JP2008248181A - Porous film having hydrophilic graft polymer, method for using the same and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a porous film usable for various applications, by suitably modifying the surface of the porous film, and a method for producing the same. <P>SOLUTION: The porous film 12 having a large number of pores 18 formed therein and a hydrophilic graft polymer 14 on surfaces of the pores is provided. Preferably, the porous film is produced by a process comprising a step of forming a film of an organic solvent solution by applying an organic solvent and the organic solvent solution containing a polymer compound, a step of forming the porous film in which holes are formed where droplets are vaporized by forming the droplets in the film of the organic solvent solution and vaporizing the organic solvent in the film and the droplets and a step of applying the hydrophilic graft polymer on the surface of the porous film. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a porous film having a hydrophilic graft polymer, a method for using the same, and a method for producing the same, and more particularly to a porous film that can be applied to various applications.

  In recent years, in the fields of optical materials and electronic materials, there are increasing demands for improving the degree of integration, increasing the amount of information, and increasing the definition of image information. For this reason, it is sometimes required that a fine structure (fine patterning, fine pattern structure, etc.) is also formed in the film used in each field as described above.

  Various methods such as vapor deposition using a mask, photochemical reaction, photolithographic technique using a polymerization reaction, laser ablation technique, etc. are known and put into practical use for fine patterning of a film. Further, for example, as a method for forming fine patterning on a polarizing plate that is an optical material, there is a method in which a plate (stamper) having a fine structure is produced by a micro processing technique and the fine structure of the plate is transferred to a resin substrate. (See Patent Document 1).

  However, in the so-called top-down method, in which the fine structure of the plate is transferred to the substrate as described above, the production of the plate for determining the fine structure is complicated, requiring many steps, resulting in high costs. End up. There is also a problem that it is difficult to produce a large-area plate.

  On the other hand, a bottom-up method has been proposed in which a self-organized structure having a fine structure is formed by applying a self-organization having a regular fine structure by forming a fine structure in a self-associative manner. For example, there is a method of obtaining a film (honeycomb structure film) having a structure in which micron-scale fine holes are regularly arranged in a honeycomb shape through a process of casting a dilute polymer solution on a support under high humidity. Are known. Such a honeycomb structure film can be manufactured relatively easily by self-organization, and the manufacturing cost can be kept low. For example, in the field of regenerative medicine, such a honeycomb structure film has been proposed to be used as a base material serving as a scaffold in surface cell culture (see Patent Documents 2 to 4).

  However, in the case of a porous film, since it has a large number of pores, there is a problem that its use is limited depending on the material and structure of the film in addition to the problem that the strength is weak and the handling property is poor. For example, a porous film in which a large number of pores are formed in a honeycomb shape as described above has a large actual surface area per unit area of the film due to its structure, and thus tends to be repelled against a liquid having a high surface tension. For this reason, it is difficult to uniformly fill the pores with a substance, which is particularly noticeable in a film having a small pore diameter, and there is a problem that a defect in quality is likely to occur.

  Such a problem can be improved to some extent by a known vapor phase surface oxidation method such as UV ozone treatment (Non-Patent Document 1). However, in this method, since the film itself is oxidatively decomposed, the structure of the film is destroyed, and the original function of the porous film may be impaired. Moreover, in the film surface-treated by the vapor phase surface oxidation method, there is also a problem that the surface of the film gradually changes in quality and the effect becomes small.

JP 2003-302532 A JP 2001-157574 A JP 2002-335949 A JP 2002-347107 A M Shimomura et al, Colloids and Surfaces A, 284-285 (2006) P.301.

  In view of the above problems, the main object of the present invention is to provide a porous film that can be used for various applications by appropriately modifying the surface of the porous film.

  In order to achieve the above object, the present invention provides the following porous film and the like.

<1> A porous film having a hydrophilic surface in which a large number of pores are formed and a hydrophilic graft polymer chain is chemically bonded to the surface.

<2> The porous film according to <1>, wherein the hydrophilic graft polymer chain has a hydrophilic functional group.

<3> The hydrophilic functional group is a nonionic hydrophilic group selected from a hydrophilic functional group having an N-monoalkyl-substituted structure and a hydrophilic functional group having an N-dialkyl-substituted amide group. The porous film according to <2>.

<4> The porous film according to any one of <1> to <3>, wherein the holes are regularly arranged.

<5> The porous film as described in <4>, wherein the pores are formed so that pores having a pore diameter of 0.01 μm to 100 μm communicate with each other.

<6> The average opening diameter that appears on the surface of the film of the holes formed so as to communicate with each other is larger than the average opening diameter of the communication portion between adjacent holes. Porous film.

<7> The porous film according to any one of <2> to <6>, wherein the ratio of the number of hydrophilic groups and the number of carbon atoms constituting the graft polymer is between 0.05 and 0.35. .

<8> The hydrophilic surface formed by chemically bonding the hydrophilic graft polymer chains of the porous film has a water contact angle of 2 to 40 degrees on the surface in an environment of 25 ° C. and 60% RH. The porous film according to any one of <1> to <7>, wherein

<9> The porous film according to any one of <1> to <8>, wherein the graft polymer has a weight average molecular weight of 10,000 to 5,000,000.

<10> The porous film substrate is formed by casting a liquid containing an organic solvent and a polymer compound on a support to form a film, and forming pores in the film. <1> to the porous film according to any one of <9>.

<11> The porous film contains a polymerization initiator, and after contacting with an unsaturated compound having a hydrophilic group capable of radical polymerization, is irradiated with radiation of an arbitrary pattern. The porous film according to any one of <1> to <10>, which has a hydrophilic surface in which a hydrophilic graft polymer chemically bonded on the surface is formed in a pattern.

<12> The porous film according to any one of <1> to <11>, the retardation film, the polarizing film, the screen, the color filter, the display member, the cell culture member, the wound protective film, and the transdermal drug. A method for using a porous film, characterized by being used as a membrane, an acoustic vibration material, a sound absorbing material, or a vibration damping material.

<13> An organic solvent solution containing an organic solvent and a polymer compound is provided on a support to form a film of the organic solvent solution;
By forming droplets in the film of the organic solvent solution and evaporating the organic solvent and the droplets in the film, a porous film having pores formed in the portions where the droplets are evaporated is produced. Process,
Providing a hydrophilic graft polymer on the surface of the porous film, and a method for producing the porous film.

  According to the present invention, there is provided a porous film or the like that can be used for various purposes by selecting a hydrophilic graft polymer without being limited by the material and structure constituting the film substrate.

  Hereinafter, a porous film and a method for producing the same according to the present invention will be specifically described with reference to the accompanying drawings.

  FIG. 1 schematically shows an example of the structure of a porous film according to the present invention. A number of holes 18 are formed in the porous film 12 on the support 16, and a hydrophilic graft polymer 14 is provided on the surface of the film 12 including the inside of each hole 18. Thus, if it is the porous film 12 which has the hydrophilic graft polymer 14 on the surface, it can be set as the porous film suitable for a use by selection of the hydrophilic graft polymer 14. FIG. Further, such a porous film 12 has a strength higher than that of a normal porous film having no hydrophilic graft polymer on the surface, and is a porous film excellent in handleability.

<Porous substrate>
The porous film before the hydrophilic graft polymer is provided (in the present invention, sometimes referred to as “porous substrate” or “pre-porous film”) is made of an organic material and has a large number of pores. If it is a film of this, it will not specifically limit, What is necessary is just to select according to the objective.
The porous substrate before providing such a hydrophilic graft polymer is, for example, a method in which a wire-like or filament-like material is knitted or woven at a high density to form a sheet-like woven or knitted fabric, and a fiber assembly is made of fibers. A method for forming a non-woven fabric type by entanglement, fusion, or binder, a method for forming a porous film or a porous sheet by forming a continuous pore structure by foaming or pressure foaming in a resin material, etc., a polymer compound It is produced by a method of forming a porous film in which a communication hole or a through hole is formed by applying an organic solvent solution containing a solution on a support by casting or the like, a method of punching by a method such as punching, and the like to obtain a porous film can do.

