Cleaning compositions for solid surfaces – auxiliary compositions – Cleaning compositions or processes of preparing – For cleaning a specific substrate or removing a specific...
Reexamination Certificate
2002-06-13
2003-09-09
Gupta, Yogendra N. (Department: 1751)
Cleaning compositions for solid surfaces, auxiliary compositions
Cleaning compositions or processes of preparing
For cleaning a specific substrate or removing a specific...
C510S208000, C510S395000, C510S445000, C510S478000, C510S488000, C510S499000, C510S500000, C264S039000
Reexamination Certificate
active
06617295
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a composition which can be utilized to induce foaming of a resin or polymeric material in polymer processing machinery. The composition of the present invention includes a blowing agent which decomposes and evolves gases thereby causing the polymeric material to foam. The compositions of the present invention allow for reductions in part weight, cycle times and injection pressure.
BACKGROUND OF THE INVENTION
Many thermoplastic polymeric materials or resins are processed in polymer processing equipment such as injection molding devices. The pressures at which the materials are molded are quite high and cause premature wear of the processing equipment. The premature wear can result in costly expenditures which can increase the cost of preparing molded articles.
Molded articles or substrates often shrink unevenly after being molded at the relatively high pressure and thus have imperfections. Often the molded articles with imperfections are unacceptable to the end user and must be scrapped. The compositions of the present invention can be utilized to minimize equipment wear and produce quality parts.
SUMMARY OF THE INVENTION
The present invention provides a composition for foaming resin or polymeric material upon the flow of a stream of the blend polymeric material and composition through polymer processing machinery. The foaming or expansion of the resin brought about by the composition of the invention enables the polymeric material to flow through the polymer processing machinery under pressures that are lower than the pressures that are otherwise needed in the absence of such foaming. The composition includes a mixture of additives separate from the polymeric material in a state pourable into the stream of polymeric material. The additives include a blowing agent effective to induce foaming of the stream of polymeric material, and at least one filler. The additives further include a surfactant effective to reduce surface tension of the blend and thus promote the flow of the stream of polymeric material along the inner surfaces of the polymer processing machinery. A binder binds the additives together in the mixture.
The present invention also provides a method for foaming resin as the resin passes through the processing machinery. The method includes blending a composition comprising a blowing agent, a filler, a surfactant, and a binder with a polymeric material or resin, to form a mixture, processing said mixture in a polymer processing apparatus, and forming a molded article from said mixture. A method for preparing the compositions of the present invention is also described.
This invention allows the processor to open processing windows regarding machine size, tool design, and resin choices. It will also provide weight reduction resulting in lower conversion costs. The invention also gives the processor the ability to reduce cycle times, improve the quality of finished product and reduce process times.
DETAILED DESCRIPTION OF THE INVENTION
A) Foaming Compositions
The compositions of the present invention are useful to improve the processability of polymeric material or resins and are capable of reducing part weight, peak injection pressure, shot size, and molding cycle time. Thus substantial cost savings are available to the processors of injection molded articles or substrates who utilize the compositions of the present invention in conjunction with polymeric materials.
Blowing or foaming agents are utilized in the composition of the present invention. Blowing agents can be endothermic, exothermic, or a combination thereof. The specific blowing agent utilized is selected to be active at or below the processing temperature or range of the polymeric material being processed. Typical blowing agents, when activated, evolve or produce a gas such as nitrogen or carbon dioxide. As the gas evolves, the volume of the composition and polymeric material mixture expands within the processing device. In order to prevent the blowing agent from prematurely activating or decomposing, the compositions are processed and preferably formed into particles below the activation temperature of the blowing agent. The particles are a dispersion or conglomerate of the components of the present invention in a solid, non-liquid particulate form such as but not limited to pellets, granules and flakes, with pellets being preferred.
During molding of a polymeric material and the composition of the present invention at elevated temperatures sufficient to degrade or activate the blowing agent, endothermic blowing agents will absorb heat as they degrade, which can reduce the cure time (mold closed) during a molding operation. The melt flow (polymer and composition) is placed under greater pressure by the blowing agent due to the evolution of gas. Accordingly, the injection pressures, as well as injection fill times can be reduced which results in both time and energy savings. The creation of a micro cellular structure within the melt will eliminate molding flaws such as sinks in the molded article. Cell structure is dictated by at least the volume of gas present in the melt flow (ml/gm) and the particle size of the nucleator. Eliminating or reducing the pack and hold portion of the injection cycle can also control over-packing. Also, a short shot of a reduced amount of polymeric material and composition can be utilized to fill the cavity to capacity due to the cell expansion of the blowing agent. The compositions of the present invention will allow one to fill tools or mold cavities, which are oversized, for barrel capacity by increasing the overall volume.
Suitable commercially available blowing agents available from Mats Corp. Ltd. of Markham, Ontario as MS01, Cenblo Mat 100 or 500 (a carboxylic acid and carbonate based product), Uniroyal Chemical Company, Inc. of Middlebury, Conn., as Expandex® 5PT (a 5-phenyl tetrazole based product), EPI Environmental Plastics Inc. of Conroe, Tex., as EPIcor, Uniroyal Chemical Company of Middlebury, Conn., as Expandex and Reedy International Corp. of Keyport, N.J. as Safoam.
Non-limiting examples of endothermic blowing agents are polycarbonic acids, coated sodium bicarbonate, coated citric acid, coated mono sodium citrate, and coated sodium citrate. Exothermic blowing agents include azodicarbonamides, modified azodicarbonamides, oxybis benezenesulfonyhydrazide (OBSH), toluenesulfonyhydrazides (TSH), 5-pheyltetrazole (5-PT), diisopropylhydrazodicarboxylate (DIHC), and dinitrosopentamethylenetetramine (DNPT).
A binder component is utilized in the flow improving foaming compositions of the present invention. The binder can beneficially unite the other components present and render them more dispersible in the polymeric material to be processed. The binder component includes waxes which can be natural or synthetic. The waxes are generally solid at room temperature and have a weight average molecular weight of less than about 10,000. The binder component is preferably present in the foaming compositions of the invention in amounts greater than about 10% by weight of the total composition, generally from about 10 to about 100 parts, desirably from about 20 to about 80 parts, and preferably from about 25 parts or about 30 parts to about 50 parts or about 60 parts by weight based on 100 parts by weight of the blowing agent.
Examples of waxes suitable for the binder component of the present invention include, but are not limited to, amide waxes such as ethylene bis-stearamide wax and hydroxystearamide wax, maleated ethylene waxes, maleated propylene waxes, microcrystalline waxes, oxidized waxes, paraffin waxes, petroleum waxes, polyethylene waxes, PTFE waxes, ethylene vinyl acetate waxes, wax esters, and polycaprolactone wax, or combinations thereof. The preferred binder component is a mixture of ethylene bis-stearamide wax and hydroxystearamide wax, at a ratio of about 60% to about 40%, respectively based on the total binder component. A further preferred binder component is a mixture of polycaprolactone wax and polyolef
Gupta Yogendra N.
Hornickel John H.
Hudak, Shunk & Farine Co. LPA
Mruk Brian P.
PolyOne Corporation
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