JPH03223349A - Porous acrylic polymer film - Google Patents

Abstract

PURPOSE:To prepare the title film which shows both a waterproofness and moisture permeability and is excellent in the water retention by causing an arylic film to contain pores with a specified mean diameter in a specified void volume. CONSTITUTION:The title film virtually comprises an acrylic polymer and contains pores with a means diameter of 0.001-50mum in a void volume of 0.0010-0.2000cm<3>/g. The acrylic polymer, pref. being a polymer obtd. by the radical polymn. of a monomer component contg. 30-100wt.% 1-22C alkyl acrylate and/or methacrylate, may be a polymer obtd. by the polymn. in bulk, in a soln. or dispersion in an org. solvent, or in an aq. soln. or dispersion. The pores formed by the removal of starch contained in the film are pref.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application] The present invention relates to a porous acrylic film useful as a film having water retention and waterproof/moisture permeable properties.

[Prior art]

Acrylic polymer films (hereinafter referred to as acrylic films), which are copolymers mainly composed of acrylic esters and/or methacrylic esters, have excellent properties such as transparency, weather resistance, and water resistance. Because it has the characteristic that the texture can be freely adjusted from hard to soft by changing it, it can be used as a stand-alone film, as a laminate with other materials, or as a coating applied to various base materials. Widely used. Foams of acrylic polymers have been known as examples of acrylic polymers in which pores are formed. BACKGROUND ART Foams or sheets obtained by foaming and foams obtained by vigorously stirring an acrylic polymer emulsion (hereinafter referred to as acrylic emulsion) to create foam and then casting the foam are known.

[Problems with the prior art and problems to be solved by the present invention]

The foam obtained by the above-mentioned known technology has large pore diameters of several hundred μm to several mm, and has a high expansion ratio of several times to several tens of times, and has pores in the polymer film. Rather than actually existing, it is in the form of a thin polymer film with a large number of pores, and it no longer has the properties of the acrylic polymer used as the raw material. Such acrylic polymer foam is suitable for application as plastic foam or acrylic leather, and is used as a film that has both waterproofness and moisture permeability and has excellent water retention, which is the purpose of the present invention. is not suitable. However, the average diameter is 0
．． 0.001~50μm pores with pore volume 0.0010~0
．． Conventionally, an acrylic film with an internal weight in the range of 2000crn"7g has not existed, and the present invention is a novel film that retains the original properties of an acrylic polymer while providing waterproof/moisture permeability and water retention properties. The present invention aims to provide a porous acrylic film.

[Means for Achieving the Object] The present inventors have discovered that a film in which pores of a specific average diameter and a specific pore volume are incorporated in an acrylic polymer film can achieve the above object, and have developed the present invention. has been reached.

That is, the present invention substantially relates to acrylic polymers or acrylic films.

The acrylic polymer in the present invention refers to a polymer obtained using only known acrylic esters and a copolymer of acrylic esters and/or methacrylic esters and other monomers, including acrylic esters and/or methacrylic esters and other monomers. Or 30Mj of acrylic acid ester in all monomer components
A more preferable acrylic polymer refers to a copolymer obtained by using 1% or more of ester of acrylic acid or methacrylic acid and 0.001 to 22 aliphatic alcohol or alicyclic alcohol. It is a copolymer containing at least one of these in a proportion of 950% or more by weight of all monomers.

The acrylic polymer may be in the form of a lump, an organic solvent solution or dispersion, an aqueous solution or an aqueous dispersion, but when the porous acrylic film of the present invention is obtained by removing starch, It is preferable to use the form of an aqueous solution or aqueous dispersion because it is easy to mix, it is easy to obtain a film in which starch is uniformly dispersed, and it has the advantages of safety, hygiene, price, and ease of handling. The form of an aqueous dispersion is particularly preferred because of its excellent film performance, specifically products commercially available as acrylic emulsions or styrene-acrylic emulsions, such as Acryset@202.
E, Acryset @204E, Acryset■210E
, Acryset ■285E, Acryset ■ll0E (
Both products (manufactured by Tamizu Shokubai Kagaku Kogyo ■) can be preferably used. Furthermore, a curing agent such as an aqueous melamine resin or epoxy resin can be used in combination with these acrylic emulsions, if necessary.

