聚氨酯技术对家电行业持续发展的贡献

聚氨酯技术对家电行业持续发展的贡献

中村富士夫            焦建清，叶利

（陶氏化学日本公司）                     (陶氏化学中国公司）

摘  要：自1987年蒙特利尔议定书生效以来，硬质聚氨酯泡沫工业尤其是家电行业积极开展CFC的废止工作。冰箱制造商及聚氨酯原材料供应商做了大量的工作来寻找CFC-11的替代发泡剂。替代发泡剂的选择因地而异：在北美，HCFC-141b由于易操作及低导热系数等特点被广泛使用；欧洲由于成本及环保的原因，主要使用环戊烷及其与异戊烷或异丁烷的混合物；至于亚太地区，由于行业结构及法规的多样性[1]，替代形势则较为复杂。除这些外部因素外，冰箱制造商还必须考虑许多与自身业务有关的内部因素，如安全操作、生产效率、较少的资金投入、产品的长期质量及应用新发泡剂的灵活性。

作为一个全球性的聚氨酯原材料供应商，陶氏化学公司开发了针对各种发泡剂的硬质聚氨酯冰箱泡沫体系，并根据各地区冰箱客户的不同要求提供最佳的解决方案。

详细阐述了陶氏化学公司开发的各种替代发泡剂技术，同时通过模拟计算清楚地表明泡沫导热系数(K值)、二氧化碳排放量的减少以及典型冰箱的整体能耗之间的关系，快速脱模体系及低密度体系通过制造过程中能源消耗和原材料的降低同样对全球环境产生正面影响，由此表明聚氨酯技术在中国及其它发展中国家冰箱行业的持续发展中对全球环境的贡献。

关键词：发泡剂；CFC替代；聚氨酯；泡沫塑料；家用电器

1  概述

自1987年蒙特利尔议定书生效以来，硬质聚氨酯泡沫工业尤其是家电行业积极开展CFC的废止工作。冰箱制造商及聚氨酯原材料供应商做了大量的工作来寻找CFC-11的替代发泡剂。替代发泡剂的选择因地而异：在北美，HCFC-141b由于易操作及低导热系数等特点被广泛使用；欧洲由于成本及环保的原因，主要使用环戊烷及其与异戊烷或异丁烷的混合物；至于亚太地区，由于法规、市场结构和冰箱设计的多样性，替代形势则较为复杂。不管怎样，环戊烷因其在环境和成本方面的优势被普遍使用。表1列出了各种替代发泡剂的物理特性及环境性质如ODP和GWP等。  

表1   各种替代发泡剂特性比较

发泡剂 名称	分子式	沸点 ℃	气体热导率(25℃) mW/(m·K)	蒸气压(20℃) kPa	ODP	GWP	可燃 性	大气生命时间 (年)
HCFC-141b	CH3CCl2F	32.1	9.8	69	0.11	630	低	8~10
环戊烷	C5H10	49.5	12.6	34	0	11	高	0.05
异戊烷	C5H12	28	13.8	80	0	11	高	0.03
异丁烷	C4H10	－12	15.9	299	0	5	高	0.02
HFC-245fa	CHF2CH2CF3	15.3	12.2	124	0	820	低	7~10
HFC-134a	CH2FCF3	－26	14.3	562	0	1300	无	14~16
二氧化碳	CO2	－78	16.3	5655	0	1	无	120~200

从表1中可以很显然地看出，在HCFC-141b废止后(许多国家计划在2003年)，所有的替代发泡剂将不含ODP值，因而地球温室效应(GWP)将成为发泡剂选择的下一个重点。虽然碳氢类及碳氟氢类发泡剂都被认为是未来10年主要的替代发泡剂，碳氢类发泡剂在地球温室效应上有优势。但是如果两类发泡剂制得的泡沫导热系数差异很大的话，由于使用低K值泡沫体系的冰箱能耗较低，二氧化碳排放量减少，地球温室效应的差异将会得到部分补偿。  

众所周知，在中国因能源消耗而产生的二氧化碳排放量是相当高的(见图1)，考虑到中国的高速发展，如何在能源的供求两方面减少二氧化碳的排放成为改善全球环境的迫切任务。本文的目的旨在就这两类主要替代发泡剂技术对全球环境的影响进行详细的阐述。在本文中，我们同时也从以下三个方面简要说明聚氨酯技术对全球环境的贡献：

