JPH0334762B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to an improvement in a melt extrusion processing method for a vinylidene chloride-methyl acrylate copolymer. (Prior art and problems to be solved by the invention) Vinylidene chloride-methyl acrylate copolymer (hereinafter abbreviated as VDC-MA) has conventionally been generally used as a type of vinylidene chloride copolymer, that is, vinylidene chloride. - It has been treated as an equivalent of vinyl chloride copolymers. In addition, as a method for molding these copolymers using a melt extrusion method, the copolymers are melt-kneaded in an extruder, extruded alone or in layers with other resins, and then extruded into, for example, a cylindrical shape and cooled and solidified. (Japanese Patent Publication No. 44-32676), for example, by inflating a cylindrical extrudate to make a container (Japanese Patent Publication No. 49/1973).
(Japanese Patent Publication No. 52-14855), for example, extruded into a plate shape with a T-die to make a sheet (Japanese Patent Publication No. 52-22676), for example, extruded into a ring shape and biaxially stretched to make a tubular film or a flat film (Japanese Patent Publication No. 52-22676). -31889) is described in each specification and is well known. On the other hand, the MA component in VDC-MA, similar to the vinyl chloride (VC) component of vinylidene chloride-vinyl chloride copolymer (hereinafter abbreviated as VDC-VC), exhibits extremely rapid thermal decomposition of vinylidene chloride polymer. This is to moderate the speed and facilitate plastic deformation of the copolymer itself as a whole. Since it is thought that the MA component is more effective than the VC component, if VDC-MA can be industrially molded, it will have an advantage over VDC-VC in terms of gas barrier properties, etc. The extrusion molded products of VDC-MA should have been listed on the market and put into practical use as soon as possible, but at present, the molded products of vinylidene chloride containing acrylic components that have finally appeared on the market are, for example, Only molded products made from acrylic-containing vinylidene chloride latex in an emulsion state that is molded by so-called casting, coating, casting, etc., without relying on extrusion methods such as those described in Publication No. 59-23682, etc. It is. The reason for this is that, according to the knowledge of the present inventors, VDC-MA has a unique polymerization form in order to make a resin that can withstand extrusion, and that the empirical rules and knowledge when copolymerizing VDC-VC are necessary. It is not always utilized, and overall research on polymerization conditions is not sufficient. On the other hand, the requirements of those who list resin molded products as products or product packaging materials are based on the existence of a wide variety of similar existing products that are already listed. All aspects, including standards, have been highly improved, and in light of the evaluation criteria for determining commercialization, which is based on the premise of being able to compete with existing products, the current VDC-MA is based on the extrusion method. This is because it is ranked as a resin that cannot be commercialized, and it is not even possible to provide polymer design values for research on polymerization conditions. In other words, the biggest specific drawback of VDC-MA is that although the knowledge gained from large-diameter extruders can be applied to small-diameter extruders, the knowledge obtained from small-diameter extruders is difficult to apply to large-diameter extruders. Therefore, all basic experiments for improvement must be based on large-diameter extruders with high resin consumption, which has the drawbacks of uneconomical experimental design and difficulty in its execution. Γ From the perspective of labor productivity, design quality level and sufficiency in a mass production system using a large-diameter extruder, it controls, for example, the heat resistance stability of the resin, melt flow stability, uniformity of flow development, etc. There are problems with the structural factors, and the current level does not seem to meet the evaluation criteria based on commercialization. Γ Thermal stability achieved by adding plasticizers, modifiers, etc.
Although it is possible to improve plastic fluidity, the magnitude of the negative effect on barrier properties caused by the addition of modifiers is
A fact that negates the very necessity of VDC-MA development. It is summarized in The present invention has been made in view of the current situation and to overcome the difficulties, and has the following objectives: 1. To achieve extrusion molding, which is more efficient and economical than casting, coating, casting, etc. methods using latex. To improve the processing method to a technical level that can be carried out under industrial standards using, for example, a large-diameter extruder with a diameter of 50 mm or more, thereby making it possible to stably supply VDC-MA extruded products that are in high demand in the market. 2. To provide target values for VDC-MA composition suitable for extrusion processing, thereby promoting the development of polymerization methods and conditions, and facilitating the appearance of further improved VDC-MA extrusion processed products. 3. Less use of modifiers such as plasticizers, so-called
To enable stable supply of VDC-MA extruded products in a state where the essential properties of VDC-MA can be fully utilized. (Means for Solving the Problems) The contents of the present invention will be explained in detail below using drawings and the like. Figures 2 and 3 show the results obtained by the method of the present invention.
