美国聚氨酯泡沫喷涂行业发泡剂从CFC-11到HCFC-141b的转.doc

2003中国聚氨酯行业整体淘汰ODS国际论坛论文集美国聚氨酯泡沫喷涂行业发泡剂从CFC-11到HCFC-141b的转变历程Robert Zimel(美国Gumser公司 远东销售经理)摘 要：介绍了美国在喷涂泡沫行业从CFC-11发泡剂过渡到HCFC-141b的实践指南和在此期间遇到的应用问题。蒙特利尔协议规定美国必须在1994年完成CFC-11的初步淘汰，同时确定发展中国家享有10年的宽限期。从CFC-11到HCFC-141b不像原来想象的能通过简单替代来完成。因为发泡剂同时也是溶剂，HCFC-141b与CFC-11的沸点不同，发泡剂的转换同时还要考虑到混合料的粘度变化、反应能力、物理稳定性和最终配方的密度。还必须开发新的催化剂和泡沫稳定剂（表面活性剂）。由CFC-11过渡为HCFC-141b导致组合料具有不同热量-粘度曲线，粘度更高，这就使喷涂时需更高的压力和稍高的温度。关键词：CFC替代；喷涂；聚氨酯；泡沫塑料；设备；发泡剂喷涂的聚氨酯泡沫在美国的增长和被广泛接受主要的原因是因为CFC-11（三氯氟甲烷）发泡的聚氨酯泡沫的优异的隔热性能。当发泡剂在气态时被截留在聚氨酯泡孔内时，聚氨酯泡沫对冷热的传递性最小化。除了真空外，喷涂的聚氨酯泡沫被公认为在低密度状态下（23 kg/m3）隔热性最好的材料,同时不吸水。1987年关于消耗臭氧层物质的蒙特利尔协议被确定为停止生产和使用消耗臭氧层的化学原料（如 CFC-11）的国际公约。协议规定美国必须在1994年完成CFC-11的初步淘汰，同时确定发展中国家享有10年的宽限期。在1994年的春季和夏季，使用HCFC-141b (1,1-二氯-1-氟乙烷)作为发泡剂的第一代聚氨酯泡沫喷涂配方被介绍给美国的泡沫喷涂应用者。1 发泡化学机理以及HCFC喷涂体系存在的问题喷涂用聚氨酯化学机理是非常复杂的（如下所示）。多元醇多异氰酸酯 聚氨酯热量热量发泡剂 气体膨胀气体膨胀产生聚氨酯泡孔催化剂控制反应速度表面活性剂维持泡孔的稳定阻燃剂进入泡沫整体图1 喷涂泡沫的收缩在发泡体系中不仅存在树脂(多元醇)与异氰酸酯的化学反应，还存在发泡剂从液态转变为气态、催化剂相互作用使泡沫上升和固化、表面活性剂在反应过程中保持泡孔稳定。只要改变配方中任何一种组分，整个化学反应都将改变。使用发泡剂HCFC-141b替代CFC-11，将同样改变发泡过程的物理化学反应状态，使喷涂后的聚氨酯泡沫的物理性能发生变化。美国的组合料供应商从1993年开始在可控条件下试验不同的喷涂配方。当时，很多人说HCFC-141b可能是CFC-11的一种理想的替代品。历史证明不是如此，因为缺乏对HCFC-141b转变和限制的必要准备和知识，当时，喷涂聚氨酯泡沫业在市场份额上遭受了极大的损失。两种发泡剂第一个主要不同之处是沸点。CFC-11的沸点较低，为23.7，泡沫的喷涂可以在比较低的温度下进行（43.348.8）。聚氨酯泡沫泡孔的内部压力可通过表面活性剂控制。HCFC-141b的沸点较高，为32.05，人们认为可通过提高喷涂时原料的温度轻易克服，经测试在喷枪口原料温度为54.460。然而，同时带来的泡沫内部压力增大，引起蠕变和收缩（见图1），导致在喷枪的两次喷涂之间泡沫分层和泡沫与基面的分层。而且，很多分层现象是在一段时间后泡沫的环境温度变化时才发现。另一个主要的不同点是HCFC-141b具有较强的溶剂效应，它常被用于电子产品和医用的清洁剂。当足够量的HCFC-141b混入聚氨酯泡沫原料体系中，以获得密度为39.2 kg/m3的泡沫时，由于HCFC-141b的侵蚀，聚氨酯泡沫泡孔会破裂。而且聚氨酯泡沫泡孔的被破坏，往往在经过一段时间以后才发现。CFC-11发泡体系制得的聚氨酯泡沫泡孔的闭孔率始终在95%，是真正的闭孔泡沫塑料产品。然而经过改良的HCFC-141b配方，泡沫的闭孔率仍然低于85%。如上所述，使用HCFC-141b作发泡剂的喷涂聚氨酯泡沫塑料虽然通过了最初的目检，其外观和性能随着时间推移和周围环境的变化开始退化，经过一段时间后会产生质量问题。随着时间的推移，其它的化学问题也显现出来。HCFC-141b的溶剂浓度差异将导致原料体系的组合聚醚变质。原料的保存期限由原来行业标准规定的1年缩短为69个月。情况变得很显然，组合料供应商必须采用新的多元醇来抵消HCFC-141b带来的不利性能。当多元醇供应商在研究开发新的多元醇的时候，组合料供应商很快意识到采用新发泡剂，需要开发用于组合料的新原料组分，以提供新的配方，使聚氨酯喷涂施工者继续开展喷涂业务。新多元醇需要新的催化剂来加速初始反应，产生更多的热量来使HCFC-141b气化。在这种放热更多、反应速度更快的反应中，又需要新的表面活性剂来保持聚氨酯泡沫泡孔稳定。除了化学原料问题外，这些新的组分给喷涂施工人员带来了一系列应用方面的问题。2 HCFC-141b在喷涂聚氨酯泡沫塑料中的应用组合料供应商方面的应用试验人员在喷涂试验中发现，使用HCFC-141b的新喷涂配方，反应非常充分，认为虽然不是很完美，但最初的缺点已经被克服了。但当时的这种观点后来被证明是太乐观了。多元醇和HCFC-141b的混合物要比原来的CFC-11发泡体系更加粘稠。CFC-11与以前的多元醇混合时，CFC-11是优良的稀释剂，大多数组合料的粘度在250 mPas。为了降低上面提到的HCFC-141b的溶剂效应对聚氨酯泡沫泡孔的副作用，用量较少。因此当时一些HCFC-141b发泡组合聚醚的粘度在25时为750 mPas左右，而泡沫的密度在46.4 kg/m3。这在聚氨酯喷涂中是不能被接受的。必须开发适用于HCFC-141b发泡体系的新(聚醚)多元醇，使之能承受HCFC-141b的溶剂效应，得到可满足泡沫喷涂业和最终用户要求的物理性能。由于更高的放热反应伴随着催化剂活性的巨大变化，当喷完一层再重复喷涂的时候，将导致泡沫分层（见图2），需向配方中加入Figure 3更多的表面活性剂以稳定聚氨酯泡沫的泡孔。泡沫喷涂有时与基面的粘接性很差，同样引起泡沫与保护性涂层的分层（见图3）。 图2 泡沫分层 图3 泡沫与保护性涂层的分层由于使用了过多的泡沫稳定剂，内部应力的原因使HCFC-141b发泡的聚氨酯泡沫收缩和膨胀。新开发的表面活性剂并不作为喷涂层间的隔离剂，也不对喷涂基面粘合力产生不利影响。此外，新的催化剂延长了不粘时间，改善了喷涂泡沫与基层的化学结合。HCFC-141b发泡体系中，与CFC-11相比，各种反应的变化使喷涂聚氨酯泡沫表面变得非常粗糙，象爆米花（见图4）。这样，相当不平整的表面将导致消耗较多的保护性涂层，并发产生更高的涂层费用，喷涂泡沫整体外观不佳，不被建筑商和最终用户接受。用于HCFC-141b发泡体系的新型催化剂已被开发，通过调节泡沫上升和不粘时间，使表面更光滑。图4 最初的HCFC-141b喷涂泡沫表面粗糙图5更高的沸点和相关的较高放热温度导致另一个应用方面的问题：不能把单层HCFC-141b喷涂做得象CFC-11发泡喷涂泡沫一样厚。用CFC-11作为发泡剂，一个熟练施工人员可很容易地喷一层3855 mm厚的泡沫并使相应的表面适合涂保护性涂层。但用HCFC-141b作为发泡剂，单层喷涂的最大厚度是25 mm。由于放热反应产生较多热量，泡沫层如更厚，容易产生分层、变色和表面外观不良。增加喷涂次数以获得喷涂厚度，意味着增加劳动量和产生更高的泡沫密度，因此增加了工作成本。另外，当喷涂者在不同温度的基面上喷涂时，需注意不均匀反应的问题。例如从阳光照射的区域喷涂移到阴凉的地方喷涂后，HCFC-141b喷涂泡沫反应特性就变化了。HCFC-141b喷涂泡沫体系对基面和环境温度的变化非常敏感，原因还是因为HCFC-141b的沸点更高。添加水作共发泡剂，可使一些HCFC-141b发泡聚氨酯配方更加稳定，但降低了隔热系数，有可能使喷涂聚氨酯相对于市场上其它隔热产品的市场优势丧失。对北美的喷涂泡沫操作人员而言，1994到1995年是他们希望能够忘却的时间。这是因为在工程完成36个月后，产生很多很多的质量问题。3 喷涂设备在所推荐的原料储存温度（25）和较平坦的热量-粘度曲线，HCFC-141b泡沫喷涂体系具有更高的粘度。这就相对于CFC-11发泡体系要求更高的原料加热温度和喷涂压力。