JPH0733151A - Packaging bag and manufacturing method thereof - Google Patents

Abstract

(57) [Summary] [Structure] 100 parts by weight of linear low density polyethylene having a melt index of 2 g / 10 minutes or less, 0.0001 to 0.1 parts by weight of a radical generator, and calcium carbonate 20.
~ 150 parts by weight and a packaging bag formed by molding a polyethylene resin composition containing 0.1 to 10 parts by weight of a plasticizer to 100 parts by weight of the above total, and inflation molding of the polyethylene resin composition. A method for producing a packaging bag, which comprises heat-sealing and cutting the obtained tubular film with a direction intersecting the take-up direction as a longitudinal direction. [Effect] It is possible to obtain a packaging bag with improved incineration while maintaining high heat-sealing strength and body strength.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a packaging bag and its manufacturing method. Specifically, a mixture of a linear low density polyethylene with a radical generator, calcium carbonate and a plasticizer, obtained by inflation molding and heat sealing, has high heat seal strength and body strength, and low calorie. The present invention relates to a packaging bag having high incineration property and a manufacturing method thereof.

[0002]

2. Description of the Related Art A film having a high incineration property in which polyethylene is mixed with an inorganic filler such as calcium carbonate is already known. Also, a method for producing a packaging bag in which a specific linear low density polyethylene is treated with a radical generator and having high heat-sealing strength and body strength is already known (Japanese Patent No. 17319929 etc.).

[0003]

However, in order to improve the incineration property, it is necessary to add a certain amount or more of the inorganic filler, which causes a decrease in strength.
It was not possible to obtain a packaging bag having high heat-sealing strength and body strength while having high incineration property.

[0004]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies in order to obtain a packaging bag that solves the above-mentioned problems, and as a result, a radical generator for a specific linear low density polyethylene,
It was found that a packaging bag having high incineration property and high heat-sealing strength and body strength can be obtained by inflation-molding and heat-sealing a mixture of calcium carbonate and a plasticizer, thus completing the present invention. Came to.

That is, the gist of the present invention is that the linear low-density polyethylene 1 having a melt index of 2 g / 10 min or less.
Polyethylene resin obtained by blending 100 parts by weight of a radical generator, 0.0001 to 0.1 part by weight of a radical generator, 20 to 150 parts by weight of calcium carbonate, and 100 parts by weight of the total amount of the plasticizer. A packaging bag formed by molding the composition, and inflation molding the polyethylene resin composition, and heat-sealing and cutting the obtained tubular film with the direction intersecting the take-up direction as the longitudinal direction. It lies in the method of manufacturing the packaging bag.

The present invention will be described in more detail below. The linear low density polyethylene used in the present invention is
It is a copolymer of ethylene and other α-olefin and is different from the low density polyethylene resin produced by the conventional high pressure method. The linear low-density polyethylene is obtained by copolymerizing, for example, ethylene with other α-olefins such as butene, hexene, octene, decene, and 4-methylpentene-1 in an amount of about 4 to 17% by weight, preferably about 5 to 15% by weight. It is produced using a Ziegler type catalyst or a Phillips type catalyst used in the production of high-density polyethylene by the medium and low pressure method. This is because the conventional high-density polyethylene has a short branched structure due to the copolymerization component, and the density is appropriately reduced by utilizing this short-chain branching to 0.91 to 0.9.
It is about 5 g / cm ³ , and is a polyethylene having a structure that is more linear than conventional low-density polyethylene and more branched than high-density polyethylene.

The linear low density polyethylene used in the present invention has a melt index of 2 g / 10 min or less, preferably 0.1-1.0 g / 10 min, obtained by copolymerizing ethylene and α-olefin. , And more preferably 0.
Those having a range of 2 to 0.8 g / 10 minutes are used. When the melt index is more than the above range, the strength of the body portion of the packaging bag is lowered, which is not preferable. The preferable density of the linear low density polyethylene in the present invention is 0.91.
5 to 0.935 g / cm ³ , and a preferable flow ratio is
It is 35 or less.

In the present invention, although only the linear low-density polyethylene described above may be used, the linear low-density polyethylene is the main component, and the low-density polyethylene, the high-density polyethylene, the ultra-low-density polyethylene, and the ethylene-α-olefin are used. A polyethylene polymer such as a copolymer rubber may be blended in such a manner that the melt index of the mixture is 2 g / 10 minutes or less. The flow ratio of the mixture is preferably 70 or less from the viewpoint of strength of the heat-sealed portion.

