JPH0362733B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention is a thermoformable laminated sheet or film that is laminated with a thermoformable sheet or film of another resin and has gas/steam barrier properties. This article relates to improved technology for resins and unstretched sheets and films for lamination. [Prior art] Vinylidene chloride resin/unstretched film for lamination, which is used as a barrier layer for thermoforming laminated sheets/films (hereinafter referred to as films), is known as, for example, "unstretched Saran film (trade name, manufactured by Asahi Kasei)". It is commercially available and known. This material is a vinylidene chloride/vinyl chloride copolymer resin with a vinyl chloride component of about 10% by weight, and contains about 7% by weight of a liquid plasticizer as a modifier, so the amount of oxygen permeation per 10 micron thickness is It is known to be a transparent (HAZE 3%) unstretched film with a gas barrier property of approximately 30 c.c. In addition, this product can be manufactured using the manufacturing method shown in Figure 3 of the advertising specification of Canadian Patent No. 713477, that is, between two resin layers such as polyethylene, which does not bond well with vinylidene chloride resin. , a production method in which the vinylidene chloride resin layer is stretched and coextruded with the vinylidene chloride resin layer sandwiched between them, cooled and wound as is, and the wound film is later peeled off into three pieces to take out a flat, unstretched vinylidene chloride resin film. is used. The reason for this is that the resin, which is easy to thermally decompose and difficult to stretch, can be thinned without decomposition by using the extrusion extensibility of other resins with a smaller amount of plasticizer, and the crystal solidification is slow and can last forever. This is said to be a device to protect a thin layer that is soft and difficult to deform from external forces and to solidify the film. It is also known that this manufacturing method has the advantage of transferring and absorbing the plasticizer in the vinylidene chloride resin layer to the outer layer, reducing the amount of plasticizer in the vinylidene chloride resin layer and improving gas barrier properties. ing. The above-mentioned unstretched film for lamination, carefully produced by such a method, has been utilized as a core material for laminated films for molding, and has come to be widely used in various molding fields with the help of advances in molding technology. [Problems to be Solved by the Invention] However, this unstretched film for lamination has the following three problems. 1 The level of gas barrier properties is rather low, and at least the oxygen permeability per 10 micron thickness is required to be 10 c.c. or less, but the current value is 30 c.c.
In order to improve the gas barrier property, it is necessary to reduce the amount of liquid plasticizer added.
There are ways to make up for this deficiency by adding plasticized resins [for example, "Unstretched Saran Film" C5H (trade name, manufactured by Asahi Kasei)], but with these products, the film quality becomes cloudy and opaque. , cannot be applied to this field. 2 In the field of deep drawing, a molding failure phenomenon occurs in which the vinylidene chloride resin layer breaks, especially at the wall where the local drawing ratio becomes large.This phenomenon also affects the plasticity of the vinylidene chloride resin layer. It can be predicted that this can be corrected by raising the level, but since the barrier properties are already below the target level, this is a problem that cannot be addressed. 3. When trying to make a laminated product, there are unstretched parts of the laminated resin on the unstretched film, or uneven and wrinkled parts, which cannot be completely laminated, resulting in a defective product. The reason for this is that the vinylidene chloride resin does not solidify properly during the production of unstretched film (currently
This is due to a defective phenomenon that occurred during the peeling process. Therefore, an object of the present invention is to solve the above-mentioned problems, that is, to provide a non-stretched vinylidene chloride resin film that can improve the above-mentioned problems. [Means for Solving the Problems] Explaining the requirements of the structure of the present invention according to its role, the main part for solving the problems is the “methyl acrylate” described in the claims. The component is a non-stretched sheet/film consisting of 4 to 8% by weight of vinylidene chloride/methyl acrylate copolymer resin and having a residual content of liquid plasticizer of 4% by weight or less. And following this, “Transparency (HAZE value) is 10%
Below, the section "Unstretched sheets/films for lamination with a heat shrinkage rate of 5% or less at 90℃ and a wall thickness of 10μ to 100μ" refers to the films in question that have been manufactured during the manufacturing process for lamination without devitrification or whitening. It is clarified that the film has been formed as a non-stretched film with a shrinkage rate adjusted to facilitate lamination and thick enough to be used in the field of lamination molding. Therefore, this requirement is the part that guarantees the basic quality of the laminate molded product. That is, for example, if the finished unstretched film has a HAZE value of more than 10%, the resulting molded product will be opaque and not practical in this field, and the heat shrinkage rate at 90°C will be low. is 5
Of course, if it exceeds 10%, the heat shrinkage strength (ORS) will also be 10.
