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化学品失控反应危害与防范-失控分解-有机过氧化物

organic peroxide crosslinking serves a variety of industries, including automotive, wire & cable, and oil & gas.

Selecting the proper organic peroxide is a critical parameter to consider for polymerization. The "initiator package" affects directly the polymer properties and also the productivity (% conversion, cost per unit of monomer converted).

有机过氧化物交联性能用于多个行业,包括汽车,电线电缆、石油天然气等。

如何选用适当的有机过氧化物是考虑聚合的关键参数。“引发剂包”直接影响聚合物性能以及生产率(转化%率,单体转化的单位成本)。


There are two main processes by which LDPE/EVA is produced via free radical initiation:

  • The tubular process
  • The autoclave process

Polymerization is propagating macroradicals building polymer chains to generate short or long branched structure.  Short segments affect mechanical performance of the finished polymer while longer branched chains affect the rheological behavior.  The reaction takes place at temperatures between 100 to 300°C and at high pressure (1200-3000 bars). At these pressures ethylene liquefies and acts as a solvent under supercritical conditions.

Molecular weight and density is regulated by controlling the temperature and pressure, and by the addition of a chain transfer agent (e.g. propane).

合成低密度聚乙烯LDPE/EVA有两种通过自由基引发的主要工艺。
聚合反应是传播构建聚合物链的大自由基以产生短或长支化结构。短链段影响成品聚合物的机械性能,而较长的支链影响流变行为。
反应在100-300℃的温度和高压(1200-3000巴)下进行。在这些压力下,乙烯液化并在超临界条件下作为溶剂。

通过控制温度和压力,以及通过加入链转移剂(例如丙烷)来调节分子量和密度。

 

Polypropylene Viscosity Modification

Isotactic polypropylene is a semi-crystalline polymer.  Free radicals generated using organic peroxides degrade the polypropylene backbone via beta-scission. This chemical process is used to adjust the melt flow, grade, and to narrow molecular weight distribution.  This operation is commonly called "vis breaking" or "PP controlled rheology."

The organic peroxide can be dry-blended with PP in the hopper of an extruder or injected in the extruder throughout several zones as:

  • a liquid (pure or diluted in a solvent)
  • a solid (peroxide + PP carrier)
全同立构聚丙烯PP是半结晶聚合物。使用有机过氧化物产生的自由基通过β-断裂降解聚丙烯主链。该化学过程用于调节熔体流,等级和收窄分子量分布。 这种操作通常称为“vis断裂”或“PP受控流变”。

有机过氧化物可以在挤出机的料斗中与PP干混,或者在挤出机中在几个区域注入:

以液态 (纯的或经溶剂稀释)

以固态形式 (过氧化物+PP载体)

 

Grafting嫁接

Peroxide is also useful for grafting maleic anhydride onto PP.  These grafted polymers are useful for:

  • Tie layers
  • Glass and filler
  • Printability and paintability
  • Increased compatibility with other homopolymers

过氧化物也可用于将马来酸酐嫁接到PP上。这些嫁接聚合物可用于:

粘接聚合物层

玻化填充

印刷性和涂布性

增强与其它均聚物的相容性

O
rganic peroxides is well adapted to suspension process for polymerizations of vinyl chloride.  The reaction is generally performed between 40 and 80°C over 3 to 10 hours. The molecular weight and density of the polymer can be regulated by temperature in the reactor. Temperature is constant during polymerization for a given grade, for example, K-67 is typically manufactured at 57°C. Suspension polymerization represents 80% worldwide production.

有机过氧化物被广泛应用于悬浮法聚合氯乙烯。反应通常在40~80℃下进行3~10小时。 聚合物的分子量和密度可以通过反应器中的温度来调节。在给定等级的聚合期间温度是恒定的,例如,K-67通常在57℃下制造。悬浮聚合法占全球生产量的80%。

 

Organic peroxide initiators for acrylics include a variety of solutions for solvent-borne, water-borne, liquid or solid resin synthesis.

