JPH03205435A - Manufacture of microporous cellular polymer - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The following description details the invention and related art to facilitate an understanding thereof.

TECHNICAL FIELD This invention relates to porous polymeric structures and methods of manufacturing them. More particularly, the invention provides a unique and easy method for producing microporous polymeric and agglomerate structures that are easy to manufacture and feature relatively homogeneous, three-dimensional, cellular microstructures. It concerns a method.

Several very different techniques have previously been developed for producing microporous polymeric structures. This technique ranges from what is referred to by those skilled in the art as classical phase inversion, to nuclear bombardment, incorporation of microporous solid particles into a matrix and subsequent leaching, to sintering the microporous particles together in some manner. It's reaching. Conventional efforts in this field have involved other techniques as well as countless variations on what are considered classic or basic techniques.

The importance of microporous polymeric products arises from the myriad possible applications for this type of material. The possible applications are well known and range from ink pads and the like to skin-like breathable sheets to filter media. 1. However, for all possible applications, commercial use has been relatively modest. And commercially used techniques have various limitations,
This allows the versatility necessary to expand this application to reach a possible market for microporous products.
Yes.

As mentioned above, some commercially available microporous polymeric products are made by nuclear bombardment techniques. With this technique, a fairly narrow pore size distribution can be obtained; however, to ensure that the polymer does not degrade during production, the pore volume must be relatively low. c (i.e., less than about 10% void space). Many polymers cannot be used in this technology due to the polymer's lack of ability to corrode. Furthermore, this technique requires that a relatively thin sheet or film of polymer be used and is subject to "double tracking," which results in the formation of oversized pores.
Significant technical knowledge must be used in carrying out the process to avoid this.

Classical phase inversion has been used commercially to form microporous polymers and certain other polymers from cellulose acetate. Classical phase change PA R.K.Keating's SYNTHFtT CPOLYMFJ C MIDMMBRANF! Described in detail in S. McGraw-Hill, 1971. In particular, on page 117 of this document it is explicitly stated that classical phase inversion involves the use of at least three components: a polymer, a solvent for this polymer and a non-solvent for this polymer. .

Reference may be made to US Pat. No. 3,945,926 which teaches the formation of polycarbonate resin membranes from a casting solution containing a resin, a solvent, and a swelling agent and/or non-solvent. Lines 42-47, column 15 of the above patent states that in the complete absence of swelling agent, phase inversion does not normally occur and that at low concentrations of swelling agent, structures with closed cells result. be done.

From the above discussion, it can be seen that classical phase inversion requires the use of solvents for the system at room temperature, making it extremely difficult for many other useful polymers to be substituted for 5-fur polymers such as cellulose-2 acetate. It's obvious. 1 From the standpoint of the octopus process, this classical phase inversion method generally has to be extracted subsequently.

F・F due to the use of large amounts of solvent used in the preparation of the solution
LUNO, LIMITED TO THE FORMATION. It is clear that conventional phase inversion requires a relatively high degree of process control to obtain structures of the desired shape. Thus, the relative concentrations of solvent, nonsolvent, and swelling agent are as follows: U.S. Pat.
As discussed in No. 6, columns 14-16, critical adjustments must be made. On the contrary, try to change the dimensions and homogeneity of the resulting structure! According to 9, the above parameters must be changed.

Other commercially available microporous polymers are made by sintering microporous particles of polymers ranging from high density polyethylene to polyvinylidene fluoride. However, it is difficult with this technique to obtain products with the narrow pore size distribution required for many applications.

Yet another common technique that has been the subject of significant prior attempts involves heating various liquids and polymers to form a dispersion or solution, followed by cooling and subsequent removal of the liquid, such as with a solvent. Methods of this type are described by way of example only and non-exclusively in the following US patents: No. 3,607,79
No. 3; No. 3,378, 5 mouth No. 7; No. 3, 3 1 0,
5 0 5; No. 3.7 4 8.2 8 7; No. 3
, 5 3 6,796; No. 3, 6 No. 8,073 and No. 3, 8 1 2.2 '2.4. The techniques described above probably suffer from the lack of previously developed specific methods and economic possibilities.
However, it is unlikely that it was used commercially to any degree, if at all. Also, this conventional method does not allow for the production of microporous polymers that typically combine desired pore sizes and pore size distributions with relatively homogeneous microcellular structures.

Regarding microporous polymers obtained by the prior art, hitherto known methods have a relatively narrow pore size distribution with a pore size distribution of about 0.
It was not possible to produce isotropic olefinic or oxidized polymers with a majority of pore sizes within the range of 1 to about 5 microns, and thus could not exhibit a high degree of pore size uniformity throughout the sample.

Some prior art olefinic or oxidized polymers have pore sizes within the above range, but without a relatively narrow pore size distribution, thus making this material difficult to use in applications such as filtration that require a high degree of selectivity. Make it worthless. Furthermore, conventional microporous olefinic or oxidized polymers, which are considered to have relatively narrow particle size size distributions, are outside the above range and are typically not suitable for use in applications such as ultrafiltration. has an absolute pore size with a substantially smaller pore size. Finally, some prior art olefinic polymers have pore sizes within the aforementioned range and what is considered to be a relatively narrow pore size distribution.

