JP2017052840A - Polyvinyl alcohol film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyvinyl alcohol film that has small dry shrinkage during film preparation, and also has excellent optical properties, mechanical properties, underwater stability and the like.SOLUTION: A modified cellulose fiber composite polyvinyl alcohol film comprises polyvinyl alcohol-based resin, and modified cellulose fiber having a repeating unit represented by formula (1) (X-Xeach independently represent a group having a cation group, a phosphoric acid-derived group, a carbonyl group or a modified carbonyl group).SELECTED DRAWING: None

Description

  The present invention relates to a polyvinyl alcohol film having excellent optical properties, good mechanical properties and linear expansion coefficient, small drying shrinkage and good underwater stability.

Polyvinyl alcohol films are used not only for general industrial fields but also for various applications from foods, cosmetics and pharmaceuticals to medical fields because of their film-forming properties. On the other hand, there was a problem in stability in water due to large drying shrinkage during film production, insufficient mechanical properties, and water solubility.
In order to improve the stability in water, a method of adding a film surfactant has been proposed (for example, Patent Document 1). However, this method has a problem in that the surfactant bleeds out over time, and the underwater stability and mechanical properties change. Furthermore, a method of adding nanofiber cellulose in which a part of hydroxyl groups is oxidized has been proposed (for example, Patent Document 2). However, this method has a problem that the dispersion of nanofiber cellulose is insufficient, and transparency increases when the amount added is increased. Also, little is known about the improvement of drying shrinkage and the improvement of mechanical properties during the production of polyvinyl alcohol films.

JP 2005-153508 A JP 2012-82395 A

  An object of the present invention is to improve the mechanical properties, linear expansion coefficient, and stability in water without impairing the optical properties of the obtained polyvinyl alcohol film due to small drying shrinkage during film production.

As a result of intensive studies by the inventor, the present inventors have found that the above-mentioned problems can be solved by uniformly dispersing a specific modified cellulose fiber in a polyvinyl alcohol-based resin.
That is, the gist of the present invention is as follows.
[1] A modified cellulose fiber composite polyvinyl alcohol film comprising a polyvinyl alcohol resin and a modified cellulose fiber having a repeating unit represented by the following general formula (1).

(Wherein X ₁ , X ₂ and X ₃ are each independently a group having a cationic group, a group derived from phosphoric acid, an alkylcarbonyl group having 1 to 20 carbon atoms, or an aryl group which may be substituted with an aryl group) Represents 2 to 6 alkenylcarbonyl groups, alkynylcarbonyl groups, or arylcarbonyl groups, provided that X ₁ , X ₂ , and X ₃ are not hydrogen atoms at the same time.)
[2] X ₁ , X ₂ and X ₃ in the general formula (1) are each independently a group having a cationic group, a group derived from phosphoric acid, or an alkylcarbonyl group having 1 to 20 carbon atoms. 1]. The modified cellulose fiber composite polyvinyl alcohol film of [1].
[3] The modified cellulose fiber composite polyvinyl alcohol film according to [1] or [2], containing 0.1 to 50 parts by weight of the modified cellulose fiber with respect to 100 parts by weight of the polyvinyl alcohol resin.
[4] A modified cellulose comprising a film comprising a composition comprising a polyvinyl alcohol resin and a modified cellulose fiber having a repeating unit represented by the general formula (1) and having a number average fiber diameter of 20 nm or less. A method for producing a fiber composite polyvinyl alcohol film.
[5] The method for producing a modified cellulose fiber composite polyvinyl alcohol film according to [4], wherein the number average fiber length of the modified cellulose fiber is 200 nm or more and 1 μm or less.

  The cellulose fiber composite polyvinyl alcohol film of the present invention has excellent optical properties, good mechanical properties and linear expansion coefficient, small drying shrinkage and good underwater stability.

Embodiments of the present invention will be described in detail below, but the description of the constituent elements described below is an example (representative example) of an embodiment of the present invention, and the present invention does not exceed the gist thereof. It is not limited to the contents.
The cellulose fiber composite polyvinyl alcohol film of the present invention is a film containing a polyvinyl alcohol resin and modified cellulose fibers.

[Polyvinyl alcohol resin]
The polyvinyl alcohol resin used in the film of the present invention is obtained by polymerizing a vinyl ester compound and then saponifying it in accordance with a conventional method. In the present invention, two or more kinds of polyvinyl alcohol resins may be mixed and used as necessary.
Examples of the vinyl ester compounds include vinyl formate, vinyl acetate, vinyl trifluoroacetate, vinyl propionate, vinyl butyrate, vinyl caprate, vinyl laurate, vinyl versatate, vinyl palmitate, and vinyl stearate. . These may be used alone or in combination of two or more, but vinyl acetate is preferably used practically.

  Further, as the polyvinyl alcohol resin used in the present invention, it is usually preferable to use unmodified polyvinyl alcohol, but partially modified modified polyvinyl alcohol may also be used. Examples of the modified polyvinyl alcohol include those obtained by copolymerizing a small amount of another monomer with a vinyl ester compound, and the ratio of the monomer in this case is within a range not inhibiting the effect of the present invention. % Or less, preferably 7 mol% or less.

  Examples of the other monomer include olefins such as ethylene, propylene, isobutylene, α-octene, α-dodecene, α-octadecene; acrylic acid, methacrylic acid, crotonic acid, maleic acid, maleic anhydride, itacone Unsaturated acids such as acids, salts thereof, mono- or dialkyl esters, etc .; Nitriles such as acrylonitrile and methacrylonitrile; Amides such as acrylamide and methacrylamide; Olefin sulfones such as ethylene sulfonic acid, allyl sulfonic acid and methallyl sulfonic acid Acids or salts thereof, alkyl vinyl ethers; polyoxyalkylene (meth) allyl ethers such as polyoxyethylene (meth) allyl ether and polyoxypropylene (meth) allyl ether; polyoxyethylene (meth) acrylate Polyoxyalkylene (meth) acrylates such as polyoxypropylene (meth) acrylate, polyoxyalkylene (meth) acrylamides such as polyoxyethylene (meth) acrylamide, polyoxypropylene (meth) acrylamide; polyoxyethylene [1- (meta ) Acrylamide-1,1-dimethylpropyl] ester, polyoxyethylene vinyl ether, polyoxypropylene vinyl ether, polyoxyethylene allylamine, polyoxypropylene allylamine, polyoxyethylene vinylamine, polyoxypropylene vinylamine, diacrylacetone amide, N -Acrylamidomethyltrimethylammonium chloride, allyltrimethylammonium chloride, dimethyldiallylammonium chloride, Methyl allyl vinyl ketone, N- vinylpyrrolidone, vinyl chloride, vinylidene chloride and the like. These other monomers may be used alone or in combination of two or more.

In the present invention, (meth) allyl means allyl or methallyl, (meth) acryl means acryl or methacryl, and (meth) acrylate means acrylate or methacrylate.
The polymerization (or copolymerization) using the vinyl ester compound is not particularly limited and a known polymerization method is used. Usually, an alcohol such as methanol, ethanol or isopropyl alcohol is used as a solvent. Solution polymerization is performed. In addition to solution polymerization, emulsion polymerization and suspension polymerization are also possible.