1)     通过节约能源减少二氧化碳的排放

2)     通过减少原材料的使用而保护资源

3)     通过生产效率改善而节约能源及资源

                            内环－GDP   外环－因产能而排放的CO2

图1  全球各地区GDP与二氧化碳排放量比例(1998年)

   资料来源： Energy and Economy Statistics (IEA, 2001)

目前亚洲国家特别是中国能源紧缺状况日趋严重，因而控制二氧化碳的排放显得尤为重要。在本文中，我们以低K值泡沫体系为例来模拟二氧化碳排放量的减少。

2  实验部分

所有实验结果都是通过聚氨酯硬泡的标准测试方法测得：

密度: ASTM D 1622

压缩强度: ASTM D1621

导热系数(K值): ASTM C518

用于测试物性的泡沫由可操作碳氢发泡剂及低沸点发泡剂的高压发泡机在如图2所示的标准模具中制备，本文中介绍的所有泡沫体系都已用于实际生产或至少已在生产线上经过验证。

3  结果与讨论

3.1  碳氢类发泡体系

我们在实验室开发和评估了下列六个发泡体系：

-            普通HCFC-141b发泡体系A (参考体系)

-            普通环戊烷发泡体系B

-            低K值环戊烷发泡体系C

-            快速离模环戊烷发泡体系D

-            低密度环/异戊烷混合发泡体系F  

-            低密度环戊烷/异丁烷混合发泡体系E

图2   标准模具

所有这些体系目前或正在冰箱生产线上正常使用，或至少已在客户的生产线上经过验证确认。这些体系的泡沫物性如表2所示，从表2中我们可以得出以下结论：

1)     普通环戊烷发泡体系的泡沫K值比普通HCFC-141b发泡体系高11.6%；

2)     低K值环戊烷发泡体系的泡沫K值仍比HCFC-141b发泡体系高6.3%，但比普通环戊烷发泡体系改进了4.7%；

3)     快速离模环戊烷发泡体系在同等试验条件下的离模膨胀值比普通环戊烷发泡体系改进了64%；

4)     使用环/异戊烷或环戊烷/异丁烷混合发泡技术，可以分别降低泡沫密度4%和7%。

表2   碳氢发泡体系的泡沫物性比较

	HCFC-141b 参考体系	普通环戊烷体系	低K值环戊烷体系	快速离模 环戊烷体系	环戊烷/异丁烷体系	环/异戊烷 体系
多元醇	A	B	C	D	E	F
异氰酸酯	PAPI* 27	PAPI 27	PAPI 27	PAPI  27	PAPI 27	PAPI 27
拉丝时间/s	45	43	34	38	43	45
模塑密度/kg·m－3	35	36	37	36	33.5	34.5
10%压缩强度/kPa	145	150	170	150	140	145
24℃泡沫K值/mW·(m·K)－1	19	21.2	20.2	21.1	21.5	21.5
离模膨胀/%	2	2.2	2.5	0.8	1.8	1.6

    注：*陶氏化学公司商标。

3.2  碳氟氢类(HFC)发泡体系

同碳氢类发泡体系一样，我们在实验室进行下列发泡体系的开发和评估：

-     普通HCFC-141b发泡体系A (参考体系)

-     普通HFC-245fa发泡体系G

-     低K值HFC-245fa 发泡体系H

-     普通HFC-134a发泡体系I

-     低K值HFC-134a发泡体系J

泡沫物性如表3所示，从表3中我们可以得出以下结论：

1)        普通HFC-245fa发泡体系的泡沫K值比参考体系A高出5%左右，但密度可降低11.4%，同时脱模膨胀可改善75％( 从2％降为0.5％)；

2)        低K值HFC-245fa发泡体系H的泡沫K值比普通HFC-245fa体系改进5%左右，其实测数值(19.1mW/m·K)与参考体系A非常接近(19.0mW/m·K)；  