In the present invention, the porous substrate produced by the various methods as described above can be used. However, the porous film has a structure in which the pores are regularly arranged, particularly in a honeycomb shape (honeycomb structure). (Referred to as “honeycomb structure film” in the present invention).
2A to 2C schematically show an example of the honeycomb structure film. Specifically, the honeycomb structure in the present invention means a structure in which pores 18 having a substantially constant shape and size are continuously and regularly arranged as shown in FIG. 2A. Such an arrangement of the regular holes 18 is two-dimensional in the case of a single layer, and may be regular in three dimensions in the case of a multilayer. This regularity is two-dimensionally arranged so that a plurality of (for example, six) vacancies surround one vacancy, and three-dimensionally like a face-centered cubic or hexagonal crystal structure. In many cases, the holes are arranged like close-packed packing, but other regularity may be exhibited depending on the manufacturing conditions.

  An opening portion of each hole 18 appears on the surface of the porous film 12 having such a honeycomb structure. In the present invention, the diameter of the opening portion is referred to as an opening diameter. The regularity of the honeycomb structure can be evaluated relatively simply by using the variation coefficient of the opening diameter of the holes 18. Usually, the smaller the coefficient of variation is, the higher the mechanical strength of the porous film is, and the coefficient of variation in the honeycomb structure film according to the present invention is preferably 20% or less, more preferably 10% or less. More preferably, it is 5% or less.

As a method for producing a porous film (porous substrate) 12 in which holes 18 are regularly arranged as shown in FIGS. 2A to 2C and providing a graft polymer on the surface thereof, for example, as shown in FIG. Such a manufacturing process can be employed.
First, in the casting step 20, a raw material solution is cast on a support to form a liquid film (polymer film). Next, in the condensation drying step 22, moisture in the atmosphere is condensed to form droplets in the polymer film. The condensation drying step 22 will be described in detail later. After the droplet formation, the solvent and the droplet in the polymer solution film on the support are sequentially evaporated. Thereby, the porous base material (pre-porous film) 24 in which pores are formed in the portion where the droplets are evaporated can be obtained.

  According to such a casting method, by adjusting various conditions such as the raw material such as resin, solvent, and additive contained in the polymer solution, the humidity in the film formation atmosphere, and the supply conditions of the humid air, For example, it is possible to obtain a porous film in which communication holes having a honeycomb shape or an arbitrary shape are formed. In addition, for example, a porous film having a so-called three-dimensional network void can be manufactured without requiring a complicated process, not only as a through-hole but also in communication with an adjacent peripheral hole.

  Next, in the surface grafting step 26, a hydrophilic graft polymer according to the purpose is provided on the surface of the porous substrate obtained as described above. Thereby, the porous film (surface grafted porous film) 28 in which the target graft polymer is formed on the surface can be obtained. If necessary, a stretching step may be added either before or after the surface grafting step 26. For example, the irradiation step 30 is performed after the casting step 20 until the surface grafted porous film 28 is obtained. It can also be added. In the irradiation step 30, ultraviolet rays or electron beams can be used as irradiation light.

  Hereinafter, a method for producing a porous substrate by a casting method and providing a graft polymer on the surface of the obtained porous substrate will be described more specifically.

[Preparation of pre-porous film]
An organic solvent solution containing an organic solvent and a polymer compound is applied onto a support to form a liquid film of the organic solvent solution. Next, droplets are formed in the film of the organic solvent solution obtained on the support, and the organic solvent and the droplets in the film are evaporated. As a result, a porous film having pores formed in the portion where the droplets have evaporated is produced.

<Film raw material>
The raw material (polymer compound, etc.) of the porous film before the graft polymer is provided may be appropriately selected according to the purpose. For example, a hydrophobic base polymer can be suitably used.

The base polymer here refers to a polymer that can form a self-supporting film by a casting method.
The base polymer is not particularly limited as long as it is a polymer that is soluble in a water-insoluble solvent, and can be appropriately selected from known ones according to the purpose. For example, a vinyl polymer (for example, polyethylene, polypropylene, polystyrene, polyacrylate, polymethacrylate, polyacrylamide, polymethacrylamide, polyvinyl chloride, polyvinylidene chloride, polyvinylidene fluoride, polyhexafluoropropene, polyvinyl ether, polyvinyl carbazole, Polyvinyl acetate, polyvinyl carbazole, polytetrafluoroethylene, etc.), polyester (eg, polyethylene terephthalate, polyethylene naphthalate, polyethylene succinate, polybutylene succinate, polylactic acid, etc.), polylactone (eg, polycaprolactone, etc.), polyamide or polyimide (For example, nylon or polyamic acid), polyurethane, polyurea, polycarbonate, poly Examples include romantics, polysulfone, polyethersulfone, polysiloxane derivatives, and cellulose derivatives (for example, cellulose acylate and cellulose nitrate). From the viewpoints of solubility, optical physical properties, electrical physical properties, film strength, elasticity, etc., these may be homopolymers as necessary, or may take the form of copolymers or polymer blends. In addition, you may use these polymers as a mixture of 2 or more types of polymers as needed.

A honeycomb structure film can be formed by using only the base polymer, but it is preferable to use an amphiphilic compound together with the base polymer. There is no restriction | limiting in particular as said amphiphilic compound, According to the objective, it can select suitably. For example, amphiphilic polymers can be used.
The amphiphilic polymer may be appropriately selected according to the purpose, for example, polyacrylamide as a main chain skeleton, an amphiphilic polymer having both a dodecyl group as a hydrophobic side chain and a carboxyl group as a hydrophilic side chain, Examples include polyethylene glycol / polypropylene glycol block copolymers.

  The hydrophobic side chain is a non-polar linear group such as an alkylene group or a phenylene group, and has a hydrophilic group such as a polar group or an ionic dissociation group up to the terminal except for a linking group such as an ester group or an amide group. It is preferable that the structure does not branch. As the hydrophobic side chain, for example, when an alkylene group is used, it is preferably composed of 5 or more methylene units.

  The hydrophilic side chain preferably has a structure having a polar part, an ionic dissociation group, or a hydrophilic part such as an oxyethylene group at the end via a linking part such as an alkylene group.

  As the amphiphilic compound, those other than the amphiphilic polymer can also be used. The amphiphilic compound other than the amphiphilic polymer can be appropriately selected according to the purpose. For example, a surfactant is preferable.

  Although there is no restriction | limiting in particular as said surfactant, For example, the compound etc. which are represented with general formula (I) are mentioned.

However, In the general formula (I), R ₁ represents an aliphatic group, an alicyclic compound group, an aromatic group, and represents one of the heterocyclic ring, R ₂ is an aliphatic group, an alicyclic compound group, an aromatic Represents any of a group, a heterocycle, and -LZ. Q ₁ , Q ₂ , and Q ₃ each represent a single bond, an oxygen atom, a sulfur atom, and —N (R ₃ ) —, R ₃ represents either a hydrogen atom or R ₂ , and L is A divalent linking group is represented, and Z represents an ionic group. Note that a single bond means that no element is present.

In the general formula (I), examples of the aliphatic group represented by R ₁ include a linear or branched unsubstituted alkyl group having 1 to 40 carbon atoms, and a linear or branched carbon number of 1 to 40. Substituted alkyl groups, linear or branched unsubstituted alkenyl groups having 2 to 40 carbon atoms, linear or branched substituted alkenyl groups having 2 to 40 carbon atoms, linear or branched carbon atoms having 2 to 40 carbon atoms An unsubstituted alkynyl group, a linear or branched substituted alkynyl group having 2 to 40 carbon atoms, and the like are preferable.

