JP2015196808A - Method for producing polyvinyl alcohol film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a PVA film, capable of easily producing a polyvinyl alcohol film which is little discolored and has a smooth surface, and to provide a film produced by the method.SOLUTION: Provided is a method for producing a polyvinyl alcohol film containing a surfactant and an antioxidant, comprising a step of mixing a mixture of the surfactant and the antioxidant with polyvinyl alcohol. Also provided is a polyvinyl alcohol film produced by the method. In the mixture of the surfactant and the antioxidant, it is preferable that the antioxidant is dispersed in the surfactant. Further, an amount of the antioxidant used is preferably 1 to 9 ppm based on mass relative to the polyvinyl alcohol.

Description

  The present invention relates to a method for producing a polyvinyl alcohol film capable of easily producing a polyvinyl alcohol film having a small color and a smooth surface, and a polyvinyl alcohol film produced thereby.

  Polyvinyl alcohol film (hereinafter, “polyvinyl alcohol” may be abbreviated as “PVA”) is excellent in mechanical properties, transparency, oxygen barrier properties, oil resistance, etc. It is used for applications such as films (films for keeping warm vegetables, growing vegetables, etc.), gas barrier materials, filters, optical films such as polarizing films, and the like.

  PVA films have the disadvantage that they are slightly colored. Conventionally, as a method for suppressing the coloring of the PVA film, there is known a method for producing a PVA film using the PVA as a raw material after drying the PVA under a condition that is hardly affected by oxygen to obtain a PVA with little coloring. (See, for example, Patent Document 1).

JP 2004-226707 A

However, in the conventional methods as described above, it is possible to prevent coloration when producing PVA, but there is room for further improvement in terms of sufficiently preventing coloration when producing PVA film. It was.
Then, an object of this invention is to provide the manufacturing method of the PVA film which can manufacture a PVA film with little coloring and a smooth surface, and the PVA film manufactured by it.

  As a result of intensive studies to achieve the above object, the inventors of the present invention prepared a PVA film containing both a surfactant and an antioxidant by mixing the surfactant and the antioxidant in advance. When it was used, it was found that the above-mentioned problems were solved, and further studies were made based on the findings to complete the present invention.

That is, the present invention
[1] A method for producing a PVA film containing a surfactant and an antioxidant, the method comprising a step of mixing a mixture of a surfactant and an antioxidant and PVA;
[2] The method according to [1] above, wherein the antioxidant is dispersed in the surfactant in the mixture of the surfactant and the antioxidant;
[3] The production method of the above [1] or [2], wherein the amount of the antioxidant used is 1 to 9 ppm by mass relative to PVA;
[4] The production method according to any one of the above [1] to [3], wherein the antioxidant is a bisphenol-based antioxidant;
[5] A PVA film produced by the production method of any one of [1] to [4] above;
About.

  According to the present invention, a PVA film with little coloration and a smooth surface can be easily produced.

Hereinafter, the present invention will be described in detail.
The method of the present invention for producing a PVA film comprising a surfactant and an antioxidant comprises the step of mixing a mixture of surfactant and antioxidant with PVA. Usually, when producing a PVA film containing a surfactant and an antioxidant, a surfactant and an antioxidant are added to the mixture of PVA and the liquid medium when preparing a film-forming stock solution for producing the PVA film. And are added separately. On the other hand, in the production method of the present invention, a mixture of a surfactant and an antioxidant is prepared in advance, and this is further mixed with PVA (preferably a mixture of PVA and a liquid medium). . By adopting such a method, a PVA film with little coloration and a smooth surface can be easily produced. In addition, although this invention is not limited at all, the following reasons can be considered as a reason which the above outstanding effects are show | played. That is, when the antioxidant is mixed with PVA without being premixed with the surfactant, the dispersibility of the antioxidant in the film-forming stock solution is low and the antioxidant effect is not sufficiently exhibited, and the surface of the film The smoothness of the film surface is not improved, but by mixing the surfactant and the antioxidant in advance, the antioxidant effect of the antioxidant is fully exerted and the coloring is reduced, and the film surface is smooth. Is also expected to improve.