However, this material is made through the use of techniques such as stretching that impart a high degree of orientation to the resulting isotropic material, making this undesirable for many applications. Thus, there is a need for microporous olefinic and oxidized polymers having pore sizes in the range of about 0.1 to about 5 microns and characterized by a relatively narrow isotropic pore size distribution. There is.

Also, a major drawback of many microporous polymers previously available is the low flow rate of these polymers when used in structures such as microfiltration membranes. One of the major reasons for this low flow rate is the typically low voids in many of this polymer. It is volume. Thus, perhaps more than 20 or less of the polymer structure is the "void" volume through which the filtrate flows, and the remaining 80 φ of the structure is the polymer resin forming the microporous structure. There also exists a need for microporous polymers having a high degree of void volume, particularly with respect to olefinic polymers.

The aforementioned castro (castro) and stole (
The StO1'1 application describes a highly advantageous method of converting certain types of liquid amine antistatic agents into materials that behave as solids. The benefits of the resulting treatment are real and significant. It would be equally beneficial to be able to convert other useful functional liquids, such as flame retardants, into materials that behave as solids.

It is therefore an object of the present invention to provide microporous polymeric products characterized by relatively homogeneous and narrow pore size.

Another object is to provide a simple process that allows economical production of microporous polymers.

Yet another object is to provide a process for making microporous polymer products that has applicability to a large number of useful thermoplastic polymers. A related and more specific purpose is
The object of the present invention is to provide a method for easily forming a microporous polymer from a condensation polymer and an oxidized polymer.

Yet another object of the present invention is to provide microporous polymers in structures ranging from thin films to relatively thick blocks.

Another purpose is to provide for the conversion of functional liquids into materials with solid-state properties.

Other objects and advantages of the invention will become apparent from the following discussion and the accompanying drawings.

While the invention is susceptible to various modifications and alternative forms, the preferred embodiments herein are shown in detail. However, the intention is not to limit the invention to the specific forms described! It should be understood that there is no ll. On the other hand, it is intended that all modifications and other forms be included within the scope of the present invention as expressed in the claims.

It has now been discovered that any synthetic thermoplastic polymer can be made microporous by first heating the polymer described above and a compatible liquid as discussed below at a temperature and time sufficient to form a homogeneous solution. did. The solution thus formed is then allowed to assume the desired shape and subsequently cooled in this shape to a rate and temperature sufficient to initiate thermodynamically non-equilibrium liquid-liquid phase separation. . Since the solution is cooled in the desired shape, no mixing or other shear forces are applied while the solution is undergoing cooling. stomach. This cooling is continued so that a solid forms.9 This solid only needs to acquire sufficient mechanical integrity to allow it to be handled without causing physical deterioration. Finally, at least a substantial portion of the compatible liquid is removed from the resulting solid to form the desired microporous polymer.

Particular Novel Tx Microporosity of the Invention 2. The oxidized polymer is characterized by a narrow pore size distribution as measured by mercury immersion porosimetry. This narrow pore size distribution can be expressed analytically as the Scharf 0ness function +l s +T, which is explained in detail below. The ``S'' values of the red 7,゜oxidized polymers of the present invention range from about 1 iL to about 10. The M f4 bodies of the front part of the Kiteki invention range from about 0.10 to about 5 microns. The average pore diameter over the range is defined as 1, approximately 0.
2 to about 1 micron is preferred. Furthermore, this microporous product is substantially isotropic and therefore has essentially the same cross-sectional shape when analyzed along any spatial plane.

In another aspect of the invention, the mixture of the synthetic thermoplastic polymer, specialty, or blend of one or more of the foregoing polymers and a compatible liquid is heated at and for a period of time sufficient to form a homogeneous solution. A method for producing a microporous polymer is carried out in such a manner that the microporous polymer is heated to . This solution is then cooled, thus forming a large number of droplets of substantially the same size in substantially the same amount of time.

This cooling is then continued to solidify the mass and at least a substantial portion of the liquid is removed from the resulting solids to form the desired cellular polymer structure.

The method described above results in a cellular, three-dimensional, void microstructure, characterized by a series of closed cells having a substantially spherical shape and pores or passageways in communication with adjacent cells. Resulting in a microporous polymer product. The basic structure is relatively homogeneous, the cells are evenly spaced throughout three dimensions, and the interconnecting pores have relatively narrow diameters with a size distribution as measured by mercury infiltration. For ease of reference, microporous polymers having such a structure are referred to as ``cellular''.

