JP2008074955A - Wrap film of polyvinylidene chloride-based resin - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wrap film of a polyvinylidene chloride-based resin obtained by achieving both of reduction of smell and suppression of thermal decomposition, hardly causing the change of properties with time such as excess adhesion phenomenon of the film and the reduction of taking-out properties, and having properties of stabilizing extrusion characteristics caused by the change of torque or the like. <P>SOLUTION: The wrap film of the polyvinylidene chloride-based resin is obtained by formulating as a stabilizer 0.2-3.0 wt.% of an epoxidized soybean oil produced by a hydrogen peroxide method and having ≤13 peroxide value. The remaining rate of the vinylidene chloride in the raw material of the vinylidene chloride-based resin composition is 0.01-1 ppm, and the ring-opening rate of the epoxy in the epoxydized soybean in the film after film formation is ≤50%. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention is a wrap film used for simple packaging of foods and the like. Specifically, 0.2 to 3.0 weight of epoxidized soybean oil produced by the hydrogen peroxide method and having a peroxide value of 13 or less. Epoxy resin, which is a conventional polyvinylidene chloride resin wrap film produced by blending the resin, and having a residual vinylidene chloride monomer content of 0.01 to 1 ppm in the raw material polyvinylidene chloride resin composition. Overcome the odor of oxidised soybean oil, and suppress thermal decomposition by keeping the epoxy ring opening rate of epoxidized soybean oil in the film after film production within 50%. By defining the total addition amount to 4.0 to 10.0% by weight, there is little change over time in physical properties such as over-adhesion phenomenon of the film and a decrease in the drawability, and the property is such that the extrusion characteristics such as torque fluctuation are stable. On fluoride resin wrap film.

Conventionally, a polyvinylidene chloride-based resin wrap film is excellent in properties such as adhesion and gas barrier properties, and thus has been used in many general households as a simple packaging material for foods and the like.
In the inflation film-forming method (see FIG. 1), which is a widely used production method for producing a polyvinylidene chloride-based resin wrap film, a resin composition extruded into a tube from a die is cooled with water on the outside, a die mouth and a pinch The inside sandwiched between the rolls is molded by passing it through a known refrigerant such as mineral oil and cooling and solidifying. A cylindrical portion sandwiched between the inner die opening and the pinch roll at this time is called a sock, and the refrigerant sealed in this part is called a sock liquid. An annular double ply sheet folded with a pinch roll is called a parison. Further, the parison is stretched by reheating and blowing air into the interior (inflation). The obtained double-ply film is slit and peeled to form a single film. Finally, it is wound on a paper tube to obtain a paper tube-wrapped wrap film.

Here, the polyvinylidene chloride-based resin composition refers to a polyvinylidene chloride-based resin containing all additives including stabilizers and plasticizers suitable for extrusion molding. Moreover, a polyvinylidene chloride type | system | group resin wrap film shows the wrap film manufactured using the polyvinylidene chloride type | system | group resin composition.
In order to obtain good processability and good physical properties as an additive in the resin composition used at this time, for example, epoxidized soybean oil (hereinafter referred to as ESO) as a stabilizer to a polyvinylidene chloride resin. It is known to add, for example, acetyltributyl citrate (hereinafter referred to as “ATBC”), acetylated monoglyceride (hereinafter referred to as “ACGL”), or the like as an epoxidized vegetable oil or plasticizer represented by the above.

  ESO, which has existed as a stabilizer in the past, is produced by epoxidizing soybean oil produced in nature with an oxidizing agent such as hydrogen peroxide or peracetic acid. When peracetic acid is used as the oxidizing agent, Although there is little peculiar odor when hydrogen peroxide is used as an oxidizing agent, there is a problem that acetic acid odor derived from the oxidizing agent is large. On the other hand, ESO produced by the hydrogen peroxide method has an odor peculiar to the production method due to low-boiling substances such as aldehydes and ketones produced at the time of production, and the same applies when this is used for food packaging materials. There was a problem of generating odor. In any case, ESO generates a lot of odors derived from the substance, and particularly when used for food contact applications, the odor of the film itself, the transfer of odors to foods, and the like are problems, and it has not been able to withstand use.