[PVA]
The PVA used in the present invention is preferably an unmodified PVA represented by a saponified product of a homopolymer of vinyl acetate, but an olefin such as ethylene or propylene; acrylic acid, acrylic ester, methacrylic acid (Meth) acrylic monomers such as methacrylic acid esters, acrylamide or derivatives thereof, methacrylamide or derivatives thereof; vinyl ethers; vinyl halides; maleic acid or salts or esters thereof; monomers such as vinylsilyl compounds It may be a modified PVA in which one type or two or more types are copolymerized in the main chain. The amount of modification by these monomers in the modified PVA is preferably 25 mol% or less, more preferably 10 mol% or less, more preferably 5 mol% based on the number of moles of all structural units constituting the modified PVA. More preferably, it is as follows.

  The polymerization degree of PVA is not particularly limited, but is preferably in the range of 500 to 8,000, more preferably in the range of 700 to 6,000, and in the range of 1,000 to 4,000. More preferably it is. When the polymerization degree of PVA is 500 or more, the mechanical strength of the obtained PVA film is improved. On the other hand, when the degree of polymerization of PVA is 8,000 or less, the thickness of the PVA film obtained by excessively increasing the viscosity of the film-forming stock solution when the PVA film is produced using the film-forming stock solution described below. It is possible to effectively prevent non-uniformity. In addition, the polymerization degree of PVA as used in this specification means the average polymerization degree measured according to description of JISK6726-1994.

  The saponification degree of PVA is preferably 80 mol% or more, and more preferably 85 mol% or more. When the degree of saponification of PVA is 80 mol% or more, the water swelling property of the obtained PVA film is improved. In this specification, the degree of saponification of PVA refers to the total number of moles of structural units (typically vinyl ester units) that can be converted into vinyl alcohol units by saponification and the vinyl alcohol units of PVA. The proportion (mol%) occupied by the number of moles of vinyl alcohol units. The degree of saponification can be measured according to the description of JIS K6726-1994.

[Surfactant]
There is no restriction | limiting in particular in the kind of surfactant used in this invention, Any of anionic surfactant, nonionic surfactant, a cationic surfactant, and an amphoteric surfactant can also be used. The surfactant may be used alone or in combination of two or more.

  Examples of the anionic surfactant include carboxylic acid types such as potassium laurate; sulfate ester types such as octyl sulfate; sulfonic acid types such as dodecylbenzenesulfonate and sodium alkylbenzenesulfonate; polyoxyethylene lauryl ether phosphate mono Ethanolamine salt, octyl phosphate potassium salt, lauryl phosphate potassium salt, stearyl phosphate potassium salt, octyl ether phosphate potassium salt, dodecyl phosphate sodium salt, tetradecyl phosphate sodium salt, dioctyl phosphate Ester sodium salt, polyoxyethylene arylphenyl ether phosphate potassium salt, polyoxyethylene arylphenyl ether phosphate amine salt, etc. And the like.

  Examples of nonionic surfactants include alkyl ether types such as polyoxyethylene oleyl ether and polyoxyethylene lauryl ether; alkylphenyl ether types such as polyoxyethylene octylphenyl ether; alkyl ester types such as polyoxyethylene laurate. Alkylamine type such as polyoxyethylene lauryl amino ether; alkylamide type such as polyoxyethylene lauric acid amide; polypropylene glycol ether type such as polyoxyethylene polyoxypropylene ether; lauric acid diethanolamide, oleic acid diethanolamide, etc. Examples include alkanolamide type; allyl phenyl ether type such as polyoxyalkylene allyl phenyl ether.

  Examples of the cationic surfactant include amines such as laurylamine hydrochloride; quaternary ammonium salts such as lauryltrimethylammonium chloride; and pyridinium salts such as laurylpyridinium chloride.

  Examples of amphoteric surfactants include N-alkyl-N, N-dimethylammonium betaine.

  The amount of the surfactant used is preferably in the range of 0.01 to 5 parts by mass with respect to 100 parts by mass of PVA, since the effects of the present invention are more remarkably achieved, and 0.02 to 3 parts by mass. More preferably within the range of parts. By using the surfactant in the above-mentioned usage amount, a PVA film containing the amount of the surfactant is obtained.

〔Antioxidant〕
Although there is no restriction | limiting in particular in the kind of antioxidant used in this invention, Since the effect of this invention is show | played more notably, a bisphenol-type antioxidant is preferable. Examples of bisphenol antioxidants include 4,4′-butylidenebis (6-tert-butyl-3-methylphenol), 2,2′-methylenebis (4-ethyl-6-tert-butylphenol), 2,2 '-Methylenebis (4-methyl-6-tert-butylphenol) and the like. Among these antioxidants, 4,4′-butylidenebis (6-t-butyl-3-methylphenol) is particularly preferable because coloring of the obtained PVA film can be further reduced.