A related aspect of the invention provides novel microporous polymeric products that behave as solids and contain relatively large amounts of functionally useful liquids, such as polymeric additives, including flame retardants. In this manner, the useful liquid gains the processing advantages of a solid material that can be used directly, for example as a masterbatch. This product uses a functional liquid as the compatible liquid and the removal of this compatible liquid can be carried out either directly or by reloading the microporous polymer after removal of the compatible liquid. It can be formed either by incorporating a functional liquid or by displacing a compatible liquid before removal, such as by incorporating a functional liquid.

Broadly, the practice of the method of the invention preferably involves heating the desired polymer with a compatible raw liquid to form a homogeneous solution;
It involves cooling the solution in a suitable manner to form a solid material, followed by extracting the body overnight to form a microporous material. Considerations involved in practicing the invention are described in detail below.

As mentioned above, the present invention provides a technique for converting any synthetic thermoplastic polymer into microporous material.

Therefore, the method of the present invention (d: Ne111-+L-Yoko-44) is applied to condensation polymers and oxidized polymers.

4L, polystyrene, polyvinyl chloride, acrylonitrile-butadiene-styrene-polymastyrene-acrylonitrile copolymer, non-butadiene copolymer, poly(4-methyl-pendene-1), polybutylene? , polyvinylidene chloride, polyvinyl butyral, chlorinated polyethylene, ethylene-vinyl acetate copolymer, polyvinyl methacrylate, polymethacrylate/polyphenylene oxide are examples of oxidized polymers that can be used. Useful condensation polymers include polyethylene terephthalate, polybutylene terephthalate, nylon 6, nylon 11, nylon 13, nylon 66, polycarbonate and polysulfone.

Selection of Compatible Liquids Thus, in order to practice the present invention it is necessary to first select the synthetic thermoplastic polymer that is to be rendered microporous. Once a polymer is selected, the next step is the selection of appropriate compatible liquids and the relative amounts of polymer and liquid to be used. Of course, blends of one or more polymers can be used in the practice of this invention. Functionally, the polymer and liquid are heated with stirring to the temperature necessary to form a clear homogeneous solution. Is the solution 1. If it is desired to form a liquid at a concentration of
b and cannot be used with certain polymers.

Because of selectivity, it is not possible to fully predict the operability of a particular liquid with a particular polymer.

However, some useful step-by-step guidance can be provided. Therefore, if the polymer involved is non-polar, non-polar liquids with similar solubility parameters at the solution temperature are likely to be more useful. When this parameter is not available, a more easily available room temperature solubility parameter can be mentioned for general phase needles. Similarly, for polar polymers, polar organic liquids with similar solubility parameters should be investigated first. Also, the relative polarity or non-polarity of the liquid should be matched to the relative polarity or non-polarity of the polymer.

Furthermore, with respect to hydrophobic polymers, useful polymers typically have little or no water solubility. On the other hand, polymers that tend to be hydrophilic generally require liquids with some water solubility.

Regarding suitable liquids, 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 miscellaneous. Certain types of organic compounds of various types have been found to be useful, including hydrocarbons and heterocycles. However, it should be noted that this concept is highly selective. Thus, not all saturated aliphatic acids are useful, and furthermore, not all liquids that are useful for high density polyethylene are necessarily useful for polysterene, as an example.

As will be appreciated, useful ratios of polymer and liquid for any particular system can be readily developed from the values of the parameters subsequently discussed.

It will be appreciated that if a blend of one or more polymers is used, the useful liquid will typically be operable with all of the polymers involved.
Must be. However, it is necessary for the liquid to be operable with all the polymers used, as it is possible for the polymer blend to have additional properties. As an example, if one or more polymeric components significantly affect the properties of the formulation and are present in relatively small amounts such as 1f or more, the liquid used may Must be operable with multiple polymers.

Additionally, while the most useful materials are liquid at ambient temperature, they are solid at room temperature unless solutions can be formed with the polymer at elevated temperatures and the material does not interfere with the formation of the microporous structure. Some advantage can be used. More particularly, solid materials can be used to the extent that phase separation occurs during the cooling process, discussed below, and liquid-to-liquid separation. The liquid medium used generally varies from about 101:c to about 90c.

We will discuss here whether the selected liquid forms a solution with the polymer and what is the degree of this collapse? Any agglomerative polymer can be used as long as successive polymeric polymers occur upon a 711 intermediate pairing, and these are discussed in detail below.

Some summaries of this system are useful in order to determine the range of polymer and liquid systems that can be manipulated. 4. Formation of microporous polymers from polypropylene Particular alcohols, such as 2-pendylamino-1-propanol and 3-7enyl-1-,y0ropanol; aldehydes, such as salicylaldehyde, amides, such as N, N-Diedyl-m-}ylamide: amines such as N-hexyldiethanolamine, N-pehenyldiethanolamine, N-cocodiethanolamine, penzylamine, N,N-bis-β-hydroxyethylcyclohexylamine, diphenylamine and 1,12-diaminododecane Esters, such as methyl benzoate, penzyl benzoate, phenyl salicylate, methyl salicylate and dibutyl phthalate; and ethers, such as diphenyl ether, 4-fromoxy7xyl ether and dibenzyl ether, have been found to be useful. did. Additionally, halocarbons such as 1,1,2,2-tetrabromoethane and hydrocarbons, such as trans-stilbenes and other alkyl/arylphosphatites, are also useful, as are ketones such as methylnonylketone. It is.

