JP3285935B2 - Ethylene resin composition with suppressed off-flavor and odor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ethylene resin composition which is suitable for a food container material in which the presence of a slight off-flavor is a problem.

[0002]

2. Description of the Related Art Polyethylene is widely used as a material for food containers in the form of various molded articles such as films and bottles. In the case where the treatment is performed, there is a disadvantage that the off-flavor and odor of polyethylene is transferred to the packing material, impairing the flavor thereof, and lowering the value. As a method for reducing the transfer of off-flavor and odor of polyethylene, a method of blending a fluorine-containing polymer (JP-A-4-39342) or a method of contacting with a gaseous alcohol having 8 or less carbon atoms (JP-A-60-1985) -38408) and the like have been proposed. However, although these methods are effective in reducing strong off-flavors, they are not effective in suppressing relatively weak off-flavors. For this reason, in the field of food containers, an ethylene-based resin material in which the off-flavor and odor are satisfactorily suppressed has not been provided.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide an ethylene resin material for a food container so that the flavor of the filling is not impaired by the off-flavor of the ethylene resin material. An object of the present invention is to provide an ethylene-based resin material in which an unpleasant odor is suppressed.

[0004]

[Means for Solving the Problems]

[Summary of the Invention] The present inventors have conducted various studies in order to solve the above-mentioned problems, and as a result, by adopting a specific composition, an ethylene-based resin composition in which an unpleasant odor is suppressed has been obtained. The inventors have found that the object of the invention is achieved and completed the present invention.

[0005] That is, the present invention relates to "
100% by weight of an ethylene-based resin of 0% by weight or less, an average particle diameter of 0.01 to 10 μm, a specific surface area of 20 m ² / g or more, and a density of silanol groups present on the surface of 0.25 / A
0.005 to 0.5 parts by weight of amorphous silica that is ² or less,
0.01 to 0.5 parts by weight of antioxidant and 0.01 of neutralizer
~ 0.3 parts by weight of an ethylene-based resin composition ".

DETAILED DESCRIPTION OF THE INVENTION The ethylene resins used in the present invention include high-pressure low-density polyethylene, linear low-density polyethylene, high-density polyethylene, ethylene-vinyl acetate copolymer, and ethylene-acrylate. Copolymers and the like can be mentioned, and these can be used in combination. Among them, linear low-density polyethylene is preferable, and linear low-density polyethylene, which is a copolymer of ethylene and 15% by weight or less of α-olefin, is particularly preferable. As the α-olefin, those having 10 or less carbon atoms, such as butene, hexene and octene, are generally used.

Among such ethylene resins, those having a hexane-soluble content of not more than 20% by weight, preferably not more than 12% by weight are used in the present invention. It is not preferable that the hexane-soluble component is out of this range because the effect of suppressing the off-flavor and off-flavor is not exhibited. These resins can be used as long as they can be molded, and those having a melt flow rate (MFR) of 0.2 to 50 g / 10 min are suitably used as food containers.

The amorphous silica used in the present invention is mainly composed of silicon dioxide, has a tetrahedral structure of SiO ₄ as a basic structure, and has a three-dimensional network structure in which these are irregularly connected to each other. Has become. The density of silanol groups present on the surface of this amorphous silica is 0.25 / A ² or less,
Preferably, it should be 0.15 / A ² or less, and when the one exceeding this range is used, the effect of suppressing off-flavor and odor is not exhibited.

The average particle size of the amorphous silica is 0.01
It is necessary to be from 10 to 10 μm, preferably from 0.5 to 5 μm, and when the one exceeding this range is used, the appearance of the molded article is unfavorably deteriorated. And its specific surface area is 2
It is necessary to be 0 m ² / g or more, preferably 30 m ² / g or more, and when a material less than this range is used, the effect of suppressing off-flavor and odor is not exhibited. Such amorphous silica can be used by appropriately selecting from commercially available products.

The antioxidants used in the present invention are phosphorus-based, phenol-based and sulfur-based antioxidants usually used for polyolefins, and among them, phosphorus-based and phenol-based antioxidants are preferred.

The neutralizing agent used in the present invention is a neutralizing agent such as a metal stearate and a synthetic hydrotalcite commonly used for polyolefin.

The amount of these essential components is based on 100 parts by weight of the above-mentioned ethylene-based resin and 0.004 parts of amorphous silica.
5 to 0.5 parts by weight, preferably 0.05 to 0.15 parts by weight, 0.01 to 0.5 parts by weight of an antioxidant, preferably 0.1 to 0.25 parts by weight and a neutralizing agent of 0.1 to 0.5 parts by weight. The amount is from 0.01 to 0.3 part by weight, preferably from 0.03 to 0.15 part by weight.