  The amount of the antioxidant used is preferably within a range of 1 to 9 ppm, more preferably within a range of 3 to 7 ppm, based on mass with respect to PVA. When the usage amount is 1 ppm or more, coloring of the obtained PVA film can be further reduced. On the other hand, when the use amount is 9 ppm or less, coloring of the obtained PVA film can be further reduced and surface smoothness is further improved. By using an antioxidant in the above-mentioned usage amount, a PVA film containing the amount of the antioxidant is obtained.

[Plasticizer, inorganic filler and other components]
The PVA film has one or more plasticizers, inorganic fillers and other components (components other than PVA, surfactants, antioxidants, plasticizers and inorganic fillers) or the like depending on the application and usage. Two or more kinds can be further contained. When the PVA film contains one or more of a plasticizer, an inorganic filler, and other components, these components are previously contained in a film-forming stock solution described below before forming the PVA film. It is preferable. There is no particular limitation on the blending timing of these components in the case where these components are preliminarily contained in the film-forming stock solution, and the blending of the surfactant, the antioxidant, and the PVA is possible. And before mixing the mixture of antioxidant and PVA with the surfactant and / or antioxidant mixture and / or PVA, or before mixing the surfactant and antioxidant It can be blended in advance in either or both of the surfactant and the antioxidant. When the PVA film contains one or more of plasticizers, inorganic fillers and other components, the amount of these components used is the same as the content of these components in the target PVA film. do it.

  Although there is no restriction | limiting in particular in the kind of plasticizer, 1 type (s) or 2 or more types among polyhydric alcohol type plasticizers, such as glycerol, trimethylene glycol, propylene glycol, and diethylene glycol, are preferable, and glycerol is especially preferable. The content of the plasticizer in the PVA film is preferably 30 parts by mass or less and more preferably 25 parts by mass or less with respect to 100 parts by mass of PVA. When the said content is 30 mass parts or less, it can prevent effectively that a plasticizer oozes out on the surface of a PVA film.

  Examples of inorganic fillers include silica, heavy or light calcium carbonate that may be surface-treated, aluminum hydroxide, aluminum oxide, titanium oxide, diatomaceous earth, mica, magnesium carbonate, kaolin, halosite, viroferrite, selenium. Clays such as sites, talc and the like can be mentioned, and one or more of these can be used. Among these, silica and talc are preferable from the viewpoint of dispersibility in PVA. It is preferable that content of the inorganic filler in a PVA film is 10 mass parts or less with respect to 100 mass parts of PVA.

  Examples of other components other than the above-described PVA, surfactant, antioxidant, plasticizer, and inorganic filler include, for example, a crosslinking agent, a colorant, a fragrance, an extender, an antifoaming agent, a release agent, an ultraviolet absorber, and starch. , Polymers other than PVA (water-soluble polymers other than PVA, etc.) can be used, and one or more of these can be used. The ratio of the total mass of PVA, surfactant, antioxidant, plasticizer and inorganic filler to the total mass of the PVA film is preferably in the range of 50 to 100% by mass, preferably 80 to 100% by mass. More preferably, it is in the range of 90-100 mass%.

[Production method of PVA film]
The method of the present invention for producing a PVA film comprising a surfactant and an antioxidant comprises the step of mixing a mixture of surfactant and antioxidant with PVA. There is no particular limitation on the method for preparing the mixture of the surfactant and the antioxidant. For example, a method of adding an antioxidant to the surfactant or adding a surfactant to the antioxidant and then stirring with a stirrer Is mentioned.

  In the mixture of the surfactant and the antioxidant, it is preferable that the antioxidant is dispersed in the surfactant because the effects of the present invention are more remarkably exhibited. The mixture in which the antioxidant is dispersed in the surfactant can be obtained by appropriately selecting the amounts and types of the antioxidant and the surfactant, for example, in the liquid surfactant. It can be obtained by adding a solid antioxidant to and mixing.