3)        普通HFC-134a发泡体系I的K值比参考体系高15.3%；

4)        与普通HFC-134a发泡体系相比，低K值HFC-134a发泡体系J的泡沫K值改进了3.2%。

表3  碳氟氢类(HFC)发泡体系的泡沫物性比较

	HCFC-141b 参考体系	普通HFC-245fa体系	低K值HFC-245fa体系	普通HFC-134a体系	低K值HFC-134a体系
多元醇	A	G	H	I	J
异氰酸酯	PAPI 27	PAPI 27	PAPI 27	PAPI 27	PAPI 27
拉丝时间/s	45	33	33	40	32
模塑密度/kg·m－3	35	31	33.5	33.5	34
10%压缩强度/kPa	145	125	155	130	140
泡沫K值/mW·(m·K)－1	19	20.1	19.1	21.9	21.2
离模膨胀率/%	2	0.5	1.7	0.7	1.2

3.3  二氧化碳排放减少量的模似

3.3.1  假设

不用说，上述3.1和3.2部分的结果仅仅只能代表泡沫性能可能改善的范围，这些数据将随着配方和发泡生产条件的不同而有所不同。但是为了简化计算，我们决定用这些数据来模拟二氧化碳排放量的减少。在冰箱工业，我们都知道冰箱能耗改善百分率是泡沫导热系数改善百分率的一半，举个例子来说，如果导热系数改善了10％，那么冰箱能耗将改善5％。当然这个比率将随着冰箱设计和压缩机性能的不同而不同。但是不管怎样，我们决定用这个比率来模拟。在计算时我们还作了以下一些假设：

-          在中国用普通环戊烷体系生产的冰箱的平均容积和能耗分别为200L和350kWh/a；

-          在中国每消耗1 kW能量将释放0.65 kg二氧化碳；

-          中国每年冰箱产量为1500万台；

-          冰箱平均寿命为10年；

-          在冰箱寿命期内能耗无变化(10年)。

本文以下部分的模拟计算都基于上述假设的基础上。

3.3.2  二氧化碳的排放

表4所列的是普通环戊烷体系与各种低导热系数发泡体系二氧化碳排放减少量的比较。累积数据这一行表示当在中国生产的冰箱(2003～2013年)全部转换成所在列的发泡体系时的二氧化碳总的排放减少量。从表4我们可以明显的看出，在中国从2003至2013年二氧化碳累积排放减少量是一个不容忽视的量。而且随着今后10年内技术的不断发展这必将进一步加速减少二氧化碳的排放。

表4  低导热系数发泡体系二氧化碳的排放减少量

发泡体系	普通环戊烷体系	低导热系数 环戊烷体系	普通HFC-245fa体系	低导热系数 HFC-245fa体系
泡沫导热系数/mW·(m·K)－1	21.2	20.2	20.1	19.1
导热系数降低率/%	标准	4.7	5.2	10.0
单台冰箱能耗降低率/%	标准	2.4	2.6	5.0
单台冰箱每年能耗降低量/(kW·h/a)	标准	8.4	9.1	17.5
单台冰箱每年二氧化碳排放减少量/(kg/a)	标准	5.5	5.92	11.4
所有新生产的冰箱二氧化碳排放减少量/(t/a)	标准	81,900	88,800	171,000
2003~2013年CO2累积排放减少量(中国)/t	标准	4,504,500	4,884,000	9,405,000

3.3.3  环戊烷体系和HFC-245fa体系比较

在选择发泡剂时必须考虑的一个问题即环境因素特别是温室效应。从表4可以看出，即使是普通的HFC-245fa体系，其二氧化碳的排放量也比低导热系数的环戊烷体系低。更不用说低导热系数的HFC-245fa体系了，其二氧化碳的排放减少量是其它体系的二倍。但是另外一方面，从表1中可以看出，与环戊烷相比HFC-245fa具有较高的温室效应。现在我们以200L的冰箱为标准，将各种发泡剂对温室效应的影响以二氧化碳的量来表示(表5)。在表5中，如果冰箱泡沫中所有的发泡剂都释放至空气中，那么其影响可以用二氧化碳的量来计算。

现在我们通过比较两种低导热系数体系(环戊烷和HFC-245fa)的二氧化碳的排放量来评估它们对温室效应的影响，冰箱的寿命为10年。

-          由于HFC-245fa体系的能耗比环戊烷体系的低，因此与环戊烷体系相比，在这方面其二氧化碳的排放量可减少(11.4 –5.5)kg×10年＝59kg 。