The polymerization reaction is carried out using a known radical polymerization catalyst such as azobisisobutyronitrile, acetyl peroxide, benzoyl peroxide, lauroyl peroxide, and the reaction temperature is usually 35 ° C. to boiling point, more preferably 50 It is selected from a range of about ~ 80 ° C.
Next, when the obtained vinyl ester polymer is saponified, the vinyl ester polymer is dissolved in an alcohol in the presence of an alkali catalyst. Examples of the alcohol include methanol, ethanol, butanol and the like, and the concentration of the vinyl ester copolymer in the alcohol is usually appropriately selected within the range of 20 to 50% by weight.

  As the alkali catalyst at the time of the saponification, for example, an alkali catalyst such as an alkali metal hydroxide or alcoholate such as sodium hydroxide, potassium hydroxide, sodium methylate, sodium ethylate, potassium methylate or the like may be used. it can. What is necessary is just to select the usage-amount of the said alkali catalyst suitably in the range of 1-100 millimol equivalent normally with respect to a vinyl ester polymer. In some cases, saponification with an acid catalyst is also possible.

  Further, as the polyvinyl alcohol resin, it is also preferable to use a polyvinyl alcohol resin having a 1,2-diol structure in the side chain, and the polyvinyl alcohol resin having a 1,2-diol structure in the side chain is, for example, ( i) a method of saponifying a copolymer of vinyl acetate and 3,4-diacetoxy-1-butene, (ii) a method of saponifying and decarboxylating a copolymer of vinyl acetate and vinyl ethylene carbonate, (iii) ) A method of saponifying and deketalizing a copolymer of vinyl acetate and 2,2-dialkyl-4-vinyl-1,3-dioxolane, and (iv) a copolymer of vinyl acetate and glycerin monoallyl ether. It is obtained by a saponification method or the like.

In the present invention, the average saponification degree of the polyvinyl alcohol-based resin is usually 70 mol% or more. For example, the average saponification degree is 70 to 90 mol% in applications where importance is attached to processing suitability at a high temperature of 100 ° C or higher. On the other hand, the average saponification degree is preferably 90% by mole or more in applications where heat resistance is important. In addition, when the average saponification degree of polyvinyl alcohol-type resin is too low, not only film strength will fall, but it will become difficult to peel a film from the cast surface at the time of manufacture. In addition, the average saponification degree is JIS
Measured according to K 6726.

  Furthermore, the viscosity of a 4% by weight aqueous solution of the polyvinyl alcohol resin at 20 ° C. is preferably in the range of 5 to 70 mPa · s, and more preferably in the range of 15 to 60 mPa · s. If the 4% by weight aqueous solution viscosity is too low, the strength of the film tends to decrease. On the other hand, if the viscosity of the 4 wt% aqueous solution is too high, the viscosity tends to be high and it becomes difficult to form a film. The viscosity of the 4 wt% aqueous solution at 20 ° C. is measured according to JIS K 6726.

[Modified cellulose fiber]
The cellulose fiber contained in the film of the present invention has a repeating unit of the following general formula (1).

(Wherein X ₁ , X ₂ and X ₃ are each independently a group having a cationic group, a group derived from phosphoric acid, an alkylcarbonyl group having 1 to 20 carbon atoms, or an aryl group which may be substituted with an aryl group) 2 to 6 alkenylcarbonyl groups, alkynylcarbonyl groups, or arylcarbonyl groups, provided that X ₁ , X ₂ , and X ₃ do not simultaneously become hydrogen atoms)
The modified cellulose fiber used in the present invention is one in which a part of the hydroxyl group of cellulose is substituted with another group. By using a modified cellulose fiber, defibration is improved, stability in an aqueous dispersion is improved, and it is easy to uniformly disperse in a polyvinyl alcohol resin, which is preferable.

<Group having cationic group>
Specific examples of the group having a cationic group include onium groups such as an ammonium group, a phosphonium group, and a sulfonium group. The group having an onium group is usually a group having a molecular weight of about 1000 or less. Specifically, primary ammonium, secondary ammonium, tertiary ammonium, ammonium such as quaternary ammonium, phosphonium, sulfonium or a group having any of these, that is, a group having ammonium, a group having phosphonium, or sulfonium. Group which has. In the present invention, the cationic group is preferably a group containing ammonium, and particularly preferably a group containing quaternary ammonium.

  The group that reacts with the hydroxyl group of cellulose contained in the cationizing agent that introduces a cationic group is not particularly limited as long as it is a reactive group that reacts with the hydroxyl group to form a covalent bond. Examples thereof include a halohydrin group, an active halogen group, an active vinyl group, and a methylol group that can be formed. Among these, an epoxy group or a halohydrin group capable of forming it is preferable from the viewpoint of reactivity.

  Examples of the cationizing agent for introducing a cationic group include glycidyltrialkylammonium halides such as glycidyltrimethylammonium chloride and 3-chloro-2-hydroxypropyltrimethylammonium chloride, and halohydrins thereof. These may be used alone or in combination of two or more. Of these, glycidyltrimethylammonium chloride is preferred from the viewpoint of reactivity.

As a reaction method between the cationizing agent and cellulose, for example, when glycidyltrialkylammonium halide is used, the reaction is performed by reacting glycidyltrialkylammonium halide and a catalyst alkali metal hydroxide in the reaction solvent. The method of letting it be mentioned.
The reaction solvent is 3 to 20 times by weight of water or lower alcohol, specifically methanol, ethanol, n-propyl alcohol, isopropyl alcohol, n-butanol or the like, or these A mixed solvent of lower alcohol and water can be used.

As the alkali metal hydroxide salt of the catalyst, one or more of sodium hydroxide, potassium hydroxide and the like can be used.
The amounts of the cationizing agent and the catalyst used are appropriately adjusted according to the cellulose used, the solvent composition of the reaction system, the mechanical conditions of the reactor, and other factors.
The reaction temperature of the cationization reaction is preferably 30 ° C or higher, more preferably 40 ° C or higher, preferably 90 ° C or lower, and more preferably 80 ° C or lower. The reaction time is usually 30 minutes or longer, preferably 1 hour or longer, usually 10 hours or shorter, and 4 hours or shorter.

After completion of the reaction, the remaining catalyst is neutralized with a mineral acid or an organic acid, and then washed and purified by a conventional method to obtain cationized cellulose.
The cationized cellulose preferably has a cation group of 0.05 mmol / g or more with respect to the weight of the cationized cellulose in terms of defibration and recovery rate, and is 0.08 mmol. / G or more is more preferable, and 0.10 mmol / g or more is particularly preferable. Further, the content of the cationic group is 3.0 mmol / g or less in order to prevent the water-soluble portion from increasing and dissolution in water easily occurs, and also increase the affinity with the resin. Therefore, it is preferably 2.5 mmol / g or less. The amount of the cationic group is a value calculated by elemental analysis.
Specifically, for example, when the cation group is ammonium, the amount of nitrogen is quantified according to JIS-K2609 using a nitrogen measuring device and divided by the molecular weight of nitrogen to calculate per element weight. The number of moles (for example, mmol / g) can be converted.