In the general formula (I), examples of the alicyclic compound group represented by R ₁ include a substituted or unsubstituted cycloalkyl group having 3 to 40 carbon atoms, and a substituted or unsubstituted carbon group having 4 to 40 carbon atoms. A cycloalkenyl group and the like are preferable.
As the aromatic group, for example, a substituted or unsubstituted aryl group having 6 to 50 carbon atoms is preferable.

  In the general formula (I), the heterocyclic ring is preferably a substituted or unsubstituted cyclic ether having 4 to 40 carbon atoms, a substituted or unsubstituted nitrogen containing ring having 4 to 40 carbon atoms, and the like.

  Among these, a linear, cyclic, or branched unsubstituted alkyl group having 1 to 24 carbon atoms, a linear, cyclic, or branched chain having 1 to 24 carbon atoms excluding the carbon number of the substituent. A substituted alkyl group, a linear, cyclic, or branched unsubstituted alkenyl group having 2 to 24 carbon atoms, a linear, cyclic, or branched substituted alkenyl group having 2 to 24 carbon atoms, a carbon number of 6 to 30 Particularly preferred are substituted or unsubstituted aryl groups.

In the general formula (I), Q ₁ , Q ₂ , and Q ₃ are preferably a single bond, an oxygen atom, or —N (R ₃ ) —, and at least of Q ₁ , Q ₂ , and Q ₃ It is particularly preferable that two or more are oxygen atoms.

  In the general formula (I), L is preferably a group represented by the following general formula (II).

However, in said general formula (II), Y < ₁ >, Y < ₂ > and Y < ₃ > may be the same or different, respectively, a C1-C40 substituted or unsubstituted alkylene group, and carbon number It represents either 6-40 substituted or unsubstituted arylene groups. J ₁ , J ₂ , and J ₃ each represent a divalent binding unit that may be the same or different. p, q, and r each independently represents an integer of 0 to 5. s represents an integer of 1 to 10. a and b each independently represents an integer of 0 to 50.

Examples of the substituent in Y ₁ , Y ₂ , and Y ₃ include the groups exemplified for R ₁ in the general formula (I). Specifically, for example, as an alkylene group, methylene group, ethylene group, propylene group, trimethylene group, tetramethylene group, pentamethylene group, hexamethylene group, 1,4-cyclohexylene group, octamethylene group, decamethylene group 2-methoxy-1,3-propylene group and the like are preferable, and as the arylene group, o-phenylene group, m-phenylene group, p-phenylene group, 3-chloro-1,4-phenylene group, 1,4- A naphthylene group, a 1,5-naphthylene group and the like are preferable. Among these, ethylene group, propylene group, trimethylene group, tetramethylene group, pentamethylene group, hexamethylene group, 1,4-cyclohexylene group, octamethylene group, decamethylene group, m-phenylene group, p-phenylene group are included. Particularly preferred.

Examples of the divalent linking unit in J ₁ , J ₂ , and J ₃ include a single bond, —O—, —S—, —CO—, —COO—, —OCO—, and —CON (R ₄ ). _{-, - N (R 4)} CO -, - CON (R 4) CO -, - N (R 4) CON (R 5) -, - OCON (R 4) -, - N (R 4) COO-, _{-SO 2 -, - SO 2 N} (R 4) -, - N (R 4) SO 2 -, - N (COR 4) -, - OP (= O) (OR 1) O- , and the like are preferable. In these, R ₁ represents the same meaning as in the general formula (I), and R ₄ represents a hydrogen atom, an unsubstituted alkyl group having 1 to 6 carbon atoms, and a carbon number excluding the carbon number of the substituent. Represents any one of 1 to 6 substituted alkyl groups, and R ₅ represents the same meaning as R ₄ , but may be the same or different. Examples of the substituent in R ₄ and R ₅ include an aryl group, an alkoxyl group, and a halogen atom.
Among these, a single bond, —O—, —S—, —CO—, —COO—, —OCO—, —CON (R ₃ ) — (R ₃ represents a hydrogen atom, a methyl group, an ethyl group, or a propyl group) Represents a group), —N (R ₄ ) CO—, —SO ₂ N (R ₄ ) —, —N (R ₄ ) SO ₂ — and the like are particularly preferable.

  As said p, q, and r, the integer of 0-3 is preferable each independently, and the integer of 0 or 1 is especially preferable. As said s, the integer of 1-5 is preferable and the integer of 1-3 is especially preferable. As said a and b, the integer of 0-20 is preferable each independently, and the integer of 0-10 is especially preferable.

In the general formula (I), Z is preferably a hydrophilic anionic or cationic ionic group, particularly preferably an anionic group.
As the anionic group, —COOM, —SO ₃ M, —OSO ₃ M, —PO (OM) ₂ —OPO (OM) ₂ are particularly preferable. The M represents a counter cation, and is any one of an alkali metal ion (for example, lithium ion, sodium ion, potassium ion, etc.), an alkaline earth metal ion (for example, magnesium ion, calcium ion, etc.), and an ammonium ion. Is preferred. Among these, sodium ion and potassium ion are particularly preferable.
The cationic group, for ^{_{example, -NH 3 + · X -,}} -NH 2 (R 6) + · -, -NH (R 6) 2 + · X -, -N (R 6) 3 + · X ^- .
R ₆ represents an alkyl group having 1 to 3 carbon atoms (for example, methyl group, ethyl group, 2-hydroxyethyl group, n-propyl group, iso-propyl group, etc.), methyl group, 2-hydroxyethyl Groups are preferred.
X represents a counter anion, for example, a halogen ion (for example, fluorine ion, chlorine ion, bromine ion, etc.), a composite inorganic anion (for example, hydroxide ion, sulfate ion, nitrate ion, phosphate ion, etc.), And an organic compound anion (for example, oxalate ion, formate ion, acetate ion, propionate ion, methanesulfonate ion, p-toluenesulfonate ion, etc.), particularly chloride ion, sulfate ion, nitrate ion, acetate ion preferable.

In the general formula (I), examples of R ₂ include a monovalent group selected from the groups exemplified for R ₁ and the groups exemplified for the above-LZ. When selected from the groups exemplified for R ₁ , it may be the same structure as or different from R ₁ existing in the same molecule. In addition, when selected from the groups exemplified as -LZ, the structure may be the same as or different from -LZ existing in the same molecule. Among these, the case where it is selected from the groups exemplified for R ₁ is particularly preferable. Furthermore, the total number of carbon atoms of R ₁ and R ₂ is preferably 6 or more and 80 or less, and particularly preferably 8 or more and 50 or less.

  The ratio between the hydrophobic side chain and the hydrophilic side chain differs depending on the size, nonpolarity, polarity strength, hydrophobicity of the organic solvent, etc. The ratio of (hydrophobic side chain / hydrophilic side chain) is preferably 9.9 / 0.1 to 5.5 / 4.5. Further, in the case of a copolymer, it is a block copolymer in which a hydrophobic side chain and a hydrophilic side chain form a block as long as it does not affect the solubility in an organic solvent, rather than an alternating polymer of hydrophilic side chains of hydrophobic side chains. Preferably there is.

  The weight average molecular weight (Mw) of the base polymer and the amphiphilic compound is preferably 10,000 to 10,000,000, and more preferably 50,000 to 1,000,000. In addition, the value measured by GPC method is employ | adopted for this weight average molecular weight.