具有高压设备的工程承包商可以在4.14.8 MPa的压力下喷涂HCFC-141b体系，但泡沫物理性能不能达到组合料供应商在喷涂压力为6.98.3 MPa时的试验结果。此外，需要更高的喷涂温度（5460），才能把HCFC-141b由液态转化为气态。北美喷涂泡沫操作者1987年开始把设备升级为具有更高压力和更高加热能力的设备。美国Gusmer公司向用户介绍了FF-1600（见图5）和H-2000系列喷涂设备，配备GX-7喷枪（见图6）。这些设备可同时满足用户喷涂CFC-11或HCFC-141b发泡原料体系的要求。用两种原料体系测试表明，如果压力增加到6.98.3 MPa，可看到两个重大的优势，由喷嘴产生细微的液滴。 图图65 FF-1600喷涂设备 图6 GX-7喷枪第一、取决于在喷涂压力时不同材料的粘度，存在一个压力区使原料组分以最佳比例喷涂到基面。如果压力太小，较大的原料滴从喷涂面流出的百分比增大；如果压力太高，小原料滴消失在周围环境中的百分比增大，象过喷一样。然而，具体喷涂压力取决于不同的原料配方。总之，应该在6.98.3 MPa范围内。第二、在同一个压力区间内，混合压力增高，泡沫的物理性能得到提高。当在6.98.3 MPa压力范围内，耐压性能、闭孔率和密度均得到改善。这两个变化意味着产出率提高（每平方米用多少原料），这使北美的应用者意识到使用高压设备的好处，即使是在此行业过渡到HCFC-141b之前。必须注意，即使是北美今天的配方，如果以超过原料商推荐的压力进行喷涂施工，仍将导致过喷及由此引起的喷涂效率降低的问题，同时导致因为过分混合引起的泡沫物理性能的降低；低于原料商推荐的压力喷涂，将导致过高的泡沫密度、降低产出率和因混合不充分引起的泡沫物理性能的降低。4 结束语不管参与喷涂聚氨酯泡沫市场所有方方面面人士，包括聚氨酯多元醇、催化剂、表面活性剂和组合料的供应商或是操作者走过了多少漫长曲折的路，用HCFC-141b 作发泡剂的喷涂体系遇到的问题可以说是已经被克服。今天北美的喷涂泡沫应用者可以利用正确的原料体系、高压喷涂设备及适当的培训，喷涂用HCFC-141b为发泡剂的聚氨酯硬泡体系。当需要外覆盖保护性涂层时，也可达到平滑的外观、优良的工作产出率，和在原料商提供的质保期内完成任务。英文题目：The Transition of Spray Applications from CFC-11 Blowing Agents to HCFC-141b in the United StatesThe Transition of Spray Applications from CFC-11 Blowing Agents to HCFC-141b in the United StatesRobert Zimel(Gusmer Corporation)ABSTRACTIntention: The Montreal Protocol on Substances that Deplete the Ozone Layer was adopted in 1987 as an international treaty to eliminate the production and consumption of ozone-depleting chemicals, with developing countries benefiting from a ten-year grace period. It was decreed that the United States would make this transition in 1994. This paper presents a practical guidebook to the transition from CFC-11 blowing agent to HCFC-141b in spray foams and their application problems during this transition in the United States. Chemistry: The change from CFC-11 to HCFC-141b was not accomplished by simple substitution as originally thought. Since CFC-11 is a solvent as well as a blowing agent, considerations to the viscosity changes of the polyol blend had to be made as well as reactivity, physical stability and ending formulation density. As new polyols were developed to offset the adverse physical and chemical changes, new catalysts and cell stabilizers (surfactant) had to be developed. Application: The difference in the boiling point of HCFC-141b (change from liquid to gas) required application considerations not necessary with CFC-11 blown formulations. In addition, the transition through development of new polyols, catalyst and cell stabilizers resulted in many lost application man-hours as unacceptable PUF was removed from the job-site surfaces. Equipment: The change from CFC-11 to HCFC-141b resulted in higher viscosity polyol blend with different heat/viscosity curves. This necessitated spraying at higher pressures and slightly higher temperatures. The growth and acceptance of sprayed polyurethane foam in the United States was due in large part to the excellent insulation value of CFC-11 (trichlorofluoromethane) blown polyurethane foams. This blowing agent, when trapped as a gas within the polyurethane cell, offered minimal transfer of heat or cold. Spray foam was advertised as the best insulation known other than a vacuum, at a very low-density 32 k/m3 (2 lb/f3) and did not absorb water as blanket insulations do. The Montreal Protocol on Substances That Deplete the Ozone Layer was adopted in 1987 as an international treaty to eliminate the production and consumption of ozone-depleting chemicals such as CFC-11. It was decreed that the United States would make the initial