In order to solve the problem, Patent Document 1 proposes epoxidized linseed oil (hereinafter referred to as ELO) instead of ESO, and has been widely used for food packaging wrap films. However, although ELO certainly does not have a problem of odor, it bleeds out to the surface of the film with time and affects the adhesion, so if the temperature history is excessive, the excessive adhesion phenomenon of the film and the drawability associated therewith Changes in physical properties over time, such as a significant decrease, are serious, and there has been a strong demand for a solution to this problem in order to improve the usability of wrap films.
However, in recent years, as described in Patent Document 2, in ESO produced by a method using hydrogen peroxide as an oxidizing agent (hydrogen peroxide method), in particular, by limiting the peroxide value of ESO to 13 or less. Odor can be suppressed even after molding. This makes it possible to use this ESO for food packaging wrap films. Compared to conventional ESO (peracetic acid method), the wrap film produced using this ESO has made it possible to dramatically reduce its odor. The odor peculiar to the law remained, and the required physical properties could not be satisfied especially for consumers sensitive to the odor.

Japanese Patent Application No. 37-43570 Japanese Patent No. 278618

  The present invention overcomes the odor of ESO, which has been a problem in the prior art, and suppresses thermal decomposition. Furthermore, there is little change over time in physical properties such as excessive adhesion of the film and a decrease in drawability, and torque. An object of the present invention is to provide a polyvinylidene chloride resin wrap film having stable physical properties such as fluctuations in extrusion characteristics.

  As a result of intensive studies from the viewpoint of achieving both contradictory problems of odor generation and thermal decomposition suppression, the present inventors have selected and used a specific stabilizer to be added to the polyvinylidene chloride resin composition By limiting the amount, and further by limiting the drying conditions, it is possible to reduce the odor to a level that satisfies the demands of consumers, and to suppress thermal decomposition. The present inventors succeeded in obtaining a polyvinylidene chloride resin wrap film having little physical property change over time, such as a decrease in drawability, and stable physical properties such as torque fluctuation.

That is, the present invention is as follows.
[1] A polyvinylidene chloride resin wrap film comprising 0.2 to 3.0% by weight of epoxidized soybean oil produced by a hydrogen peroxide method and having a peroxide value of 13 or less as a stabilizer. The residual amount of vinylidene chloride monomer in the raw material polyvinylidene chloride resin composition is 0.01 to 1 ppm, and the epoxy ring opening rate of the epoxidized soybean oil in the film after film production is within 50%. A polyvinylidene chloride-based resin wrap film.
[2] The polyvinylidene chloride resin wrap film of [1], wherein the total amount of additives added to the polyvinylidene chloride resin is 4.0 to 10.0% by weight.

  By the present invention, it is possible to overcome odor and suppress thermal decomposition. Furthermore, there is little change with time in physical properties such as excessive adhesion phenomenon of the film and lowering of drawability, and stable extrusion characteristics such as torque fluctuation. A polyvinylidene chloride resin wrap film having the above-mentioned physical properties can be obtained.

Hereinafter, the present invention will be described in detail.
The most different point of the present invention from the prior art is that 0.2 to 3.0% by weight of ESO produced by the hydrogen peroxide method and having a peroxide value of 13 or less as a stabilizer in polyvinylidene chloride resin. A polyvinylidene chloride-based resin wrap film formed by removing the residual amount of vinylidene chloride monomer in the raw material polyvinylidene chloride-based resin composition from 0.01 to 1 ppm, and an epoxy in the film after film production The epoxy ring opening rate of the modified soybean oil is within 50%.
If the amount of ESO added is less than 0.2% by weight, the effect of stabilizing the resin by ESO is too small, the resin undergoes thermal degradation during extrusion, and the film becomes yellowed and brittle, resulting in 3.0% by weight. If it exceeds 50%, the odor generated from the ESO main body becomes a problem although the resin stabilizing effect of ESO is sufficient. Therefore, the ESO addition amount is preferably 0.2 to 3.0% by weight, more preferably 0.8 to 1.5% by weight.

