JPH08337692A - Packaging polyethylene film capable of irradiation with actinic ray - Google Patents

Abstract

PURPOSE: To obtain a polyethylene film which can be used in applications, e.g. in medical applications and applications for foods and as a hygienic material, where it is irradiated with actinic ray, such as radiation, electron beams and ultraviolet rays, to react a modifier for sterilization or impartation of functional characteristics. CONSTITUTION: This film is obtained by extruding a low-density polyethylene or linear low-density polyethylene having a density of 0.900-0.925g/cm<3> and a n-heptane extraction of less than 0.30wt.% (preferably mixed with a high- density polyethylene) and allows irradiation with actinic ray.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention produces an offensive odor even when irradiated with active energy rays such as radiation, electron beams and ultraviolet rays for the purpose of imparting functionality to packaging films and sterilizing contents. It relates to very few polyethylene films for packaging.

[0002]

2. Description of the Related Art Polyethylene films are used in large quantities for packaging various articles because they are excellent in mechanical properties and processability and can be obtained at low cost. Particularly in packaging applications, low-density polyethylene and linear low-density polyethylene, which have excellent heat-sealing properties, transparency, and flexibility, are mainly used. Especially after packaging medical supplies and foods with polyethylene film,
Irradiation with active energy rays such as radiation or electron rays to sterilize the contents, or a film-reactive antistatic agent,
After adding or applying modifiers such as release agents, antibacterial agents, antifogging agents, etc., irradiation with active energy rays is carried out for the purpose of preventing the modifiers from being released from the film. ing. As described above, the use of active energy rays has an advantage that the treatment can be performed at a low temperature in a short time, as compared with the conventional heating method.

However, active energy rays such as electron rays and ultraviolet rays are not limited to contents and reactive modifiers,
It is known that it also acts on the polyethylene film, and that polyethylene is crosslinked, decomposed, or oxidized depending on the irradiation dose. In particular, it has been reported that those having a large degree of branching such as low-density polyethylene and linear low-density polyethylene and being rich in amorphous portions are more susceptible to the effects (Masaki Shinbo, Toshio Kobayashi: Polymer Chemistry, 2
8, 604-609 (1971)). Therefore, when the packaging polyethylene film is used for medical supplies, foods, sanitary materials, etc. and irradiated with active energy rays, there are problems such as generation of a bad odor and coloring.

[0004]

DISCLOSURE OF THE INVENTION According to the present invention, the generation of offensive odor due to irradiation of active energy rays such as radiation, electron beams, and ultraviolet rays is extremely small, and the transparency, heat sealability, and
It is an object of the present invention to provide a polyethylene film for packaging containing low density polyethylene or linear low density polyethylene as a main component, which exhibits excellent processability.

[0005]

According to the present invention, low density polyethylene or linear low density polyethylene having a density of 0.900 to 0.925 g / cm ³ and an n-heptane extraction rate of less than 0.30 wt%. A polyethylene film for packaging capable of irradiating with active energy rays, which is obtained by extrusion molding, is provided, and further low density polyethylene or linear low density polyethylene 40 to 80 wt% and high density polyethylene 20 are provided.
A polyethylene film for packaging which is capable of being irradiated with active energy rays and which is obtained by mixing and extruding 60 to 60 wt% is provided, and the n-heptane extraction rate is X (wt%), 16
After holding at 0 ° C. for 10 minutes, the temperature was once cooled to 23 ° C. at a cooling rate of 10 ° C./min, and the endothermic amount when the temperature was raised again at a temperature rising rate of 10 ° C./min was defined as Y (J / mg). At this time, the low-density polyethylene, or the linear low-density polyethylene and the high-density polyethylene all satisfy the following inequality (1), the packaging polyethylene film capable of being irradiated with active energy rays is provided: <-0.5X + 0.26 (1) Further, there is provided a polyethylene film for packaging capable of being irradiated with active energy rays, characterized in that the polyethylene contains a phenol-based antioxidant and / or a phosphorus-based antioxidant. Further, there is provided a polyethylene film for packaging which can be irradiated with an electron beam, wherein the active energy ray is an electron beam. There is provided the packaging film capable of irradiating ultraviolet rays, wherein the Rugie line is ultraviolet rays, and further, the polyethylene film for packaging irradiating ultraviolet rays, wherein the polyethylene contains an ultraviolet absorber. Further provided is the above-mentioned ultraviolet ray-irradiable packaging polyethylene film, wherein the ultraviolet absorber is ultrafine titanium oxide.