The composition ratio (mass ratio) between the base polymer and the amphiphilic compound is preferably 99.9: 0.1 to 50:50 when the amphiphilic compound is an amphiphilic polymer. 95: 5-75: 25 is more preferable. When the ratio of the amphiphilic compound is within the above range, a uniform porous film can be easily obtained, and the stability of the film, particularly the mechanical stability can be sufficiently obtained.
On the other hand, when the amphiphilic compound is not an amphiphilic polymer, the composition ratio (mass ratio) between the base polymer and the amphiphilic compound is preferably 99.9: 0.1 to 80:20. When the ratio of the amphiphilic compound is within this range, a uniform continuous porous film can be obtained and the film strength can be appropriately maintained.
In addition, as an amphiphilic compound, an amphiphilic polymer and an amphiphilic low molecular weight compound may be mixed and used in an arbitrary ratio. Mixing and using an amphiphilic polymer and an amphiphilic low-molecular compound is particularly suitable for providing a film having a pore size of 2 μm or less.

The base polymer and the amphiphilic polymer are also preferably polymerizable or crosslinkable polymers having a polymerizable group in the molecule.
In addition, a polymerizable polyfunctional monomer is blended together with the base polymer and / or the amphiphilic polymer, and a honeycomb structure film is formed from the blend, and then a thermosetting method, an ultraviolet curing method, an electron beam curing method, etc. Curing treatment can also be performed by a known method.

The polyfunctional monomer used in combination with the base polymer and / or the amphiphilic polymer is preferably a polyfunctional (meth) acrylate from the viewpoint of reactivity. Examples of the polyfunctional (meth) acrylate include dipentaerythritol pentaacrylate, dipentaerythritol hexaacrylate, dipentaerythritol caprolactone adduct hexaacrylate or a modified product thereof, epoxy acrylate oligomer, polyester acrylate oligomer, Urethane acrylate oligomer, N-vinyl-2-pyrrolidone, tripropylene glycol diacrylate, polyethylene glycol diacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, or a modified product thereof can be used. These polyfunctional monomers are used singly or in combination of two or more from the balance of scratch resistance and flexibility.
When the base polymer or the amphiphilic polymer is a polymerizable or crosslinkable polymer having a polymerizable group in the molecule, polymerization that can react with the polymerizable group of the base polymer and the amphiphilic polymer It is also preferable to use a polyfunctional monomer in combination.

  Polymerization of the monomer having an ethylenically unsaturated group can be carried out by irradiation with ionizing radiation or heating in the presence of a photo radical initiator or a thermal radical initiator.

Examples of the photo radical polymerization initiator include acetophenones, benzoins, benzophenones, phosphine oxides, ketals, anthraquinones, thioxanthones, azo compounds, peroxides, 2,3-alkyldione compounds, Examples include disulfide compounds, fluoroamine compounds, and aromatic sulfoniums.
Examples of the acetophenones include 2,2-ethoxyacetophenone, p-methylacetophenone, 1-hydroxydimethylphenyl ketone, 1-hydroxycyclohexyl phenyl ketone, 2-methyl-4-methylthio-2-morpholinopropiophenone, 2 -Benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone and the like.
Examples of the benzoins include benzoin benzene sulfonate, benzoin toluene sulfonate, benzoin methyl ether, benzoin ethyl ether, and benzoin isopropyl ether.
Examples of the benzophenones include benzophenone, 2,4-chlorobenzophenone, 4,4-dichlorobenzophenone, p-chlorobenzophenone, and the like.
Examples of the phosphine oxides include 2,4,6-trimethylbenzoyldiphenylphosphine oxide.
Examples of the radical photopolymerization initiator include known ones described in “Latest UV Curing Technology (Issue: Kazuhiro Takasashi, Publisher; Technical Information Association, Inc., 1991) P.159”. Can be used widely.

Further, as a commercially available photocleavable photoradical polymerization initiator, Irgacure (registered trademark) (651, 184, 907) manufactured by Ciba Specialty Chemicals, and the like are preferable examples.
The photopolymerization initiator is preferably used in the range of 0.1 to 15 parts by mass, and more preferably in the range of 1 to 10 parts by mass with respect to 100 parts by mass of the polyfunctional monomer.
In addition to the photopolymerization initiator, a photosensitizer may be used. Specific examples of the photosensitizer include n-butylamine, triethylamine, tri-n-butylphosphine, Michler's ketone, and thioxanthone.

Examples of the thermal radical polymerization initiator that can be used include organic peroxides, inorganic peroxides, organic azo compounds, and organic diazo compounds.
Specific examples of the organic peroxide include benzoyl peroxide, halogen benzoyl peroxide, lauroyl peroxide, acetyl peroxide, dibutyl peroxide, cumene hydroperoxide, and butyl hydroperoxide. Examples of the inorganic peroxide include hydrogen peroxide, ammonium persulfate, and potassium persulfate.
Examples of the azo compound include 2,2′-azobis (isobutyronitrile), 2,2′-azobis (propionitrile), 1,1′-azobis (cyclohexanecarbonitrile), and the like.
Examples of the diazo compound include diazoaminobenzene, p-nitrobenzenediazonium, and the like.

  Such a polymerization initiator is preliminarily contained in the porous film, or is contained in an intermediate layer of the porous film and the hydrophilic graft polymer, and then patterned in any pattern by heat, acid or radiation. It is also effective to form a hydrophilic graft polymer on the surface of the porous film. In this case, in order to prevent the polymerization initiator from eluting into the polymer solution to be contacted in the hydrophilic grafting process, it is desirable that the polymerization initiator is a polymer of a monomer having a functional group having a polymerization initiating ability and a crosslinking group in the side chain. Examples of such a polymerization initiator include compounds described in JP-A No. 2004-175098.

  The polymer concentration of the dissolved base polymer and amphiphilic polymer is preferably 0.02 to 20% by mass, more preferably 0.05 to 10% by mass. When the polymer concentration is within this range, it is easy to produce a hydrophilic porous film having sufficient mechanical strength, and it is easy to control the pore diameter and arrangement.

<Solvent>
When producing a honeycomb structure porous film before the graft polymer is provided by the casting method, it is preferable to use a water-insoluble solvent in order to form fine water droplet particles on the polymer solution cast on the support. Examples of the water-insoluble solvent include fluorine-containing solvents such as hydrofluoroether, perfluorobenzene and dichloropentafluoroethane, halogen-based organic solvents such as chloroform and methylene chloride; aromatic hydrocarbons such as benzene, toluene and xylene. Esters such as ethyl acetate and butyl acetate; water-insoluble ketones such as methyl isobutyl ketone; ethers such as diethyl ether; carbon disulfide; These can also be used individually by 1 type, and can also be used as a mixed solvent which combined these solvents.

<Support>
The support for forming a film by casting the raw material solution (cast solution) of the porous film is not particularly limited as long as it is transparent and has a certain degree of strength, and is appropriately selected according to the purpose. can do. For example, inorganic materials such as glass, metal and silicon wafers; polyesters such as polyethylene terephthalate and polyethylene naphthalate; polyolefins such as polyethylene and polypropylene; polyamides, polyethers, polystyrenes, polyester amides, polycarbonates, polyphenylene sulfides, polyether esters, polys Examples thereof include organic materials having excellent organic solvent resistance such as vinyl chloride, polyacrylic acid ester, polymethacrylic acid ester, polyether ketone, and polyfluorinated ethylene; and liquids such as water, liquid paraffin, and liquid polyether.

  The thickness of the support may be a thickness that can support the liquid film of the raw material solution, and can be appropriately selected according to the material of the support. 0.02-4.0 mm is preferable.

Further, the support has a surface tension gamma _S of the support surface, and the surface tension gamma _L of organic solvent used in the casting liquid, between the surface tension gamma _LS between the support and the solvent, gamma _S It is desirable to select one that satisfies the relationship -γ _LS > γ _L. This is because the wettability of the casting liquid to the support can affect the thickness of the liquid film formed on the support. The support preferably has a high affinity with the organic solvent constituting the casting solution.