In many acrylic applications like coatings and solid surface, color can be of critical importance. Organic peroxides have been shown to provide equal or enhanced reaction rates while avoiding the yellowing that is commonly observed when azo-initiators are used. In applications where azonitrile use leads to VOC generation, substitution with organic peroxides has been shown to produce lower VOC emissions.

Coatings, mirror housings, seals, and hoses, are just a small number of the automotive components that are made possible through the use of organic peroxides.

用于丙烯酸类的有机过氧化物引发剂包括用于溶剂型,水性,液体或固体树脂合成物的一系列溶液。

在丙烯酸许多应用中,比如涂料和固体表面,颜色常常至关重要。有机过氧化物已表明能提供相等或增强的反应速率,同时避免当使用偶氮引发剂时通常观察到的黄化。 在使用偶氮腈导致VOC产生的应用中,用有机过氧化物的替代已证明可产生较低的VOC排放。

车体涂层,反光镜外壳,密封件和软管就是通过使用有机过氧化物而得以制造的汽车部件中略举几例。


Organic Peroxides are the products of choice for many automotive coatings applications. In addition to providing increased reaction rates (faster processing) and lower process costs, the t-amyl products also provide improved coating appearance and durability.

Ketone Peroxides are a standard in the production of fiber-reinforced-plastics (FRP's) and composites for automotive applications. These products increase cure rate, decrease cure time and temperature, and contribute to higher strength in the final products.

有机过氧化物是许多汽车涂料应用的当然之选。除了能增加反应速率(加快工序)、降低工艺成本外,叔戊基化合物还能改善涂层外观和耐久性。

酮过氧化物是生产纤维增强塑料(FRP)和汽车应用复合材料的标配。这些产品提高固化速率,减少固化时间和温度,并有助于最终产品达到更高强度。



An organic peroxide is any organic chemical that contains an oxygen-oxygen (-O-O-) bond (peroxy functional group). A very large number of compounds fit this definition and therefore organic peroxides may have a wide range of properties.

有机过氧化物是含有氧 - 氧(-O-O-)键(过氧官能团)的各类有机化学品。数量庞大的化合物符合该定义,因此有机过氧化物可具有范围宽广的各种特性。


The peroxy functional group is thermally sensitive, containing a pseudo-stable energetic bond. For the organic peroxide to be useful as a free radical source this bond must be broken.  When properly used, these free radicals can initiate polymerization or other desired chemical reactions. This decomposition leads to heat and by-products.

过氧官能团具有热敏性,含伪稳态的能量键。有机过氧化物要成为自由基源,该键必须断裂。 使用得当,这些自由基可以引发聚合或其它所需的化学反应。而自由基的分解会产生热和副产物。


Each organic peroxide has a different rate of decomposition. Some organic peroxides must be stored and shipped under refrigerated conditions to preserve their usefulness and quality and for safety reasons. Other organic peroxides can be stored and shipped safely at or above ambient temperature. Determining the safe handling, storage and shipping temperatures is a significant part of the testing that must be done before an organic peroxide formulation is allowed to be transported or offered for sale.

每种有机过氧化物具有不同的分解速率。 一些有机过氧化物必须在冷藏条件下储存和运输,以保持其效用和质量,并还出于安全考虑。其他有机过氧化物可以在环境温度或高于环境温度下安全储存和运输。确定有机过氧化物制剂的安全处置,储存和运输温度是允许其运输或提供销售之前必须进行的测试的重要部分。


TYPES OF ORGANIC PEROXIDES

The simplified formula for an organic peroxide is R1OOR2 where R1 is an organic group and R2 is the same or different organic group or hydrogen. In the case of difunctional peroxides (two peroxide bonds in the structure) the structure is simplified as shown for peroxyketals or dialkyl peroxides in the table below.  In that case there may be three organic groups in the structure.