[0006] That is, as a result of studies to achieve the above-mentioned object, polyethylene having a small n-heptane extraction rate X and a large amount of an amorphous portion, which satisfies the following inequality (1), has a bad odor when irradiated with active energy rays. It was found that the occurrence was low. Further, it has been found that the addition of an antioxidant or an ultraviolet absorber to these polyethylenes is extremely effective in preventing the generation of malodor. It seems that the fact that the more the amorphous portion is, the less the foul odor is generated is inconsistent with the view of Shinpo et al. Mentioned above. Although radicals are generated in both the amorphous part and the molecules in the amorphous part are easy to move, the radicals generated in the amorphous part are likely to recombine and stabilize, resulting in less foul odor. There is. Therefore, it is considered that the polyethylene having more amorphous portions has less breakage of the molecular chain due to irradiation with active energy rays, and less volatile components causing an offensive odor. The n-heptane extraction rate (wt
%) Is a value measured after immersing the pellet-shaped polyethylene in heptane at 30 ° C. for 90 hours, and the endothermic amount (J / mg) represented by Y is first measured by a differential scanning calorimeter (DSC). Was heated and held at 160 ° C. for 10 minutes, then once cooled to 23 ° C. at a cooling rate of 10 ° C./min, and the endothermic amount was measured when the temperature was raised again at a heating rate of 10 ° C./min. is there. Y <-0.5X + 0.26 (1)

Therefore, when low density polyethylene or linear low density polyethylene having a density in the range of 0.900 to 0.925 g / cm ^{3 which} is suitable for the packaging purpose of the present invention is used, n-heptane is used. Extraction rate is 0.30wt
It has been found that the use of less than 10% is an essential requirement, and the present invention has been completed.

The present invention will be described in detail below. The low density polyethylene used in the present invention has a density of 0.915-0.
A polyethylene obtained by a high pressure method of about 925 g / cm ³ and having a large number of branches in the molecule. Also,
Linear low-density polyethylene has a density of 0.900-0.
A copolymer of ethylene having about 925 g / cm ³ and an α-olefin having 4 to 8 carbon atoms, which is a short chain derived from α-olefin having 4 to 8 carbon atoms in a linear molecular structure. A linear low-density polyethylene having a highly branched molecular weight and degree of branching, which is produced by using a single-site catalyst such as a metallocene catalyst, which has a branch and has recently become commercially available, is also included in the present invention. include. In the present invention, it is necessary to use, among these low-density polyethylene and linear low-density polyethylene, an n-heptane extraction rate X of less than 0.30 wt%, that is, a low-molecular weight component is small.

Further, high density polyethylene has a density of 0.
It means polyethylene produced by the Ziegler method at about 945 to 0.965 g / cm ³ . Generally, high-density polyethylene is superior to low-density polyethylene and linear low-density polyethylene in mechanical strength and heat resistance, but it is transparent, processable, heat-sealable, or flexible when used as a packaging film. Slightly inferior.

Therefore, the packaging film aimed at by the present invention can be achieved by using low density polyethylene or linear low density polyethylene satisfying the above conditions alone or by mixing them. Most preferably, it is used as a mixture with high-density polyethylene for the purpose of imparting mechanical strength, some stiffness, or heat resistance. The mixing ratio at this time is preferably 40 to 80 wt% of low-density polyethylene or linear low-density polyethylene and 20 to 60 wt% of high-density polyethylene, although it depends on the performance required for the intended packaging film. If the blending ratio of the high-density polyethylene is less than this range, a sufficient modifying effect cannot be expected, and if the blending ratio exceeds this range, the n-heptane extraction ratio is generally small, but the influence of the high-density polyethylene having many crystal parts It is not preferable because a bad odor is likely to be generated and transparency and processability are deteriorated. For this reason, all of the polyethylenes used in the present invention have the above-mentioned inequality (1).
Is preferably satisfied.