transition from CFC-11 in 1994, while defined developing countries would benefit from a ten-year grace period. During the spring and summer of 1994, United States spray foam applicators were introduced to the first production formulations of sprayed polyurethane foams with HCFC-141b (1,1-dichloro-1-fluoroethane) as their blowing agent.CHEMISTRY Spray Polyurethane chemistry is very complex (Figure 1). Not only is the reaction between the base resin or resins and isocyanate taking place, but the blowing agent is changing from a liquid to a gas, the catalysts are interacting to cause rise and tack free times to meet the chemists requirements and the surfactant is holding the cell together during the reaction. Change one component and the entire reaction will change. This new Blowing Agent, HCFC-141b changed the reaction profile as well as the physical properties of the end-result, sprayed polyurethane foam. In 1993, blenders began testing spray formulations under controlled conditions. During this period, many said that HCFC-141b could be a drop-in replacement for CFC-11. History has shown this was not the case, and the spray foam industry suffered significant loss of market share due to lack of preparedness and knowledge relating to the transition and limitations of HCFC-141b.Figure 1The first major difference was in the boiling point of the two blowing agents. With CFC-11s low boiling point of 23.7 (74.6F), spray foam was sprayed at low temperatures, 43.348.8 (110120F). Internal stresses upon the polyurethane cell were well known and controlled with cell stabilizers (surfactants) that had been available for many years. HCFC-141bs higher boiling point of 32.05 (89.7F) was thought to be easily overcome by spraying with higher material temperatures, 54.460(130140F), when measured at the spray gun. However, this induced internal stresses in the spray foam that caused creeping and shrinkage (Figure 2). The results were delamination between spray passes and delamination from substrates. Many of these delaminations were not seen until the spray foam had been subjected to ambient temperature changes over time. Figure 2The next major difference was the solvent strength of HCFC-141b. Used as a cleaner in the electronics and medical industry, when blended into polyurethane foam systems in sufficient quantity to result in acceptable densities, 39.2 kg/m3 the polyurethane cell broke down as the HCFC-141b attacked it. This degrading of the polyurethane cell was not seen until some time had passed after the application. Closed cell content for CFC-11 blown systems was consistently 95%, truly a closed cell product. While newer HCFC-141b formulations have improved this number, it remains less than 85%.As noted, both these issues occurred over time. Therefore sprayed polyurethane foam with HCFC-141b was applied, passed initial visual inspections, and began to degrade and fail with time and ambient temperature changes. Other chemistry problems also began to show with the passage of time. The difference in solvent strength of HCFC-141b caused degrading of the Polyol side of the chemical system. Shelf life was shortened to 69 months from the industry standard of 1 year. It became obvious to the material blenders that new base resins were required to offset the adverse properties of HCFC-141b. As the resin suppliers worked to develop new resins, the system blenders soon realized that the new blowing agent was going to require all newly developed components