Mechanism of Chrome-free Tanning with Tetra-hydroxymethyl Phosphonium Chloride

Tetra-hydroxymethyl phosphonium chloride （THPC） has been considered as an important chrome-free tanning agent. To understand the THPC tanning mechanism, the structure, charge distribution, activity and tanning ability of each phosphorous compound in THPC tanning system were studied, by ^31p NMR, FT-IR spectroscopy, differential scanning calorimetry （DSC） and computational chemistry method, etc. When pH raised to 6.0, the decomposition of THPC would take place, which results in a production of free formaldehyde, tri-hydroxymethyl phosphonium （TrHP） and tri-hydroxymethyl phosphine oxide （TrHPO）. At pH 9.0, THPC will be converted completely to TrHP and most TrHP is further oxidized into TrHPO. It is possible that, in reaction of phosphorous compounds and collagens, both P-C and C-O bonds would break simultaneously or individually. From molecular charge distribution and bond polar properties, it is deduced that, if P-C bonds break, the activity is in order of TrHPO 〉 THPC 〉 TrHE whereas if C--O bonds break, the order is TrHP 〉 THPC 〉 TrHPO. It is more possible that P--C bonds will break in reaction with collagen, and TrHPO may be more active in the THPC tanning system. The results of tanning and DSC also prove the above conclusion. Furthermore, the fact that the shrinkage temperature of THPC tanned leather was below 70℃ when basified to pH 5.0 or lower suggests that the hydroxymethyl groups of THPC and TrHP are less possible to combine directly with amino groups of collagen.

Investigation of Formation Process of the Chrome-free Passivation Film of Electrodeposited Zinc

The feasibility was investigated to substitute chrome-free passivation treatment of electrodeposited zinc in a titanium bath for chromate passivation treatment. The formation mechanism of the chrome-free passivation film was further analyzed. The surface mor- phologies and the elemental compositions of the treated samples with varied immersion times were observed by scanning electron mi- croscopy （SEM） and determined by energy dispersion spectrometry （EDS）, respectively. The electrode potential of the sample surface was recorded in the film formation process. The changes of the electrode potential are in accordance with that of SEM and EDS of the sample surface. The results of X-ray photoelectron spectroscopy （XPS） show the chrome-free passivation film composed ofZnO, SiO2, TiO2, Zn4Si207（OH）2, and SrF2. The anode zinc dissolution and the local pH value increase due to the cathode hydrogen ion reduction process result in the formation of the chrome-free passivation film. The macro-images of the chrome-free passivation films formed on electrodeposited zinc show that the color of the film changes from blue to iridescence with the increase of the immersion times.

Development and Application of Chrome-free Refractory Materials for RH Degasser

The research progress and industrial application of chrome-free refractories for RH degasser were introduced in the paper.It is proved that unburned magnesia-spinel refractories used for RH throat and snorkel in Baosteel have longer service life compared with traditional direct bonded fused magnesia-chrome materials.The new developed chrome-free unburned magnesia-spinel composite can fully meet the present demand for RH operation and can be applied extensively for RH processing.At present,instead of chrome-containing materials,chrome-free refractories have been applied widely for RH in Baosteel.Super low carbon MgO-C material with high mechanical properties at mild and high temperatures can be an alternative chrome-free material for RH.

A chrome-free combination tanning strategy: based on silicic acid and plant tannin

