JPS58215345A - Composite film - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a composite film for packaging, in particular a laminate of a μ isotactic polybutene-1 homopolymer or copolymer and a propylene homopolymer or copolymer. The present invention relates to a composite film which is stretched at least in the m=axial direction and has poor properties required as a packaging film, particularly flexibility and bunch hole strength.

Packaging films are required to have many properties such as transparency, tensile strength, blocking resistance, flexibility, and bunch-hole strength, among which demands on flexibility and bunch-hole strength have recently become particularly severe. In other words, as the types of products and packaging formats become more diverse, "flexibility" becomes an essential requirement in order to adapt to all kinds of products and packaging formats. However, when transporting products over long distances,
"Bunch hole strength" is also extremely important in completely preventing film destruction during transportation. In particular, textile products such as clothing, bedding, interior products, etc. are soft products, so these products must be packaged in a soft manner, and are susceptible to holes due to external forces during handling and transportation. , it is necessary to prevent the progression of fracture starting from all the openings, which is extremely important for the above two types of characteristics.

Various types of synthetic resin films are known as packaging materials, including vinyl alcohol, polyphtadiene, ethylene-vinyl acetate, polyethylene, soft vinyl chloride resin, and vinylidene chloride resin. The most widely used material for packaging is soft polyvinyl alcohol. However, although polyvinyl alcohol films have excellent transparency, antistatic properties, and flexibility, they have serious problems in that they are sensitive to changes in humidity and lose flexibility and harden during dry periods. Moreover, because the film surface is sticky, it is difficult to work with during packaging, and it also causes blocking when stacking packaged products. Many problems have been pointed out.

The present inventors focused on the above circumstances and conducted research to provide a film with particularly excellent flexibility and punch hole strength.
It started. First, we focused on isotactic polybutene-1, which has high flexibility, and attempted to modify it for use in all packaging films. However, polybutene has a low softening point, is sticky on the surface, and has poor punch hole strength, so it cannot be put to practical use as a packaging film as described above.

It has been confirmed that divantihole strength of ordinary crystalline polymer films is improved by stretching. However, although isotactic polybutene-1 has some crystallinity, it cannot be subjected to a stretching process, so that stretching cannot be expected to improve the punch hole strength. So instead of completely improving the physical properties of isotactic polybutene-1, what is this? We thought that it would be possible to eliminate all of the above-mentioned drawbacks by combining the film with other film materials, so we conducted further research.

The present invention was completed as a result of such research, and
Its composition consists of a base layer made of isotactic polybutene-1 yarn homopolymer or copolymer having a butene content of 60 to 100% by weight, and a propylene base layer having a propylene content of 70 to 100% by weight on one or both sides of the base layer. The gist lies in that the base layer is made of a film made of a polymer or copolymer and has a thickness of 72 degrees, and the inner thickness of the base layer is 50% or more of the total inner thickness, and is stretched at least uniaxially. .

The base layer of the composite film according to the present invention must be an isotactic polybutene-1 homopolymer or copolymer, and the butene content i must be 60% by weight or more. The reason for this is that if the butene content is less than 60% by weight, the flexibility as a base layer becomes poor, the flexibility changes significantly due to temperature differences, and furthermore, the transparency of the film becomes poor. The most common copolymerization components are α-olefins copolymerizable with butene-1 (02 to C), but t, c
4h), and the form of copolymerization may be either a random copolymer or a block copolymer, but a random copolymer is optimal in terms of improving transparency. It is also possible to blend an α-olefin polymer into the material constituting the entire base layer within a range that satisfies the requirement that the butene content be 60% or more. This homopolymer or copolymer is laminated with the following propylene yarn alone or copolymer to form a composite film, but the thickness of the base layer must be at least 50% of the total internal thickness of the film. However, if the thickness of the base layer is less than 50%, the above-mentioned flexibility peculiar to the base layer will not be fully exhibited, making it impossible to achieve the entire purpose.

Next, the propylene thread alone or copolymer laminated on one or both sides of the base layer is extremely important in imparting stretchability to the composite film and mainly increasing the cross-hole strength Jl. In other words, it is extremely difficult to carry out the drawing process with the above-mentioned iK74'/J kuchitsukuboribute and no-1 yarn polymers. When a 10 pyrene thread polymer film is laminated on the composite film, the entire composite film can be stretched and the punch strength can be increased. Furthermore, since the surface of the composite film is coated with a non-sticky propylene polymer film and is in the fc state, the problem of blocking is also eliminated.

