JPH0473127A - Heat-shrinkable film-shaped material and its manufacture - Google Patents

Abstract

PURPOSE:To increase adhesion properties to a base and transparency by specifying the temperature difference between an upper roll and a lower roll of a couple of pressure rollers, rolling thermoplastic resin and manufacturing a film-shaped material with specified overall light transmittance, haze and shrinkage factor. CONSTITUTION:Thermoplastic resin is melted and kneaded, and a film is manufactured by the forming method such as the T-die method and the inflation method. Rolling is performed between a couple of rolls or more at the temperature of 10 deg.C lower than the melting point of crystalline thermoplastic resin, and the temperature difference between an upper roll and a lower roll is usually 10 deg.C or over. Thus a film-shaped material having 90% or more overall light transmittance and 5% or less haze, preferably 92% or more overall light transmittance and 3% or less haze, and 10% or more shrinkage factor when heat treatment is carried out at the temperature of 5 deg.C lower than the crystalline melting point is manufactured. The film-shaped material is provided with the tendency of winding on the transverse axis after shrinking.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a heat-shrinkable film-like product made of thermoplastic resin, and particularly to adhesiveness to a packaged object (hereinafter sometimes referred to as "substrate") after heat-shrinking. The present invention relates to a highly transparent film-like product with excellent properties and a method for producing the same.

[Prior Art] There are two types of shrink films made of plastic: foamed and non-foamed. Vinyl chloride resin is mainly used as shrink film for containers and packaging. However, due to environmental problems caused by the generation of chlorine gas during incineration, attempts have been made to switch to packaging films using polystyrene resin or polyolefin resin.

[Problems to be Solved by the Invention] The present invention relates to a thermoplastic resin film having physical properties suitable as a non-foaming heat-shrinkable film.

Conventionally, polystyrene resin has been widely used as a substitute for vinyl chloride resin due to its transparency and shrinkage rate.However, it lacks solvent resistance and deteriorates in adhesion to the substrate over time. (relaxation phenomenon).In addition, polyolefin resins have better heat resistance than the above resins, so they are used for retort applications.However, polyolefin resins have insufficient transparency and shrinkage rates. Its use is limited due to its small size and large relaxation phenomenon.

The inventors of the present invention have conducted extensive research on methods for obtaining a heat-shrinkable film-like material that suppresses the relaxation phenomenon to a small extent, has little impact on the environment, and has excellent transparency.

[Means for Solving the Problem] As a result, the present inventors developed a thermoplastic resin film obtained by rolling a pair of rolling rolls with a temperature difference of 10°C or more between the upper roll and the lower roll. It was discovered that the relaxation phenomenon after heat shrinkage can be improved by showing a tendency to wrap around the horizontal axis during heat shrinkage, and a film-like product with excellent transparency can be obtained.Based on this knowledge, the present invention was developed. completed.

As is clear from the above description, an object of the present invention is to provide a heat-shrinkable thermoplastic resin film that has good adhesion to a substrate and excellent transparency. It is in.

That is, the present invention provides (1) a total light transmittance of 90% or more and a haze value of 5% or less;
When heat-shrinked at a temperature 5°C lower than the crystal melting point, the shrinkage rate in the longitudinal direction (molding direction) is 10% or more, and the film-like material after shrinkage shows a tendency to wrap around the horizontal axis. (2) When a thermoplastic resin is rolled between one or more pairs of rolls, the temperature difference between the upper roll and the lower roll in contact with the resin is small (both are 10°C). A method for producing a heat-shrinkable film-like material, comprising:

Examples of thermoplastic resins used in the present invention include the following: high-density polyethylene, medium-density polyethylene, low-density polyethylene, linear low-density polyethylene, crystalline polypropylene, crystalline poly-1-butene. , crystalline olefin homopolymers or copolymers such as crystalline poly-4-methyl-1-pentene, nylon-6, nylon-6,6, nylon-12, nylon-6,10, nylon-11, etc. Crystalline polyamide resins, crystalline thermoplastic polyester resins such as polyethylene terephthalate and polybutylene ethylene phthalate, polyacetal resins, acrylonitrile-butadiene-
Examples include low crystallinity or amorphous resins such as styrene copolymer resins and polystyrene resins, and mixtures of two or more of these thermoplastic resins, but are not limited to these thermoplastic resins.