Oxygen permeation amount [O ₂ TR, unit: 15 μ cc/m ²・
24Hrs・atm・(at20℃・65%RH)] and water vapor permeation rate [WVTR, unit: 15μ・g/m ²・24Hrs・
40°C, 90% RH] is a graph showing the relationship. FIG. 4 is a graph showing the relationship between the Elmendorff tear strength (unit: g) and the MA component ratio of the same VDC-MA sheet. Therefore, the overall relationship in Figures 2 to 4 is VDC-
This is a relationship diagram showing whether or not a continuous layer without cracks etc. can be maintained when MA is put to practical use as a gas barrier layer in the form of a single layer or a laminated component layer. Figures 2 and 3 show the fact that the lower the amount of MA, the lower the amount of permeation of both O ₂ TR and WVTR, indicating that it can become an excellent gas barrier resin layer.On the other hand, Figure 4 This shows that reducing the amount of MA component results in a resin layer that is weak in terms of mechanical properties. Therefore, when using VDC-MA as a barrier resin layer, it is necessary to select the MA component amount from the range of 1 to 15% by weight, and when high levels of both mechanical strength and barrier properties are required. It can be said that it is desirable to select a material with an MA amount in the range of 5 to 13% by weight. In addition, the values of O ₂ TR and WVTR shown in Figures 2 and 3 are:
A so-called virtually unplasticized copolymer containing only 1% by weight of epoxidized linseed oil and 0.4% by weight of magnesium oxide, which are called heat stabilizers, is added to the copolymer.
The value shown by the extruded VDC-MA sheet,
The reason why such a high level of barrier properties can be achieved is because
It should be noted that a major advantage of the process of the present invention is that VDC-MA can now be economically and industrially extruded in a substantially unplasticized state. In addition, as reference values for FIG. 2 (O ₂ TR) and FIG. 3 (WVTR), the characteristic values of commercially available vinyl chloride films and vinylidene chloride films are shown below, with the same unit amounts.

[Table] Figure 1 is an exploded diagram. This exploded diagram is also a proof diagram showing the validity of the technical idea of the present invention. The horizontal axis in Figure 1 is the weight average molecular weight (GPC
Similarly, the vertical axis is the copolymer content (%) with a molecular weight of 20,000 or less (according to the same GPC method) contained in the copolymer, on a logarithmic scale. It is a rectangular coordinate on a logarithmic scale. What is plotted in Figure 1 expresses the degree of sufficiency when trying to perform extrusion molding processing in a mass production system as a comprehensive evaluation (specifically, the evaluation method in the main text, the description of the evaluation scale, and Table 3) ), the results of the comprehensive evaluation are shown in relation to the weight average molecular weight of the corresponding copolymer and the content of copolymers with a molecular weight of 20,000 or less contained in the copolymer. ing. In addition, in the diagram, ◎ indicates that we are confident enough to produce with industrial equipment, and 〇 indicates that production with industrial equipment is somehow possible with partial design changes.
The mark △ indicates that it is unsuitable for production in industrial equipment, and the mark x indicates that it is difficult to obtain a molded product. According to FIG. 1, those evaluated as ◎ and ○ have a coordinate relationship that is distributed inside those evaluated as △ and ×. What should be noted is that the items marked with ◎ and ○ are as follows:
The fact is that all of these are copolymers obtained by mixing (adjusting) copolymers that were originally evaluated as X or Δ. Therefore, there is a technical means to improve the breakdown diagram of FIG. 1, which was evaluated as unadoptable, into one that can be adopted. The technical idea is as shown in Figure 1 and defined in the present invention as a point A [70,000 yen expressed by the coordinate point [weight average molecular weight, content of copolymer with a molecular weight of 20,000 or less in the copolymer]. , 18], point B [150,000, 4], point C [25
This means adjusting and selecting a copolymer that satisfies the relationship that the value is within the range of the quadrilateral formed by connecting the four coordinate points of point D [120,000, 4] and point D [120,000, 18] with straight lines. I understand. The means of adjustment shown in the present invention is to mix copolymers with each other, but if the skeleton of the target copolymer is specified, it is possible to select polymerization conditions and adjust them to the desired value. Since it is not difficult, the adjustment referred to in the present invention can be understood to include polymerization adjustment. In recent years, in extrusion molding processing plants based on commercialization, labor and resource conservation has progressed, and ensuring high labor productivity, together with maintaining high quality standards, is a key factor in the survival of the company. control that thing. From this point of view, it is preferable to use the system shown in FIG.