At the same time, the residual amount of vinylidene chloride monomer in the raw material resin composition is removed by drying to 0.01 to 1 ppm. At the same time, for example, aldehydes such as n-butyl ether, toluene and hexanal, esters such as butyl butanoate, and various lower carbonizations Low boiling components derived from ESO such as hydrogen can also be removed. Thus, by removing the causative substance as much as possible from the raw material resin composition in advance, the odor of ESO, which has been a problem in the past, can be dramatically reduced even in a wrap film after molding. However, if the drying conditions are strict, low boiling components derived from ESO can be further reduced, but on the other hand, the deterioration of the resin progresses due to the strict drying conditions, and other problems such as film coloring after film production occur. For this reason, the residual amount of vinylidene chloride monomer in the raw material resin composition is preferably 0.01 to 1 ppm, and more preferably 0.02 to 0.3 ppm. As an example of drying at this time, a condition of about 3 hours at a set temperature of 70 to 90 ° C. and an air volume of 35 to 40 m ³ / hr by a fluid dryer can be mentioned.

Furthermore, in order to keep the ESO epoxy ring-opening ratio within 50% of the film after film production, it is specifically stabilized at a set temperature of 165 to 175 ° C. in an extruder designed to suppress resin retention as much as possible. This makes it possible to suppress thermal degradation of the resin during extrusion by ESO, and as a result, to suppress film coloring and embrittlement over time after film formation. When the epoxy ring-opening rate exceeds 50%, film coloring and embrittlement over time becomes remarkable, and the physical properties of the resulting wrap film do not satisfy the requirements.
By satisfying these conditions, the resulting wrap film overcomes odor and suppresses thermal decomposition, and further changes over time in physical properties such as excessive adhesion of the film and reduction in drawability. There are few extrusion characteristics such as torque fluctuation and stable physical properties.

  In addition, by making the total amount of the additive containing ESO 4.0 to 10.0% by weight, it is possible to reduce changes in physical properties over time, such as excessive adhesion of the film due to additive bleed-out, and torque. Extrusion characteristics such as fluctuations can also be stabilized. When the total addition amount is less than 4.0% by weight, the plasticizing effect of the resin is small, the extrusion stability and stretchability are remarkably inferior, and a stable film cannot be formed. If it exceeds 10.0% by weight, the opening property of the parison deteriorates, and at the same time, changes in physical properties with time, such as an excessive adhesion phenomenon of the film due to bleeding out of the additive from the resin and a decrease in the drawability, become large. Therefore, the total addition amount is preferably 4.0 to 10.0% by weight, more preferably 5.0 to 8.0% by weight.

Hereinafter, an example of a method for producing the film of the present invention will be described.
Drawing 1 is a schematic diagram of an example of a manufacturing process of a wrap film.
First, the melted vinylidene chloride copolymer composition is extruded into a tubular shape from a die (2) by an extruder (1) to form a sock (4). The outside of the sock (4) is brought into contact with cold water in the cold water tank (6), and the sock liquid (5) is injected into the inside of the sock (4), so that it is cooled and solidified from the inside and outside. The solidified sock (4) is folded by a first pinch roll (7) to form a parison (8).

Subsequently, by injecting air into the inside of the parison (8), the parison (8) is opened again and becomes tubular. At this time, the sock liquid (5) applied on the inner surface of the sock (4) exhibits the effect of the parison (8) as an opening agent. The parison (8) is reheated to a temperature suitable for stretching with warm water. The warm water adhering to the outside of the parison (8) is squeezed out by the second pinch roll (9). Air is injected into a tubular parison (8) heated to an appropriate temperature to form bubbles (10), and a stretched film is obtained. Thereafter, the stretched film is folded by the third pinch roll (11) to form a double-ply film (12). The double ply film (12) is wound up by a winding roll (13). Further, the film is slit and peeled off to become a single film. Finally, the film is wound on a paper tube to obtain a paper tube-wrapped wrap film.