Among the above-mentioned thermoplastic resins, crystalline olefin polymers are preferred from a practical standpoint.

Among the crystalline olefin polymers, preferred are, for example, the following: Homopolymers include high-density polyethylene, crystalline polypropylene, crystalline poly-1-butene, and crystalline poly-4- Copolymers such as methyl-1-pentene include medium density polyethylene, linear low density polyethylene, and crystalline propylene copolymers, such as: propylene containing 70% by weight or more of a propylene component, ethylene, 1-butene, -hexene, 1-heptene,
Crystalline copolymers of 1-octene or 1-decene with one or more α-olefins, propylene or the above-mentioned α-olefins with vinyl acetate, acrylic acid, methyl acrylate, ethyl acrylate, acrylic crystalline polyolefin resins such as copolymers with polar monomers such as butyl methacrylate, methyl methacrylate, ethyl methacrylate or butyl methacrylate; Modified resins that are copolymerized or grafted with unsaturated carboxylic acids such as acids, their acid anhydrides, or derivatives such as their esters, and modified resins that are treated with ionizing radiation or crosslinked with a crosslinking agent can also be used. It can be suitably used depending on the situation.

In the present invention, various fillers (or reinforcing materials) can be added to the thermoplastic resin to the extent that the transparency thereof is not substantially reduced.

Examples of fillers that can be used include fibrous fillers such as glass fibers, carbon fibers, and vinylon fibers, mica, flake fillers such as talc, spherical fillers such as glass peas, and amorphous fillers such as calcium carbonate and wood chips.

The surface of these fillers (or reinforcing materials) is preferably subjected to a treatment that imparts affinity to the resin to be blended. Examples of such treatments include addition of unsaturated carboxylic acids or their acid anhydrides, addition of unsaturated amines, and rubber coating.

In addition to these fillers, extenders, colorants, flame retardants, deterioration inhibitors, antistatic agents, lubricants, etc. can be added.

In the present invention, the thermoplastic resin is melt-kneaded and formed into a film by a known forming method such as the T-die method or the inflation method, and the resulting film-like product for rolling (hereinafter referred to as "original film")
rolling process is performed on the

The rolling in the present invention can be carried out between one or more pairs of rolls at a temperature that is 10°C lower than the melting point of the crystalline thermoplastic resin (or its softening point in the case of low-crystalline or non-crystalline resins). is necessary. If the raw fabric is rolled at a temperature that is higher than the melting point of the thermoplastic resin (its softening point in the case of low crystalline or non-crystalline resin) or higher than the temperature that is 7°C lower, the raw fabric will There are problems such as wrinkles and uneven thickness due to close contact with the roll.

The effect of the rolling treatment in the present invention is noticeable in resins with high crystallinity. However, even an effect that appears in low-crystalline or non-quality resins may be sufficient depending on the application. The rolling temperature of the present invention is primarily based on the crystalline melting point of the resin, but even if it does exist, it is difficult to measure the resin, such as a multi-component copolymer. Alternatively, in compositions of many types of resins, measurement is difficult, and non-quality resins do not have crystal melting points.

Note that, if necessary, this rolling operation may be repeated or the original fabric may be preheated before rolling.

The temperature difference between the upper roll and lower roll for carrying out the rolling of the present invention is usually 10°C or more, preferably 20°C or more. If the temperature difference is 7° C., the relaxation phenomenon will not be sufficiently improved. Tendency to wrap around the horizontal axis during heat shrinkage (vertical warpage)
does not occur sufficiently.

The rolling of the present invention must be carried out to achieve a specific rolling reduction.

In the present invention, the rolling reduction rate (r:%) is calculated using the following formula using the thickness (hl) of the material resin film-like material (original fabric) before rolling and the thickness (h2) of the film-like material after rolling. It can be expressed as

r = 100 ・(h + h 2 ) / h
+The surface roughness of the rolling roll used to create the heat-shrinkable film of the present invention is generally Is or less, preferably 0.5S or less, in order to reduce the scattering of visible light on the surface of the rolled film. , more preferably set to 0.28 or less.

The roughness used in the present invention is the maximum height (Rmax) defined in JIS BO601.

