JP3438958B2 - Laminated sheet - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in surface gloss and thermoformability which can be used for food packaging containers such as lunch containers, food packs, and general packaging containers. To a laminated sheet. 2. Description of the Related Art In the field of thermoforming, a laminated sheet formed by laminating an unstretched polypropylene film (hereinafter referred to as a CPP film) on a polypropylene sheet is known. The CPP film used here is used for the purpose of imparting gloss to the surface of a molded article. However, in the sheet forming temperature range, the original gloss of the CPP film is reduced, and there is a drawback that a desired molded article with high gloss cannot be obtained. In addition, when a sheet is pressed or vacuum formed, a phenomenon in which the central portion of the sheet sags after heating (hereinafter referred to as drawdown) occurs. As a method for reducing the drawdown, a CPP film is used, but its effect is insufficient. [0003] An object of the present invention is to provide a laminated sheet that prevents drawdown and has good moldability and a glossy surface. [0004] The present inventors have continued to study polyolefin films laminated on polypropylene sheets. As a result, it has been found that when the biaxially oriented polyolefin film laminated on the polypropylene sheet has an appropriate elastic modulus and elongation, drawdown can be prevented, and a glossy thermoforming laminated sheet with good moldability can be produced. Was. That is, the present invention relates to (1) an ethylene-propylene copolymer having an ethylene content of 1 to 4% by weight, or an ethylene content of 0.5 to 3.0% by weight and butene-
1 content 4 to 15% by weight of an ethylene - butene - consists propylene copolymer, the draw ratio 3 to 4 times in the MD direction, T
It is biaxially stretched at a draw ratio of 8 to 12 times in the D direction, and has an elongation of 30 to 15 at a tensile strength of 5 kg / mm ² in the MD direction
0%, tensile modulus in MD direction is 80 ~ 130kg
/ Mm ² and biaxially oriented polyolefin film having a thickness of 15~120μm is (2) and polypropylene sheet having a thickness 0.2~1mm is a laminated sheet for thermoforming, characterized in that formed by laminating. JP-A-3-288641 discloses a method for obtaining a laminated sheet by laminating a biaxially stretched polypropylene film (hereinafter referred to as an OPP film) on a polypropylene sheet having a crystalline state of a smectic structure. I have. However, the properties of the biaxially stretched polypropylene film are not specifically disclosed. However, it is described that the stretching ratio of the OPP film is 1.2 to 7 times, and preferably 1.5 to 5 times in both the vertical and horizontal directions. It is not possible to obtain a biaxially stretched polypropylene film having a specific elastic modulus and elongation rate. The biaxially stretched polyolefin film used in the present invention is an ethylene-propylene copolymer having an ethylene content of 1 to 4% by weight, or an ethylene content of 0.5 to 3.0% by weight and butene. 1 content 4 to 15
% By weight of an ethylene-butene-propylene copolymer (hereinafter also referred to simply as a polyolefin-based copolymer). The ethylene-propylene copolymer used in the present invention is a random copolymer having an ethylene content of 1 to 4% by weight, preferably 1.5 to 2.5% by weight,
The ethylene-butene-propylene copolymer has an ethylene content of 0.5 to 3.0% by weight and a butene-1 content of 4 to 15% by weight, preferably an ethylene content of 1.0 to 1.0%.
It is a random copolymer having about 2.0% by weight and a butene-1 content of 7% to 10% by weight. In the above-mentioned ethylene-propylene copolymer and ethylene-butene-propylene copolymer,
When the amount of ethylene or the amount of butene-1 is less than the above range, the film itself becomes too hard, and the elongation at a tensile strength of 5 kg / mm ² in the MD direction is 30 to 150%.
