JP2003181859A - Method for manufacturing polyvinyl alcohol resin film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To manufacture a polyvinyl alcohol resin film without impairing an operating efficiency, such as film physical property and film making quality, which can be realized at the same level as when virgin polyvinyl alcohol resin powder is fully used, even when a reclaimed polyvinyl alcohol resin is partially recycled. <P>SOLUTION: When a mixture of the reclaimed polyvinyl alcohol resin film, a virgin polyvinyl alcohol resin and water is extrusion-molded and thereby, the polyvinyl alcohol resin film is manufactured, the grinds of the reclaimed polyvinyl alcohol resin film and the pulverized virgin polyvinyl alcohol resin are mixed. Especially, the grinds of the reclaimed polyvinyl alcohol resin with an average particle diameter of 1,000 μm or less and a moisture content of 10 wt.% or less is used. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention makes use of a polyvinyl alcohol resin film, which has become unnecessary in the film manufacturing process and the market, and is almost the same as when a new polyvinyl alcohol resin is used alone. The present invention relates to a method for producing a polyvinyl alcohol resin film having film properties and film properties.

[0002]

2. Description of the Related Art Films made from polyvinyl alcohol-based resins have been applied in various fields due to their excellent properties and variety of qualities. The film has excellent gas barrier properties, mechanical strength, transparency, gloss, etc.,
It is used in non-food fields such as food packaging, medical infusion bags, and agricultural chemical packaging materials.

In producing such a polyvinyl alcohol-based film, a method of melt-forming a water-containing polyvinyl alcohol-based resin in an extruder is often used in expectation of advantages such as high production rate. And
The obtained polyvinyl alcohol-based film is stretched if necessary.

In this method, a loss may occur at the start of operation or at the time of switching the type of product, a trimming film edge or a film edge may be generated, and a product film which is out of specifications due to a change in operating conditions may be generated. Further, even if the film is a product film supplied to the market, it may be required to dispose of the film after use.

Therefore, it is conceivable to recover the lost product as described above and to reuse the so-called recovered polyvinyl alcohol resin film. As one of such techniques, the applicant of the present invention discloses Japanese Patent Application Laid-Open No. 55-21214. Then, a method of extruding a hydrous polyvinyl alcohol resin mixture having a polyvinyl alcohol resin concentration of 40 to 60% by weight, which is a mixture of an aqueous solution of the recovered polyvinyl alcohol resin film and a new polyvinyl alcohol resin powder, into a film was proposed.

[0006]

However, in the above method, the recovered polyvinyl alcohol-based resin film is used as the total amount of the aqueous solution. Therefore, when the concentration is increased, the viscosity of the aqueous solution is increased to cause clogging of pipes and the new polyvinyl alcohol-based resin. A large amount of condition control is required for uniform compatibility with powder, and there is also a problem that may affect the quality of the film itself of the product. Decreasing the concentration of the aqueous solution of the recovered polyvinyl alcohol-based resin film in order to avoid such a problem defeats the original purpose of recycling the recovered material, and the economic merit is completely lost.

[0007]

[Means for Solving the Problems] However, as a result of diligent research conducted by the present inventors on such problems, a mixture of a recovered polyvinyl alcohol-based resin film, a new polyvinyl alcohol-based resin, and water is extruded to form a polyvinyl alcohol-based resin. In producing a resin film, when the recovered polyvinyl alcohol-based resin film is used as a crushed product and mixed with a new polyvinyl alcohol-based resin powder, the average particle size of the crushed product is 1000 μm or less and the water content is 10%.
It was found that a polyvinyl alcohol-based resin film can be obtained when the content of the polyvinyl alcohol-based resin powder is less than or equal to 10% by weight, without impairing work efficiency such as film physical properties and film-forming properties equivalent to the case where the entire amount of the new polyvinyl alcohol-based resin powder is used. Completed the invention.

Further, if such a polyvinyl alcohol resin film is biaxially stretched, preferable performances can be imparted in terms of mechanical strength, gas barrier property, water resistance, chemical resistance, heat resistance, releasability and the like. Is.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is described in detail below.
The polyvinyl alcohol resin used in the present invention may be either polyvinyl alcohol or modified polyvinyl alcohol, which is produced by homopolymerizing vinyl acetate and then saponifying it. The modified polyvinyl alcohol is produced by saponifying a copolymer of vinyl acetate and another unsaturated monomer, or by post-modifying polyvinyl alcohol.

