Foam composition comprising oil, thermoplastic elastomer and...

Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...

Reexamination Certificate

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C521S098000, C521S139000, C521S140000

Reexamination Certificate

active

06451865

ABSTRACT:

The present invention relates to a foam composition, a pre-foam composition and process for the production of foams and pre-foam compositions.
Oil gel compositions are generally useful as filling compounds in wire and cable applications. Their properties include slump resistance at high service temperatures, strippability and good working viscosity. The oil gels need strippability so that installers and repair men can make electrical splices easily in the field. A good working viscosity is required so that the oil gel melt or solution can be easily pumped into the cable. Other characteristics of oil gels include compatibility with other components in the cable system and a lack of stiffness so that they do not add to the stiffness of the cable.
These oils gel compositions are also well suited for re-enterable sealing of electrical connections. Other end uses for these oil gel compositions include vibration damping, pressure relief, toys, cushioning, grips, therapeutic and orthopaedic devices.
Due to their extremely low melt (or solution) viscosity, oil gels lead to a diffusion of gas bubbles when the oil gel is mixed with a chemical blowing agent and heated above the blowing temperature. The diffusion of gas bubbles causes a failure to produce a foamed structure. Furthermore, oil gels are often used for their “self-healing” properties, ie when an oil gel is punctured or torn, the gel structure reforms after a short time leaving no visual traces. However, the “self-healing” properties of an oil gel would also lead to a destruction of any foamed structure once the foamed structure is put under any pressure. For this reason, oil gels have not been considered for foam applications.
However, in accordance with the invention, it has been discovered that the use of heat expandable hollow particles such as microspheres prevents collapse of the foam structure. Furthermore, it has surprisingly been found that the low melt or solution viscosity of the oil gel materials is advantageous in allowing blending of the oil gels with the heat expandable hollow particles and by blending a homogenous distribution of the particles can be attained. Furthermore, the low melt or solution viscosity of the oil gels allows the use of a low temperature blending process which maximises the utility of the hollow expandable particles which are prone to collapse above the expansion limit temperature.
W09712930 describes a manufacturing method for a padding element used as an interior component of a motor vehicle which comprises moulding the padding element from a mixture of microspheres and a plasticised thermoplastic material matrix. The microspheres are formed from plastic shells filled with gas or liquified gas. In addition EP0717091 describes a pressure sensitive adhesive foam which comprises a thermoplastic block co-polymer, tackifying resin, isocyanate terminate monomer, polymer, and expandable articulate materials. However, none of these documents addresses the problems associated with foaming oil based compositions of low melt or solution viscosity.
U.S. Pat. No. 5,626,657 defines a composite mixture which comprises spheres having a lubricant of viscoelastic fluid on the surface. The lubricant or viscoelastic fluid comprises a main lubricant and elastomeric polymer and is present in a quantity less than that which would cause dispersion of the spheres with significant separation from one another by the lubricant. Spheres flow in low friction sliding and rolling contact with each other in response to a deforming pressure, where the lubricant reduces the co-efficient of friction between the spheres. Again, the document does not address the problem of producing foam from an oil based composition.
EP-200822 describes a cushioning article which comprises a closed flexible envelope containing a quantity of discreet, relatively-moveable, gas-filled enclosures bounded by respective permanent flexible walls. A lubricant is provided to facilitate the relative movement of the gas-filled enclosures within the envelope. Articles of this type are said to follow body contours of a user, distribute pressure evenly and provide greater comfort, as well as reduce hardness. Again, this publication does not address the production of foams from oil based compositions of low viscosity.
According to one aspect of the present invention, there is provided a process for producing a foam comprising the steps of:
forming a pre-foam composition comprising oil(s), thermoplastic elastomer(s) and heat expandable thermoplastic particles encapsulating heat expandable gas or liquified gas;
heat treating the said composition to cause the said particles to expand and produce a Loam from the said composition.
Preferably, the thermoplastic elastomer(s) is/are present in an amount of 2-40% by weight of the pre-foam composition, more preferably, 8-25% by weight of the pre-foam composition.
Preferably, the said heat expandable thermoplastic particles are present in an amount of 0.5-6% by weight of the pre-foam composition, more preferably, 1-4%, most preferably, at least 2% by weight of the pre-foam composition.
Preferably, the oil(s) is/are in a range of 54-97% by weight of the pre-foam composition.
Typically, the thermoplastic elastomer(s) is/are present in an amount which gives a viscosity to the oil gel melt or solution which allows dispersion of the particles in the melt or solution but substantially prevents migration thereof towards the surface during cooling.
Preferably, the oil/thermoplastic elastomer melt or solution viscosity is in the range of typical oil gels, that is in the range from 50 to 100,000, preferably 200 to 30000 Pa.s at 120° C.
In the process of the invention, typically, the composition forms a melt during said heat treating step or prior to the said heat treating step in a melting step.
Alternatively, but less preferably, the pre-foam composition can be prepared from an oil solution using a solvent or blends of solvents that assist dissolution of the thermoplastic elastomer but will not dissolve the heat expandable particles. Examples of suitable solvents include toluene, xylene, cyclohexane, methylethyl ketone, or combinations thereof.
Preferably, the process includes a particle dispersion step, prior to the heat treating step. Preferably, mixing of the components of the composition is continued until homogenous dispersion of the particles is achieved. Preferably, the particles are added to oil(s) and thermoplastic elastomer(s) beyond the glass transition temperature of the latter, or in case the thermoplastic elastomer(s) has (have) two glass transition temperatures, beyond the highest glass transition temperature.
Preferably, tackifying resin, wax(es), filler(s), solvents, and/or end block resin can be added to the composition in accordance with the end use.
Preferably, the oil(s) and thermoplastic elastomer(s) are present in the relative ranges of oil gels.
The invention also extends to a process for producing the pre-foam composition for subsequent heating and foam formation.
Still further aspects of the invention include a pre-foam composition comprising oil(s), thermoplastic elastomer(s) and the said particles, additionally comprising fillers, end block resin and/or solvents. The invention also extends to a foam produced from the said pre-foam composition. The invention may also be utilised in the formulation of adhesives, coatings and sealants comprising the foam or pre-foam composition.
Preferably, in the process according to the present invention, the oil and thermoplastic elastomer are heated beyond the glass transition temperature, or the highest glass transition temperature, of the thermoplastic elastomer and the said expandable particles are added to the melt. Preferably, the said particles are mixed with the melt until substantially homogenous distribution is achieved.
Preferably, in foam preparation, the composition is heat treated by being heated to a suitable expansion temperature for the hollow particles.
Preferably, the expansion temperature is above the melting point of the oil/thermoplastic elas

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