Propylene polymers suitable for such purposes include propylene homopolymers or propylene and a-olefins such as ethylene, butene, and hexene (preferably 02-
C. , except for C3) with a propylene content of at least 70! Is it more than L amount%? The reason for this is that if the propylene content is less than 70% by weight, the properties cannot be satisfied, and it cannot be laminated with an isotactic polybutene-1 polymer film that is difficult to stretch as in the present invention. This is because in this case, the stretchability of the composite film as a whole cannot be sufficiently improved. This propylene copolymer may be either a random copolymer or a Glock copolymer, but is it transparent? Random copolymers are optimal for increasing this. However, it is not superior to propylene homopolymer.

When selecting the above isotactic polybutene-1 polymer and propylene polymer, the most suitable one should be selected depending on the physical properties of the other material to be combined, but regarding the selection criteria. We also conducted a study and found that the most practical method is to determine the difference in melting points of the image materials, and that the melting point of the main polymer that forms the entire base layer is lower than the melting point of the surface layer by 5 to 50°C. It was found that a high-quality composite film could be obtained by selecting all materials.

The above composite film can be manufactured, for example, by the following method.

[1] The base layer and the coating layer are individually melt-extruded and then melt-laminated, or the base layer is melt-extruded in a full bath and laminated on a previously prepared coating film, and then cooled and solidified. The cooling solidification temperature in this case depends on the melting point of the material, but is between -20 and
The temperature is generally about 100°C (preferably Vf, -20 to 70°C). Taking over again or tension? When applying, it is preferable to arrange all the rolls so that the coating layer is in contact with the chill roll and the base layer is in contact with the hot roll.

Of course, when coating Mk is provided on both sides, such consideration is not necessary at all.

[2] The unstretched composite film obtained above is then subjected to a VC stretching treatment in at least the l-axis direction (or in the biaxial direction of a suitable film) by a conventional method. The stretching ratio is not particularly limited, but in order to significantly exhibit the effect of increasing bunch hole strength, it is recommended that the stretching ratio be approximately 1.5 to 20 times in the longitudinal direction and 1.5 to 16 times in the transverse direction. In this case, the optimum stretching temperature of 1M degree is 80 to 160°C (preferably 60 to 185°C) for longitudinal stretching.
°C), 60 to 160 °C (more preferably 80 to 140 °C) in the case of transverse stretching. This composite film is only uniaxially stretched (generally 2-20°C at 60-160°C).
However, full biaxial stretching will further improve the bunch hole strength, as well as creep properties, transparency, anti-blocking properties, and antistatic properties. is preferred.

The stretched film obtained in this way may be rolled up as it is and made into a single product, or if necessary, it may be subjected to aging treatment at about 10 to 60°C, and further subjected to corona discharge treatment, electron beam treatment, flame treatment, etc. You can also do it.

The present invention is roughly constructed as described above, and includes a propylene polymer on one or both sides of an isotactic polybutene-1 polymer film with excellent flexibility. By laminating and stretching the film, it was possible to significantly improve the characteristics required for a packaging film, especially flexibility and bunch hole strength. Therefore, this composite film is extremely useful for packaging soft products such as textile products, and can also be used for packaging other thermoplastic films, cellophane, paper, cloth, etc.
By fully laminating metal foils, etc., it can be applied to applications depending on the characteristics of each.

Next, Examples and Comparative Examples will be shown, but prior to that, all evaluation methods for various test items to be described later will be explained.

(20℃ using all Perkin-Elmer differential calorimeters)
It was measured at a temperature increase of 1 minute.

(2) Blocking Measured according to AsrM-D-1893-67, heating temperature was 50'C.

(3) Friction coefficient Measured according to ASTM-D-1894-63 method.

(4) Haze Measured according to ASTM-D-1008-52.

(5) Gross Measured according to ASTM-D-528-67.

(69 Surface unevenness and ripple pattern Rating: 5: Not at all, good condition. 4: Slight presence, but no practical problem. 8: Slight presence, but no unevenness and usable. 2: Quite noticeable pattern. Unsuitable for use 1: There are unevenness and ripples that stand out from each other on the entire surface, making it completely impossible to use. Measured by breaking strength when

Example 1 Isotactic polybutene-1-ethylene copolymer (
Ethylene content: 80% by weight), 10% by weight of propylene-butene-1 copolymer, and 10% by weight of globylene-ethylene copolymer were added with ethylene, an alkylamine, as an antistatic agent. An amount of 96% of the oxide adduct IN was mixed to obtain a base layer film material (A). In addition, as the film material (B) for the coating layer, propylene-butene-1 copolymer (butene content 12% by weight) is used.
) and propylene-ethylene copolymer (ethylene content 4
．． 5 wt.