-          但是如果所有的发泡剂都释放至空气中的话，HFC-245fa体系的二氧化碳释放当量将比环戊烷体系多205.7kg－2.76kg ＝202.9kg。

根据上述模拟，环戊烷看起来好像比HFC-245fa对环境更有利些，但是如发泡剂已在泡沫中分解而没有完全释放至空气中的话，情况必将有所不同。  

表5  发泡剂对温室效应的影响以二氧化碳的量来表示

	普通环戊烷体系	低导热系数环戊烷体系	普通HFC-245fa体系	低导热系数HFC-245fa体系
模塑密度/kg·m－3	36	37	31	33.5
每台200L冰箱泡沫用量/kg	7	7.2	6	6.5
单冰箱泡沫的发泡剂量/kg	0.35	0.40	0.57	0.77
发泡剂的相对分子质量	70	70	134	134
发泡剂量/mol	5.0	5.7	4.3	5.7
GWP	11	11	820	820
对应的二氧化碳的量/mol	55.0	62.7	3526	4674
对应的二氧化碳的量/kg	2.42	2.76	155.1	205.7

3.3.4  通过降低泡沫密度节约原材料

当我们考虑家电工业持续发展的时候，自然资源的节约是另外一个主要的因素。我们可以通过开发低密度体系来降低生产泡沫的原料聚醚、异氰酸酯、催化剂、硅油的使用量。正如我们前面提到的那样，如果我们用环/异丁烷体系来替代目前的普通环戊烷体系的话，单台冰箱泡沫重量可降低7％，那么整个中国每年可节约聚氨酯原材料7350t (7kg×1500万台×0.07)。但是考虑到对泡沫导热系数的负面影响和操作异丁烷需投入一定的资金，那么其益处就不怎么明显。

3.3.5  通过生产效率改善来节约资源

通过对生产效率改善，聚氨酯技术可对资源的节约作出贡献，一般来说泡沫后膨胀从2％降至0.8%，就意味着脱模时间可降低20％至40％。这不仅能降低能耗而且能够减少人力和资金的投入。总的来说，通过对自然资源的节约，它能对环境的改善带来一定程度的贡献。但是这是很难评估的，因为其影响程度主要取决于工厂的设计和生产的方式。

4  结论  

通过使用先进的原材料及配方技术，可以用较为经济的方式开发出很低导热系数的各种替代发泡剂体系，由此制得的泡沫具有极佳的导热系数和良好的工艺性。这样的泡沫由于使用了无ODP的发泡剂并通过较好的能效减少了二氧化碳的排放而使生产的冰箱更加环保。在另一方面，我们也开发了快速脱模（降低生产周期）泡沫体系和低密度泡沫体系，这些使我们在冰箱制造过程中节约了能源和使用较少的原材料（自然资源）。

陶氏化学公司针对市场中现有的各种发泡剂开发了低导热系数的泡沫体系，这些泡沫体系可通过较低的冰箱能耗而减少二氧化碳的排放，二氧化碳排放量的减少可通过现有的一些工业数据进行模拟计算。快速脱模体系及低密度体系通过制造过程中能源消耗和原材料的降低同样对全球环境产生正面影响。通过给客户提供最佳的解决方案，聚氨酯技术可以促进中国的冰箱工业持续发展。      

致谢

对于陶氏化学在Freeport，Meyrin及亚太地区的研发人员在本文撰写过程中给予的协助和支持表示衷心的感谢。

参考文献

1  Chang V, Jiao J, Ye R, Rigid Appliance Foams – Current and Future Technologies in Asia Pacific. Utech Asia 2002

  

作者简介：

中村富士夫先生 毕业于日本庆应义塾大学并获有机化学硕士学位，他于1984年加入陶氏化学日本有限公司聚氨酯研发部门，过去19年在聚氨酯的许多应用领域从事相关技术工作，目前为聚氨酯硬泡及CASE的亚太区技术及研发经理。

焦建清先生 于1991年毕业于上海交通大学高分子材料专业，毕业后在冰箱厂从事发泡技术工作多年，1997年加入陶氏化学（中国）有限公司，主要负责家电行业聚氨酯产品的配方开发及技术服务工作，目前为聚氨酯产品应用主任。

