NO151369B - MICROPOROUS POLYMER BODIES, PROCEDURES FOR PREPARING THESE AND USING THESE - Google Patents

Description

The invention relates to porous polymer bodies and a method for their production. The invention relates more specifically to

tuned microporous polymer bodies which can be easily produced and which are characterized by relatively homogeneous, three-dimensional, cell-containing microstructures, and a distinctively simple method for the production of microporous <p>polymer bodies and use thereof.

Several very different methods have previously been developed for the production of microporous polymer bodies. Such methods vary from what within the relevant technique is termed a classical phase inversion, to nuclear bombardment,

for the incorporation of microporous solid particles in a substrate and which are then leached, and for the sintering of microporous particles

laughing somehow. Previous attempts in this technical area have included additional methods and, moreover, countless variations of what can be considered the classic or basic

the methods.

Interest in microporous polymer products has been stimulated by the countless potential applications for materials of this type. These potential applications are well known and range from piston pads and similar articles to breathable leather-like sheets and to filter media. Nevertheless, despite the potential application possibilities, commercial exploitation has been relatively modest. In addition, the methods that are used commercially have various limitations that do not enable the richness of variety that is necessary for the application to gain entry into the potential market for micro-

porous products.

As mentioned, some commercially available micro-porous polymer products are produced by nuclear bombardment. With such a method, a relatively narrow pore size distribution can be achieved,

but the pore volume must be relatively low (i.e. below approx. 10%

voids) to ensure that the polymer will not degrade during manufacture. A number of polymers cannot be used in such a me-

tode due to the polymer not being etchable. Such a method also requires that a relatively thin sheet or film of polymer

must be applied, and a considerable amount of expertise must be drawn

in to perform the method to avoid "double tracking" which leads to the formation of excessively large pores.

The classic phase inversion has also been used on a technical scale for the production of microporous polymers from cellulose acetate and certain other polymers. The classical phase inversion is described in detail by R.E. Kesting in "Synthetic Polymeric Membranes", McGraw-Hill, 1971. It should be particularly noted that on page 117 of this book it is explicitly stated that this classic phase inversion involves the use of at least three components, i.e. a polymer, a solvent for the polymer and a non-solvent portion for the polymer.

Reference may also be made to US Patent No. 3,945,926 in which the formation of polycarbonate resin membranes from a casting solution containing the resin, a solvent and a swelling agent and/or non-solvent is described. It is stated in this patent document, column 15, lines 42 - 47, that in the complete absence of a swelling agent, the phase inversion will not normally take place, and that at low concentrations of swelling agents, s-structures with closed cells are formed.

It is therefore quite clear from the above that the classical phase inversion requires the use of a solvent for the system at room temperature, so that a number of other useful polymers cannot be used instead of such polymers as e.g.

cellulose acetate. Also in terms of production, the classic phase inversion ion process will usually be limited to the formation of films

■•"••due to the large amount of solvent that is used during the preparation of solutions and which must later be extracted. It also appears that the classic phase inversion requires relatively strong process control in order for structures with the desired configuration to be achieved. The relative concentrations of solvent, non-solvent and swelling agent must therefore be regulated very precisely, as described in US patent document no.

3 945 926, columns 14 - 16. To change the number, size

and the homogeneity of the obtained structure, conversely, the above-mentioned parameters must be changed by trial and error.

Other commercially available microporous polymers are prepared by sintering microporous particles of polymers that can range from high density polyethylene to polyvinylidene fluoride. However, it is difficult with such a method to obtain a product with the narrow pore size distribution required for a variety of applications.

A further general method which has previously been extensively used involves heating a polymer with various liquids to form a dispersion or solution which is then cooled, after which the liquid is removed with a solvent or similar material. This type of procedure is described in US Patent No. 3,607,793,

no. 3 378 507, no. 3 310 505, no. 3 748 287, no. 3 536 796, no. 3 308 073 and no. 3 812 224. It is assumed that the above-mentioned method has not been used on a technical scale in to any significant extent, if at all, presumably due to a lack of economic feasibility for the special processes that have previously been developed. The known processes also do not enable the production of microporous polymers that combine relatively homogeneous microcell-containing structures with the pore size and pore size distributions that are typically desired.

As regards the microporous polymers which have been obtained using known methods, none of the methods known to date have been able to give isotropic olefinic polymers or oxidation polymers in which the main proportion of the pore sizes lies within the range 0.1 - 5 ym, at the same time as they have a relatively narrow pore size distribution, and these polymers will thus have a strongly uneven pore size in a sample of the polymer. Certain known olefinic polymers or oxidation polymers have had pore sizes within the above-mentioned range, but without a relatively narrow pore size distribution, so that such materials have no particular value in such areas of application as filtration which require a high degree of selectivity. Moreover, known microporous olefinic polymers or oxidation polymers which can be stated to have relatively narrow pore size distributions have had absolute pore sizes that lie outside the above-mentioned range, and they generally have significantly smaller pore sizes, for use in such areas of application as ultrafiltration. Finally, a number of known olefinic polymers have had pore sizes within the above-mentioned range and what can be considered relatively narrow pore size distributions. However, such materials have been produced using such methods as stretching, which gives the obtained anisotropic material a strong degree of orientation, so that the material becomes undesirable for a number of areas of application. There has thus been a need for microporous olefinic polymers and oxidation polymers with a pore size within the range of 0.1 - 5 um and which are characterized by having a relatively narrow, isotropic pore size distribution.

It is also a significant disadvantage of a number of the hitherto available microporous polymers that they have a low flowability when used in objects such as microfiltration membranes. One of the main reasons for such a low flowability is the typically low void volume in a number of such polymers. Thus, perhaps 20% of the polymer object or less can be made up of a "cavity" volume through which the filtrate can flow, while the other 80% of the object is made up of the polymer resin that forms the microporous structure. There has thus also been a need for microporous polymers with a high void volume, especially as regards olefinic polymers.

The invention thus aims to provide microporous polymer bodies which are characterized by the fact that they are relatively homogeneous and have narrow pore size distributions.

The invention also aims to provide a . simple method that enables economical production of microporous polymer bodies.

: ; The invention also aims to provide a method for the production of microporous polymer bodies which can be used for a large number of useful thermoplastic polymers. A more special purpose of the invention

is to provide such a process which is capable of readily producing microporous polymer bodies from any synthetic thermoplastic polymer, including polyolefins, condensation polymers and oxidation polymers.

The invention further aims to provide microporous polymer bodies which can vary from thin films to relatively thick blocks.

Inventinne Isen thus relates to polymer bodies of the type specified in claim 1's preamble and which are characterized by the features specified in claim 1's characterizing part.

Furthermore, the invention relates to a method for the production of such polymer bodies, comprising the method features specified in claim 7's preamble, and the method is characterized by the features specified in claim 7's characterizing part.

The microporous bodies according to the invention are particularly suitable for use for the absorption and release of functional liquids.

The invention also applies to an application which according to claim 11.

The invention will be described in more detail under reference

to the drawings, of which

fig. 1 is a diagram of temperature versus concentration for a hypothetical polymer-liquid system, where the binodial and spinodal curves are shown and also the necessary concentration to obtain the microporous polymers and to be able to practically carry out the present method,

fig. 1A is a plot of temperature plotted against concentration, similar to Fig. 1, but also including the phase line for the freezing point depression,

fig. 2 is a photomicrograph with a magnification of 55X showing the macrostructure of a microporous polypropylene polymer according to the invention with a void volume of approx. 75%,

fig. 3 - 5 are microphotographs of the microporous polypropylene structure according to fig. 2 at magnifications of 550X, 2200X and 5500X, and shows a homogeneous cell structure,

fig. 6 - 10 are photomicrographs with a magnification of 1325X, 1550X, 1620X, 1450X and 1250X of additional microporous polypropylene structures and show the changes in the structure as the void volume is reduced from 90% to, respectively. 70%, 60%, 40% and 20%,

fig. 11 - 13 are photomicrographs with a magnification of 2000X, 2050X and 1950X of additional microporous polypropylene structures according to the invention and show the reduced cell size as the polypropylene content is increased from 10% by weight according to fig. 11 to respectively 20% by weight and 30% by weight according to fig. 12 and 13,

fig. 14 - 17 are photomicrographs with magnifications of 250X, 2500X, 2500X and 2475X of microporous LD polyethylene

structures according to the invention, of which fig. 14 and 15 show the macro- and microstructure for a microporous polymer containing 20% by weight of polyethylene, and fig. 16 and 17 show the microstructure with respectively 40% by weight and 70% by weight polyethylene,

fig. 18 and 19 are photomicrographs with a magnification of 2100X and 2000X of microporous HD polyethylene structures according to the invention and show the structures at 30% by weight and 70% by weight polyethylene,

fig. 20 and 21 are photomicrographs with a magnification of 2550X and 2575X of microporous SBR polymers according to the invention and show a homogeneous cell structure,

fig. 22 is an enlarged photomicrograph

2400X of a microporous methylpentene polymer,.

fig. 23 and 24 are photomicrographs with a magnification of

respectively 255X and 2550X of a microporous ethylene/acrylic acid copolymer,

fig. 25 is a photomicrograph at a magnification of 2500X of a microporous polymer made from a mixture of polyphenylene oxide and polystyrene;

fig. 26 is an enlarged photomicrograph

2050X and shows a "microporous polystyrene polymer,

fig. 27 is a photomicrograph at a magnification of 2000X showing a microporous polyvinyl chloride polymer,

fig. 28 and 29 are photomicrographs at 2000X magnification of microporous LD polyethylene polymers and show the partial masking of the base structure by the modified "foil" structure,

fig. 30 - 33 are mercury penetration curves for micro-porous polypropylene structures according to the invention and show the narrow pore diameter distribution which is typical for the polymers according to the invention,

fig. 34-40 are mercury intrusion curves for commercially available microporous products, including the polypropylene "Celgard" (Fig. 34), the polyvinyl chlorides. "Amerace 0" and "Amerace A30" (Figs. 35 and 36 respectively), the polypropylene "Porex" (Fig. 37), the cellulose acetate "Millipore BDWP 29300" (Fig. 38), the cellulose tri-acetate "Gelman TCM-200" and the acrylonitrile/polyvinyl chloride polymer

"Gelman Acropor WA" (fig. 39 and 40 respectively),

fig. 41 - 4 3 are mercury penetration curves for micro-porous structures prepared according to US patent document no. 3,378,507 and using polyethylene (fig. 41 and 42) and polypropylene (fig. 43),

fig. 44 is a mercury intrusion curve for a microporous polyethylene material prepared according to US Patent No. 3,310,505,

fig. 45 - 4 6 are microphotographs of a porous polyethylene product produced by imitating example 2 according to US Patent No. 3,378,507 using an injection molding machine, as fig. 45 (magnification 240X) shows the macrostructure and fig. 46 (magnification 2400X) shows the microstructure,

fig. 47 - 48 are photomicrographs of a porous polyethylene product produced by imitating example 2 according to US Patent No. 3,378,507 using a compression molding method, as fig. 47 (magnification 195X) shows the macrostructure and fig. 48 (for-magnification 2000X) shows the microstructure,

fig. 49 - 50 are photomicrographs of a porous polypropylene product produced by imitating example 2 according to US Patent No. 3,378,507 using an injection molding method, as fig. 49 (magnification 195X) shows the macrostructure and fig. 50 (magnification 2000X) shows the microstructure,

fig. 51 - 52 are photomicrographs of a porous polypropylene product produced by imitating example 2 according to US Patent No. 3,378,507 using a compression molding method, as fig. 51 (magnification 206X) shows the macrostructure and fig. 52 (magnification 2000X) shows the microstructure, and

fig. 53 - 54 are microphotographs of a porous polyethylene product produced by imitating example 2 according to US Patent No. 3,310,505, as fig. 53 (magnification 205X) shows the macrostructure and fig. 54 (magnification 2000X) shows the microstructure,

fig. 55 shows a melting curve and a crystallization curve for a system of polypropylene and quinoline polymer/liquid,

fig. 56 shows a melting curve and several crystallization

tion curves for a system of polypropylene and N,N-bis(2-hydroxy-ethyl) tallow amine polymer/liquid,

fig. 5 7 shows a melting curve and a crystallization curve for a system of polypropylene and dioctyl phthalate polymer/liquid and shows a system that does not lie within the scope of the present invention,

fig. 58 shows the phase diagram1 for a system of low molecular weight polyethylene and diphenyl ether polymer/liquid, determined at a cooling rate and a heating rate of 1°C/minute,

fig. 59 shows several melting and crystallization curves for a system of low molecular weight polyethylene and diphenyl ether polymer/liquid,

fig. 60 shows a glass transition curve for a system of low molecular weight polystyrene and 1-dodecanol polymer/liquid,

fig. 61 is a photomicrograph at a magnification of 5000X of a microporous cell structure according to the invention with 70% voids and made from polymethyl methacrylate,

fig. 62 shows melting and crystallization curves for a system of "Nylon 11" and tetramethylene sulfone polymer/liquid,

fig. 63 is a photomicrograph at a magnification of 2000X of a microporous cellular structure according to the invention with 70% voids and made from "Nylon 11",

fig. 64 is a photomicrograph at a magnification of 2000X of a microporous cellular structure according to the invention with 70% voids and made from polycarbonate,

fig. 65^é"t photomicrograph i with a magnification of 2000X of a microporous cell structure according to the invention with 70% voids and made from polyphenylene oxide,

fig. 66 and 67 are microphotographs with a magnification of 2000X of a microporous, non-cellular structure according to the invention with cavities of respectively 60% and 75% and made from polypropylene,

fig. 68 and 69 show mercury penetration curves for a non-cellular microporous polypropylene structure according to the invention with respectively 60% void and 75% void, and

fig. 70 is a diagram showing the distinctive microporous

see cell structures according to the invention compared to certain known materials.

According to the invention, it has been shown that any synthetic, thermoplastic polymer can be made microporous by first heating the polymer and a compatible liquid, as discussed in more detail below, to a temperature and for a sufficient time that a homogeneous solution will form. The thus formed solution is then allowed to assume a desired shape and is then cooled with this shape at a rate and to a temperature sufficient for a thermodynamic, non-equilibrium liquid-liquid phase separation to be initiated. As the solution cools to the desired shape, no mixing or other shearing force is used while the solution cools. The cooling is continued so that a solid material is obtained. The solid material only needs to achieve sufficient mechanical strength so that it can be handled without it breaking down physically. Finally, at least a significant proportion of the compatible liquid is removed from the obtained solid material to form the desired microporous polymer.