And the tensile modulus in the MD direction is 80 to 130 k.
g / mm ² is not preferred because a film of g / mm ² cannot be obtained. On the other hand, when the amount of ethylene or the amount of butene-1 is larger than the above range, gloss is insufficient as in the case of the CPP film, and drawdown frequently occurs. The polyolefin-based copolymer used in the present invention is in a range that does not impair its physical properties, for example, 5
Α- except for ethylene, butene and propylene within mol%
An olefin may be included as a copolymer component. Further, a mixture of the above-mentioned polyolefin-based copolymer or a mixture of the above-mentioned polyolefin-based copolymer and another polyolefin can also be used. When mixing the polyolefin-based copolymers, the mixing ratio is arbitrary. When the polyolefin-based copolymer is mixed with another polyolefin, it is preferable that the content of the polyolefin-based copolymer be 70% by weight or more and the other polyolefin be 30% by weight or less in order to obtain the effects of the present invention. . Other polyolefins include polyethylene, polypropylene, polybutene and the like. The melt index of the polyolefin-based copolymer used in the present invention and its mixture is not particularly limited, but in order to impart good film formability, it is 0.5 to 10 g / 10 min, and further 1 to 7 g. / 10 minutes is preferable. The biaxially oriented polyolefin film used in the present invention has a tensile strength in the MD of 5 kg / mm.
The elongation at ² is 30 to 150%, preferably 80 to
130%, and the tensile modulus in the MD direction is 80 to 130.
kg / mm ^2, preferably 90~120kg / mm ^2. Note that the MD direction is a winding direction of the biaxially stretched polyolefin film. MD direction tensile strength 5kg / m
the elongation at m ² is less than 30%, or
If the tensile modulus in the MD direction is larger than 130 kg / mm ² , it is not preferable because the elongation percentage of the OPP film is insufficient if the drawn product of the molded product is large, resulting in poor moldability. On the other hand, the elongation at a tensile strength of 5 kg / mm ² in the MD direction is greater than 150%, or the tensile modulus in the MD direction is 80 kg / mm ^2.
If it is smaller than this, the gloss is insufficient as in the case of the CPP film, and drawdown occurs, which is not preferable. The biaxially rolled polyolefin film used in the present invention is biaxially stretched. Stretch ratio is MD
Must be 3 to 4 times in the direction, preferably 3.5 to 3.8 times. In the TD direction, it must be in the range of 8 to 12 times, and preferably in the range of 8.5 to 10.5. When the stretching ratio in the MD direction is less than 3 times or the stretching ratio in the TD direction is less than 8 times, the elongation percentage at a tensile strength of 5 kg / mm ² in the MD direction exceeds 150% and the tensile modulus is 80 kg / mm. Less than ² is not preferred. When the stretching ratio in the MD direction exceeds 4 times, or when the stretching ratio in the TD direction exceeds 12 times, MD
30% elongation at 5 kg / mm ² tensile strength
And the tensile modulus exceeds 130 kg / mm ^2, which is not preferable. [0013] The thickness of the biaxially oriented polyolefin film for use in the present invention is 15～120Myuemu, when considering the moldability, more preferably in the range of 20 to 50 m. The biaxially oriented polyolefin film used in the present invention may be a single-layer film or a laminated film having two or more layers. By using a laminated film, physical properties such as adhesiveness, heat sealability, and gas barrier properties can be imparted. In the case of forming a laminated film, the thickness of the film laminated on the biaxially oriented polyolefin film of the present invention is preferably 20% or less of the laminated film because the performance is not impaired. At this time, the resin to be laminated is not limited to polyolefin, and a known resin can be employed according to the physical properties to be imparted to the laminated film. For example, when imparting heat sealability, a resin that melts at a lower temperature than the polyolefin copolymer used in the present invention, for example, an ethylene content of 4 to 8% by weight and a melt index of 4 to 12 is used.