叶利先生于1988年毕业于江苏化工学院高分子材料专业，同年进入苏州香雪海电器有限公司从事聚氨酯发泡工作，1995年加入苏州三星电器有限公司担任化工工艺主管，1997年加入陶氏化学（中国）有限公司，主要负责家电行业聚氨酯产品的技术服务及开发工作。目前为聚氨酯产品技术主任。

Polyurethane Technologies Can Contribute to Sustainable Growth of Appliance Industry

Jeffrey Jiao Jian-Qing       Ricky Ye Li              Fujio Nakamura

(Dow Chemical China)   (Dow Chemical China)   (Dow Polyurethanes Japan Ltd)

ABSTRACT

Since the Montreal Protocol in 1987, rigid polyurethane foam industries especially rigid appliance industry has proactively implemented CFCs phase-out program. Refrigerator manufacturers and the PU raw material suppliers have done substantial work to replace CFC-11 with alternative blowing agents. The choice of blowing agent depends on the regional requirements.  In N.A., HCFC-141b has been commonly used due to its easy handling and low thermal conductivity.  Cyclopentane and its mixtures with isopentane or isobutane are popular in Europe due to the cost and environmental reason.  In Asia Pacific, the situation is somewhat complicated because of the industry structure and local regulatory issues[1]. In addition to these outside factors, each refrigerator manufacturer must consider business related matters including safe operation, effective production process, less capital investment, long term quality of the products, and flexibility of the plant to apply new blowing agent when required.

As a global PU raw material supplier, The Dow Chemical Company has developed and supplied rigid polyurethane appliance foam systems based on different blowing agents to offer the best technical solutions to customers in all regions.  

The objective of this paper is to give a detailed view of these blowing agents, and to illustrate the technical options for each blowing agent. This paper also describes a simulation which clearly defines the relationship between foam thermal conductivity (k-factor), CO2 emission saving and the overall energy consumption of a typical refrigerator. Fast demold systems and low-density foam systems can also contribute to global environment through energy and raw materials reduction. It clarifies how PU technology can contribute to global environment to secure sustainable growth of refrigerator industry especially in China and other developing countries.

INTRODUCTION

Since the Montreal Protocol in 1987, rigid polyurethane industries especially rigid appliance industry has proactively implemented CFC phase-out program.  Refrigerator manufacturers and the PU raw material suppliers have done substantial work to replace CFC-11 with alternative blowing agents. The choice of blowing agent depends on the regional requirements.  In N.A., HCFC-141b has been commonly used due to its easy handling and low thermal conductivity.  Cyclopentane and its mixtures with isopentane or isobutane are popular in Europe due to the cost and environmental reason.  In Asia Pacific, the situation is somewhat complicated because of its diversified regulatory requirements, market structures and refrigerator designs.  However, cyclopentane has been the most popular blowing agent because of its environmental and cost advantages.   The physical properties and environmental measures such as ODP and GWP of each blowing agent are shown in Table 1.

In Table 1, it is obvious that after phasing out of HCFC-141b, which is planned in this year in most of countries, all the blowing agents will be ODP free, thus the GWP is the next focus in selection of blowing agent.  Although both hydrocarbons and HFCs are considered to be major blowing agents in the first decade of 21st century, hydrocarbons have advantage on this factor. But if there is big gap in foam thermal conductivity between these two types of blowing agents, the GWP difference should be compensated by less CO2 generation by its low energy consumption.

Table 1.  Properties of blowing agents

Blowing agent	Formula	Boiling Point (℃)	Gas k-factor @25℃(mW/mK)	Vapor pressure @ 20℃ (bar)	ODP	GWP	Flammability	Atmospheric life time (yrs)
HCFC-141b	CH3CCl2F	32.1	9.8	0.69	0.11	630	Low	8~10
Cyclo-pentane	C5H10	49.5	12.6	0.34	0	11	High	0.05
Iso-pentane	C5H12	28	13.8	0.8	0	11	High	0.03
Iso-butane	C4H10	-12	15.9	2.99	0	5	High	0.02
HFC-245fa	CHF2CH2CF3	15.3	12.2	1.24	0	820	Low	7~10
HFC-134a	CH2FCF3	-26	14.3	5.62	0	1300	None	14~16
CO2	CO2	-78	16.3	56.55	0	1	None	120~200

It is well known that CO2 emission for energy is high in China (Figure 1). Considering China’s rapid growth rate, saving of CO2 emission in both supply and demand sides of energy is an urgent issue for global environment. The objective of this paper is to give a clear picture regarding contributions of polyurethane technologies to global environment by using these two major blowing agents.   In this paper, we also tried to figure out contributions of PU technologies on the following three aspects.