? Alcohols such as decyl alcohol and 1-dodecanol, secondary alcohols such as 2-syndecanol and 6-undecanol, ethoxylated alcohols such as N-lauryldiethanolamine, aromatic amines such as N,N-diethylaniline, diesters, For example, dibutyl sebacate and dihexyl sebacate and ethers such as diphenyl ether and benzyl ether have proven useful. Other useful liquids are:
compounds such as octabmodiphenyl, hexabromobenzene and hexaglomocyclodecane, hydrocarbons such as 1-hexaacane, diphenylmethane and naphthalene, aromatic compounds such as acetophenone and other organic compounds such as alkyl/aryl phos Phatites, and quinolins) and ketones, such as methyl nonyl ketone.

The following liquids have been found useful for forming microporous polymers from moderate density polyethylene: hexanoic acid, caprylic acid, decanoic acid, uranate, lauric acid, myristic acid, Saturated aliphatic acids including palmidic acid and stearic acid, unsaturated aliphatic acids including oleic acid and erucic acid, aromatic acids including benzoic acid, phenylstearic acid, polystearic acid and xylylbehenic acid; Acids including branched carboxylic acids, tall oil acids, and rosin acids with an average chain length of 11 carbons;
Primary saturated alcohols, including 1-octanol, nonyl alcohol, tacyl alcohol, 1-decanol, 1-dodecanol, tridecyl alcohol, cetyl alcohol and 1-heptadecanol, undecylenyl alcohol and oleyl alcohol -Unsaturated alcohols, secondary alcohols including 2-octanol, 2-undecanol, dinonylcarbinol and diundecylcarbinol, 1-phenylethanol, 1-phenyl-i4tan]/? Aromatic alcohols including alcohol, nonylphenol, phenylste7lyl alcohol and 1-naphthol. Other useful hexyl-containing compounds include the phosphoryoxyethylene ether of oleyl alcohol and polypropylene glycol having a number average molecular weight of about 400. Even more useful 1. Cyclic alcohols such as butyl hexanol and menthol, aldehydes including salicylaldehyde, primary amines such as octylamine, tetradecylamine and heylidecylamine, secondary amines such as bis(1- methyl pentyl) amine and? (-lauryl diethanolamine, N
-tallow diethanolamine, N-stearyldiethanolamine and N-cocodiethanolamine. Contains ethoxylated amines.

Other useful liquids id N-e'ec-butylaniline, dodecylaniline, N,N-dimethylaniline, N
, N-diethylaniline, 1. Diamines including 8-diamino-p-methane, branched tetramines and other amines including cyclododecylamine,
Cocoamide, hydrogenated tallowamide, octadecylamide, erucyamide, N,N-jedyltoluamide and N
-}Rimeb'0-lupu-a amide containing panstamide;
Saturated aliphatic esters, stearyl acrylate, including methyl caf 0-lylate, editerlaure-1, isoprobyl myristi, ethyl palmitate, isoprobyl palmitate, methyl stearate, impbuur stearate and tridecyl stearate. , butylphenyl stearate, butylphenyl stearate, unsaturated esters including butyl oleate, alkoxy esters including butylphenyl stearate and butoxyethyl oleate, vinyl phenyl stearate, isobutylphenyl stearate, tritecylphenyl stearate rate, methyl benzoate, ethyl benzoate, butyl benzoate, penzyl benzoate, phenyllau 1
Notes: Aromatic esters including phenyl salicylate, methyl salicylate, 1/1 and benzyl acetate, dimethyl phenylene dinutherate, diethyl fucreto, dibutyl fucray 1, diisooctyl phthalate, dicapryl adishate , dibutyl sepacate, dihexyl IL. Contains diesters including sebacate, diisoocter sebacate, dicapryl sebacate, and dioctyl sebacate. Liquid gel for fZ and other A1s, polyethylene glycol (approximately 4
What is the average molecular profile of 0 mouths? Polyhydroxy link esters (triglycerides), including mountains
Gerycerol monostearl/-}, glycerol monooleate, glycerol distear-1, glycerol dioleate 1, glycerol monooleate, Cl)
Shichikuchirudisteare-1, glycerol dioleate and}! J Methylolpropane monophenyl stearate, cyphenyl ether and hypenyl stearate: f--
ter ((containing moether, hexagonal pentadiene, , l-cutabromo 1! phenyl, 5''cabro-diphenyl)';/- haloke-1 compound containing oxy-12 and 4-promodiphenyl ether,・Hydrocarbons including 1-nonene, 2-nonene, 2-undecene, 2-heptadecene, 2-nonadecene, lo-eicosene, 9-nonadecene, diphenylmethane, l-rifenylmethane and h!-lansu-stilbene, 2 -hef1tanone, methylnonylketone, 6-undecanone, methylundecylketone, 6-tridecanone, 8--!!ntacanone, 11-pentadecanone, 2-heptadecanone, 8-he7°tadecanone, methylhebutanone rsilketones, aliphatic ketones including dinonyl ketones and distearyl ketones, aromatic ketones including acetophenones and penzophenones, and other ketones including xanthone. Still further useful liquids include
Nil phosphate, polysiloxane, Madetsu 1 Hyacinth (trade name) (Ammeria Negra), Terpineol Primega 61 (simplified product name) (GID-Delawante), Bath oil Fragrance #5B64K (trade name) ( International Flavor and Fragrance Co., Ltd.), Hos', Otclair P315C (trade name) (morganophosphite), Hosk 1/-L P576 (trade name) (organophosphite), styrenated nonylphenol, quinoline and quinaridine. Contains a phosphorus fI1 compound.

