JP4942373B2 - Wrapping film manufacturing method - Google Patents

Description

  The present invention relates to a method for producing a wrap film used for simple packaging of food. In detail, excellent adhesion to containers, etc. is developed immediately after production, and it can stably produce polyvinylidene chloride resin wrap film with excellent adhesion and drawability even when distributed under high temperature in summer. The present invention relates to a method of manufacturing a wrap film that does not contaminate a cold water tank even when a cyclic resin melt-extruded therein is damaged and a refrigerant injected therein leaks.

In the inflation film-forming method, the resin extruded in a ring shape from the die is cooled and molded by bringing the outside into contact with cold water and the inside sandwiched between the die opening and the pinch roll with a coolant such as mineral oil. Is done. At this time, a portion sandwiched between the die opening and the pinch roll is called a sock, a refrigerant sealed in the inside is called a sock liquid, and a cylindrical resin folded by the pinch roll is called a parison. The inside of the resin extruded in an annular shape from the die reaches the pinch roll while touching the sock liquid, and when it passes through the pinch roll and is folded into a cylindrical shape, it becomes a parison with the sock agent applied thinly on the inner surface.
In the conventional film forming method, after the inside of the sock is cooled with a sock liquid, it is once pressure-bonded with a pinch roll, and then peeled again for inflation. At that time, the sock liquid is used to peel the inner surface of the parison pressed with the pinch roll. As a method, a method of adding a lubricant is used. A representative example of the lubricant is mineral oil. Patent Document 1 reports the use of a hydrophilic surfactant, and Patent Document 2 reports the use of a lubricant such as a water-soluble polysaccharide ether.

However, in these manufacturing methods, when the sock is accidentally broken during manufacturing and the internal sock liquid leaks, the cold water tank is contaminated with the sock liquid containing the lubricant. If the sock liquid leaks, the cold water tank is contaminated by the liquid, and a great deal of labor is required for the subsequent processing such as washing around the cold water tank. Furthermore, in terms of the physical properties of the wrap film, in the wrap film distributed under high summer temperatures, there is a problem that the lubricant applied to the film surface induces excessive adhesion and deteriorates the drawability.
Here, the adhesion is an index of the ease with which the wrap films adhere to each other and the container of the wrap film, and the drawability is an index of the ease of pulling out the wrap film wound around the paper tube. is there.

Patent Document 3 discloses a method for producing a wrap film using a composition comprising a polyvinylidene chloride resin and a natural wax. The polyvinylidene chloride resin wrap film of Patent Document 3 has good adhesion and good drawability even in the summer when it is circulated under high temperature. However, since a lubricant is used as a sock liquid and a wrap film is produced by an inflation method, if the sock breaks accidentally during production and the sock liquid leaks, the sock liquid containing the lubricant will contaminate the cold water tank. In terms of physical properties, since the lubricant is applied to the film surface by the sock solution containing the lubricant, there is a problem that the obtained wrap film exhibits satisfactory adhesion only after a certain period of time.
Further, when water is used as a sock liquid in order to prevent the occurrence of contamination of the cold water tank during the production of the wrap film, the parison does not open at all and cannot be inflated.
JP 55-133927 A Special table 2002-539986 gazette JP-A-11-199735

  The object of the present invention is to produce a polyvinylidene chloride-based resin wrap film that expresses good adhesion immediately after production, maintains good adhesion even when distributed under high temperatures in summer, and has improved drawability Providing a method for producing a polyvinylidene chloride resin wrap film in which the sock liquid does not contaminate the cold water tank even if the sock breaks during production and the sock liquid leaks, and the above It is providing the method of satisfy | filling these conditions and manufacturing a polyvinylidene chloride type | system | group resin wrap film stably.

As a result of intensive studies to solve the above problems, the present inventors have found that the object can be achieved by adding a wax to a vinylidene chloride resin, and have completed the present invention.
That is, the present invention is a resin composition comprising a wax and a polyvinylidene chloride-based resin, and a resin composition containing 100 to 10,000 ppm of wax in the resin composition is melt-extruded in a ring shape from a die, This is a method for producing a wrap film, which comprises injecting water into the interior, inflating after cooling.