<Group derived from phosphoric acid>
Specific examples of the group derived from phosphoric acid include at least one selected from the group consisting of phosphoric acid, polyphosphoric acid, phosphorous acid, phosphonic acid, polyphosphonic acid, and salts or esters thereof. Among these, a compound having a phosphoric acid group is preferable because it is low-cost and easy to handle, and a phosphoric acid group can be introduced into the hydroxy group of cellulose to further improve the refinement (defibration) fibrillation efficiency.

  Examples of the compound having a phosphoric acid group include phosphoric acid, lithium dihydrogen phosphate which is a lithium salt of phosphoric acid, dilithium hydrogen phosphate, trilithium phosphate, lithium pyrophosphate, lithium polyphosphate, and sodium dihydrogen phosphate which is a sodium salt of phosphoric acid, Examples thereof include disodium hydrogen phosphate, trisodium phosphate, sodium pyrophosphate, sodium polyphosphate, and potassium phosphates such as potassium dihydrogen phosphate, dipotassium hydrogen phosphate, tripotassium phosphate, potassium pyrophosphate, and potassium polyphosphate.

Among these, phosphoric acid, sodium salt of phosphoric acid, and potassium salt of phosphoric acid are preferable, and sodium dihydrogen phosphate and disodium hydrogen phosphate are more preferable from the viewpoint of high efficiency of introducing phosphate groups and easy industrial application.
In addition, the compound is preferably used as an aqueous solution because of the uniformity of the reaction and the introduction efficiency of the group derived from phosphoric acid. Further, an organic compound such as urea may be contained in the aqueous solution as in the urea phosphoric acid method which is a known technique. The pH of the aqueous solution of the compound is preferably 7 or less because the phosphate group introduction efficiency is high. From the viewpoint of suppressing hydrolysis of cellulose fibers, pH 3 to 7 is particularly preferable.

Cellulose introduced with phosphoric acid-derived groups has 0.05 mmol / g or more of phosphoric acid groups with respect to the weight of cellulose introduced with phosphoric acid-derived groups, from the viewpoint of improving defibration and recovery rate. Is more preferable, 0.08 mmol / g or more is more preferable, and 0.10 mmol / g or more is particularly preferable. Further, the content of the phosphate group is 3.0 mmol / g or less in order to prevent the water-soluble portion from increasing and dissolution in water easily occurs, and also increase the affinity with the resin. Therefore, it is preferably 2.5 mmol / g or less. The amount of the phosphoric acid group is a value calculated by the method of “Test Method T237 cm-08 (2008): Carboxyl Content of pull” of TAPPI, USA, or elemental analysis.
As a calculation method based on elemental analysis, specifically, an inductively coupled plasma emission analyzer (ICP-AES) is used to quantify the amount of phosphorus and divide by the molecular weight of phosphorus to obtain the number of moles per unit weight (for example, mmol). / G) can be converted.

<C1-C20 alkylcarbonyl group>
Specific examples of the alkylcarbonyl group having 1 to 20 carbon atoms include acetyl group, propionyl group, butyryl group, 2-butyryl group, pentanoyl group, hexanoyl group, heptanoyl group, octanoyl group, nonanoyl group, decanoyl group, undecanoyl group, Examples include dodecanoyl group, myristoyl group, palmitoyl group, stearoyl group, and pivaloyl group.

<C2-C6 alkenylcarbonyl group which may be substituted with an aryl group>
Specific examples of the alkenylcarbonyl group having 2 to 6 carbon atoms which may be substituted with an aryl group include an acryloyl group, a methacryloyl group and a cinnamoyl group.
<Alkynylcarbonyl group>
Examples of the alkynylcarbonyl group include a propioloyl group.

<Arylcarbonyl group>
Examples of the arylcarbonyl group include a benzoyl group and a naphthoyl group.
The method for introducing an alkylcarbonyl group having 1 to 20 carbon atoms, an alkenylcarbonyl group having 2 to 6 carbon atoms that may be substituted with an aryl group, an alkynylcarbonyl group, or an arylcarbonyl group is not particularly limited. There is a method of reacting a cellulose fiber raw material or cellulose fiber after defibration treatment with the following chemical modifier. Although there are no particular limitations on the reaction conditions, a solvent, a catalyst, or the like may be used, or heating, decompression, or the like may be performed as necessary.

As a kind of chemical modifier, the 1 type (s) or 2 or more types chosen from the group which consists of an acid, an acid anhydride, alcohol, and a halogenating reagent are mentioned.
Examples of the acid include acetic acid, acrylic acid, methacrylic acid, propanoic acid, butanoic acid, 2-butanoic acid, and pentanoic acid.
Examples of the acid anhydride include acetic anhydride, acrylic anhydride, methacrylic anhydride, propanoic anhydride, butanoic anhydride, 2-butanoic anhydride, and pentanoic acid.

Examples of the halogenating reagent include acetyl halide, acroyl halide, methacryloyl halide, propanoyl halide, butanoyl halide, 2-butanoyl halide, pentanoyl halide, benzoyl halide, and naphthoyl halide.
Among these, acetic anhydride, acrylic acid anhydride, methacrylic acid anhydride, benzoyl halide, and naphthoyl halide are particularly preferable.

These chemical modifiers may be used alone or in combination of two or more.
The amount of the alkylcarbonyl group having 1 to 20 carbon atoms, the alkenylcarbonyl group having 2 to 6 carbon atoms which may be substituted with an aryl group, the alkynylcarbonyl group and the arylcarbonyl group is introduced with respect to the total hydroxyl groups of cellulose. Usually, it is 2 mol% or more, preferably 3 mol% or more, usually 65 mol% or less, preferably 50 mol% or less, more preferably 40 mol% or less, and further preferably 35 mol% or less.

By introducing these groups, the heat resistance of cellulose is increased, and the physical property deterioration and coloring at high temperature are reduced. Etc. can also be performed.
Among these, a group having a cationic group, a group derived from phosphoric acid, or a group having an alkylcarbonyl group having 1 to 20 carbon atoms is preferable, among which a group having a cationic group, a group derived from phosphoric acid, an acetyl group, a propionyl group, or butyryl. Group is preferable, and a group having a cationic group and a group derived from phosphoric acid are more preferable.

In order to produce the modified cellulose fiber, as described above, for example, other groups are introduced into the hydroxyl group of cellulose by chemical or physical treatment on cellulose. The modification may be performed on the cellulose fiber raw material or may be performed on the cellulose fiber after the defibrating treatment.
It is preferable to perform a pretreatment such as an enzyme treatment or an acid treatment before modifying the cellulose fiber. By performing these treatments, the fiber length is shortened and the defibrating efficiency is improved.