  Moreover, the support body which gave the process which improves the affinity with a casting liquid can also be used. Improvement of the wettability of the support surface can be performed by a known method in consideration of the material of the support, the composition of the casting solution, and the like. For example, for glass or metal supports, vapor phase treatment such as UV ozone irradiation treatment or plasma oxidation treatment, or liquid phase treatment such as silane coupling treatment or monomolecular layer formation treatment with a thiol compound, respectively. Can be used.

Next, the procedure for forming a porous film using the above raw material solution will be specifically described.
An organic solvent solution containing the organic solvent and the polymer compound as described above is applied onto the support to form a film of the organic solvent solution (a liquid film of the polymer solution; which becomes the polymer film after the solvent is dried).
For example, a cast solution in which a base polymer is dissolved in an organic solvent, preferably a water-insoluble solvent having a surface tension γ _L of 50 mN / m or less, is used as a surface tension γ _S between the support substrate and the solvent. The substrate is cast on the substrate surface satisfying the relationship of γ _S -γ _LS > γ _L between the surface tensions γ _LS . In addition, as a method of applying an organic solvent solution containing a polymer compound on a support, a known method such as a bar coating method, a dip coating method, or a spin coating method is used in addition to a method of dropping a cast solution onto a supporting substrate. Each of them can be used in both batch and continuous methods.
The film thickness of the raw material solution on the support may be determined according to the use of the porous film to be produced, but is usually 1 μm to 1000 μm, preferably 700 μm or less.

Next, in the condensation drying step, droplets are formed in the film of the organic solvent solution, and then the organic solvent and the droplets in the film are evaporated.
4A to 4C are diagrams for schematically explaining the condensation drying process. As shown in FIG. 4A, by sending wind at a predetermined humidity and temperature onto the polymer film 40 on the support 46, moisture 42 in the wind is condensed on the polymer film 40 to form droplets 44. Become. After the droplets are thus formed on the film 40 by condensation, the organic solvent 48 is volatilized from the polymer film 40 when dry air is sent onto the polymer film 40 as shown in FIG. 4B. At this time, the moisture in the droplets 44 also evaporates, but the volatilization rate of the organic solvent 48 is faster, and the droplets 44 become substantially uniform due to the surface tension as the organic solvent 48 volatilizes. As the drying further proceeds, the droplets 44 in the polymer film 40 volatilize as water vapor 50 as shown in FIG. 4C. When the droplet 44 evaporates from the polymer film 40, a hole is formed at the location where the droplet 44 evaporates. For example, as shown in FIGS. 2A to 2C, a porous material in which a large number of holes 18 are formed in a honeycomb shape. A film 12 is obtained.

  Here, it is desirable to evaporate the water-insoluble solvent in the raw material solution cast on the support substrate 46 in the presence of air having a relative humidity of 30% or more. The evaporation rate of the solvent can be adjusted by developing the liquid film 40 on the support 46 in an air stream containing water vapor having a relative humidity of 30% or more and a wind speed of 0.01 to 20 m / sec. In the case of producing a porous film having through-holes, a liquid film 40 of a water-insoluble solvent solution of a base polymer in an air flow adjusted within a range of a relative humidity of 30 to 99% and a wind speed of 0.01 to 20 m / sec. Is preferably expanded. The direction of setting the air flow with respect to the liquid film 40 is preferably set to a depression angle of 45 ° or less, and a direction having a parallel or elevation angle is more desirable from the viewpoint of preventing distortion and cracking. In this case, the airflow may be generated by either positive pressure from the upstream side or negative pressure from the downstream side. For example, either predetermined air may be ejected from a nozzle installed toward the support 46, or air above the support may be sucked from one direction.

  By evaporating the water-insoluble organic solvent and the droplets from the liquid film 40 spread on the support 46 in this manner, a porous film made of a base polymer and having pores formed in the portions where the droplets were evaporated is obtained. Can be produced. At that time, the pore diameter of the porous film can also be adjusted by adjusting the evaporation rate of the solvent.

  Here, for example, in order to reduce the pore diameter, it is effective to promote rapid drying. For example, it is effective to use a low boiling point solvent as the solvent, raise the support temperature, or increase the casting speed to reduce the initial liquid film thickness.

  The thickness of the honeycomb-shaped porous film of the present invention is preferably 0.1 μm to 1.0 mm. Further, by increasing the concentration of the polymer to be cast, a thick layer without pores 18 can be provided on the support 16 side as shown in FIG. In this case, the thickness of the thick layer without voids is preferably 500 μm or less.

Moreover, although the porous film of this invention is based also on the use, it is good also as a porous film arrange | positioned so that it may generally take the structure where the adjacent void | hole communicated with each other. This is because, as shown in FIG. 2C, if adjacent holes 18 communicate with each other, it can be used as a material permeation path in the surface direction, for example. Although the pore diameter depends on the film thickness and purpose of use, in order to keep the strength of the membrane and the material permeability in the surface direction good, the pores having a pore diameter of 0.01 μm to 100 μm are formed to communicate with each other. It is preferable.
Further, in order to set the material permeation ratio in the thickness direction and the surface direction of the film to a desired value, the ratio of the average opening diameter D of the film surface and the average opening diameter L of the communicating portion between the adjacent holes is controlled. It is desirable. Generally, it is preferable that the average opening diameter D of the opening portions of the holes 18 appearing on the film surface is larger than the average opening diameter L of the communication portions in the surface direction. If such a communication hole 18 is formed, the porous film 12 has sufficient mechanical strength and can control the material permeability in the thickness direction and the surface direction of the film 12.

  The porous film of the present invention may be stretched depending on the purpose. In the case of stretching, the pore diameter (pore diameter) in the film having the honeycomb structure is preferably 50 μm or less, more preferably 100 nm or more and 2000 nm or less. When the hole diameter exceeds 50 μm, the film strength is lowered and the film may be broken. In the case where the stretching treatment is performed, it may be performed before or after the surface grafting step 26, but it is preferable to set it before the surface grafting step 26 in consideration of stretching efficiency and quality.

[Formation of hydrophilic graft polymer]
In the surface grafting step 26, a hydrophilic graft polymer is provided on the surface of the porous film produced as described above.

The hydrophilic graft polymer provided on the surface of the porous film may be selected according to the purpose. For example, when the hydrophilic property of the porous film is to be improved, a graft polymer having a hydrophilic group may be provided. .
The graft polymer according to the present invention may be directly bonded to the surface of the honeycomb structure film, for example, or an intermediate layer to which the graft polymer is easily bonded is provided on the surface of the film, and the graft polymer is bonded to the intermediate layer. May be. Further, a polymer in which a graft polymer chain having a functional group such as a hydrophilic group is bonded to the trunk polymer compound, or a graft polymer chain having a functional group such as a hydrophilic group can be bonded to the trunk polymer compound and crosslinked. Functional polymers such as those provided on the surface of the honeycomb structure porous film by coating or post-coating crosslinking using a polymer having a functional group introduced therein, or hydrophilic groups having a crosslinkable group at the polymer terminal A composition containing a group-containing polymer and a crosslinking agent may be used and disposed on the surface of the honeycomb structure film by coating or crosslinking after coating.

  The graft polymer has a graft portion in which the polymer ends are bonded to the surface of the honeycomb structure film or to an intermediate layer provided on the surface of the honeycomb structure film, and exhibit a characteristic of a functional group such as a hydrophilic group. It is preferable to have a structure that is not substantially crosslinked. With such a structure, the mobility of the polymer portion that exhibits the characteristics of the functional group such as a hydrophilic group is not limited, or the polymer portion is not embedded in a strong crosslinked structure, and high mobility can be maintained. For this reason, compared with the non-graft polymer which has a normal crosslinked structure, performance, such as hydrophilic property by a functional group, can be notably expressed.