The polyvinylidene chloride resin used in the present invention contains 85 to 97 wt% of vinylidene chloride units. In addition to vinylidene chloride, for example, acrylic acid esters such as vinyl chloride, methyl acrylate and butyl acrylate, methacrylic acid esters such as methyl methacrylate and butyl methacrylate, acrylonitrile, vinyl acetate and the like, which can be copolymerized with vinylidene chloride or Two or more monomers may be copolymerized.
As long as the effect of the present invention is not impaired, the resin may be a plasticizer, a stabilizer, a weather resistance improver, a colorant such as a dye or a pigment, an antifogging agent, an antibacterial agent, and the like used in known food packaging materials. A lubricant, a nucleating agent, an oligomer such as polyester, a polymer such as MBS, or the like may be added.

The thickness of the wrap film of the present invention is not particularly limited, but is generally 5 to 20 μm.
The film of the present invention is obtained by, for example, uniformly mixing a polyvinylidene chloride resin and various additives with a ribbon blender, a Henschel mixer or the like as necessary, aging for 24 hours, and then melt-extruding the resin composition. , Obtained by inflation stretching. As long as the effect of the present invention is not impaired, the resin may be a plasticizer, a stabilizer, a weather resistance improver, a colorant such as a dye or a pigment, an antifogging agent, an antibacterial agent, and the like used in known food packaging materials. A lubricant, a nucleating agent, an oligomer such as polyester, a polymer such as MBS, and the like can also be added. These may be added at any stage until film formation. The wrap film obtained by the above-mentioned method has better adhesion immediately after production, has stable adhesion with little seasonal difference between summer and winter, and has high adhesion and excellent drawability. A wrap film having both contradictory and improved characteristics can be obtained.

EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention concretely, this invention is not limited at all by these.
Evaluation methods used in Examples and Comparative Examples are as follows.
(Evaluation methods)
(1. Thermal degradability)
A 20-m roll wrap film immediately after film formation is cut out, and the degree of deterioration coloring (b value) is measured and evaluated with a colorimetric color difference meter (transmission) according to JIS Z8722.
Evaluation symbol b value Judgment ○ Less than 2.5 The degree of coloring is small and the degree of coloring is small × 2.5 or more The degree of coloring is large because the thermal deterioration is not suppressed

(2. Extrusion torque fluctuation)
Evaluate the fluctuation of the torque during extrusion over time (after 2 hours).
Evaluation symbol Judgment ○ Torque fluctuation value is stable within a certain range × Torque fluctuation value is rising, falling, or fluctuating

(3. Parison opening)
The opening property of the obtained parison is evaluated from the viewpoint of stretching propagation.
Evaluation symbol Judgment ○ The parison is fully open at the position where the second pinch roll comes out △ The end of the parison is not fully opened at the position where the second pinch roll comes out
There is a fused part. × The parison opens completely, always fused from the position immediately after the second pinch roll.
Absent

(4. Film odor)
The ESO odor of the film after film formation is evaluated by sensory evaluation.
Evaluation symbol Judgment ○ Level at which people who are sensitive to odors do not care at all

(5. Residual amount measurement of vinylidene chloride monomer)
The residual amount of vinylidene chloride monomer is measured as an index for removing low-boiling components that cause ESO-derived odors remaining in the wrap film.
Place 5 g of polymer sample into a vial and cover with septum and aluminum cap. A vial tube was set in the heating device and kept warm at 100 ° C. for 60 minutes. After completion of the holding conditions, 0.8 ml of the gas phase portion of the vial tube was sampled, placed in a gas chromatograph, and detected and analyzed by FID.
Evaluation symbol Remaining monomer amount ○ 0.01 or more and less than 1.0 Drying conditions are good, resin does not deteriorate, and low boiling point components
Removed sufficiently × Less than 0.01 Drying conditions are harsh and resin degradation is progressing
1.0 or more Drying conditions are insufficient and low boiling point components can be removed.
Not in