in the Resin side of the sprayed polyurethane foam to give formulations that would allow the applicator to continue in business. New resins required new catalyst to give a faster initial reaction, generating more heat (exotherm) to boil the HCFC-141b. The new catalysts required new surfactants (cell stabilizers) to hold the cell together during this hotter, faster reaction. In addition to the chemical problems, these new components led to application problems for the spray applicator.APPLICATIONUnder controlled spray tests performed by applicators on behalf of the system blenders, the new spray formulations with HCFC-141b processed adequately. Although not perfect, it was initially felt that the shortcomings were solvable. This attitude proved to be overly optimistic.The blend of resins and HCFC-141b was much more viscous than the old CFC-11 systems. CFC-11 was an excellent diluent for the previous resins used, with the viscosity of most polyol blends at 250 mPas. Less HCFC-141b was used to minimize the degrading to the cell because of the solvent action mentioned prior. Therefore the viscosity of some new systems were 750 mPas at 25 (75F) or greater and the system densities were still 46.4 k/m3 (3 lb/ft3). This was unacceptable to the spray foam industry. New resins had to be developed that withstood the solvent action of the HCFC-141b and offered the physical properties required by the spray foam industry and its end-users.Adding extra surfactants to the formulation to hold the cell together due to the higher exothermic reactions combined with significant changes in the catalyst reaction profile, caused the foam to delaminate (blister) where one spray pass went over another (Figure 3). Adhesion to substrates that spray foam normally bonded well to was poor, also causing delamination including the bonding of the protective coatings to the spray foam (Figure 4). This action, due to excessive surfactant, was masked by the fact that HCFC-141b spray polyurethane foam was shrinking and growing due to internal stresses as discussed prior. New surfactants were developed that did not act as release agents between spray passes and did not adversely impact adhesion to spray substrates. In addition, new catalysts extended the “tack free” time so the spray foam chemical bond to the substrate was improved. Figure 3 Figure 4The significant changes in reaction profile caused the applied HCFC-141b spray foam surface to become very rough, like popcorn (Figure 5). This extremely uneven surface resulted in excessive consumption of protective coating; subsequent higher costs to the applicator in coating usage and an overall appearance that was unacceptable to the building owner or end-user. New catalyst were developed that allowed for a smoother profile by adjusting the rise and tack fee times. Figure 5The higher boiling point of HCFC-141b and the subsequent higher exothermic temperatures lead to another application problem. The inability to make single passes as thick as with CFC-11 blown systems. With CFC-11 as the blowing agent, it was not unusual for a top spray applicator to make a single pass of 3851mm (12 in) and have the resultant surface acceptable for coating. With HCFC-141b systems, 25mm (1 in) was the maximum spray thickness. Any thicker and delamination, discoloration and poor surface profiles due to the high exothermic heat occurred. Added passes meant added labor and a higher “in-place” spray foam density, thereby increasing the job costs. In