If the amount of the amorphous silica is too small, the effect of suppressing the off-flavor is not obtained, while if it is too large, the off-odor of the silica itself is transferred to the packing, which is not preferable. If the amount of the antioxidant is too small, the generation of unpleasant odor due to the deterioration of the resin is remarkable, and the suppression is not sufficiently performed, while if the amount is too large, the unpleasant odor of the antioxidant itself is filled. It is not preferable because it shifts to. Further, when the amount of the neutralizing agent is too small, the effect of suppressing the off-flavor and off-flavor is not exhibited, while on the other hand, when the amount is too large, the off-flavor and off-flavor of the neutralizing agent itself is undesirably transferred to the packing.

In the present invention, in addition to these essential components, auxiliary components usually used for polyolefin such as antiblocking agents, lubricants, antistatic agents and the like, and additional components such as pigments, resins other than ethylene resins, rubbers, etc. It can be appropriately compounded within a range that does not significantly impair the effects of the invention.

The resin composition of the present invention is produced by blending these components and mixing or kneading them. The method of mixing or kneading is a method of mixing and kneading using a known mixing and kneading machine, for example, a V-type blender, a Henschel mixer, a ribbon blender, a roll, an extruder, or the like. Usually, pellets are convenient for handling. Further, a method of forming a master batch in which the amount of the amorphous silica is larger than the final target amount, diluting with an ethylene-based resin at the time of molding, and molding can be employed.

The resin composition of the present invention is suitable as a material for food containers such as the inner bag of a bag-in-box for soft drinks, but is not limited to this use, and may be T-die molding, blown film molding, hollow molding, extrusion molding, or the like. Film, sheet, pipe, etc. by various molding methods such as molding, injection molding, rotational molding, etc.
It can be processed into various molded products such as tubes and tanks, and can be applied to applications that require suppression of off-flavor and odor. As a special use, it can be formed into various composite films by extrusion coating or coextrusion molding on another film, or a steel tube coating material.

[0017]

EXAMPLES In the following examples, evaluation items were in accordance with the following methods. (1) Hexane-soluble matter (% by weight) A 30 μm thick blown film is 10 mm × 5
It is cut into a rectangular shape of 0 mm, weighed and weighed so as to become approximately 5 g. This sample is refluxed and extracted with 200 cc of hexane using a Soxhlet extractor for high temperature for 3 hours. Next, after cooling to room temperature, the extraction residue was dried under reduced pressure, weighed, and compared with the original weight to obtain a hexane-soluble matter.

(2) Average particle size (μm) 1 g of a sample is placed in a 200 ml beaker, 150 ml of deionized water is added thereto, and the mixture is dispersed with ultrasonic waves for 2 minutes with stirring. This dispersion was measured with a Coulter counter aperture tube of 50 μm, and the average particle size was determined from the cumulative distribution diagram.

(3) Specific surface area (m ² / g) 0.5 to 0.6 g of a sample previously dried at a constant temperature of 150 ° C. is placed in a weighing bottle, and further dried in a constant temperature dryer at 150 ° C. for 1 hour. Weigh immediately. This sample was placed in a 3 ml adsorption sample tube and heated to 200 ° C., and the degree of vacuum in the tube was 10 ⁻⁴ m
Degas until reaching mHg. After standing to cool, the adsorption sample tube was placed in liquid nitrogen at about -195 ° C., and P _N2 / P ₀ = 0.05.
The adsorption amount of nitrogen gas at 4 to 5 points is measured under the conditions of 〜0.30 (P _N2 : nitrogen gas pressure, P ₀ : atmospheric pressure at the time of measurement).
A value obtained by subtracting the dead volume from the nitrogen gas adsorption amount is 0 ° C.
Converted to the adsorption amount at 1 atm, the following BET formula X / {V (1-X)} = 1 / (V _m C) + {(C-1)
/ (V _m C)｝ X (where X = P _N2 / P ₀ , V is the equilibrium adsorption amount ml / g,
V _m is the amount of nitrogen gas adsorbed in ml / g required to form a monolayer on the sample surface, and C is expｅｘ (E ₁ -E ₂ ) / R
T｝, E ₁ is the heat of adsorption J · mol ^{−1 on} the first layer, E ₂ is the heat of condensation J · mol ⁻¹ of the adsorbate, and R is the gas constant J · mol ^−1.
· K ^-1, T asked for V _m from the absolute temperature K). This V _m
The specific surface area S was obtained from the following equation. S = 4.35 × V _m