有机过氧化物的种类
有机过氧化物的简化式为
R1OOR2,其中R1是有机基团,R2是相同或不同的有机基团或氢。 对双官能过氧化物(结构中的两个过氧化物键),其结构可以简化作如下表中的过氧缩酮或二烷基过氧化物所示。在这种情况下,结构中可以有三个有机基团。

                            R1OOR2        R1 = organic group      R2 = (same or different) group 


Common types of commercially available organic peroxides and their typical ranges of 10 hour half-life temperatures are shown in the following table. Here the types are grouped by structural definition. Note that within each type, the exact structure of the various organic groups (R1, R2, or R3) determines the thermal stability of any particular member. For some types, such as peroxydicarbonates, the nature of the organic groups has little effect on the thermal stability. For other types, like peroxyesters, the organic groups can have a dramatic effect on thermal stability. In the case of peroxyesters you will see a wide range of 10 Hour Half-life temperatures as a result. In some of the types, one or more of the organic groups must be tertiary-alkyl groups in order for the peroxides to be good free radical initiators.

常见类型的市售有机过氧化物如下所列。这里的类型按结构定义分组。要注意在每种类型中,各种有机基团(R1R2R3)的确切结构决定了任何特定类中物质的热稳定性。对于一些类型,例如过氧化二碳酸酯,有机基团的性质对热稳定性几乎没有影响。而对于其它类型,如过氧酯,有机基团可对热稳定性具有显着的影响。 对于过氧酯,可看到范围很宽的10小时半衰期温度。在一些类型中,一个或多个有机基团必须是叔烷基,以使过氧化物成为良好的自由基引发剂。

 

dialkyl peroxides                二烷基过氧化物

hydroperoxides                  氢过氧化物

diacyl peroxides                 二酰基过氧化物   

peroxydicarbonates           过氧化二碳酸酯

peroxyesters                      过氧化酯

ketone peroxides               过氧化酮

peroxyketals                      过氧化缩酮

alkylperoxy carbonates      烷基过氧化碳酸酯

 

For the organic peroxide to be useful, the peroxy bond must be broken, usually by heating, to produce free radicals which can initiate polymerization or another desired end result. This decomposition also produces heat and by-products.

有机过氧化物要起作用,必须通常通过加热破坏其过氧键,以产生可引发聚合或其它期望的最终结果的自由基。这种分解也产生热和副产物。


Each peroxy group is considered to contain one active oxygen atom. The concept of active oxygen content is useful for comparing the relative concentration of peroxy groups in formulations, which is related to the energy content. In general, energy content increases with active oxygen content and thus, the higher the molecular weight of the organic groups, the lower the energy content and, usually, the lower the hazard.

每个过氧基团可看作含有一个活性氧原子。活性氧含量的概念可用于比较制剂中过氧基团的相对浓度,其与所含能量相关。通常,能量含量随活性氧含量增加,因此,有机基团的分子量越高,能量含量越低,危害通常也越低。


The term ACTIVE OXYGEN is used to specify the amount of peroxide present in any organic peroxide formulation. One of the oxygen atoms in each peroxide group is considered “active”.

Organic peroxides are often sold as formulations which include one or more phlegmatizing agents. That is, for safety sake or performance benefits the properties of an organic peroxide formulation are commonly modified by the use of additives to phlegmatize (desensitize), stabilize, or otherwise enhance the organic peroxide for commercial use. Commercial formulations occasionally consist of mixtures of organic peroxides which may or may not be phlegmatized.

“活性氧”一词用于定义在任何有机过氧化物制剂中存在的过氧化物数量。每个过氧化物基团中氧原子之一即被视为“活性的”。

有机过氧化物通常以含有一种或多种减敏剂的制剂配方出售。亦即,为安全或性能上的益处,有机过氧化物配制剂的性能常经改性,通过使用添加剂来钝化(脱敏),稳定或以其它方式加以增强,以用于商业用途。商业制剂偶尔由经过或未经减敏的有机过氧化物的混合物组成。


Technical

Organic peroxides can be used alone or combined with coagents.  Crosslinking is the process of chemically joining two polymer chains. For synthetic and natural rubber crosslinking, Arkema peroxides provide rubber and elastomers with outstanding mechanical, thermal, and chemical resistance performance.  A crosslink is a carbon-to-carbon bond between adjacent polymer chains.  