Point E [80,000, 14], Point F [105,000, 8], Point G [130,000,
8], point H [100,000, 14], and the composition of the copolymer is adjusted to a value within the range of the quadrilateral drawn by a straight line. The technical significance of this is presumed to be that when increasing the content of a copolymer with a molecular weight of 20,000 or less, the molecular weight distribution of the entire copolymer is adjusted so as not to become too broad. According to research, the weight average molecular weight is in the range of 70,000 to 250,000, and the ratio to the number average molecular weight determined by the same GPC method (i.e., weight average molecular weight ÷ number average molecular weight) is 2 to 250,000.
It is desirable that the value be in the range of 3. One of the usefulness of the production method of the present invention is the properties exhibited by the molded article obtained. If I introduce two or three of the main ones, the first one is
are the characteristics of the gas barrier shown in FIGS. 2 and 3 above. This gas barrier property is a property that can also be obtained with the same VDC-based copolymer, such as VDC-VC, but when using a VC component, the proportion of VC in the copolymer when it becomes a molded product is 8. It is difficult to reduce the O ₂ TR (i.e., high barrier There is a limit to extracting things with a value of On the other hand, VDC− obtained by the method of the present invention
By keeping the MA component content at 15% or less and adding a small amount of a modifier that does not significantly contribute to deterioration of gas barrier properties, MA molded articles can maintain excellent extrusion processability, resulting in VDC- This means that it can be used as a layer material with superior gas barrier properties compared to VC. Figure 5 is a strain-stress relationship graph of the VDC-MA molded product obtained by the method of the present invention.
A comparison (dashed line) with that of a VDC-VC molded product is shown. According to FIG. 5, depending on its composition and conditions, the molded product obtained by the method of the present invention (solid line) elongates when the molded product is stretched, and returns to its original shape when the stretching force is released. This shows that the material has the property of returning to a state close to that of the original material (the part shown by the dashed line), which indicates that it has the so-called suitability for stretch packaging. This property is VDC
- Its use is attracting attention because it has unique properties that cannot be obtained with VC compositions. That is, currently known single-layer films having stretchability include vinyl chloride film and ethylene-vinyl acetate copolymer film.
Since these films have problems such as poor gas barrier properties including water vapor and loss of the contents of the package, it has become a challenge in the industry to provide stretch films with barrier properties. As one measure,
Lamination with barrier resins has been considered, but since barrier resins generally cannot be expected to have stretch properties, it is difficult to provide both barrier properties and stretch properties. In this current situation, the appearance of VDC-MA, which is easy to mold, is
When applied as a single layer or as a laminated material, it is attracting attention as a material that exhibits great usefulness. In order to effectively exhibit such stretchability, it is desirable to select and use a copolymer containing MA in an amount of 10 to 15% by weight. FIG. 6 shows an example of experimental results (solid line) showing the shrinkage characteristics of stretched and oriented VDC-MA, in comparison with the case of VDC-VC (broken line). Although the stretching conditions for both are not necessarily the same, they are shown as examples of comparison between the two at the highest level of orientation that can be achieved with each composition. According to the results shown in Figure 6, it can be seen that VDC-MA has superior properties that exceed VDC-VC in both low-temperature shrinkability and the amount of shrinkage in a constant temperature range. . This shrinkage performance is, for example,
When VDC-MA is used as a gas barrier resin layer in a laminated film and used as a whole as a low-temperature shrinkable gas barrier laminated packaging material for applications such as raw meat packaging, conventional
This shows the usefulness of providing a laminated film that has better low-temperature shrinkability than laminated films containing VDC-VC as a component layer and can be shrink-wrapped tightly without wrinkles. The second usefulness of the present invention is that molded products having the above-mentioned characteristics can be manufactured using equipment on an industrial production scale, and that it provides various molded products that satisfy quality standards. This is something that can be done. The reasons for this will be supplemented below along with the meanings of the evaluation items in the present invention. First of all, the evaluation items ``thermal stability of resin during extrusion'' and ``incidence of punctures'' are based on, for example, the extruder being operated continuously for a long time to ensure normal quality molding without decomposition products or discolored streaks. It is an indicator that shows how long a product can be continuously produced under set normal operating conditions without requiring recovery and