Since the weight is higher than Kg/ ^cm2 , the heating during lamination may cause interlayer displacement.
This means that if the wall thickness is less than 10μ or more than 100μ, where defects are likely to occur, it is no longer suitable for the layered molding field. The meaning of the above important requirements will be explained in detail below using drawings and the like. FIG. 1 is an experimental diagram showing the dissipation rate of the plasticizer contained in the vinylidene chloride resin used in the present invention. The horizontal axis is the amount (wt%) of the plasticizer initially contained in the resin, and the vertical axis is the plasticizer dissipation rate calculated from the amount of plasticizer remaining in the final unstretched film. The solid line shows the case of the resin used in the present invention (5% methyl acrylate component), and the broken line shows the case of the conventional commercially available film resin (10% vinyl chloride component). In both cases, the vinylidene chloride resin layer is laminated with polyethylene resin on both sides, stretched in a die, extruded from a T-die into a plate shape so that the vinylidene chloride resin layer has a thickness of approximately 30μ, and cooled. Roll it up, peel it off after 3 days and coat it with vinylidene chloride resin.
This is an analysis of the unstretched film taken out. The results shown in FIG. 1 indicate that the vinylidene chloride resin used in the present invention has a greater plasticizer escape rate during processing than conventional products. or,
In the present invention, by utilizing this phenomenon tendency of resin, we compensate for the processing suitability of resin that tends to be insufficient by adding a large amount of plasticizer to the extent possible during extrusion-film forming processing, and on the other hand, as an unstretched film. The amount of plasticizer is brought to a level that provides excellent gas barrier properties and excellent moldability at the time of removal. The completion of an invention lies in the investigation of such points of harmony. FIG. 2 shows examples of molding defects that tend to occur in molding in this technical field, and figures A, B, and C show the magnitude of the defects in order. Figure 3 is an enlarged sketch (approximately 40x) showing the causes of the black streaks on the molded container in A, B, and C of Figure 2. It depicts the vinylidene chloride resin layer being broken. The purpose of improving formability in deep drawing in the present invention is to eliminate such phenomena and expand the suitable temperature range for forming. Figure 4 shows the analysis results, where the vertical axis shows the amount of plasticizer remaining in the film (wt%) when the film was unstretched, and the horizontal axis shows the amount of methyl acrylate component in the film resin layer (wt%). . In Figure 4, the plot points in the figure represent the relationship between the symbols in the comprehensive evaluation section of Table 1, which summarizes the results of Examples and Comparative Examples, and the methyl acrylate component of the target film and the amount of residual plasticizer. This is an analysis diagram drawn at the coordinates of , together with the experiment number. The arrows indicate changes from the initial amount of plasticizer added to the resin. Note that the amount of methyl acrylate located in the middle is based on calculation from the mixing ratio. According to the results shown in Figure 4, the level of gas barrier properties is maintained, moldability is improved, the appearance quality of the finished molded product is maintained, and processability during film formation and holding time until peeling are shortened. , eliminating film wrinkles and peeling defects, etc., all of which can be achieved at a high level, have a methyl acrylate content of 4 to 8% by weight.