The above-mentioned compoundable polyethylene-based polymers include those containing ethylene homopolymers and copolymers of ethylene with other copolymerization components, and the copolymerization components include vinyl acetate and ethyl. Vinyl compounds such as acrylate and methyl acrylate, propylene, butene,
Examples include olefins having 3 or more carbon atoms such as hexene, octene, and 4-methylpentene-1.

The copolymerization amount of the copolymerization component is 0.5 to 1
It is about 8% by weight, preferably about 2 to 10% by weight. Starting
What is Melt Index in Ming? JIS K6760
Is the value measured at 190 ° C., and the flow ratio is
Shear force obtained using the above melt index measuring device
10⁶Dynes / cm²(Load 11131g) and 10^FiveDa
In / cm ²Extrusion rate (g / 103g) (g / 10
Min), and the extrusion rate at a load of 11131 g (10 min)
Interval) ÷ Calculated by the extrusion rate (10 minutes) at a load of 1113 g
Be done. The density is measured according to JIS K6760.
It is the value.

The flow ratio is a measure of the molecular weight distribution of the resin used, and the smaller the flow ratio value is, the narrower the molecular weight distribution is.
The larger the flow ratio value, the wider the molecular weight distribution. Next, as a radical generator added to linear low-density polyethylene, the decomposition temperature at which the half-life is 1 minute is 13
Those in the range of 0 ° C. to 300 ° C. are preferable, for example, dicumyl peroxide, 2,5-dimethyl-2,5-di (t
-Butylperoxy) hexane, 2,5-dimethyl-
2,5-di (t-butylperoxy) hexyne-3,
a, a'-bis (t-butylperoxyisopropyl)
Examples thereof include benzene, dibenzoyl peroxide and di-t-butyl peroxide.

The amount of the radical generator added is selected from the range of 0.0001 to 0.1 part by weight based on the linear low density polyethylene. When the addition amount is less than 0.0001 parts by weight, the strength of the heat-sealed portion of the obtained packaging bag is almost the same as that of the additive-free one, and when it is more than 0.1 parts by weight, It is not preferable because the melt index becomes too low and film breakage easily occurs during film formation, and the surface of the film becomes rough.

On the other hand, this addition amount is 0.002-0.02
The range of parts by weight is preferable because the film moldability and the strength of the heat seal part are significantly improved. In the present invention, the method of adding a radical generator, calcium carbonate and a plasticizer to the linear low density polyethylene is not particularly limited and may be carried out, for example, by the following method.

(1) At the time of inflation molding, the linear low-density polyethylene, the radical generator, calcium carbonate and a plasticizer are fed simultaneously or sequentially and melt-extruded. (2) Using a kneader such as an extruder or a Banbury mixer, the linear low-density polyethylene and the radical generator are kneaded and reacted, and then pelletized, and then calcium carbonate and a plasticizer are added to the pellets. Blend and blow mold.

(3) A masterbatch containing a large amount of a radical generating agent (polyethylene such as high density polyethylene, branched low density polyethylene or linear low density polyethylene with a large amount of radical generating agent at a temperature not lower than the melting point of the polyethylene). A polyethylene masterbatch containing a high concentration (usually about 200 to 20000 ppm) of a radical generator melt-kneaded at a temperature at which the polyethylene does not react with the radical generator, for example, at a temperature of 130 to 160 ° C.) Is prepared in advance, and the master batch, the linear low-density polyethylene, calcium carbonate, and a plasticizer are blended and inflation-molded.

The radical generator itself may be used as it is or after being dissolved in a solvent. By reacting the linear low density polyethylene with a radical generator,
The polyethylene undergoes a crosslinking reaction to increase the high molecular weight component and to obtain a modified polyethylene having a reduced melt index. The modified polyethylene has improved film moldability as compared with unmodified linear low-density polyethylene, and is more likely to be oriented in the longitudinal direction during inflation molding. The film thus obtained is oriented in the direction subjected to heat sealing. It is preferable because it shrinks to a thickness larger than the original thickness of the film and the strength of the heat-sealed portion is improved.