Silicic acid,commonly derived from cheap and easily available sodium silicate,has recently received great attention for application in leather industry to produce ecological leather with a cleaner approach.However,leather tanned with silicic acid alone is poor in storage stability,which limits its practical application in leather production.In this work,a new environment-friendly combination tannage based on silicic acid and plant tannin was developed to address this issue along with improving the comprehensive performances of leather.The obtained leather was characterized by scanning electron microscopy,Fourier transform infrared spectroscopy,X-ray photoelectron spectroscopy and so on.The results showed that compared with leather tanned with silicic acid alone,the leather tanned with this combination method possessed improved thermal stability,enhanced mechanical properties,acceptable softness,appropriate hydrophilicity,and especially enhanced storage stability.More importantly,the combination tanned leather with 1:1 of the mass ratio of silicic acid to vegetable tannin(composed of valonea extract and mimosa extract with the same weight)had more prominent comprehensive performances.In addition,the results demonstrated that hydrogen bonding played an important role in the combination tanning process.Furthermore,the hydrogen bonds generated between phenolic hydroxyl groups of polyphenols with silicon hydroxyl groups of silicic acid molecules inhibited the excessive condensation of Si-OH groups between themselves.Subsequently,the assessment of environmental impact revealed the value of BOD 5/COD of the wastewater produced in this combination tanning process is more than 0.3,indicating the chrome-free combination tannage based on silicic acid and plant tannin was an environment-friendly tanning technology.These findings therefore indicated that a new chrome-free tanning method with silicon and biomass materials as main tanning agents has potential practical application prospect in leather production.

Self-driven directional dehydration enabled eco-friendly manufacture of chrome-free leather

Manufacture of eco-friendly chrome-free leather is of great significance for realizing sustainable development of leather industry.Conventional tanning theory believes that it is impossible to convert raw hide to leather without the utilization of cross-linking agent(e.g.,chrome salts)among collagen fibers in raw hide.Here,we developed a brand-new leather manufacture strategy that relied on the composite dehydration media enabled self-driven directional dehydration mechanism to accomplish chrome-free leather manufacture for the first time,rather than followed the classic cross-linking mechanism that has been obeyed for more than one century in leather industry.We demonstrated that the essence of leather making is to regulate the water content in raw hide rather than to form cross-linkage among collagen fibers.The composite dehydration media comprised of anhydrous ethanol and molecular sieves(3A activated zeolite powder)successfully guaranteed continuous self-driven directional dehydration of raw hide by establishing stable water concentration gradient between raw hide and ethanol,which significantly increased the dispersity of collagen fibers in raw hide(with the water content reduced from 56.07%to 5.20%),thus obtaining chrome-free leather that is more ecological than chrome-tanned leather due to the elimination of any tanning agent.The as-prepared chrome-free leather exhibited outstanding tear force(174.86 N),tensile strength(24.56 N mm−2),elongation at break(53.28%)and dry-thermal stability,superior to chrome-tanned leather.Notably,the used compos-ite dehydration media was recyclable for chrome-free leather manufacture,therefore facilitating an environmentally benign leather manufacture process.Our investigations are expected to open up a new conceptual leather making strategy that is applicable for realizing substantial manufacture of eco-friendly leather.

加速老化的无铬鞣革中游离苯胺的FIA-UV法分析

采用流动注射分析-紫外光谱法(FIA-UV),基于苯胺与亚硝酸盐在酸性条件下发生的重氮化反应及其在碱性条件下的偶合显色反应,实现苯胺的有效检测.通过实验参数的优化,确定495 nm为最大吸收波长,建立了苯胺质量浓度在0.002~2.0 mg/L范围内与峰高具有良好线性关系的模型(R^(2)=0.9997),检出限为1.62μg/L,重复性(RSD)为0.71%.该方法在加速老化后皮革萃取液中的应用表现出97.8%~103.8%的加标回收率,相较国标法具有更优的抗干扰能力和更高的检测精度.成功建立的苯胺检测新方法,为无铬鞣革产品的质量控制及环境监测提供了重要的技术支持,有助于提高公共健康和环境保护水平.

