JPS6341550A - Resin composition for molding film - Google Patents

Abstract

PURPOSE:To obtain the title composition, by blending a specific ethylenic copoly mer with an ultralow-density polyethylene and crystalline polyolefin in a specific proportion, having remarkably improved conflicting properties of ready stretching and difficult breaking as well as good finish packaging. CONSTITUTION:A composition obtained by blending (A) a polymer selected from low-density polyethylene, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, ethylene-acrylic acid copolymer and ionomer resins, (B) an ultralow-density polyethylene having <=0.91g/cm<3> density, >=110 deg.C melting point and 100-1,000kg/cm<3> 1% modulus and (C) either one of crystalline polypropylene and crystalline polybutene-1 or a blend thereof to give the following ratios. 0.90>=B/(A+B)>=0.30 and 0.50>=C/(A+B)>=0.05.

Description

[Detailed description of the invention] [Industrial application field] The present invention has excellent extrusion moldability and stretchability, and
The present invention relates to a composition capable of producing a polyolefin film having many excellent properties such as heat sealability, impact strength properties, tensile strength properties, flexibility, cold resistance, and transparency.

This composition is useful as a constituent of the main resin layer of a composite film, and such a composite film is suitable as a stretch film for food packaging.

[Conventional technology]

Plasticized polyvinyl chloride (hereinafter abbreviated as PvC) film is mainly used as stretch film for food packaging, but there are hygienic problems such as the transfer of plasticizer into food, and the generation of toxic gas when incinerated. There are pollution problems such as Therefore, as an alternative to PvC film, ethylene-vinyl acetate copolymer (hereinafter abbreviated as EVA) is used.
There are several films on the market, but the ability to replace PvC film has not yet reached its potential. In other words, if you increase the vinyl acetate content to make the EvA film easier to stretch, it will become weaker and more likely to tear, and to prevent this, if you increase the film thickness from /lμ to 0μ to 25μ, the elongation will become ic<. . In addition, when the vinyl acetate content is increased, the film exhibits elastic behavior similar to rubber, and the adhesion and sealing between the films becomes weaker, and the increased thickness is also disadvantageous in terms of cost.

An example of a composition suitable for a stretch film that solves these contradictory problems is EVA.

Japanese Patent Publication No. Sho 39-319 disclosing a ternary composition of ethylene-α-olefin copolymer nidistomer 1 polypropylene
No. 76, and as a film, JP-A-Shoto-O-
There is an invention disclosed in Publication No. 79932. This film had extremely high heat resistance, heat sealability, and stretchability compared to conventional olefin stretch films.

[Problem that the invention seeks to solve]

In recent years, mechanization and diversification have progressed in the field of stretch packaging. The mainstream of packaging is shifting from traditional hand packaging using hand wrappers to machine packaging, which can save labor and increase speed. In addition, in the past, mechanical packaging used to involve packaging specific items in large quantities after making sufficient machine adjustments (e.g., stretch rate), but in recent years, a wide variety of materials and shapes have been used. The method has changed to packaging trays in small quantities at random, with little mechanical adjustment. In addition, machines are now used to package items that have protrusions that can easily tear the film (crab scissors, frozen fish, etc.), and stretch films are now required to have such versatility. It has become.

Conventional compositions disclosed in Japanese Patent Publication No. 39-3T97A etc. have sufficient versatility even when formed into a film, and cannot be applied to random packaging of trays made of a wide variety of materials and shapes. There were some points, and it was impossible to package special items. In addition, when this composition is used as a main component, there is a problem in that if the physical properties of the film are attempted to be improved by changing conditions such as stretching and deorientation, thickness unevenness worsens and film formability deteriorates.

As a result of intensive research to improve the mechanical packaging suitability and versatility of stretch packaging, the present inventor discovered that low-density polyethylene or specific ethylene copolymers It was discovered that a ternary composition consisting of a specific blending ratio of three components, ultra-low density polyethylene and crystalline polyolefin, has excellent cold stretchability, and the formed film has the contradictory properties of being easy to stretch and difficult to tear. properties are significantly improved,
The present invention was developed based on the discovery that the packaging property is excellent in versatility and has a beautiful finish.