The new microporous olefinic polymer bodies and oxidation polymer bodies according to the invention are distinctive in that they have a narrow pore size distribution, more precisely when measured by mercury penetration. The narrow pore size distribution can be analytically expressed as a sharpness function "S" which is explained in detail below. The "S" value for the olefinic polymer and oxidation polymer according to the invention varies from 1 to 10. These polymers according to the invention are also distinctive in that they have average pore sizes that vary from 0.10 to 5 µm, with 0.2 to 1 ym is preferred. Moreover, such microporous products are essentially isotropic and thus have essentially the same cross-sectional configuration when analyzed along any spatial plane.

According to one embodiment of the invention, the method is carried out in the production of microporous polymers such that a mixture comprising a synthetic thermoplastic polymer, in particular a polyolefin, and an ethylene/acrylic acid copolymer, a mixture of polyphenylene oxide and polystyrene or a mixture of one or more of the above polymers, and a compatible liquid is heated to a temperature and for a sufficient time that a homogeneous solution will form. The solution is then cooled so that essentially at the same time a number of small liquid droplets of essentially the same size are formed. The cooling is then continued in order for the polymer to solidify, and at least a significant proportion of the liquid is removed from the obtained solid material to form the t desired cell polymer bodies.

In the above-mentioned method, microporous polymer products are obtained which are characterized by a cellular, three-dimensional, cavity-containing microstructure, i.e. a number of enclosed cells with an essentially spherical shape and with pores or channels that connect neighboring cells to each other. The basic structure is relatively homogeneous, and the cells are evenly distributed in all three dimensions, and the interconnecting pores have diameters that have a relatively narrow size distribution, as measured by mercury penetration. For convenience, microporous polymers having such a structure will hereafter be referred to as "cellular".

Another part of the invention provides new microporous polymer products which behave like solid materials and which contain relatively large amounts of functionally useful liquids, such as e.g. polymer additives including flame retardants and the like. In this way, useful liquids can have the further processing advantages associated with a solid material that can be used directly, e.g. in a premix. Such products can be formed directly by using a functional fluid as the compatibilizing fluid and not removing the compatibilizing fluid, or indirectly by refilling the microporous polymer after the compatibilizing fluid has been removed, or by displacing the compatibilizing fluid. before the removal to incorporate the functional fluid.

The present process generally involves heating the desired polymer with a suitable compatible liquid to form a homogeneous solution which is suitably cooled to form a solid material, after which the liquid is extracted to form a microporous material.

As indicated above, the present invention surprisingly provides a method for making any synthetic thermoplastic polymer microporous. The present method can thus be used for olefinic polymers, condensation polymers and oxidation polymers.

Examples of useful non-acylic polyolefins include LD polyethylene, HD polyethylene, polypropylene, polystyrene, polyvinyl chloride, acrylonitrile/butadiene/styrene terpolymers, styrene/acrylonitrile copolymers, styrene/butadiene copolymers, poly(4-methyl-pentene-1), polybutylene , polyvinylidene chloride, polyvinyl butyral, chlorinated polyethylene, ethylene/vinyl acetate copolymers, polyvinyl acetate and polyvinyl alcohol.

Useful acrylic polyolefins include polymethyl methacrylate, polymethyl acrylate, ethylene/acrylic acid copolymers and ethylene/acrylic acid metal salt copolymers.

Polyphenylene oxide is representative of the oxidation polymers that can be used. The useful condensation polymers include polyethylene terephthalate, polybutylene terephthalate, Nylon 6, Nylon 11, Nylon 13, Nylon 66, polycarbonates and polysulfone.

For carrying out the present method it is

only necessary first to select the synthetic thermoplastic polymer to be made microporous. After the polymer has been selected, the next step is to select the suitable compatible liquid and the relative amounts of polymer and liquid that can be used. Of course

mixtures of one or more polymers can be used in the execution of the present method. Functionally, the polymer and liquid are heated with stirring to the temperature necessary to form a clear, homogeneous solution. If a solution cannot be formed at any liquid concentration, the liquid is unsuitable and cannot be used with the particular polymer.

Because of the selectivity, it is not possible with absolute certainty to make any prediction to determine in advance whether a particular liquid is usable with a particular polymer. However, some useful general guidelines can be given. Thus, when the polymer in question is non-polar, it is more likely that non-polar liquids with similar solubility parameters at the dissolution temperature can be used. If such parameters are not available, reference can be made as a general guideline to the more readily available parameters for solubility at room temperature. Similarly, polar organic liquids with similar solubility parameters should first be examined when polar polymers are used. Also, the relative polarity or non-polarity of the liquid should be matched to the relative polarity or non-polarity of the polymer. In addition, useful liquids for use with hydrophobic polymers will typically have little or no solubility in water. On the other hand, polymers that tend to be hydrophobic will generally require a liquid that has some solubility in water.

In terms of suitable liquids, special groups of different types of organic compounds have proven useful, including aliphatic and aromatic acids, aliphatic, aromatic and cyclic alcohols, aldehydes, primary and secondary amines, aromatic and ethoxylated amines, diamines, amides, esters and diesters, ethers, ketones and various hydrocarbons and heterocyclic compounds. However, it should be noted that this recognition is highly selective. Thus, e.g. not all saturated aliphatic acids can be used, and furthermore, not all liquids that can be used together with HD-polyethylene necessarily need to be used together with e.g. polystyrene.

It will be understood that the applicable relative amounts of polymer and liquid for a particular system can easily be determined from an assessment of the parameters discussed in more detail below.

When mixtures of one or more polymers are used, it will be understood that useful liquids must typically be able to be used together with all the polymers in question. However, it may be possible that the polymer mixture has such properties that the liquid will not be usable together with all relevant polymers. As an example, it can be mentioned that if one or more polymeric components are present in such relatively small quantities that they will not significantly affect the properties of the mixture, the liquid used only needs to be usable together with the main polymer or the main polymers.

Although most applicable materials are liquids at ambient temperature, materials that are solid at room temperature can also be used as long as solutions can be formed together with the polymer at an elevated temperature and the material is not unhealthy, affecting the formation of microporous structures. More specifically, a solid material can be used as long as phase separation occurs by liquid/liquid separation instead of by liquid/solid separation during the cooling step, which is discussed in more detail below. The amount of liquid used can usually be varied from approx. 10 to approx. 90%.

As mentioned above, any synthetic thermoplastic polymer can be used as long as the selected liquid forms a solution together with the polymer and the concentration gives a continuous polymer phase with separation during cooling, as further discussed below. In order to gain an understanding of the scope of the applicable systems of polymer and liquid, it may be useful to have a brief summary of some of these systems.

When microporous polymers are formed from polypropylene, it has been shown that alcohols such as 2-benzylamino-l-propanol and 3-phenyl-1-propanol, aldehydes such as salicylaldehyde, amides such as N,N-diethyl-ni-to luamide, amines such as N -hexyldiethanolamine, N-behenyldiethanolamine, N-coco diethanolamine, benzylamine, N,N-bis-3~hydroxyethylcyclohexylamine, diphenylamine and 1,12-diaminododecane, esters such as methyl benzoate, benzyl benzoate, phenyl salicylate, methyl salicylate and dibutyl phralate, and ethers such as diphenyl ether, 4-bromodiphenyl ether and dibenzyl ether are useful. In addition, halogen hydrocarbons such as 1,1,2,2-tetrabromoethane, and hydrocarbons such as trans-stilbene and other alkyl/aryl phosphites are also usable, in the same way as ketones such as methylnonyl ketone.

In the production of microporous polymers from HD polyethylene, it has been shown that a saturated aliphatic acid such as decanoic acid, primary saturated alcohols such as decyl alcohol and 1-dodecanol, secondary alcohols such as 2-undecanol and 6-undecanol, ethoxylated amines such as N-lauryldiethanolamine, aromatic amines such as N,N-diethylaniline, diesters such as dibutyl sebacate and dihexyl sebacate, and ethers such as diphenyl ether and benzyl ether are useful. Other useful liquids include halogenated compounds such as octabromodiphenyl, hexabromobenzene and hexabromocyclodecane, hydrocarbons such as 1-hexadecane, diphenylmethane and naphthalene, aromatic compounds such as acetophenone and other organic compounds such as alkyl/aryl phosphites, and quinoline and ketones such as methylnonyl ketone.

For the production of microporous polymers from LD polyethylene, the following liquids have been found to be useful: saturated aliphatic acids including hexanoic, caprylic, decanoic, undecanoic, lauric, myristic, palmitic and stearic acids, unsaturated aliphatic acids including oleic and erucic acids, aromatic acids including benzoic acid, phenylstearic acid, polystearic acid and xylylbehenic acid and other acids including branched carboxylic acids with an average chain length of 6, 9 and 11 carbon atoms, tall oleic acids and natural resin acid, primary saturated alcohols including 1-octanol, nonyl alcohol, decyl alcohol, 1-decanol, l^dodecanol , tridecyl alcohol, cetyl alcohol and 1-hepta-decanol, primary unsaturated alcohols including undecylenyl alcohol and oleyl alcohol, secondary alcohols including 2-octanol, 2-undecanol, dinonylcarbinol and diundecylcarbinol, and aromatic alcohols including 1-phenylethanol, 1-phenyl-l-pentanol, nonylphenol, phenylstearyl alcohol and 1-naphthol. Other useful hydroxyl-containing compounds include polyoxyethylene ether of oleyl alcohol and a polypropylene glycol having an average molecular weight of about 400. Additional useful liquids include cyclic alcohols such as 4, tert. butylcyclohexanol and menthol, aldehydes including salicylaldehyde, primary amines such as octylamine, tetradecylamine and hexadecylamine, secondary amines such as bis-(l-ethyl-3-methylpentyl)amine, and ethoxylated amines including N-lauryldiethanolamine, N-tallowdiethanolamine, N-stearyldiethanolamine and N-coco diethanolamine.

Additional useful liquids include aromatic ethers including N-sec-butylaniline, dodecylaniline, N,N-dimethylaniline, N,N-diethylaniline, p-toluidine, N-ethyl-o-toluidine, diphenylamine and aminodiphenylmethane, diamines including N-erucyl-1 ,3-propanediamine <p>g 1,8-diamine-p-menthane, other amines including branched tetraamines and cyclododecylamine, amides including cocoamide, hydrogenated tallow amide, octadecylamide, eruciamid, N,N-diethyltoluamide and N-trimethylolpropane stearamide , saturated aliphatic esters comprising methyl caprylate, ethyl laurate, isopropyl myristate, ethyl palmitate, isopropyl palmitate, methyl stearate, isobutyl stearate and tridecyl stearate, unsaturated esters comprising stearyl acrylate, butyl undecylenate and butyl oleate, alkoxy esters comprising butoxyethyl stearate and butoxyethyl oleate, aromatic esters comprising vinyl phenyl stearate, isobutyl phenyl stearate, tridecyl phenyl stearate, methyl benzoate, ethyl -benzoate, butyl benzoate, benzyl benzoate, phenyl laurate, phenyl salicylate, methyl salicylate and benzylac etate, and diesters including dimethyl phenylene distearate, diethyl phthalate, dibutyl phthalate, diisooctyl phthalate, dicapryl adipate, dibutyl sebacate, dihexyl sebacate, diisooctyl sebacate, dicapryl sebacate and dioctyl maleate. Additional useful liquids include polyethylene glycol esters including polyethylene glycol (with an average molecular weight of about 400), diphenyl stearate, polyhydroxy esters including castor oil (triglyceride), glycerol monostearate, glycerol monooleate, glycerol distearate, glycerol dioleate and trimethylolpropane monophenylstearate, ethers including diphenyl ether and benzyl ether, halogenated compounds including hexachlorocyclopentadiene, octabromobiphenyl, decabromodiphenyl oxide and 4-bromodiphenyl ether, hydrocarbons including 1-nonene, 2-nonene, 2-undecene, 2-heptadecene, 2-nonadecene, 3-eicosene, 9-nonadecene, diphenylmethane, triphenylmethane and trans- stilbene, aliphatic ketones including 2-heptanone, methylnonyl ketone, 6-undecanone, methylundecylketone, 6-tridecanone, 8-pentadecanone, 11-pentadecanone, 2-heptadecanone, 8-heptadecanone, methylheptadecylketone, dinonyl ketone and distearyl ketone, aromatic ketones including acetophenone and benzo-phenone, and other ketones including xanthon. Still other useful liquids include phosphorus compounds including trixyl-nyl phosphate, polysiloxanes, "Muget hyacinth (An Merigenaebler, Inc), "Terpineol Prime No. 1" (Givaudan-Delawanna, Inc) ,'Bath Oil Fragrance #5864 K" (Inrernational Flavor & Fragrance, Inc), "Phosclere P315C" (organophosphite), "Phosclere P576 " (organophosphite), styrenated nonylphenol, quinoline and quinalidine.

In the manufacture of microporous polymer products from polystyrene, the applicable liquids include tris-halogenated propyl phosphate, aryl/alkyl phosphites, 1,1,2,2-tetrabromoethane, tribromone-pentyl alcohol, 40% "Voranol CP. 3000<H>polyol and 60% tribromo-neo-pentyl alcohol, tris-3-chloroethyl phosphate, tris-(1,3-dichloroisopropyl)-phosphate, tri-(dichloropropyl)-phosphate, dichlorobenzene and 1-dodecanol.

In the production of microporous polymers using polyvinyl chloride, the usable liquids include aromatic alcohols including methoxybenzyl alcohol, 2-benzylamino-1-propanol and other hydroxyl-containing liquids including 1,3-dichloro-2-propanol. Still other useful liquids include halogenated compounds including "Firemaster T33P" (tetrabromophthalic acid diester) and aromatic hydrocarbons including trans-stilbene.