By using vinylidene chloride resin added with wax, it is possible to use water as a sock solution in the production of wrap films, and it exhibits good adhesion immediately after production, even if it is distributed under high temperatures in the summer It is possible to stably produce a wrap film that maintains excellent adhesion and has improved drawability.
Moreover, since water is used as the sock liquid, the cold water tank will not be contaminated even if the sock breaks during production and the sock liquid leaks.

Hereinafter, the present invention will be described in detail.
The resin composition used in the present invention comprises a polyvinylidene chloride resin and a wax, and the wax is contained in the resin composition in an amount of 100 to 10,000 ppm. The resin composition may contain additives for improving the performance of the wrap film, such as a plasticizer and a stabilizer.
The composition of a typical resin composition is from 89 to 99.39% by weight of polyvinylidene chloride resin, 100 to 10,000 ppm of wax, 0.1 to 7% by weight of plasticizer, and 0.5 to 3% by weight of stabilizer. Become.
The polyvinylidene chloride resin is composed of a vinylidene chloride polymer, 85 to 97% by weight of vinylidene chloride, and a monomer copolymerizable therewith, for example, acrylic acid esters such as vinyl chloride, methyl acrylate and butyl acrylate, and methyl methacrylate. , Methacrylic acid esters such as butyl methacrylate, acrylonitrile, vinyl acetate and the like, or a copolymer comprising 15 to 3% by weight.

Examples of the plasticizer include dibutyl sebacate (hereinafter referred to as DBS), dioctyl adipate, acetyl tributyl cytolate (hereinafter referred to as ATBC), acetylated monoglyceride (hereinafter referred to as ACGL), and the like.
Examples of the stabilizer include epoxidized vegetable oils such as epoxidized soybean oil (hereinafter referred to as ESO) and epoxidized linseed oil (hereinafter referred to as ELO).
Furthermore, as long as the effects of the present invention are not impaired, the resin composition is a plasticizer, a stabilizer, a weather resistance improver, a colorant such as a dye or a pigment, an antifogging agent, or an antibacterial agent. Further, a lubricant, a nucleating agent, an oligomer such as polyester, a polymer such as MBS, or the like may be added.

In order to produce a vinylidene chloride-based wrap film stably using water as a sock solution, the resin composition should contain 100 to 10,000 ppm, preferably 2,000 to 4,000 ppm of wax. Very important.
By containing 100 to 10,000 ppm of wax in the resin composition, it exhibits good adhesion immediately after production, maintains good adhesion even when distributed under high temperatures in the summer, and further has drawability. An improved polyvinylidene chloride resin wrap film can be produced. And a wrap film can be manufactured stably using water as a sock liquid.
In particular, when the wax content is less than 100 ppm, the parison does not peel stably. If the content of the wax exceeds 10,000 ppm, crystallization proceeds and the stretchability deteriorates, making it difficult to form a stable film. Moreover, the adhesiveness of the obtained wrap film becomes inadequate.

Examples of the wax include synthetic wax and natural wax. Examples of the synthetic wax include petroleum-derived chemical synthetic products such as synthetic paraffin, fine wax, and polyethylene wax. Examples of natural waxes include those derived from natural products such as carnauba wax, spal acetyl wax (whale oil), montan wax, beeswax, wood wax, lanolin (wool), rice wax, jojoba oil, and the like. These may be used alone or in combination of two or more.
When carnauba wax is used, even when excessive heat is applied to the wrap film, it has excellent adhesion and drawability, so it is preferable to use it alone or in combination with other waxes. When carnauba wax is used in combination with other waxes, the carnauba wax is preferably contained in the resin composition at 2,000 to 4,000 ppm.

  According to the present invention, according to the inflation film forming method, the sock is formed by bringing the outside and inside of the resin extruded in an annular shape from the die into contact with cold water. When the parison once crimped with a pinch roll is peeled again and blown, it can be peeled off with water without using a lubricant to peel the parison inner surface due to the effect of the wax component present in the resin composition. It is. Thereafter, the wrap film can be stably produced by a normal inflation film forming method. The produced wrap film expresses good adhesion immediately after production, and even if it is distributed under high temperatures in summer, it retains good adhesion and has good drawability.