correction work, and is used in setting product quality and labor productivity (including equipment design). This corresponds to the basic condition of In other words, in manufacturing equipment for industrial production, the above basic conditions assume that continuous production will continue for 10 hours or more on average probability, and based on that premise, for example, the capacity of molded product storage equipment, equipment etc. Automatic interlocking, operating mechanisms, quality adjustment mechanisms, etc. are considered, and the design is designed to minimize the required man-hours and maximize operating conditions. Therefore, if you try to manufacture a molded product that does not meet the above basic conditions using equipment with such a design, it will not only take a lot of man-hours to restore the equipment to normal operation, but also The operating rate of the equipment decreases and the quality of the settings cannot be guaranteed, resulting in a state where production is impossible. On the other hand, in the present invention, since the continuity evaluation, which is the basic condition described above, is fully satisfied, it can be said that it is possible to manufacture an economically competitive molded product that satisfies the set quality. Furthermore, the fact that the "thermal stability of the resin in the extruder" can be maintained at a high level means that the method of the present invention can also be applied to in-die extrusion processing, which requires continuous retention of the resin in the extruder. It can be used as a basis. Next, "extrusion amount unevenness" and "thickness unevenness in the width direction" are both fluid elements that control the uniformity of the thickness in the longitudinal direction and the thickness in the lateral direction of a molded article.
However, in this case, the fact that both of these fluctuations can be maintained at a low level means that the fluidity is excellent in biaxial directions. Furthermore, it is noteworthy that it shows that it is possible to perform economical extrusion using a die with a wide width (or a large diameter), and that it is possible to extrude uniformly evenly into mold cavities of a wide area. Moreover, "homogeneous stretchability" corresponds to the main item that determines suitability for stretching processing. In other words, the characteristics that control the quality of the obtained film, such as its appearance quality such as color tone, wrinkles, and bending, mechanical properties such as tear strength and tensile strength, and physical properties such as gas barrier properties and transmission distortion. Therefore, satisfying this item is of great significance in obtaining a high quality stretched film. Next, the meaning of "allowable range of change in extrusion temperature conditions" is:
This is an index that indicates the suitability of selecting a companion resin when obtaining a laminated product (film molding, medium molding, in-die extrusion molding, etc.) using the in-die lamination coextrusion method. In other words, in in-die lamination coextrusion, it is important to approximate the viscosity of the laminated resins, but the wider this tolerance range, the wider the range of selection of resins that can be partners. Therefore, it is significant that it can be used for high-quality laminate products. Furthermore, the meaning of "laminate extensibility" is
Evaluation of whether the VDC-MA layer can follow the stretching deformation of other layers. - It is significant as a means of evaluating the homogeneous stretchability of the MA layer (i.e., the role mechanism of the barrier component layer). In the case of the present invention, all of the above-mentioned evaluation items are met at a high level (3rd and 4th items).
(See table) Since it exhibits the advantage of being able to supply various molded products economically and on an industrial scale, its usefulness can be said to be extremely high. The weight average molecular weight of VDC-MA in the present invention,
The number average molecular weight, the content of copolymers with a molecular weight of 20,000 or less, etc. are values determined by the following method, that is, the GPC (gel permeation chromatography) method. The equipment used is as follows. Γ Model: High performance liquid chromatography (manufactured by Waters) Γ Column: Microstyradil (same as above) Γ Solvent: Tetrahydrofuran [hereinafter abbreviated as THF] (manufactured by Wako Pure Chemical Industries, Ltd., for liquid chromatography) Measurement format is as follows street. A sample to be measured dissolved in THF at a concentration of 0.5% by weight is kept at 20°C. Changes in the concentration of the sample flowing out of the column together with the solvent over time after sample injection are measured using differential refraction. Detect it as the output current value of the meter and draw it on the chart of the recorder. Calibration of molecular weight is as follows. Molecular weight is 3600, 35000, 110000, 650000,
For each of the five types of monodisperse polystyrene with a molecular weight of 1,460,000, the measurement using this measuring device was completed in advance, and this data was used as a calibration curve to calculate the VDC-
Use this as the basis for calculating the molecular weight of MA. In other words, the relationship between the number of GPC counts (number of seconds from the time of sample injection to the starting point O) until the peak value of the output current of the differential refractometer occurs and the molecular weight (semi-logarithm) of monodisperse polystyrene with a known molecular weight. As the coordinate point, this 5