Organic peroxides decompose when exposed to heat, and produce free radicals.

These radicals abstract hydrogen atoms from the polymer backbones. This is possible both in unsaturated and saturated polymers. Two macro radicals can then recombine to create a direct C-C bond between adjacent polymer chains.

有机过氧化物可单独使用或与助剂组合使用。交联是化学上两个聚合物链结合的过程。对于合成和天然橡胶交联,过氧化物提供具有突出机械,耐热和耐化学性能的橡胶和弹性体。交联是相邻聚合物链之间碳 - 碳结合。

有机过氧化物当暴露于热时分解,并产生自由基。

这些基团从聚合物主链中提取氢原子。这在不饱和和饱和聚合物中都会发生。然后两个大基团可以重组从而在相邻的聚合物链之间产生直接的C-C键。


THERMAL DECOMPOSITION

Unlike most other chemicals, the purpose of a peroxide is to decompose. In doing so it generates useful radicals that can initiate polymerization to make polymers, modify polymers by grafting or visbreaking, or crosslink polymers to create a thermoset. When used for these purposes, the peroxide is highly diluted, so the heat generated by the exothermic decomposition is safely absorbed by the surrounding medium (e.g. polymer compound or emulsion). But when a peroxide is in a more pure form, the heat evolved by its decomposition may not dissipate as quickly as it is generated which can result in increasing temperature which further intensifies the rate of exothermic decomposition. This can create a dangerous situation known as a self-accelerating decomposition.

与大多数其他化学品不同,过氧化物的目的是分解。此时,可产生有用的自由基,并可引发聚合以制得聚合物,通过嫁接或减粘裂化改性聚合物,或使聚合物交联以产生热固性。当用作这些用途时,过氧化物被高度稀释,因此由放热分解产生的热可安全地被周围介质(例如聚合物化合物或乳液)吸收。但是当过氧化物处于较纯的形态时,其分解释放的热量可能不会像产热速度同样快地耗散,这会导致温度升高,并进一步加剧放热分解的速率。因而可能产生被称为自加速分解的危险情况。


A self-accelerating decomposition occurs when the rate of peroxide decomposition is sufficient to generate heat at a faster rate than it can be dissipated to the environment. Temperature is the main factor in the rate of decomposition. The lowest temperature at which a packaged organic peroxide will undergo a self accelerating decomposition within a week is defined as the self-accelerating decomposition temperature (SADT).

过氧化物分解速率足以产生多于其耗散到环境中的热量时,就会发生自加速分解。温度是分解速率的主要因素。已封装的有机过氧化物在一周内能产生自加速分解的最低温度定义为自加速分解温度(SADT)。

 

HALF-LIFE OF ORGANIC PEROXIDES

The term half-life relates to the time for one half of the starting material to decompose at a given temperature. The half-life of an organic peroxide reveals its rate of decomposition at certain conditions and allows the behavior of various organic peroxides to be compared.

半衰期一词是指半数物料在给定温度下分解的时间。有机过氧化物的半衰期指征其在某种条件下的分解速率,从而可以比较各种有机过氧化物的特性。


CONTAMINATION and PROMOTED DECOMPOSITION

In addition to thermally induced decomposition organic peroxides can be induced to decompose by contaminants such as amines, metal ions (by themselves or as a result of contact with metal surfaces), strong acids and bases, and strong reducing and oxidizing agents. Susceptibility to decomposition due to contamination or contact varies greatly among different organic peroxide types and formulations. For example, organic peroxides that are particularly susceptible are hydroperoxides (those with the -O-O-H group). However methyl ethyl ketone peroxides (MEKP’s) are also typically more susceptible to decomposition initiated by contamination. Careful thought should be put into the selection of materials of construction for all storage and handling systems that may have organic peroxides introduced to them. Selection of gaskets and materials of all sealing elastomers should also be considered for compatibility with the organic peroxide and possible solvent that might be used to introduce it into any chemical process. Although it is recommended to avoid contact with most metals and metal salts, cobalt (Co), iron (Fe) and copper (Cu) can be particularly troublesome. It is therefore conservatively recommended that all equipment and transfer lines that routinely handle organic peroxides should be fabricated of 316 stainless steel.

