商士斌 王定選
(中國林業(yè)科學(xué)研究院林產(chǎn)化學(xué)工業(yè)研究所 南京 210042)
摘 要 以馬來海松酸和線性小分子二醇為原料，合成馬來海松酸聚酯多元醇，再用氨基樹脂交聯(lián)，制備馬來海松酸聚酯氨基樹脂。利用熱重分析，討論了不同原料種類及配比對樹脂耐熱性的影響。研究結(jié)果表明，馬來海松酸聚酯多元醇和氨基樹脂以及它們的配比直接影響最終樹脂的耐熱性。只有選用耐熱性好，官能度高的聚酯多元醇組分和自縮聚少的氨基樹脂組分，并且在它們的最佳配比下，才能獲得具有較好耐熱性的聚酯氨基樹脂。
Rosin is one of the most important forest products in our country, the annual output is about 4×105 tons, the worldwide annual output is about 1.2×106 tons［1］. About half of them were used or exported just as raw materials, this made the economic benefit of rosin very poor. How to modify rosin chemically and use it economically is one of the urgent tasks faced by forest chemists.
Most rosin in China were made from the resin of Pinus massoniana. One of its main features is that the content of abietic acids is about 80%, which provides good fundmentals for chemical modification of rosin［2］. Maleopimaric acid (MPA) is one of useful modified rosin products, which can be produced in industrial scale［3］. As MPA is a fused-ring tri-carboxylic acid, if the structure were laid in a resin, the resin properties, such as water resistance, hardness and thermal stability must be improved. This may result in a new utilization of rosin.
In previous articles［4～5］, esterification of MPA with some small molecular weight linear alkyl diols (LADs) was discussed. Maleopimaric acid ester polyols (MEPs) with high thermal stability were synthesized and thermal stability of rigid polyurethane foams based on MEPs was also discussed. In this report, maleopimaric acid ester polyols amino resins (MEAs) were prepared from MEPs crosslinked by etherified melamine formaldehyde resins (MFRs). By TGA, influence of each component and weight ratio of components on the thermal stability of MEAs were discussed. The properties of the resin were also measured.
1 Experimental
1.1 Materials
Except ethylene glycol is A.R., all other chemicals used are industrial products.
1.2 Synthesis of MEPs
MEP was synthesized by mixing appropriate amounts of MPA, LAD (6 times of the molar ratio of MPA) and catalyst, keeping the system at ≥200℃ until the acid value was less than 5 mg KOH/g. After washing 2～3 times with distilled water, the product was distilled at reduced pressure to drive off any unreacted LAD and water. Three MEPs were synthesized, namely ethylene glycol (EG) ester of MPA (MEP 1), diethylene glycol (DEG) ester of MPA (MEP 2) and triethylene glycol (TEG) ester of MPA (MEP 3). The properties of MEPs are gived in Table 1.
Table 1 Properties of MEPs
| Sample LAD |
MEP 1 | MEP 2 | MEP 3 |
| EG | DEG | TEG | |
| Hydroxyl value (mg KOH/g) | 233.5 | 164.7 | 131.6 |
| Molecular weight (tested by VPO) | 950 | 1100 | 911 |
| Functionality | 3.95 | 3.23 | 2.14 |
|
Table 2 Formulation of MEA |
| Ingredients | Parts by weight |
| MEP 2 | 41.3 |
| HMMM | 13.7 |
| Xylene | 35.5 |
| n-Butuol | 8.9 |
| Cat. | 0.6 |
| 1.3 Synthesis of MFRs Hexamethoxymethylmelamine (HMMM), n-butylated melamine formaldehyde resin (NBMF) and iso-butylated melamine formaldehyde resin (IBMF) were prepared by the procedures provided by S.Chen［6］. 1.4 Preparation of MEAs Certain amounts of MEP, MFR and catalyst were dissolved in n-butuol and xylene. MEA was prepared according to Chinese National Standard GB 1727―79. The curing condition was 130℃ for 3 hours. 1.5 Properties of MEA MEA was prepared according to the formulation as shown in Table 2. The properties of MEA were measured according to the corresponding National Standards of PRC. The results are: hardness, 0.93; flexibility (mm),1; adhesion (grade),1; impact resistance (kg*cm),≥50; water resistance (7 days), pass; salt water resistance (3% NaCl water solution, 7 days), pass; alkali water resistance (3% Na2CO3 water solution, 4 days), pass. 1.6 Thermogravimetric analysis (TGA) of MEAs TGA was run on a Rigaku TAS-100 type TG-DSC analyzer at heating rate 10℃/min, sample weight ca. 2 mg, temperature 50℃ to 500℃. 2 Results and discussion 2.1 Influence of MEPs on thermal stability of MEAs MEAs are actually polymer networks formed through the reactions of MEPs and MFRs. So thermal stability of MEPs plays a very important role to thermal stability of the final resins. The TGA curves of MEPs and the corresponding MEAs (HMMM as the MFR component) are shown in Fig.1 and Fig.2， respectively. The curves in Fig.1 display that MEP prepared from lower molecular weight LAD has higher thermal stability. This is possiblly due to the lower content of poor thermally stable ether C-O bonds and linear alkyl C-C bonds, as well as the higher content of MPA, a high heat resistant unit［5］. The curves in Fig.2 indicate that thermal stability of MEAs decreases with increasing molecular weight of LADs, from which the corresponding MEPs and MEAs were prepared. The reason for this may be similar to that for MEPs. Functionality may be another reason for it as well. Data in Table 1 display that functionality of MEPs decreases with increasing molecular weight of LADs. The crosslink density increases with increasing functionality. This also made the thermal stability of MEAs decreasing with increasing molecular weight of LADs, from which MEPs and MEAs were prepared. Comparing Fig.1 with Fig.2, it is not difficult to find that the order of thermal stability of MEAs is in good agreement with that of their corresponding MEPs, that is to say, thermal stability of the final MEAs was strongly dependent on that of the former MEPs. Only thermally stable MEPs prepared from small molecular weight LADs could result in the final MEAs with better thermal stability. |
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Fig.1 TGA curves of different MEPs:(1) MEP 1;(2) MEP 2;(3) MEP 3
Fig.2 TGA curves of MEAs based on different MEPs:(1) MEP 1;(2) MEP 2;(3) MEP 3 2.2 Influence of MFRs on thermal stability of MEAs |
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Fig.3 TGA curves of MEAs based on different MFRs:(1) HMMM;(2) NBMF;(3) IBMF
Fig.4 TGA Curves of MEAs prepared at different weight ratios of MEP 2/HMMM:(1)4∶1;(2)3∶1;(3)2∶1；(4)1∶1 When the ratio is small, the content of MEP2, a thermally stable unit, is low, the content of HMMM is very high, i.e., HMMM is in excess. In this case, the reactions are not only co-condensation of methoxy groups on HMMM with the hydroxy groups on MEP2 to form co-condensation crosslink networks but also self-condensation of methoxy groups on HMMM to form self-condensation crosslink networks, a poor heat resistant unit［7］. So thermal stability of MEAs increases with increasing weight ratio. When the ratio reaches a certain optimum value, the system undergoes mainly co-condensation of methoxy groups on HMMM with the hydroxy groups on MEP2 to form co-condensation crosslink networks and has a high thermal stability. Further increase of the ratio has no obvious influence on improving thermal stability of the final MEAs. In this case, the optimum ratio is about 3. The curves in Fig.4 also confirm that when the ratio reaches the optimum value, thermal stability of MEAs has nothing to do with the ratio basically. References |
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