The calcium carbonate used in the present invention is
Although not particularly limited, those having an average particle size of 0.5 to 6 μm which is surface-treated with a higher fatty acid are preferable. Surface treatment with higher fatty acids is effective for uniformly dispersing calcium carbonate in linear low-density polyethylene,
The surface treatment method is performed, for example, by mixing and stirring calcium carbonate and a higher fatty acid while heating.

Preferred higher fatty acids in the surface treatment are
A higher fatty acid having 10 or more carbon atoms is preferably mixed in an amount of 0.1 to 5 parts by weight with respect to 100 parts by weight of calcium carbonate. If the average particle size is less than the above range, the particles are likely to coagulate, and the heat seal strength and the body strength of the packaging bag are reduced, which is not preferable.

Further, if the content is more than the above range, the heat seal strength and the body strength of the packaging bag are lowered, which is not preferable. The blending ratio of calcium carbonate in the present invention is
20 to 150 parts by weight of calcium carbonate is preferably used for 100 parts by weight of linear low-density polyethylene in order to ensure easy incineration and strength of the packaging bag.

As the plasticizer used in the present invention, various ones usually used as plasticizers for vinyl chloride resins can be used, and are not particularly limited, and include phthalic acid ester plasticizers and aromatic compounds. Carboxylic acid ester plasticizer, aliphatic dibasic acid ester plasticizer, aliphatic ester derivative plasticizer, phosphoric acid ester plasticizer, epoxy plasticizer, chlorine plasticizer, polyester plasticizer,
Other plasticizers are used.

Examples of the phthalic acid ester plasticizer include dimethyl phthalate, diethyl phthalate, dibutyl phthalate, diisobutyl phthalate, diheptyl phthalate, dioctyl phthalate, di-2-ethylhexyl phthalate, di-isooctyl phthalate, dinonyl phthalate, diisononyl. Phthalate, didecyl phthalate, diisodecyl phthalate, dilauryl phthalate, dicyclohexyl phthalate, diphenyl phthalate, dibenzyl phthalate, di (mixed alcohol) phthalate, dibutoxyethyl phthalate, butyl lauryl phthalate, butyl benzyl phthalate, butyl octyl phthalate, octyl decyl phthalate. , Butyl cyclohexyl phthalate and the like.

Examples of the aromatic carboxylic acid ester plasticizer include tri-2-ethylhexyl trimellitate,
Examples thereof include tri-n-octyl trimellitate, tridecyl trimellitate, tributyl trimellitate, dibutylbenzyl trimellitate and diethylene glycol dibenzoate. Examples of the aliphatic dibasic acid ester-based plasticizer include di-n-hexyl adipate, dioctyl adipate, di-n-ethylhexyl adipate, diisodecyl adipate, dicapryl adipate, dibutyl sebacate, dioctyl sebacate, di-2-ethylhexyl sebacate. Kate, dioctyl azelate, di-2-
Examples thereof include ethylhexyl azelate, butyl fumarate, dioctyl fumarate, dioctyl succinate, diisodecyl succinate, dioctyl tetrahydrophthalate and the like.

Examples of the aliphatic ester derivative type plasticizer include butyl oleate, methylacetyl ricinolate, dipentaerythritol hexaester, pentaerythritol ester and the like. Examples of the phosphoric acid ester-based plasticizer include trioctyl phosphate,
Examples thereof include trichloroethyl phosphate, tributyl phosphate, tri (2-ethylhexyl) phosphate, tributoxyethyl phosphate, triphenyl phosphate, cresyl diphenyl phosphate, tricresyl phosphate, diphenyl octyl phosphate and the like.

Examples of the epoxy plasticizer include butyl epoxy stearate, octyl epoxy stearate, octyl epoxy benzoate, epoxidized soybean oil, benzyl epoxy stearate, and epoxidized dioctyl hexahydrophthalate. Examples of the chlorinated plasticizer include chlorinated paraffin, chlorinated methyl stearate, chlorinated diphenyl, chlorinated benzyl laurate, chlorinated diphenylbenzene and the like.

Examples of the polyester plasticizer include polypropylene adipate and polypropylene sebacate. These plasticizers can be used alone or in admixture of two or more. The mixing ratio of the plasticizer is selected from the range of 0.1 to 10 parts by weight with respect to the total 100 parts by weight of the linear low density polyethylene, the radical generator and the calcium carbonate, and the mixing ratio is 0.1 parts by weight. When the amount is less than 10 parts by weight, the strength of the heat-sealed portion of the obtained packaging bag is almost the same as that of the additive-free one, and when it is more than 10 parts by weight, it is deposited on the film surface and causes blocking or printability. And the heat sealability are deteriorated, which is not preferable.