Moreover, according to the invention, microporous products have been produced from other polymers and copolymers and mixtures. For the production of microporous products from styrene/butadiene copolymers, the applicable liquids thus include decyl alcohol, -N-tallow diethanolamine, N-coco diethanolamine and diphenylamine. Useful liquids in the production of microporous polymers from ethylene/acrylic acid copolymer salts include N-tallow diethanolamine, N-coco diethanolamine, dibutyl phthalate and diphenyl ether. Microporous polymer products using impact resistant polystyrene can be prepared using hexabromobiphenyl and alkyl/aryl phosphites as liquids. Using "Noryl" mixture of polyphenylene oxide and polystyrene, microporous polymers can be produced using N-coco diethanolamine, N-tallow diethanolamine, diphenylamine, dibutyl phthalate and hexabromophenol. Microporous polymers from mixtures of LD polyethylene and chlorinated polyethylene can be prepared using 1-dodecanol, diphenyl ether and N-tallow diethanolamine. When 1-dodecanol is used as the liquid, microporous polymer products can be prepared from the following blends: polypropylene/chlorinated polyethylene, HD polyethylene/chlorinated polyethylene, HD polyethylene/polyvinyl chloride and HD polyethylene and acrylonitrile/butadiene/styrene (ABS) terpolymers. In the production of microporous products from polymethyl methacrylate, 1,4-butanediol and lauric acid have proven to be useful. Microporous Nylon 11 can be produced using ethylene carbonate, 1,2-propylene carbonate or tetramethylene sulphone. Menthol can also be used for the production of microporous products from polycarbonate.

Selection of concentrations for polymer and liquid

The determination of the amount of liquid to be used is obtained with reference to the binodial and spinodal curves for the system, typical curves of which are shown in fig. 1. It appears from this that Tm represents the maximum temperature for the binodial curve (i.e. the maximum temperature for the system at which binodial splitting will take place), T ^ represents the upper critical solution temperature (i.e. the maximum temperature at which spinodal splitting will take place), ø <1> mrepresents the polymer concentration at Tm, ø*c denotes the critical concentration and ø"x denotes the polymer concentration for the system that is necessary to obtain the distinctive microporous polymer structures according to the invention. Theoretically, ø"m and øc should be practically identical , It is known, however, that due to molecular weight distributions in commercially available polymers, øc can be approx. 5% by weight higher than the value for For the production of the distinctive microporous polymers according to the invention, the polymer concentration ø"x used for a particular system must be greater than øc. If the polymer concentration is less than øc, the phase separation that occurs after as the system cools, form a continuous liquid phase with a discontinuous polymer phase. If, on the other hand, the correct polymer concentration is used, it will be ensured that the continuous phase that will form on cooling to the phase separation temperature will be the polymeric phase necessary for to obtain the distinctive microcell structures according to the invention. It will also appear that for the formation of a continuous polymer phase by phase separation, it is required that a solution is initially formed. When the present method is not followed and a dispersion is initially formed, the obtained micro-porous product similar to that obtained by sintering polymeric particles r.

It will therefore be understood that the applicable polymeric concentration or amount of liquid will vary for each system. Suitable phase diagram curves for several systems have already been developed. If, however, a suitable curve is not available, this can easily be developed using known techniques. A suitable technique is described e.g. in Smolders, van Aartsen and Steenbergen, Kolloid - Z.u.z. Polymers, 243, 14 (1971).

A more general diagram of temperature versus concentration for a hypothetical polymer-liquid system is shown in Fig. IA. The portion of the curve from y to a represents thermodynamic equilibrium for liquid-liquid phase separation. The portion of the curve from a to 3 represents equilibrium for liquid-solid phase separation which will be recognized as the normal freezing point depression curve for a hypothetical liquid-polymer system. The upper shaded area represents an upper liquid/liquid immiscibility that may be present in some systems. The dotted line represents the lowering of the crystallization temperature due to cooling at a sufficient rate to cause thermodynamic nonequilibrium liquid-liquid phase separation. The flat part of the curve for the crystallization in relation to the composition defines a usable composition range which is a function of the applied cooling rate, as discussed in more detail below.

For any given cooling rate, the crystallization temperature can thus be set in relation to the percentage amount of resin or compatible liquid, and in this way the liquid/polymer concentration ranges can be determined which will give the desired microporous structures with the given cooling rate. For crystalline polymers, the determination of the above crystallization curve is a useful alternative to determining a phase diagram as shown in fig. 1. As an example of the above, reference should be made to fig. 55 which is a diagram of the temperature in relation to the polymer/liquid concentration and which shows the melting curve at a heating rate of 16° C per minute and the crystallization curve for polypropylene and quinoline over a wide concentration range. It appears from the crystallization curve that at a cooling rate of 16° C per minute, the suitable concentration range extends from approx. 20% polypropylene to approx. 70% polypropylene.

Fig. 56 is a curve for temperature in relation to the polymer/liquid composition for polypropylene and N,N-bis-(2-hydroxyethyl)-tallow. The upper curve is a deposit for the melting curve at a

o heating rate of 16 C per minute. The lower curves are in descending order and deposits of the crystallization curve at cooling rates of respectively 8° C, 16° C, 32° C and 64° C per minute. The curves show two simultaneous phenomena when the cooling rate increases. First, the flat part of the curve, which shows a relatively stable crystallization temperature over a wide concentration range, is lowered with an increased cooling rate, and this shows that the faster the cooling rate, the lower the relevant crystallization temperature.

The other phenomenon that can be observed is the change in the slope of the crystallization curve that occurs when the cooling rate is changed. It thus appears that the flat area for the cross-tallization curve expands as the cooling rate increases. It can thus be assumed that by increasing the cooling rate, a corresponding increase in the applicable concentration range can be achieved for the formation of the microporous structures according to the invention and for the practical implementation of the present method. It appears from the above that in order to determine the applicable concentration ranges for a given system, it is only necessary to prepare a few representative concentrations for polymer/liquid and to cool these at some desired rate. After the crystallization temperatures have been plotted on the diagram, the applicable concentrations will clearly appear.

Fig. 5 7 is a curve for the temperature in relation to the polymer/liquid concentration for polypropylene and dioctyl phthalate. The upper curve represents the melting curve for the system within a concentration range, and the lower curve represents the crystallization curve within the same concentration range. As the crystallization curve does not have a flat region within which the crystallization temperature remains essentially constant for a concentration range, it was not expected that the polypropylene/dioctyl phthalate system would be useful for forming microporous structures, and in fact it is not the.

To gain an understanding of the excellent relationship between the phase diagram method for determining applicable polymer and liquid concentration ranges and the crystallization method for making such a determination, reference may be made to FIG. 58 and 59. ig. 58 is a phase diagram for a system of low molecular weight polyethylene and diphenyl ether polymer and liquid determined by a conventional light scattering method using a temperature controlled container. It appears from the phase diagram in fig. 58 that Tm is approx. 135° C and that Øm is at approx. 7% polymer. It also appears that at a polymer concentration of approx. 45% intersects the flash point curve with the freezing point depression curve, and this suggests a usable concentration range from approx. 7% polymer to approx. 45% polymer.

The applicable area determined from fig. 58 can be compared with the area that can be determined from fig. 59 which shows the melting curve for the same system at heating rates of 8° C and 16° C per minute and crystallization curves for the system at cooling rates of 8° C and 16° C per minute. It appears from the crystallization curves that their essentially flat part extends from something below a concentration of 10% polymer to approx. 42 - 4 5% polymer, depending on the cooling rate. The results obtained from the crystallization curves thus agree surprisingly well with the results obtained from the fading point phase diagram.

For non-crystalline polymers, it is believed that one plot of temperature versus concentration for the glass transition temperature may be referred to as an alternative to referring to a phase diagram such as that shown in Fig. 1. Fig. 58 is thus a graph of temperature versus concentration for the glass transition temperature of low molecular weight polystyrene sold under the trade name "Piccolastic D-125", and 1-dodecanol at various concentration values.

It appears from fig. 58 that "from about 8% polymer to about

50% polymer, the glass transition temperature for polystyrene/1-dodecanol is essentially constant. It has hitherto been suggested that concentrations along the essentially flat part of the glass transition curve would be applicable for carrying out the present method, analogously to the flat part for the above-mentioned crystallization curves. It thus appears that a useful alternative for determining the phase diagram for non-crystalline polymer systems is to determine the glass transition curve and to work within the essentially flat region of such a curve.

For all of the above figures, the crystallization temperatures were determined with a DSC-2 type differential scanning calorimeter or comparable apparatus. Further effects of cooling rates in the execution of the present method are discussed in more detail below.

After the desired synthetic thermoplastic polymer, the compatible liquid and the potentially applicable concentration range have been selected, it is necessary to select e.g. the actual concentration of polymer and liquid that will be used. For-, without taking into account e.g. the theoretically possible concentration range, other functional considerations should be used to determine the relative amounts used for a particular system. As regards the maximum amount of liquid that should be used, the obtained firmness properties must therefore be taken into account. More specifically, the amount of liquid used should thus enable the resulting microporous structure to have a sufficient minimum "handling strength" to avoid a microporous or cell-containing structure from collapsing. On the other hand, the choice of the maximum amount of resin and viscosity limitations of the particular equipment used may dictate the tolerable maximum content of polymer or resin. Moreover, the amount of polymer used should not be so large that it causes the cells or other areas of microporosity to be closed.

The relative amount of liquid used will also depend to a certain extent on the desired effective size for the micro-porosity, which e.g. the special requirements for cell and pore sizes for the intended end use. Thus, e.g. the average cell and pore size tends to increase somewhat with increasing liquid content.

In any case, the applicability of a liquid and a useful concentration thereof for a given polymer can be easily determined experimentally using the liquid, as described above.

The parameters mentioned above should of course be maintained. It will be readily understood that mixtures of two or more liquids may be used, and the applicability of a particular mixture may be determined, as described herein. Although a particular mixture may be applicable, it will be understood that one or more of the liquids may also be unsuitable if used alone.

It will be understood that the particular amount of liquid used will also often be dictated by the particular calculated end use. As typical examples of special examples where HD-polyethylene and N,N-bis(2-hydroxyethyl)-talgamine are used, useful microporous products can be produced by using 30-90% by weight of amine, preferably 30-70% by weight. When LD-polyethylene and the same amine are used, the amount of liquid can be advantageously varied within the range from 20 - 90% by weight, preferably 20 - 80% by weight. In contrast, systems with LD-polyethylene when diphenyl is used as liquid will not contain more than approx. 80% of the liquid, and a maximum liquid quantity of approx. 60% is preferred. When 1-hexadecene is used together with LD-polyethylene, amounts of up to approx. 90% or more is advantageously used. When polypropylene is used together with the tallow amine described above, it is advantageous to use the amine in an amount of 10-90%, the largest amount of not exceeding approx. 85% is preferred. When polystyrene is used together with 1-dodecanol, the alcohol concentration can vary from 20 to 90%, preferably 30 to 70%. When styrene/butadiene copolymers are used, the amine content can vary from 20 to 90%. When a system of decanol and styrene/butadiene copolymer (ie -SBR) is used, the liquid content can advantageously vary from 40 to 90%, and with diphenylamine it is advantageous for the liquid content to lie within the range from 50 to 80%. When microporous polymers are prepared from the amine and an ethylene/acrylic acid copolymer, the liquid content can vary within the range from 30 to 70%, and with diphenyl ether the liquid content can vary from 10 to 90%, as is the case when dibutyl phthalate is used as solvent.

Formation of the homogeneous liquid

After the solution has been prepared, it can be further processed into any desired shape or configuration. Depending on the particular system used, the thickness of the object can usually vary from a thin film of approx. 0.0254 mm or less into a relatively thick block with a thickness of approx. 6.4 cm or more. The ability to produce blocks thus allows the microporous material to be further processed into any intricate desired shape, such as using conventional extruding, injection molding or other related methods. The practical trade-offs that must be made when determining the range of thicknesses that can be produced from a particular system include

the rate at which the viscosity increases for the system as it cools. The higher the viscosity, the thicker the structure can usually be produced. The structure can therefore have any thickness as long as a strong phase separation does not occur, i.e. that 2 separable layers become visually clear.

It will be understood that if liquid-liquid phase separation is allowed to take place under thermodynamic equilibrium conditions, the result will be a complete separation into two separate layers. A layer consists of molten polymer containing the soluble amount of liquid and a liquid layer containing a soluble amount of polymer in the liquid. This condition is represented by the biodial line in the phase diagram in fig. 1 and IA. It appears that a limitation regarding the size of the object that can be produced is conditioned by the material's heat transfer properties because if the object is sufficiently thick and the heat transfer is sufficiently poor, the cooling rate in the center of the object can be sufficiently slow that it will approach thermodynamic equilibrium conditions and lead to to a clear layer phase separation, as mentioned above.

o

An increased thickness can also be obtained by adding smaller amounts of thixotropic materials. The addition of e.g. commercially available colloidal silicon oxide before cooling will greatly increase the useful thicknesses, but not adversely affect

the distinctive microporous structure. The particular amounts that can be used can be easily determined.

Cooling of the foomogenic solution

It is clear from the above discussion that regardless of the type of treatment (e.g. molding into a film or the like), the solution must be cooled until it forms a product that behaves like and looks like a solid material. The material obtained should be sufficiently cohesive that it will not crumble during handling, e.g. in the hand. A further investigation to determine whether the claimed system has the desired structure is to use a solvent for the liquid used, but not for the polymer. If the material breaks, the system used did not satisfy the necessary conditions.

The cooling rate of the solution can be varied within wide limits. In the usual cases, in reality, no external cooling needs to be used, and it is satisfactory simply, e.g. casting a film by pouring the hot liquid system onto a metallic surface heated to a temperature that enables the film to be pulled out, or forming a block by pouring the hot liquid system onto a substrate under the ambient conditions.

As mentioned above, the cooling rate must be sufficiently rapid that liquid/liquid phase separation will not take place under thermodynamic equilibrium conditions. Moreover, the cooling rate must exert a significant effect on the microporous structure obtained. For a number of polymer/liquid systems, if the cooling rate is sufficiently slow, but still such that it satisfies the above-mentioned conditions, the liquid/liquid phase separation will essentially simultaneously lead to the formation of a number of small liquid droplets of essentially the same size. If the cooling rate is such that a number of small liquid droplets are formed, provided that all other conditions mentioned herein have been satisfied, the microporous polymer obtained will have the cellular microstructure as defined above.

It is generally assumed that the distinctive structures for the microporous polymers according to the invention are obtained by cooling the liquid system to a temperature below the binodial curve, as shown in fig. 1, so that the liquid/liquid phase separation is initiated. At this stage, nuclei will begin to form consisting mainly of pure solvent. When the cooling rate is such that the cell-containing microstructure is obtained, it is also assumed that as each such seed continues to grow, it will be surrounded by a polymeric region that will increase in thickness as it becomes poorer in liquid. Finally, this polymer-rich region resembles a skin or film covering the growing small solvent droplets. As the polymer-rich region continues to thicken, the diffusion of additional solvent through the skin slows, and droplet growth decreases accordingly until it effectively ceases, and the droplet has then reached its maximum size. At this stage, a formation of a new seed is more likely than a continued growth of the large solvent droplet. However, in order to achieve this mode of growth, it is necessary that nucleation is initiated by spinodal fission instead of by binodial fission.