The weight average molecular weight of such a graft polymer chain is preferably in the range of 10,000 to 5,000,000, more preferably in the range of 10,000 to 2,000,000, and still more preferably in the range of 20,000 to 1,000,000. The weight average molecular weight mentioned here can be measured by the GPC method using an appropriate hydrophilic solvent system solution after dissolving the porous film with an appropriate organic solvent and isolating the graft portion.
Further, the ratio of the number of hydrophilic groups and the number of carbon atoms constituting the surface graft polymer described later can be measured using the NMR method of the sample collected here.

<Method for forming hydrophilic graft polymer>
As a method of providing a graft polymer having a functional group such as a hydrophilic group on the surface of the honeycomb structure film, particularly the inner surface of each hole, a method of mainly attaching the honeycomb structure film and the graft polymer by chemical bonding (Grafting on) and a method (Grafting from) of polymerizing a compound having a double bond that can be polymerized from the honeycomb structure film as a base point.

First, a method (Grafting on) of bonding the honeycomb structure film and the graft polymer by chemical bonding will be described. In this method, a polymer having a functional group that reacts with the substrate at the terminal or side chain of the polymer is used, and the functional group can be grafted by chemically reacting with the functional group on the surface of the honeycomb structure film. . The functional group of the graft polymer that reacts with the functional group on the surface of the honeycomb structure film is not particularly limited as long as the reaction occurs. For example, a silane coupling group such as alkoxysilane, an isocyanate group, an amino group Hydrophilic groups such as hydroxyl group, carboxyl group, sulfonic acid group, phosphoric acid group, epoxy group, allyl group, methacryloyl group, acryloyl group, hydrophobic group such as phenyl group, isopropyl group, tert-butyl group, trimethylamine group, thiol And a coloring group such as azobenzene and anthracene. Particularly useful compounds as a polymer having a reactive functional group at the polymer terminal or side chain are a hydrophilic polymer having a trialkoxysilyl group at the polymer terminal, a hydrophilic polymer having an amino group at the polymer terminal, and a carboxyl group at the polymer terminal. A hydrophilic polymer having an epoxy group at the polymer terminal, and a hydrophilic polymer having an isocyanate group at the polymer terminal.
In addition, the polymer used at this time is not particularly limited. Specifically, polyacrylic acid, polymethacrylic acid, polystyrene sulfonic acid, poly-2-acrylamido-2-methylpropane sulfonic acid, and salts thereof. , Polyacrylamide, polyvinylacetamide and the like. In addition, a polymer or copolymer used in the surface graft polymerization described later can be advantageously used.

  On the other hand, a method (Grafting from) of forming a graft polymer by polymerizing a compound having a double bond that can be polymerized based on the honeycomb structure film is generally referred to as surface graft polymerization. Specifically, the surface graft polymerization method is such that active species are provided on the surface of the honeycomb-shaped porous film by a method such as plasma irradiation, light irradiation, and heating, and further arranged so as to be in contact with the surface of the honeycomb-shaped porous film. It refers to a method in which a compound having a polymerizable double bond is bonded by polymerization.

  As the surface graft polymerization method in the present invention, for example, any of the known methods described in the following documents can be used. For example, “New Polymer Experiments 10 (Kyoritsu Shuppan Co., Ltd., edited by Polymer Society, published in 1994) P.135” describes surface grafting methods such as photograft polymerization and plasma irradiation graft polymerization. ing. Further, “Adsorption Technology Handbook (NTS Co., Ltd., supervised by Takeuchi, published in 1999) P.203 and P.695” describes a radiation-induced graft polymerization method such as γ-rays and electron beams.

  As a specific method of the photograft polymerization method, for example, methods described in JP-A-63-92658, JP-A-10-296895, JP-A-11-119413 and the like can be used. In addition to the above-mentioned documents, photograft polymerization is performed by applying a photopolymerizable composition to the film surface as described in JP-A-53-17407 and JP-A-2000-212313, It can also be carried out by bringing a radical polymerization compound into contact and irradiating light.

  For the plasma irradiation graft polymerization method and the radiation irradiation graft polymerization method, the methods described in the above-mentioned literature and “Y. Ikada et al, Macromolecules, 19 (1986) P. 1804” can be applied. Specifically, the surface of the honeycomb-like porous film is treated with plasma or electron beam to generate radicals on the surface, and then the graft polymer surface layer is formed by reacting the active surface with a monomer having a functional group. Obtainable.

-Compounds having polymerizable double bonds useful for surface graft polymerization-
As a compound useful for forming a hydrophilic graft polymer chain in the present invention, it is necessary to have a polymerizable double bond and to have a functional group giving desired performance. As such a compound, a polymer, an oligomer, a monomer, or a mixture thereof can be used as long as it has a double bond in the molecule. Particularly useful compounds are monomers.
Monomers useful in the present invention include positively charged monomers such as ammonium and phosphonium, negative charges such as sulfonic acid groups, carboxyl groups, phosphate groups, and phosphonic acid groups, or negatively charged ions. Monomers having an acidic group that can be dissociated may be mentioned. For example, monomers having a nonionic group such as a hydroxyl group, an amide group, a sulfonamide group, an alkoxy group, or a cyano group may be used. From the viewpoint of high hydrophilicity and abrasion resistance, the hydrophilic group of the hydrophilic graft polymer chain includes a hydrophilic group having an N-monoalkyl-substituted structure and a hydrophilic group having an N-dialkyl-substituted amide group. The nonionic hydrophilic group selected is desirable.

  Specific examples of the monomer particularly useful in the present invention include the following monomers. For example, (meth) acrylic acid or its alkali metal salt and amine salt, itaconic acid or its alkali metal salt and amine salt, allylamine or its hydrohalide salt, 3-vinylpropionic acid or its alkali metal salt and amine salt Vinyl sulfonic acid or its alkali metal salt and amine salt, styrene sulfonic acid or its alkali metal salt and amine salt, 2-sulfoethylene (meth) acrylate, 3-sulfopropylene (meth) acrylate or its alkali metal salt and amine salt 2-acrylamido-2-methylpropanesulfonic acid or alkali metal salts and amine salts thereof, acid phosphooxypropylene glycol mono (meth) acrylate or salts thereof, 2-dimethylaminoethyl (Meth) acrylate or its hydrohalide, 3-trimethylammoniumpropyl (meth) acrylate, 3-trimethylammoniumpropyl (meth) acrylamide, N, N, N-trimethyl-N- (2-hydroxy-3-methacryloyl Oxypropyl) ammonium chloride and the like can be used. Also useful are 2-hydroxyethyl (meth) acrylate, (meth) acrylamide, N-monomethylol (meth) acrylamide, N-vinylpyrrolidone, N-vinylacetamide, propylene glycol mono (meth) acrylate and the like.

  In the present invention, a hydrophilic graft polymer chain is formed on the surface including the inner surface of each hole of the porous film using the above-described monomer or the like. We have studied earnestly. As a result, for example, when the hydrophilicity of the surface of the porous film is improved by the graft polymer, the ratio of the number of hydrophilic groups to the number of carbons constituting the surface graft polymer (number of hydrophilic groups / carbon number) is 0.05 to 0.00. It has been found that the configuration of 35 is particularly preferable. In addition, the hydrophilic group here has a positive charge such as ammonium and phosphonium in addition to a hydroxyl group, or a negative charge such as a sulfonic acid group, a carboxyl group, a phosphoric acid group, and a phosphonic acid group, Contains acidic groups that can dissociate into negatively charged ions.

  In addition, the present inventors have found that the configuration in which the weight average molecular weight of the surface graft polymer is 10,000 or more and 5,000,000 or less as described above is particularly preferable. The weight average molecular weight of the surface graft polymer here is a value measured by GPC method using a solution of an appropriate hydrophilic solvent system after dissolving the porous film with an appropriate organic solvent and isolating the graft portion. It is.