6063铝合金中性无铬转化膜制备及膜层性能分析

目的提高铝合金微小器件的耐蚀性,开发一种条件温和可控的转化膜成膜工艺。方法采用中性无铬转化工艺,在6063铝合金表面制备转化膜。通过研究NaF、NH_(4)HF_(2)、KMnO_(4)、十二烷基硫酸钠(SDS)和没食子酸等几种添加剂对转化膜外观与耐蚀性的影响,确定NH_(4)HF_(2)为最佳添加剂。采用电化学方法分析膜层的耐蚀性,用SEM和EDS分析表面形貌及元素组成,并采用XRD和XPS表征膜层晶态结构和化合物组成。基于检测结果,简要分析转化膜的成膜过程。结果最终得到了中性转化处理的最佳成膜工艺为EDTA-2Na8.0g/L,单宁酸1.0g/L,Na_(2)WO_(4)6.0g/L,H_(2)ZrF_(6)4.0g/L,NH_(4)HF_(2)3.0g/L,pH6.6,成膜温度为30℃,成膜时间为15 min。该工艺所制备的转化膜外观致密均匀,颜色为浅黄色。电化学测试结果表明,转化膜具有良好耐蚀性,自腐蚀电流密度由基体铝合金的16.22µA/cm^(2)下降为转化处理后的0.87µA/cm^(2)。EDS能谱分析结果表明,膜层主要由Al、C、F、O、Na、Zr和W元素组成。XRD结果显示,膜层中含有Na_(3)AlF_(6)晶体。XPS分析结果表明,膜层中还含有Al_(2)O_(3)、AlF_(3)、WO_(3)、ZrF_(4)以及金属有机络合物。结论采用中性转化处理工艺,可以在6063铝合金表面制备有色均匀、耐蚀性良好的转化膜,膜层主要由Al的难溶化合物组成。

生物质基无铬鞣剂在可持续皮革制造中的研究进展

鞣制是使生皮变成革的关键工序。目前,铬鞣剂因其优良的性能仍占据鞣剂市场的90%。但是Cr3+存在转化为具有致癌性Cr6+的潜在危害,铬鞣废水的排放对生态系统的潜在风险不容忽视。因此,无铬鞣剂成为研究的热点。其中生物质材料因其来源广泛、可再生和生物可降解好等优点而备受关注。文章对多糖类、蛋白类等生物质材料进行了介绍,并对多糖、蛋白质的功能改性及其在皮革鞣制和复鞣的应用进行了归纳。同时,对生物质基鞣剂的发展前景及推广应用进行了展望。

有机配体对铝-锆配合物鞣制性能及环境效益的影响

采用氧化木质素磺酸钠(OSL)、酒石酸(TA)和氧化淀粉(OST)与铝锆盐(AZ)进行配位鞣制,并与传统铬(Cr)鞣进行对比,评估了4种鞣制技术的鞣革性能、坯革性能和环境效益。OSL-AZ与皮胶原以配位键结合为主,辅以OSL的磺酸基、羧基、酚羟基和苯环与皮胶原间的离子键、氢键和疏水键作用,促使OSL-AZ在皮胶原间形成大分子刚性交联网络,鞣革的收缩温度高达88.4℃,等电点达到7.54,对染整化学品吸收率超过84%,最终获得的坯革物理性能优良,仅次于Cr鞣坯革。TA和OST无磺酸基、酚羟基和刚性苯环,与皮胶原的相互作用弱,故其铝-锆配合物的鞣制性能不及OSL-AZ。OSL-AZ鞣革和废水的生物降解性明显优于传统Cr鞣革和废水。综上,OSL-AZ鞣制技术是一种实用环保的制革技术。

无铬鞣废革屑胶原提取物与PBAT共混成膜性能

利用稀酸法分别从沸石、TWS鞣废革屑中提取胶原,以提取率、特性粘数等为指标优化提取工艺,对纯化后的胶原水解物进行表征。随后选取TWS鞣废革屑提取的胶原水解物(C-TWS)与聚己二酸对苯二甲酸丁二醇酯(PBAT)共混成膜,探究二者的成膜性能。结果表明:两种胶原水解物均含有17种氨基酸,元素组成以C、N、O为主,矿物盐含量低,是优质的生物可降解蛋白基材。PBAT/C-TWS共混过程为简单的物理共混,C-TWS组分含量的增大使复合膜的水蒸气透过量提高43.05%~182.5%。C-TWS组分含量为30%时,薄膜的最大热降解温度由405.4℃降低至386.5℃,所有比例共混膜都具有良好的透光率,共混体系中C-TWS组分含量小于50%时具有较好的相容性。