(Pretreatment before denaturation)
Cellulase enzymes are preferably used for the enzyme treatment.
Cellulase enzymes are enzymes that cleave the β-1,4-glycoxide bond of cellulose by hydrolysis and cause depolymerization. In the present invention, any of endo-glucanase (EG) and cellobiohydrolase (CBH) can be used as the cellulase enzyme. Each may be used alone, or EG and CBH may be mixed and used. Moreover, you may mix and use a hemicellulase type enzyme.

The hemicellulase enzyme that can be used in the present invention is an enzyme that hydrolyzes hemicellulose. Among hemicellulase-based enzymes, xylanase, which is an enzyme that degrades xylan, mannanase, which is an enzyme that degrades mannan, and arabanase, an enzyme that degrades araban. In addition, pectinase, which is an enzyme that degrades pectin, can also be used as a hemicellulase-based enzyme.
Examples of the acid treatment include a method of heat-treating the cellulose fiber raw material with an acid such as hydrochloric acid or sulfuric acid.

<Cellulose fiber raw material>
In the present invention, the cellulose fiber raw material is obtained by removing impurities from a cellulose-containing material as shown below through a general purification process.

(Cellulose-containing material)
Examples of cellulose-containing materials include woods such as conifers and hardwoods (wood flour, etc.), cotton such as cotton linter and cotton lint, pomace such as sugar cane and sugar radish, bast fibers such as flax, ramie, jute and kenaf Vegetal vein fibers such as sisal and pineapple, petiole fibers such as abaca and banana, fruit fibers such as coconut palm, stem-derived fibers such as bamboo, bacterial cellulose produced by bacteria, seaweed and squirts such as valonia and falcon Natural cellulose such as encapsulates. These natural celluloses are preferable because of their high crystallinity and low linear expansion and high elastic modulus. In particular, cellulose fibers obtained from plant-derived materials are preferred.
Woods such as conifers and broad-leaved trees have fine fibers, are the largest biological resources on earth, and are sustainable resources that produce about 70 billion tons or more annually. The contribution to the reduction of carbon dioxide that affects the conversion is also significant, which is also advantageous from an economic point of view.

(Purification of cellulose-containing material)
The method for purifying the cellulose-containing material is not particularly limited. For example, the cellulose-containing material is degreased with benzene-ethanol or an aqueous sodium carbonate solution and then subjected to delignification treatment with a chlorite (Wise method), followed by dehydration with an alkali. It is obtained by treating with hemicellulose. In addition to the Wise method, a method using peracetic acid (Pa method), a method using a peracetic acid persulfuric acid mixture (Pxa method), and the like are also used as purification methods. Moreover, a bleaching process etc. are further performed suitably.

In the purification treatment, water is generally used as a dispersion medium. However, an aqueous solution of an acid or base or other treatment agent may be used, and in this case, it may be finally washed with water.
The cellulose fiber raw material may be obtained by a general method for producing chemical pulp, for example, a method for producing kraft pulp, salified pulp, antari pulp, or nitrate pulp.

That is, pulps such as hardwood kraft pulp, softwood kraft pulp, hardwood sulfite pulp, softwood sulfite pulp, hardwood bleached kraft pulp, softwood bleached kraft pulp, and linter pulp may be used as the cellulose fiber raw material.
In addition, as a raw material for cellulose fiber, CGP (Chemical Groundwood Pulp) or the like which is subjected to light chemical treatment with ground pulp, such as SGW (Stone Groundwood) or sodium sulfite, and then crushed, can be used. Groundwood pulp is preferably used.

In addition, the cellulose-containing material may be crushed into a state such as wood chips or wood powder, and this crushing may be performed at any timing before, during or after the purification treatment.
The degree of purification of the cellulose fiber raw material obtained by refining the cellulose-containing material is not particularly limited, but it is preferable that the fat content of the cellulose fiber raw material is less because the fat and oil and lignin are less and the cellulose component content is higher. The cellulose component content of the cellulose fiber raw material is preferably 80% by weight or more, more preferably 90% by weight or more, and still more preferably 95% by weight or more.

  The cellulose component of the cellulose fiber raw material can be classified into a crystalline α-cellulose component and an amorphous hemicellulose component. It is preferable that the content of crystalline α-cellulose is large because when a resin composition is obtained, the effects of low linear expansion coefficient, high elastic modulus, and high strength are easily obtained. The α-cellulose content of the cellulose fiber raw material is preferably 70% by weight or more, more preferably 75% by weight or more, more preferably 80% by weight or more.

Although the fiber diameter of the cellulose fiber raw material is not particularly limited, the number average fiber diameter is usually 1 μm to 1 mm. The number average fiber diameter of those that have undergone general purification is about 50 μm.
The number average fiber length of the cellulose fiber raw material is usually about 0.1 mm to 10 mm.

<Defibration of modified cellulose fiber>
The modified cellulose fiber used in the present invention can be used as it is after the modification treatment as described above, but obtains transparency, better mechanical properties, linear expansion coefficient, stability in water and drying shrinkage. Therefore, it is preferable to make fine cellulose by defibration. In order to efficiently obtain fine cellulose fibers by defibration, pretreatment may be performed.

  A specific method of the defibrating treatment is not particularly limited. For example, ceramic beads having a diameter of about 0.1 mm to 1 mm are made of cellulose fiber raw material concentration of 0.1 to 10% by weight, for example, about 1% by weight of cellulose. A method of defibrating a cellulose fiber raw material by putting it in a fiber raw material dispersion (hereinafter sometimes referred to as “cellulose fiber dispersion”) and applying vibration using a paint shaker or bead mill, etc., a grinder (stone mill grinding) And the like, and the like. In particular, these methods are effective for shortening the fiber length of cellulose fibers.

  In addition, as a dispersion medium of a cellulose fiber dispersion liquid, an organic solvent, water, or a mixed liquid of an organic solvent and water can be used. Examples of the organic solvent include alcohols such as methanol, ethanol, isopropyl alcohol, n-propyl alcohol, n-butanol, ethylene glycol, and ethylene glycol mono-t-butyl ether, ketones such as acetone and methyl ethyl ketone, and cyclic ethers such as tetrahydrofuran. In addition, one or more water-soluble organic solvents can be used. The dispersion medium is preferably a mixed liquid of an organic solvent and water or water, particularly water, because it can be more uniformly mixed with the polyvinyl alcohol resin.

  Defibration methods include a blender-type disperser and a high-speed rotating slit that uses a cellulose fiber dispersion to apply a shearing force (using a high-speed rotating homogenizer), or a sudden decrease in pressure from high pressure. By using a high-pressure homogenizer method, a method using a counter-impact type disperser such as “Masscomizer X (Masuyuki Sangyo)”, etc. Is mentioned. In particular, the efficiency of defibration is improved by adopting a treatment using a high-speed rotation type homogenizer or a high-pressure homogenizer.