  There is no particular limitation on the mixing method when mixing the mixture of surfactant and antioxidant with PVA. For example, the mixture of surfactant and antioxidant and PVA pellets are mixed to form a mixture. A method of further mixing a liquid medium such as water; a method of mixing PVA dissolved in a liquid medium such as water and a mixture of a surfactant and an antioxidant; and impregnating a PVA pellet with a liquid medium such as water And a method of further mixing this with a mixture of a surfactant and an antioxidant. Among these, the method of mixing the PVA dissolved in a liquid medium such as water with a mixture of a surfactant and an antioxidant because the effect of the present invention is more remarkably; After the liquid medium is impregnated, a method of further mixing this with a mixture of a surfactant and an antioxidant is preferable. After impregnating the PVA pellets with a liquid medium such as water, the surfactant and the surfactant A method of further mixing the mixture of antioxidants is more preferable. Mixing can be performed using a stirrer or an extruder using a stirring blade.

  There is no particular limitation on the type of film forming method for the PVA film as long as the provisions of the present invention are satisfied. For example, a cast film forming method, an extrusion film forming method, a wet film forming method, a gel film forming method using a film forming stock solution, etc. Is mentioned. These film forming methods may be used alone or in combination of two or more. Among these film forming methods, the cast film forming method and the extrusion film forming method are preferable because a PVA film having uniform thickness and width and good physical properties can be obtained.

  As the film forming stock solution, one or more of PVA, a surfactant, an antioxidant, and, if necessary, the above-described plasticizer, inorganic filler, and other components were dissolved in a liquid medium. It contains one or two or more of a film-forming stock solution, PVA, a surfactant, an antioxidant, a liquid medium, and, if necessary, the above-described plasticizer, inorganic filler, and other components. The film-forming stock solution etc. which are are mentioned.

  Examples of the liquid medium used for the preparation of the membrane forming stock solution include water, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, ethylene glycol, glycerin, propylene glycol, diethylene glycol, triethylene glycol, and tetraethylene glycol. , Trimethylolpropane, ethylenediamine, diethylenetriamine and the like, and one or more of them can be used. Among these, water is preferable from the viewpoint of environmental load and recoverability.

  The volatile fraction of the film-forming stock solution (content ratio in the film-forming stock solution of volatile components such as liquid media removed by volatilization or evaporation during film formation) varies depending on the film-forming method, film-forming conditions, etc. Specifically, it is preferably in the range of 50 to 95% by mass, more preferably in the range of 55 to 90% by mass, and still more preferably in the range of 60 to 85% by mass. When the volatile fraction of the film-forming stock solution is 50% by mass or more, the viscosity of the film-forming stock solution does not become too high, and filtration and defoaming are smoothly performed during preparation of the film-forming stock solution, and there are few foreign matters and defects. Film production is facilitated. On the other hand, when the volatile fraction of the film-forming stock solution is 95% by mass or less, the concentration of the film-forming stock solution does not become too low, and the production of an industrial PVA film becomes easy.

  As an example of a specific method for producing a PVA film, for example, a T-type slit die, a hopper plate, an I-die, a lip coater die or the like is used to rotate the above-mentioned film forming stock solution on the most upstream side. The volatile component is uniformly discharged or cast on the peripheral surface of the first roll (or belt) and the volatile component is discharged from one surface of the film discharged or cast on the peripheral surface of the first roll (or belt). Evaporate to dry, then further dry on the circumference of one or more rotating heated rolls located downstream, or pass through a hot air dryer and further dry, The method of winding with a winding device can be preferably employed industrially. Drying with a heated roll and drying with a hot air dryer may be performed in an appropriate combination.

  The formed film can be heat-treated as necessary. The temperature of the heat treatment is preferably in the range of 70 to 180 ° C, and may be in the range of 100 to 150 ° C. Examples of the heat treatment time include a range of 1 second to 1 hour. In addition, in each process of manufacturing the PVA film including the heat treatment, when exposed to a temperature that is too high, the water swellability of the resulting PVA film may be reduced. It is preferable to keep the film forming stock solution and the film temperature until the production of the PVA film at 180 ° C. or lower, and may be kept at 150 ° C. or lower, 140 ° C. or lower, and further 130 ° C. or lower.

  If necessary, uniaxial or biaxial stretching can be performed at any one or two or more stages before, during or after drying. The stretching temperature is preferably in the range of 20 to 120 ° C. In addition, the draw ratio is preferably in the range of 1.05 to 5 times, more preferably in the range of 1.1 to 3 times, based on the length before drawing. Furthermore, if necessary, the residual stress can be reduced by heat fixing the film after stretching.

  According to the manufacturing method of the present invention, a PVA film with little coloring can be easily manufactured. The b value of the PVA film produced by the production method of the present invention is preferably 1.1 or less, more preferably 1.0 or less, still more preferably 0.9 or less, and It is particularly preferably 8 or less, and preferably 0 or more. The b value of the PVA film can be measured by the method described later in Examples.