The cooling is thus carried out in such a way that essentially at the same time a number of small liquid droplets of essentially the same size are formed in a continuous polymer phase. If this mode of cleavage does not take place, the cell-containing structure will not be reached. The suitable mode of cleavage is usually obtained by applying such conditions which ensure that the system does not enter thermodynamic equilibrium until at least nucleation or droplet growth has been initiated. Process-wise, this can be achieved by simply allowing the system to cool without subjecting it to mixing or other shearing forces. The time parameter can also be of importance if relatively thick blocks are formed because a more rapid cooling is desired in such cases.

Within the area where cooling leads to the formation of a number of small liquid droplets, there is a general indication that the cooling rate can affect the size of the cells obtained, as increasing the cooling rate leads to smaller cells. In this connection, it has been observed that an increase in the cooling rate from approx. 8° C per minute will apparently lead to a reduction in cell size to half for a microporous polypropylene polymer. If desired, external cooling can therefore be used to regulate the final cell and pore size, as discussed in more detail below.

The way in which the interconnecting channels or pores are formed in the cell structure is not fully understood. It is desirable]-

keS not to be bound to any particular theory, but there are various possible mechanisms that can serve to explain this phenomenon and each of which is in accordance with the knowledge presented in the present description. The pore formation may therefore be due to thermal shrinkage of the polymer phase on cooling, as the small droplets of the liquid solvent behave as incompressible spheres when the solvent has a lower coefficient of expansion than the polymer. Furthermore, as indicated above, even after the solvent droplets have reached their maximum size, the polymer-rich phase may still contain some residual solvent and vice versa. As the system continues to cool, further phase separation can therefore occur. The residual solvent in the polymer-rich skin can therefore diffuse to the solvent drop with a decrease in the polymer-rich skin's volume and with an increase in the solvent drop's volume. It is believed that this may weaken the polymer skin, and the increase in volume for the solvent or liquid phase may lead to an internal pressure that will be able to break the polymer skin so that neighboring solvent droplets connect with each other. In connection with this latter mechanism, the polymer can be subjected to a renewed self-distribution to a more compact state as the residual liquid migrates out through the polymer skin, as e.g. by crystallization when this type of polymer is used. In such a situation, it is likely that the polymer skin obtained will shrink and have imperfections or small openings which are likely to occur within the areas that are particularly weak. It can be expected that the weakest areas will occur between neighboring liquid droplets, and in such a situation the small openings will form between neighboring liquid droplets and cause the solvent droplets to connect with each other. Regardless of the mechanism, in any case, interconnected pores or channels will inevitably form when the process is carried out as indicated in the present description.

Another explanation for the mechanism that causes the pores to form is based on the "Marangoni effect" which has been discussed in Marangoni, C. Nuovo Cimento [2] 5-6.239 (1871; [3], 3,97,193

(1878) and Marangoni, C. Ann. Phys. Lp. (1871), 143,337. The Marangoni effect has been used to explain the phenomenon that occurs when alcoholic beverages spontaneously flow back from the sides of drinking glasses, and in particular the mechanism that occurs when a condensed small droplet flows back into the bulk of the liquid. The fluid in the drop first penetrates through the fluid in the bulk of the liquid, followed by a rapid return of part of the liquid into the drop. It has been hypothesized that a similar physical phenomenon takes place for the liquid droplets that have been formed as a result of liquid/liquid phase separation Thus, a drop may impinge on another drop, and the fluid in one drop may penetrate the fluid in another drop, followed by a rapid separation of the two drops, possibly leaving a portion of the liquid as connecting the two droplets and forming the basis of the interconnected pores of the cell structure For a more recent discussion of the Marangoni effect, reference may be made to Charles & Mason, J. Colloid Sc:, 15, 236-267 (1960).

If the cooling of the homogeneous solution takes place at a sufficiently high rate, liquid/liquid phase separation can take place under thermodynamic non-equilibrium conditions, but a substantial solidification of the polymer can take place so quickly that essentially no nucleation with subsequent growth will occur. In such a case, a series of small liquid droplets will not form, and the microporous polymer obtained will not have the distinctive cell structure.

Thus, under certain circumstances, it is possible to obtain different microporous structures by using unusually high cooling rates. When e.g. a solution of 75 parts of N,N-bis(2-hydroxyethyl)-tallowamine and 25 parts of polypropylene is cooled at a rate varying from approx. 5° C to approx. 1350° C per minute, the cellular microstructure is obtained. The main effect of different cooling rates within the above range for the mixture is that the absolute cell size will change. If cooling rates of approx. 2000° C per minute is achieved, the micro-structures will e.g. a fine lacy pattern-like, non-cellular appearance. When a solution of 60 parts of N,N-bis(2-hydroxyethyl)-tallowamine and 40 parts of polypropylene is treated in the same way, a cooling rate of over 2000° C per minute is reached before the lace pattern-like, non-cellular structure is obtained.

In order to investigate the effect of the cooling system speed on the cell solidification of the cellular structure and to investigate the cooling rate necessary for a transition from the production of the cellular structure to the production of a structure without separate cells, different concentrations of polypropylene and N,N-bis(2- hydroxyethyl)-talgamine used for the preparation of homogeneous solutions. For such investigations, the previously mentioned DSC-2 was used together with standard X-ray equipment and a scanning electron microscope. As the DSC-2 is able to withstand a maximum cooling rate of approx. 80° C per minute, a heat gradient rod was also used. This was a brass rod capable of achieving a temperature difference of over 2000°C over the length of the rod of 1 meter on which the samples could be placed.

An infrared camera was used to determine the samples

temperature by first focusing the mate on a pan that was placed at the location of the ten locations on the rod that had a temperature closest to 110° C, measured with a thermocouple. The regulation device for the emission from the camera was then regulated until the read camera temperature agreed with the thermocouple reading.

In each trial, the camera was focused on a location where a given pan containing the sample solution was to be cooled. The pan with the sample was then placed on the heat gradient rod for 2 minutes. When the pan was removed from the rod to be placed in the camera field, a stopwatch was started. As soon as the camera had indicated that the pan had a temperature of 110° C, the stopwatch was stopped and the time recorded. The determined cooling rates were thus based on the time required for the sample to cool over a temperature range of approx. 100°C.

It turned out that the regulatory limitation of the cooling rate was not made up of the amount of material that was cooled. It was noted that although heavier samples cooled more slowly than light samples, the silicon oil applied to the bottom of the pan to provide heat conduction between the pan and the rod had a significant effect on the cooling rate. Thus, the highest cooling rates were obtained by placing a pan without any silicone oil on an ice cube, and the slowest cooling rates were obtained with a pan with a thick coating of silicone oil placed on a piece of paper. 5 samples of polypropylene were prepared containing from 0% N,N-bis(2-hydroxyethyl) tallamine to 80% of the amine, for use in investigating the effect of cooling rate on the structures obtained. About. 5 mg of each of the samples was heated on the DSC-2 inside closed pans at 40° C. per minute to a holding temperature of 175° C for the sample containing 20% polypropylene len, at 230° C for the sample containing 40% polypropylene, at 245° C for the sample containing 60% polypropylene, at 265° C for the sample containing 80% polypropylene, and at 250° C for the sample which consisted of 100% polypropylene.

Each of the samples was heated to and held at the approximate holding temperature for 5 minutes before being cooled. After the samples had been cooled at the desired cooling rate, the N,N-bis(2-hydroxyethyl) tallamine was extracted from the sample with methanol and the sample analyzed. The results of the investigations are reproduced in Table I, which indicates the sizes of the cells in ym for the materials obtained. All cell sizes were determined by measurements based on the respective scanning electron micrographs.

A further investigation of the cooling rate was carried out using samples of 20% polypropylene and 80% N,N-bis(2-hydroxyethyl)-tallow on the heat gradient rod. Five of these samples were cooled at different rates from a melting temperature of 210° C, and the results are reproduced in table II with an indication of the cell sizes in ym, as the same method was used to obtain the data as in table I.

It appears from tables I and II that when the cooling rate increases, the cell size in the obtained materials will generally decrease. As regards the polymer/liquid system, which is made up of 20% polypropylene and 80% N,N-bis(2-hydroxyethyl)-tallow, it also appears at a cooling rate of between approx. 1350° C per minute and 1,700° C per minute, a transformation of the obtained polymer from essentially cell-containing to non-cellular is completed. Such a transformation of the obtained structure is consistent with the characteristic that the polymer becomes substantially solid after liquid/liquid phase separation has been initiated, but before a large number of small liquid droplets are formed, as discussed above.

A further 5 samples of 40% polypropylene and 60% N,N-bis(2-hydroxyethyl)-talgamine were prepared and cooled at a rate from 690°C per minute to over 7000° C per minute from melting temperatures of 235° C., in accordance with the above-mentioned method. It was determined that for such a concentration of polypropylene and the amine, the transformation from cellular to non-cellular took place at a cooling rate of approx. 2000° C per minute.

Finally, to investigate the crystallinity of structures prepared within a range of cooling rates, 3 samples of 20% polypropylene and 80% N,N-bis(2-hydroxyethyl) tallamine were prepared and cooled at rates of 20°C, 1900°C and 6500 ° C per minute. From the DSC-2 data for such samples, it was determined that the degree of crystallinity in the 3 samples was essentially the same. It thus appears that variations in the cooling rate have no significant influence on the degree of crystallinity of the structures obtained. However, it was determined that when the cooling rate was greatly increased, as expected, the produced crystals were less perfect.

Removal of the liquid

After the homogeneous solution of polymer and liquid has been formed and after the solution has been cooled in a suitable manner to produce a material with a suitable firmness for handling, the microporous product can be formed by removing the liquid by e.g. extraction with any suitable solvent for the liquid which is similarly of course a non-solvent for the polymer in the system. The relative miscibility or solubility of the liquid in the solvent used will partly determine the efficiency expressed by the necessary time for extraction. If desired, the extraction or leaching can also be carried out at an elevated temperature below the polymer's softening point, thereby shortening the required time. Typical examples of usable solvents are isopropanol, methyl ethyl ketone, tetrahydrofuran, ethanol and heptane.

The time required will vary depending on the liquid used, the temperature used and the degree of extraction required. More precisely, in some cases it may be unnecessary to extract 100% of the liquid used in the system, and smaller amounts can be tolerated, as the amount that can be tolerated depends on the requirements for the calculated end use of the polymer. The necessary time can therefore vary within the range from several minutes or perhaps less to more than 24 hours or even more, depending on a number of variables that include the thickness of the sample.

The liquid can also be removed using other known methods. Typical examples of other applicable methods for removing the liquid include evaporation, sublimation and displacement.

It should also be noted that when common liquid extraction methods are used, the cell-containing, microporous polymer structures according to the invention can exhibit release of a liquid contained in the structure, in a way that approaches zero order, i.e. that the rate of release can be essentially constant after perhaps an original period with a high release rate. In other words, the release rate can be independent of the liquid that has been released. The speed with which the liquid is extracted after e.g. 3/4 of the liquid has been removed from the structure, so it is approximately the same as when the structure was half filled with liquid. An example of such a system which provides an essentially constant release rate is the extraction of N,N-bis(2-hydroxyethyl)-tallowamine from polypropylene with isopropanol as extractant. In addition, an initial induction period will presumably occur in any situation before the release rate can be identified. When liberation of a liquid takes place by evaporation, the rate of liberation tends to be first order.

Characterization of the microporous polymers

Cell structure

When the cooling of the polymer/liquid solution takes place so that a large number of small liquid droplets are formed as discussed above and the liquid is removed from these, the resulting microporous product forms a relatively homogeneous cell structure which, on a microscale, comprises a number of essentially spherical, enclosed microcells which are in the essentials evenly distributed throughout the structure. Neighboring cells are connected to each other via smaller pores or channels. This basic structure can be seen from the photomicrograph in fig. 4 and 5. It will be understood that the individual cells are in reality enclosed, but that they appear to be open in the photomicrographs due to the cleaning that takes place during the preparation of the sample to take the photomicrographs. On a macroscale, the structure, at least for the crystalline polymers, appears to have planes similar to the fracture plane along the edges of crystals that have grown (see fig. 2), and it is evident from fig. 3 that the appearance of the structure is coral-like. The cell microstructure can also be said to be analogous to zeolite clay structures that contain distinct "chambers" and "portal" regions. The cells correspond to the larger chamber areas in zeolite structures, but the pores correspond to the portal areas.

In the cell structure, the average diameter of the cells will usually vary from 0.5 um to 100 um, with 0.5 to 50 um being more typical, while the average diameter of the pores or interconnecting channels typically appears to be an order of magnitude smaller. If the cell diameter in a microporous polymer structure according to the invention is e.g. about. 1 ym, the average diameter of the pore or interconnecting channel will be approx. 0.1 <y>m. As pointed out above, the cell diameter and also the pore or channel diameter will depend on the particular polymer/liquid system used, the cooling rate and the relative amounts of polymer and liquid used. A wide o?sr range for the cell:pore ratios is, however, possible, such as e.g. from 2:1 to 200:1, and typically from 5:1 to 40:1.

It appears from the many figures that some of the microporous cell polymer products used as examples can be considered to the extent that they do not have the distinctive microcell structure that has been described in the present description. However, it must be understood that this structure can in some cases be masked by further modifications due to the particular liquid or polymer or the relative amounts thereof. This masking can be complete or partial and varies from small polymer particles attached to the cell walls, to large "foliage-like" polymer accumulations which in the photomicrographs tend to completely mask the underlying structure. Small polymer spheres thus adhere

e.g. and as can be seen from fig. 21 and 25, to the cell cavities of the structures. The further formation can be understood by reference to

the nucleation and growth theory described above. In systems with a particularly high content of solvent or liquid, the maximum cavity will thus typically be relatively large. This also means that the time required for the cavity or the droplet to reach its maximum size will similarly increase.

During this time, it is possible for additional germs to form nearby. Two or more germs may then come into contact with each other before each germ has reached its maximum size. In such cases, the cell structure obtained has less coherence and a somewhat lower regularity than the basic structure described above. Moreover, even after the small liquid droplets have reached their maximum size, depending on the system used, the solvent or liquid phase may still contain some residual polymer or vice versa. In such situations, further residual phase separation may occur as the system continues to cool. When the residual polymer is simply separated from the solution, polymer spheres can be formed, as shown in fig. 21 and 25. On the other hand, if the residual polymer diffuses to the polymer skin, the walls will appear hairy and irregular, thus giving the "foliage type" structure. This "foliage type" structure can only partially mask the basic structure, as shown in fig. 28 and 29, or it may completely mask the structure, as shown in Figs. 6.