To form a microporous polymer product with polystyrene,
Useful liquids (tris-halodanide)
1-, aryl/alkyl phosphite, L1,2.
2-Te 1.Rub Mouth Moethane, 1.Libromoneopentyl Alcohol, '10% Boranol C. P. 60 mouths (
Product name) Poly; Tall and l-rib r7 monemepentyl alcohol 6 mouths η, 1) 7. -βchloroethyl phosphate, tris(1,ro-isoprovir) phosphate, tri(dichloroprovir) phosphate
dichlorobenzene and 1-dodecanol.

When molding microporous goblets using polyvinyl chloride, useful liquids are 1-xypendyl alcohol, 2
-pendylamino-1-propanol, an aromatic alcohol containing gold, and 1,3-dichloror. I-2)2 Contains other hydroxyl-containing liquids including monopropanol. Still other useful liquids include halogenated compounds, including Firemaster T33P (tetrabromophthalic diester), and aromatic hydrocarbons, including transstillpene.

Additionally, microporous products have been made from other polymers and copolymers and blends in accordance with the present invention. Thus, to form a microporous product from a styrene-butadiene copolymer, a liquid padcyl alcohol, N-tallow diethanolamine, a liquid useful to form an N-type polymer, is N-tallow diethanolamine. , N-cocodiethanolamine, dibutyl phthalate and diphenyl ether. Microporous polymeric products using high impact polystyrene can be formed by using hexab-mobiphenyl and alkyl/aryl phosphites as the liquids.゛Nori. Noryl ``Polyphenylene Oxide Polystyrene Blend'' (General Electric Company) produces microporous polymers from a blend of N-cocodiethanolamine, N-tallow diethanolamine, diphenylamine, digtylphthalate and chlorinated polyethylene. combined pa1-dodecanol,
It is made by using diphenyl ether and N-tallow diethanolamine. Using 1-dodecanol as the liquid, microporous polymers are made from the following formulations: polypropylene-chlorinated polyethylene, high-density polyethylene-chlorinated polyethylene, high-density polyethylene-polyvinyl chloride, and high-density polyethylene and Acrylonitrile-butadiene-styrene (ABS) terpolymer. It has been found that 1,4-butanediol and lauric acid are useful for forming microporous products from polymethyl methacrylate. Is microporous nylon 11 made using ethylene carbonate, 1,2-zolobylene carbonate, or tetramethylene sulfone? Ru. Menthol can be used from microporous products made from polycarbonate.

Selection of Polymer and Liquid Concentrations Determination of the amount of liquid used can be determined by determining the amount of liquid used (
binodial) and spinodal (Spinodial)
dal) curve, and an exemplary curve is shown in FIG. As shown there, Tm represents the maximum temperature of the pinodial curve (i.e., the maximum temperature of the system at which pinodal decomposition occurs), Tucs represents the upper critical solution temperature (i.e., the maximum temperature at which spinodal decomposition occurs), and φm at Tm φC represents the critical concentration and φχ represents the polymer concentration of the system required to obtain the unique microporous polymer structure of the present invention. In theory, φm and φC should be substantially the same; however, as is known, due to the molecular weight distribution of commercially available polymers, φC is about 5 weights greater than φm. To form the unique microporous polymers of this invention, the polymer concentration φX used in a particular system must be greater than φC. If this polymer concentration is less than φC, the phase separation that occurs as the system is cooled constitutes a continuous liquid phase with discontinuous polymer phases. On the other hand, using the correct polymer concentration ensures that the continuous phase formed upon cooling to the phase separation temperature is the polymer phase, which yields the unique microcellular structures of the present invention. It is necessary for Similarly, clearly the formation of a continuous polymer phase upon phase separation requires that a solution be formed first. When the process of the invention is not carried out and the dispersion is first formed, the resulting microporous product is similar to that obtained by sintering the polymer particles together.

Therefore, as will be appreciated, the applicable polymer concentrations and the amount of liquid available will vary with each system.