addition to the application problems noted, as the applicator sprays upon a substrate that has different temperatures, such as when you move from a sunny area into the shade and then out again, the reaction profile of HCFC-141b spray foam changes. HCFC-141b spray foam is very sensitive to substrate and ambient temperature change, due again to the higher boiling point of the new blowing agent as noted earlier.The addition of water as a co-blowing agent has given some HCFC-141b polyurethane formulations more stability, but lowered the R factor thereby minimizing one of the major marketing tools of sprayed polyurethane foam against other insulation products.For the spray foam applicator in North America, 1994 and into 1995 was a time they wish to forget. This was due to the many problems not being noticed until 3 6 months after applications were completed. EQUIPMENTThe HCF-141b spray systems had higher viscosities at recommended material storage temperature (25C) and flatter heat vs. viscosity curves. This required spraying at higher material temperatures and higher pressures than required by CFC-11 systems. Contractors with “high pressure” equipment that sprayed at 4148 bar (600700 psi) could still spray HCFC-141b spray systems, but the physical properties did not match those developed by the material system blenders during tests using spray pressure of 6983 bar (1,0001,200 psi). In addition, higher spray temperatures of 54.460(130140F), as mentioned prior, were now required to change the HCFC-141b liquid blowing agent into an expansive gas.Figure 6For the North American spray foam applicator, this change to equipment with higher pressure and higher heat capability was started in 1987. Gusmer introduced its FF-1600 (Figure 6) and H-2000 series proportioners, along with the GX-7 (Figure 7) spray gun. These units met the requirements of the applicator for both in-plant and contracting applications spraying CFC-11 systems and then HCFC-141b systems. Testing with both systems has shown that if the spray pressure was increased to 6983 bar (1,0001,200 psi) two significant advantages were found with the slightly smaller material droplet produced at the spray tip.Figure 7First, depending on the material viscosity at spray pressure, there was a pressure window where an optimum percentage of the chemical system sprayed was propelled to the substrate. Too little pressure and an increased percentage of the larger droplets fell out of the spray pattern. Too much pressure and an increased percentage of the smaller droplets were lost to the ambient as over-spray. While this number did vary depending on the spray system formulation, in general it was in the 6983 bar (1,0001,200 psi) range.Second, the physical properties were improved as the mixing pressure was increased within the same pressure window. Compression properties, closed cell content and density all improved when spraying within the 6983 bar (1,0001,200 psi) window.These two changes resulted in improved job yield (kilos used per meter2), which led the North American applicator to realize the advantage of higher spray pressures even before the industry transitioned to HCFC-141b blowing agents.It must be cautioned, that even with todays formulations in North America, spraying at pressures above those recommend by the material system supplier will result in not only excessive over-spray and it subsequent decrease in job yield, but can cause degrading of the spray foam physical properties by