首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 62 毫秒
1.
镍系催化十二烯聚合   总被引:2,自引:0,他引:2  
我国镍系顺丁橡胶(BR)生产采用以加氢汽油为溶剂的Ni(naph)2-Al(i-Bu)3-BF3.OEt2(简称Ni-Al-B)催化体系。聚合活性与Al/B(摩尔比)密切相关,Al/B值又是调节BR分子量的关键参数。催化活性中心上镍的价态分别为Ni(0)和Ni(I),聚合反应的表观活化能为Ea[Ni(0)<Ea[Ni(I)]。AlR2F也是组成活性中心配合物的结构单元。催化活性表现有低温聚合依时性  相似文献   

2.
张玲  廖海燕 《弹性体》1997,7(3):7-13
研究了Ni(naph)2-Al(i-Bu)3-(BF3.OEt2+ROH0体系催化丁二烯聚合的特点,考查了ROH/B摩尔比,Al/Ni摩尔比,Ni/Bd摩尔比等反应条件对聚合活性及聚合产物分子量的影响。  相似文献   

3.
BR生产用镍催化体系的聚合活性和稳定性   总被引:1,自引:0,他引:1  
研究了生产顺丁橡胶(BR)用Ni(naph)_2-Al(i-Bu)_3-BF_3·OEt_2(Ni-Al-B)催化体系的聚合活性,考察了“Al-Ni陈化,稀B单加”催化体系的稳定性。结果表明,该催化体系的组分化、陈化方式对聚合活性有极大影响;“Al-Ni陈化,稀B单加”催化体系有较好的耐时性,形成的活性中心有较高的耐温性。  相似文献   

4.
以二乙胺为例研究了胺对Ni(naph)2-Al(-Bu)3-BF3·OEt2+n—C8H17OH(简称Ni-Al-B+ROH)和Ni(naph)2-Al(i-Bu)3-BF3·OEt2+CH3COOC4H9(简称Ni—Al—B+BA)两体系聚合活性和聚合物分子量的影响,并与Ni—Al—B体系进行了对比.考察了通常条件下肢的允许含量,讨论了有胺存在时Ni/Bd、Al/Ni、Al/B摩尔比的变化对聚合规律的影响。结果表明:胺的含量高于20ppm时将使聚合活性和分子量降低,提高催化剂用量可以抑制胺的不利影响。  相似文献   

5.
镍顺丁橡胶分子量控制   总被引:1,自引:1,他引:0  
张玲  仲崇祺 《弹性体》1999,9(3):1-5
本文分别就Ni(naph)2 —Al(i - Bu)3 —(BF3·OEt2 + ROR) 、Ni(naph)2 —Al(i- Bu)3 —(BF3·OEt2 + ROH) 体系中聚合条件对催化活性及聚合物分子量的影响关系进行了对比,同时还比较了加醚体系、加醇体系的聚合动力学参数。实验结果表明,同稀硼单加的传统体系相比较而言,醚体系具有稳定的分子量控制能力。醚在体系中起着稳定活性中心的作用。该体系适于质量稳定的中门尼顺丁胶的生产。辛醇体系能够很灵敏地从低到高调节聚合物的分子量。高分子量可控制在门尼粘度为85 ±5 之间,有利于高门尼充油顺丁胶的合成;低分子量最小可调至[η] = 0 .5dl/g 。这是稀硼单加体系、醚体系不及之处。由于辛醇的作用,通过Al/B 比的改变,顺丁胶特性粘数可在0 .5 ~5 .0dl/g 之间很宽范围内调变。醇或醚类的加入均对聚合物分子量分布、微观结构影响不大。  相似文献   

6.
张玲  张三强 《弹性体》1998,8(2):1-6
研究了Ni(naph)2-Al(i-Bu)3-BF3.OEt2-ROR’体系催化丁二烯聚合的特点,考察了Al/B摩尔比,Al/Ni摩尔比,Ni/Bd摩尔比,ROR’/B摩尔比等反应条件对聚合活性及聚合产物分子量的影响,还考察了该体系的凝胶含量,实验结果表明,该体系中醚的加入不仅保持体系较高的聚合活性,较好的地控制聚合物分子量,而且还能降低体系的凝胶含量,Al/B比的变化对聚合物活性及聚合物分子量的  相似文献   