Examples of the other unsaturated monomers mentioned above include ethylene, propylene, isobutylene, α-octene,
Olefins such as α-dodecene and α-octadecene, unsaturated acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, maleic anhydride, and itaconic acid, or salts thereof, mono- or dialkyl esters, acrylonitrile, methacrylonitrile, etc. Nitriles, amides such as acrylamide and methacrylamide, olefin sulfonic acids such as ethylene sulfonic acid, allyl sulfonic acid and methallyl sulfonic acid or salts thereof, alkyl vinyl ethers, N-acrylamidomethyl trimethyl ammonium chloride, allyl trimethyl ammonium chloride , Dimethyl allyl vinyl ketone, N-vinyl pyrrolidone, vinyl chloride, vinylidene chloride, polyoxyethylene (meth) allyl ether, polyoxypropylene (meth) allyl Polyoxyalkylene (meth) allyl ether such as ether, polyoxyethylene (meth) acrylate, polyoxyalkylene (meth) acrylate such as polyoxypropylene (meth) acrylate, polyoxyethylene (meth) acrylamide, polyoxypropylene (meth ) Polyoxyalkylene (meth) acrylamide such as acrylamide, polyoxyethylene (1- (meth) acrylamide-1,1-dimethylpropyl) ester, polyoxyethylene vinyl ether, polyoxypropylene vinyl ether, polyoxyethylene allylamine, polyoxypropylene Allylamine, polyoxyethylene vinylamine, polyoxypropylene vinylamine, etc. are mentioned.

Examples of the post-modification method include a method in which polyvinyl alcohol is esterified with acetoacetate, acetalized, urethaned, etherified, grafted, phosphoric esterified, and oxyalkylenated.

Among such polyvinyl alcohol resins, the saponification degree is preferably 90 to 100 mol%,
Furthermore, 95-100 mol% is preferable. When the degree of saponification is less than 90 mol%, the strength of the film tends to be poor, which is not preferable. The average degree of polymerization is preferably 500 to 4000, more preferably 1500 to 2800. If the average degree of polymerization is less than 500, the strength of the film is poor, and
If it exceeds 00, the film forming property is deteriorated, which is not preferable. The degree of saponification and the average degree of polymerization are measured according to JIS K 6726.

The recovered polyvinyl alcohol-based resin film used in the present invention is a trimming edge film, a film edge product, a lost product at the start of operation or product type change, a product film out of spec, an unnecessary disposal product in the market, etc. is there. Even if it is heat-treated, stretched, coated with various substances, or laminated with another resin, it can be used as long as it has water solubility.

In the present invention, the recovered polyvinyl alcohol-based resin film is mixed with the new polyvinyl alcohol-based resin powder as a crushed product. When preparing the crushed product, a rotary cutter crusher, a hammer crusher, and a ball are used. A well-known crusher such as a type crusher is used.

The average particle size of the crushed product is 1000 μm or less, preferably 700 μm or less, particularly preferably 10 to 700.
and a water content of 10% by weight or less, preferably 8
By adjusting to less than or equal to wt%, it is effective without blocking in storage or transportation, etc., without impairing work efficiency such as film physical properties and film-forming properties to the same extent as when using the entire amount of the new polyvinyl alcohol-based resin, A polyvinyl alcohol-based resin film can be manufactured. If the average particle size of the crushed product exceeds 1000 μm, the bulk specific gravity increases,
It becomes a problem in storage and transportation. Furthermore, if the water content of the crushed product exceeds 10% by weight, problems such as blocking occur during storage and transportation.

In the present invention, when a mixture of the recovered polyvinyl alcohol resin film, the new polyvinyl alcohol resin and water is obtained, the concentration of water or the resin content is 50% by weight or less, preferably 30% by weight or less. It is preferable that the aqueous solution in which the recovered polyvinyl alcohol-based resin film is dissolved, and the pulverized product of the recovered polyvinyl alcohol-based resin film and the new polyvinyl alcohol-based resin powder are mixed and dissolved. If the resin concentration of the aqueous solution exceeds 50% by weight, it takes too much time to dissolve, the piping is clogged, and the physical properties of the film are adversely affected.

The dissolving method for dissolving the recovered polyvinyl alcohol-based resin film in water is not particularly limited, and any method may be adopted. The recovered film may be used directly or the cut or crushed film may be dissolved in water in a dissolution tank equipped with a stirrer. Then, the mixture may be heated and stirred. After the dissolution operation is completed, the suspended solids and undissolved solids are filtered and removed using an ordinary filter.