  According to the production method of the present invention, a PVA film having a smooth surface can be produced easily. Ra of the PVA film produced by the production method of the present invention is preferably 5.8 nm or less, more preferably 4.5 nm or less, and particularly preferably 3.0 nm or less. When the Ra is 5.8 nm or less, it is possible to effectively prevent foreign matter and the like from adhering to the film surface and lowering the quality. Although there is no restriction | limiting in particular in the minimum of the said Ra, The said Ra is 0.1 nm or more, for example. Ra of a PVA film can be measured by the method mentioned later in an Example.

  The thickness of the PVA film produced by the production method of the present invention is not particularly limited, and can be appropriately set according to the use or use mode of the PVA film, but is preferably in the range of 1 to 100 μm, More preferably, it is in the range of 3 to 50 μm. In addition, the thickness of a PVA film can measure the thickness of arbitrary 5 places, and can obtain | require as those average values.

  There is no restriction | limiting in particular in the use of the PVA film manufactured by the manufacturing method of this invention, For example, a fiber packaging material; Agricultural film (Film for vegetable preservation, vegetable growth etc.); Gas barrier material; Polarizing film, Retardation film Water-soluble film for hydraulic transfer, packaging, agriculture, civil engineering, medical, industrial, daily goods, toys, etc. It can be preferably used for a biodegradable film.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited at all by these Examples.

[Measurement of b value of PVA film]
A plurality of PVA films obtained in the following examples or comparative examples are stacked so as to have a thickness of 0.4 to 0.5 mm, and an ultraviolet-visible spectrophotometer (c light source, two-degree field of view, transmitted light) is used. The b value was measured, and this value was used as an index for coloring the PVA film.

[Measurement of Ra of PVA Film]
The PVA films obtained in the following examples or comparative examples were measured for Ra in the range of 0.091 mm ² using a scanning white interferometer. Note that both sides of the film were measured, and the larger Ra value was taken as the Ra value of this film. The Ra was used as an index of the surface smoothness of the PVA film.

[Example 1]
(1) Surfactant (polyoxyethylene lauric acid amide) 0.05 part by mass and antioxidant (4,4′-butylidenebis (6-t-butyl-3-methylphenol)) 0.0015 part by mass (described later) Was added to the PVA and stirred, to obtain a mixture in which the antioxidant was dispersed in the surfactant.
The above mixture is added to 100 mass parts of PVA (saponified vinyl acetate homopolymer, degree of polymerization 2,400, degree of saponification 99.9 mol%) impregnated with water, and further plasticizer By adding 12 parts by weight of (glycerin) and water and stirring, a film-forming stock solution having a volatile content rate of 70% by mass was obtained.
(2) The film-forming stock solution was cast on a PET film and dried at room temperature to obtain a 50 μm film. The obtained film was fixed to a frame and heat-treated at 160 ° C. for 10 minutes to obtain a PVA film.
(3) When each of b value and Ra was measured by the above-described method using the obtained PVA film, the b value was 0.9 and Ra was 3.5 nm.

[Example 2]
A PVA film was obtained in the same manner as in Example 1 except that the amount of the antioxidant used was changed from 0.0015 parts by mass to 0.0005 parts by mass (5 ppm by mass relative to PVA). When Ra was measured, the b value was 0.7 and Ra was 2.5 nm.

[Comparative Example 1]
Implementation was carried out except that the antioxidant and the surfactant were separately added to the PVA pellets impregnated with water without preparing a mixture in which the antioxidant was dispersed in the surfactant. When a PVA film was obtained in the same manner as in Example 1 and b value and Ra were measured, the b value was 1.3 and Ra was 6.0 nm.

Claims (5)

  A method for producing a polyvinyl alcohol film comprising a surfactant and an antioxidant, the method comprising a step of mixing a mixture of a surfactant and an antioxidant and polyvinyl alcohol.   The manufacturing method of Claim 1 with which the antioxidant is disperse | distributing in surfactant in the mixture of surfactant and antioxidant.   The manufacturing method of Claim 1 or 2 whose usage-amount of antioxidant is 1-9 ppm on the mass basis with respect to polyvinyl alcohol.   The manufacturing method of any one of Claims 1-3 whose antioxidant is a bisphenol-type antioxidant.   The polyvinyl alcohol film manufactured by the manufacturing method of any one of Claims 1-4.