三聚氯氰与氨基葡萄糖反应产物的鞣革性能

以三聚氯氰和氨基葡萄糖为原料,合成了N,O-二-(4,6-二氯-1,3,5-三嗪基)-氨基葡萄糖(CG)。通过FTIR和1HNMR对CG的结构进行了表征。并将其用于生皮鞣制实验,以脱灰软化状态的绵羊皮为材料,以单因素实验确定了适宜的鞣制工艺条件为:CG鞣剂用量为7.5%(以灰皮质量计,下同),并采用30、40、45℃阶梯控温模式进行鞣制,各温度对应下的鞣制时间为1、1.5、2 h。结果表明,CG初鞣的坯革收缩温度可达78.9℃,革面洁白细腻,身骨柔软;坯革具有良好的染色性能,经过染整的坯革也具有优异的卫生性能和物理机械性能。

铝鞣法的演变:从传统技术到绿色制革

铝鞣作为最古老的鞣法之一,一直被用于制革。近年来,由于制革行业面临着Cr(Ⅵ)和含铬固废带来的环境与健康风险,铝鞣法在生态皮革制造中再次被重点关注。本文全面综述了铝鞣技术的研究现状,具体包括铝单独鞣、植-铝结合鞣、铝与其他鞣剂结合鞣以及新型铝鞣技术;对未来铝鞣技术的发展方向进行了展望,有助于生态皮革制造技术的发展。

基于单因素法的植物鞣剂-沸石鞣剂结合鞣革研究

为改善植物鞣白湿革性能,引入了沸石鞣剂,以湿热收缩温度和物理机械性能(撕裂强度和抗张强度)为评价指标,采用单因素法,优化出基于植物鞣剂的沸石结合鞣的最佳工艺。试验结果表明,植物鞣剂-沸石结合鞣最佳条件为:沸石鞣剂的用量为5%,鞣制时间50 min,提碱终点p H为5.5,鞣制终点温度30℃,所得白湿革的收缩温度达到94.55℃,撕裂强度达到55.75 N/mm,抗张强度达到11.44 N/mm^(2),部位差显著降低。该工艺对植鞣白湿革的改善效果明显,为无铬结合鞣技术提供了新思路。

基于均匀设计的无铬复鞣工艺设计与优化

为提高皮革复鞣工艺的生态性能,以锆-铝-钛鞣白湿革为原料皮,以皮革的热收缩温度、撕裂强度、感官性能和复鞣排放废液中的COD含量作为评价指标,设计并优化基于改性戊二醛、锆铝钛配合鞣剂和阳离子油的无铬复鞣工艺。结果表明,当改性戊二醛鞣剂用量为2%、锆-铝-钛配合鞣剂用量为2%、阳离子油用量为0.4%时,复鞣效果和生态性能好,复鞣后的坯革也具有较好的耐热性能、感官性能和物理性能。这为皮革的生态设计提供了一种新思路。

基于CH/β-CD的无铬鞣白湿革长效抗菌性能研究

以β-环糊精(β-CD)醛基衍生物和盐酸环丙沙星(CH)作为抗菌剂,应用于无铬鞣白湿革(MCFL),开发了一种新型长效抗菌白湿革。采用傅里叶变换红外光谱(FTIR)、扫描电子显微镜(SEM)、差示扫描量热仪(DSC)、热重分析仪(TGA)对所得皮革的结构和性能进行表征,并考察其对大肠杆菌和金黄色葡萄球菌的抑菌效果。结果表明,与未经β-CD改性和CH处理的MCFL相比,该方法制备的皮革的Ts、Td和Tp分别提高了5.7℃、4.9℃和6.9℃;在贮藏90 d时,经CH处理后,对大肠杆菌和金黄色葡萄球菌的抑菌率仍分别达到99.7%和97.4%,比未经β-CD处理的分别提高了29.8%和34.4%。这说明改性后的MCFL具有更好的热稳定性能,且引入β-CD空腔可以包合抗菌剂,能改善因小分子抗菌剂释放导致的抗菌持久性差的问题。利用β-环糊精多醛基衍生物和CH对MCFL进行抗菌改性,可满足白湿革生产需求,为实现白湿革长效抗菌提供了一种新工艺。