In producing the polyvinyl alcohol-based resin film, the recovered polyvinyl alcohol-based resin film is mixed with the powder (including particles and pellets) of the new polyvinyl alcohol-based resin in the form of a crushed product.

Any mixing method may be used, but preferably, powders, particles and pellets of the new polyvinyl alcohol resin are first mixed with a pulverized product of the recovered polyvinyl alcohol resin film, and then in water or of the recovered polyvinyl alcohol resin film. Formulated in an aqueous solution. In some cases, the powder, particles, or pellets of the new polyvinyl alcohol resin are mixed with water or an aqueous solution of the recovered polyvinyl alcohol resin film, and then a pulverized product of the recovered polyvinyl alcohol resin film is mixed, or the new polyvinyl alcohol resin is mixed. It is also possible to simultaneously mix resin powder, particles, pellets, a pulverized product of the recovered polyvinyl alcohol-based resin film, water or an aqueous solution of the recovered polyvinyl alcohol-based resin film.

Upon mixing, 100 parts by weight or less, preferably 60 parts by weight or less, of a pulverized product of the recovered polyvinyl alcohol-based resin film is mixed with 100 parts by weight of the new polyvinyl alcohol-based resin. If the amount of the recovered polyvinyl alcohol-based resin film pulverized product exceeds 100 parts by weight, the physical properties of the film deteriorate.

As the mixing and dissolving device, a known kneading machine such as an extruder, a twin screw extruder, a three screw extruder, a continuous kneader or the like is used. It is advantageous to use a kneader with a vent to facilitate defoaming during dissolution. Also, after melting in a pressure melting pot or the like, it may be defoamed by the above kneader. The temperature at the time of melting is practically set to 50 to 270 ° C, preferably about 70 to 200 ° C.

Finally, as a stock solution for extrusion molding, a water-polyvinyl alcohol resin composition having a polyvinyl alcohol resin concentration of 10 to 60% by weight, preferably 25 to 55% by weight is prepared, and a film is formed. To be done. In addition, if necessary, the above-mentioned composition contains a colorant, a fragrance, a bulking agent, an antifoaming agent, a release agent, an ultraviolet absorber, an inorganic powder, a usual additive such as a surfactant, starch, carboxymethyl cellulose,
Other water-soluble resins such as methyl cellulose and hydroxymethyl cellulose may be appropriately blended.

The preparation of the water-polyvinyl alcohol resin composition and the film forming operation can be performed using the same extruder, but the L / D can be increased or a multi-screw extruder can be used. It is necessary to pay attention to uniform mixing and film formation stability such as using a gear pump.

The method for forming the polyvinyl alcohol-based resin film is not particularly limited, but after the above stock solution is supplied to an extruder and melt-kneaded, the T-die method (melt-extrusion method,
Melt casting method), an inflation method, and a blow molding method are preferably used to form a film by extrusion and then to dry it. The formed film is dried and commercialized. For such drying,
It is preferably carried out at 50 to 150 ° C, particularly 70 to 110 ° C.

In the present invention, not only the above-mentioned production of a single layer film of a polyvinyl alcohol resin film, but also a metal foil,
It is also possible to carry out extrusion coating on paper, plastic film and the like. Furthermore, in the present invention, the polyvinyl alcohol-based resin film may be subjected to any post-treatment such as stretching treatment, heat treatment, lamination with another substrate, water resistance treatment and embossing treatment.
Particularly in the present invention, it is also advantageous to further subject the obtained film to biaxial stretching, preferably sequential biaxial stretching, to impart physical properties such as mechanical strength, oxygen barrier property and infrared ray barrier property.

Regarding such stretching, the stretching ratio in the machine direction is 1.5 to 5.0 times, and the stretching ratio in the transverse direction is 2.0 to 4.
The draw ratio is preferably 0 times, more preferably 3.0 to 3.3 times in the longitudinal direction and 2.5 in the transverse direction.
~ 4.0 times. If the stretching ratio in the machine direction is less than 1.5 times, it is difficult to improve the physical properties by stretching, and if it exceeds 5.0 times, the film tends to tear in the machine direction, which is not preferable. Further, if the stretching ratio in the transverse direction is less than 2.0 times, it is difficult to improve the physical properties by stretching, and if it exceeds 4.0 times, it is difficult to industrially produce the film, which is not preferable.