In other words, the present invention provides at least one material selected from the group consisting of (A) low density polyethylene, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, ethylene-acrylic acid copolymer, and ionomer resin. 7 types of polymers, (B) ultra-low density polyethylene with a density of Q9/li/- or less, a melting point of 11O"C or more, and a 7% modulus of 100~/000We-rl-, (C) crystalline polypropylene, Any of crystalline polybutene-7 or a mixture thereof, (2), a resin mixture of (Bl and (C)),
The mixing weight ratio of (A), (8), and (C') is 0.90≧B
/(A+B)≧a, io.

The present invention relates to a film-molding resin composition in which aSO≧C/(A+B)≧O, OS.

The present invention will be described in detail below using the drawings and the like.

FIG. 1 is a conceptual diagram showing an example of a process suitable for producing a film mainly composed of the composition of the present invention. This process will be explained in detail according to FIG.

Prepare three extruders: (1), (1'), (1'1),
Seven of them were supplied with the composition of the present invention as a base layer.
In the other machine, the resin for the heat-resistant layer (H layer) and the resin for the skin layer (8 layers) are arranged, and they are combined by the annular die (2) and extruded into a tube shape. At this time, in the die (2), multiple layers such as S layer/paste layer/H layer/S layer, S layer/base N/H layer/base layer/S layer are stacked, and the extruded tube is placed in a water-cooled ring. (3) and then 7 pairs of pinch rolls (
The original fabric is obtained by folding according to A). The raw fabric is passed between a pair of pinch rolls (5) and (A) by introducing air inside and twisting to disperse uneven thickness, and then sent to a stretching machine. And heating ring (8)
, the stretching humidity (
The process is heated to the temperature at which the bubble begins to stretch, and is expanded by the internal pressure of air to form a bubble, nearing (9), <i>
The film is cooled to about -0°C from K, subjected to cold stretching, folded with a deflator, and taken off with pinch rolls aυ to obtain a film. This is heated and shrunk with hot air by a heat setting device (river), and is divided into a single film and wound up in a winding machine (b) to obtain a product.

Conventionally, in the cold stretching process shown in Figure 1, when stretching is carried out at a heating temperature of SO''C or lower, the stress of the film is high and the flexibility is insufficient. The process shown in Figure 2 was generally unstable for stretching at heating humidity of 60° C. or higher.

Next, the range of the resin composition of the present invention will be explained with reference to FIG.

Figure 1 shows Na/~/4 of Examples/and Comparative Examples/ shown later.
It is an experimental analysis diagram corresponding to C.

In the figure, the components are low density polyethylene, EVAN x tyrene-ethyl acrylate copolymer, ethylene-acrylic copolymer, ionomer resin, or a mixture thereof. Low-density polyethylene has a melt index of C or below (abbreviated as MI) a Col 10. Density Q9/-(
19J 9/aA. Ethylene copolymers contain monomers other than ethylene in an amount of 1 to 1 molar, MI (l
λ~1o. Among these, low-density polyethylene and EVA produced by a high-pressure method are preferred.

The ultra-low density polyethylene of component (B) is described in Plastic Engineering Volume 1/P, J Ribuco (lrj
)), which contains ethylene and 3 carbon atoms.
It is a copolymer with ~1 α-olefin.

Crystalline polypropylene with crystalline polybutene (O) is a crystalline polymer with high isotacticity. It is a product of MI (l N2Q).Polybutene is a low molecular weight liquid, waxy type, and fruit butene-
It has a high molecular weight content of 93 mol% or more and also contains copolymers with other monomers.

To explain the coordinate system in Figure 1, vertices A, B, and C indicate that each component is 100%, and on side AB, component (C) is 0%, and components (A) and (B ) is the ratio of apex AK
The closer you get, the more prisoners there are.

Further, a line parallel to side AB indicates that as it approaches vertex C, component (C) increases by 70%, 20%, and 30%. For example, point A (J41.291.!i) has component ■47% by weight, component (n) x 9% by weight, and component (C) 3
Shows the weight percentage of the stone.