The porous acrylic film of the present invention has pores with an average diameter of 0.001 to 50 μm, preferably 0.001 to 20 μm, and a pore volume of 0.0010 to 20 μm.
0.2000cm”7g, preferably 0.0010~
The pores can be formed within the range of 0.0500cm''7g.For example, there is a method of mixing the following additives into an acrylic polymer, forming a film, and then removing the additives.

Additives: Solvent dyes that are incompatible with acrylic polymers; Water-oil-based substances; Among the above additives, water-extractable substances allow easy adjustment of the diameter of the pores formed, and are easy to extract to remove the additives. Water can be used as a liquid medium, which is preferable.As the water-extractable substance, natural or synthetic water-soluble or water-dispersible polymer compounds can preferably be used, but the particle size is suitable for the film of the present invention, Starches are particularly preferred because they are inexpensive and easy to handle.

Hereinafter, a method for producing the porous acrylic film of the present invention using starch will be explained.

As the starch, known starches such as those obtained from rice, adlay, wheat, corn, sweet potato, potato, arrowroot, adzuki bean, lotus, buckwheat, millet, etc. can be used. In addition, these starches may be processed by partial decomposition, cationization, etc. The pore size of the resulting porous acrylic film depends on the particle size of the starch used, so the pore size suitable for the purpose of the porous acrylic film is determined. Select and use a starch that provides the following.

For example, the relationship between starch type and pore size is as follows.

Botetoscouch: about 15-20 microns, corn starch: 8-12 microns, rice starch: 1-10 microns, soluble starch: 1-1000 angstroms.

The ratio of acrylic polymer and starch used is such that the pore volume of the porous acrylic film is between 0.0010 and 0.20.
- For boat fishing, the polymer/starch solids weight ratio should be 100/cm”/g.
The range is from 1 to 100/200, and from the viewpoint of the strength and performance of the obtained film, it is from 100/10 to 100/100.
Starch may be used in any form of powder, paste, dispersion, or aqueous solution. When used in the form of a paste or dispersion, the solvent is water,
It can be an organic solvent.

Mix acrylic polymer and starch in a predetermined ratio,
Stir to obtain a homogeneous mixture and make a film from this mixture. The film can be produced by known methods such as melt extrusion and casting, but when the acrylic polymer is in the form of an aqueous solution or dispersion, it is convenient to use the casting method.

Although there is no particular restriction on the thickness of the film, a range of 10 μm to 1 mm is appropriate.

To extract starch from an acrylic polymer film, for example, the acrylic polymer film containing starch may be swollen in dripping water, and then the starch may be decomposed in dilute sulfuric acid at λ to generate voids. However, in this method, when the acrylic polymer film is in the form of an aqueous dispersion, the acrylic polymer tends to be altered or deteriorated by the treatment depending on the polymer components.

Therefore, the present inventors investigated this point and found that if the starch was removed using an amylolytic enzyme, the process could be carried out under mild conditions, so the polymer would not deteriorate and a porous acrylic film with excellent performance could be obtained. Ta.

That is, in a preferred embodiment of the method for producing a porous acrylic film of the present invention, an acrylic polymer and starch, or starch and an amylolytic enzyme are mixed to obtain an acrylic polymer containing starch, This is a method in which this is formed into a film, and then starch is removed from the film using an amylolytic enzyme to create pores.

There are various amylases as starch degrading enzymes, and specific examples include α-amylase, β-amylase,
Examples include isoamylase, pullulase, glucoamylase, and the like. Among them, it is more preferable to use glucoamylase because it can efficiently remove starch under mild conditions.

There are two methods for removing starch from an acrylic polymer film containing starch.

(2) A method in which an acrylic polymer film containing starch is brought into contact with an aqueous solution of an amylolytic enzyme to hydrolyze and extract the starch.

■ Starch and starch-degrading enzymes are mixed into the polymer to form an acrylic polymer film containing starch, and this is brought into contact with water to hydrolyze and extract the starch.
How to remove it.

In the case of method (2), the concentration of the amylolytic enzyme aqueous solution is in the range of 0.1 to 100 g/ρ, preferably in the range of 0.5 to 10 g/ρ. When using method (2), the ratio of starch and amylolytic enzyme used is starch/amylolytic enzyme = 10010.1 to 10.
Range of 0/20, preferably 100/1 to 100/10
The range shall be .

In either method, the temperature at which starch is removed is 1
The temperature can be in the range of 0 to 100°C, but preferably in the range of 40 to 80°C, and the time can be determined so that the degree of starch removal is the desired level. ranges from 10 minutes to 72 hours, preferably 12 hours.
~48 hours.