In carrying out such sequential biaxial stretching,
The polyvinyl alcohol film has a water content of 5 to 5
It is preferable to adjust it to 0% by weight, preferably 20 to 30% by weight, and the polyvinyl alcohol-based film obtained before drying is continuously dried to adjust the water content, or the water content is less than 5% by weight. There is a method of adjusting the water content by immersing the polyvinyl alcohol-based film in (1) in water or subjecting it to humidity control.

If the water content is less than 5% by weight, the stretching ratio cannot be sufficiently increased, and if it exceeds 50% by weight, the film strength sufficient to increase the stretching ratio in the longitudinal and transverse directions cannot be obtained in the same manner in the stretching process. Not preferable.

Further, it is preferable to carry out heat setting after successive biaxial stretching, and the temperature of such heat setting is selected from the melting point of the polyvinyl alcohol resin or a temperature lower than the melting point by 40 ° C. Is preferred. If the temperature is lower than 40 ° C. lower than the melting point, the dimensional stability is poor and the shrinkage ratio becomes large, while if it is higher than the melting point, the thickness variation of the film becomes large, which is not preferable. When the polyvinyl alcohol-based resin is a saponified product of a vinyl acetate homopolymer, the heat setting temperature is, for example, 160 to 230 ° C. The heat setting time is preferably 1 to 30 seconds,
More preferably, it is 5 to 10 seconds.

The stretched film obtained can be used as it is, or by coating the surface thereof with another resin or laminating it with another resin, for various uses including food packaging.

[0031]

EXAMPLES The present invention will be specifically described below with reference to examples. In the examples, "part" and "%" mean weight basis unless otherwise specified.

Example 1 Preparation of a pulverized product of recovered polyvinyl alcohol-based resin film Polyvinyl alcohol having a polymerization degree of 1700 and a saponification degree of 99.7 mol% (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., “Gothenol N”).
H-17Q ") film (thickness 14 μm, moisture content 3)
%) Was pulverized in two stages by a rotary cutter type pulverizer to obtain a pulverized product having an average particle size of 600 μm. Preparation of aqueous solution of recovered polyvinyl alcohol resin film
Manufacture The crushed product was supplied into water in a dissolution tank, heated to a temperature of 98 ° C. and completely dissolved over 6 hours to prepare a polyvinyl alcohol aqueous solution having a concentration of 18%, and filtered to remove impurities.

Production of polyvinyl alcohol resin film
From the hopper of the twin-screw extruder type kneader (screw L / D = 40) with the jacket temperature set to 60 to 150 ° C., a new polyvinyl alcohol with a water content of 3% and an average particle size of 900 μm (polymerization degree 1700, saponification degree) 99.7 mol%, "Gohsenol NH-17Q" manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) 10
A powder composition in which 50 parts of the above-mentioned pulverized product was mixed with 0 part was supplied at a rate of 200 kg / hr, and the polyvinyl alcohol aqueous solution was fed from the hopper in the screw advancing direction side at a rate of 300 kg / hr. It is supplied at a rate of hr, kneaded at a temperature of 90 to 120 ° C., and the discharge amount is 50.
It was discharged under the condition of 0 kg / hr. Immediately, this discharge product was pressure fed to a single-screw extruder (screw L / D = 30) and the temperature was adjusted to 85
After kneading at ˜140 ° C., it was extruded from a T-die to a cast roll at 5 ° C. and dried for 30 seconds with a hot air dryer at 90 ° C. to prepare a film (A) having a water content of 25% (thickness 150 μm). Subsequently, the film (A) was stretched 3 times in the longitudinal direction, and then stretched 3 times in the transverse direction with a tenter, and then 2
The film was heat set at 20 ° C. for 8 seconds to obtain a biaxially stretched film (B) (thickness 14 μm).