Other materials may be mixed with the water used as the sock liquid as long as the object of the present invention is not hindered. However, in order to prevent the sock from being broken during the production and contaminating the cold water tank. It is preferable to use only water as the sock liquid.
According to the present invention, the additive may be added before polymerization of the polyvinylidene chloride-based resin or in any step until obtaining a composition at the time of polymerization. For example, to the polyvinylidene chloride-based resin, Wax, if necessary, an additive may be added, and if necessary, the mixture may be mixed uniformly with a ribbon blender, a Henschel mixer or the like, and aged for about 24 hours. The resin composition thus obtained is melt-extruded from a die in a ring shape, and both sides of the parison are contacted with cold water and cooled to form a sock. The parison that has passed through the pinch roll and folded into a cylindrical shape is easily peeled even after being once crimped by the pinch roll due to the effect of the wax, and becomes a tube shape by injecting air into the inside. The tube-like parison thus obtained can be continuously stretched by inflation by re-heating and then injecting air. The stretched film is wound with a normal winder, and a wrap film is obtained through a slit and rewind process.
At this time, due to the presence of wax in the resin composition, the wax bleeds during melt extrusion, and the parison pressed with a pinch roll can be peeled off, and water is used as a sock solution without using a lubricant. Is possible.

The wrap film is required to satisfy a certain degree of adhesion from the commercial characteristics to those circulated at high temperatures in summer from immediately after production. The adhesion work measured by the method described later is more preferably 1.2 mJ or more and less than 2.5 mJ immediately after production, either at 28 ° C. for one month or at 40 ° C. for one month. If the work of contact is less than 1.2 mJ, the work of contact may be low and it may be difficult to touch the container, etc. Conversely, if the work of contact is more than 2.5 mJ, the wrap films may be cluttered together due to the high work of contact. Usability may be reduced.
Furthermore, the pulling power is 10 cN or more and 100 cN or less after storage for one month at 40 ° C. measured by the method described later, assuming a heat history when placed in a storage warehouse in the summer for a long period of time. It is preferably 10 cN or more and 70 cN or less. If the pull output is less than 10 cN, it may be drawn more than necessary, and if it exceeds 100 cN, problems such as a halfway cut may occur.
Although there is no restriction | limiting in the thickness of the wrap film of this invention, Generally it is 5-20 micrometers.
The wrap film obtained as described above exhibits satisfactory adhesion in the range of 1.2 to 2.5 mJ immediately after production and after aging at 28 ° C. and 40 ° C. for 1 month, and in the range of 10 to 70 cN. It has good drawability.

EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention concretely, this invention is not limited at all by these.
The evaluation method of the film obtained by the present invention is as follows.
1. Film-forming properties The following three stages of evaluation are performed to determine whether or not a wrap film can be obtained by continuously extruding a ring from a die and injecting water into the sock for a long time.
Evaluation symbol Judgment ○ The parison continues to open stably for a long time, and a wrap film is obtained and can be manufactured. △ A wrap film is obtained, but the parison opens only for a short time and cannot be manufactured. × The parison does not open at all and is manufactured. Impossible

2. Adhesion Assume that wrap films are used at home, and evaluate the adhesion between wrap films. Evaluate whether to maintain good adhesion immediately after film formation and after various distribution processes. Therefore, a wrap film immediately after film formation and a wrap film stored in advance in a constant temperature bath set to 28 ° C. and 40 ° C. for a certain period (one month) are used.
The measurement is performed in an atmosphere of 23 ° C. and 50% RH. First, two aluminum jigs having a bottom area of 25 cm 2, a height of 55 mm, and a weight of 400 g are prepared, and a filter paper having the same area as the bottom area is attached to the bottom surfaces of both jigs. Cover the bottom surface of both jigs with the filter paper, and cover with a wrap film so that no wrinkles will enter. The two jigs covered with the wrap film are combined with each other so that the bottom surface on the side covered with the wrap film overlaps, and is pressure-bonded at a weight of 500 g for 1 minute. Next, the work amount required to peel both wrap film surfaces perpendicularly to each other at a speed of 5 mm / min with a tensile and compression tester is measured (unit: mJ / 25 cm 2).