A graph is created by connecting the coordinate points of the species with straight lines, and this is used as a test line for molecular weight calculation. Measurements and calculations are as follows. From the relationship chart between the GPC count number drawn for the target resin sample and the output current value of the differential refractometer, the output current value shown at the position separated by every 20 counts between GPC count number 900 and 1440. (Pi) is determined as the frequency of the molecular weight (according to the inspection line) Mi corresponding to the GPC count number, and each is calculated as follows. Weight fraction Wi of molecular weight Mi=Pi/ΣPi Next, the weight average molecular weight and number average molecular weight of VDC-MA in the present invention are calculated using the weight fraction Wi of molecular weight Mi and the molecular weight Mi calculated in this way. Then,
Each is calculated as follows. Weight average molecular weight=Σ(Wi×Mi) Number average molecular weight=1/Σ(Wi÷Mi) The content of copolymers with a molecular weight of 20,000 or less in the present invention is calculated as follows. Molecular weight less than 20,000
The weight fractions Wi corresponding to each of Mi are summed, and 100 times the sum is taken as the content (weight percent) of a copolymer with a molecular weight of 20,000 or less. As described above, weight average molecular weight,
The method for determining the number average molecular weight can be found in publications related to polymers, such as "Kyomunshi Measuring Methods Volume 1" (Baifukansha,
This method was widely known in 1971). The evaluation method and evaluation scale used in the present invention will be described in detail below. Productivity evaluation in industrial equipment (1) Evaluation using single-layer film production equipment. The outline of the extrusion-film forming method is as follows. In Fig. 7, extruder 1 (diameter D = 80 mm, L =
The raw resin supplied from the hopper part 2 is melted and kneaded in the hopper section (1600mm, temperature control zone 5 section), and the circular die 3 attached to the tip of the hopper part 2 is melted and kneaded.
(diameter 200 mm, slit gap 1 mm), the extruded cylindrical film 4 with a target thickness of 1 mm is extruded at a rate of 100 kg per unit time, is introduced into the cooling tank 5, supercooled, and then sealed inside the cylindrical film. Simultaneous biaxial stretching with longitudinal and horizontal (4 to 5 x 4 to 5) inflation was carried out using the air and the circumferential speed ratio between the pinch rolls 6, 6', 7, and 7'. is folded into a two-ply flat film 8, and the two-ply film (40 microns in total) with a fold width of 1200 or 1900 mm and a wall thickness of 20 microns is wound on the winding shaft 10 of the winding device 9.
Winding at a rate of 13 or 20m/min. The outline of the evaluation method is as follows. We prepared a three-shift experimental team made up of workers skilled in film forming experiments and production at VDC-VC, and selected important factors as evaluation items for maintaining labor productivity and set quality in continuous production. The contents of these evaluation items were prepared in advance based on an experimental plan that considered whether the content of these evaluation items could be evaluated in the most accurate and efficient manner. Indicate by evaluation. The evaluation items and evaluation scale are as follows. a) This was an attempt to evaluate the thermal stability of the resin during the extrusion process, and the continuous sustainability of the thermal stability of the resin against retention of the resin in the extruder. The evaluation is based on the length of extrusion time until the film is formed.
However, the data depends on the actual film production for the target 72 hours, but if decomposed products leak out, film production must be interrupted, the inside of the extruder must be cleaned or disassembled and cleaned, and then film production must be continued again. In this case, data on the outflow of decomposed products caused by the interruption time and insufficient cleaning inside the extruder at the time of starting film production shall be excluded from the calculations. Evaluation scale, evaluation symbol Average time until decomposition products flow out ◎; 24 hours or more ○; Less than 24 hours to 8 hours or more △; Less than 8 hours to 1 hour or more ×; Less than 1 hourb Puncture incidence Inflation This is an attempt to evaluate the continuous sustainability of inflation film formation, and is based on the average rate at which bubbles break during inflation due to abnormalities other than the above-mentioned decomposed products (e.g. bubbles, outflow of unmelted materials, etc.) It is expressed in units of time. Note that the data calculation procedure is in accordance with the above section a. Evaluation scale, evaluation symbol, average number of occurrences per hour ◎; Less than 0.1 times 〇; 0.1 times or more to less than 0.3 times △; ; 0.3 times or more to less than 2 times ×; 2 or more times c Extrusion amount unevenness, occurring during extrusion This is an attempt to evaluate an extruder in the direction of the extrusion axis (which causes uneven thickness in the longitudinal direction of the film).