  When the surface graft polymer satisfies the above conditions, in addition to the hydrophilicity of the porous film surface, control over the material permeation in the thickness direction and the surface direction of the porous film can be achieved through structural defects and strength of the film. It can be utilized without causing the above problems, and the porous film can be applied to more applications.

  As described above, a surface hydrophilic layer fixed by a chemical bond in which a hydrophilic graft polymer chain is present can be provided on the surface including the inside of the pores of the porous film. The thickness of the hydrophilic surface layer by the hydrophilic graft polymer can be arbitrarily selected according to the purpose, but generally it is preferably in the range of 0.001 μm to 10 μm, and more preferably in the range of 0.01 μm to 5 μm. .

The introduction amount (graft ratio) of the desirable hydrophilic graft polymer chain of the present invention is in the range of 1 to 300% by weight, although it depends on the intended use of the resulting porous film. 150%. Here, the graft ratio is a weight ratio of the hydrophilic graft polymer to the polymer constituting the preporous film before the hydrophilic graft treatment, and is represented by the following formula.
Graft rate (%) = [(weight of porous film after hydrophilic grafting) − (weight of preporous film before hydrophilic grafting)] / (weight of preporous film before hydrophilic grafting) × 100

  The hydrophilic surface formed by chemically bonding the hydrophilic graft polymer chains of the porous film has a water contact angle of 2 to 40 degrees on the surface in an environment of 25 ° C. and 60% RH. It is preferable. If the water contact angle on the surface where the graft polymer is formed is within the above range, the hydrophilicity can be greatly improved.

  The porous film of the present invention may be used as it is by first producing it on a desired support or a release layer provided on the support, or after being immersed in an appropriate solvent such as ethanol. After peeling from the support, it may be used on another desired support. In the case of use after peeling, an adhesive such as an epoxy resin or a silane coupling agent suitable for the material and the material of the desired substrate may be used for the purpose of improving the adhesion to a new substrate.

  The porous film according to the present invention produced as described above has a hydrophilic graft polymer on the surface including the inside of each hole. For example, if it has a graft polymer with hydrophilic groups introduced at a certain ratio, the wettability of the porous film will be improved continuously, uniform surface modification treatment with the liquid phase, and the substance filling property to the pores , A porous film having excellent supportability and the like can be obtained. Furthermore, if the opening diameter of the communication part between adjacent holes is controlled, the distribution ratio of mass transfer between the thickness direction and the surface direction of the film can be changed. Therefore, the porous film according to the present invention includes, for example, a retardation film, a polarizing film, a screen, a color filter, a display member, a cell culture member, a wound protective film, a percutaneous absorption drug film, an acoustic vibration material, a sound absorbing material, and the like. It can be applied to various uses such as materials and vibration damping materials, and becomes a porous film having performance suitable for the use. For example, it is possible to smoothly and uniformly perform surface modification using a liquid phase and filling of pores with a substance, and it is possible to provide a porous film having performance suitable for high-quality applications.

  Examples of the present invention will be described below, but the present invention is not limited to the following examples.

<Example 1>
-Preparation of pre-porous film-
A polycaprolactone having a weight average molecular weight of 60,000, an amphiphilic polymer (A) represented by the following structural formula and having a weight average molecular weight of 50,000 and a low molecular weight surfactant (B) in a mass ratio of 100: 10: 0.5 mL of methylene chloride solution (0.4% by mass as polymer concentration) mixed at a ratio of 1 was prepared.

  Next, the entire amount of the methylene chloride solution was cast on a glass substrate for HDD kept at 1 ° C. in a closed space not affected by outside air. A pre-porous film (porous) is obtained by blowing constant-humidity air with a relative humidity of 60% at a constant flow rate of 2 L / min from the direction of a depression angle of 30 ° with respect to the support (glass substrate) surface and evaporating methylene chloride. Substrate) was obtained. Here, constant humidity air is supplied by connecting a humidity generator manufactured by Yamato Scientific Co., Ltd. to a compressor SC-820 manufactured by Hitachi Koki Co., Ltd., which has a commercially available dust removal air filter (filtration degree: 0.3 μm). did. In addition, it was 0.3 m / s when the flow velocity of the air of a spraying part was measured.

  When the structure of the obtained film was observed with a field emission scanning electron microscope (manufactured by Hitachi High-Technology Corporation, S4300), a honeycomb-like porous material in which pores having a pore diameter of 0.9 μm were regularly arranged in a hexagonal shape. The structure was confirmed. The distance between the centers of adjacent vacancies was approximately 1.3 μm. Each hole formed a single layer from the front surface to the back surface of the film, and had a structure penetrating in the thickness direction of the film. In addition, the vacancies were distributed over almost the entire surface except for a part of the periphery where the methylene chloride solution was cast, and had a spherical shape with a uniform shape.

Next, the surface of the pre-porous film was subjected to oxygen glow treatment under the following conditions using a magnetron sputtering apparatus (CFS-10-EP70 manufactured by Shibaura Eletech).
Initial vacuum: 1.2E-3Pa
Oxygen pressure: 0.9 Pa
RF glow: 1.5kW
Processing time: 60 sec

-Introduction of hydrophilic graft polymer-
Next, the porous substrate having a honeycomb structure subjected to oxygen glow treatment was immersed in an aqueous solution of sodium styrenesulfonate (10 wt%) that had been bubbled with nitrogen at 70 ° C. for 7 hours. After the immersion, the porous body was washed with running water for 8 hours. As a result, a porous film (sample 1) having a surface grafted with sodium polystyrene sulfonate was obtained.

  Moreover, the porous film (sample 2) grafted with polyacrylic acid was obtained by the same method as the sample 1 of Example 1 except having changed the sodium styrenesulfonate into acrylic acid.

  About the porous film of the samples 1 and 2, the cross section of the thickness direction was observed by SEM. From the cross-sectional SEM photograph, it was confirmed that a uniform film having a film thickness of 0.15 μm was formed along the surface of both porous films including the inside of each hole.

<Example 2>
Samples 3 and 4 were obtained by the same method as Sample 1 of Example 1 except that the reaction time for grafting (immersion time at 70 ° C.) was changed to 1 hour or 24 hours.

<Example 3>
The surface is a polyoxyethylene glycol acrylate polymer in the same manner as Sample 1 of Example 1 except that polyoxyethylene glycol monoacrylate (average number of oxyethylene units: 8.6) is used as the monomer solution for grafting. A grafted porous film (Sample 5) was obtained.

<Example 4>
A solution having the following composition was prepared as a monomer solution for grafting, and oxygen was removed by bubbling nitrogen for 10 minutes.
・ Acrylic acid: 10g
・ Sodium periodate: 10mg
・ Ion exchange water: 90g

  The same pre-porous film as that prepared in Example 1 was immersed in a petri dish filled with this solution. Next, exposure was performed for 5 minutes with a high-pressure mercury lamp (manufactured by USHIO INC., UVX-02516S1LP01). After exposure, the sample was taken out and thoroughly washed with ion exchange water. As a result, Sample 6 was obtained.

<Example 5>
Samples 7 and 8 were obtained in the same manner as in Example 4 except that the acrylic acid used in Example 4 was replaced with N-vinylacetamide and N, N-dimethylacrylamide.

<Comparative example>
The same pre-porous film as that prepared in Example 1 was not subjected to any surface treatment such as oxygen glow treatment or grafting treatment. Sample 9 was obtained. The same sample 11 as the sample 10 was produced except that the treatment was performed for 180 seconds.

