多层帘式涂布和一种新型压光技术

帘式涂布是一种低冲击预计量涂布方式,可用于纸和纸板的涂布、帘式涂布技术所产生的涂层为仿形涂层,因而能提供良好的纤维覆盖。在多层帘式涂布中,可以同时进行多层涂布。与单层帘式涂布相比,多层帘式涂布具有许多优点：投资成本更低、设计不同涂层性质更具灵活性、具有更大的涂布操作空间及涂层更薄等,     

Adhesion properties of lactic acid based hot melt adhesives and their storage stability in different packaging applications

Adhesion properties and the stability during the use life of the package for two biodegradable hot melt adhesives were evaluated. Adhesives were based on poly (L-lactide) (PLLA) and poly(-caprolactone) (PCL) with molar ratio 81:19. One sample was stabilized by end-capping the terminal hydroxyl groups with acetic anhydride. The other sample was unmodified. Reference adhesive that was used in the studies, was a conventional non-biodegradable hot melt adhesive based on poly(ethylene-co-vinylacetate) (EVA).

Materials, which were bonded with these hot melt adhesives, were typical biodegradable packaging materials: a pigment-coated cardboard, a similar cardboard extrusion laminated with film type PLLA and an uncoated cardboard. The storage stabilities of the copolyester films and bonded structures were monitored during an eight week period at room (23°C) and at low (−18°C) temperatures.

Changes in molecular weight and crystallinity of the copolyesters were measured with gel permeation chromatography (GPC) and differential scanning calorimetry (DSC), respectively. Mechanical strength of the adhesive bonds was measured by a tensile testing instrument. Fracture surfaces of the adhesive bonds were subjected to microscopic studies.

Initial adhesion properties of the copolyesters were similar to those of EVA and better in case of PLLA-laminated cardboard. Both biodegradable copolyester samples degraded during the studied period; however, end-capping of the copolymer retarded this degradation rate.     

Blends of poly(ε‐caprolactone‐b‐lactic acid) and poly(lactic acid) for hot‐melt applications

The condensation reaction product of poly(lactic acid) (PLA) and a hydroxyl‐terminated four‐armed poly(ε‐caprolactone) (PCL) was studied by size‐exclusion chromatography, DSC, and NMR. The use of both L ‐lactic acid (LLA) and rac‐lactic acid (rac‐LA) was studied and the use of two different catalysts, stannous 2‐ethylhexanoate [Sn(Oct)₂] and ferrous acetate [Fe(OAc)₂], was also investigated. The thermal stability and adhesive properties were also measured for the different formulations. The characterization results suggested the formation of a blend of PLA and a block‐copolyester of PLA and PCL. The results further indicated partial miscibility in the amorphous phase of the blend showing only one glass‐transition temperature in most cases, although no randomized structures could be detected in the block‐copolymers. The polymerization in the Fe(OAc)₂‐catalyzed experiments proceeded slower than in the Sn(Oct)₂‐catalyzed experiments. The discoloring of the polymer was minor when Fe(OAc)₂ was used as catalyst, but significant when Sn(Oct)₂ was used. The ferrous catalyst also caused a slower thermal degradation. Differences in the morphology and in the adhesive properties could be related to the stereochemistry of the poly(lactic acid). © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 196–204, 2004     

开创压光技术新纪元——ValZone带式压光机

芬兰美卓造纸机械公司推出了最新开发的ValZone带式压光机，使得压光技术向前迈进了一大步。它采用了一种宽压区压光技术，可以大大改进纸和纸板压光的质量以及生产效率。该压光机的特点是采用长达1m的宽压区替代了传统的辊式压光机，压区由光滑的加热钢带和热辊形成，纸幅的两面可以在这个宽压区中同时得到压光，