On the performance of a melamine–urea–formaldehyde resin for decorative paper coatings

The decorative laminates industry is a highly competitive industrial sector. To be profitable, manufacturers of impregnated papers for surface laminated MDF and particleboards need to significantly reduce their production costs. Melamine formaldehyde resin (MF) formulations are commonly used for impregnation and coating of such papers, melamine being an important, but costly raw material used in high quantities. While MF is substituted by cheaper urea formaldehyde resins (UF) in the core impregnation, for paper surface films pure MF is used. Therefore, a further reduction in cost could be achieved if a portion of the melamine in the surface film was replaced by urea. In the present contribution, recent results of technological tests on paper laminates using a novel melamine–urea–formaldehyde resin (MUF) formulation are reported and their performance is compared to traditional surfaces made from MF.     

低压短周期浸渍纸饰面刨花板技术的应用研究

本文探讨了低压短周期浸渍纸用三聚氰胺树脂和脲醛树脂的改性机理，制备工艺及其浸渍纸饰面刨花板工艺技术。     

聚乙二醇改性三聚氰胺甲醛树脂对汽车空气滤纸性能的影响

采用聚乙二醇对三聚氰胺甲醛树脂进行改性,改性后的树脂用作交联剂添加到苯丙乳液中,并对汽车工业滤纸原纸进行浸渍加工处理。通过研究聚乙二醇(P)、三聚氰胺(M)、甲醛(F)的不同配比、树脂添加量及固化pH值,探讨了其作为乳液交联剂对汽车工业空气滤纸的抗张强度、耐破度、耐水性、透气度的影响。实验结果表明,当P与M的摩尔比为0.32,F与M-MP的摩尔比为2.8,改性树脂添加量为苯丙乳液固含量的4%,固化pH值为6～7时,汽车工业空气滤纸的综合性能最佳(苯丙乳液的上胶量为25%)。当pH值为6时,滤纸的抗张强度为4.51 kN/m,耐破度为340 kPa,耐水性为39.4min,透气度为334 L/(m2.s)。     

Factors influencing the processing and technological properties of laminates based on phenolic resin impregnated papers

High quality decorative laminate panels typically consist of two major types of components: the surface layers comprising décor and overlay papers that are impregnated with melamine-based resins, and the core which is made of stacks of kraft papers impregnated with phenolic (PF) resin. The PF-impregnated layers impart superior hydrolytic stability, mechanical strength and fire-resistance to the composite. The manufacturing involves the complex interplay between resin, paper and impregnation/drying processes. Changes in the input variables cause significant alterations in the process characteristics and adaptations of the used materials and specific process conditions may, in turn, be required. This review summarizes the main variables influencing both processability and technological properties of phenolic resin impregnated papers and laminates produced therefrom. It is aimed at presenting the main influences from the involved components (resin and paper), how these may be controlled during the respective process steps (resin preparation and paper production), how they influence the impregnation and lamination conditions, how they affect specific aspects of paper and laminate performance, and how they interact with each other (synergies).     

改性剂对三聚氰胺甲醛树脂及饰面刨花板性能的影响

研究了4种改性剂(己内酰胺、丙三醇、二甘醇、蔗糖)对三聚氰胺甲醛树脂技术指标的影响;考查了改性树脂对饰面刨花板的理化性能的影响。结果表明:与未改性树脂相比,改性树脂的黏度、pH值、适用期无差异。在浑浊时间和固化时间上,己内酰胺改性树脂明显增长、丙三醇和二甘醇改性树脂有所增加、蔗糖改性树脂增加不明显。改性树脂对饰面刨花板的耐水蒸气和耐香烟灼烧性能影响不大,对耐污染、耐龟裂性能影响很大。     