除了热致分解外,有机过氧化物也可以被诸如胺,金属离子(因其自身或与金属表面接触的结果),强酸和碱以及强还原剂和氧化剂等污染物诱发而分解。不同有机过氧化物类型和制剂之间对污染或接触所致分解的敏感性变化很大。例如,氢过氧化物(具有-O-O-H基团的那些物料)就是特别易受影响的有机过氧化物。而甲基乙基酮过氧化物(MEKP)通常也更易于由污染引起的分解。选择可能引入有机过氧化物的存储和处理系统构件材料时应慎密考虑。所有垫圈和密封弹性体材料的选择也应考虑与有机过氧化物以及将其导入各种化学工艺的可能的溶剂之间的相容性。除一般建议避免与大多数金属和金属盐接触以外,钴(Co),铁(Fe)和铜(Cu)特别可能造成麻烦。因此,保守地建议所有常规处理有机过氧化物的设备和输液管线应由316不锈钢制造。


In some cases the use of this characteristic can be exploited through the intentional “contamination” of the organic peroxide to induce decomposition at a lower temperature than normal for a particular organic peroxide formulation. In these cases the contaminant is referred to as a “Promoter”. Promoters allow organic peroxides to be used at lower temperatures than when simple thermal decomposition is the basis for decomposition. In those processes low concentrations of peroxides are used. One must be careful in handling promoters around organic peroxide formulations that have not been diluted. Severe reactions may be caused by accidental contamination of the undiluted organic peroxide formulation with the promoter.

某些情况下,可以探索利用该特性,通过对有机过氧化物特意“搀杂”以低于特定有机过氧化物制剂的正常温度诱导其分解。在这些情况下,搀杂物被称为“促解剂”。促解剂使得有机过氧化物可以在低于单纯热分解作为分解基础的温度下使用。在那些方法中还可使用低浓度的过氧化物。在未稀释的有机过氧化物制剂周围处置促解剂必须小心。未经稀释的有机过氧化物制剂与促解剂之间意外沾污可能引发激烈反应。


OXIDIZING PEROPERTIES

While most organic peroxides exhibit weak oxidizing properties toward reducing agents, contrary to wide-spread belief, most organic peroxide formulations are fuels, not oxidizers. Only one type of organic peroxide, peroxy acids, shows strong oxidizing properties. The oxygen-oxygen bond only rarely decomposes to give free oxygen. It should be noted that organic peroxides and strong oxidizers are not compatible.

虽然大多数有机过氧化物对还原剂表现出弱氧化性,但与常规想法相反,大多数有机过氧化物配制剂是燃料,即还原剂,而不是氧化剂。只有一种类型的有机过氧化物,过氧酸,显示出强氧化性。氧-氧键很少分解而得到游离氧。所以必须注意,有机过氧化物和强氧化剂是不相容的。


Hazardous peroxide decomposition

The major causes of peroxide decomposition (sources of hazard) are Heat, Fire, Friction, Shock and Contamination. Examples of the common sources of these include:

Heat- Sunlight; loss of refrigeration; radiators; heating elements; hot reaction vessels; heating ducts.

Fire - Open flame; sparks.

Friction- Mixing; pumping; grinding; traffic over spillage (which can generate heat).

Shock- Dropping; impact during transportation (which can generate heat).

Contamination- Metal salts; amines; acids; bases; polymerization accelerator; transition metals; per sulfates.

过氧化物分解的主要原因(危险源)是热,火,摩擦,冲击和污染。这些常见源的示例包括:

- 阳光; 制冷失效; 散热器; 加热元件; 热反应容器; 加热管道。

- 明火; 火花。

摩擦 - 混合; 泵送; 研磨; 车辆驶过泄漏物(可产生热量)。

冲击 - 运输过程中的冲击(可产生热量)。

污染 - 金属盐; ; ; 碱基; 聚合加速剂; 过渡金属; 每种硫酸盐。

 

HAZARD OVERVIEW

The three primary types of hazards to be concerned with are flammability, heat sensitivity and contamination.