The cutting operation was continuously repeated at intervals of seconds to obtain 10 cut extruded pieces, and the weight of each piece was accurately measured.
Calculate the ratio of the difference between the maximum and minimum weights to the average weight of the 10 pieces as a percentage. Evaluation scale Evaluation symbol, size of spots, ◎ Less than 2% 〇 2% or more to less than 4% △ 4% or more to less than 7% × 7% or more D Thick spots in the width direction Cylindrical extrudate cooled in a cooling tank Measure the wall thickness with a micro gauge at 50 points equally spaced in the circumferential direction.
The standard deviation of the thickness variation was calculated and shown. d Thickness in the width direction The uniformity of the thickness in the width direction of the cylindrical extrudate before stretching is
After setting the temperature of the die in advance to an intermediate temperature between the temperature at which the resin stagnates in the die and the temperature at which thermal decomposition of the resin occurs, according to the characteristics of each evaluation resin, The gap between the slits of the die was sufficiently adjusted based on the knowledge of extrusion molding of vinylidene chloride-vinyl chloride copolymer, and the wall thickness of the cylindrical extrudate cooled in the cooling tank was made evenly spaced in the circumferential direction. The thickness was measured at 50 points using a micro gauge (based on ASTM, D.374), and the standard deviation of the measured thickness at the 50 points was calculated using the following formula, and the standard deviation was multiplied by 3. Here, x _i means each measured thickness, n means the average thickness, and n means the number of measurement points, that is, 50. Evaluation scale Evaluation symbol Size of thick spot ◎; Less than 0.05 mm〇; 0.05 mm or more to less than 0.1 mm △; 0.1 mm or more to less than 0.2 mm The objective is to evaluate the uniformity of the thickness of the resin, and the temperature conditions of the cooling tank and the circumferential speed ratio of the pinch rolls are adjusted in advance so that a predetermined vertical and horizontal stretching ratio is obtained according to the characteristics of each resin. After setting, the thickness of the cylindrical film was measured by peeling off the two layers of film again and measuring the thickness using a dial gauge [ASTM.D.374] at 50 points equally spaced in the circumferential direction.
The standard deviation of the measured thickness at 50 points was calculated using the formula explained in section D, and the standard deviation was multiplied by 3. Evaluation scale Evaluation symbol Size of thick spot ◎; less than 1 micron 〇; 1 micron or more - less than 2 micron △; 2 micron or more - less than 4 micron ×; 4 micron or more (2) evaluation. The outline of the extrusion-film forming method is as follows. In Figure 8, three extruders 20, 21, 22
Three types of resins, polypropylene (PP), ethylene-vinyl acetate copolymer (EVA),
Vinylidene chloride-methyl acrylate copolymer (VDC-MA) was added to the feed port block 23.
In this part, PP/EVA/VDC-MA/
A resin block-like material is made by laminating EVA/PP in this order, and this is introduced into the T-die 24 (width 2000 mm, slit gap 3 mm), developed into a sheet, and coextruded. Cool it with
On the winding shaft 27 of the winding machine 26, a width of 1950 mm and a wall thickness of 65 mm are mounted.
Micron [layer structure, PP (20μ)/EVA (5μ)/
VDC-MA (15μ) / EVA (5μ) / PP (20μ)] Wind it up as the target 5-layer laminated film. The length (L)/diameter (D) of the extruder used was as follows: [3120mm/120mm] = 26, [1080mm/60mm] = 18,
[1600mm/80mm] = 20 and the target total extrusion amount is 250
Kg/Hr. The outline of the evaluation method is as follows. An experimental sample prepared by workers skilled in VDC-VC coextrusion film forming experiments was prepared, and for each of the resins to be tested, the extrusion temperature at which the above-mentioned five-layer coextrusion laminated film could be formed was set and stabilized. After confirming that the desired film can be formed, the VDC-MA extrusion temperature is shifted by 5°C on both sides of the set extrusion temperature (temperature change rate 1°C/1).
Repeat the process (dividing) to create a cross-section of the formed film.