The symbols ◎, 01△, and × in the figure are (A), (
Characteristic values brought about by the three-component composition of B) and (C), namely, the fluctuation of the folded width of the original film indicating the film formability, the average bubble life, the stable temperature range, the uneven thickness of the film, and the necessary characteristics as a stretch film. shows. Haze, falling impact strength, 1
The results of a comprehensive evaluation of a total of seven properties of 00% elongation stress are plotted on a coordinate system along with the ratio of each component (B) and (C). The areas where the overall evaluation is ◎, ○ are points A (6, 29, ri, points 0 (10, I#, ri, points/S (7,
tO,! It is in the range surrounded by point 2 (37, 20, 33), and points with comprehensive evaluations Δ and × are arranged around it. It has been found through analysis that the area surrounded by the dots, ie, the claims, provides a composition useful as a stretch film.

Table 3 listed below shows the composition of the present invention and the conventional Japanese Patent Publication No. 1973-
A comparison of the compositions of No. 31976 is shown in terms of the film forming conditions of the compositions and the properties under those conditions. According to Table 3, the composition of the present invention is extremely stable in the cold stretching process shown in FIG. 2 in a temperature range that cannot be achieved with conventional compositions. As a result, the film obtained from one composition satisfies all of the requirements of dimensional stability, uneven thickness, and flexibility, which was impossible to simultaneously add 1cII by cold stretching with the conventional composition. Ta.

Table Q shows the film's suitability for mechanical packaging and its versatility. According to Table 1, the film obtained from this composition is well suited for packaging special contents that tend to be problematic in the actual market, as well as for tray packaging of a wide variety of materials and shapes. It shows superior packaging finish and versatility. This indicates the high practicality of the film used with this composition.

〔Example〕

The present invention will be explained in detail by giving examples below.

Note that measurements and evaluations in the examples were carried out by the following methods.

(Evaluation method) /) Folding width variation of original fabric The folding width of the original fabric was measured continuously over 2Q11, and the difference between the maximum and minimum R (m) was divided by the average folding width and multiplied by 100.

◎ Less than 7% ○ tI% or more but less than 7% Δ 7% or more and less than 10%

◎ 1 hour or more 1 hour or more Less than 2 hours △ 30 minutes or more Less than 1 hour × Less than 30 minutes 3) Stable stretching temperature range A stretching temperature range that allows stable stretching. A film forming test was conducted, and conditions were defined as a stable stretching temperature that had a bubble life of 30 minutes or more and had no bubble fluctuation.

◎ Greater than 0℃ ○ Greater than 10'C and less than 20'C Δ Greater than 3℃ and less than 10'C When this was repeated three times in the machine direction, the thickness from the average thickness was expressed as ±X%.

◎ 3% or less ○ More than 3% and less than io% Δ Greater than 10% and less than 20% X greater than 20% j) Haze value Measured according to ASTM-D-10 (:) J-sco.

◎ /, 0% or less 0 /, greater than 0% and less than 2% Δ Greater than 20% and less than 3% It was used as a measure of strength against. ASTM
-D-/Measured according to method 709-47.

◎ 3QKgcm or more ○ j OKg cm or more 30K Tantan △ / OK
y am or more, less than 20 Kgcm x less than 10 Kgcm 7) ioo% elongation Used as a measure of ease of stretching and flexibility of the stress film. A
A tensile test was conducted according to the STM-D-112-t7 method, and the stress at 100% elongation (VI.

■Width), expressed as the average value of vertical and horizontal values.

◎ JI10tm width or less 0 -2009/Large than 10mm2!Og/1(Ha
s width or less △, 2jOg/1O1a1 width greater than 300
g/lo ■ Width or less
Evaluation was made based on the total score, with × as 0 points.

◎　　　　/On point r Upper/G point or higher, 77 points or lower Δ 10 points or more 13 points or less × 9 points or less A list of resins used in the examples is shown below.

