Durable Wood Adhesives from Kraft Lignin

Gillespie, Robert H.

doi:10.1021/bk-1989-0385.ch009

Cited by 6 publications

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“…It appears that more reactive sites of R react predominantly with reactive hydroxymethylated phe- Brought to you by | University of Queensland -UQ Library Authenticated Download Date | 7/13/15 1:51 PM nols such as MP-2 deacetylated and the resulting products cause LPF resin to be polymerized and solidified by cross-linking. This assumption is supported by the report that the rate of condensation of methylolated NKL is far lower than that of PF resins (Gillespie 1989). Thus low-molecular-weight materials in LPF resins appeared to produce undesirable cross-linking reactions during the preparation of LPRF resins.…”

Section: Preparation Of Softwood Kraft Lignin-based Cold-setting (Lprmentioning

confidence: 74%

Preparation of Softwood Kraft Lignin-Based Cold-Setting Wood Adhesives

Shimatani¹,

Sano²

1995

HFSG

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KeywordsCold-Setting wood adhesives Kraft lignin Resorcinol phenol Tensile shear strength Differential scanning calorimetry Lignin-bascd adhesive SummaryThe preparation of softwood kraft lignin (NKL)-based thermosetting (LPF) and cold-setting (LPRF) wood adhesives was investigated. The LPF and LPRF adhesives were prepared by the following procedure. A mixture of NKL : phenol (8:2-7:3) was hydroxymethylated under alkaline conditions at 80°C for 2 hours for LPF resins. The LPF resins solution obtained from NKL : phenol (8 : 2) was acidified with aqueous HC1 and water insolubles (WI) were collected in a yield of 89% by ccntrifugation. Then, the WI reacted with small amounts of resorcinol at pH 11 and 80 °C for the preparation of LPRF resins. Bonding of wood veneers using LPRF adhesives was performed by cold-setting at room temperature for 48 hours. A satisfactory adhesive was mainly composed of 60 parts of KKL, 15 parts of phenol and 25 parts of resorcinol. Powdered LPF, LPRF and resorcinol-formaldehyde (RF) adhesives were analyzed by differential scanning calorimetry (DSC). Major exothermic temperature peaks of LPF, LPRF and RF resins were observed at 145.5, 116.1 and 79.0°C, respectively. The LPRF adhesives provided high-quality bonds, both wet and dry equivalent to RF adhesives. However, high exothermic temperatures and activation energies of LPRF resins compared with those of RF resins indicate that improvements may be necessary for more fast-curing. IntroductionLignin is one of the most abundant, renewable natural products on earth and it is produced in tremendous quantities every year as a byproduct of the pulping process. Numerous efforts have been made to develop its commercial uses such as for adhesives, surface-active agents and so forth but success has been limited. Based on the structural properties of lignin as polyphenols that are similar to those of phenol-formaldehyde (PF) resins, intensive studies have been carried out to exploit lignin as a substitute for phenol in PF adhesives for wood composites (Nimz 1983). However, lignin adhesives have received little commercial attention for practical and economic reasons. Von der Klashorst et al. (1985) reported that a soda bagasse lignin can be used as a substrate for a traditional type of cold-setting as well as fast-setting wood adhesives and that such adhesives are economically very attractive since they are composed of approximately 75 % bagasse lignin and 25 % resorcinol and are associated with excellent performance. They also reported in the same paper that pine kraft lignin has only approximately 0.3 carbon atoms per C 9 , reactive towards formaldehyde under alkali catalyzed conditions in contrast to the bagasse lignin with 0.7 per Cj. It is assumed by their reports that softwood kraft lignin is difficult to be utilized as a substrate for cold-setting wood ad-

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Section: Preparation Of Softwood Kraft Lignin-based Cold-setting (Lprmentioning

confidence: 74%

Preparation of Softwood Kraft Lignin-Based Cold-Setting Wood Adhesives

Shimatani¹,

Sano²

1995

HFSG

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“…133 Lignin-based phenol formaldehyde resin has been most extensively investigated for wood adhesive applications. [133][134][135][136][137][138][139][140][141][142] Typically, lignin-based phenol formaldehyde resin can be prepared by a two-step polymerization as shown in Scheme 3. 135 First, lignin reacts with formaldehyde and then the methylolated lignin reacts with phenols.…”

Section: Phenol Formaldehydementioning

confidence: 99%

Chemistry of lignin-based materials

2013

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There is a need for renewable resources as a raw material for commodity polymers. Lignin is one of the most important natural biopolymers from renewable resources due to its suffi cient supply, robust material properties and the fact that its use does not compete with the food supply. Lignin has been investigated since the late 19th century, but its applications are limited due to poor processability, low reactivity and intrinsic heterogeneity depending on the plant source and isolation methods used. Current strategies for using lignin in modern materials center on integrating it with other natural or synthetic polymers. This review article introduces the technological importance of lignin and focuses on copolymers and blends based on lignin in a broad range of applications.

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“…Strict regulations on toxic emissions and the foreseeable reduction of acceptable limits have also stimulated the wood products industry to develop biorenewable adhesives.Lignins as an adhesive resourceLimos, a natural feedstock high in polyphenolics, have been examined as a replacement, for synthetic phenol. Lignin is present in a variety of natural sources, but wood is likely .the primary source Gillespie (1989). demonstrated that kraft lignin reacted.…”

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Protein-based phenolic wood adhesives for aspen/agricultural residue blended medium density fiberboard

Ellsworth¹

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Durable Wood Adhesives from Kraft Lignin

Cited by 6 publications

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Preparation of Softwood Kraft Lignin-Based Cold-Setting Wood Adhesives

Preparation of Softwood Kraft Lignin-Based Cold-Setting Wood Adhesives

Chemistry of lignin-based materials

Protein-based phenolic wood adhesives for aspen/agricultural residue blended medium density fiberboard

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