The heat-shrinkable film-like material of the present invention has a total light transmittance of 90
% or more, the haze value is 5% or less, and preferably the total light transmittance is 92% or more and the weight value is 3% or less. If the total light transmittance is 85% or less or the weighing value is 10% or more, the heat-shrinkable film will lack transparency. This is because the scattering of visible light on the surface of the film material is too large.

The heat shrinkage rate of the present invention is the shrinkage rate observed when a film-like material is heat-treated for 30 minutes at a temperature 5° C. lower than the crystalline melting point of the resin. The measurement is performed as follows.

Five or more test pieces shown in FIG. 1 are sampled, the distance between the points is set to 100 mm, and the gauge points are recorded in each of the longitudinal and lateral directions of the test piece film or sheet. This sample piece is placed horizontally in a gear aging tester kept at a temperature 5°C lower than the crystalline melting point (softening point in the above specific case) of the resin for 30 minutes, and then at 25°C for 12 hours or more. After cooling, the distance between the vertical and horizontal gauge points is measured, and the shrinkage rates in the vertical and horizontal directions are calculated using the following equations.

Since the test piece warps in the vertical direction (it shows a tendency to wrap around the horizontal axis) when heated, the length of the arc between the gauge points is measured.

It is desired that the heat-shrinkable film of the present invention has a longitudinal shrinkage rate of 10% or more, preferably 20% or more, and more preferably 30% or more, as measured by the method described above. If the shrinkage rate at a temperature 5° C. lower than the crystal melting point (softening point in the above specific case) is 5%, the shrinkage rate is insufficient for a heat-shrinkable film-like material.

[Examples] Hereinafter, the present invention will be explained in more detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

In addition, the physical properties of the thermoplastic film-like materials in Examples and Comparative Examples were evaluated by the following method.

1) Melting point: DS measured according to JIS K7121
This is the temperature at which the apex of the peak of the C curve is located.

If there are multiple peaks, the temperature at which the peak with the largest area is located is taken as the temperature.

2) Total light transmittance: Measured in accordance with JIS K7105.

3) JL value: Measured in accordance with ASTM D1003.

4) Warpage after heat shrinkage: After the heat shrinkage test explained above, place the film with the convex side facing up on a flat table, and mark ○, 10 mm when the distance from the table to the convex side of the film is 10 mm or more. When it is less than, it is expressed as ×.

5) Relaxation phenomenon: Length 26 in the longitudinal direction of the film-like object
Cut out a sample piece of Omm x width of 30 mm, and glue both ends of the film so that it forms a ring shape with a diameter of 80 mm, with the surface in contact with the roll on the high temperature side facing inside.

The ring is attached to a glass bottle with a diameter of 74 mm, and heated for 10 seconds at an ambient temperature of 200°C. A relaxation phenomenon was observed after cooling at 25° C. for 60 minutes.

When there is no relaxation phenomenon: A 2B if there is a relaxation phenomenon 20 in case of insufficient contraction It was expressed as

℃, lower roll temperature 130°C, rolling blade 39 tonf and rolling reduction rate 75% or rolling blade 32 tonf and rolling reduction rate 67
%, two rolled films (thickness 0.0
50 mm ) was obtained.

Table 1 shows the total light transmittance, haze value, and heat shrinkage rate of each of the rolled films.

As Comparative Example 1, both the upper roll and the lower roll were rolled at a temperature of 120°C.

As Comparative Example 2, the upper roll temperature was 120°C and the lower roll temperature was 1.
Table 1 shows the results when rolled at 25° C. and when a non-stretched film with a thickness of 0.050 mm was used as Comparative Example 3.

Examples 1-2 and Comparative Examples 1-3 Crystalline polypropylene homopolymer (abbreviated as rPPJ).

Melt flow rate 1-0g/10m1n, density 0
, 90 g/cc, melting point 162°C) 2 sheets (thickness 0.
20 mm x width 250 am and thickness 0.15 II 1 m x width 250 mm) with a pair of rolling rolls (roll diameter 300 m
Example 3-4 and Comparative Examples 4-6 Crystalline propylene-ethylene random copolymer (rR
-Abbreviated as PPJ. MF82.2g/10mln, density 0
．． 90 g/cc, melting point 142°C, propylene component content 96% and ethylene component content 4 mol%) 2 sheets (
Thickness 0.20mm x width 250mm and thickness 0.15mm
x width 250 mm), and a pair of rolling rolls with an upper roll temperature of 90°C and a lower roll temperature of 110°C, a rolling blade of 35 tonf and a rolling reduction rate of 78% or a rolling blade of 28 to
Rolling treatment was performed at nf and rolling reduction rate of 70%, and 2
A sheet of rolled film (thickness 0.045 mm) was obtained.