Tensile strength, fish film
, Oxygen permeability, water vapor permeability, recyclability
evaluated. The results are shown in Table 1. The evaluation method was as follows. Tensile strength: Tensile strength (MP
a) was measured. Test piece is 15mm x 200mm, test
The speed was 200 mm / min. Fish eye: 1m film²Diameter 1 observed inside
Measure the number of resin lumps of mm or more and evaluate according to the following criteria
It was ○: 1 or less ×: 2 or more Oxygen permeability: JIS K7126 B method (isobaric method)
"Method of testing gas permeability of plastic films and sheets
Oxygen permeability (cc / m ²・ D
ay) was measured. Water vapor permeability: JIS Z0208 (cup method) "prevention
20 ℃ × 6 in accordance with “Permeability test method for wet packaging materials”
Water vapor permeability at 0% RH and 20 ° C x 90% RH
(G / m²-Day) was measured. Recyclability: evaluated according to the following criteria. ◎ ・ ・ ・ Waste from the production line and from the market
Can be collected and recycled ○ ・ ・ ・ Collection and recycling of waste from the production line
can do ×: Collecting and recycling waste from the production line
Can not do it

Example 2 The same experiment as in Example 1 was carried out except that the recovered polyvinyl alcohol was used in Example 1 except that the average particle size of the ground product was changed to 700 μm and the water content was changed to 5%. The results are shown in Table 1.

Example 3 The same experiment as in Example 1 was carried out except that the recovered polyvinyl alcohol in which the average particle size of the ground product was changed to 500 μm and the water content was changed to 2% was used. The results are shown in Table 1.

Example 4 The same experiment as in Example 1 was carried out except that the aqueous solution of the recovered polyvinyl alcohol-based resin film was changed to water. The results are shown in Table 1.

Comparative Example 1 The same experiment as in Example 1 was carried out except that only new polyvinyl alcohol was used. The results are shown in Table 1.

[0039]   [Table 1]           Film Tensile Strength Fish Eye Oxygen Steam Recycle                (MPa) Permeability Permeability Appropriate                                 (cc / m²・ Day) (g / m²・ Day) Example 1 (A) ――― ○ ――― --- ---           (B) 240 ○ 0.2 <0.1 52 ◎ Example 2 (A) ――― ○ ――― --- ---           (B) 235 ○ 0.2 <0.1 50 ○ Example 3 (A) ――― ○ ――― --- ---           (B) 240 ○ 0.3 <0.1 53 ◎ Example 4 (A) ――― ○ ――― --- ---(B) 240 ○ 0.2 <0.1 50 ○ Comparative Example 1 (A) ――― ○ ――― --- ---(B) 240 ○ 0.2 <0.1 51 ×

[0040]

In the present invention, when a mixture of a recovered polyvinyl alcohol resin film, a new polyvinyl alcohol resin and water is extrusion-molded to produce a polyvinyl alcohol resin film, the recovered polyvinyl alcohol resin film is crushed. As a product, when mixed with new polyvinyl alcohol-based resin powder, especially when the average particle size of the crushed product is 1000 μm or less and the water content is 10% by weight or less, the same as when the entire amount of new polyvinyl alcohol-based resin powder is used A polyvinyl alcohol-based resin film can be obtained without impairing work efficiency such as film physical properties and film-forming properties.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) B29L 7:00 B29L 7:00 C08L 29:04 C08L 29:04 F term (reference) 4F071 AA29 AH01 AH04 AH19 BA01 BB06 BC01 4F205 AA19 AA50 AC05 AG01 GA07 GB02 GC01 GE24 GF01 GF51 4F207 AA19 AA50 AG01 KA01 KA17

Claims (5)

[Claims] 1. When a mixture of a recovered polyvinyl alcohol-based resin film, a new polyvinyl alcohol-based resin, and water is extrusion-molded to produce a polyvinyl alcohol-based resin film, the recovered polyvinyl alcohol-based resin film is used as a crushed product. A method for producing a polyvinyl alcohol-based resin film, which comprises mixing with a polyvinyl alcohol-based resin powder. 2. The method for producing a polyvinyl alcohol-based resin film according to claim 1, wherein the crushed product of the recovered polyvinyl alcohol-based resin film has an average particle diameter of 1000 μm or less. 3. The method for producing a polyvinyl alcohol resin film according to claim 1, wherein the pulverized product of the recovered polyvinyl alcohol resin film has a water content of 10% by weight or less. 4. An aqueous solution in which a recovered polyvinyl alcohol-based resin film is dissolved so that a resin content concentration is 50% by weight or less, a pulverized product of the recovered polyvinyl alcohol-based resin film and a new polyvinyl alcohol-based resin powder are mixed and dissolved. The method for producing a polyvinyl alcohol-based resin film according to any one of claims 1 to 3, wherein 5. The method for producing a polyvinyl alcohol resin film according to claim 1, further comprising biaxial stretching.