To determine the allowable change range of extrusion temperature that can be extruded without disturbing the VDC-MA layer, and to obtain a laminated film formed at approximately the median extrusion temperature of the allowable change range, 8 Stretch the film twice (stretching temperature 130°C), measure the oxygen permeability (ASTM.D.1434) of the film before and after stretching, and measure the rate of change in oxygen permeability (converted to thickness) due to stretching (rate of improvement in barrier properties). and reduction rate) was taken as the lamination stretchability. f Allowable range of change in extrusion temperature Evaluation symbol Allowable temperature range ◎; 20°C or more 〇; Less than 20°C to 10°C or more △; Less than 10°C to 5°C or more ×; Less than 5°C Improvement rate of 10% or more ○; Improvement rate of less than 10% to 0% △; Decrease rate of less than 10% ×; Decrease rate of 10% or more Overall evaluation Evaluation of the 7 items a to g above The results were comprehensively examined and divided into the following four stages. Evaluation symbol: ◎: There is sufficient confidence in production using industrial equipment. 〇: Possible to produce in industrial equipment by partially changing the design △: Unsuitable for production in industrial equipment (somehow impossible for experiments in small equipment) ×: Obtaining molded products The VDC-MA resin used in the experiment and its manufacturing method are as follows. Methyl cellulose 11Kg, ethylenediamine 7.5
Capacity 30 containing 11000Kg of aqueous solution containing Kg
A polymerization reactor containing 15 kg of diisopropyl peroxydicarbonate dissolved in 7,500 kg of a mixed monomer of vinylidene chloride monomer and methyl acrylate monomer (weight ratio 90, 10) was loaded into a ³ m3 polymerization vessel under reduced pressure, and a Feudler-type stirring blade was installed. Suspension polymerization was carried out while stirring with a stirrer. The polymerization temperature started at 30℃, 4 hours at 30℃, and a heating rate of 1℃/1℃ to 40℃.
Polymerization was carried out at a heating rate of 1.5°C/hour until 55°C, and a copolymer with a polymerization rate of 97% was obtained over a total polymerization time of 24 hours. Let resin be the symbol resin). The above polymerization conditions (temperature and time) were changed to change the average molecular weight, and in the same manner, the symbols,...
, , were polymerized. Next, the mixing ratio of vinylidene chloride monomer and methyl acrylate was changed to a weight ratio of 97; 3, 92.5; 7.5, 85; ,,,
XI and XII. The compositions and properties of the 12 resins produced by polymerization are as shown in Table 1.

[Table] Experimental example 1 For each of the six types of resins with symbols ~ in Table 1,
Epoxidized linseed oil 1% by weight, magnesium oxide
Add and mix 0.4% by weight (both are heat stabilizers),
Using this resin, an experiment was conducted to evaluate productivity in industrial equipment using the single-layer film production equipment described in the text. The results are very disappointing, as shown in Table 2. Some resins cannot be extruded stably and the experiment has to be stopped, and even if some resins can be extruded, most resins cannot be made into a film. Finally, it seemed that we had finally completed the evaluation of the possible evaluation items. Just to be sure, we also conducted an evaluation using five-layer laminated film production equipment, but only the resin with the symbol was found to be usable for use in lamination, and no promising results were obtained. I couldn't help it. Table 2 summarizes these results.

【table】

【table】

【table】

[Table] (Example) Example/Comparative Example 1 A total of 11 types of mixed resins A to K were created by mixing two to three resins with symbols ~ in Table 1 above.
In the same manner as in Experimental Example 1 described above, we repeated experiments to evaluate productivity in industrial equipment (see Table 3). Surprisingly, the results showed that in Experimental Example 1, even the evaluation was difficult. It is a fact that by mixing resins in appropriate proportions, resins can be transformed into resins that can be produced in industrial facilities. Table 3 shows the inventors' hypothesis that the root of the above surprising fact is that the molecular weight in VDC-MA is 2.