<Evaluation>
The following (1) to (6) were evaluated using the surface-grafted porous films obtained in Examples 1 to 5 and Comparative Examples.
(1) Weight average molecular weight of surface graft polymer The sample is immersed in methylene chloride together with the base material, the porous film is dissolved, and the insoluble polymer is recovered. After repeating this operation three times, the product was dissolved in THF (tetrahydrofuran) and the weight average molecular weight was determined by GPC (HLC-8121 manufactured by Tosoh Corporation).

(2) Ratio of hydrophilic group and carbon number of surface graft polymer Moreover, the ratio of a carbonyl group and carbon number was calculated | required for the polymer extracted by evaluation 1 using ¹³ C-NMR (the product made from JEOL, JNM-ECAseries).

(3) Apparent surface contact angle The sample was allowed to stand for 60 minutes in an environment of 25 ° C. and 60% RH, and then the apparent surface contact angle was measured with a solid-liquid interface analyzer (DropMaster 300, manufactured by Kyowa Interface Science Co., Ltd.).

(4) Structural regularity 100 randomly selected aperture diameters were sampled with a digital microscope (VHX500, manufactured by Keyence Corporation) to obtain a coefficient of variation.

(5) Hyaluronic acid impregnation The sample was immersed in an aqueous solution of sodium hyaluronate (1 mg / 1 mL) at 25 ° C. for 60 minutes, then washed with water for 5 minutes, and then impregnated with hyaluronic acid by a colloidal iron staining method (Muller-Mowly method). Sex was evaluated.

(6) Strength The deformation (breaking, crushing, etc.) of the honeycomb structure before and after lightly rubbing the sample surface with a finger was evaluated with an optical microscope.
The evaluation results are shown in Table 1.

  From the results shown in Table 1, it was confirmed that the porous films (Samples 1 to 8) in Examples having hydrophilic graft polymers on the surface can be surface-modified with high uniformity and at the same time the strength is remarkably improved. It was done. Moreover, the effectiveness of the present invention is recognized from the fact that, as seen in the sample 11, it can be read that the structure is destroyed before the sufficient surface modification is performed in the gas phase oxidation treatment.

<Example 6>
(Synthesis of polymerization initiation polymer)
30 g of propylene glycol monomethyl ether (MFG) was added to a 300 ml three-necked flask and heated to 75 ° C. There, 8.1 g of [2- (acryloxy) ethyl] (4-benzoylbenzyl) dimethylammonium bromide, 9.9 g of 2-hydroxyethyl methacrylate, 13.5 g of isopropyl methacrylate, and dimethyl-2,2′-azobis (2-methylpropionate) A solution containing 0.43 g and 30 g of propylene glycol monomethyl ether (MFG) was added dropwise over 2.5 hours. Thereafter, the reaction temperature was raised to 80 ° C., and the reaction was further continued for 2 hours to obtain a polymerization initiating polymer (C) represented by the following formula.

(Preparation of pre-porous film)
As a casting liquid used in preparing the preporous film of Example 1, the preporous film was used under the same conditions as the preporous film except that 5% by weight of the polymerization initiating prepolymer (C) was further added to polycaprolactone. A film was obtained.

(Hydrophilic grafting)
Next, the preporous film is immersed in an aqueous solution of 10% by weight of α (styrene-4-sulfonyl) acetate sodium salt, and irradiated with light for 30 minutes using a 400w high-pressure mercury lamp in an argon atmosphere through a lattice mask having a width of 1 cm. did. After light irradiation, the obtained sample was thoroughly washed with ion-exchanged water to obtain a porous film in which (styrene-4-sulfonyl) acetic acid sodium salt was selectively grafted onto the irradiated surface.
After the film was dried, it was immersed in ion-exchanged water and taken out.As a result, a wetted area and a water-repellent surface area corresponding to the mask lattice were observed, and the pattern was hydrophilic grafted. Admitted.

  The porous film provided by the present invention may have a hydrophilic graft polymer according to the application on the surface of the film including the inside of the pores. In this way, a porous film having a hydrophilic graft polymer on the surface, for example, is extremely suitable for uniform modification treatment using a liquid phase, and also has high strength, high strength and excellent handling properties. It becomes a quality film, and it is easy to increase the area and can be manufactured efficiently. Accordingly, the porous film according to the present invention includes, for example, a retardation film, a polarizing film, a screen, a color filter, a display member, a cell culture member, a wound protective film, a transdermal absorption film, an acoustic vibration material, and a sound absorbing material. It can be used widely for vibration damping materials.

It is a schematic sectional drawing which shows an example of the structure of the porous film which concerns on this invention. It is a schematic plan view which shows an example of the porous film in which the hole is arranged in honeycomb form. It is an aa line schematic sectional drawing in Drawing 2A. It is a bb schematic sectional drawing in FIG. 2A. It is process drawing explaining an example of the manufacturing method of the porous film which concerns on this invention. It is the schematic which shows the state in which the polymer film was formed on the support body. It is the schematic which shows the state in which the organic solvent in a polymer film volatilizes. It is the schematic which shows the state from which water | moisture content volatilizes from the droplet in a polymer film.

Explanation of symbols

12 Porous film 14 Hydrophilic graft polymer 16 Support 18 Hole

Claims (13)

  A porous film having a hydrophilic surface in which a large number of pores are formed and a hydrophilic graft polymer chain is chemically bonded to the surface.   The porous film according to claim 1, wherein the hydrophilic graft polymer chain has a hydrophilic functional group.   The hydrophilic functional group is a nonionic hydrophilic group selected from a hydrophilic functional group having an N-monoalkyl-substituted structure and a hydrophilic functional group having an N-dialkyl-substituted amide group. Item 3. The porous film according to Item 2.   The porous film according to any one of claims 1 to 3, wherein the pores are regularly arranged.   The porous film according to claim 4, wherein the pores are formed so that pores having a pore diameter of 0.01 μm to 100 μm communicate with each other.   The porous film according to claim 5, wherein an average opening diameter that appears on the surface of the film of the holes formed so as to communicate with each other is larger than an average opening diameter of a communication portion between adjacent holes. .   The porous according to any one of claims 1 to 6, wherein a ratio of the number of hydrophilic groups and the number of carbon atoms constituting the hydrophilic graft polymer is between 0.05 and 0.35. the film.   The hydrophilic surface formed by chemically bonding the hydrophilic graft polymer chains of the porous film has a water contact angle of 2 to 40 degrees on the surface in an environment of 25 ° C. and 60% RH. The porous film as described in any one of Claims 1-7 characterized by these.   The porous film according to any one of claims 1 to 8, wherein the graft polymer has a weight average molecular weight of 10,000 or more and 5 million or less.   The substrate of the porous film is obtained by casting a liquid containing an organic solvent and a polymer compound on a support to form a film, and forming pores in the film. The porous film as described in any one of Claims 1-9.   The porous film contains a polymerization initiator, and after contacting with an unsaturated compound having a radical group capable of radical polymerization, the surface of the porous film is irradiated with an arbitrary pattern of radiation. The porous film as described in any one of Claims 1-10 which has the hydrophilic surface which produced | generated the hydrophilic graft | grafting polymer couple | bonded chemically in the shape of a pattern.   A porous film according to any one of claims 1 to 11, comprising a retardation film, a polarizing film, a screen, a color filter, a display member, a cell culture member, a wound protective film, and a transdermally absorbable drug film. A method for using a porous film, characterized by being used as an acoustic vibration material, a sound absorbing material, or a vibration damping material. Providing an organic solvent solution containing an organic solvent and a polymer compound on a support to form a film of the organic solvent solution;
By forming droplets in the film of the organic solvent solution and evaporating the organic solvent and the droplets in the film, a porous film having pores formed in the portions where the droplets are evaporated is produced. Process,
Providing a hydrophilic graft polymer on the surface of the porous film, and a method for producing the porous film.

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