After melt-extruding each of the above materials (A) and (B), they are laminated in a molten state and then cooled with a cooling roll at 25°C.B)
The thickness ratio of layer/(A) layer/(B) layer is 15/75/15
(total thickness is 40 μm)
m).

On the other hand, an unstretched film was obtained in the same manner as above except that materials (A) and CB) were melt-extruded so that the wall thickness in the unstretched state was 720 μm, and then rolled in the longitudinal direction at 125° C.
．． A biaxially stretched film with a wall thickness of about 40 μm that is simultaneously biaxially stretched 0x and 4-5x in the lateral direction? Obtained.

One side of the unstretched or 211i stretched film obtained above was subjected to corona discharge treatment to adjust the surface wetting tension to 41 dynes/α, and then subjected to the physical property tests shown in Table 1 below.

Comparative Example 1 Isotactic polypropylene 1'tx Example 1,
! : 1.0% by weight of the same antistatic agent was mixed and then melt-extruded, and the same procedure as in Example 1 was carried out to prepare an unstretched film and a biaxially stretched film with a thickness of 40 μm. The surface wetting tension was adjusted to a total of 40 dynes/α by applying the same corona discharge treatment.

Comparative Example 2 Low density polyethylene (density 0-
An unstretched film and a biaxially stretched film with a surface wetting tension of 40 dynes/α were prepared in the same manner as in Comparative Example 1 except that 915 f/ax) was used. Obtained.

Comparative Example 3 The same isotactic polypropylene (containing 1.0% by weight of antistatic agent) used in Comparative Example 1 was used as the film material for the base layer, and propylene-ethylene copolymer (ethylene content: 4.0% by weight) was used as the film material for the base layer. An unstretched film and a 2h stretched film with a surface wetting tension of 40 dynes/α and a thickness of 40 μm were prepared in the same manner as in Example 1, except that they were used as film materials for the coating layer. Obtained.

Comparative Example 4 Polybutene-1 mixed with 1.0% by weight of an antistatic agent was used as the film material for the base layer, and the low-pressure polyethylene used in Comparative Example 2 was used. The same procedure as in Example 1 was used except that the film for the coating layer was used as the purple material, and the surface wetting tension was 40 dynes/ax''.
'C unstretched film and biaxially stretched film with a thickness of 40 pm? Obtained.

Comparative Example 5 The same isotactic polybutene-1 used in Example 1 was melt-extruded alone to obtain an unstretched sheet with a thickness of 720 μm. In this case, it was extremely difficult to form a film because the extruded sheet adhered to the chill roll, but it was melt-extruded at a low speed of about 0.5 m/min, completely ignoring productivity and appearance. I did it.

This unstretched sheet was biaxially stretched in the same manner as Tenjiri Example 1,
A film with a thickness of 40 μm was obtained. However, since it was not possible to carry out stretching at 125°C, the stretching temperature was set at ffU10.
The temperature was set to 0°C. Then, one side was subjected to corona discharge treatment to adjust the surface wetting tension to 41 dynes/α.

The properties of each unstretched film and biaxially stretched film obtained in the Tenjiri Example and Comparative Example are summarized in Table 1.

As is clear from Table 1, the biaxially stretched film of Example 1 (the film of the present invention) is different from the unstretched film of Example 1 and the unstretched or biaxially stretched films of Comparative Examples 1 to 5 (both It also has superior punch hole strength compared to other comparative films. In addition, the film of the present invention shows comprehensively superior values in other properties compared to comparative films, and in particular, Young's modulus, which is a measure of flexibility, is inferior to a single film of isotactic polybutene-1. In addition, the blocking and friction coefficient values are comparable to those of a polypropylene film alone. That is, it can be said that the composite film of the present invention has both the features of isotactic polybutene-1 and the features of polypropylene, and has significantly improved bunch hole strength.

Applicant: Toyobo Co., Ltd.

Claims (1)

[Claims] (1) One side or both sides of a base layer made of isotactic polybutene-1 yarn homopolymer or copolymer with a butene content of 60 to 100% by weight, and a propylene content of 70% by weight.
-100% by weight of a propylene homopolymer or copolymer film, and the base layer has a thickness of 50% or more of the total thickness and is stretched in at least one axis. Composite film with all the features.