(4) Density of silanol groups (pieces / A ² ) Approximately 5 g of a sample is weighed (W ₁ (g)), dried in a thermostat dryer at 105 ° C. for 4 hours, and immediately weighed (W ₂ (g). ))
Then, the drying loss rate D (%) is obtained from the following equation. D = _{[(W 1 -W 2) / W} 1 ] × 100 Separately, the same sample approximately 5g was weighed (W _T (g)), which 2 hours burning in melting furnaces of 800 to 900 ° C., immediately weighed (W _R (g)) to determine the ignition loss ratio P (%) from the following equation. P = [(W _T −W _R ) / W _T ｝ × 100−D] × 100
/ (100-D) From this P, the number of silanol groups N _SiOH (number / g) per 1 g of the sample is determined by the following equation. ( _Where M _H2O is the molecular weight of water 18 and N _A is Avogadro's number.) N _SiOH = P / M _H2O × N _A × 2 This N _SiOH is divided by S obtained in the above item (3). The silanol group density per unit area was determined and converted to A (angstrom).

(5) Off-flavor and smell The bag is made by heat-sealing four sides of the film so that the inner size becomes 200 × 300 mm, and the bag is covered with aluminum foil.
Irradiation with Mrad gamma rays. After cutting one corner of the bag and filling with 500 ml of 23 ° C. mineral water, the cut end is heat-sealed and sealed. This is covered again with aluminum foil, stored for 1 hour in a gear oven maintained at 80 ± 5 ° C., and then stored for 1 week in a room at 23 ° C. and 50% humidity where it is not exposed to direct sunlight. Next, mineral water (standard sample) placed in an Erlenmeyer flask separately from this evaluation sample was stored in a gear oven kept at 50 ± 5 ° C. for 3 hours, then the mineral water was taken out of the bag, and 10 panelists examined both samples. The following odors and tastes were compared, and one of the following levels was selected and evaluated by the average of the values. Here, the standard sample was used as a reference for tasteless and odorless. Tasteless and odorless… 0, Feel slightly off-flavor odor… 1 Clearly feel off-flavor odor… 2, Feel strong off-flavor odor… 3

(6) MFR (g / 10 min) According to JIS K-6760. (7) Density (g / cm ³ ) According to JIS K-6760.

Examples 1 to 3 Linear low-density polyethylene A powder 100 shown in Table 1 below
In parts by weight, adsorbent a shown in Table 2 (Mizusawa Chemical Industry Co., Ltd.)
Shows 5 weight ratio mixture) and neutralizing agent (calcium stearate) in Table 3: manufacturing, Mizukasil P-527), antioxidants (Chi Bagaigi <br/> chromatography Co. RA1076 and Sandoz Ltd. P-EPQ 4 After mixing for 5 minutes with a Henschel mixer, the mixture was melt-kneaded at 230 ° C with a 40 mm diameter extruder to form pellets. The pellets were heated at a temperature of 220 ° C., a blow-up ratio of 2.0, and a take-up speed of 10 to 15 by a die gap 3 mm inflation molding machine equipped with a 40 mm diameter extruder.
Molded under the conditions of m / min, width 230mm, thickness 75μm
Was obtained. Table 3 shows the evaluation results of the off-flavor and off-flavor of these films.

[0024]

[Table 1]

[0025]

Examples 4 and 5 The same adsorbent, antioxidant and neutralizing agent as used in Example 1 were mixed with 100 parts by weight of high-pressure low-density polyethylene B powder shown in Table 1 as shown in Table 3. Then, a blown film was obtained and evaluated in the same manner as in Example 1. Table 3 shows the results.

Comparative Examples 1 to 10 To 100 parts by weight of various low-density polyethylene powders shown in Table 1, various adsorbents shown in Table 2 and the same antioxidants and neutralizing agents used in Example 1 are shown in Table 3. They were blended as shown, and a blown film was obtained and evaluated in the same manner as in Example 1. Table 3 shows the results.

[0028]

[0029]

According to the present invention, an ethylene-based resin composition which has a remarkable effect of suppressing the slight off-flavor of the ethylene resin and suppresses the presence of a slight off-flavor is a problem. Can be provided.

Continuation of the front page (56) References JP-A-3-41136 (JP, A) JP-A-3-41135 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08L 23 / 04-23/08 C08L 23/16

Claims (1)

(57) [Claims] 1. 100 parts by weight of an ethylene resin having a hexane-soluble content of 20% by weight or less, and an average particle size of 0.01 to 10 μm.
0.005 to 0.5 parts by weight of amorphous silica having a specific surface area of 20 m ² / g or more and a density of silanol groups present on the surface of 0.25 / A ² or less, and an antioxidant 0.01
An ethylene-based resin composition comprising 0.5 to 0.5 parts by weight and a neutralizing agent 0.01 to 0.3 parts by weight.