It can be seen that the amount of residual plasticizer is 4% by weight or less, and the length of the arrow is long, that is, the product was initially processed with a large amount of plasticizer, and then it was dissipated. However, in order to achieve the objectives of the present invention, that is, to improve the level of gas barrier properties, the level of improvement in moldability, and the defective removal of wrinkles from the film, the amount of thylacrylate is 4 to 8% by weight and the amount of residual plasticizer is 4% by weight. It has also been shown that the purpose can be fully achieved if it is guaranteed that the amount is less than %. The present inventors have discovered that the following phenomena occur regarding the amount of plasticizer dissipation that affects processability during film formation, elimination of film wrinkle defects due to unremovable film, and shortening of holding time until peeling off. I guess. In other words, the excess plasticizer that first plasticizes the resin and makes it easier to stretch is extruded from the vinylidene chloride resin layer and oozes out due to the progressing crystallization of the resin and the suction action of the adjacent resin, but it oozes out from the vinylidene chloride resin layer. Since the entire amount cannot be absorbed in a short time, it accumulates between the vinylidene chloride resin layer and the adjacent resin. On the other hand, vinylidene chloride resin that has undergone crystallization becomes a layer that is firm and resistant to deformation due to the resin properties of the methyl acrylate component. It is speculated that the phenomenon of peeling occurs there. The liquid plasticizer used in the present invention refers to a liquid plasticizer known as a plasticizer for vinyl chloride resin. Among them,
From the viewpoint of food safety and hygiene, aliphatic dibasic acid esters, citric acid esters, fatty acid esters,
Carefully selected from liquid plasticizers such as polyester. Qualitative and quantitative determination of plasticizers can be carried out using a gas chromatograph and a mass spectrometer using the solvent extraction method described in analytical publications such as "Polymer Analysis Handbook" (edited by the Japan Society for Analytical Chemistry, 1985). . The plasticizer dissipation rate is the ratio (wt%) of the amount of plasticizer (B) dissipated during the extrusion-laminated film-forming-stripping process to the initial content (A), i.e., the plasticizer dissipation rate. (% by weight)=B/A×100=Amount of plasticizer in raw resin (% by weight)−Amount of plasticizer in film (% by weight)/Amount of plasticizer in raw resin (% by weight)×100. In addition, the thermoplastic resin used for both outer layers, which is peeled off after forming a three-layer structure with vinylidene chloride resin as the core layer, does not exhibit sufficient thermal adhesion to the vinylidene chloride resin, and the extrusion temperature is too high for chloride. There is no particular limitation as long as it does not promote thermal deterioration of the vinylidene resin, but it is preferable to use a polyolefin resin from the viewpoint of repeated reuse or the usability of the film after peeling off. More preferably, low density polyethylene is used. The evaluation method and evaluation scale used in the present invention are shown below. [] Suitability for film forming processing When forming a laminated film containing an unstretched vinylidene chloride resin film, the generation of bubbles due to carbon and thermal decomposition was observed with the naked eye, and the time required until generation was recognized was evaluated as follows. It was evaluated using a scale. Evaluation symbol Evaluation scale ◎; 6 hours or more ○; 3 hours or more and less than 6 hours △; 1 hour or more and less than 3 hours ×; less than 1 hour Store it at 20℃ and cut it out into 100mm wide, 2m strips over time.
The length of the film taken out at a peeling speed of 5 m/min is 3% of the length in the laminated state.
The elapsed time required until the increase was suppressed to the following was evaluated using the following evaluation scale. Evaluation symbol Evaluation scale ◎; Less than 1 day ○; 1 day or more and less than 3 days △; 3 days or more and less than 7 days ×; 7 days or more [] Film wrinkles When rewinding the obtained unstretched vinylidene chloride resin film alone Diameter heated to 120℃
60 by contacting a 250mm heat roll at a holding angle of 90°.
While running at a speed of m/min, vertical wrinkles at the winding section and horizontal wrinkles at the edges were observed with the naked eye, and the number of wrinkles occurring per 100 m was evaluated using the following evaluation scale. Evaluation symbol Evaluation scale ◎; No occurrence ○; 1 to 2 occurrences △; 3 to 5 occurrences ×; 5 or more occurrences [] Strippability Obtained unstretched vinylidene chloride resin with a width of 1000 mm The film was rewound 100 m, and during this time the film surface was observed with the naked eye, peeling defects were counted, and evaluation was made using the following evaluation scale. Evaluation symbol Evaluation scale ◎; No defects at all ○; 1 to 5 defects △; 6 to 10 defects ×; 11 or more [] Gas barrier property Obtained unstretched vinylidene chloride resin film for evaluation MOCON according to ASTM D-3985
Oxygen gas permeability was measured using an OXTRAN 100 model at 20°C and 65% RH, and evaluated using the following evaluation scale. Evaluation symbol Evaluation scale (unit cc/ ^m2.day.atm ) ◎; 6 or less ○; More than 6 and less than 10 △: More than 10 and less than 15 ×; More than 15 and high [] Formability Evaluation target After laminating a 500μ unstretched polypropylene sheet (manufactured by Mitsui Toatsu Co., Ltd.) and a 50μ unstretched polypropylene film (manufactured by Tocello Co., Ltd.) on both sides of the unstretched vinylidene chloride resin film using adhesive to make a total of three layers. Plug assist molding was performed using an Erich molding machine, and each item of appearance quality type reproducibility and molding reversion resistance was evaluated. The heating temperature of the sheet is determined by the discoloration of the heat label attached to the edge of the sheet, and the heating level is determined by
150~160℃, 165~175℃, 180~190℃,
Using a cylindrical mold with right angle corners, the drawing ratio (mold depth ÷ opening diameter) was set to 4 levels of 195 to 205℃, 0.3, 0.6, 0.9, 1.2, and 1.5.