Table 1 shows the total light transmittance, haze value and heat shrinkage rate of the film.

As Comparative Example 4, both the upper roll temperature and the lower roll temperature are 1.
When rolled at 00°C, Comparative Example 5, when rolled at an upper roll temperature of 96°C and lower roll temperature of 100°C, and Comparative Example 6, when the unrolled film (thickness: 0.045 mm) itself was used. The results are shown in Table 1.

Examples 5-6 and Comparative Examples 7-9 Crystalline propylene-ethylene block copolymer (rB
-Abbreviated as PPJ, MFR0.5g/10m1n, density 0
．． 91g/cc, melting point 160℃, propylene component content M
92 mol%, ethylene component content 8 mol%) sheet 2
(thickness 0.30mm x width 250mm and thickness 0.20mm)
mHnx width 25 On+m) 1, upper roll temperature 110°C and lower roll temperature 12 in a pair of rolling rolls.
Two rolled films (thickness: 0.050 mm) were obtained by rolling at 5° C. with a rolling blade of 34 tonf and a rolling reduction rate of 83% or a rolling blade of 30 tonf and a rolling reduction rate of 75%.

Table 1 shows the total light transmittance, haze value and heat shrinkage rate of the film.

Comparative Example 7 is a case where the upper roll temperature and lower roll temperature are both 120°C, and Comparative Example 8 is a case where rolling is performed at an upper roll temperature of 120°C and a lower roll temperature of 125°C, and Comparative Example 9 is an unrolled film. (thickness: 0.050 mm) Table 1 shows the results when using the sample itself.

Examples 7 to 8 and Comparative Examples 10 to 12 High density ethylene homopolymer (abbreviated as rHDPEJ. Melt index (MI) 0.8 g/10 m1n,
2 sheets (density 0.95 g/cc and melting point 130°C) (thickness 0.30 mm x width 250 mm and thickness 0.22 m
m x width 250 mm), a pair of rolling rolls with an upper roll temperature of 85°C and a lower roll temperature of 100°C, a rolling force of 35 tonf and a rolling reduction rate of 85% or a rolling blade of 29 to
Two rolled films (thickness: 0.45 mm) were obtained by rolling at nf and rolling reduction of 80%.

Table 1 shows the total light transmittance, haze value and heat shrinkage rate of the film.

Comparative Example 10 is a case where the upper roll temperature and lower roll temperature are both 90°C. Comparative Example 11 is a case where the upper roll temperature is 90°C and lower roll temperature is 95°C. Table 1 also shows the results when using 0.045 ml (11) itself.

[Effects of the Invention] According to the present invention, as a thermoplastic resin film, not only the adhesion to the substrate after heat shrinkage is improved to the same level or higher than that of conventional PVC film (furthermore, its transparency is unmatched). We can provide you with the film you want.

The manufacturing method of the present invention can be carried out with ordinary equipment without requiring any special equipment, and is easy to operate, so it is an invention that produces extremely large economic benefits.

[Brief explanation of the drawing]

FIG. 1 is a plan view illustrating a test piece for measuring heat shrinkage rate in the present invention. A and B... longitudinal direction (molding direction) gauge points C and D...
・Horizontal direction (perpendicular to molding direction) gauge point MD...Longitudinal direction (
Molding direction) TD... Lateral direction (perpendicular to the molding direction) Applicant Chisso Co., Ltd. Company agent Patent attorney Johei Sanno and 1 other person

Claims (2)

[Claims] (1) Total light transmittance is 90% or more, haze value is 5% or less,
A heat-shrinkable film characterized by having a shrinkage rate in the longitudinal direction of 10% or more when heat-shrinked at a temperature 5°C lower than the crystal melting point, and in which the film-like material after shrinkage shows a tendency to roll around the horizontal axis. something like that. (2) A method for producing a heat-shrinkable film material, which comprises rolling a thermoplastic resin between one or more pairs of rolls, and setting a temperature difference of at least 10° C. between an upper roll and a lower roll that are in contact with the resin.