ml: EV A (vinyl acetate content j, j mo # %, MI/, o) ILz: EVA (vinyl acetate content!, j morch, M engineering/, 0) a3: low density polyethylene (LDPE) (Ml, 2.O, density aqir/al
, m, p, / (7, r℃] a4: ethylene-
Ethyl acrylate copolymer (EEA) [ethyl acrylate content S, O mol%, MI/, t) as; ionomer resin (IO) (ethylene-methacrylic acid copolymer N
a Neutralized type, methacrylic acid content 7.4 mol%, MI
/, (7, degree of neutralization !%, degree of saponification! 0%) b1: Ultra low density polyethylene (ULDPE) (density arq9/al
, MI Qlr, Union Carbide Knee Car Flex DEFD-tx/ONT) b, i UI, DPE (Density Q90/cl!, M
Ia+, Unio Y'Carbide Nycarflex I)FDA-/131NT)el'Crystalline polypropylene (IPP) (weight S random copolymerization of ethylene, MFR7,0,m,p,//7 °C]
c2: Crystalline polybutene (PB-/)C butene-/content 9g molti, density o, qosr/cJ, MI/, 0) a
s: I PP (MFR2,,2, density aqig
t〆1, m, p, /l'l'' (, 1 Example/and Comparative Example 1 Ethylene-vinyl acetate copolymer (EVA) (ILI)
20% by weight, ultra low density polyethylene (ULDPE)
(bt) 4 layer weight% and crystalline polypropylene (IPP
)(Cx)/j% by weight was mixed and prepared as a paste. In addition, 0% by weight of the next K IPP (Ct) I and 20% by weight of crystalline, i' IJ butene (PB/) (e2) were mixed as the H layer agent, EVA (a2) was used as the 8 layer agent, and the first It was stretched and formed into a film using the process shown in the figure.

At this time, diglycerin monooleate, polyoxyethylene nonyl phenyl ether, and mineral oil were added to the extruder for the base layer as additives. ! r*
-Flk Chi, /, 3 wt%, /, 0 wt% total weight%
was injected and kneaded.

In addition, the thickness of the original fabric is 8 layers for the 1st layer and 5th layer, and 7 layers each.
μ, the second layer, and the μ-th layer are the base layers, respectively.
The thickness of the H layer was 7μ, and the total thickness of the J layer was 70μ.

At a stretching temperature of 70°C, the length is 2.2 to 2.11 times, and the width is 3. Il~3. Stretch it twice and heat set Nω
) was blown with hot air at 3o''C to shrink the film by j% vertically and j% horizontally, and then a film was obtained.

Let this be Nll/. Also, prisoners as shown in Table 1 (
B) and (C) Films were obtained by the process shown in FIG. 2 in the same manner as N11/, using base layer compositions in which the types and ratios of the polymers of each component were changed.

Table 2 shows Example/(NIL/~r) and Comparative Example/(m
The stretching properties and physical properties of Samples 9 to z&) were evaluated by the methods of c to r) above, and the results are shown below.

Based on Table 2 below, the roles of each component (A), (B), and (Q) are considered as follows.

Component (A) improves extrudability, transparency, etc., and as is clear from the comparison of bulk 7 and concealment/no, when the ratio with component (B) is 70% by weight or less, draw resonance Resonance) phenomenon occurs, and the fold width fluctuation of the original fabric deteriorates rapidly, making subsequent stretching impossible.

Component (B) has improved impact strength, flexibility, and transparency, and has the function of improving the compatibility of components (A) and (C) and enhancing the synergistic effect. If component (B) is present in a small amount, transparency will be significantly lowered due to decreased compatibility, and impact strength and flexibility will also be lowered, as can be seen from the comparison of hr and /μ.

Ingredient (C) improves the firmness and bubble stability of the film, and as is clear from 10, when the film is slightly thinner, the 1-bubble stability decreases and punctures are more likely to occur, resulting in uneven thickness. Only bad films can be obtained.On the other hand, component (q
If there are too many, the flexibility of the film decreases as is clear from Nαλ and H1l/, 2, resulting in a film that cannot be used as a stretch film.

(Left below) -/r- Comparative Example - As a paste layer composition, 3% by weight of EVA (at), ethylene-α-olefin copolymer thermoplastic silasmer [15% by mole of α-olefin in propylene, Monote, M copolymerized with 3% by weight of ethylidene norbornene
I (lIl&, Vicat softening point IIo℃ or less) (b3
) 20% by weight, IPP(et) 13% by weight, PB-/
(es) 3% by weight was mixed to prepare a base layer composition, and an extruded original fabric was obtained in the same manner as in Example.

Cholera stretching temperature 1. tt”c is 2.3 times vertical and 3 times horizontal.
Stretched to 3 times, length S%, width 3 using heat setting device
% shrinkage was designated as A. 1. Stretching mix us ”
After stretching in the same manner as in C, B was shrunk by 70% in the vertical direction and 70% in the horizontal direction. Furthermore, C
And so.