4) Reduction of CO2 emission through energy saving

5) Resource conservation by applying less raw materials

6) Energy and resource saving through effective production

Among these three aspects, CO2 emission should be most critical one considering current energy sources in Asian countries especially in China.  In this paper, we simulated how much CO2 emission could be save by developing low thermal conductivity foams.      

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1－U.S.A.   2－EU   3－PRC   4－Russia   5－Japan   6－Rest of world

Figure 1.  Global GDP and CO2 emission (1998)

Source: Energy and Economy Statistics (IEA, 2001)

EXPERIMENTAL

All the experimental results were obtained by the following standard test methods of polyurethane rigid foams:

Density: ASTM D 1622

Compressive strength: ASTM D1621

Thermal conductivity (k-factor): ASTM C518

All the foams were prepared by high-pressure injection foaming machines, which were modified for hydrocarbon and LBBA (Low boiling point blowing agent) handling.  The foam samples for physical property testing and basic processing check were obtained from standard molds such as Figure 2.  All systems introduced in this paper were practiced in actual productions or at least confirmed the performance through line trials.

Figure 2.  Standard mold

RESULTS AND DISCUSSIONI.  Hydrocarbon systems

We developed and evaluated the following six foam systems in our laboratories;

-   Conventional HCFC-141b system (reference)

-   Conventional cyclopentane system

-   Low k-factor cyclopentane system

-   Fast demold cyclopentane system

-   Low density cyclopentane/isopentane system

-   Low  density  cyclopentane/isobutane system

All these systems are currently used in actual refrigerator productions, or at least, confirmed the performance through production trials at our customers.  The foam performances of the systems are shown in Table 2.  From Table 2, the following results were obtained:

5) Compared to HCFC-141b, conventional cyclopentane system showed an 11.6% worse foam k-factor.

6) Low k-factor cyclopentane system showed still a 6.3% worse k-factor than HCFC-141b system, but a 4.7% improved value than conventional cyclopentane system.

7) Fast demold cyclopentane system showed a 64% (0.8% vs. 2.2%) better post expansion value than conventional cyclopentane system.

8) By applying cyclopentane/isopentane and cyclopentane/isobutane mixed blowing agents, we could reduce foam density by 4% and 7% respectively.

Table 2.  Foam performances of hydrocarbon systems

Blowing agent	HCFC-141b	CP, Conv.	CP, Low K	CP Fast DMT	CP/IB	CP/IP
Polyol*	A	B	C	D	E	F
Gel time (sec)	45	43	34	38	43	45
Molded Density (kg/m3)	35	36	37	36	33.5	34.5
CS@10% (kPa)	145	150	170	150	140	145
k factor @ 24℃ (mW/mK)	19	21.2	20.2	21.1	21.5	21.5
Post Expansion ( %)	2	2.2	2.5	0.8	1.8	1.6

   * Isocyanate is the same (PAPI 27 of The Dow Chemical Company)

II.  HFC systems

Same as hydrocarbon systems, we developed and evaluated the following five systems in our laboratories;

-   HCFC-141b system (reference)

-   Conventional HFC-245fa system

-   Low k-factor HFC-245fa system

-   Conventional HFC-134a system

-   Low k-factor HFC-134a system

The foam performances are shown in Table 3.  From Table 3, the following results were obtained:

5) Compared to HCFC-141b system, conventional HFC-245fa system gave a 5.8% worse foam k-factor.  But an 11.4% foam density reduction and a 75% (2% vs. 0.5%) improvement of post expansion could be observed.

6) Low k-factor HFC-245fa system gave a 5% improved k-factor than conventional HFC-245fa system.  And the k-factor (19.1 mW/mK) is very closed to the k-factor of HCFC-141b system (19.0 mW/mK)

7) Conventional HFC-134a system gave a 15.3% worse k-factor than HCFC-141b system.  