5 levels. Appearance Quality The molded articles molded into container shapes by varying the heating temperature and drawing ratio were visually observed from the bottom to evaluate the presence or absence of defects in appearance as illustrated in FIG. 2. The breadth of the range of heating temperature and drawing ratio in which this defect does not occur was evaluated using the following evaluation scale. Evaluation symbol Evaluation scale ◎; Heating rank level 3 or higher Drawing ratio rank or higher ○; Heating rank level 3 or higher Drawing ratio rank or heating rank 2 level Drawing ratio rank or higher △; Heating rank level 3 or lower Drawing ratio rank ×; Heating rank level 3 Below drawing ratio rank: Mold reproducibility Measure the degree of determination of the bottom corners of the container-shaped molded product obtained from the outside of the container using an R gauge, and find the heating temperature and drawing ratio that will make the corners of the molded product have a roundness of 5 mm or less. The breadth of the range was evaluated using the following evaluation scale. Evaluation symbol Evaluation scale ◎; Heating rank level 3 or higher Drawing ratio rank or higher ○; Heating rank level 3 or higher Drawing ratio rank or heating rank 2 level Drawing ratio rank or higher △; Heating rank level 3 or lower Drawing ratio rank ×; Heating rank level 3 The outside diameter of the bottom of the container-shaped molded product obtained is measured, and this value is divided by the inside diameter of the mold.
The breadth of the range of heating temperature and drawing ratio of 0.95 or more was evaluated using the following evaluation scale. Evaluation symbol Evaluation scale ◎: Heating rank is level 3 or above and drawing ratio rank is above ○; Heating rank is level 3 or above and drawing ratio rank is above, or heating rank is level 2 and drawing ratio rank is above △ ; Heating rank is level 3 or below and the drawing ratio rank is below ×; Heating rank is level 3 or below and the drawing ratio rank is below Emphasis was placed on barrier properties, poor peeling, film wrinkles, moldability, and quality, and the degree of sufficiency was evaluated using the following scale. Evaluation scale Evaluation symbol All items are ◎ or ○, and the number of ○ is 2 or less ◎ All the items are ◎ or ○, and the number of ○ is 3 or more ○ △ in 1 item △ × in 1 item × The content of the present invention will be explained in detail in the following Examples and Comparative Examples. Examples and Comparative Examples Vinylidene chloride resin, which is the base resin used for evaluation, is a copolymer resin of vinylidene chloride and methyl acrylate, and each component in the resin, vinylidene chloride to methyl acrylate, is 97:3 (wt%, The same applies hereafter) to 91:9,
All of these can be obtained, for example, by the method described in Japanese Patent Application No. 59-240483.