Furthermore, 2,6-di-t is added to the above polyethylene.
-Butyl-4-methylphenol, 1,6-hexanediol-bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], pentaerythrityl-tetrakis [3- (3,5 -Di-t-butyl-4
-Hydroxyphenyl) propionate], 2-t-butyl-6- (3'-t-butyl-5'-methyl-2'-
Hydroxybenzyl) -4-methylphenyl acrylate, (2,2-thio-diethylenebis [3- (3,5-
Di-t-butyl-4-hydroxyphenyl) propionate], octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate and other hindered phenolic antioxidants and tetrakis- (2, 4-
Such as di-t-butylphenyl) 4,4-biphenylene diphosphonate, tris (2,4-di-t-butyl) phenyl phosphite, tris (2,4-di-t-butylphenyl) phosphite. It is preferable to add a phenolic antioxidant and / or a phosphorus antioxidant such as a phosphorus antioxidant. Of these antioxidants, the phenol-based antioxidant can be used alone, but it can be used in combination with the phosphorus-based antioxidant, and the addition amount thereof is 0.02-0.5 wt% (200 ~ 5000pp
m) is preferred. It is not preferable to add a large amount of the phenolic antioxidant, because if it is added in too large a quantity, it will turn yellow upon irradiation with active energy rays.

When the active energy rays are ultraviolet rays, it is preferable to add an organic ultraviolet absorber such as benzophenone type or triazole type or an inorganic type ultraviolet absorber such as fine particles of zinc oxide, titanium oxide or iron oxide. preferable. Organic UV absorbers are preferably used when transparency of the film is required, and inorganic UV absorbers having no bleed-out are preferably used when transparency is not required. The addition amount of these UV absorbers is preferably 0. 1 to 10% by weight is preferable.
Particularly in the present invention, it is preferable to use ultrafine particle titanium oxide as the ultraviolet absorber.

Further, in the present invention, a lubricant, an anti-blocking agent, a colorant, an antistatic agent and the like can be added, if necessary, in addition to the antioxidant and the ultraviolet absorber.
Among them, the colorant also has an effect of blocking ultraviolet rays and is therefore effective in preventing the generation of offensive odors.

The polyethylene film for packaging of the present invention can be manufactured by a usual extrusion molding method such as an inflation method or a T-die method. In addition, when the T-die method is used, polyethylene having a high melt index (that is, a low molecular weight and a large amount of low-molecular components is considered to be used) is often used as compared with the inflation method. Therefore, the resin composition of the present invention is used. Is most effective.

[0015]

The polyethylene film for packaging which can be irradiated with active energy rays of the present invention has few low molecular weight components which are easily decomposed by active energy rays such as electron beams and ultraviolet rays, and radicals generated by the active energy rays are recombined and stabilized. As a main raw material is a specific polyethylene that is difficult to crystallize, and an antioxidant and an ultraviolet absorber are added if necessary, so that low molecular weight volatile components that cause an offensive odor even when irradiated with active energy rays are generated. Is expected to decrease. Therefore, the polyethylene film for irradiation with active energy rays of the present invention does not generate an offensive odor even when irradiated with active energy rays such as electron beams and ultraviolet rays, and is suitably used in the fields of medical, food, sanitary materials, etc. be able to.

[0016]

EXAMPLES Next, the present invention will be specifically described with reference to examples. The evaluation was performed according to the following method. <N-Heptane extraction rate (wt%)) 20 g of polyethylene pellets were immersed in 50 g of heptane at 30 ° C for 90 hours, and the weight (wt%) eluted in heptane was measured. <Endotherm (J / mg)> Using a differential scanning calorimeter (DSC), polyethylene was first heated and held at 160 ° C for 10 minutes, then cooled once to 23 ° C at a cooling rate of 10 ° C / min, and again 10 The amount of endotherm when the temperature was raised at a temperature rising rate of ° C / min was measured. <Evaluation of offensive odor generation> Evaluation of raw material pellets After using an ultraviolet irradiation device equipped with a high-pressure mercury lamp (80 W / cm: manufactured by Iwasaki Electric), 10 g of polyethylene pellets put in a petri dish was passed once at a speed of 15 cm / min. Immediately, the polyethylene pellets were placed in an Erlenmeyer flask and sealed tightly, and a sensory test of the offensive odor generated was carried out to judge.・ Evaluation by line test of film [Method A] 8 film at line speed of 10 m / min
After passing through a 0 W / cm ultraviolet irradiation device, the presence or absence of a bad odor was evaluated by a sensory test. [Method B] The film was passed through a 240 W / cm ultraviolet irradiation device at a line speed of 100 m / min, and the presence or absence of a bad odor was evaluated by a sensory test. The evaluation standard is method A,
Both B are as follows. ◯: No offensive odor was observed Δ: Slight offensive odor was observed ×: Clearly offensive odor was observed