In the case of defibration by these treatments, the solid content concentration as the cellulose fiber raw material is 0.1% by weight or more, preferably 0.2% by weight or more, particularly 0.3% by weight or more, and 10% by weight or less. It is preferable to perform a defibrating treatment on 6% by weight or less of the cellulose fiber dispersion. If the solid content concentration in the cellulose fiber dispersion to be subjected to the defibrating process is too low, the amount of liquid will be excessive with respect to the amount of cellulose fiber raw material to be processed, and the efficiency will be poor, and if the solid content concentration is too high, the fluidity will be poor. Therefore, the concentration of the cellulose fiber dispersion used for the defibrating treatment is adjusted by adding water as appropriate.

In addition, you may perform the fibrillation (miniaturization) process which combined the ultrasonic process after the process by such a high voltage | pressure homogenizer and the process by a high-speed rotation type homogenizer.
Moreover, after the defibrating treatment, cellulose fibers with poor defibration in the cellulose fiber dispersion may be separated and removed by using centrifugal separation. By separating and removing cellulose fibers with poor defibration in the cellulose fiber dispersion by centrifugation, a supernatant of a more uniform and finer fine cellulose fiber dispersion can be obtained, and the transparency of the cellulose fiber composite polyvinyl alcohol film is improved. The mechanical properties, linear expansion coefficient, drying shrinkage, and stability in water are improved. The conditions for centrifugation are not particularly limited because they depend on the defibrating treatment used, but it is preferable to apply a centrifugal force of, for example, 3000 G or more, preferably 10,000 G or more. Further, the centrifugation time is, for example, 1 minute or longer, preferably 5 minutes or longer. If the centrifugal force is too small or the time is too short, separation / removal of poorly defibrated cellulose fibers becomes insufficient, which is not preferable.

Further, when the centrifugal separation is performed, it is not preferable that the viscosity of the cellulose fiber dispersion is high because the separation efficiency is lowered. For this reason, as a viscosity of a cellulose fiber dispersion liquid, it is preferable that the viscosity in shear rate 10s- ¹ measured in 25 degreeC is 500 mPa * s or less, Preferably it is 100 mPa * s or less.

<Fiber diameter of modified cellulose fiber>
The number average fiber diameter of the modified cellulose fiber used for the cellulose fiber composite polyvinyl alcohol film of the present invention is preferably 20 nm or less, more preferably 15 nm or less, still more preferably 10 nm or less, and particularly preferably 8 nm or less. Further, the number average fiber diameter of the cellulose fibers is preferably as small as possible. However, in order to exhibit a high reinforcing effect, it is important to maintain the crystallinity of cellulose, and 2 nm or more is preferable. When the average fiber diameter of the cellulose fibers is less than the above lower limit value, the cellulose I-type crystal structure may not be maintained, and the strength and elastic modulus of the fibers themselves are lowered, and the reinforcing effect tends to be hardly obtained. In addition, when the average fiber diameter of the cellulose fibers exceeds the above upper limit value, the contact area with the polyvinyl alcohol-based resin becomes small, so that the reinforcing effect tends to be small and the transparency tends to deteriorate.

<Fiber length of modified cellulose fiber>
The number average fiber length of the modified cellulose fiber used for the cellulose fiber composite polyvinyl alcohol film of the present invention is preferably 1 μm or less, more preferably 900 nm or less, and still more preferably 800 nm or less. By setting the number average fiber length of the modified cellulose fibers within this range, the dispersibility of the modified cellulose fibers in the polyvinyl alcohol resin is improved. The number average fiber length of the cellulose fibers is preferably as small as possible, but considering the level-off polymerization degree of natural cellulose, it is preferably preferably 100 nm or more, more preferably 150 nm or more, and further preferably 200 nm or more. It is more preferable.

The number average fiber length and fiber diameter of the modified cellulose fibers used in the cellulose fiber composite polyvinyl alcohol film of the present invention are determined by drying and removing the dispersion medium in the cellulose fiber dispersion, and then using a scanning electron microscope (hereinafter “ "SEM"), transmission electron microscope (hereinafter sometimes referred to as "TEM"), atomic force microscope (hereinafter sometimes referred to as "AFM"), X-ray small angle scattering (hereinafter referred to as "SEM"). It may be referred to as “SAXS”. When measuring the number average fiber diameter of cellulose fibers with SEM, a line is drawn on the diagonal line of the SEM photograph magnified 30,000 times, and 12 fibers in the vicinity are extracted at random, the thickest fiber and the thinnest fiber. The average of the 10 measured values from which the fibers have been removed is taken as the number average fiber diameter. The cellulose fiber in the cellulose fiber composite polyvinyl alcohol film can also be measured and determined by removing the polyvinyl alcohol-based resin and observing in the same manner.

[Other ingredients]
The cellulose fiber composite polyvinyl alcohol film of the present invention is not limited to the polyvinyl alcohol film produced from the composition containing only the modified cellulose fiber and the polyvinyl alcohol-based resin. It is also preferable to produce a cellulose fiber composite polyvinyl alcohol film by forming a film by appropriately blending a surfactant, a plasticizer and the like. Moreover, a filler can also be mix | blended within the range which does not impair the objective of this invention.

<Surfactant>
The surfactant is blended for the purpose of improving the releasability between a metal surface such as a drum or belt which is a film forming apparatus for a polyvinyl alcohol film and the film formed.
Examples of the surfactant include nonionic surfactants such as polyoxyalkylene alkyl ethers, polyoxyalkylene alkyl phenyl ethers, polyoxyalkylene alkyl esters, sorbitan fatty acid esters, polyoxyalkylene alkyl amines, polyoxyalkylene alkyl amines, Examples include oxyalkylene alkylamides, polypropylene glycol ethers, acetylene glycols, and allyl phenyl ethers.

  In addition, anionic surfactants, cationic surfactants, and amphoteric surfactants may be used. Examples of the anionic surfactant include carboxylic acid types such as potassium laurate and sulfate ester types such as octyl sulfate. A sulfonic acid type anionic surfactant such as dodecylbenzenesulfonate is preferred. Examples of the cationic surfactant include amines such as laurylamine hydrochloride, quaternary ammonium salts such as lauryltrimethylammonium chloride, and pyridium salts such as laurylbiridinium chloride. Examples of amphoteric surfactants include N-alkyl-N, N-dimethylammonium betaine.

Surfactant can be used 1 type or in combination of 2 or more types.
About the compounding quantity of surfactant mix | blended with the said polyvinyl alcohol-type resin, what is necessary is just a grade which does not impair the objective of this invention, Moreover, the external appearance characteristic of film surfaces, such as bleeding out and the surface whitening, is carried out. The amount is not limited, and is usually 1 part by weight or less, preferably 0.8 part by weight or less, and particularly preferably 0.5 part by weight or less with respect to 100 parts by weight of the polyvinyl alcohol resin.

<Plasticizer>
The plasticizer is blended for the purpose of imparting flexibility to the film.
Examples of the plasticizer include glycerins such as glycerin, diglycerin, and triglycerin, and trihydric or higher polyhydric alcohols such as trimethylolpropane, mannitol, sorbitol, and pentaerythritol. These may be used alone or in combination of two or more.

