GB/T 9846–2015 for Class III board. This study provides a new path for further improving the performance and design of hybrid resins based on isocyanate and urea-formaldehyde resin. 相似文献
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通过氯乙烯与醋酸乙烯酯的共聚试验,研究了单体的投料配比、加料工艺、聚合转化率等对氯醋共聚糊树脂中醋酸乙烯酯含量以及树脂性能的影响规律,掌握了在10 L聚合釜中制备高醋酸乙烯酯含量氯醋糊树脂的聚合工艺。 相似文献
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Crosslinked resins were prepared from α,ω-diglydicyl and α,ω-dimethacryloyl oligo(ethylene oxide)s by anionic polymerization with triethylenediamine/n-pentanol initiating system or by free-radical polymerization, respectively. Their activity as solid-liquid phase transfer catalysts was proved in the reaction of 1-bromobutane with potassium phenoxide, and compared with the activity of similar resins synthesized from α,ω-diglycidyl oligo(ethylene oxide)s and triethylenetetramine (TETA). The catalytic activity of dimethacryloyl resins was higher than that of diglycidyl resins for oligomer chains longer than 6–7 oxyethylene units, whereas the opposite was true for resins of shorter chain lengths. These differences were explained by an unlike graft content of the resins in the former case, and by a different ability to complex the potassium cation into the meshes of the resin lattice, in the latter. In order to improve the catalytic activity of the resins two methods were developed consisting in the increase of the number of grafts either by decreasing the ratio of TETA/epoxy end groups used to the crosslinking of diglycidyl oligomers or by adding 2-mercaptoethanol as a transfer agent to the free-radical crosslinking process of dimethacryloyl oligo(ethylene oxide)s. 相似文献
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尤戎(Uron)树脂及其用法对脲醛树脂性能的影响 总被引:2,自引:0,他引:2
以不同工艺制备了三种含尤戎结构的脲醛树脂(Uron树脂),通过其与普通脲醛树脂的混合制得多种混合脲醛树脂。研究了Uron树脂及其使用方法对降低脲醛树脂胶粘剂游离甲醛含量及胶接胶合板甲醛释放量的作用与效果。结果表明:1)三种不同摩尔比的Uron树脂对脲醛树脂游离甲醛含量及胶接胶合板甲醛释放量都有明显的降低作用,游离甲醛含量最多可降低43%,甲醛释放量最多可降低61%;2)Uron树脂的添加量在10%-20%时对胶合强度的提高有利,强度最大可提高29%;3)低摩尔比Uron树脂对脲醛树脂的改性效果优于高摩尔比Uron树脂。 相似文献
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脲醛树脂改性工艺中的酸度条件控制 总被引:4,自引:1,他引:4
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 相似文献
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Structurally isomeric 15N-labeled polymeric methylenebis(phenylisocyanate), pMDI, adhesives were synthesized. One resin had a high content of 4,4'-MDI, and another was prepared with a high content of 2,4'-MDI. Both resins were cured with wood (Liriodendron tulipifera) for various times and temperatures and then analyzed using 15N CP/MAS NMR. It was found that resin polymerization occurs via the reaction of isocyanate with wood moisture to form polyurea. Biuret formation and isocyanate dimerization were detected. Urethane formation probably also occurs; however, signal overlap of urea and urethane signals prevents a definitive conclusion. These findings are similar to previous ones; however, subtle differences are noted. The structurally isomeric resins displayed similar chemistries. Of the two resins, the resin prepared with a high content of 2,4'-MDI cured more slowly, and resulted in a network that was more mobile in the midkilohertz frequency range. This leads to the prediction that resins high in 2,4'-MDI may have a superior performance in impact loading. 相似文献
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Concentrated inverse emulsion polymerization was used for making chromatography columns [based on crosslinked polystyrene divinylbenzene (PS–DVB)] with pore sizes less than 10 μm. For application of these columns in ion‐exchange chromatography, the sulfonation process was performed by concentrated sulfuric acid. According to X‐ray fluorescence analysis and ASTM D2187‐94 standard test method, the total capacity of resins (sulfonated PS–DVB) increased with increasing time. To obtain high‐capacity resins, the sulfonation process was carried out over two steps. The optimum sulfonation time for the first and second sulfonation steps was 24 and 48 h, respectively. By increasing the DVB content, the capacity of resins passed through a maximum; thus the optimum amount of DVB, as crosslinking agent in the sulfonation process, was 22.5%. The structure of columns was analyzed by scanning electron microscopy (SEM). SEM evaluations showed that the porous structure of PS–DVB resin was maintained intact after the sulfonation steps. According to DSC–thermal gravimetry thermograms, it was confirmed that the residual monomer concentration after polymerization process was negligible. Also, the PS–DVB resins exhibit thermal stability up to 300°C and this quantity would increase with increasing amount of DVB weight percentage. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 2973–2979, 2004 相似文献