A.    Flammability

All organic peroxides will burn vigorously, and once ignited will be difficult to extinguish. The flammability of organic peroxides will also be affected by the decomposition products. When most peroxides begin to decompose they will generate vapors and heat. Such vapors may be flammable and could be the cause of an explosion.

 
B.    Heat Sensitivity

All organic peroxides are sensitive to heat. If a peroxide is heated above a certain temperature (depending on the specific heat sensitivity of the peroxide itself) the rate of decompostion will increase in an uncontrolled manner. This reaction can become violent, releasing large volumes of hot, flammable gasses.

The temperature at which this will occur depends on the volume of the peroxide, the container and the period of time the peroxide remains at that temperature. The self accelerating decomposition temperature (SADT) test provides a measure of this hazard.

In general, the best way to avoid decomposition due to heat is to scrupulously adhere to the recommended storage temperatures for each product. This is particularly true for peroxides requiring refrigerated storage.


C.
   
Contamination

Chemical contamination can accelerate decomposition of organic peroxides. Care should be taken to avoid all forms of contamination, particularly oxidizing and reducing agents and metal salts –especially strong mineral acids. These will initiate a rapid decomposition at normal ambient temperatures, while many heavy metals such as copper, iron, brass, etc. will have a similar effect over a longer period of time.

需关注的三种主要危害性包括易燃性,热敏性和污染。

A.易燃性

所有有机过氧化物都会剧烈燃烧,一旦点燃将难以熄灭。有机过氧化物的可燃性也将受到分解产物的影响。大多数过氧化物开始分解时,将产生蒸气和热。这种蒸气可能是易燃的,是引发爆炸的可能原因。

 

B.热敏性

所有有机过氧化物对热敏感。如果将过氧化物加热到高于某一温度(取决于过氧化物本身的特定热敏度),分解速率将以不受控制的方式增加。这种反应可能变得剧烈,释放大量灼热、可燃气体。

发生这种情况的温度取决于过氧化物的体积,容器和过氧化物处于该温度下的时长。自加速分解温度(SADT)试验可提供此类危害性的量度。

一般来说,避免热分解的最佳方法是严格遵守每个产品的推荐储存温度。对于需要冷藏储存的过氧化物尤其如此。

化学杂污会加速有机过氧化物分解。应注意避免所有形式的污染,特别是氧化剂、还原剂和金属盐 - 特别是强无机酸。 这些将在正常环境温度下引发快速分解,而许多重金属例如铜,铁,黄铜等将在较长时间段内产生类似的效果。

 

STORAGE

In general, one of the most important factors to observe when working with organic peroxides is the required storage temperature. Exposure to a temperature that can lead to an accelerated decomposition may result in the generation of flammable gasses and, in some cases, spontaneous ignition. Proper storage is critical to the safe handling of organic peroxides, particularly those requiring controlled temperature storage. Ventilation is important because air circulation around peroxides stored at low temperatures reduces the chance of localized hot spots that can cause decomposition.

Organic peroxide inventory should be rotated to avoid shelf life problems. Only minimal quantities of peroxide should be kept in the immediate processing area.  Freezer or refrigerated facilities should be provided for intermediate storage of controlled temperature products.

储存

通常,在使用有机过氧化物时遵守的最重要的因素之一是所需的储存温度。暴露于可导致加速分解的温度下可能导致产生易燃气体,并且在一些情况下可能产生自燃。储存合适对于安全处置有机过氧化物,特别是那些需要控制温度储存的过氧化物至关重要。通风很重要,因为在低温下储存的过氧化物周围的空气循环降低了可能引起分解的局部热点的机会。

有机过氧化物库存应轮转,以避免保质期问题。直接加工区域中应只保留最少量的过氧化物。 温度控制产品的中间储存应采用冷冻设备或冷藏设施。

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