The acrylic film and porous acrylic film in the present invention do not refer only to a single film (
, a laminate of the film and an inorganic base material such as another plastic film, cloth, paper, metal plate, slate board, plastic, cloth, paper, metal, wood, inorganic base material A mixture of heborimer and starch is applied and dried. impregnated products obtained by impregnating and drying a mixture of heborimer and starch, and glass fibers,
This includes films reinforced with metal fibers and organic fibers.

The porous acrylic film of the present invention thus obtained is
It has micropores uniformly distributed within the film, possibly (
As measured values, even when 100% of starch has been decomposed and extracted, it has excellent hydrophilicity, which is thought to be derived from a small amount of remaining starch. Therefore, the porous acrylic film of the present invention has an equilibrium moisture absorption rate of 3.5 to 30% at 100% RH, more preferably 3.5 to 20%, 10
Moisture permeability at 0%RH 11-100 g/24hr/
It has a performance of 7 mm or more and a tensile strength of 5 kg/cm or more. In other words, the film of the present invention has excellent strength, water retention, and waterproof/breathable properties, and by taking advantage of these properties, it can be used as a wall material that prevents condensation, as a material for moisture-permeable and waterproof clothing, and as a coating for various base materials. agent (useful as an adhesive or impregnating treatment agent)

The present invention will be explained in more detail in the following Examples.
The present invention is not limited by the examples, and
Unless otherwise specified, parts are parts by weight and percentages are percentages by weight.

Example 1 (Preparation of acrylic film containing starch) Rice starch 3 was added to 10 parts of Acryset 0204E (manufactured by Nippon Shokubai Chemical Co., Ltd., acrylic emulsion, solid content 49%).
of the mixture was added to obtain a homogeneous mixture. The mixture was applied to a release paper, and after drying at room temperature, the release paper was removed to a thickness of about 20 mm.
A film of 0 μm was obtained.

(Preparation of starch decomposition solution) AMG (NOVOIND
USTRIA/SF, glucoamylase), AM
1 part of G was dissolved in 1000 parts by volume of a buffer solution prepared by mixing 0.1 M citric acid and 0.2 M sodium monohydrogen phosphate to adjust the pH to 4.5.

(Hydrolysis of starch) The film was immersed in a starch decomposition solution whose temperature was controlled to 60°C for 18 hours.

(Measurement of Hydrolysis Rate) The produced glucose was measured by Somogyi's modified method, and the hydrolysis rate was calculated. 70.2% of the starch used was hydrolyzed.

(Measurement of pore volume) A sample (film) suspended from a precision balance with a thin steel wire is
- The sample was immersed in hebutane, the weight was measured every minute, and the apparent specific volume was calculated from the extrapolated value to time 0 obtained from the relationship diagram between elapsed time and weight using the following formula.

w-w' Apparent specific volume = (Cm''/g)-d W; Dry weight of sample in air W'; n- Extrapolated value to time O in hebutane d; n-
Specific Gravity of Hebutane Meanwhile, the sample was immersed in an n-hebutane desiccator and degassed under reduced pressure, and then the weight of the sample was measured in 1-hebutane, and the true specific volume was calculated from the following formula.

W-W'' True specific volume = (cm”/g) - d W”: Sample weight in n-hebutane after degassing under reduced pressure Then, the pore volume was calculated using the following formula.

Pore volume=apparent specific volume−true specific volume (am”/g) The pore volume was O, OO79 cm”/g.

(Confirmation of pore formation using an electron microscope) The films in Examples were observed using an electron microscope.

No pores were observed in the film obtained using Acryset 0204E alone without starch. It was confirmed that the acrylic polymer film containing starch before being treated with the aqueous amylolytic enzyme solution had starch particles dispersed in the acrylic resin film.

In a porous film obtained by immersing an acrylic polymer film containing starch in an amylolytic enzyme aqueous solution for 18 hours, it was confirmed that the starch was hydrolyzed to form a porous film. It was also found that the pore diameter was approximately in the range of 3 to 6 μm.

Examples 2 to 15 Porous films were obtained by repeating the same operations as in Example 1, except that the polymer, starch, starch-degrading enzyme, starch-degrading treatment conditions, etc. were as shown in Table 1.