The "leaflet type" structure is also more likely to occur for certain polymers. The microporous polyethylene structures with low specific gravity thus typically provide this type of structure, possibly due to the solubility or the like of the polyethylene in the particular liquids used. This can be observed in fig. 14. Furthermore, when the amounts of the liquid used are particularly large, this will also occur for polymers, such as polypropylene, which otherwise exhibit the basic structure. This can be easily observed by comparing the "leafwork type" structure of the microporous product according to fig. 6 with the basic structure according to fig. 8, where the polymer content is 40% by weight compared to the 10% by weight polypropylene in the structure shown in fig. 6.

For most applications, it is preferred to use a system that causes the cell matrix to form. The relative homogeneity and regularity of this structure provides predictable results, which are necessary for filtration applications. However, the sheet-work type structure may be more desirable if structures with a relatively high surface area are desired, such as for ion exchange or various adsorption processes.

It can also be observed that some of the structures have small holes or openings in the cell walls. This phenomenon can also be understood by reference to the nucleation and growth theory. Thus, in a section of the system where a few spatially associated liquid droplets have already reached their maximum size, each drop will be enclosed by a polymer-rich skin. In some cases, however, some solvent may be trapped between the enclosed droplets, but it cannot continue to migrate to the larger droplets due to the skin's lack of permeability. In such cases, therefore, a seed of the liquid can form and grow and lead to a small cavity that is submerged near the larger droplets. After the liquid has been extracted, the smaller droplets will appear as a small hole or opening. This can be observed for the micro-porous structures shown in fig. 11 - 12 and 20.

Another interesting characteristic of the cell structure according to the invention is linked to the surface area of these structures.

The theoretical surface area for the microporous cell structure, which consists of interconnected spherical cavities with a diameter of approx. 5 um, is 2 - 4 m 2/g. It has been shown that microporous polymers produced by the present method need not be limited to the theoretical limit of the surface area. Determination of surface area using the B.E.T. method described by Brunauer, S., Emmett, P.H. and Teller, E. in "The Adsorption of Gases in Multimolecular Layers" J.Am.Chem. Soc., 60, 309,-16 (1938), have shown surface areas far greater than for the theoretical model which is not in proportion to the cavity, as shown in Table III, for microporous polymers made from polypropylene and N,N- bis(2-hydroxyethyl)-tallowamine.

The surface area can be reduced by careful annealing of the microporous polymer without affecting the basic structure. Microporous polypropylene prepared with 75% voids using N,N-bis(2-hydroxyethyl)-tallowamine as the liquid component was extracted and dried at temperatures not higher than room temperature and then heated to affect the surface area. The original surface area was 96.9 m 2 /g. After eleven 40 minute heating periods at 62° C, the surface area decreased to 66 m /g. A further heating at 60° C. for a further 66 hours reduced the surface area to 51.4 m 2 /g. Treatment of another sample at 90° C. for 52 hours decreased the surface area from 96.9 to 33.7 m 2 /g. The microporous structures were not significantly altered when examined by scanning electron microscopy. These results are summarized in table IV.

It should be clear that one of the distinctive features of the cell structures according to the invention concerns the presence of both separate, essentially spherical, enclosed microcells that are evenly distributed throughout the structure, and clear pores that connect cells to each other, the pores having a smaller diameter than the cells. Moreover, the cells and the interconnecting pores have essentially no spatial orientation and can be described as isotropic. There is thus no preferred direction such as e.g. for the flow of a liquid through the structure. This is in stark contrast to known materials that do not have such a cell structure. A number of known systems have an indistinct structure that lacks any structural design that can be defined. It is therefore very surprising that a microporous structure can be produced with such uniformity which may be particularly desirable for a number of applications where highly uniform materials are required.

The cell structure can be defined in terms of the ratio between the average diameter of the cells ("C") and the diameter of the pores ("P"). The C/P ratio as mentioned above can thus vary from 2 to 200, with 5 to 100 being typical and 5 to 40 even more typical. Such a C/P ratio separates the cell structure according to the invention from any known microporous, polymeric product. As there is no synthetic thermoplastic polymer structure known within the state of the art with separate cells and pores, must. all such known materials are assumed to have a cell-to-pore ratio of 1.

Another way of describing the cell structures according to the invention is by a sharpness factor "S". The S-factor is determined by analyzing a mercury displacement curve for a given structure. All mercury displacement data discussed in this specification were determined using a "Micromeritics" mercury intrusion porosity meter from the model 910 series. The S value is defined as the ratio of the pressure at. at which 85% of the mercury penetrated, and the pressure at which 15% of the mercury penetrated. This ratio is a direct indication of the variation in pore diameter over the central 70% of the pores for any sample as the pore diameter is equal to 12.43 divided by the pressure in kg/cm

The S value is then a ratio between the diameter of the pores through which 15% of the mercury has penetrated, and the diameter of the pores through which 85% of the mercury has penetrated. The range of 1 - 15% and 85 - 100% for mercury penetration is not taken into account when determining the S-factor. The range from 0 - 15% is not taken into account as penetration within this range can be due to cracks that have been introduced into the material as a result of the freeze degradation to which the material was exposed before the mercury penetration test was carried out. Furthermore, the range from 85 to 100% is not taken into account as data within such a range may be due to compression of the sample or a real penetration of mercury into the pores.

It is characteristic of the narrow range of pore sizes that the bodies according to the invention have that the S-value for such structures is 1-30, with 2-20 being typical and 2-10 even more typical.

The average size of the cells in the structure varies from 0.5 to 100 µm, with 1 - 30 µm being typical and 1 - 20 µm even more typical. As indicated, the cell size may vary depending on the particular resin and compatible liquid used, the ratio of polymer to liquid and the cooling rate used to form the particular microporous polymer. The same variable will also affect the average size of the pores in the obtained structure, which usually varies from 0.05 to 10 ym, with 0.1 - 5 ym being typical and 0.1 - 1.0 ym even more typical. All references to a cell and/or pore size in this description refer to the average diameter for such a cell or pore expressed in ym unless otherwise stated.

By determining the above-mentioned factors, i.e. cell diameter, pore diameter and S, for the microporous cell polymers according to the invention, the microporous cell polymers according to the invention can be precisely defined. A particularly useful means of defining the polymer in this way is by the logarithm of the cell/pore ratio ("log C/P") and by the logarithm of the ratio of the sharpness function S to the cell size ("log S/C"). The micro-porous cell polymers according to the invention therefore have a log C/P of 0.2 - 2.4 and a log S/C of -1.4 - 1.0, and the polymers more commonly have a log C/P of 0 .6 - 2.2 and a log S/C of -0.6 - 0.4.

Cell-free structure

The cell-free structure which, according to the invention, is obtained by cooling the homogeneous solution at such a rate that the polymer essentially solidifies before the large number of liquid droplets is formed, can be described mainly in connection with the narrow pore size distribution for the material together with the actual pore size and the structure's spatial uniformity.

The cell-free microporous polymers can in particular be described using a sharpness function S as mentioned above in connection with the cell structure. The S-values that the cell-free structure has vary from 1 to 30, 1-10 being preferred and 6-9 even more preferred. However, when the material's pore size varies from 0.2 to 5 ym, the S value will vary from 5-10, typically 5-10. Such S-values for olefinic polymers and oxy-das ion polymers with a microporosity of such a size have hitherto been unknown, with the exception of highly oriented thin films produced by a stretching method. As indicated above, the porous polymers according to the invention are essentially isotropic. A cross-section of the polymers taken along any spatial plane will thus show essentially the same structural features.

The pore sizes for the cell-free structures according to the invention are usually 0.05 - 5 ym, typically 0.1 - 5 ym and even more typically 0.2 - 1.0 ym.

It appears that a surprising feature of the present invention is the possibility of using it to produce isotropic, microporous bodies of olefinic polymers and oxidation polymers, the bodies having a porosity of 0.2 - 5 ym and a sharpness value of 1 - 10. It is particularly surprising that such bodies can be produced not only in the form of thin films, but also in the form of blocks and intricately shaped objects.

General remarks

When a film or block is formed by casting on a substrate such as e.g. a metal plate, the surface of the microporous polymer structure according to the invention and which is in contact with the plate, will comprise a cell-free surface skin. In contrast, its other surface is usually mainly open. The thickness of the skin will vary in accordance with the particular system used and with the particular process parameters used. However, the thickness of the skin will usually be approximately equal to the thickness of a single cell wall. Depending on the particular conditions used, the skin can vary from a skin that is completely impermeable to the flow of liquids, to a skin that has a certain degree of liquid porosity.

If only a cellular structure is desired for the intended end use, the surface skin can be removed by any of a number of methods. As typical examples, it can be noted that the skin can be removed by using any of a number of mechanical means, such as abrading, puncturing the skin with needles, or breaking down the skin by passing the film or other structure through rollers. at different speeds. The skin will also be able to be removed by microtoming. The skin can also be removed with chemical means, i.e. short-term contact with a suitable solvent for the polymer.

When e.g. a solution of polypropylene in N,N-bis(2-hydroxyethyl) tallow amine is continuously extruded as a thin film on an endless stainless steel conveyor belt, applying a small amount of liquid solvent to the belt immediately before the solution application zone will effectively remove it surface that forms at the interface between solution and steel. Useful liquids are such liquids as isoparaffinic hydrocarbons, decane, decalin, xylene and mixtures thereof, such as xylene-isopropanol and decalin-isopropanol.

For some end uses, however, the presence of the skin will not only not be undesirable, but a necessary component. As an example, it can be mentioned that, as is known, a thin film which is impermeable to liquid is used in ultrafiltration or in other applications of the membrane type. For such applications, the microporous part of the structure according to the invention would therefore be particularly useful as a substrate for the surface skin which will act as a membrane for such applications. A complete cell structure can also be produced directly using different methods. The polymer liquid system would thus e.g. could be extruded in air or a liquid medium, such as e.g. hexane.

The microporous polymer structures according to the invention have, as mentioned above, cell and pore diameters with very narrow size distributions which indicate the distinctive structures and their relative homogeneity. The narrow size distribution of the pore diameters is evident from the mercury penetration data, as shown in fig. 30 - 33. The same general distribution is obtained regardless of whether the structure is in the form of a film (fig. 30 - 32) or a block (fig. 33). The characteristic pore size distribution. for the micro-porous structure according to the invention is in strong contrast to the significant further pore size distributions for known micro-porous polymer products produced using known methods, such as e.g. described in US patent documents No. 3,310,505 and No. 3,378,507, and this will be discussed in more detail in connection with the examples.

For any of the microporous polymers produced according to the invention, the particular intended end use will as a rule determine the amount of voids and the requirements for the pore size. For e.g. prefilter applications, the pore size will typically be above 0.5 pm, while the pore size in ultrafiltration should be below approx. 0.1 ym.

For applications where the microporous structure actually serves as a recipient for a functionally useful liquid, strength trade-offs will dictate the amount of voids if the contained functional liquid is to be released in a controlled manner. In such cases, the pore size will similarly be dictated by the desired release rate, smaller pore sizes tending to give lower release rates.

If the microporous structure is to be used to convert a liquid polymer additive, such as a flame retardant, into a solid material, a certain minimum strength is usually desired, but in accordance with this minimum strength it will usually be desired to use as much liquid as possible as the polymer only serves as a receiver or carrier material.

Microporous polymers containing functional liquids

It will be understood from the above description that according to a feature of the present invention, microporous products containing a functionally useful liquid, such as a polymer additive (e.g. a flame retardant mite1), can be produced which behave like and can be processed as a solid material . For this purpose, the obtained microporous polymer must again be filled with the desired functional liquid. This can be achieved by using normal absorption methods, and the amount of liquid taken up will be essentially the same as the amount of liquid used to first produce the microporous polymer. Any useful organic liquid can be used as long as the liquid is not, of course, a solvent for the polymer or otherwise will attack or degrade the polymer at the working temperature. The microporous products containing the functional useful liquid can be produced from or by using microporous polymers with cellular structure or cell-free structure as the base material in which the liquid is incorporated.

Such microporous products can be similarly produced using a displacement method. According to this" embodiment of the invention, the microporous polymer intermediate is first prepared, and the liquid is then displaced either with the desired functional useful liquid or with a transient displacement liquid. In each case, the displacement is carried out by normal pressure or by vacuum displacement or by infusion methods instead of extracting the liquid that was used for the production of the microporous polymer intermediate.

Any functional or temporary displacement liquid can be used which could have been used as extraction liquid for the production of the microporous polymer, i.e. the liquid which is not a solvent for the polymer, but which nevertheless has a certain solubility in or miscibility with the liquid which is displaced. It will be understood that smaller quantities of the displaced liquid or the displaced liquids may remain after the displacement. The requirement for the end use will typically dictate the desired degree of displacement. Thus amounts of 1 - 10% by weight can be tolerated for some applications. If necessary, several displacements and/or the use of liquids that can be easily removed by evaporation can enable the removal of essentially the entire amount of the liquid or liquids to be displaced, i.e. that under approx. 0.03 wt% residual liquid can be achieved. From an economic point of view, it will generally be desirable to use a displacement liquid which has a boiling point which is sufficiently different from the boiling point of the liquid to be displaced, thereby enabling recovery and renewed use. For this reason, it may be desirable to use a transient displacement fluid.