(6. ESO / ELO: epoxy ring-opening ratio measurement)
The ring opening rate of the epoxy group in the epoxidized vegetable oil is measured as an index of capturing hydrochloric acid generated during the thermal decomposition of the resin of the epoxidized vegetable oil added to the wrap film.
3 g of the film sample was reprecipitated in THF / methanol, and the reprecipitated filtrate was concentrated and dried, then made up to 5 ml with chloroform, and the epoxidized vegetable oil component was fractionated with a large volume preparative GPC.
The separated product of ¹ H-NMR analysis was (256 times integration), preparative product and the standard sample (epoxidized vegetable oil), respectively, and 2.2～2.4Ppm (lateral CH ₂ groups of the ester) 2.8 The ring opening rate of the epoxy group was determined from the ratio of 3.3 ppm (CH group with an epoxy).

(7. Evaluation of excessive adhesion)
The adhesion work after the film formation at 28 ° C. for 1 month is evaluated. First, ^two aluminum cylindrical jigs having a bottom area of 25 cm ² , a height of 55 mm, and a weight of 400 g were prepared, and filter paper having the same shape as the bottom surface was attached to the bottom surfaces of both jigs. A wrap film was placed on the bottom surface of the jig with the filter papers on both sides so that no wrinkles would enter, and it was fixed with rubber bands. The two jigs covered with the wrap film were put together so that the surfaces on the side covered with the wrap film were perfectly overlapped, and pressed with a load of 500 g for 1 minute. Next, the work required to peel the wrap film surfaces from each other in the direction perpendicular to the surfaces was measured at a speed of 5 mm / min with a tensile and compression tester (unit mJ / 25 cm ² ). This measurement was performed in an atmosphere of 23 ° C. and 50% RH.

The adhesion of the wrap film was determined by evaluating the following three stages based on the measured adhesion work.
<Work of adhesion after storage at 28 ° C for 1 month>
Evaluation symbol Work (mJ) Judgment ○ 2.0 or more and less than 2.5
Excellent level △ 2.5 or more and less than 3.2 Adhesiveness is too high, handling is inferior × 3.2 or more Adhesiveness is too high, handling is remarkable
Inferior When the adhesion work amount is 2.5 mJ or more, it is judged that the adhesion is too high and the handling property is inferior, and that it is in the excessive adhesion region.

(8. Overall evaluation)
Based on these evaluation results, a comprehensive evaluation is performed.
[Example 1]
Polyvinylidene chloride resin having a weight average molecular weight of 90,000 (90% by weight of vinylidene chloride component and 10% by weight of vinyl chloride component), ATBC, and ESO manufactured by the hydrogen peroxide method (Newsizer 510R, Nippon Oil & Fat Co., Ltd.) )) Are mixed at a ratio of 93.0% by weight, 5.5% by weight and 1.5% by weight (total added amount 7.0% by weight), respectively, and a drying temperature of about 80 ° C. After drying with a fluid dryer (remaining vinylidene chloride monomer amount: 0.09 ppm) under conditions of an air volume of 35 to 40 m3 / hr and a residence time of 3 hours, it was extruded into a tube at an extrusion rate of 300 kg / hr, and water at 10 ° C. It solidified quickly. At this time, a mixture of (Smoyl P-70S, Matsumura Oil Research Co., Ltd.) and water was poured into the formed sock to obtain a sock solution. Furthermore, after heating with warm water of 45 ° C., it is stretched by an inflation method to form a tubular film, and this tubular film is pinched and folded flat, and a two-layer film having a folding width of 1,900 mm and a thickness of 10 μm is wound. The film was wound at a take-up speed of 100 m / min to obtain a stretched film. The results of evaluation based on the above evaluation method are shown in Table 1.