改性酚醛树脂用于滤纸增强的研究

通过三聚氰胺的改性以及PVA的增韧,研制成一种水溶性改性酚醛树脂,将其应用于汽车工业滤纸的增强。主要探讨了影响树脂及浸渍滤纸性能的一些因素如原纸定量、上胶量、固化工艺以及树脂合成的相关因素如酚醛摩尔比、反应温度和反应时间、改性剂和PVA用量。研究结果表明：采用甲醛/苯酚=3.25的摩尔比投料,通过两步碱催化合成工艺,在50～85℃程序升温下连续反应2～4h,并加入占甲醛用量6.88%的三聚氰胺以及PF树脂绝干量1.5%的PVA改性剂,可制备出综合性能较好的水溶性酚醛树脂。用该改性酚醛树脂浸渍滤纸后固化,纸的物理性能都得到明显的改善。耐破度可达到328kPa、抗张强度达5.15kN/m、伸长率达4.78%、7.5°挺度2.4mN·m,而且树脂贮存时间能达到20d。     

树脂固化度对强化木地板性能的影响

通过对强化木地板(“两纸一板”工艺压贴)浸渍纸树脂固化度的测试,分析热压时间长短对浸渍纸树脂固化度的影响,进而分析浸渍纸树脂固化度对地板耐磨性能和甲醛释放量的影响。     

On the warping behaviour of particleboards coated with melamine formaldehyde resin impregnated papers

Impregnated papers are widely used as decorative, protective and balance sheets in decorative laminates for the furniture, flooring and building industries. One important property of such composites is their warping behaviour. Especially for laminate flooring, warping of the lamellae is undesirable. In the present study the influence of important process parameters in the manufacturing of impregnated papers is quantitatively analyzed based on an industrial experiment carried out at an Austrian impregnation plant. Catalyst concentration, moisture content, resin loading and base paper supplier were varied according to an experimental design. The thermal properties of the impregnated papers and the warping behaviour of the corresponding boards were evaluated using response surface methodology. The resulting models allowed quantifying the relative importance of single factors on composite warp and defining the useful working range. Determination of the thermal properties of impregnated papers using DSC and TMA was not sufficient to predict laminate warp.     

On the warping behaviour of particleboards coated with melamine formaldehyde resin impregnated papers

Impregnated papers are widely used as decorative, protective and balance sheets in decorative laminates for the furniture, flooring and building industries. One important property of such composites is their warping behaviour. Especially for laminate flooring, warping of the lamellae is undesirable. In the present study the influence of important process parameters in the manufacturing of impregnated papers is quantitatively analyzed based on an industrial experiment carried out at an Austrian impregnation plant. Catalyst concentration, moisture content, resin loading and base paper supplier were varied according to an experimental design. The thermal properties of the impregnated papers and the warping behaviour of the corresponding boards were evaluated using response surface methodology. The resulting models allowed quantifying the relative importance of single factors on composite warp and defining the useful working range. Determination of the thermal properties of impregnated papers using DSC and TMA was not sufficient to predict laminate warp.     

机油过滤纸用水溶性酚醛树脂的制备及应用

通过两次加料制备了一种低分子质量的水溶性酚醛树脂,研究了酚醛树脂的固化行为,并结合滤纸浸渍酚醛树脂固化后强度性能的变化,确定了树脂的最佳固化温度。通过对酚醛树脂浸渍和固化工艺的研究以及对过滤纸性能的比较表明,水溶性酚醛树脂用于浸渍增强过滤纸是可行的。定量为135 g/m2的过滤原纸浸渍树脂固化后,耐破指数1.53 kPa·m2/g,抗张指数30.1 N·m/g,湿抗张指数9.26 N·m/g,固化后过滤纸有良好的强度性能。通过孔径分析,发现该水溶性酚醛树脂对过滤纸的孔径大小以及分布几乎没有影响,浸渍后过滤纸仍保持优良的孔隙结构。     

改性剂对三聚氰胺甲醛树脂及饰面刨花板性能的影响

研究了4种改性剂（己内酰胺、丙三醇、二甘醇、蔗糖）对三聚氰胺甲醛树脂技术指标的影响;考查了改性树脂对饰面刨花板的理化性能的影响。结果表明：与未改性树脂相比,改性树脂的黏度、pH值、适用期无差异。在浑浊时间和固化时间上,己内酰胺改性树脂明显增长、丙三醇和二甘醇改性树脂有所增加、蔗糖改性树脂增加不明显。改性树脂对饰面刨花板的耐水蒸气和耐香烟灼烧性能影响不大,对耐污染、耐龟裂性能影响很大。     