It will also be apparent from the above examples of applicable polymer-liquid systems that a further method of making a material of polymer and functionally applicable liquid includes utilization of the microporous polymer intermediate without further treatment, as a number of functionally applicable liquids have been shown to be able to be used as the compatible liquid together with special polymers to produce the solid microporous polymeric intermediate. Intermediates that behave as solid materials can thus be produced directly with liquids that are useful as lubricants, surfactants, abrasives, moth repellents, pesticides, plasticizers, medicines, fuel additives, polishing agents, stabilizers, insect repellents and animal repellents, odorants, flame retardants, antioxidants, odor masking agents, anti-fog agents, perfumes and similar agents. When using e.g. LD-polyethylene useful intermediates containing a lubricant or plasticizer can be prepared by using an aliphatic or aromatic ester with 8 carbon atoms or more or a non-aromatic hydrocarbon with 9 carbon atoms or more. Useful products containing a surfactant and/or wetting agent can be prepared from LD polyethylene using a polyethoxylated aliphatic amine of 8 or more carbon atoms or using a nonionic surfactant. When using polypropylene, intermediate products containing a surfactant can be prepared by using diethoxylated aliphatic amines with 1 or more carbon atoms. Polypropylene intermediates containing abrasives can be prepared by using a phenylmethylpolysiloxane, but abrasive intermediates with LD polyethylene are formed by using an aliphatic amide with 12 - 22 carbon atoms. Fuel addition intermediates with LD polyethylene can be prepared using an aliphatic amine of 1 or more carbon atoms or an aliphatic dimethyl-tert-amine of 12 or more carbon atoms. The tertiary amines can also form useful addition intermediates with methylpentene polymers. HD and LD polyethylene intermediates containing a stabilizer can be formed using an alkylaryl phosphite.

Intermediate products of LD polyethylene containing an anti-fog agent can be prepared by using the glycerol mono- or diester of a layered fatty acid with at least 10 carbon atoms. Intermediate products with incorporated flame retardants can be produced with HD and LD polyethylene, polypropylene and a mixture of polyphenylene oxide and polystyrene using a polyhalogenated aromatic hydrocarbon with at least 4 halogen atoms per molecule. Usable materials should of course be liquid at the phase separation temperature described here. Other systems that have proven to be applicable will be described in more detail in connection with the examples below.

Moreover, the association with polypropylene, HD-polyethylene and LD-polyethylene certain groups of ketones have been shown to be particularly

usable as animal repellents and can generally be used in the implementation of the present invention. Such ketones may include saturated aliphatic ketones with 7-19 carbon atoms, unsaturated aliphatic ketones with 7-13 carbon atoms, 4-tert.amylcyclohexanone and 4-tert.butylcyclohexanone.

In the examples below, all parts and percentages are based on weight unless otherwise stated.

Manufacturing method

The porous polymer intermediates and the microporous polymers described in the examples below were prepared using the following method:

A. Porous polymer intermediates

The porous polymer intermediates are prepared by mixing a polymer and a compatible liquid, heating the mixture to a temperature usually near or above the softening point of the resin so that the homogeneous solution is formed, and then cooling the solution without subjecting it to mixing or other shearing forces to produce a macroscopically solid, homogeneous mass. When massive blocks of the intermediate product are to be produced, the homogeneous solution is given a desired shape by pouring it into a suitable container which is usually made of metal or glass, and the solution is cooled under room conditions unless otherwise specified. The cooling rate under room temperature conditions will vary depending on such factors as the thickness and composition of the sample, but it will usually be 10 - 20° C per minute. The container is usually cylindrical with a diameter of 1.9 - 6.4 cm, and the solution is typically poured to a depth of 0.63 - 5.10 cm. When films of the intermediate are formed, the homogeneous solution is poured onto a metal plate which is heated to a sufficient temperature for the solution to be drawn out into a thin film. The metal plate is then placed in contact with a dry-ice bath to rapidly cool the film below its solidification temperature.

B. Porous polymer

The microporous polymer is produced by extracting the compatible liquid that was used to produce the porous polymer intermediate, usually by repeatedly washing the intermediate in a solvent, such as isopropanol or methyl ethyl ketone, after which the solid, microporous mass is dried.

Examples

In the examples and tables below, some of the different combinations of polymer/compatible liquid are described which can be used for the production of the porous intermediate polymer products, f and various known or in-hand

len available microporous products. Solid blocks of the intermediates were prepared with all the combinations indicated in the examples, and when tabulated, thin films of the intermediate were also prepared, using the method described above. As indicated in the tables below

several of the intermediate products were used for the production of the microporous polymers according to the invention by using a suitable solvent to extract the compatible liquid from the intermediate product, to then remove the solvent, e.g. by evaporation.

A number of the compatible liquids described in the examples below are, as indicated in the tables, functional liquids which are useful not only as compatible liquids, but also as flame retardants, release agents and similar aids. The intermediate products produced with such functional liquids are thus useful as solid additives for polymers and similar auxiliaries, and also as intermediate products for the production of porous polymers. The functional fluids described in the examples below are indicated as functional by means of one or more of the following symbols under the column "Type of functional fluid": AD (anti-fog agent), AO (anti-oxidation agent), DF (animal repellent) , BT (fuel additive), DM (perfumer), FH (flame retardant), IF (insect repellent), S (lubricant), M (medicinal agent), MF (moth repellent), LM (air masking agent ), P (plasticizer), PM (polishing agent), PE (pesticide), PF (perfume), S (fungicide), OM (surfactant), and ST (stabilizer).

Examples 1-27

In examples 1 - 27 in table V, the production of homogeneous, porous polymer intermediates in the form of cylindrical blocks with a radius of approx. 3.2 cm and a depth of approx. 5.1 cm, from HD polyethylene ("HDPE") and the compatible liquids found to be applicable, using the standard method of manufacture. The HD polyethylene that was used is sold under the trademark "Plaskon AA 55-003" and has a melt index of 0.3 g/10 minutes and a specific gravity of 0.954 g/cm 3. A number of the intermediate products indicated in the examples were extracted for the production of porous polymers, as indicated in the table.

The details of the preparation and of the type of the indicated functionally useful liquids are given in table V.

In examples 28-188" in table VI, for the same purpose as in examples 1-27, LD-polyethylene with the following properties was used, specific gravity 0.922 g/cm, melt index 21 g/10 min.

Photomicrographs of the porous polymers according to the examples

38 and 122 are shown on respectively. fig. 28 and 29. The photomicrographs taken at a magnification of 2000X show the cell structure with a significant proportion of "foliage" evenly distributed throughout the samples.

Examples 189-193

Examples 190-194 in Table VII show the formation of homogeneous porous polymer intermediates by pouring the solution into a glass dish to form cylindrical blocks with a radius of 4.45 cm and a depth of 6.35 mm, if nothing else is indicated, from "Noryl" polymer and the compatible liquids found to be applicable, using the standard method of manufacture. In the indicated cases, the microporous polymer was likewise produced.

Details regarding the preparation and type of functional fluid are given in Table VII.

A photomicrograph of the microporous polymer according to example

192 is shown in fig. 25. The photomicrograph taken at a magnification of 2500X shows the microcell structure with globular resin deposits on the cell walls.

Examples 194-236

Examples 194-236 in Table VIII demonstrate the formation of homogeneous porous polymer intermediates in the form of cylindrical blocks with a radius of 3.18 cm and a depth of 1.27 cm from polypropylene ("PP") and the compatible liquids shown to be applicable, using the standard manufacturing method. Furthermore, in the given examples, blocks with a thickness of 15.2 cm and/ thin films were produced. As indicated, the microporous polymer was also prepared.

Details regarding the preparation and type of functional fluid are given in Table VIII.

Photomicrographs of the porous polymer according to Example 225 are shown in fig. 2-5. The photomicrographs according to fig. 2 and 3 which were taken with a magnification of respectively 55X and 550X, shows the macrostructure of microporous polymer. The photomicrographs according to fig. 4 and 5 which were taken with a magnification of 2200X and 5500X, shows the microcellular structure of the polymer and also the interconnecting pores.

Examples 237-243

Examples 237-243. in Table IX shows the formation of homogeneous porous polymer intermediates in the form of cylindrical blocks with a radius of 3.18 cm and a thickness of 1.27 cm from polyvinyl chloride ("PVC") and the compatible liquids which were found to be useful, under application of the standard manufacturing method. A number of the exemplified intermediates were extracted to produce porous polymers, as indicated in the table.

Details regarding the preparation and type of functional fluid are given in Table IX.

A photomicrograph of the porous polymer according to example 24 2 is shown in fig. 27. The photomicrograph taken at a magnification of 2000X shows the very small cell size of this microporous polymer in contrast to the cell structure exemplified in fig. 7,13,18,20 and 24 where the cell size is larger and easier to observe at a comparable magnification. The photomicrograph also shows the presence of a large amount of resin masking the basic cell structure.

Examples 244-255

Examples 244-255 in Table X demonstrate the formation of homogeneous porous polymer intermediates in the form of cylindrical blocks having a radius of 3.18 cm and a thickness of 5.08 cm from methylpentene ("MPP") polymer and the compatible liquids which showed to be applicable, using the standard manufacturing method. A number of the exemplified intermediates were extracted to form porous polymers, as indicated in the table.

Details regarding the preparation and type of functional fluid are given in Table X.

A photomicrograph of the porous polymer according to Example 253 is shown in fig. 22. The photomicrograph which was taken with a magnification of 2400X shows the strongly flattened cell walls compared to the design that can be observed in fig. 14.

Examples 265-266

Examples 256-266 in Table XI show the formation of homogeneous porous polymer intermediates in the form of cylindrical blocks with a radius of 3.18 cm and a depth of 1.27 cm from polystyrene ("PS").

and the compatible liquids found to be useful, using the standard method of manufacture. All of the exemplified intermediates were extracted to form porous polymers.

Details regarding the preparation and type of the functionally usable liquid are given in Table XI.

A photomicrograph of the microporous polymer according to

example 260 is shown in fig. 26. Although the cells are small compared to the cells shown in fig. 4, 7, 13, 18 and 25, the basic microcell structure is present.

Example 267

This example describes the formation of a homogeneous, porous polymer intermediate from 30% high-impact polystyrene ("Bakelite<11> polystyrene for injection molding with the following properties: Tensile phase (3.18 mm thick) 356 kg/cm<2>, final elongation (3.18 mm thick) 25, Tensile modulus (3.18 mm thick) 26717 kg/cm<2>, Rockwell hardness (0.64 x 1.27 x 12.7 cm) 90, Specific gravity, natural 1.04 ) and 70% hexabromobiphenyl using the standard preparation method and by heating the mixture to 280°C.

The polymer intermediate thus formed had a diameter of

about. 6.4 cm and a thickness of approx. 1.3 cm. The hexabromobiphenyl is useful as a flame retardant, and the porous intermediate is useful as a solid flame retardant additive.

Example 268

This example describes the formation of a homogeneous, porous polymer intermediate from 25% acrylonitrile/butadiene/styrene terpolymer ("Kralastic ABS" polymer with the following properties: Specific gravity 1.07, Izod shear strength (3.18 mm test rod) at

22.8°C 7.0-10.3 cm-kg/cm, tensile strength 619 kg/cm<2> and Rockwell hardness 118) and 7 5% diphenylamine using the standard preparation method and heating the mixture to 220° C. The polymer intermediate thus formed had a diameter of approx. 6.4 cm and a thickness of approx. 5.1 cm. The microporous polymer was formed by extracting the diphenylamine. diphenyl-

the amine is useful as a pesticide and antioxidant, and the porous polymer intermediate has the same application.

EB samples 269 and 270

The homogeneous, porous polymer intermediates were prepared from 25% chlorinated polyethylene thermoplastic but a melt viscosity of 15 poise, 8% crystallinity and containing 36% chlorine and 75%

N,N-bis (2-hydroxyethyl) tallow amine (Example 270) and 75% chlorinated polyethylene thermoplastic and 25% 1-dodecanol (Example 271) using the standard preparation method and heating to 220°C. The porous polymer intermediates had a diameter of approx. 6.4 cm and a thickness of approx. 5.1 cm.

Example 271

The homogeneous, porous polymer intermediate was prepared using the standard preparation method and by heating to 210°C from 25% chlorinated polyethylene elastomer as used in Example 271 and 75% diphenyl ether. The porous polymer intermediates had a diameter of approx. 6.4 cm and a thickness of approx. 5.1 cm. The diphenyl ether is useful as a perfume, and the intermediate is also useful in perfumes.

Examples 272-275

In examples 272-275 which are reproduced in table XII, the production of homogeneous, porous polymer intermediates in the form of cylindrical blocks with a radius of approx. 3.2 cm and a thickness of approx. 1.3 cm from styrene/butadiene ("SBR") rubber ("Kraton SBR" polymer with the following properties: Tensile strength 217-323 kg/cm <2>, elongation at break 880-1300 and Rockwell hardness, Shore A, 35-70) and the compatible liquids found to be useful using the standard method of preparation. In addition to the indicated cylindrical blocks, thin films were also produced.

Details regarding the preparation and the indicated type of functionally usable liquid are reproduced in Table XII..

Examples 276-278

Examples 277-279, which are reproduced in Table XIII, describe the production of homogeneous, porous polymer intermediates in the form of cylindrical blocks with a radius of 3.18 cm and a thick

love of approx. 1.3 cm from the resin sold under the trademark "Surlyn" ionomer resin 1652, production number 115478, with the following properties: Specific gravity 0.939 g/cm., melt flow index 0.44 g/min, tensile strength 200 kg/cm 2 , conventional yield strength 131 kg /cm 2 and elongation 580%, and the compatible . liquids found to be usable, using the standard method of manufacture. In addition to the indicated cylindrical blocks, thin films were also produced. Two of the intermediates described in the examples were extracted to form porous polymers, as indicated in

the table.

Details regarding the preparation and indicated type of functionally usable fluids are given in Table XIII.

Photomicrographs of the porous polymer according to example

277 is shown in fig. 23 and 24. Fig. 23, which was taken at a magnification of 255X, shows the macrostructure of the polymer. Fig. 24, which was taken with a magnification of 2550X, shows the polymer's microcell structure with a faint hint of "leafwork" and relatively thick cell walls compared to e.g. with the polymer shown in fig. 25.

Example 279

A homogeneous, porous <p>olymer intermediate product was produced using the standard production method and by heating to 200°C from equal parts of a mixture of HD polyethylene/chlorinated polyethylene and 75% 1-dodecanol. The porous polymer intermediate was cast into a film with a thickness of 0.508-0.635 mm. The HD polyethylene and the chlorinated polyethylene (CPE) were used in previous examples.

Example 280

A homogeneous, porous polymer intermediate was prepared using the standard production method and by heating to 200°C from a mixture of equal parts HD polyethylene/polyvinyl chloride and 75% 1-dodecanol. The thus produced intermediate product had a thickness of approx. 5.1 cm and a diameter of approx. 6.4 cm. The HD polyethylene and polyvinyl chloride (PVC) were the same as those used in previous examples.

Example 281

A homogeneous, porous polymer intermediate was prepared using the standard manufacturing method and by heating to 200°C from a mixture of equal parts HD polyethylene and an acrylonitrile/butadiene/styrene terpolymer and 75% 1-dodecanol. The thus produced intermediate product had a thickness of approx. 5.1 cm and a diameter of approx. 6.4 cm. The HD polyethylene and the acrylonitrile/butadiene/styrene terpolymer (ABS) were the same as those used in previous examples.