[Comparative Example 1]
The polyvinylidene chloride resin composition used in Example 1 was dried by a box-type dryer under the conditions of a drying temperature of about 80 ° C. and a residence time of 24 hours (residual amount of vinylidene chloride monomer: 1.5 ppm), A stretched film was obtained in the same manner as in Example 1. The results of evaluation based on the above evaluation method are shown in Table 1.

[Comparative Example 2]
As an additive composition of the polyvinylidene chloride resin, the polyvinylidene chloride resin used in Example 1, ATBC, and ESO manufactured by the peracetic acid method (Newsizer 510RS, Nippon Oil & Fats Co., Ltd.) A stretched film was obtained in the same manner as in Example 1, except that the mixing was performed at a ratio of wt%, 5.5 wt%, and 1.5 wt% (total addition amount 7.0 wt%). The results of evaluation based on the above evaluation method are shown in Table 1.

[Comparative Example 3]
As an additive composition of the polyvinylidene chloride resin, the polyvinylidene chloride resin, ATBC, and ELO used in Example 1 were 93.0 wt%, 5.5 wt%, and 1.5 wt% (total added amount). A stretched film was obtained in the same manner as in Example 1 except that the mixture was mixed at a ratio of 7.0 wt%. The results of evaluation based on the above evaluation method are shown in Table 1.

[Comparative Example 4]
As an additive composition of the polyvinylidene chloride-based resin, the polyvinylidene chloride-based resin used in Example 1, ATBC, and ESO (Newsizer 510R, Nippon Oil & Fats Co., Ltd.) manufactured by the hydrogen peroxide method were respectively 89. A stretched film was obtained in the same manner as in Example 1 except that the mixing was performed at a ratio of 0.5% by weight, 7.0% by weight, and 3.5% by weight (total addition amount 10.5% by weight). The results of evaluation based on the above evaluation method are shown in Table 1.

[Comparative Example 5]
As the additive composition of the polyvinylidene chloride resin, 96 polyvinylidene chloride resin, ATBC, and ESO (Newsizer 510R, Nippon Oil & Fats Co., Ltd.) manufactured by the hydrogen peroxide method used in Example 1 were used. A stretched film was obtained in the same manner as in Example 1 except that mixing was performed at a ratio of .32 wt%, 3.5 wt%, and 0.18 wt% (total addition amount 3.68 wt%). The results of evaluation based on the above evaluation method are shown in Table 1.

  The wrap film of the present invention overcomes odor and suppresses thermal decomposition, has little change over time in physical properties such as excessive adhesion phenomenon of the film and lowering of drawability, and has extrusion characteristics such as torque fluctuation. Suitable as a stable film for wrapping.

Schematic of the apparatus implemented by the film forming process of this invention.

Explanation of symbols

1 Extruder 2 Die 3 Die Mouth 4 Tubular Vinylidene Chloride Copolymer Composition (Sock)
5 Sock liquid 6 Cold water tank 7 1st pinch roll 8 Parison 9 2nd pinch roll 10 Bubble 11 3rd pinch roll 12 Double ply film 13

Claims (2)

  A polyvinylidene chloride resin wrap film comprising 0.2 to 3.0% by weight of an epoxidized soybean oil produced by a hydrogen peroxide method and having a peroxide value of 13 or less as a stabilizer, The residual amount of vinylidene chloride monomer in the polyvinylidene chloride resin composition is 0.01 to 1 ppm, and the epoxy ring opening rate of epoxidized soybean oil in the film after film production is within 50%. A polyvinylidene chloride resin wrap film.   2. The polyvinylidene chloride resin wrap film according to claim 1, wherein the total amount of additives added to the polyvinylidene chloride resin is 4.0 to 10.0% by weight.

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