The adhesiveness of the wrap film is evaluated in the following four stages based on the measured numerical values.
<Initial work after 28 months at 28 ° C, and after 1 month storage at 40 ° C>
Evaluation symbol Work of adhesion (mJ) Judgment ◎ 2.0 or more and less than 2.5
Excellent level ○ 1.2 or more and less than 2.0 Adhesiveness, practical level △ 0.8 or more and less than 1.2 Slight adhesion, but practically problematic
2.5 or more and less than 3.2 Adhesiveness is too high and handling is inferior × Less than 0.8 Adhesiveness is too small and impractical
3.2 or higher Adhesiveness is too high and handling is extremely inferior

3. Withdrawal As with the adhesiveness, it is assumed that wrap films that have undergone various distribution processes are used at home, and the drawability between the wrap films is evaluated. Therefore, the wound wrap film stored under the same conditions is used as a preliminary preparation for the adhesion evaluation. If the pulling power exceeds 100 cN, problems such as cut off may occur, so it is assumed that it will receive a heat history when placed in a storage warehouse in midsummer for a long period of time, and set as 40 ° C as advance preparation The wound wrap film is stored in advance in a constant temperature bath for a certain period (one month).
The measurement is performed in an atmosphere of 23 ° C. and 50% RH. A plastic free roll consisting of a drive unit having a length of about 310 mm and a diameter matched to the inner diameter of the paper tube of the wound wrap film, and a fulcrum shaft having a length of 330 mm is connected to the center in the width direction of the wound wrap film and the free roll drive unit. It is installed in the paper tube of the wound wrap film so that the center in the longitudinal direction of the film is aligned. A free roll integrated with this wound wrap film, the hanger suspended on the load cell side at the top of the tensile compression tester and its fulcrum axis are parallel, and the width direction of the wound wrap film is perpendicular to the center of the hanger. Place the fulcrum shaft on the bearing installed at the bottom of the testing machine so that the center is located, and then peel off the wound wrap film integrated with the free roll to the load cell side above the testing machine. Secure the hanging hanger with double-sided tape so that there are no wrinkles.

Next, the wound wrap film is peeled off perpendicularly from the paper tube at a speed of 1000 mm / min with a tension / compression tester. At this time, the peak value of the force required to peel the wound wrap film from the paper tube is taken as the measured value of the drawability. (Unit: cN / 30 cm width) The drawability of the wound wrap film is evaluated based on the measured numerical value in the following four stages.
Evaluation symbol Peak value (cN) Judgment ◎ 10 or more and less than 70 Excellent extractability and excellent level ○ 70 or more and less than 80 Excellent drawability and practical level △ 80 or more and less than 100 Inferior pullability and practical use Top problem × Less than 10 Withdrawability is too light, impractical
100 or more The pullability is very inferior, impractical

4). Comprehensive evaluation Comprehensive judgment is made based on the evaluation results of film-forming properties, adhesion and drawability, and the following three stages of evaluation are performed.

Evaluation symbol Standard Judgment No No △ or × Good balance of film forming properties and physical properties △ No No Thin film forming properties and poor balance of physical properties No good balance of film forming properties and physical properties

[Example 1]
A vinylidene chloride resin (PVDC) having a weight average molecular weight of 100,000 (90% by weight of vinylidene chloride and 10% by weight of vinyl chloride), and 4.5% by weight and 1.5% by weight of ATBC and ELO, respectively. To 10 kg of the mixed vinylidene chloride resin composition, 40 g (4000 ppm) of powdered carnauba wax was added and mixed at room temperature with a high-speed mixer for 5 minutes, and passed through a 40 μm mesh.
The wax-containing vinylidene chloride resin composition thus obtained was melt extruded at an extrusion rate of 12.5 Kg / hr in a melt extruder while adjusting the heating conditions of the extruder so that the temperature at the outlet of the annular die was 170 ° C. Water was poured into the sock, the parison was supercooled, and then stretched to form a tubular film. The tubular film was pinched and folded flat, and a two-layer film having a folding width of 320 mm and a thickness of 10 μm was wound at a winding speed of 16 m / min.
The film was slit to a width of 230 mm and peeled so as to form a single film, while being wound on a paper tube having an outer diameter of 36.6 mm and a length of 305 mm to produce a wrap film having a thickness of 10 μm.
Table 1 shows the results of evaluating the film forming property, the adhesiveness of the wrap film, and the drawability.