What is necessary is just to laminate the ethylene-propylene random copolymer for g / 10 minutes. Further, in order to impart gas barrier performance, an ethylene-vinyl alcohol copolymer, for example, "EVAL" (trade name, manufactured by Kuraray Co., Ltd.) is interposed on one side of the film by an adhesive resin by a coextrusion method or the like. They can also be stacked. In this case, the surface on which the ethylene-vinyl alcohol copolymer is laminated is preferably the outer surface, so as not to hinder the effects of the present invention. For the various resins used in the present invention, known additives such as antioxidants, crystal nucleating agents, heat stabilizers, release agents, slip agents, antiblocking agents and antistatic agents are used. Can be. As an anti-blocking agent, silica, natural zeolite, synthetic zeolite, kaolin, talc, silicone resin, silicone rubber, fused silica,
Fine particles such as melamine resin and acrylic resin are preferably used. These fine particles are preferably spherical, and more preferably a rubber-based fine particle which is softer than the polyolefin-based copolymer. As the slip agent, higher fatty acid amides can be used, but care must be taken because if added in a large amount, the film may be whitened and the transparency and gloss may be lost. When an appropriate amount of an antistatic agent is added, generation of static electricity can be suppressed. By performing the corona treatment, the effect can be further improved and printability can be imparted, and laminating processability such as when extruding lamination with a sheet (direct lamination) or dry lamination can be imparted.
When an appropriate amount of an antifogging agent is added, the polyolefin copolymer used in the present invention tends to exhibit an antifogging effect. The biaxially oriented polyolefin film used in the present invention is not particularly limited, but can be produced, for example, by the following method. First, a polyolefin-based copolymer is melted and kneaded by an extruder, and the melted resin is subjected to T
It is cooled and solidified into a sheet shape on a cooling roll by a mold die.
The obtained sheet is stretched 3 to 4 times after heating by a longitudinal stretching machine, and subsequently heated by a transverse stretching machine and then stretched 8 to 12 times in the width direction. After transverse stretching, at a temperature slightly higher than the stretching temperature, 5
It is preferable to relax by 15% since the heat shrinkage can be reduced. As the polypropylene sheet to be laminated with the above-mentioned biaxially oriented polyolefin film, known polypropylene sheets can be used without any limitation. Examples of the polypropylene include a propylene homopolymer, and a random, block, or graft copolymer of α-olefins other than propylene, for example, ethylene, butene-1, pentene-1 and the like of 20% by weight or less and propylene of 80% by weight or more. Or a mixture thereof. Further, as the polypropylene sheet, for example, a foamed sheet of polypropylene, a sheet containing fillers, a stretched sheet, and the like can be used. Known fillers such as talc, mica, calcium carbonate, magnesium carbonate, silica, and glass can be used as the filler. The amount of these fillers is not particularly limited, but is preferably in the range of 5 to 50% by weight for imparting heat resistance and improving mechanical strength of the laminated sheet. In addition, examples of the above-mentioned stretched sheet include a uniaxially stretched sheet, a biaxially stretched sheet, and a rolled sheet. The thickness of the polypropylene sheet is 0.2 to 1
mm, considering the formability , 0.3-0.5mm
More preferably, it is within the range. The method of laminating the biaxially stretched polyolefin film and the polypropylene sheet is not particularly limited, but known methods such as an extrusion lamination method and a dry lamination method are used. The laminated sheet for thermoforming of the present invention has almost no drawdown, good moldability and excellent surface gloss. Therefore , the laminated sheet for thermoforming of the present invention can be suitably used in the field of food packaging and general packaging. The present invention will be described in more detail with reference to the following Examples and Comparative Examples, which by no means limit the scope of the present invention. The physical properties of the films in the following Examples and Comparative Examples were measured by the following methods. (1) Tensile strength and elongation The sample was cut into strips having a width of 10 mm, and the measurement length was set to 40 mm.
Was recorded on a chart paper by a tensile tester at a tensile speed of 300 mm / min and a chart speed of 300 mm / min. An elongation rate of 5 kg / mm ² was read from the base point. (2) Tensile elastic modulus The sample was cut into strips having a width of 10 mm, and the measurement length was set to 20 mm.