艾力特AT鞣剂在浸酸与不浸酸工艺体系下的鞣制性能

以绵羊酸皮为实验对象,使用新型有机鞣剂艾力特AT分别在常规浸酸和不浸酸两种工艺体系下进行鞣制,通过坯革的收缩温度、纤维形貌及其热力学性能等分析测试,主要考察艾力特AT鞣剂在浸酸与不浸酸工艺体系下鞣制性能的差异性。实验结果表明:在两种工艺体系中,鞣制工艺条件的变化对鞣制效果产生了相似的影响;在艾力特AT鞣剂用量6%时,两种不同工艺体系下鞣制的坯革收缩温度都可以达到89℃。此外,鞣制坯革粒面饱满,毛孔清晰,热稳定性和力学性能基本接近。因此,艾力特AT鞣剂在浸酸与不浸酸工艺条件下,基本鞣制效应差异性不明显,这对于推广和应用基于艾力特AT鞣剂的无铬鞣制技术具有一定的理论指导意义。

制革无铬鞣体系中高分子化学品的构造设计研究进展

制革中无铬鞣的发展使其配套的高分子化学品开发成为热点.就高分子而言,高分子链的构造对分子结构有着重要影响,将直接影响其作为皮革化学品在工艺中的应用范围及作用效果.但目前以高分子链构造为依据的无铬鞣皮革化学品综述仍鲜有报道.基于此,本文按照线型、支化和交联等主要构造方式分类对无铬鞣配套高分子化学品进行综述.归纳探讨了不同构造的特点、影响该构造的主要因素以及对应构造在无铬鞣配套化学品制备当中的特点,以期为无铬鞣体系高分子化学品的开发提供理论支持,从而进一步推动传统皮革产业的转型升级和可持续发展.

鳄鱼皮制革工艺的研究进展

由于鳄鱼皮具有骨骼架构等特点,鳄鱼皮革加工对技术要求苛刻。近几十年,国内外不少研究者对鳄鱼皮制革加工的技术进行了不断探索。本文阐述了鳄鱼皮的特点,并重点对鳄鱼皮制革工艺在无铬鞣制、涂饰、加工和其他方向上进行了总结和展望。

丙烯酸树脂复鞣剂的亲水性对无铬鞣皮革性能的影响

无铬鞣革普遍存在亲水性强、纤维分散不足等问题,通过调控复鞣材料的亲疏水性来设计适用于无铬鞣革的复鞣剂可能是解决该问题的有效策略。研究了丙烯酸-甲基丙烯酸长链烷基酯合成的丙烯酸树脂复鞣剂(AR)的亲水性(羧基单体含量)对有机无铬鞣革性能的影响。结果表明,随着羧基单体含量的增加,AR的粒径逐渐减小、表面负电荷增加,其在无铬鞣革内的渗透深度和分布均匀度增加。当丙烯酸单体的含量为45%时,AR能完全渗透坯革,且所得复鞣坯革的纤维分散程度、疏水性能、耐干热稳定性、撕裂强度、抗张强度等最高。由此可见,设计亲疏水性合适的AR对改善无铬鞣皮革的综合性能具有重要意义。

聚乙二醇化多环氧共聚物的清洁化铬鞣应用

传统铬鞣的低铬利用率以及鞣制过程中大量含铬、含盐废水的排放严重危害生态环境和人类健康,制约了制革工业的可持续发展。研究采用自由基共聚设计并制备了一种聚乙二醇化多环氧基共聚物,将其作为预鞣剂考察了其在无盐、少铬、高吸收清洁化铬鞣过程中的应用。基于碱性条件下环氧基与胶原氨基的反应,共聚物预鞣能够封闭胶原氨基并在皮胶原纤维之间产生预交联,赋予坯革无盐浸酸性能。此外,聚乙二醇链段的引入能够在纤维表面形成水化层惰化胶原纤维,防止铬鞣初期鞣剂在皮表面的快速结合,促进铬鞣剂在皮中的均匀渗透。同时,环氧基开环反应所产生的羟基为后续铬鞣剂提供额外的结合位点,有助于提高铬鞣剂的吸收率。结果表明,共聚物预鞣能够实现无盐浸酸,能使少铬鞣法的铬吸收率由80.5%提高至95%,并显著提高成革热稳定性、力学性能和感官性能。