7.
研究了Ni(naph)2—Al(i-Bu)3—BF3·OEt2—ROR′体系催化丁二烯聚合的特点,考察了Al/B摩尔比、Al/Ni摩尔比、Ni/Bd摩尔比、ROR′/B摩尔比等反应条件对聚合活性及聚合产物分子量的影响,还考察了该体系的凝胶含量。实验结果表明,该体系中醚的加入不仅保持体系较高的聚合活性,较好地控制聚合物分子量,而且还能降低体系的凝胶含量。Al/B比的变化对聚合活性及聚合物分子量的影响显著,Al/Ni比、Ni/Bd比、ROR′/B比对其影响不大。  相似文献   

8.
张玲  刘开坤 《弹性体》1999,9(2):15-18
研究了Ni(naph)2-Al(i-Bu)3-BF3·OEt2-C8H17OH体系合成低分子聚丁二烯,考察了Al/B摩尔比、Al/Ni摩尔比、Ni/Bd摩尔比、C8H17OH/B摩尔比等反应条件对聚合活性及聚合产物分子量的影响。实验结果表明,该体系在Al/B比于015~030之间时,随着Al/B比的降低,聚合活性下降,聚合物分子量也降低。由于辛醇的作用,聚丁二烯的特性粘数最低可降至05dL/g。Al/B比的变化对聚合活性及聚合物分子量的影响显著,Al/Bd比、Ni/Bd比、C8H17OH/B比对其影响不大  相似文献   

9.
黄健 《合成橡胶工业》1994,17(4):204-206
以Ni(naph)2-Al(i-Bu)3-BF3·OEt2(Ni-Al-B)为催化体系,抽余油为溶剂,制备了充油镍系顺丁橡胶,研究了不加第三组分提高基础胶门尼粘度的聚合规律,讨论了ML,胶含量和胶液粘度的关系,选择了充油镍系顺丁橡胶的制备条件,考察了充油胶的性能。结果表明,丁二烯溶液聚合体系水含量在一定范围时,提高Al/B值(摩尔比),可在镍系顺丁橡胶生产装置上生产出质量优良的充油镍系顺丁橡胶。  相似文献   

10.
研究了Nd(naph)3-Al(i-Bu)2H-Al(i-Bu)2Cl催化体系引发丁二烯聚合动力学,得到了聚合速度方程式-d[M]/dt=kpα[c]0[M]。发现聚合物的Mn在聚合过程中随着单体转化率的增加而下降。测得了该催化体系的活性中心浓度和有关动力学参数。  相似文献   

11.
12.
Vismiones and ferruginins, representatives of a new class of lypophilic anthranoids from the genusVismia were found to inhibit feeding in larvae of species ofSpodoptera, Heliothis, and inLocusta migratoria.  相似文献   

13.
14.
Despite its industrial importance, the subject of freeze-thaw (F/T) stability of latex coatings has not been studied extensively. There is also a lack of fundamental understanding about the process and the mechanisms through which a coating becomes destabilized. High pressure (2100 bar) freezing fixes the state of water-suspended particles of polymer binder and inorganic pigments without the growth of ice crystals during freezing that produce artifacts in direct imaging scanning electron microscopy (SEM) of fracture surfaces of frozen coatings. We show that by incorporating copolymerizable functional monomers, it is possible to achieve F/T stability in polymer latexes and in low-VOC paints, as judged by the microstructures revealed by the cryogenic SEM technique. Particle coalescence as well as pigment segregation in F/T unstable systems are visualized. In order to achieve F/T stability in paints, latex particles must not flocculate and should provide protection to inorganic pigment and extender particles. Because of the unique capabilities of the cryogenic SEM, we are able to separate the effects of freezing and thawing, and study the influence of the rate of freezing and thawing on F/T stability. Destabilization can be caused by either freezing or thawing. A slow freezing process is more detrimental to F/T stability than a fast freezing process; the latter actually preserves suspension stability during freezing. Presented at the 82nd Annual Meeting of the Federation of Societies for Coatings Technology, October 27–29, 2004 in Chicago, IL. Tied for first place in The John A. Gordon Best Paper Competition.  相似文献   