8) Low k-factor system gave a 11.6% worse k-factor than HCFC-141b system.  And the improvement compared to conventional HFC-134a system was 3.2%.

Table 3. Foam performances of HFC systems

	HCFC-141b	HFC-245fa	HFC-245fa	HFC-134a	HFC-134a
Polyol*	A	G	H	I	J
	Conv.	Conv.	Low K	Conv.	Low K
Gel time (sec)	45	33	33	40	32
Molded Density kg/m3	35	31	33.5	33.5	34
CS@10%  kPa	145	125	155	130	140
k factor @ 24oC (mW/m·K)	19	20.1	19.1	21.9	21.2
Post Expansion, %	2	0.5	1.7	0.7	1.2

   * Isocyanate is the same (PAPI 27 of The Dow Chemical Company)

III.  Simulations of CO2 emission saving

1) Assumptions

Needless to say, the results obtained in section I and II only represent possible ranges of performance improvements.  The figures should vary by formulations and foaming conditions.  But to simplify the calculation, we decided to use these figures for simulation of CO2 saving.

In refrigerator industry, it is known that the energy consumption of a refrigerator can be improved about a half level of foam k-factor improvement.  For instance, if foam k-factor is improved by 10%, we can expect about a 5% improvement in energy consumption of the refrigerator.  Of course this ratio should vary by the design of refrigerator and performance of the compressor.  But we decided to use this ratio for simulation.  Other assumptions for the calculation are:

-       Average size and energy consumption of conventional cyclopentane blown foam refrigerators produced in China is 200L and 350 kWh/year respectively.

-       CO2 emission per kWh is 0.65 kg-CO2/kWh in China.

-       Annual production of refrigerators in China is 15 million units.

-       Average lifetime of a refrigerator is 10 years.

-       No change in energy consumption by gas diffusion etc. throughout the lifetime (10 years).

The simulations in the next section were calculated based on the assumptions above.  

2) CO2 emission

Possible CO2 saving by applying low k-factor system for each blowing agent system is shown in Table 4 in comparison with the conventional cyclopentane system. The accumulated number means possible CO2 saving when all the refrigerators newly produced in China are converted to the system.  From Table 4, it is obvious that accumulated CO2 saving is not negligible level even in China only.  And further technology development during the 10 years period should accelerate the reduction of CO2 emission further more.

Table 4. Possible CO2 emission saving in China by low k-factor system

	Con. CP system	Low K CP system	Conv. HFC-245fa system	Low K HFC-245fa system
Foam k-factor (mW/m·K)	21.2	20.2	20.1	19.1
k-factor reduction (%)	Standard	4.7	5.2	10.0
Energy saving as a refrigerator (%)	Standard	2.4	2.6	5.0
Energy saving as a refrigerator (kWh/year)	Standard	8.4	9.1	17.5
CO2 saving as a refrigerator (kg-CO2/year)	Standard	5.5	5.92	11.4
CO2 saving by new refrigerators (MT-CO2/year)	Standard	81,900	88,800	171,000
Accumulated (2003-2013) CO2 saving in China (MT)	Standard	4,504,500	4,884,000	9,405,000

3) Cyclopentane vs. HFC-245fa

There must be a question about choice of blowing agent for environment especially in terms of global warming issue.  In Table 4, even conventional HFC-245fa system can save higher amount of CO2 to low k-factor cyclopentane system.  And in case of low k-factor HFC-245fa system, it can save double amount of these systems.  On the other hand, HFC-245fa has much higher GWP compared to cyclopentane as shown in Table 1.  And the impact of each blowing agent to global warming was converted as CO2 amount for a standard 200L refrigerator (Table 5).  In Table 5, the impact is calculated as CO2 amount if the blowing agent in the foam for the refrigerator is completely released to the air.   

Now we can evaluate cyclopentane and HFC-245fa in terms of global warming issue by comparing each low k-factor system.  In 10 years lifetime:

-     HFC-245fa system gave -- (11.4 – 5.5) kg ´ 10 years = 59 kg of CO2 saving to cyclopentane system through less energy consumption

-     HFC-245fa has penalty of--205.7 kg–2.76 kg = 202.9 kg of CO2 if all the blowing agent is released to the air

According to this simulation, cyclopentane looks more environmentally friendly blowing agent than HFC-245fa.  But the situation should be different if the blowing agent in the foam is properly recovered or decomposed.