The preferred mixing ratio of the plasticizer is 0.5 to 5 parts by weight. Further, when the molecular weight of the plasticizer is higher than about 400, it is difficult to deposit on the film surface, which is preferable.
In order to obtain a product with good heat-sealing strength, rather than simply inflation molding the modified linear low-density polyethylene blended with calcium carbonate and a plasticizer, the following specific molding is used. The condition is preferable.

The specific molding conditions are inflation molding with a blow-up ratio of 0.9 to 2, a draft ratio of 10 to 40, and a cooling rate index of 30 seconds or less. Here, the draft rate is obtained by the following formula.

[0028]

[Equation 1]

The cooling rate index is the time (sec) until the molten resin is extruded from the die and reaches the frost line, and is obtained by the following formula.

[0030]

[Equation 2]

When the blow-up ratio is 2.0 or more, shrinkage in the longitudinal direction of the heat seal occurs at the time of heat sealing, and distortion occurs in the direction opposite to the orientation of the bag body. The strength is reduced and it causes bag breakage. When the draft ratio is 10 or less, good shrinkage does not occur during heat sealing, and when it is 40 or more, the molecular orientation of the body portion of the bag itself becomes too large in one direction, which causes tearing of the body portion itself.

When the cooling rate index is 30 seconds or more, the molecular orientation generated in the film due to the draft at the time of film formation is relaxed by thermal relaxation, so that the heat seal does not contract and the heat seal portion does not have sufficient strength. The film becomes uneven. Although a heat bar, a heat belt, or the like is used for heat sealing, if the heat sealing portion is pressed for a long time by these heaters, heat relaxation occurs and the strength of the heat sealing portion does not appear. 280
C., preferably about 230 to 280.degree. C., heat is applied to the heat-sealing part as little as possible, and is rapidly heated until the films are fused to each other. It is desirable to use a heat-sealing method that causes the parts to shrink.

[0033]

EXAMPLES The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded.

Example 1 (a) Production of packaging bag Linear low density polyethylene (melt index: 0.6
g / 10 minutes, density: 0.92 g / cm ³ , copolymerization component:
100 parts by weight of hexene-1 and a radical generator (2,
0.01 parts by weight of 5-dimethyl-2,5 di (t-butylperoxy) hexyne-3) and calcium carbonate (average particle diameter: 1.7 μm, surface treatment: 2 parts by weight of stearic acid) 4
0 parts by weight and 3 parts by weight of a plasticizer (tri-2-ethylhexyl trimellitate) are mixed, and then 250 ° C. in an extruder.
Melt-kneaded for 3 minutes and extruded into pellets.

This is a Delsar 65 manufactured by Modern Machinery.
Using an inflation molding machine in which an inflation die with an annular slit diameter of 200 mmφ and an air ring for cooling were attached to a φ type extruder, the extrusion rate was 100 kg / hr, the blow-up ratio was 1.4, and the draft rate was 14 from the air ring. By changing the amount of air blown out, an inflation film having a cooling rate index of 16 seconds and a thickness of 150 μm was obtained.
The resulting blown film has a length of 670 cm,
It was cut into a tubular film having a width of 440 cm, and HS 22B-2 type heat sealer manufactured by New Long Co. (heating unit length 15
0 mm, heating section clearance 0.3 mm, cooling section length:
150 mm, cooling section clearance 1 mm), heat seal temperature (heating section surface temperature) 220 ° C., cooling section temperature 30 ° C., film feed speed 15 m / sec. Heat sealing was performed at a position of 1.5 cm. Fill the obtained bag with 20 kg of fertilizer, heat the opening under the same conditions as above, and heat
After accumulating for 24 hours and leaving it to stand, a packaging bag for a drop bag test was obtained.