The antioxidants, ultraviolet absorbers and colorants used in this example are as follows. Antioxidant (A): trade name; IRGANOX 1076 (phenolic antioxidant) octadecyl-3- (3,5-di-t-butyl-4-human oxyphenyl) propionate (Ciba Geigy) Antioxidant (B): Product name; Sandostab P-EPQ (phosphorus antioxidant) Tetrakis- (2,4-di-t-butylphenyl) 4,4-biphenylene phosphonite (sand) UV absorber: Product name; 7H213 Fine particle oxidation Low Density Polyethylene Masterbatch with 60wt% Titanium Content (Sumika Color) Colorant: Trade Name; 7G-480 Low Density Polyethylene Masterbatch with 60wt% Titanium White Content (Sumika Color)

Reference Example The following various polyethylenes were tested for n-heptane extraction rate, endothermic amount and presence / absence of malodor. The results are shown in Table 1.
And shown in FIG. <High Density Polyethylene> PE (A): trade name; Hi-Zex 3300F density = 0.950 g / cm ³ , MI = 1.10 g / 10 min (Mitsui Petrochemical Industry) PE (B): trade name; Shorex HD5050 density = 0.950 g / cm ³ , MI = 5.50 g / 10 min (Showa Denko) PE (C): Trade name; 7000F Density = 0.956 g / cm ³ , MI = 0.04 g / 10 min (Mitsui Nisseki Polymer) PE (D): trade name; E905FA density = 0.949 g / cm ³ , MI = 0.05 g / 10 min (Nippon Petrochemical) PE (E): trade name; UP polyethylene HD1150 density = 0.96 g / cm ³ , MI = 15.0 g / 10 minutes (Maruzen Polymer)

<Low-density polyethylene> PE (F): Trade name; Sumikasen L718H Density = 0.919 g / cm ³ , MI = 8.0 g / 10 min (Sumitomo Chemical Co., Ltd.) PE (G): Trade name: Sumikasen L705 Density = 0.918 g / cm ³ , MI = 7.0 g / 10 min (Sumitomo Chemical Industries) PE (H): Trade name; Sumikasen L719H Density = 0.918 g / cm ³ , MI = 7.0 g / 10 min ( Sumitomo Chemical Co., Ltd. PE (I): Trade name; Sumikasen F208-0 Density = 0.92 g / cm ³ , MI = 1.5 g / 10 min (Sumitomo Chemical Co., Ltd.) PE (J): Trade name; LD186 Density = 0 .92 g / cm ³ , MI = 3.0 g / 10 min (Union Polymer)

<Linear low-density polyethylene> PE (K): Trade name; Sumikasen FA201-0 Density = 0.92 g / cm ³ , MI = 2.0 g / 10 min (Sumitomo Chemical Co., Ltd.) PE (L): Affinity PL1880 Density = 0.902 g / cm ³ , MI = 1.0 g / 10 min (Dow Chemical) PE (M): trade name; Esplen SPO NO352 Density = 0.905 g / cm ³ , MI = 2.0 g / 10 Minutes (Sumitomo Chemical Industries)

[0021]

[Table 1]

As is clear from Table 1, in the case of low-density polyethylene or linear low-density polyethylene, the use of an n-heptane extraction rate of less than 0.30 wt% can prevent the generation of malodor. It can be seen that in the case of high-density polyethylene, even if the n-heptane extraction rate is less than 0.30 wt% as in PE (C) and PE (E), a foul odor is slightly generated. Further, in the case of a resin having an extremely small endothermic amount such as PE (M), even if the n-heptane extraction rate exceeds 0.30 wt%, a bad odor is slightly generated, and the above inequality (1) is satisfied. Is an essential condition for preventing the generation of a bad odor when irradiated with active energy rays.

