Improved process for forming a thin microporous sheet material

Claim 2

The process of forming a microporous sheet as defined in claim 2 in which said layer of emulsion is held at elevated temperature after casting to complete the reaction between said reactive components.

Claim 3

The process of forming a microporous solidified body as defined in claim 1 in which said body is a thin, microporous layer and said process includes the steps of depositing said emulsion in a thin layer on a supporting surface, providing means to prevent loss of non-solvent liquid from said emulsion on the face of said layer opposite said supporting surface before substantial reaction of said components, thereafter reacting said components to bring the layer to a solid state with said means in place and without substantial expansion of said layer, removing said means from said face after solidification of said reaction mixture and thereafter removing said non-solvent liquid from said layer.

Claim 4

The process of forming a microporous solidified body as defined in claim 4 in which said means to prevent loss of non-solvent liquid is an impervious cover in contact with said face of said layer.

Claim 5

The process of forming a microporous solidified body as defined in claim 5 in which said impervious cover is a flexible sheet material.

Claim 6

The process of forming a microporous solidified body as defined in claim 4 in which said means to prevent loss of non-solvent liquid is a layer of an organic liquid having a boiling point of at least about 100* C. and being substantially non-solvent for and non-reactive with said reactive material and being immiscible in said continuous phase.

Claim 7

The process of forming a microporous solidified body as defined in claim 7 in which the liquid of said non-solvent liquid layer is the same as the liquid of said fine droplets.

Claim 8

The process of forming a microporous solidified body as defined in claim 4 in which said means to prevent loss of non-solvent liquid is a porous layer impregnated with an organic liquid having a boiling point of at least about 100* C., said liquid being substantially non-solvent for and non-reactive with said reactive material and being immiscible in said continuous phase.

Claim 9

The process of forming a microporous solidified body as definEd in claim 6 in which said polymeric reactive component is heated to a temperature of at least about 50* C. to bring it to a viscosity suitably low for emulsion formation and in which said liquid is an aliphatic hydrocarbon having a boiling point above the emulsifying and reaction temperature.

Claim 10

The process of forming a microporous solidified body as defined in claim 10 in which said layer of emulsion is held at elevated temperature after casting to complete the reaction between said reactive components.

Claim 11

In the process of forming a microporous solidified body comprising the steps of casting a water-free emulsion of fine droplets of a volatile organic liquid as the internal phase in a continuous phase comprising reactive material convertible through reaction to solidified, resilient, film-forming condition, said reactive material comprising a mixture of an organic compound providing at least two reactive -NCO groups per molecule and an organic compound having at least two active hydrogens per molecule for reaction with said -NCO groups, said organic liquid having a boiling point of at least about 100* C. and at least 90 percent boiling below 232* C., being substantially non-solvent for and non-reactive with said reactive material, being immiscible in said continuous phase and being present in amount from about 60 percent to about 300 percent by weight based on the weight of the reactive material, reacting said material at a temperature below the boiling point of said liquid so that the liquid never boils to cause the emulsion to gel and solidify with said droplets held in the solidified material and removing said liquid without expanding the solidified material leaving pores and discontinuities in the solidified material to constitute passageways for air and vapor, the improvement which comprises employing as said continuous phase a mixture of reactive components which is substantially free from solvents for said reactive components, said reaction mixture including as reactive components at least one -NCO terminated prepolymer from reaction of a polyisocyanate with a polymeric polyol from the group consisting of polyalkyleneether polyols, polyester polyols from reaction and condensation of polybasic acids and polyols and polyester polyols from caprolactones which are solid or pasty at room temperature and a chain extender having at least two active hydrogens per molecule for combination with the -NCO groups of said prepolymer to form a higher molecular weight, tough, strong film-forming material and said mixture has a consistency at room temperature which interferes with emulsifying said immiscible liquid, heating any reactive component which is solid or pasty at room temperature to bring it to freely fluid state and mixing said reactive components and dispersing said immiscible liquid to form an emulsion while said solid or pasty at room temperature component is in heated state, whereby the consistency of the emulsion after casting is improved due to the presence of said polymeric component to aid in retaining the dispersed droplets uniformly distributed through the layer.

Claim 12

The process of forming a microporous sheet as defined in claim 12 in which said chain extender is at least one member of the group consisting of p,p''-methylenedianiline, 4,4''-methylene -bis - (2,-chloroaniline), trimethylol propane, m-phenylenediamine, 1,4 butane diol and triethanolamine.

Claim 13

The process of forming a microporous sheet as defined in claim 13 in which said polymeric reactive component is heated to a temperature of at least about 50* C. to bring it to a viscosity suitably low for emulsion formation, in which said liquid is an aliphatic hydrocarbon having a boiling point above the emulsifying and reaction temperature and in which said emulsion is cast as a layer.

Claim 14

The process of forming a microporous solidified body as defined in claim 12 in which said body is a thin, microporoUs layer and said process includes the steps of depositing said emulsion in a thin layer on a supporting surface, providing means to prevent loss of non-solvent liquid from said emulsion on the face of said layer opposite said supporting surface before substantial

Claim 15

The process of forming a microporous solidified body as defined in claim 12 in which said body is a thin, microporous layer and said process includes the steps of depositing said emulsion in a thin layer on a supporting surface, providing means to prevent loss of non-solvent liquid from said emulsion on the face of said layer opposite said supporting surface before substantial reaction of said components, thereafter reacting said components to bring the layer to a solid state with said means in place and without substantial expansion of said layer, removing said means from said face after solidification of said reaction mixture and thereafter removing said non-solvent liquid from said layer.

Claim 16

The process of forming a microporous solidified body as defined in claim 16 in which said means to prevent loss of non-solvent liquid is an impervious flexible sheet material in contact with said face of said layer.

Claim 17

The process of forming a microporous solidified body as defined in claim 15 in which said means to prevent loss of non-solvent liquid is a layer of an organic liquid having a boiling point of at least about 100* C. and being substantially non-solvent for and non-reactive with said reactive material and being immiscible in said continuous phase.

Claim 18

The process of forming a microporous solidified body as defined in claim 16 in which said means to prevent loss of non-solvent liquid is a porous layer impregnated with an organic liquid having a boiling point of at least about 100* C., said liquid being substantially non-solvent for and non-reactive with said reactive material and being immiscible in said continuous phase.