The rising angle was recorded on a chart paper by a tensile tester at a pulling speed of 20 mm / min and a chart speed of 2000 mm / min. A perpendicular line was drawn at a point 20 mm from the base point, the strength at the intersection with the tangent was read, and the tensile modulus was calculated by the following equation. Tensile modulus (kg / mm ² ) = [strength (k
g) x sample length (mm) x chart speed (mm / min)]
[Pulling speed (mm / min) × 20 mm × Film thickness (mm) × Film width (mm)] (3) Hanging amount A far-infrared ray is sandwiched between the laminated sheet with the film face up on a clamp frame (300 mm × 300 mm). 30 heaters
The temperature was set at 0 ° C., and the laminated sheet was heated from above and below. The sheet once sagged, and the amount of sagging at the center of the sheet 5 seconds after the point at which the sheet sagged was measured. (4) Moldability Lunch container (length: 200 mm, width: 220 mm, height: 35 m)
m) is a partition part (width 2m) of the container when vacuum-formed
m, height 25 mm) was taken as 100%, and moldability was evaluated from the height of the partition part of the molded product under each condition. Example 1 Ethylene content 2.2% by weight, melt index 2.
0.2 parts by weight as an antioxidant (BHT), glycerin monostearate and N, N 'as antistatic agents were added to 100 parts by weight of an ethylene-propylene copolymer at 2 g / 10 min.
0.1 parts by weight of bis (2-hydroxyethyl) stearylamine, 0.01 part by weight of erucamide, 0.04 part by weight of calcium stearate, and an average particle diameter of 2 μm
Was added and melt-kneaded to obtain a raw material for a biaxially stretched film. This raw material was melt-extruded at 260 ° C. using a T-die extruder to form a 1.35 mm sheet on a 40 ° C. casting roll. This sheet was preheated with a heating roll at 125 ° C. and stretched 3.5 times in the machine direction. Next, the film was stretched 9 times in the transverse direction in a transverse stretching machine heated to 145 ° C., and then relaxed 7% in the transverse direction at 150 ° C. in the heat setting zone of the transverse stretching machine. The thickness of the obtained film was 40 μm. The strength, elongation, tensile modulus, and talc-containing polypropylene sheet of the film thus obtained (thickness: 0.45 m)
m, talc content: 30 wt%), the amount of sag, moldability, and surface gloss of the film surface of the molded product were measured. The results are shown in Table 1. Example 2 Ethylene content 1.3% by weight, butene-1 content 8.0
% By weight, 100 parts by weight of an ethylene-butene-1-propylene copolymer having a melt index of 5.0 g / 10 minutes,
Same as Example 1 except that the resin containing the same additives as in Example 1 was melt-extruded at 240 ° C. using the same T-die extruder and made into a 1.02 mm sheet on a 30 ° C. casting roll. Biaxial stretching was performed under the conditions. The thickness of the obtained film was 30 μm. The film thus obtained was laminated on the same polypropylene sheet as used in Example 1. The results are shown in Table 1. Example 3 Ethylene content 2.5% by weight, melt index 6.
A mixture prepared by blending 80 parts by weight of an ethylene-propylene copolymer with 0 g / 10 min and 20 parts by weight of a propylene homopolymer with a melt index of 2.0 g / 10 min with the same additives as in Example 1 was also subjected to T-die extrusion. Extrusion at 250 ° C. using a machine and 1.3 on a 35 ° C. casting roll.
Biaxial stretching was performed under the same conditions as in Example 1 except that the sheet had a size of 5 mm. The thickness of the obtained film is 40 μm
Met. The film thus obtained was laminated on the same polypropylene sheet as used in Example 1. The results are shown in Table 1. Example 4 Ethylene content 2.2% by weight, melt index 2.