  The blending amount of the plasticizer blended in the polyvinyl alcohol resin is preferably 10 parts by weight or less, more preferably 8 parts by weight or less, with respect to 100 parts by weight of the polyvinyl alcohol resin. When the blending amount of the plasticizer is too large, the film tends to become dull and difficult to handle, and further, it tends to cause a decrease in the appearance of the surface of the resulting decorative molded product, such as whitening. In addition, content of a plasticizer is suitably selected by the kind of plasticizer, For example, if it is glycerol with a high plasticizing effect, about 0.5-5 weight part is enough.

<Filler>
Examples of the filler include starch (not only various raw products but also etherified, oxidized and modified products), organic powders such as polymethyl methacrylate, inorganic powders such as talc, mica and silica. These may be used alone or in combination of two or more. Of these, starch is preferably used.

It is preferable that the compounding quantity of the filler mix | blended with the said polyvinyl alcohol-type resin is 20 weight part or less with respect to 100 weight part of polyvinyl alcohol-type resin, Most preferably, it is 15 weight part or less. If the blending amount of the filler is too large, the film strength tends to decrease in practical use.
Furthermore, as long as the effects of the present invention are not hindered, antioxidants (phenolic, amine-based, etc.), stabilizers (phosphate esters, etc.), coloring agents, fragrances, extenders, antifoaming agents, rust inhibitors, Other additives such as ultraviolet absorbers and other water-soluble polymer compounds (polyacrylic acid soda, polyvinylpyrrolidone, dextrin, chitosan, chitin, methylcellulose, hydroxyethylcellulose, etc.) may be appropriately blended.

  The cellulose fiber composite polyvinyl alcohol film of the present invention having the configuration as described above has excellent optical properties, good mechanical properties and linear expansion coefficient, small drying shrinkage and good underwater stability. In addition, it retains the properties of conventional polyvinyl alcohol films, that is, excellent properties such as hydrophilicity, water solubility, organic solvent resistance, gas barrier properties, etc., so optical films, various packaging materials, seed tapes, laminates for transfer It is not limited to the base film of the body, but may be used as a base film of a laminate for hydraulic transfer, and can also be used for conventionally known uses as other uses of the polyvinyl alcohol film.

[Method for producing cellulose fiber composite polyvinyl alcohol film]
Below, the manufacturing method of the cellulose fiber composite polyvinyl alcohol film of this invention is demonstrated.
First, the polyvinyl alcohol-based resin and, if necessary, a surfactant, a plasticizer, other additives and the like are blended in a predetermined blending amount and dissolved in water to prepare a polyvinyl alcohol-based resin aqueous solution. If necessary, in the case of a polyvinyl alcohol resin having a particularly high saponification degree, it is preferable to apply a temperature from room temperature to about 130 ° C. In preparing the aqueous polyvinyl alcohol resin solution, instead of dissolving it in water, it may be dissolved in the above-mentioned modified dispersion of cellulose fibers.

As a polyvinyl alcohol-type resin density | concentration in a polyvinyl-alcohol-type resin aqueous solution, it is preferable normally that it is 2-30 weight%, and it is especially preferable that it is 4-25 weight%. If the concentration is too low, the stability of the film thickness tends to decrease. If the concentration is too high, the viscosity tends to be high and film formation tends to be difficult.
Regarding the mixing of the polyvinyl alcohol-based resin aqueous solution and the dispersion of the above-described modified cellulose fiber, a general mixing method may be used, but it is preferable to mix them sufficiently so that they are uniformly mixed. If necessary, it is preferable to apply a temperature from room temperature to about 130 ° C. In the case of a polyvinyl alcohol resin having a high degree of saponification, it is also preferable to maintain a temperature at which the dissolved state of the polyvinyl alcohol resin is maintained from the mixing step to film formation.
The amount of the modified cellulose fiber in the mixed solution of the polyvinyl alcohol resin aqueous solution and the modified cellulose fiber dispersion is usually 0.1 parts by weight or more with respect to 100 parts by weight of the polyvinyl alcohol resin. , Preferably 0.2 parts by weight or more, particularly preferably 0.5 parts by weight or more. Further, it is usually 50 parts by weight or less, preferably 30 parts by weight or less, particularly preferably 20 parts by weight or less. When it is at least the above lower limit, the mechanical properties and underwater stability of the film become better, and the linear expansion coefficient and the drying shrinkage rate become smaller. Moreover, in the case of the upper limit or less, the optical properties of the film become higher.

The film formation is not particularly limited, and a general mixing method may be used.
For example, using an applicator on a PET film, glass, SUS plate, etc., a mixture of a polyvinyl alcohol-based resin aqueous solution and the above-mentioned modified cellulose fiber dispersion is applied, or is poured into a frame made of rubber or the like. Then, it is made into a film by drying and is further heat-treated as necessary.

At this time, it is preferable to apply a temperature to the substrate to be fluted as necessary. The drying temperature is usually preferably 20 to 150 ° C. Moreover, you may apply temperature in steps as needed.
After the drying, heat treatment may be performed as necessary. Examples of the heat treatment method include a hot roll (including a calender roll), hot air, far infrared rays, dielectric heating, and the like. It is preferable to perform the said heat processing normally at 50-130 degreeC, More preferably, it is 60-120 degreeC.

The film thickness of the modified cellulose fiber composite polyvinyl alcohol film of the present invention is preferably 10 to 100 μm, more preferably 10 to 80 μm, and particularly preferably 10 to 60 μm.
The cellulose fiber composite polyvinyl alcohol film of the present invention thus obtained has excellent optical properties, good mechanical properties and a linear expansion coefficient, low drying shrinkage and good underwater stability.

[Use of cellulose fiber composite polyvinyl alcohol film]
The cellulose fiber composite polyvinyl alcohol film of the present invention has excellent optical properties, good mechanical properties and linear expansion coefficient, small drying shrinkage and good underwater stability. Further, it retains the properties as a conventional polyvinyl alcohol film, that is, excellent properties such as hydrophilicity, water solubility, organic solvent resistance, and gas barrier properties. Therefore, the cellulose fiber composite polyvinyl alcohol film of the present invention can be used for optical films, various packaging materials, seed tapes, base films for laminates for transfer, base films for laminates for hydraulic transfer, and the like.

Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the description of the following examples unless the gist of the present invention is exceeded.
Moreover, the number average fiber diameter and number average fiber length of the cellulose fiber were measured as follows using an atomic force microscope (AFM).

<AFM>
Method: Atomic force microscopy (tapping mode)
Probe: Unmodified Si cantilever (NCH)
Environment: Room temperature and air (humidity about 50%)
Equipment: Digital Instrument Nanoscope III data sampling number manufactured by Bruker, Inc .: 512 × 512 point AFM type: Height image, phase image (to recognize each fiber)
Image analysis method: The fibers were traced from the AFM observation image, the fibers were extracted one by one, and the maximum value of the height of each fiber was measured as the fiber thickness. The measured values were averaged to obtain a number average fiber diameter. Further, the fiber length was measured from the observed image, and the fiber length distribution was determined.