15.
16.
17.
In 2002–2004, we examined the flight responses of 49 species of native and exotic bark and ambrosia beetles (Coleoptera: Scolytidae and Platypodidae) to traps baited with ethanol and/or (−)-α-pinene in the southeastern US. Eight field trials were conducted in mature pine stands in Alabama, Florida, Georgia, North Carolina, and South Carolina. Funnel traps baited with ethanol lures (release rate, about 0.6 g/day at 25–28°C) were attractive to ten species of ambrosia beetles (Ambrosiodmus tachygraphus, Anisandrus sayi, Dryoxylon onoharaensum, Monarthrum mali, Xyleborinus saxesenii, Xyleborus affinis, Xyleborus ferrugineus, Xylosandrus compactus, Xylosandrus crassiusculus, and Xylosandrus germanus) and two species of bark beetles (Cryptocarenus heveae and Hypothenemus sp.). Traps baited with (−)-α-pinene lures (release rate, 2–6 g/day at 25–28°C) were attractive to five bark beetle species (Dendroctonus terebrans, Hylastes porculus, Hylastes salebrosus, Hylastes tenuis, and Ips grandicollis) and one platypodid ambrosia beetle species (Myoplatypus flavicornis). Ethanol enhanced responses of some species (Xyleborus pubescens, H. porculus, H. salebrosus, H. tenuis, and Pityophthorus cariniceps) to traps baited with (−)-α-pinene in some locations. (−)-α-Pinene interrupted the response of some ambrosia beetle species to traps baited with ethanol, but only the response of D. onoharaensum was interrupted consistently at most locations. Of 23 species of ambrosia beetles captured in our field trials, nine were exotic and accounted for 70–97% of total catches of ambrosia beetles. Our results provide support for the continued use of separate traps baited with ethanol alone and ethanol with (−)-α-pinene to detect and monitor common bark and ambrosia beetles from the southeastern region of the US.  相似文献   

18.
Halyomorpha halys (Stål) (Pentatomidae), called the brown marmorated stink bug (BMSB), is a newly invasive species in the eastern USA that is rapidly spreading from the original point of establishment in Allentown, PA. In its native range, the BMSB is reportedly attracted to methyl (E,E,Z)-2,4,6-decatrienoate, the male-produced pheromone of another pentatomid common in eastern Asia, Plautia stali Scott. In North America, Thyanta spp. are the only pentatomids known to produce methyl 2,4,6-decatrienoate [the (E,Z,Z)-isomer] as part of their pheromones. Methyl 2,4,6-decatrienoates were field-tested in Maryland to monitor the spread of the BMSB and to explore the possibility that Thyanta spp. are an alternate host for parasitic tachinid flies that use stink bug pheromones as host-finding kairomones. Here we report the first captures of adult and nymph BMSBs in traps baited with methyl (E,E,Z)-2,4,6-decatrienoate in central Maryland and present data verifying that the tachinid, Euclytia flava (Townsend), exploits methyl (E,Z,Z)-2,4,6-decatrienoate as a kairomone. We also report the unexpected finding that various isomers of methyl 2,4,6-decatrienoate attract Acrosternum hilare (Say), although this bug apparently does not produce methyl decatrienoates. Other stink bugs and tachinids native to North America were also attracted to methyl 2,4,6-decatrienoates. These data indicate there are Heteroptera in North America in addition to Thyanta spp. that probably use methyl 2,4,6-decatrienoates as pheromones. The evidence that some pentatomids exploit the pheromones of other true bugs as kairomones to find food or to congregate as a passive defense against tachinid parasitism is discussed.  相似文献   

19.
收集了2007年7月~2008年6月世界塑料工业的相关资料,介绍了2007~2008年国外塑料工业的发展情况,提供了世界塑料产量、消费量及全球各类树脂的需求量及产能情况.按通用热塑性树脂(聚乙烯、聚丙烯、聚苯乙烯、聚氯乙烯、ABS树脂)、工程塑料(尼龙、聚碳酸酯、聚甲醛、热塑性聚酯、聚苯醚)、特种工程塑料(聚苯·硫醚、液晶聚合物、聚醚醚酮)、通用热固性树脂(酚醛、聚氨酯、不饱和聚酯树脂、环氧树脂)不同品种的顺序,对树脂的产量、消费量、供需状况及合成工艺、产品应用开发、树脂品种的延伸及应用的进一步扩展等技术作了详细介绍.  相似文献   

20.
收集了2005年7月~2006年6月国外塑料工业的相关资料,介绍了2005—2006年国外塑料工业的发展情况。提供了世界塑料产量、消费量及全球各类树脂生产量以及各国塑料制品的进出口情况。作为对比,介绍了中国塑料的生产情况。按通用热塑性树脂(聚乙烯、聚丙烯、聚苯乙烯、聚氯乙烯、ABS树脂)、工程塑料(聚酰胺、聚碳酸酯、聚甲醛、热塑性聚酯、聚苯醚)、通用热固性树脂(酚醛、聚氨酯、不饱和树脂、环氧树脂)、特种工程塑料(聚苯硫醚、液晶聚合物、聚醚醚酮)的品种顺序,对树脂的产量、消费量、供需状况及合成工艺、产品开发、树脂品种的延伸及应用的扩展作了详细的介绍。  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号