酚液化柳杉為原料所製備酚／間苯二酚／甲醛共聚合樹脂之性質

The properties of phenol-resorcinol-formaldehyde copolymer resins prepared with phenol-liquefi ed Cryptomeria japonica as a raw material

間苯二酚－甲醛樹脂（Resorcinol-formaldehyde resin；RF）為木材工業重要用膠之一，RF 膠添加架橋硬化劑後具備中性條件下常溫硬化的能力，主要應用於集成材製造。然由於間苯二酚價格昂貴，目前多採用酚／間苯二酚／甲醛共聚合樹脂（Phenol-resorcinol-formaldehyde copolymer resin； PRF）以降低其製造成本。本研究將柳杉（Cryptomeria japonica）木材以酚為溶劑進行液化處理，並將所得液化木材（Liquefi ed wood；LW）與甲醛在不同F/P莫耳比條件下反應形成LW-PF預聚合樹脂，再添加不同比例間苯二酚形成LW-PRF共聚合樹脂。由試驗結果可知，鹼性條件較酸性條件有利於LWPRF共聚合樹脂的合成。LW-PRF共聚合樹脂的性質受合成條件所影響，預聚合階段採用甲醛／酚（F/ P）莫耳比較低者，其共聚合樹脂之固形分及粘度較高、未反應甲醛含量較少、膠液保存性較佳。共聚合階段較多間苯二酚添加比例者，其樹脂液之固形分較高、粘度較低、膠化時間較短、膠液保存性較佳。熱示差掃描卡量（Differential scanning calorimetry；DSC）熱分析顯示，常溫膠化樹脂在熱掃描過程出現進一步架橋反應的放熱峰，其中間苯二酚添加量較多者，此放熱峰向低溫側偏移。將LW-PRF共聚合樹脂應用於木材膠合時，預聚合階段採用F/P莫耳比1.8/1，共聚合階段添加40%及 30%間苯二酚者有較佳的膠合性能，其膠合強度及木破率可符合CNS 11031號「結構用集成材」標準對樹種區分編號第1類集成材之膠合性能要求。 Resorcinol-formaldehyde resin (RF) is one of the most important widely used adhesives in the wood industry. It is mainly applied in the manufacturing of laminated wood. After the adding of crosslinking hardener, RF adhesive has the capability to set at room temperature under neutral conditions. However, because resorcinol is costly, phenol-resorcinol-formaldehyde copolymer resin (PRF) is often used in order to reduce its production cost. In this study, wood of Cryptomeria japonica was liquefi ed with phenol as solvent. The liquefied wood (LW) was reacted with formaldehyde under different formaldehyde/phenol (F/P) molar ratios to form LW-PF prepolymer, resorcinol were then added at different ratios to form LW-PRF copolymers. The results showed that, compared to the acidic condition, the basic condition was better for preparing LW-PRF copolymer resins. The properties of the LW-PRF copolymers were affected by the synthesis conditions. Using lower F/P molar ratio at pre-polymerization stage, the resulted LW-PRF copolymer resin had higher solid content and viscosity, less unreacted formaldehyde content and relatively longer storage life. Increasing resorcinol in the co-polymerization stage would decreased the gel time and reduce the the viscosity of LW-PRF copolymer resin, while at the same time, enhanced solid content and storage life. Differential scanning calorimetry (DSC) thermal analysis showed that resins cured at room temperature exhibited an exothermic peak due to further crosslinking reaction. The LW-PRF copolymer resin with the addition of higher amount of resorcinol had the exothermic peak shifted to lower temperature region. When these LW-PRT copolymer resins were applied for wood gluing, resins prepared with the F/P molar ratio of 1.8/1 during pre-polymerization and with 40% and 30% of resorcinol during copolymerization had better bonding performance with bonding strength and wood failure rate meet the CNS 11031 standard requirements for structural laminated wood of the fi rst type tree species.