(B) Performance test of packaging bag The packaging bag obtained in (a) above was subjected to a lateral drop bag test and a vertical drop bag test by the following methods. (A) Side-dropping bag test 20 bags are dropped (side-down) so that the body of the packaging bag is parallel to the floor surface and the heat-sealed portion is substantially perpendicular to the floor surface, and the test is performed to obtain the bag breakage rate. It was The falling bag test was carried out to measure the strength of the heat-sealed portion of the bag. Drop conditions are room temperature -5 ° C and drop height 1.5.
The number of drops per bag was 5 times. The bag breakage rate was obtained as a percentage of the broken bags of the packaging bags used in the test. The results are shown in Table 1. From a practical point of view, if a bag is broken, it cannot be used.

(B) Vertical drop bag test The test was performed by dropping 20 bags (vertical drop) so that the heat-sealed portion of the packaging bag was parallel to the floor surface and the trunk portion was substantially perpendicular to the floor surface. The bag rate was calculated. The vertical drop bag test was conducted to measure the strength of the body of the bag. The dropping conditions were such that the room temperature was −5 ° C., the drop height was 1.5 m, and the number of drops per bag was 5 times. The bag breakage rate was obtained as a percentage of the broken bags of the packaging bags used in the test. The results are shown in Table 1. From a practical point of view, a bag breakage rate of up to 10% is acceptable.

Example 2 In Example 1, the linear low density polyethylene had a melt index of 0.8 g / 10 minutes, a calcium carbonate content of 100 parts by weight, a plasticizer content of 10 parts by weight, and a blow-up ratio. Except that the cooling rate index was set to 1: 1 and the cooling rate index was set to 28 seconds to obtain an inflation film of 150 μm in the same manner as in Example 1. Then, the bag breakage rate was measured in the same manner as in Example 1. The results are shown in Table 1.

Comparative Example 1 Example 1 was repeated except that no plasticizer was added.
A 150 μm blown film was obtained in the same manner as in. Then, the bag breakage rate was measured in the same manner as in Example 1. The results are shown in Table 1.

Comparative Example 2 Example 1 was repeated except that the linear low density polyethylene had a melt index of 2.6 g / 10 minutes.
A 150 μm blown film was obtained in the same manner as in. Then, the bag breakage rate was measured in the same manner as in Example 1. The results are shown in Table 1.

Comparative Example 3 An inflation film of 150 μm was obtained in the same manner as in Example 2 except that the radical generator was not added. Then, the bag breakage rate was measured in the same manner as in Example 2. The results are shown in Table 1.

[0042]

[Table 1]

[0043]

EFFECTS OF THE INVENTION According to the present invention, a packaging bag having improved heat-sealing strength and body strength and improved easy incineration can be obtained. This packaging bag is suitable for packaging relatively heavy contents such as rice grains and fertilizers.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tetsuya Yoshikiyo 3-10-10 Shiodotsu, Kurashiki-shi, Okayama Mitsubishi Kasei Co., Ltd. Mizushima Plant

Claims (5)

[Claims] 1. A linear low density polyethylene having a melt index of 2 g / 10 minutes or less, 100 parts by weight, a radical generator 0.0001 to 0.1 part by weight, and calcium carbonate 2.
A packaging bag formed by molding a polyethylene resin composition obtained by blending 0 to 150 parts by weight and 0.1 to 10 parts by weight of a plasticizer with 100 parts by weight in total. 2. Calcium carbonate having an average particle size of 0.5 to 6
10 carbon atoms for 100 parts by weight of μm calcium carbonate
The packaging bag according to claim 1, which is surface-treated with 0.1 to 5 parts by weight of the higher fatty acid. 3. 100 parts by weight of a linear low density polyethylene having a melt index of 2 g / 10 minutes or less, 0.0001 to 0.1 part by weight of a radical generator, and calcium carbonate 20.
To 150 parts by weight and a total of 100 parts by weight of the above-mentioned polyethylene resin composition obtained by blending 0.1 to 10 parts by weight of a plasticizer, and the resulting tubular film is crossed with respect to the take-up direction. A method for producing a packaging bag, which comprises heat-sealing and cutting in a longitudinal direction. 4. The method for producing a packaging bag according to claim 3, wherein the inflation molding conditions are a blow-up of 0.9 to 2.0, a draft rate of 10 to 40, and a cooling rate index of 30 seconds or less. 5. The heat-sealing method causes shrinkage in the heat-sealing portion by heating the heat-sealing portion at a temperature of 200 to 280 ° C. until the films are fused and then leaving the heat-sealing portion in a free state. The manufacturing method of the packaging bag according to claim 3 or 4, characterized in that.