[Comparative Example 1]
Carnauba wax was added to the same vinylidene chloride resin composition as in Example 1 in an amount of 0.5 g (50 ppm). Except that, melt extrusion was performed in the same manner as in Example 1, water was poured into the sock, and the parison was passed through. After cooling, when inflation stretching was attempted, no film could be formed. About this, the result evaluated about film forming property is shown in Table 1.

[Comparative Example 2]
A wound wrap film having a thickness of 10 μm was produced by the same operation as in Example 1 except that 150 g (15000 ppm) of carnauba wax was added to the same vinylidene chloride resin composition as in Example 1.
The results of evaluating the obtained film are shown in Table 1.

[Comparative Example 3]
Without adding wax to the same vinylidene chloride resin composition as in Example 1, except that melt extrusion was performed in the same manner as in Example 1, water was poured into the sock, the parison was supercooled, and then inflation stretching was performed. Attempts to form the film failed. About this, the result evaluated about film forming property is shown in Table 1.

[Comparative Example 4]
While adding wax to the same vinylidene chloride resin composition as in Example 1 and adjusting the heating conditions of the extruder so that the temperature at the outlet of the annular die is 170 ° C., the melt extruder is 12.5 Kg / hr. Melt extrusion at an extrusion speed, lubricant (mineral oil) and water were injected into the sock at a ratio of 1: 4, the parison was supercooled, and then stretched to form a tubular film. Otherwise, the same as in Example 1 A wound wrap film having a thickness of 10 μm was produced by the above operation.
The results of evaluating the obtained film are shown in Table 1.

[Comparative Example 5]
40 g (4000 ppm) of carnauba wax was added to the same vinylidene chloride resin composition as in Example 1, and a wound wrap film having a thickness of 10 μm was produced in the same manner as in Comparative Example 4.
The results of evaluating the obtained film are shown in Table 1.

From the above results, the following can be understood.
In the wrap film containing the wax of the scope of the present invention (Example 1), the melt film is melt-extruded in an annular shape from the die, and only water is injected into the inside of the wrap film. Therefore, even if a sock breakage occurs during production, the sock liquid does not contaminate the cold water tank. Furthermore, the wrap film thus obtained exhibits good adhesion immediately after production, and has an excellent balance between adhesion and drawability even after aging.
On the other hand, when the addition amount of the wax is too small (Comparative Example 1), it is difficult to form a stable film because it is difficult to peel the parison pressed by the pinch roll, while when the addition amount is too large (Comparison Example 2) Since the crystallization progresses and the stretchability deteriorates, stable film formation is difficult, and the expression of adhesion is insufficient.
Furthermore, when no wax is added (Comparative Example 3), the parison bonded with the pinch roll cannot be peeled off, and thus the film cannot be manufactured.
When a sock solution containing a lubricant is used (Comparative Examples 4 to 5), the sock solution containing the lubricant contaminates the cold water tank due to the occurrence of sock breakage during the production. As for the obtained wrap film, the effect of reducing the drag output is seen for the one added with carnauba wax (Comparative Example 5), but since the lubricant is applied to the surface of the wrap film, it is good only after a certain period of time has passed since the manufacture. Does not express good adhesion.

  The film obtained by the present invention is suitable as a film for wrapping applications, expresses good adhesion immediately after production, retains good adhesion even when distributed under high temperatures in summer, and has improved drawability. ing. And even when a sock breakage occurs during production, a production method is provided in which the sock liquid does not contaminate the cold water tank.

Claims (1)

A resin composition comprising a wax and a polyvinylidene chloride resin, wherein a resin composition containing 100 to 10,000 ppm of wax in the resin composition is melt-extruded in a ring shape from a die, and water is injected into the resin composition. And a method for producing a wrap film comprising inflation after cooling.