In the course of developing monomer casting technology $\epsilon$ -caprolactam was anionically fast-polymerized in a metal mold to produce polymeric products and the parameters associated with the casting reaction such as heating cycle, reaction time, catalyst-and initiator-concentration etc. were investigated.
$\epsilon$-Caprolactam dried by vacuum-distilling over phosphorous pentoxide was heated to a proper temperature and was activated by the addition of certain amount of catalyst and initiator. The monomer mix was then introduced into a preheated mold with the least contact with air, and the mold was placed in a heating oven. After certain time period the mold was removed from the over and cooled.
Among the catalyst bases investigated sodium hydride was the most active and convenient to use. Hexane diisocyanate gave the best results as an initiator.
The following reaction conditions were found to give the best results.
Concentration of catalyst NaH 0.35 mole %
Concentration of initiator $OCN(CH_2)_6NCO$ 0.35 mole %
Temperature for the activation 130 - 135℃
Mold preheating temperature 180℃
Final mold temperature 190℃
Polymerization time 12 - 15min
The product thus polymerized contained 2-3% of equilibrium monomer concentration and the molecular weight was in the range of 500,000. Density measurement and DSC analysis indicated that crystallinity was high (40%).
Various strength values were higher than those of common molded nylon product. Tensile strength was in the range of 900Kg/㎠ and modulus of elasticity was in the range of 40,000Kg/㎠. These high strength properties were attributed to the high molecular weight and high crystallinity.
-Caprolactam monomer 에서 수분을 완전히 제거한 후 촉매로서 sodium hydride, 중합 개시제로서 hexane diisocyane 를 사용하여 그들의 농도와 반응 온도, 반응 시간을 변화 시키면서 Nylon 6의 monomer casting 에 대한 최적 조건을 구하였다.
합성 방법은 음이온 중합에 의한 bulk polymerization 으로써, 먼저 $\epsilon$-caprolactam 을 감압 증류하여 수분을 제거시킨 후 130 - 135℃ 로 가열하여 sodium hydride (0.3 - 0.35 mole%) 와 hexane diisocyanate (0.35 mole%) 를 넣어 활성화 시킨 다음 180℃ 로 예열된 금형에 넣고 190℃까지 가열하여 10 ? 12분간 반응 시켰다.
다음 온도를 내려 180℃ 에서 20 ? 30분간 tempering 하여 MC Nylon의 결정성을 증가 시킨후 금형을 상온까지 천천히 식혀 분해하여 완전히 성형된 MC Nylon 을 얻었다.
이렇게 하여 생성된 성형체는 monomer 의 함유랑이 2 ? 3%정도이기 때문에 추출할 필요가 없었고 분자량은 500,000 정도를 나타 내었다.
Density gradient technique 에 의하여 밀도를 측정 하였으며, 이 밀도로부터 결정성을 구하였다.
Commercial Nylon 6 에 비하여 밀도는 2%정도 증가 했으며, 결정성은 15% 증가 하였다.
DSC 로부터 melting point 220℃ 를 구하였으며 피크의 모양으로부터 MC Nylon 의 결정성이 높음을 증명할 수 있었다.
MC Nylon 의 tensile strength 와 modulus of elasticity를 측정한 결과 molded Nylon보다 tensile strength 는 20% 증가하였고 modulus of elasticity 는 75% 증가 하였다. 이것은 높은 분자량과 결정성에 기인되는 것이다.