(Production Example 1) Production of Cationized Cellulose Fibers 32.4 parts by weight of hardwood bleached kraft pulp (LBKP, manufactured by Oji Holdings Co., Ltd., solid content 30% by mass) as a cellulose fiber raw material was added to 250 parts by weight of 2-propanol, and then 5.83 parts by weight of a 1 mol / L aqueous sodium hydroxide solution and 4.86 parts by weight of an 80% by weight aqueous solution of glycidyltrimethylammonium chloride (Cathiomaster G (registered trademark), Yokkaichi Gosei Co., Ltd.) as a cationizing agent were added at room temperature. For 3 hours.

Thereafter, the temperature was raised to 50 ° C., and the cellulose fiber raw material and the cationizing agent were reacted for 90 minutes. After the reaction, the cake separated by filtration was dispersed in 600 parts by weight of desalted water, neutralized with a 10% by mass aqueous acetic acid solution, and then filtered again.
Next, the filtrate was washed with demineralized water until the electric conductivity of the filtrate was less than 50 μS / cm to obtain a cellulose fiber raw material into which a cationic group was introduced.

It was 0.43 mmol / g when the amount of cation groups of this fine cellulose fiber was measured according to JIS-K2609 using the nitrogen measuring device (TN-10, Mitsubishi Chemical Analytech make).
An aqueous dispersion containing 0.5% by mass of the cellulose fiber raw material into which this cationic group was introduced was prepared, and dissolved at 20000 rpm for 60 minutes using a high-speed rotating homogenizer (CLEAMIX-0.8S, manufactured by M Technique Co., Ltd.). Fiber processing was performed.

The aqueous dispersion was diluted to 0.2% by weight, and centrifuged at 38900 G for 30 minutes with a centrifuge (CR23 manufactured by Hitachi Koki Co., Ltd.) to recover the supernatant. (Cellulose fiber 1)
The obtained cellulose fiber 1 had a number average fiber diameter of 3.2 nm and a number average fiber length of 778 nm.

Production Example 2 Production of Phosphorylated Cellulose Fiber 6.75 g of sodium dihydrogen phosphate dihydrate and 4.83 g of disodium hydrogen phosphate were dissolved in 19.62 g of water to obtain a phosphorylating reagent aqueous solution. The pH of this phosphorylating reagent aqueous solution was 6.0 at 25 ° C.

As a cellulose fiber raw material, a conifer bleached kraft pulp (manufactured by Oji Holdings Co., Ltd., moisture 50%, Canadian standard freeness (CSF) 700 ml measured according to JIS P8121 (1995)) is 4% by weight. Add water to the plate and use a double disc refiner to add 250 ml with anomalous CSF (according to JIS P8121 (1995) except that plain mesh 80 mesh, pulp collection amount is 0.3 g) until the average fiber length is 0.68 mm. A pulp slurry was obtained by beating. After the obtained pulp slurry was diluted to 0.3% by weight, a pulp sheet having a moisture content of 90% (3 g as an absolute dry weight, thickness 200 μm) was obtained by a papermaking method. The pulp sheet was immersed in 31.2 g of the phosphorylating reagent aqueous solution (80.2 parts by weight as the amount of phosphorus element with respect to 100 parts by weight of the dried pulp), and then blown and dried at 105 ° C. (DKM400, manufactured by Yamato Scientific Co., Ltd.). ) For 1 hour, and further heat-treated for 1 hour with a blow dryer (DKM400, supra) at 150 ° C. to obtain a pulp sheet in which phosphoric acid was introduced into cellulose.

Next, 500 ml of ion-exchanged water was added to the pulp sheet into which phosphate groups had been introduced, and after stirring and washing, filtration and dehydration were performed to obtain dehydrated pulp. The obtained dehydrated pulp was diluted with 300 ml of ion-exchanged water, and 5 ml of 1N aqueous sodium hydroxide solution was added little by little with stirring to obtain a pulp slurry having a pH of 12 to 13. Thereafter, this pulp slurry was filtered and dehydrated, and washing with 500 ml of ion-exchanged water and filtration and dehydration were repeated a total of three times to finally obtain cellulose phosphate (cellulose fiber 2).
The number average fiber diameter of the obtained cellulose fibers 2 was 2.6 nm, and the number average fiber length was 665 nm.

<Introduction amount of phosphoric acid group>
The amount of phosphoric acid-derived groups introduced into the cellulose fiber 2 was calculated by applying TAPPI T237 cm-08 (2008). Specifically, in order to make it possible to calculate the introduction amount of phosphate groups introduced into cellulose over a wider range, among the test solutions used in the test method, sodium hydrogen carbonate (NaHCO ₃ ) / sodium chloride (NaCl) = The test solution in which 0.84 g / 5.85 g was dissolved and diluted in 1000 ml with distilled water was changed to a test solution in which 1.60 g of sodium hydroxide was dissolved and diluted in 1000 ml with distilled water. The calculation was performed according to TAPPI T237 cm-08 (2008) except that the difference in the calculated values was changed to a substantial substituent introduction amount (monovalent acidic group). Furthermore, in order to calculate the introduction amount of a phosphoric acid-derived group that is a polyvalent acidic group, the value obtained by dividing the obtained substituent introduction amount by the acid number of the phosphoric acid-derived group is introduced into the phosphoric acid-derived group. The amount.
The amount of phosphate group introduced, calculated according to this method, was 0.59 mmol / g.

Example 1
A 4% aqueous solution of polyvinyl alcohol (Nippon Synthetic Chemical NH-26) was prepared, and the cellulose fiber 1 prepared in Production Example 1 was mixed so as to be 1 part by weight with respect to 100 parts by weight of polyvinyl alcohol. Stir and mix for 1 hour. This mixed solution was filtered and degassed, and then poured into a silicon rubber frame mold placed on PET so that the film thickness became 70 μm. This was dried in a nitrogen stream at 30 ° C. for 5 hours, and further vacuum dried at 100 ° C. for 2 hours.
It was 96.7% when it evaluated by the area ratio of the film after drying with respect to the frame type | mold of the cellulose fiber composite polyvinyl alcohol film obtained in this way.

(Example 2)
A film was obtained in the same manner as in Example 1 except that the amount of cellulose fiber 1 to be added was 5.3 parts by weight with respect to polyvinyl alcohol.
It was 98.3% when it evaluated by the area ratio of the film after drying with respect to a frame type | mold.

(Comparative Example 1)
A film was obtained in the same manner as in Example 1 except that no cellulose fiber was added. When evaluated by the area ratio of the film after drying with respect to the frame mold, it was 84.0%.
The results of Examples 1 and 2 and Comparative Example 1 are shown in Table 1.

In addition, the haze measurement measured the haze value by C light source using the Suga Test Instruments haze meter.
From Examples 1 and 2 and Comparative Example 1, it was found that drying shrinkage was greatly improved by adding cellulose fibers. Moreover, it turned out that the improvement degree of dry shrinkage is so large that there is much quantity of the nanofiber cellulose to add.