Suitable phase diagram curves for some systems have been previously disclosed. However, if a suitable curve is not available, this can easily be disclosed using known techniques. For example, suitable techniques include Smol4ers,
Kolloid Z+ulZ+ Polymer from Van Aartsen and Steenbergen, 2 4.3
+ 1 4 (1 9 7 1')
It is described in

A more general graph of temperature versus concentration for a hypothetical polymer-liquid system is shown in Figure IA. The portion of the curve from γ to α represents thermodynamic equilibrium liquid-liquid phase separation. The α to β curve represents equilibrium liquid-solid phase separation, which would be recognized as a normal freezing point depression curve for a hypothetical liquid-monopolymer system.

The upper shaded area represents upper liquid/liquid immiscibility that may exist in some systems. The dotted line represents the decrease in crystallization temperature as a result of cooling at a rate sufficient to obtain thermodynamic nonequilibrium liquid-liquid phase separation. The crystallization plateau relative to the composition curve limits the usable composition range, which is a function of the cooling rate used, as discussed in further detail.

Thus, for any given cooling rate, it is possible to obtain a crystallization temperature of 70% of the resin or compatible liquid, and in this way it is possible to obtain the desired fineness at a given cooling rate. By plotting the crystallization curves described above for producing a porous structure? Figure 55 is a plot of temperature versus polymer/liquid concentration showing the melting curves at a heating rate of 16° C. and the crystallization curves for polypropylene and quinoline over a wide concentration range. As can be seen regarding the crystallization curve, the fractional weight is 916°.
At a cooling rate of C, suitable concentration ranges from about 20% polyzolobylene to about 70% polypropylene.

FIG. 56 is a graph of temperature versus polymer/liquid composition for polynolopyrene and N,N-bis(2-hydroxyethyl)tallowamine. The upper curve is a plot of the melting curve at a heating rate of 16°C per portion. The downward curve is in descending order, and it's allotted! 18°C1 16°C13
Figure 2 is a plot of crystallization curves at cooling rates of 2°C and 64°C. This curve shows two coincident phenomena that occur as the cooling rate increases.

First, the flat part of the curve showing a relatively stable crystallization temperature over a wide concentration range decreases with increasing cooling rate, which means that as the cooling rate increases, the actual crystallization temperature decreases. Show that.

The second observable phenomenon is the change in the slope of the crystallization curve that occurs with changes in the rate of cooling. Therefore, the flat portion of the crystallization curve appears to increase as the cooling rate increases. Consequently, it is estimated that by increasing the rate of cooling, one can correspondingly increase the operable concentration range for forming the microporous structures of the invention and for practicing the methods of the invention. can. From the above, to determine the operable concentration range for a given system,
It is clear that it is only necessary to prepare a small representative concentration of polymer/liquid and cool it at some desired rate. After the crystallization temperature has been plotted, the operable range of concentrations becomes very clear.

FIG. 57 is a graph of temperature versus polymer/liquid concentration for polypropylene and dioctyl phthalate. The upper curve represents the melting curve for the system over a range of concentrations and the lower curve represents the crystallization curve over the same concentration range.

A polypropylene/dioctyl phthalate system capable of forming a microporous structure is not expected, since this crystallization curve does not exhibit any flat portion where the crystallization temperature remains essentially constant for a range of concentrations; And in fact, this is not a formal precept.

Reference is made to Figures 58 and 59 to appreciate the excellent correlation between the phase diagrams that determine the operable concentration ranges of polymers and liquids and the crystallization methods that make this determination. FIG. 58 is a phase diagram for low molecular weight polyethylene and diphenyl ether polymer/liquid systems measured by conventional light scattering techniques using a thermally controlled vessel. From the phase diagram in Figure 58, Tm is about 135°C and φm is about 7
It turns out that it is a multi-polymer. Furthermore, it is apparent that the cloud point curve intersects the freezing point depression curve at about 45% polymer concentration, thus indicating an operational concentration range of about 7% polymer to about 45% polymer. .

．． :? Z The operable range determined from Figure 58 was compared to the melting curve of the same system at 8°C and a heating rate of 16°0/min and 8°C.
and the crystallization curve, which can be compared with the range that can be determined from Figure 59 showing the crystallization curve for the above system at a cooling rate of 16°C/min, shows that its substantially flat portion is slightly less than 10% depending on the cooling rate. It can be seen that the polymer concentration ranges from 42% to 45% polymer. Thus, the results obtained from the crystallization curves are in remarkable agreement with those obtained from the cloud point phase diagram.

For amorphous polymers, reference may be made to a temperature versus concentration plot of the glass transition temperature as an alternative to a phase diagram such as that in FIG. Thus, FIG. 58 shows Piccolastic D at various concentration levels.
125 is a graph of temperature versus concentration versus glass transition temperature of low molecular weight polystyrene and 1-dodecanol supplied by Pennsylvania Industrial Chemical Company under the trade name 125.