70 parts by weight of an ethylene-propylene copolymer of 2 g / 10 min, ethylene content of 1.3 wt%, butene-1 content of 7.0 wt%, melt index of 5.0 g / 10 min of ethylene-butene-1- A mixture of 30 parts by weight of a propylene copolymer and the same additives as in Example 1 was mixed with T
Using a die-type extruder, the mixture was melt-extruded at 260 ° C., and biaxially stretched under the same conditions as in Example 1 except that a 1.35 mm sheet was formed on a casting roll at 40 ° C. The thickness of the obtained film was 40 μm. The film thus obtained was laminated on the same polypropylene sheet as used in Example 1. The results are shown in Table 1. Example 5 A film obtained in the same manner as in Example 1 was laminated on a transparent polypropylene sheet (thickness: 0.4 mm) by extrusion lamination, and the same measurement as in Example 1 was carried out. The results are shown in Table 1. Example 6 The procedure of Example 5 was repeated except that a foamed polypropylene sheet (thickness: 0.5 mm) was used.
It was shown to. Comparative Examples 1 and 2 Polypropylene sheet containing talc (thickness: 0.45 m)
m, talc content of 30 wt%), and the polypropylene sheet was molded while changing the surface temperature during molding as shown in Table 1, and the amount of sag, moldability, and surface gloss of the molded article were measured. The results are shown in Table 1. Comparative Example 3 The same additives as in Example 1 were added except that the antistatic agent was increased to 1.0 part by weight in 100 parts by weight of a propylene homopolymer having a melt index of 2.0 g / 10 minutes. It was melt-extruded at 280 ° C. using a T-die extruder, and biaxially stretched under the same conditions as in Example 1 except that a 1.35 mm sheet was formed on a casting roll at 35 ° C. However, since the obtained film has insufficient longitudinal stretching ratio, MD
The thickness in the direction was as large as 30 to 120 [mu] m, and the unstretched portion in the form of mottle was mixed with the dispersion, and a film which could be used practically could not be obtained. Comparative Examples 4 and 5 The same resin as in Comparative Example 3 was subjected to biaxial stretching in a longitudinal stretching ratio of 5
The same procedure was performed as in Example 1 except that the film was stretched to 00%. The thickness of the obtained film was 40 μm. The film thus obtained was laminated on the same polypropylene sheet as used in Example 1. The laminated sheet was molded while changing the surface temperature during molding as shown in Table 1, and the results are shown in Table 1. Comparative Example 6 Ethylene content 1.3% by weight, butene-1 content 7.0
100% by weight of an ethylene-butene-1-propylene copolymer having a melt index of 5.0 g / 10 minutes and the same additives as in Example 1 were mixed at 210 ° C. using a T-die extruder. It was melt-extruded and a non-stretched film of 40 μm was obtained on a casting roll at 30 ° C. The film thus obtained was laminated on the same polypropylene sheet as used in Example 1. The results are shown in Table 1. [Table 1]

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-60745 (JP, A) JP-A-2-299841 (JP, A) JP-A-3-288641 (JP, A) 27330 (JP, U) Actual opening 57-132528 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) B32B 1/00-35/00

Claims (1)

(1) An ethylene-propylene copolymer having an ethylene content of 1 to 4% by weight, or an ethylene content of 0.5 to 3.0% by weight and butene. -Consists of an ethylene-butene-propylene copolymer having a content of 4 to 15% by weight, a stretching ratio in the MD direction of 3 to 4 times, and a stretching ratio in the TD direction.
Biaxially stretched at 8 to 12 times, MD tensile strength 5kg
/ Mm ² is 30 to 150%, and MD
Thickness in which the tensile elastic modulus in the direction is 80 to 130 kg / mm ²
15 to 120 µm biaxially stretched polyolefin film
And (2) laminated sheet for thermoforming polypropylene sheet having a thickness 0.2~1mm is characterized by comprising stacked.