Examples 282-285

In the examples 282-285 that are reproduced in Table XIV, the production of homogeneous, porous polymer intermediates is described,

in the form of cylindrical blocks with a radius of 3.18 cm and a thick

emperor of ca. 5.1 cm from a mixture of equal parts of LD polyethylene and chlorinated polyethylene and from the compatible liquids found to be useful, using the standard method of manufacture. For Example 283, the above method was used, but the intermediate was cast into a film with a thickness of 0.508-0.635 mm. The LD polyethylene and the chlorinated polyethylene (CPE) were the same as those used in previous examples.

Details regarding the preparation and the indicated type of functional fluid are given in Table XIV:

Examples 286 and 287

Homogeneous, porous polymer intermediates were produced using the standard production method and by heating to 220°C for example 286 and to 270°C for example 288 from a mix-

ing of equal parts LD-polyethylene and polypropylene and 75% N,N-bis

(2-hydroxyethyl)-talgamine (Example 286) and from a mixture of

equal parts of LD polyethylene and polypropylene and 50% N,N-bis(2-hydroxyethyl)-tallow (Example 287). Both porous polymer intermediates had a diameter of approx. 6.4 cm and a thickness of approx. 5.1 cm. The LD polyethylene and polypropylene (PP) were the same as used in previous examples.

Example 288

A homogeneous, porous polymer intermediate was prepared using the standard production method and by heating to 200°C from 50% N,N-bis(2-hydroxyethyl)-tallowamine and 50%

of a mixture of polypropylene and polystyrene (25 parts polypropylene). The porous polymer intermediates had a diameter of approx. 6.4 cm

and a thickness of approx. 5.1 cm. The polypropylene (PP) and polystyrene (PS) were the same as those used in previous examples.

Example 289

A homogeneous, porous intermediate polymer product was produced using the standard production method and by heating to 200°C from 75% 1-dodecanol and a mixture of equal parts of polypropylene and chlorinated polyethylene. The porous polymer intermediate had a diameter of approx. 6.4 cm and a thickness of approx. 1.3 cm. The polypropylene and the chlorinated polyethylene (CPE) were the same as those used in previous examples.

Examples 290-300

Examples 290-300 describe the applicable concentration range for polymer-compatible liquid for the production of a homogeneous, porous polymer intermediate from HD-polyethylene and N,N-bis(2-hydroxyethyl)-tallow. In each example, the intermediates had a thickness of approx. 5.1 cm and a diameter of approx. 6.4 cm.

The HD polyethylene used was the same as has been used in previous examples.

Details regarding the preparation and some physical properties are given in Table XV.

A photomicrograph of the porous polymer according to example 300 is shown in fig. 19 with a magnification of 2000X. The cells are not clearly visible at this magnification. Fig. 19 can be compared with fig. 17 where the magnification is 2475X and where cell sizes are also very small at a similar polymer concentration of 70%.

Examples 301-311

In these examples, the applicable concentration range for polymer-compatible liquid for the production of a homogeneous, porous polymer intermediate product from LD-polyethylene and N,N-bis(2-hydroxyethyl) tallow amine is described. In each example, the intermediate product had a thickness of approx. 1.3 cm and a diameter of approx. 6.4 cm. The LD polyethylene used was the same that had been used

in previous examples.

Details regarding the manufacture and some physical properties are given in Table XVI.

Photomicrographs of the porous polymers according to examples 303, 307 and 310 are shown respectively in fig. 14-15 with a magnification of 250X and 20500X, fig. 16 with a magnification of 2500X and fig. 17 with a magnification of 2475X. These figures show the decreasing cell size from a very large cell size (Fig. 15, 20% polymer) to a very small cell size (Fig. 17, 70% polymer) with increasing polymer content. The relatively flattened cell walls for the polymer with 20% polymer content according to example 3 03 are similar to the relatively flattened cell walls for the methylpentene polymer (fig. 22) and can be seen from fig. 14. Fig. 15 is an enlargement showing part of a cell wall shown in Fig. 14. The microcell structure of the porous polymer can be seen from fig. 16.

Examples 312-316

Examples 312-316 describe the applicable concentration range for polymer-compatible liquid for the production of a homogeneous, porous polymer intermediate from LD polyethylene and diphenyl ether. In each example, the intermediate product had a thickness of approx. 1.3 cm and a diameter of approx. 6.4 cm. The LD polyethylene used was the same as has been used in previous examples.

Details regarding the manufacture and some physical properties are given in Table XVII.

Examples 317-321

Examples 317-321 describe the applicable concentration range for polymer-compatible liquids for the production of a homogeneous, porous polymer intermediate from LD-polyethylene and 1-hexadecene. In each example, the intermediate product had a thickness of approx. 5.1 cm and a diameter of approx. 6.4 cm. The LD polyethylene used was the same as the 1D polyethylene used in previous examples.

Details regarding the preparation and some physical properties are given in Table XVIII.

Examples 322-334

In these examples, the applicable concentration range for polymer liquid for the production of a homogeneous, porous polymer intermediate product from polypropylene and N,N-bis(2-hydroxy-ethyl)-tallow is described. In each example, the intermediate product had a thickness of approx. 1.3 cm and a diameter of 6.4 cm. As indicated, films were also produced. The polypropylene used was the same as the polypropylene used in previous examples.

Details regarding the preparation and some physical properties are given in Table XIX.

Photomicrographs of the intermediates according to examples 322, 326, 328, 330 and 333 are shown in, respectively. fig. 6-10, taken with a front size of respectively 1325X, 1550X, 1620X, 1450X and 1250X. The very pronounced foliage formation for the microporous polymer with 10% polymer can be seen from fig. 6, but the microcell structure is nevertheless still retained. These figures show the decreasing cell size as the amount of polymer increases. However, the microcellular structure is present in each sample despite the small cell size.

Examples 335-337

In these examples, the applicable concentration range for polymer-compatible liquid for the production of a homogeneous, porous polymer intermediate product from polypropylene and diphenyl ether is described. In each example, the intermediate product had a thickness of approx. 1.3 cm and a diameter of approx. 6.4 cm. In addition, as indicated, thin films were also produced. The polypropylene used was the same polypropylene that has been used in previous examples.

Details regarding the preparation and some physical properties are given in Table XXI.

Photomicrographs of the porous polymer according to examples 335, 336 and 337 are shown in, respectively. fig. 11 (magnification 2000X),

fig. 12 (magnification 2059X) and fig. 13 (magnification 1950X).

The figures show that as the polymer concentration increases, the cell size decreases, and fig. 11 shows the smooth cell walls, while fig. 12 and 13 show the cells and connecting pores. From. each of the figures shows that the microcell structure is present.

Examples 338-346

In these examples, the applicable concentration range for polymer-compatible liquid for the production of a homogeneous, porous polymer intermediate product from styrene/butadiene rubber and N-N-bis(2-hydroxyethyl) tallow is described. In each example, the intermediate product had a thickness of approx. 1.3 cm and a diameter of 6.35 cm. Also, as indicated, thin films were produced. The styrene/butadiene used

J

rubber (SBG) was the same as the styrene/butadiene rubber used in previous examples.

Details regarding the preparation and some physical properties are given in Table XXI.

Photomicrographs for the microporous styrene/butadiene rubber polymer according to Examples 339 and 340 are shown in Figs. fig. 20 (magnification 2550X) and fig. 21 (magnification 2575X). The figures show the microcell structure in the microporous polymers. Fig..21 also shows the presence of spherical polymer deposits on the cell walls.

.'> Examples 347^ 352

Examples 347-352 describe the applicable concentration range for polymer-compatible liquid for the production of a homogeneous polymer intermediate from styrene/butadiene rubber and decanol. In each example, the intermediate product had a thickness of approx. 1.3 cm and a diameter of 6.35 cm. Also, as indicated, thin films were produced. The styrene/butadiene rubber (SBG) used was the same as the styrene/butadiene rubber used in previous examples.

Details regarding the preparation and some physical properties are reproduced in Table XXII.

Examples 353-356

These examples relate to polymer intermediates prepared from styrene/butadiene rubber and diphenylamine, and details of the preparation are given in Table XXIII.

Examples 357-361

Examples 357-361 describe the applicable concentration range for polymer-compatible liquid for the production of a homogeneous, porous polymer intermediate from a "Surlyn" resin as used in previous examples, and N,N-bis(hydroxyethylene) tallow amine. In each example, the intermediate product had a thickness of approx. 1.3 cm and a diameter of 6.35 cm. Also, as indicated, thin films were produced.

Details regarding the preparation and some physical properties are given in Table XXIV.

Examples 362-370

In these examples, the applicable concentration range for polymer-compatible liquid is described for the production of a homogeneous, porous polymer intermediate from a "Surlyn" resin as used in the previous examples, and diphenyl ether. In each example, the intermediate product had a thickness of approx. 1.3 cm and a diameter of approx. 6.4 cm. Also, as indicated, thin films were produced.

Details regarding the manufacture and some physical properties are given in table XXV.

Examples 371-379

Examples 371-379 describe the applicable concentration range for polymer-compatible liquid for producing a homogeneous, porous polymer intermediate from a "Surlyn" resin as used in previous examples, and dibutyl phthalate. In each example, the intermediate product had a thickness of approx. 1.3 cm and a diameter of approx. 6.4 cm.

Details regarding the preparation and some physical properties are given in Table XXVI.

Examples 380-384

According to the state of the art

Examples 380-334 are examples relating to the production of various known materials which have been shown to have a physical structure that is different from the physical structure of the polymer produced according to the invention.

Example 330

A porous polymer was prepared using the process of Example 1 in US Patent No. 3,378,507, but modified to obtain a product with some physical integrity (integrity) and to use a soap as the water-soluble anionic surfactant instead of sodium bis(2-ethylhexyl)sulfosuccinate.

In a "Brabender-Plasti-Corder" which is an internally heated mixing apparatus, 3 3.5 parts by weight of LD polyethylene of the type "LD 606" and 66.66 parts of "Ivory" soap chips were mixed at a machine temperature of approx. 177°C until a homogeneous mixture had been formed. The material was then compression molded using a rubber type mold having a mold cavity of 6.35 x 12.7 cm and a depth of 0.508 mm at a temperature of approx. 177°C and a pressure off

2531 kg/cm 2 . The obtained sample was continuously washed x approx.

3 days in a slow stream of tap water and then successively washed by immersion in 8 distilled water baths for approx. 1 hour in each water bath. The sample obtained still contained some residual soap and was difficult to handle.

Fig. 47 and 48 are photomicrographs of the product according to example 380 taken with a magnification of 195X and 2000X. It appears that the product has a relatively uneven polymer structure which has neither clear cell cavities nor interconnecting pores.

Example 381

A porous polymer was prepared using the method of Example 2, sample D, in US Patent No. 3,378,507, but modified to obtain a sample with some handling strength.

In a "Brabender-Plasti-Corder" which is an internally heated mixing apparatus, 75 parts of "Ivory" soap chips and 25 parts of LD-polyethylene of the type "LD-606" were mixed at a machine temperature of approx. 177°C and a temperature for the sample of approx. 166°C until a homogeneous mixture had been formed. The material was then injection molded in a 0.03 liter "VJatson-Stillman" type injection molding machine with a mold cavity diameter of 5.08 cm and. a depth of 0.508 mm. The obtained sample was continuously washed for approx. 3 days in a slow stream of tap water and then washed sequentially by immersion in 8 distilled water baths for approx. 1 hour in each bath. The sample obtained still contained some soap.

Fig. 45 and 4 6 are microphotographs of the product according to example 381 taken with a magnification of 240X and 2400X, respectively. The product according to this example does not have the typical cell structure of the products produced according to the invention, and this is evident from the photomicrographs.

Example 382

A porous polymer was prepared using the method of Example 3, Sample A, in US Patent No. 3,378,507.

In a "Brabender-Plasti-Corder" which is an internally heated mixing apparatus, 25 parts polypropylene of the type "F300 8N19" and 75 parts "Ivory" soap chips were mixed at a machine temperature of approx. 166°C until a homogeneous mixture had been formed. The material was then pressure molded into a rubber type mold. The sample obtained turned out to have a very low strength. Part of the obtained sample was continuously washed for approx. 3 days in a slow stream of tap water and then washed sequentially by immersion in 8 distilled water baths for approx. 1 hour in each bath. The washed product turned out to have very poor handling properties.

Fig. 51 and 52 are microphotographs of the product according to example 382 taken with a magnification of 206X and 2000X. The photomicrographs show that the product does not have the cell structure of the products produced according to the invention.

Example 383

The method according to example 3, sample A, in US patent document no. 3378507 was changed to produce a product with improved handling strength. 25 parts polypropylene of the type "F300 8N19" and 75 parts "Ivory" soap chips were mixed on an open two-roller rubber mill for approx. 10 minutes at a temperature of approx. 177°C until a homogeneous mixture had been formed. The material was then injection molded using a "Watson-Stillman" type injection molding machine with a mold cavity diameter of 5.08 cm and a depth of 0.508 mm. The obtained sample was continuously washed for approx. 3 days in a slow stream of tap water and then washed sequentially by immersion in 8 distilled water baths for approx. 1 hour in each bath. The sample obtained still contained an ideal soap. The product obtained proved to be stronger than the product according to Example 382.

Fig. 49 and 50 are microphotographs of the product according to example 383 taken with a magnification of 195X and 2000X. The uneven shapes shown in the photomicrographs can be clearly distinguished from the structure of the products produced according to the invention.

Example 384

A porous polymer was prepared in accordance with Example II of US Patent No. 3,310,505, but modified to obtain a more homogeneous mixture of the materials.

40 parts LD polyethylene of the type "LD 606" and 60 parts polymethyl methacrylate were in approx. 10 minutes mixed in a "Brabender-Plasti-Corder" at a machine temperature of approx. 177°C up to a

homogeneous mixture had been formed. The material was then re-

formed into sheets on a cold mill and then pressure formed using a heated 10.16 cm circular punch with a depth of 0.508 mm and a pressure of 30 tons for approx. 10 minutes. The material obtained was extracted for 43 hours with acetone in a large extraction apparatus of the "Soxlet" type.

Fig. 53 and 55 are photomicrographs of the product according to

example 384 taken with a magnification of 205X and 2000X. The uneven structure shown in the photomicrographs can be easily distinguished from the even structure of the products produced according to the invention.