It is clear from Figure 58 that the glass transition temperature for polystyrene/1-dodecanol is essentially constant from about 8% polymer to about 50% polymer. It is therefore proposed that concentrations along a substantially flat portion of the glass transition temperature, analogous to the flat portion of the crystallization curve discussed above, are operable in the practice of this invention. Thus, it can be seen that a viable alternative method of determining the phase diagram for amorphous polymeric systems is to determine the glass transition curve and to operate on the substantially flat portion of this curve.

In all of the foregoing figures, crystallization temperatures were measured with a DSC-2, differential scanning calorimeter, or comparable equipment manufactured by PerkinElmer. Further, the effect of cooling rate in the practice of the present invention is discussed below.

After selecting the desired synthetic thermoplastic polymer, compatible liquids, and potentially operable concentration ranges, it is necessary to select, for example, the actual concentrations of the polymers and liquids used. For example, in addition to considering the theoretically possible concentration range, other functional considerations must be made in determining the ratios to be used for a particular system. Thus, as far as the maximum amount of liquid to be used is concerned, the strength properties produced must be taken into account. More particularly, the amount of liquid used should therefore allow the resulting microporous structure to have a sufficient minimum "handling strength" so as to avoid destruction of the microporous or cellular structure. . On the other hand, the selection of the maximum amount of resin, the viscosity limits of the particular equipment used will dictate the maximum allowable polymer or resin content. Furthermore, the amount of polymer used should not be so great as to cause occlusion of cells or other areas of microporosity.

The relative amounts of liquid used depend in part on the desired pore size of the microporous material, such as the particular cell and pore size requirements for the final application involved. Thus, for example, average cell and pore sizes tend to increase slightly as liquid content increases.

Regardless, for a particular polymer, the use of the liquid and its operative concentration can be easily determined by using the liquid experimentally as described.

Of course the parameters discussed above should be followed. Actually, as recognized, two or that J'7? The above formulations can be used; and the use of specific formulations can be determined as described herein. Also, while certain formulations are useful, one or more of the liquids may be individually inappropriate.

As will be appreciated, the particular amount of liquid used will often be dictated by the particular end-use application as well. Using high-density polyethylene and N,N-bis(2-hydroxyethyl)tallowamine, Takaki Reiso's example shows that the amount of aluminum is about 30 to about 90, preferably 3 to 70 A useful microporous product is created by using a microporous material. For low density polyethylene and the same amine, the amount of liquid is between 2 and 90%, preferably 2
It can be usefully varied within a range of 8 to 8 degrees.

In contrast, when diphenyl ether is used as the liquid, useful low density polyethylene systems contain less than about 80% liquid, with a maximum of about 60% preferred. When 1-hexadecene is used with low density polyethylene, amounts up to about 90% or more can readily be used. When polypropylene is used with the tallow amine described above, the amine can suitably be used in an amount of about 1 to 9 parts, with a maximum amount of about 85 parts or less being suitable. For polystyrene and 1-dodecanol, the alcohol concentration varies from about 2 to 90%, from about 30 to about 7
0 steamed rice is suitable. When a styrene-butadiene copolymer is used, the amine content ranges from about 20 to about 90. When decanol and styrene-butadiene copolymer (i.e. -SBR) systems are used, the liquid content can suitably vary from about 40 to about 90%; for diphenylamine the liquid content varies from about 50 to about 80%.
Suitable within % range. When the microporous polymer is formed from an amine and an ethylene-acrylic acid copolymer, the liquid content varies within a range of about 30 to about 7 mm; for diphenyl ether, dibutyl phthalate is used as the solvent. Again, it varies by about 10 to about 90 more.

Homogeneous Liquid Shaping No. 7 Following the formation of the solution, it is then processed to provide any desired shape or structure. Generally, and depending on the particular system involved, the thickness of the articles will vary from thin films of about 1 mil or less to relatively thick blocks of about 21/2 inches or more thick. The ability to form blocks thus allows the D microporous material to be processed into desired complex shapes, for example by conventional extrusion, injection molding or other related techniques. Practical considerations to include in determining the range of thicknesses that can be made from a particular system include the rate of viscosity increase that the system undergoes as it cools. Generally, the higher the viscosity, the thicker the structure.

Therefore, the structure may be of any thickness as long as no coarse phase separation occurs, ie, two distinguishable layers are visible overnight.

It will be appreciated that if liquid-liquid phase separation is allowed to occur under thermodynamic equilibrium conditions, complete separation into two distinct layers will result. One layer is made of molten polymer containing a soluble amount of liquid, and the liquid layer contains a soluble amount of lρ polymer in the liquid. This state is represented by the pinodial line in the state diagram of FIGS. 1 and 1A.

The limits on the dimensions of the objects that can be manufactured are governed by the heat transfer properties of the assembly, because if the object is thick enough and the heat transfer is fairly poor, the rate of cooling applied to the center of the object is thermodynamic. This is clearly because the phase separation is slow enough to reach a state of equilibrium and, as mentioned above, causes phase separation with distinct layers.