机油滤纸用环保型水溶性酚醛树脂的制备及应用

通过多步加料法制备了一种环保型水溶性酚醛树脂,通过DSC研究酚醛树脂的固化行为,并应用于机油过滤纸,对滤纸浸渍酚醛树脂固化后的力学性能和耐机油性能进行了研究。实验结果表明,该水溶性酚醛树脂游离醛浓度为1.5%,游离酚浓度为0.42%。定量为90g/m2的滤纸浸渍树脂固化后,耐破度为404kPa,抗张强度为5.75 kN.m–1,断裂功为188J.m–2,固化后滤纸有良好的耐机油性能。树脂对滤纸的平均孔径与最大孔径没有影响,浸渍后滤纸仍保持优良的孔隙结构。     

The influence of curing conditions on properties of melamine modified wood

The curing conditions influence the material properties of wood modified with methylated melamine formaldehyde resin. To identify the most influential parameters, the process conditions were varied separately. The degree of conversion (differential scanning calorimetry; DSC), work in bending, nitrogen fixation, formaldehyde emission, formaldehyde content and content of free formaldehyde were measured to verify the influence of the curing conditions on the material properties. The temperature and duration positively influenced the curing of melamine resin as the DSC results and the nitrogen fixation indicate. However, the relative humidity (RH) had the greatest influence on the material properties: the formaldehyde properties and the work in bending differed most between dry and high RH processes with the latter producing material being less brittle and having lower formaldehyde emissions. It can be derived that DSC measurements, formaldehyde emission and -content are valuable methods to characterize the influence of curing conditions on the material properties. The formaldehyde content in combination with the emission revealed a different formaldehyde release factor for dry and high RH processes. In the future, the curing process conditions can be designed depending on the desired material properties: dry, high temperature processes will lead to more complete curing, whereas hot steam processes can be used for material with low formaldehyde emissions.     

X射线衍射和红外光谱法分析磨料的成分

采用X射线衍射和红外光谱法，对磨料的成分进行了分析。结果表明：磨料中含有金刚石和三聚氰胺甲醛树脂。再采用热处理方法，对磨料中三聚氰脂甲醛树脂进行定量分析。方法简单易行，合理可靠，能够准确测定磨料中的成分。     

Feuchtebeständigkeit und Hydrolyseresistenz von Holz-zu-Holz-Bindungen in Spanplatten,hergestellt mit formaldehydarmen modifizierten Harnstoff-Formaldehydharzen unter Einsatz verschiedener Härtungsbeschleunigersysteme

Two different UF-resins (UF 1 and UF 2) with significant differences in their viscosity of their 50% solutions (UF 1: 70 mPa·s, UF 2: 46 mPa·s), but almost the same molar ratio F:U (UF 1: 1,11∶1, UF 2: 1,12∶1) and small differences in the content of free formaldehyde (UF 1: 0,07%, UF 2: 0,09%) and water tolerance (UF 1: 1∶0,90, UF 2: 1∶1,18) were modified with a melamine resin (F:M=1,6∶1), resorcinol, tannin and PMDI. The unmodified and modified resins were tested for some of their technological properties before and after curing using different catalyst systems (ammonium chloride, ammonium sulfate, ammonium nitrate, ammonium sulfate/formic acid). The results show:

1. There are no remarkable differences between the gelation time of the unmodified resins, however, the resin with the higher content of free formaldehyde shows higher reactivity especially at high dilution.
2. The thermoanalytical data of the two resins (temperature curing maximum and reaction enthalpy) are more or less the same, when the same hardener is used.
3. The catalyst has a definite influence on the temperature of curing maximum and on the enthalpy of the curing reaction. A big difference in curing temperature was noticed between ammonium chloride, ammonium sulfate and ammonium nitrate on the one side and ammonium sulfate/formic acid on the other side.
4. The unmodified resins show big differences in the formaldehyde release after curing. UF 1 releases more formaldehyde after curing compared to UF 2, as measured by the WKI-flask-method and the Perforator method.
5. Modification of UF-resins with melamine resin, resorcinol, tannin and PMDI decreases the formaldehyde release of the cured resin significantly. The effect of melamine resin and resorcinol are extremly huge.
6. Melamine resin and resorcinol have no negative effect on the shelf life of UF-resins, however, tannin and PMDI do negatively affect the storage stability of the UF-resins.