Table 3 shows the results of the physical properties and stretching conditions of various films, together with the results of Example 1.

According to Table 3, Example 1f) Nnl had low film stress, excellent thickness unevenness, and service life of 3 hours or more, which was extremely excellent at 1+2/-, and was satisfactory.

For A, the thickness unevenness and bubble life of the film were fair, but due to the high stress of the film and the high heat shrinkage rate of the film at In particular, width shrinkage occurred and the product was unsatisfactory as a commercial product.

In order to compensate for the drawbacks of Comparative Example/B, the film is greatly shrunk in a heat setting device to reduce film stress and μO.
℃ The heat shrinkage rate has been lowered. However, it has the disadvantage that the uneven thickness of one film decreases due to excessive shrinkage during heat setting. Furthermore, if the thickness of the product is kept constant, the film thickness of the bubble during stretching becomes extremely thin due to the large amount of subsequent shrinkage, resulting in a reduction in the life of the bubble.

C. An attempt was made to form a film under the same conditions as in Example 1, but because the stability of the bubbles was extremely poor, only a few film fragments with poor thickness unevenness were obtained.

Thus, the Na/film of Example 1 could not be compared with Comparative Example A, BSC. It satisfied all of the requirements of dimensional stability, uneven thickness, flexibility, and stable film formability.

Table 3 Mechanical Packaging Test Examples Example/NIl/, Nap and Comparative Example λ B1 Commercially available p
Table 1 shows the results of mechanical packaging tests performed on stretch films of vcJ and U EVAi.

The packaging machine was a linear type 5T-6090 manufactured by Omori Machine Industry Co., Ltd. As test 1, a standard tray made of foamed polystyrene was filled with clay simulating the contents. As Testco, we packaged clay in deep trays made of high-impact polystyrene that are easy to crush. As Test 3, clay was placed and packaged in a large tray made of biaxially oriented polystyrene, where the film tends to tear at the tray edge. As test g, clay was placed in a long tray for packaging saury that tends to leave wrinkles on the finished product. test! The content of crab claws with protrusions was packaged in a tray similar to Test/. In addition, the packaging machine was adjusted by adjusting the tension of each film, such as the stretch rate, in Test 1, and Tests 2 and 3 were conducted under the same conditions.

The evaluation is as follows: ◎ Items that were packaged well in all cases 〇 Items with some small wrinkles or distortions △ Items with wrinkles, tears, or uneven treads Comprehensive evaluation was made with Δ as 7 points and x as 0 points.

As is clear from Table μ, NIl/, hidden g of Example 1
Compared to Comparative Example B, the mixing properties of the packaging were significantly improved, and the performance was equivalent to or better than that of commercially available PvC films. Compared to other films, commercially available EVA films were easily torn and the overall evaluation of the packaging was at an extremely low level. In addition, for contents that are extremely difficult to package in a machine such as test j, k l of Example 1, NCL
& had excellent packaging properties.

(Left below) -2- [Effects of the Invention] As stated above, the composition of the present invention has excellent extrudability and stretchability, as well as excellent flexibility, impact strength properties,
This is a composition that allows you to obtain a film with good tensile strength and transparency. In addition, a film with such a composition is
It has the effect of meeting the mechanical packaging properties required for stretch films, and plays a major role in industry.

[Brief explanation of drawings]

FIG. 1 is a triangular diagram showing the -g- range of the three-component composition of the resin composition of the present invention. FIG. 2 is a conceptual diagram showing an example of a process suitable for producing a composite film mainly composed of the composition of the present invention. Patent applicant Asahi Kasei Industries Co., Ltd. Representative Patent Attorney Hoshino -Toichi 7-

Claims (1)

[Claims] (1) A mixed resin of the following (A), (B), and (C),
A resin composition for film molding whose mixing weight ratio is 0.90≧B/(A+B)≧0.30 and 0.50≧C/(A+B)≧0.05. (A) At least one polymer selected from the group consisting of low density polyethylene, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, ethylene-acrylic acid copolymer, and ionomer resin. (B) Ultra-low density polyethylene with a density of 0.91 g/cm^2 or less, a melting point of 110°C or more, and a 1% modulus of 100 to 1000 Kg/cm^2. (C) Crystalline polypropylene, crystalline polybutene-1, or a mixture thereof.