This was compiled based on the hypothesis that the copolymer content is related to the magnitude of the copolymer content of 1,000 or less, and the results of Table 2 (Experimental Example 1) were added to the results of Example/Comparative Example 1. This is a breakdown table that evaluates the results using the comprehensive evaluation scale described in the text. However, the results in Table 3 do not make clear the regularity of the above hypothesis. Figure 1 is a more complicated breakdown diagram of the results in Table 3. The horizontal axis shows the weight average molecular weight of the resin (logarithmic scale), and the vertical axis shows the weight average molecular weight of the resin (copolymer). The content of the copolymer with a molecular weight of 20,000 or less (logarithmic scale) contained in the above is indicated by the symbol of the overall evaluation result (◎, 〇, △, × mark) in Table 3 on the rectangular coordinate scale. The results are plotted as coordinate points of the copolymer. According to Figure 1, the technical concept for adjusting resins that could not be produced using industrial equipment (marked with △ and ×) by replacing them with those that were possible (marked with ◎ and ○) is clear. The idea is to place the resin component of VDC-MA at point A [7 18,000,000, point B [15]
10,000,4], point C [250,000,4], and point D [120,000,18]. More preferably, point E [80,000,
14], point F [105,000, 8], point G [130,000, 8], point H
It has been proven that the copolymer can be adjusted to form a copolymer within the range of the quadrilateral connecting the four points [100,000, 14]. Also, note that these copolymers in the quadrilateral range of E, F, G, and H have a value of 2 to 2.4 in terms of weight average number of molecules divided by number average molecular weight. be done. Examples/Comparative Examples ~2 Six types of resins with symbols ~XII in Table 1 were evaluated for productivity in the same industrial equipment as in Experimental Example 1. The results were the same as those in Experimental Example 1, and were in a state that could not be used for production (see Table 4). Next, combine two or more of the resins listed in ~XII above.
The component composition of VDC-MA is VDC:MA weight ratio: 97, 3, 92.5, 7.5, 90, 10, 85, 15, 95,
The mixture was adjusted to the proportions shown in Table 4 so that the total amount was 5. The components and properties of this mixed resin are shown in Table 4.
Shown as resin with symbols 2X, 3X, 4X, 5X, 6X. Six types of mixed resins 2X to 6X in Table 4 were evaluated for productivity in industrial equipment in the same manner as above. Similar to the results obtained in Example and Comparative Example 1, the results showed a surprising phenomenon in which the evaluation of production impossibility changed to that of production.According to the results in Table 4, the technical idea of the present invention , that is, under a specific range of weight average molecular weight, VDC-
The advantage of adjusting the content of the copolymer with a molecular weight of 20,000 or less in the MA copolymer to fall within the range of 4 to 18% is common to a wide range of different component ratios of VDC and MA. It has been proven that it can be applied.

【table】

[Effects of the present invention]

As has been clarified above, by having the above-described structure, the present invention makes it possible to stably supply VDC-MA extrusion molded products with industrial equipment at a quality level that meets market demands. Ta. Moreover, the method of the present invention is designed to extract the quality of the VDC-MA material itself, so it is possible to create new materials that exhibit high barrier properties, high levels of heat shrinkability, or in some cases, stretch properties. Highly useful as a resin material. Moreover, the present invention is suitable for extrusion molding in industrial equipment.
Since this invention gives a single target value to the VDC-MA resin composition, it is an excellent invention that will play a large role in industry, having a large impact on the future development and improvement of polymerization conditions.

[Brief explanation of drawings]

Figures 1 to 6 are experimental diagrams explaining the technical content of the present invention; Figure 1 is an exploded diagram; Figures 2, 3, 4, 5, and 6 are
The figures are characteristic diagrams showing the usefulness of each film obtained, and Figures 7 and 8 are conceptual diagrams of the apparatus used for evaluation.

Claims (1)

[Scope of Claims] 1. A vinylidene chloride-methyl acrylate copolymer is supplied to an extruder, melt-kneaded and extruded into a desired shape, and stretched as necessary to form a sheet, film or container shape. In the melt extrusion processing method of vinylidene chloride-methyl acrylate copolymer to be molded, the vinylidene chloride-methyl acrylate copolymer has an MA component of 3 to 15 per 100 of the copolymer.
The weight average molecular weight measured by weight percentage and GPC method (gel permeation chromatography method) is 70,000 to 250,000, and the molecular weight contained in the copolymer is 20,000 or less (according to the same GPC method). The relationship with the copolymer content is expressed in double logarithmic orthogonal coordinates, with the above average molecular weight on the horizontal axis (logarithmic scale) and the copolymer content of 20,000 or less on the vertical axis (logarithmic scale). , Point A [70,000,18], Point B [150,000,4], Point C [25]
Vinylidene chloride-methyl acrylate copolymer adjusted to satisfy the relationship within the range of the quadrilateral formed by connecting the four coordinate points of point D [120,000, 4] and point D [120,000, 18] with straight lines. A method for molding a vinylidene chloride-methyl acrylate copolymer using a melt extrusion method, characterized by using