Examples 1-4 and Comparative Example 1 The resins shown in Table 2 were supplied to an extruder and a thickness of 3 was obtained by the T-die method.
A polyethylene film of 0 μm was obtained. The obtained film was irradiated with ultraviolet rays under the conditions of Method A or B to measure whether or not a bad odor was generated. The results are also shown in Table 2.

[0024]

[Table 2]

As is clear from Table 2, the film of Comparative Example 1 made of PE (G) having a high n-heptane extraction ratio produces a bad odor, whereas PE (F) having a low n-heptane extraction ratio is generated. In Example 1 consisting of the above, only a slight odor is generated, and when the irradiation intensity of ultraviolet rays is small as in Method A, the generation of a bad odor can be prevented. Further, it can be seen that in the case of the film of Example 2 in which an antioxidant is added thereto or the film of Example 3 in which an ultraviolet absorber is added, the generation of malodor can be prevented even when the ultraviolet intensity is increased.
Further, it can be seen that titanium white, which has been conventionally used as a white pigment, has little effect of preventing the generation of malodor, but ultrafine particle titanium oxide has an extremely excellent effect of preventing generation of malodor.

The film of Example 4 having a resin composition obtained by blending low-density polyethylene with high-density polyethylene is not only effective for the generation of malodor, but also has a tensile load of 1200 g / 25 mm in the MD direction, which is a low density of the prior art. It is higher than polyethylene film and has further improved waist strength and heat resistance, so it can be suitably used for various packaging applications.

[0027]

As described above, the packaging polyethylene film capable of being irradiated with active energy rays according to the present invention does not generate a volatile low molecular weight substance even when irradiated with active energy rays such as radiation, electron rays and ultraviolet rays. It has the feature that it does not generate an offensive odor. Therefore, the polyethylene film of the present invention is a medical, food, or hygiene material that is irradiated with active energy rays such as radiation, electron beams, and ultraviolet rays for the purpose of sterilizing or reacting with a modifier for imparting functionality. It can be preferably used for applications such as use.

[Brief description of drawings]

FIG. 1 n-heptane extraction rate (wt) of various polyethylenes
%), The amount of heat absorption (J / mg), and the presence or absence of the generation of malodor in the state of pellets.

[Explanation of symbols]

 ○: No offensive odor was found △: Slight offensive odor was found ×: Clear offensive odor was found

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display area C09K 15/24 C09K 15/24

Claims (8)

[Claims] 1. A density of 0.900 to 0.925 g / cm ³ , n
A polyethylene film for packaging capable of being irradiated with active energy rays, which is obtained by extrusion-molding low-density polyethylene or linear low-density polyethylene having a heptane extraction rate of less than 0.30 wt%. 2. The packaging for irradiation with active energy rays according to claim 1, wherein 40-80 wt% of the low-density polyethylene or linear low-density polyethylene and 20-60 wt% of high-density polyethylene are mixed and extrusion-molded. Polyethylene film. 3. An n-heptane extraction rate of X (wt%), 16
After holding at 0 ° C. for 10 minutes, the temperature was once cooled to 23 ° C. at a cooling rate of 10 ° C./min, and the endothermic amount when the temperature was raised again at a temperature rising rate of 10 ° C./min was defined as Y (J / mg). The polyethylene film for packaging capable of being irradiated with active energy rays according to claim 2, wherein the low-density polyethylene, or the linear low-density polyethylene and the high-density polyethylene all satisfy the following inequality (1). Y <-0.5X + 0.26 (1) 4. A polyethylene film for packaging which can be irradiated with active energy rays, wherein the polyethylene according to claim 1 or 2 contains a phenolic antioxidant and / or a phosphorus antioxidant. 5. The polyethylene film for packaging which can be irradiated with an electron beam according to claim 1, wherein the active energy ray is an electron beam. 6. The packaging film capable of being irradiated with ultraviolet rays according to claim 1, wherein the active energy rays are ultraviolet rays. 7. A polyethylene film for packaging which can be irradiated with ultraviolet rays, wherein the polyethylene according to claim 6 contains an ultraviolet absorber. 8. The polyethylene film for packaging capable of ultraviolet irradiation according to claim 7, wherein the ultraviolet absorber is ultrafine titanium oxide.