Table 5.  Impact of blowing agents as CO2 amount

System	Molded density (kg/m3)	Foam weight for 200L refrigerator (kg/unit)	Blowing agent contained (kg)	M.W. of blowing agent	Moles of blowing agent	GWP	Impact as CO2 moles	As CO2 (kg)
Conv. cyclopentane system	36	7	0.35	70	5.0	11	55.0	2.42
Low k-factor cyclopentane system	37	7.2	0.40	70	5.7	11	62.7	2.76
Conv. HFC-245fa system	31	6	0.57	134	4.3	820	3526	155.1
Low k-factor HFC-245fa system	33.5	6.5	0.77	134	5.7	820	4674	205.7

4) Raw Material conservation by foam density reduction

Natural resource conservation is another factor when we consider sustainable growth of appliance industry.  Raw materials for polyurethane foams including polyols, isocyanates, amine catalyst, silicone surfactants can be saved by developing low foam density systems.  As mentioned before, if we replace the current conventional cyclopentane system to the cyclopentane/isobutane system, about a 7% weight reduction is possible.  Thus as China total, 7350MT (7 kg x 15 MM units x 0.07) of PU raw materials can be saved annually.  But considering reverse effects on foam k-factor and capital investment to handle isobutane, the benefit looks marginal.

9)  Resource conservation by productivity improvement

Polyurethane technologies can contribute to resource conservation through productivity improvement.  The improvement of foam post expansion level from 2% to 0.8% normally gave demold time improvement by 20-40%.  This can save not only energy but also manpower and capital investments.  Overall, it can give a certain degree of contribution to environment through natural resource conservation.  However it is difficult to estimate the impact since the degree really depends on the design of plant and the way of manufacturing.

CONCLUSION

By applying advanced raw materials and formulation technologies, very low k-factor foams could be developed for each blowing agent in economical manner.  The foams obtained showed excellent foam k-factors and good processability.   These foams will make refrigerators more environmental friendly not only in terms of the blowing agents but also CO2 emission reduction through better energy efficiency.   As another options, cycle time reduction (fast demold) systems and low foam density systems were also developed and evaluated.  These gave us improved energy consumption in refrigerator manufacturing, and less usage of raw materials (natural resources).

The possible CO2 saving was simulated by using several data available in the industry.  Fast demold systems and low-density foam systems also could contribute to global environment through energy and raw material conservation.  Polyurethane technologies can contribute to sustainable growth of appliance industry especially in China by introducing best options and new solutions to customers.  

ACKNOWLEDGEMENT

The authors of this paper would like to thank the Dow PU R&D personnel in Freeport, Meyrin and Pacific area for their kind advice and information sharing.

REFERENCE

1. Chang, V, Jiao J, Ye R, “Rigid Appliance Foams – Current and Future Technologies in Asia Pacific”, U-Tech Asia 2002.

  

BIOGRAPHIES Jeffrey Jiao Jian-Qing

Jeffrey Jiao received a B.Sc. degree in polymer material from Shanghai Jiaotong University in 1991.  After several years’ polyurethane foaming experience in a refrigerator company, He joined Dow Chemical China in 1997 and is currently the application development specialist responsible for polyurethane technical service and system development for appliance market.

Ricky Ye Li

Ricky Ye received a B.Sc. degree in polymer material from Jiangsu College of Chemical Engineering and Technology in 1988. The same year he joined Suzhou XiangxueHai Refrigerator Company as a Polyurethane Engineer. In 1995 he transferred to Suzhou SAMSUNG Electronics Company as a supervisor in charge of chemical materials and process. He joined Dow in 1997 as a technical service and development engineer. Currently he is a technical service specialist responsible for appliance application.

Fujio Nakamura

Fujio Nakamura received his M.Sc. degree in Organic Chemistry from Keio University.  He joined Dow Chemical Japan Limited in 1984 in Polyurethanes R&D group.  He has worked in many fields of Polyurethane applications for last 19 years.  He is currently Rigid/CASE technology leader for the Pacific area.