Physical characterization of the products according to the examples

225 and 358

To obtain a quantitative understanding of the homogeneous

structure obtained according to the invention, certain samples of the microporous material and certain samples of material according to the state of the art were analyzed with an "Aminco" type mercury penetration porosity measuring apparatus. In fig. 30 and 31 show mercury intrusion curves for the 1.27 cm block according to Example 225 which was made from 25% polypropylene and 75% N,N-bis(2-hydroxyethyl)-tallow, and in fig. 32 shows a mercury intrusion curve for the 15.24 cm block according to example 225. All mercury intrusion curves are reproduced on a semi-log diagram with the equivalent pore sizes shown on the abscissa of the log scale. Fig. 30-32 show the typical narrow pore size distribution for the material according to the invention. It was determined that the 1.27 cm sample according to example 225 has a void content of approx. 76% and an average pore size of approx. 0.5 pm, while the 15.24 cm block has a void content of approx. 72% and an average pore size of approx. 0.6 pm.

In fig. 33 shows a mercury penetration curve for the product in example 358 which was prepared with 40% polypropylene and 60% N,N-bis(2-hydroxyethyl)-tallow. It appears from fig. 33 that the sample has the typical narrow pore size distribution. It was determined that the sample had a void content of approx. 60% and an average pore size of pa. 0.15 pm.

It is clear that the material according to the invention has

such pore size distributions that at least 80% of the pores in the materials

falls within no more than a decade on the abscissa of the mercury intrusion curve. The pore size distribution for the material can thus be characterized as "narrow".

Physical characterization of known commercially available materials

Example 385

The material of this example is commercially available as a microporous polypropylene sold under the trademark "Celgard 3501". In fig. 34 shows a mercury penetration curve for this sample, which shows a large distribution of pores within the range 70-0.3 pm. It was determined that the sample had a void content of approx. 35% and an average pore size of approx. 0.15 pm.

Example 386

The material of this example is commercially available as microporous polyvinyl chloride sold under the trade name "A-20". In fig. 35 shows a mercury penetration curve for the sample, and this curve shows a very wide pore size distribution. It was determined that the sample had a void content of approx. 75% and an average pore size of approx. 0.16 pm.

Example 387

The material of this example is commercially available as microporous polyvinyl chloride sold under the trade name "A-30". In fig. 36 shows a mercury penetration curve for the sample, and a very wide pore size distribution is evident from the curve. The sample was determined to have a void content of approx. 80% and an average pore size of approx. 0.2 pm.

Example 388

The material in this example is commercially available as microporous polypropylene sold under the trade name "Porex".

In fig. 37 shows a mercury penetration curve for the sample, and the curve shows a very wide distribution of very small cells and also a distribution of very large cells. It was determined that the sample had a void content of approx. 12% and an average pore size of approx. 1 p.m.

Example' 38 9

The material in this example is commercially available as microporous polyvinyl chloride sold under the trade name "Millipore BDWP 29300". In fig. 38 shows a mercury penetration curve

for the sample, and the curve shows a relatively narrow distribution within the range 0.5-2 pm and also a number of cells with a smaller size than approx. 0.5 pm. It was determined that the sample had a void content of approx. 72% and an average pore size of approx. 1.5 µm.

Example 3 90

The material in this example is commercially available as microporous cellulose triacetate sold under the trademark "Metricel TCM-200"- In fig. 39 shows a mercury penetration curve for the sample, and the curve shows a wide pore size distribution up to approx. 0.1 pm. It was determined that the sample had a void content of approx. 82% and an average pore size of oa. 0.2 pm.

Example 391

The material in this example is commercially available as a microporous acrylonitrile/polyvinyl chloride copolymer sold under the trade name "Acropor WA". In fig. 40 shows a mercury penetration curve for the sample, and the curve shows a wide pore size distribution. It was determined that the sample had a huiroim content of approx. 64% and an average pore size of approx. 1.5 p.m.

Physical characterization of known materials

Examples 380-384

The known products of Examples 380-384 were also analyzed by mercury intrusion. In fig. 41-43 show mercury penetration curves, and the curves show the wide pore size distribution for the products according to respectively example 381,

380 and 383. On fig. 44 shows a mercury penetration curve for the product according to example 384 and the curve shows a distribution of pores within the range 4 5 and 80 pm and also a number of very small pores. The products according to examples 308, 381, 383 and 384 were determined to have a void content of respectively about. 54, 46, 54 and 29% and an average pore size of about. 0.8, 1.1, 0.56 and 70 pm.

Examples 392-299

These examples describe the applicable concentration range for polymer/compatible liquid for the production of homogeneous, porous polymer intermediates from polymethyl methacrylate and 1,4-butanediol using the standard production method. In each example, the intermediate product produced had a thickness of approx. 1.3 cm and a diameter of approx. 6.4 cm. The polymethyl methacrylate is sold under the trade name "Plexiglas Acrylic Plastic Molding Powder, lot No. 386491". The details regarding the preparation are given in Table XXVII.

The 1,4-butanediol was removed from the product according to example 395, and the structure obtained was determined to be the cell structure according to the invention, as shown in fig. 61 of which the microporous product appears with a magnification of 5000X. The same polymer/liquid system used in example 394 was also cooled at rates up to 4000°C per minute, and still the cell structure according to the invention was obtained.

Example 4 00

The porous polymer intermediate was prepared using the standard preparation method and by heating 30% polymethyl methacrylate, as used in the previous examples, and 70% lauric acid to 175°C and cooling to form the porous polymer intermediate. The lauric acid was removed from the intermediate product obtained to form the microporous cell structure according to the invention.

Example 401

The porous polymer intermediate was prepared using the standard manufacturing method and by heating 30% Nylon 11 and 70% ethylene carbonate to a temperature of 218°C and cooling the resulting solution to form the porous polymer intermediate. The ethylene carbonate was removed from the intermediate product, and it was determined that the microporous polymer obtained had the cell structure according to the invention.

Example 402

The porous polymer intermediate was prepared using the standard preparation method and by heating 30% Nylon 11 which was the same as used in the above example, and 70% 1,2-propylene carbonate to a temperature of 215°C and cooling it solution obtained to form the porous polymer intermediate. The propylene carbonate was removed from the intermediate product, and it was determined that the microporous polymer obtained had the cell structure according to the invention.

Examples 403-422

Examples 403-422 describe the formation of the porous polymer intermediates from polymer/liquid tanks containing different amounts of Nylon 11, as used in the above examples, and tetramethylene sulfone, which is sold under the trade name "Sulfone W", and containing approx. 2.5% water. The different concentrations were cooled at different rates and from different solution temperatures, as indicated in Table XXVIII from which it is also evident that increased cooling rates and an increased concentration of the polymer generally cause the cell sizes to become smaller.

From the above table XXVIII it also appears that at concentrations from 40% to 10% liquid, no visible porosity is obtained for the system that was cooled at a rate of 20°C per minute. Such results are quite reasonable to expect, as can be seen from fig. 62 which shows the melting curve for the Nylon 11/tetramethylsulfone concentration range and also the crystallization curves at the different cooling rates. It appears from fig. 62 that at a cooling rate of 20°C per minute, the system containing 40% liquid does not fall within the essentially flat part of the crystallization curve, and thus it was not expected that this system would form the desired microporous structure. Fig.63 is a photomicrograph taken with a magnification of 2000X of the product according to example 409 and shows the typical cell structure of the products according to examples 403-418.

Example 423

The porous polymer intermediate was prepared using the standard manufacturing method and by heating 30% polycarbonate sold under the trademark "Lexan" and 70% menthol to a temperature of 206°C and cooling to form the porous polymer intermediate. The methol was extracted and a cellular microporous structure was obtained as shown in fig. 64 which is a photomicrograph of the product of this example taken at a magnification of 2000X.

Example 424

This example describes formation of the microporous cell structure according to the invention from poly-2,6-dimethyl-1,4-phenylene oxide, which is commonly referred to as polyphenylene oxide. The homogeneous micro-porous polymer intermediate was prepared from 30% of this polyphenylene oxide and 70% N,N-bis(2-hydroxyethyl)-tallowamine heated to a dissolution temperature of 275°C, and the intermediate was prepared using the standard preparation method . The liquid was removed from the intermediate product, and the cell structure according to the invention was obtained, as shown in fig. 65 which is a photomicrograph of the product of this example taken at a magnification of 2000X.

Example 425

This example describes formation of the ikJce cell-containing product according to the invention by cooling a homogeneous solution of 40% polypropylene, as used in the above examples, and 60% dibutyl phthalate. The solution was extruded onto a cooled belt to a thickness of approx. 0.25 mm, and the cooling rate was over 2400°C. A certain amount of dispersion was applied to the surface of the pasture at a location prior to where the solution was extruded onto the belt. The liquid was removed from the resulting film, and a non-cellular, microporous product was obtained as shown in fig. 65 which is a photomicrograph of the product according to this example taken with a magnification of 2000X.

Example 426

This example describes the formation of the non-cellular product according to the invention by cooling a homogeneous solution of 25% polypropylene, as used in the above examples, and 75% N,N-bis(2-hydroxyethyl)-talgamine in the same way as according to example 425. The liquid was removed from the resulting film, and a non-cellular, microporous product was obtained as shown in

fig. 67 which is a photomicrograph of the product of this example taken at a magnification of 2000X.

The products according to examples 425 and 426 were analyzed by mercury penetration pore measurement, and the respective penetration curves are shown in fig. 68 and 69. It appears that both products generally have narrow pore size distributions, but the product according to example 426 has a much narrower distribution than the product according to example 425. Thus, the product according to example 425 has a calculated S-value of 24.4, while the product according to example 426 has a calculated S-value of just 8.8. However, the average pore size for the product according to Example 425 is very small, specifically 0.096 µm, while the average pore size for the product according to Example 426 is 0.589

In order to quantitatively demonstrate the distinctive features of the cell materials according to the invention, a number of such microporous products were produced using the standard production method, and details in connection with this production are compiled for examples 427-457 in table 29. The products according to these examples were analyzed using by mercury intrusion porosity measurement to determine the products' average pore diameter and S values, and by scanning electron microscopy to determine the products' average cell size S. The results of these analyzes are set forth in Table XXX.

The data in tables XXIX-XXXII are combined in fig. 70 which shows a plot of log S/C in relation to log C/P. It appears from fig. 70 that the cell structure according to the invention can be defined by having a log C/P of 0.2-2.4 and a log S/C of -1.4 to 1.0, and the polymer will more commonly have a log C/ P of 0.6-2.2 and a log S/C of -0.6-0.4.

It thus appears from the above description that the present invention provides a simple method for the production of microporous polymer bodies from any synthetic, thermoplastic polymer and with greatly varying thickness and shape. The microporous polymer bodies can have a distinctive microcell structure and are in each case distinctive in that they have pore diameters with a relatively narrow size distribution. These polymer bodies are produced by first choosing a liquid which is compatible with a polymer, i.e. which forms a homogeneous solution together with the polymer and which can be removed from the polymer after cooling, then choosing the amount of liquid and carrying out cooling of the solution in such a way that it is ensured that the desired microporous polymer structure will be obtained.

It also appears from the above description that the present invention provides microporous polymer products which contain relatively large amounts of functionally usable liquids as polymer additives and which behave as a solid material. These products can be advantageously used for a number of different applications, such as e.g. in the production of concentrate mixtures.

Claims (11)

1. Three-dimensional, microporous, isotropic, essentially homogeneous polymer body with a relatively narrow pore size distribution, produced by a mixture of one or more thermoplastic polymers mixed with a compatible liquid having been heated at a sufficient temperature and for a sufficient time to that a homogeneous solution is formed which is formed, and the formed solution is cooled and at least a significant part of the comparable liquid is removed, characterized in that it has a cavity volume of 10-90% and a sharpness factor S of 1-30, the sharpness factor S being determined by analysis of a mercury penetration curve and is defined as the ratio between the pressure at which 85% of the mercury has penetrated and the pressure at which 15% of the mercury has penetrated, and as the body is produced by the formed solution having been cooled so far and so rapidly that thermodynamic non-equilibrium conditions are achieved and a liquid-liquid phase separation is initiated, and that the cooling while avoiding mixing or other shearing forces are continued until a solid body has been formed before at least a substantial part of the comparable liquid is removed in a manner known per se to form the microporous body. 2. Microporous body according to claim 1, characterized in that it contains a long series of essentially spherical cells with an average diameter C of 0.5-100 µm which are essentially evenly distributed over the entire structure, the adjacent cells being connected to each other via pores having a smaller diameter P than the said cells, and the ratio between the average cell diameter and the average pore diameter C/P being 2:1-200:1, log C/P is 0.2-2.4 and log S/C from -1.4 to +1. 3. Microporous body according to claim 2, characterized in that it has an average cell diameter C of 1-20 µm and an average pore diameter of 0.05-10 µm. 4. Microporous body according to claims 2-3, characterized in that it has a sharpness factor of 2-20. 5. Microporous body according to claims 1-3, characterized in that it has a sharpness factor of 1-10. 6. Microporous body according to claim 1, characterized in that the thermoplastic polymer is polypropylene and that it has a sharpness factor of 1-10 and pores with an average diameter of 0.2-5 µm. 7 . Process for the production of an essentially homogeneous, three-dimensional, microporous, isotropic polymer body with a void volume of 10-90% and a sharpness factor S of 1-30, where a mixture of one or more thermoplastic polymers in mixture with a compatible liquid is heated at a sufficient temperature and for a sufficient time so that a homogeneous solution is formed which is formed, and the formed solution is cooled and at least a significant part of the comparable liquid is removed, characterized in that the formed solution is cooled so far and so quickly that thermodynamic non-equilibrium conditions are achieved and a liquid-liquid phase separation is initiated, and that the cooling, avoiding mixing or other shear forces, is continued until a solid body has been formed before at least a significant part of the comparable liquid is known per se way is removed to form the micro-porous structure. <8.> Method according to claim 7, characterized in that to form a solution, the mixture is heated to a temperature close to or above the softening point of the thermoplastic polymer. 9. Method according to claim 7 or 8, characterized in that the cooling is carried out at a rate such that during the cooling, a long series of liquid droplets of essentially the same size is formed in a continuous liquid polymer phase. 10. Method according to claims 7-9, characterized in that a mixture of 90-10% polymer and 10-90% inert liquid is used. 11.- Use of the microporous body according to claim 1-g for absorption and release of functional liquids.