Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
2001-12-19
2004-10-12
Teskin, Fred (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C526S227000, C526S228000, C526S232300, C526S347000, C526S348200, C526S348300, C526S348500, C568S559000, C502S160000, C525S387000, C525S938000, C252S182180, C252S182230, C422S001000
Reexamination Certificate
active
06803436
ABSTRACT:
The invention relates to containers containing specific organic peroxide formulations that can be handled, produced, and shipped in a safe manner and where the organic peroxide formulations contained therein can be used in polymerisation processes where the resulting polymer has a reduced level of undesired residues of low-molecular weight and/or inert phlegmatising agents.
Organic peroxides have long been known. Due to the safety hazards associated with most of them, they are often diluted with one or more specific solvents, also known as phlegmatisers. Classical phlegmatising agents are hydrocarbons and esters, such as phthalates.
U.S. Pat. No. 4,131,728 discloses a polymerisation process employing shock-sensitive peroxides in improved phlegmatisers. The improved phlegmatisers are specific monomers that do not homopolymerise. Exemplified suitable phlegmatising monomers are maleic and citraconic anhydride and esters thereof, fumarates and fumaronitriles, cinnamates and cinnamonitriles, and stilbene.
U.S. Pat. No. 4,029,875 discloses an ethylene polymerisation process employing a mixture of organic peroxides and cyclic olefins, styrene, or styrene homologues bearing alkyl substituents on the benzene nucleus to reduce the consumption of initiator in the process and to improve the optical and mechanical properties of the polyethylene produced.
Yu. A. Alexandrov et al. disclose in
Journal of Organometallic Chemistry,
157 (1978), 267-274, that silicon subgroup organoelement peroxides (peroxides where one Si, Ge or Sn atom is attached to the peroxygen function) in model studies showed specific decomposition behaviour and that the ratio of proton abstraction and addition to double bonds varies depending on the olefin that is used as the solvent. The present invention does not relate to silicon subgroup organoelement peroxides.
In WO 96/03397, disclosing particular safe cyclic ketone formulations, a variety of potential phlegmatisers is mentioned. However, ketone peroxides, including cyclic ketone peroxides, are not the subject of the present invention. It is noted that Akzo Nobel markets formulations of tert butyl peroxymaleate in dibutylmaleate solvent for specific use in unsaturated polyester resin curing processes with specific curing profiles.
Although many phlegmatisers are known and although reactive compounds have been combined with certain organic peroxides before, there is a need in the industry for packaged peroxide formulations that can be produced, handled, and shipped in a safe manner and where the peroxide formulations, when used in polymerisation reactions, do not lead to the presence of undesired phlegmatising agent in the resin that is produced. The most pressing need is for the supply of peroxides for use in the styrenics and high-pressure ethylene (co)polymerisation industry, where the phlegmatising agent as such should not end up in the final resin. However, such improved formulations which would reduce the amount of low-molecular weight (<1,000 Dalton) products, especially solvents, in the final product could be beneficial also in the process of making acrylic resins, to modify polymers, e.g. polypropylene, and to cure or cross-link polymers, such as polyethylene and unsaturated polyester resins.
In the styrenics industry it is preferred, especially when expandable polystyrene is produced using a suspension polymerisation process, that the phlegmatiser is apolar in nature to prevent the final resin from becoming more hydrophilic, which interferes with the foaming process. Due to the nature of the polymerisation process, relatively small quantities of concentrated, preferably technically pure, peroxide formulations are used. Traditionally, containers shipped for use in this industry are less than 500 liters, preferably less than 250 liters, more preferably less than 30 liters in size. For economic reasons and to reduce the amount of packaging material, the container will preferably contain more than 1 liter, more preferably more than 2 liters, most preferably more than 10 liters of the (phlegmatised) peroxide, such as the Nourytainers® ex Akzo Nobel. There is a need for a “drop in” replacement for the existing products, so that polymerisation recipes need not be changed, which leads to an improved product (containing less low-molecular weight compounds). However, there is also a need for more dilute peroxide formulations, which, for example, could be dosed automatically and/or stored safely in large-size (200 liters, preferably 500 liters or more) storage tanks.
In the high-pressure ethylene (co)polymerisation process, typically very dilute peroxide formulations, often containing just 10-40% w/w of peroxide and 60-90% w/w of phlegmatiser, are supplied. Particularly in these processes it is highly desirable that most if not all of the phlegmatiser be consumed or reacted, so that the resulting polymer contains an acceptably low amount of phlegmatiser. It is noted that because quite dilute peroxide formulations are to be supplied, it is preferred that the safety characteristics of the formulations are such that the container in which the peroxide formulations are shipped is at least 200 liters, preferably at least 1,000 liters, most preferably more than 10,000 liters in size.
Furthermore, there is a prejudice against shipping and storing large containers which contain peroxides in combination with reactive compounds for fear of increasing the hazards associated with the handling of said organic peroxides. More particularly, containers containing a peroxide will show a run-away thermal decomposition, also known as a thermal explosion, whenever the heat developing in the container due to decomposition of the peroxide is higher than the heat transmitted to the surroundings. The larger a (practical) container, the lower the surface to volume ratio will be. Therefore, shipment in larger containers is more hazardous. The presence of reactive compounds in peroxide formulations has always been expected to result in a less safe product, because the heat of reaction will contribute to the heat being generated, while the heat transfer to the surroundings is not increased. Hence, the shipment of peroxides dissolved in reactive compounds has never been commercialised, except for some peroxydicarbonates which have been shipped in monomers with allylic unsaturated groups which do not readily polymerise and must be shipped at very low and impractical temperature of −20° C., or in monomers that do not homopolymerise at all (meaning that no more than 1% of the monomer is converted in a test where a 1:1 weight ratio mixture of monomer and peroxide is kept at 40° C. for a period of 100 hours).
Surprisingly, we have found that containers with a size of more than 1 liter and containing organic peroxides and reactive diluents can nevertheless be shipped in a safe fashion at temperatures above −20° C., preferably above −10° C., more preferably above 0° C. The use of the reactive diluent gives the benefit of reduced unbound phlegmatiser in the polymer (so that the polymer contains less volatile product). Particularly in a high-pressure ethylene (co)polymerisation process, the phlegmatiser is consumed without the properties of the polymer being changed and without the polymerisation process being adversely affected. The reduced unbound phlegmatiser levels improve the organoleptic properties of the resulting (co)polymer and may even obviate a vacuum treatment of the molten polymer to reduce volatile material.
Accordingly, we claim a method to safely transport specific peroxide formulations comprising reactive phlegmatisers, containers comprising such specific peroxide formulations that are safely transportable, some preferred peroxide formulations that can be transported/shipped in such a fashion, and the use of the preferred peroxide formulations in polymerisation processes, particularly the (co)polymerisation process of ethylene at high pressure to make so-called (modified) low density polyethylene (LDPE) and the suspension polymerisation process to make expandable p
Fischer Bart
Roes Johannes Isodorus
Waanders Petrus Paulus
Akzo Nobel N.V.
Fennelly Richard P.
Teskin Fred
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