Comparative Example I A comparative film was prepared by repeating the same procedure as in Example 1, except that AMG (glucoamylase) was not used.

Starch hydrolysis rate is 1.3%, pore volume is 0,0
009 cm"/g.

(Note 1) AMG, as in Example 1, was dissolved in a buffer prepared by mixing O, LM citric acid and 0.2M sodium monohydrogen phosphate and adjusting the pH to 4.5.

(Note 2) BAN, N0VOINDUSTR
α-Amylase manufactured by IA/S was dissolved in a buffer solution in which 0.1 M citric acid and 0.2 M sodium monohydrogen phosphate were mixed and the pH was adjusted to 6.0.

(Note 3) Acryset 285E; manufactured by Nippon Shokubai Kagaku 1 Awaside, acrylic emulsion M-3; Sumitex Registry Jumin-3: manufactured by Sumitomo Chemical @, water-soluble melamine resin Acryset 285E/M-3, 10015 (solid After creating an acrylic film containing starch at room temperature, it was heat-treated at 120° C. for 5 minutes.

(Note 4) Alloron 453; Water-soluble acrylic resin manufactured by Nippon Shokubai Chemical Industry Co., Ltd. Non-volatile content 50% (Note 5) Allocet 5
270; Solvent-type acrylic resin manufactured by Nippon Shokubai Chemical Industry ■
Non-volatile content: 40% Example 16 3 parts of rice starch and 15 parts of AMGo were added to 10 parts of Acryset@204E to obtain a homogeneous mixture. The mixture was applied to release paper, dried at room temperature, and then the release paper was removed to obtain a film with a thickness of about 200 ILm.

(Hydrolysis of starch) A buffer solution prepared by mixing 0.IM citric acid and 0.2M sodium lhydrogen phosphate and adjusting the pH to 4.5 was adjusted to 60°C, and the above film was added to it. Soaked for 18 hours.

The hydrolysis rate is 75.3%, and the pore volume is 0,0
The weight was 081cm"7g.

Examples 17 to 19 Example 1 except that the polymer, starch, starch degrading enzyme, and starch decomposition treatment conditions were as shown in Table 2.
The same operation as in 6 was repeated to obtain a porous film.

Comparative Example 2 70.3 parts of ammonium stearate was added to 310 parts of Acryset 285E/M-3, and the mixture was stirred at high speed with a homomixer until the volume doubled, and then cast onto release paper. After preheating this at 80℃ for 15 minutes, it was heated to 120℃.
was heated for 5 minutes to obtain a foamed sheet with a thickness of about 500 μm. When the sheet was observed with an optical microscope, the size of the bubbles (pores) was in the range of 0.5 to 1 mm.

Example 20 For each film obtained in Examples 1 to 19 and Comparative Examples 1 to 2 and the non-porous acrylic film, the equilibrium moisture absorption rate, water vapor transmission rate, and film physical properties (elongation rate, strength) at each temperature were determined. It was measured. The measurement method for each item is as follows.

(Equilibrium moisture absorption rate) A sample (film) was placed in a desiccator containing a water/glycerin mixture in a ratio that would provide a predetermined humidity, and the weight (Wwet) was measured after 48 hours at 20°C. The weight (Wdry) after drying at ℃ for 2 hours was measured, and the equilibrium moisture absorption rate was measured using the following formula.

Wwet-Wdry Equilibrium moisture absorption rate; (%) Wdry (moisture permeability) Calcium chloride is placed in a desiccator containing a water/glycerin mixture in a ratio that provides a predetermined humidity, and the cup is tightly sealed with a sample (film). After 24 hours at 20° C., the weight increase of calcium chloride was measured.

(Film physical properties) Using an Instron universal testing machine, the sample was heated at 20°C and 65°C.
A tensile test was conducted under the condition of %RH.The measurement results for each item are shown in the third study.

Claims (1)

[Scope of Claims] 1. A film consisting essentially of an acrylic polymer, the film having pores with an average diameter of 0.001 to 50 μm and a pore volume of 0.0010 to 0.2000 cm^
3/g. 2. A claim in which the acrylic polymer is obtained by radical polymerization of a monomer component containing 30 to 100% by weight of an acrylic ester and/or a methacrylic ester having an alkyl group having 1 to 22 carbon atoms. Porous acrylic film according to 1. 3. The porous acrylic film according to claim 1, wherein the pores are generated by removing starch contained in the film.