(Example 3)
Polyvinyl alcohol (Nippon Synthetic Chemical NH-26) 13% by weight, ethylene glycol 1.8 parts by weight, water 85.2 parts by weight are mixed, put into a micro bomb, heated at 120 ° C. for 1 hour, transferred to a flask, 90 The mixture was stirred and mixed for 1 hour. The cellulose fiber 1 produced in Production Example 1 was mixed so as to be 1 part by weight with respect to 100 parts by weight of polyvinyl alcohol, and this was stirred and mixed at 90 ° C. for 1 hour. This mixed solution was filtered and defoamed, and applied on PET using an applicator so that the film thickness was 10 μm. This was dried in a nitrogen stream at 30 ° C. for 2 hours, and further vacuum dried at 100 ° C. for 2 hours. This film was cut into 30 mm × 15 mm, marked at intervals of 5 mm in the major axis direction, fixed at both ends with 4.9 g clips, and suspended on one side for a dimensional stability test in water. The rate of dimensional change was 50% at 30 seconds, 55% at 60 seconds, and 55% at 120 seconds.

Example 4
A 10 μm film was obtained in the same manner as in Example 3 except that the cellulose fiber 1 was changed to the cellulose fiber 2. When a dimensional stability test in water was performed in the same manner as in Example 3, the dimensional change rate was 30%, 52%, 55 seconds in 60 seconds, and 70% in 120 seconds.

(Comparative Example 2)
A 10 μm film was obtained in the same manner as in Example 3 except that no cellulose fiber was added. When a dimensional stability test in water was performed in the same manner as in Example 3, the dimensional change rate was 30 and 155%, 60 seconds was 190%, and 120 seconds was 200%.
The results of Examples 3 and 4 and Comparative Example 3 are shown in Table 2.

  From Examples 3 and 4 and Comparative Example 2, it can be seen that the dimensional stability in water is greatly improved by adding nanofiber cellulose.

(Example 5)
A 5% by weight aqueous solution of polyvinyl alcohol (Nippon Synthetic Chemical KH17) was prepared, and the cellulose fiber 1 prepared in Production Example 1 was mixed therewith so as to be 0.5 parts by weight with respect to 100 parts by weight of polyvinyl alcohol. This mixed solution was degassed and poured into a silicon rubber frame mold placed on PET so that the film thickness became 70 μm. This was dried at 60 ° C. for 4 hours.
When this film was cut into 3 mm × 30 mm and the linear expansion coefficient was measured, the value from 60 ° C. to 100 ° C. was 45 ppm / K.

<Measurement of linear expansion coefficient>
Using a thermomechanical analyzer (TMA “EXSTAR6000” manufactured by SII), the temperature profile is 25 ° C. → (5 ° C./minute temperature increase) → 100 in a tension mode with a chuck distance of 20 mm, a load of 98 mN, and a nitrogen gas atmosphere. The measurement was performed under the conditions of ° C (5 minutes hold) → (10 ° C / minute temperature drop) → -10 ° C → (5 ° C / minute temperature rise) → 180 ° C. The linear expansion coefficient was determined from the measured values of second run from 60 ° C to 100 ° C.

(Example 6)
A film was prepared in the same manner as in Example 5 except that the amount of cellulose fiber 1 added was 1 part by weight with respect to 100 parts by weight of polyvinyl alcohol, and the linear expansion coefficient was measured. The value was 30 ppm / K.

(Example 7)
A film was prepared in the same manner as in Example 5 except that the amount of cellulose fiber 1 added was 5.3 parts by weight with respect to 100 parts by weight of polyvinyl alcohol, and the linear expansion coefficient was measured. The value of ° C. was 25 ppm / K.

(Comparative Example 3)
A film was prepared in the same manner as in Example 5 except that the cellulose fiber 1 was not added, and the linear expansion coefficient was measured. The value from 60 ° C. to 100 ° C. was 115 ppm / K.

(Example 8)
A film was produced in the same manner as in Example 7 except that the polyvinyl alcohol used was N300 made by Nippon Synthetic Chemical Co., Ltd., and the linear expansion coefficient was measured. The value from 60 ° C. to 100 ° C. was 45 ppm / K. there were.

(Comparative Example 4)
A film was prepared in the same manner as in Example 8 except that the cellulose fiber 1 was not added, and the linear expansion coefficient was measured. The value from 60 ° C. to 100 ° C. was 85 ppm / K.
Table 3 shows the results of Examples 5 to 6 and Comparative Examples 3 and 4.

  It can be seen from Examples 5 to 8 and Comparative Examples 3 and 4 that the linear expansion coefficient is greatly improved by adding nanofiber cellulose.

Example 9
A 5% aqueous solution of polyvinyl alcohol (Nippon Synthetic Chemical N300) is prepared, and the cellulose fiber 1 prepared in Production Example 1 is mixed so as to be 5.3 parts by weight with respect to 100 parts by weight of polyvinyl alcohol, followed by filtration and defoaming. Then, the silicon rubber frame mold placed on PET was poured so that the film thickness became 70 μm. This was dried in a nitrogen stream at 30 ° C. for 5 hours, and further vacuum dried at 100 ° C. for 2 hours to produce a film. A 10 mm × 50 mm dumbbell was cut from this film, and a tensile test was performed with STA-1225 manufactured by ORIENTEC. The results are shown in Table 4.

(Comparative Example 5)
A film was prepared in the same manner as in Example 9 except that the cellulose fiber 1 was not added, a 10 mm × 50 mm dumbbell was cut, and a tensile test was performed. The results are shown in Table 4.

  From Example 9 and Comparative Example 5, it can be seen that the mechanical properties are greatly improved by adding nanofiber cellulose.

Claims (5)

A modified cellulose fiber composite polyvinyl alcohol film comprising a polyvinyl alcohol resin and a modified cellulose fiber having a repeating unit represented by the following general formula (1).
(Wherein X ₁ , X ₂ and X ₃ are each independently a group having a cationic group, a group derived from phosphoric acid, an alkylcarbonyl group having 1 to 20 carbon atoms, or an aryl group which may be substituted with an aryl group) Represents 2 to 6 alkenylcarbonyl groups, alkynylcarbonyl groups, or arylcarbonyl groups, provided that X ₁ , X ₂ , and X ₃ are not hydrogen atoms at the same time.) X ₁ , X ₂ and X ₃ in the general formula (1) are each independently a group having a cationic group, a group derived from phosphoric acid, or an alkylcarbonyl group having 1 to 20 carbon atoms. The modified cellulose fiber composite polyvinyl alcohol film described.   The modified cellulose fiber composite polyvinyl alcohol film according to claim 1 or 2, comprising 0.1 to 50 parts by weight of the modified cellulose fiber with respect to 100 parts by weight of the polyvinyl alcohol resin.   A modified cellulose fiber composite polyvinyl, characterized in that a polyvinyl alcohol resin and a composition containing a modified cellulose fiber having a number average fiber diameter of 20 nm or less and having a repeating unit represented by the general formula (1) are formed into a film. A method for producing an alcohol film. The manufacturing method of the modified cellulose fiber composite polyvinyl alcohol film of Claim 4 whose number average fiber length of the said modified cellulose fiber is 200 nm or more and 1 micrometer or less.