1.0% by weight of epoxidized linseed oil was used. A liquid plasticizer prepared by mixing diisobutyl adipate and tributyl acetyl citrate in a weight ratio of 60:40 (wt%) to the above base resin,
A vinylidene chloride resin composition was prepared in which the amount added corresponded to the starting point of the arrow in FIG. 4. These compositions were sequentially melt-extruded using an extruder with a diameter of 90 mm and L/D: 24, while ASTM D-
1238, low-density polyethylene with a melt index of 2.5 measured at 190°C and a load of 2.16 kg is melt-extruded using an extruder with a diameter of 120 mm and L/D: 22, and both molten resins are manufactured by, for example, the Dow Chemical Company in the United States. Using a laminating device such as a feed port block, vinylidene chloride resin is laminated into a three-layer structure with a core layer, and then the T-die casting method is used to form a 1200 mm
It was rolled up as a 3-layer film with a width of mm. At the time of extrusion film formation, film forming processability was evaluated using the evaluation method and evaluation scale described in the text. The obtained laminated film was stored in an atmosphere of 20℃, and the peeling retention time was evaluated using the evaluation method and evaluation scale described in the text, while keeping up with the aging based on the plasticizer dissipation rate data obtained in preliminary experiments. sequentially
An unstretched vinylidene chloride resin film with a width of 1000 mm was taken out. All of the obtained unstretched films were transparent (HAZE value 7% or less as measured by ASTM D-1003).
No heat shrinkage (90℃ according to ASTM D-2732)
The shrinkage rate was 3% or less). The peeling defects, film wrinkles, and barrier properties of these unstretched films were evaluated according to the evaluation method and evaluation scale described in the text, while the residual plasticizer was measured on the parts where both surfaces of the film were wiped with ethyl alcohol. It is shown in Table 1 along with the experiment number. Furthermore, regarding the moldability of the film, the items of appearance quality, mold reproducibility, and mold reversion resistance were evaluated in accordance with the evaluation method and evaluation scale described in the text from the viewpoint of a wide range of possible conditions. Table 1 shows the above evaluation results along with the ratio of each component and residual plasticizer of the vinylidene chloride/methyl acrylate copolymer resin film. Since it is difficult to understand useful factors using only the evaluation table in Table 1, an analytical diagram is shown in FIG. 4 to clarify the relationship between the content of the methyl acrylate component and the amount of residual plasticizer. The results of this evaluation and analysis show that if the methyl acrylate component is too small (less than 4% by weight), the film forming processability, the appearance quality of the molded product, and the mold reproducibility are likely to be impaired, whereas if it exceeds 8% by weight, It can be seen that if the amount is too large, the peeling retention time, peeling defects, film wrinkles, and mold reproducibility become worse. Furthermore, it can be seen that if the residual plasticizer is too large, exceeding 4% by weight, not only the molding reversion is deteriorated but also the target barrier properties are likely to be impaired. From the above, if the amount of methyl acrylate component in the copolymer resin is in the range of 4 to 8% by weight, and the amount of residual plasticizer is in the range of 4% by weight or less, high standards can be maintained in all evaluation items. I understand. As is clear from the above, the embodiment of the present invention is the first embodiment.
Experiment No. 5, 6, 7, 10, 11, 14, 16, 17, 18 in the table
The comparative examples are the same experiment Nos. 1, 2, 3, 4, 8,
9, 12, 13, 15, 19, 20, 21, 22.

【table】

〔Effect of the invention〕

By adopting the above-described structure, the present invention can be applied to commercially available films such as "unstretched Saran film" C2M,
It can be transparent, which C5H (product name, manufactured by Asahi Kasei Corporation) etc. could not achieve, and realizes advanced barrier properties and an expanded range of suitability for deep drawing, and at the same time greatly improves workability in film forming processing. This invention is extremely useful industrially as an unstretched vinylidene chloride resin film for molding, which improves the properties of the film.

[Brief explanation of drawings]

FIG. 1 is an experimental diagram showing the dissipation rate of plasticizer.
FIG. 2 is a perspective view of a molded product showing a state of defective molding. FIG. 3 is an enlarged cross-sectional view (approximately 40 times) of the defective portion shown in FIG. 2. FIG. 4 is an analytical diagram of the experimental results.

Claims (1)

[Claims] 1. An unstretched film for lamination made of vinylidene chloride resin, consisting of a vinylidene chloride/methyl acrylate copolymer resin with a methyl acrylate component of 4 to 8% by weight, and a liquid plasticizer remaining in the film layer of 4% by weight or less. An unstretched sheet for lamination made of vinylidene chloride resin, which has a transparency (HAZE value) of 10% or less, a heat shrinkage rate at 90°C of 5% or less, and a wall thickness in the range of 10μ to 100μ.・Film.