With the addition of a small amount of thixochloride material, an increased thickness is obtained. For example, the addition of commercially available colloidal silica before cooling significantly increases the useful thickness, but does not adversely affect the distinctive microporous structure. The specific amount to be used can be easily determined.

Cooling of Homogeneous Solutions It is clear from the above discussion that regardless of the type of processing (e.g., forming into a film, etc.), the solution must be cooled to form something that behaves and appears as a solid. . Is the raw material of sufficient integrity so that it does not shatter when handled by hand? Should have. Another test to confirm whether the required system has the desired structure is to use the solvent for the liquid used rather than for the polymer. If this material decomposes, the system used did not meet the required criteria.

The cooling rate of the solution can be varied within a wide range. In fact, in normal cases, external cooling is not necessary and simply injecting a hot liquid system onto a metal surface heated to a temperature at which the film can be drawn off, for example, or alternatively onto a substrate at ambient conditions. I am satisfied with forming the film by injecting it into ■ and forming a block with it.

As discussed above, the rate of cooling must be fast enough so that liquid-liquid phase separation does not occur under thermodynamic equilibrium conditions. Furthermore, the rate of cooling has a substantial effect on the resulting microporous structure. For many polymer/liquid systems,
If the rate of cooling is slow enough, but still satisfies the above criteria, liquid-liquid phase separation will occur with the formation of multiple droplets of substantially the same size and at substantially the same time. If the cooling rate is such that a large number of droplets ρ are formed, the resulting microporous polymer will have a cellular structure as defined above, provided all other conditions discussed above are satisfied. It has a microscopic structure.

In general, the unique structure of the microporous polymers of the present invention can be obtained by cooling the liquid system to a temperature below the pinozoal curve, as shown in Figure 1, to initiate liquid-liquid phase separation. Seem. In this state, a nucleus consisting essentially of pure solvent begins to form. When the rate of cooling is such that fine cell-like structures occur, as each nucleus continues to grow, it becomes surrounded by a polymer-rich zone that increases in thickness as the liquid empties. It seems that it will. As a result, this polymer-rich area resembles a skin or film covering the growing droplet of solvent. As the polymer-rich zone continues to thicken, the diffusion of excess solvent through the skin decreases; and the length of the droplet decreases correspondingly until it effectively stops and the droplet length decreases. The drop has reached its maximum size. At this point, the formation of new nuclei is even more possible than continuous growth of large droplets. However, in order to obtain the precepts of this method, it is necessary that nucleation be initiated by a spinodal decomposition rather than a pinodial decomposition.

Cooling is thus carried out in such a manner as to form a plurality of droplets of substantially the same size in the continuous polymer phase at substantially the same time. If this decomposition method does not occur, no cell-like structures are generated. A suitable decomposition regime is generally obtained by using conditions that ensure that the system does not reach thermodynamic equilibrium at least at the point where nucleation or droplet growth begins. Methodologically, this is accomplished by simply allowing the system to cool without applying any mixing or other shear forces to the system. The time parameter becomes even more important when relatively thick blocks are being formed, in which case even more rapid cooling is desirable.

To the extent that cooling results in the formation of multiple droplets, there is a general indication that the rate of cooling will affect the size of the cells produced; increasing the rate of cooling will result in smaller cells. . In this context, it has been observed that increasing the cooling rate from about 8°C/min clearly results in a reduction in cell size by half for polypropylene microporous polymers. Therefore, external cooling can be used, if desired, to adjust the final cell and pore dimensions, as discussed in further detail.

Claims (3)

[Claims] (1) Polystyrene, polyvinyl chloride, acrylonitrile-butadiene-styrene terpolymer, styrene-acrylonitrile copolymer, styrene-ptadiene copolymer, poly(4-methyl-pentene-1), polybutylene,
From the group consisting of polyvinylidene chloride, polyvinyl butyral, polyvinyl acetate, polyvinyl alcohol, polymethyl-methacrylate, polymethyl-acrylate, polyphenylene oxide, polyethylene terephthalate, polybutylene terephthalate, nylon 6, nylon 11, nylon 13, nylon 66, polycarbonate and polysulfone 100 parts of a mixture of 90 to 10 parts of one or more selected synthetic thermoplastic polymers and 10 to 90 parts of a compatible liquid were heated to 150°C to 300°C to obtain a homogeneous monolayer solution. followed by cooling under substantially shear-free conditions to allow the simultaneous formation of substantially equally sized droplets of compatible liquids in the continuous phase of liquid polymer and cooling until a solid is formed. and then removing at least a substantial portion of the compatible liquid from the solid produced. 2. The method of claim 1, wherein the mixture is heated to a temperature near or above the softening temperature of the synthetic thermoplastic polymer to form a solution. (3) The method of claim 1 or claim 2, wherein the cooling is performed at a rate such that substantially uniformly sized droplets of compatible liquid are formed in the continuous phase of liquid polymer. .