     

Recycling melamine-impregnated paper waste as board adhesives

Melamine impregnated paper offcuts and waste has been shown to be usable both directly, in finely powdered form, as a binder for particle board and as a melamine substitute during the formulation and preparation of liquid MUF resins. Both approaches were based on the residual activity of the MF resin present in the resin. Amounts of waste melamine paper of 22% on dry wood, equivalent to 10% melamine resin solids on total dry panel weight, were shown necessary for water resistant particleboard, and 18.5% for interior particleboard. Due to problems connected to excessive viscosity increase only a maximum of 25% of the total melamine in the formulated melamine resin could be substituted to good effect in the formulation of liquid MUF resin adhesives.     

Effects of resin open time and melamine addition on cold pre-pressing performance of a urea–formaldehyde resin

The pre-pressing performance of urea formaldehyde resins has a significant impact on plywood production efficiency. This paper reports on the effects of the time elapsed after the addition of the hardener (“resin open time”) and of a melamine addition on the cold pre-pressing performance of UF resins. The changes in pH and viscosity, the thermal behaviour, and the structural composition as well as the performance during cold pre-pressing of veneers were investigated. Cold pre-pressing performance was measured by testing pre-pressed three-ply plywood stacks. The results showed that the cold pre-pressing performance is enhanced with longer time after preparation of the resin mix before application onto the veneers and also by longer pre-pressing times. All plywood stacks with at least 2 h pre-pressing time reached the so-called G1 grade (where the re-opened area of the cold pre-pressed plywood stack was 0), which meets the industrially accepted requirements for plywood fabrication. Further, the addition of melamine improved the cold pre-pressing behaviour compared to the investigated UF resin without melamine, showing an earlier start of the development of the pre-pressing shear strength and higher G grades at the various cold pressing times. There are two main reasons for the enhanced cold pre-pressing performance of the resin under the investigated conditions: (1) influence of the “resin open time”: a certain further condensation of the resin after preparing the glue mix (addition of hardener) leading to increased molar mass and viscosity ultimately transforming the resin from liquid-state to gel-state; (2) a higher methylol content in the resin after incorporation of melamine into the resin, which enhanced the formation of hydrogen bonds between the resin and the wood surface. These conclusions represent a feasible approach for the improvement of the cold pre-pressing properties and thus the practical applicability of UF resins with low molar ratios.     

醋丙乳液交联体系对汽车过滤纸湿强度性能的影响研究

使用交联单体甲基丙烯酸(MAA)和N-羟甲基丙烯酰胺(NMA)以及乳液体系加入外交联剂三聚氰胺甲醛树脂(MF)的方法提高树脂的交联度,研究了交联体系对醋丙乳液浸渍后过滤纸湿强度性能的影响。结果表明,乳液体系中引入交联体系可以有效增强浸渍滤纸的强度性能。在MMA用量为20%(wt)、MAA用量为3%(wt)、NMA用量为4%(wt)、MF用量为4%(wt)时,改性乳液的耐水性能增强明显,湿老化后滤纸的耐水保持率超过65%。     

三聚氰胺甲醛树脂在阻燃型空气滤纸中的应用

采用磷系阻燃剂制备内燃机用阻燃型空气滤纸,并用三聚氰胺甲醛树脂替代部分苯丙乳液进行增强,研究其对阻燃剂用量的影响.结果表明,15％的三聚氰胺甲醛树脂和85％的苯丙乳液进行复配后,阻燃剂的留着率在14％时即可获得优异的阻燃性能,可节约22％的阻燃剂用量,且不会降低滤纸的力学性能.     

立式浸渍干燥机加热技术探讨

简要分析覆铜板芯布立式干燥系统组成和原理、辐射板干燥及其气流加热循环、气帘冷却循环等技术。该干燥原理类似于人造板用贴面浸渍层压纸气流干燥工艺,值得我国人造板设计者和经营者借鉴。