JPS587347A - Bag for packing and its manufacture - 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 packaging bag and a method for manufacturing the same, and more particularly to a packaging bag that is strong, has low blocking properties, is suitable for automatic packaging, and has excellent impact resistance at low temperatures. and its manufacturing method. Traditionally, low-density polyethylene, which has excellent sealing strength, has been widely used as packaging bags for various heavy items such as granular items such as rice and wheat, powdered items such as fertilizer, and angular solid items such as broilers. There is. However, low-density polyethylene has low mechanical strength, so thick-walled materials must be used.Especially when used as packaging bags for heavy items, the tensile strength and rigidity are significantly inferior, so extremely thick-walled materials must be used. It's necessary
b. There were various limitations in terms of usage. Furthermore, this low-density polyethylene is not suitable for use as bags for automatic packaging due to its weak elasticity, which poses a practical problem. Therefore, in recent years, bags made of a laminated film of high-density polyethylene and low-density polyethylene, which do not have the above-mentioned drawbacks of low-density polyethylene, have been developed (Japanese Patent Application No. 5'1-1, 9'133, Gansho!;!;-10da3gO, JP-A-3!;-3θq9'l). Here Tokugan Sho S Da / 69 da 33 and Tokugan Sho! ;5-
Bags using the film disclosed in IO'13g0 are
It has high seal strength and film impact strength, has a good balance of tear strength, and has a non-smooth outer layer, making it extremely desirable in practical terms.However, when storing and transporting angular and heavy objects such as broilers,
Tear strength. There are problems with impact resistance and strength at low temperatures. Tokukai Akira again! ;! The bag using the film disclosed in -3099 da has an inner layer of low-density polyethylene, which tends to cause blocking, and there is a problem with opening properties, and at the same time, the inside of the bag is difficult to slip, making it difficult to store items. There is a big drawback. Therefore, the present inventors overcame the drawbacks of the above-mentioned prior art, and
We conducted extensive research to develop a packaging bag that has various advantages and is extremely suitable for practical use, as well as a method for manufacturing the same. As a result, they discovered that the desired bag could be obtained by constructing a bag with two layers, an outer layer and an inner layer, and simultaneously forming each layer with a certain amount of Silertic film.They also bonded the two layers together in a die and performed inflation. It has been found that the above-mentioned bag can be efficiently produced by coextrusion and molding at a specific blow ratio. The present invention was completed based on this knowledge. That is, the present invention is characterized in that the outer layer is made of low-density polyethylene or a mixture of low-density polyethylene and an ethylene-vinyl acetate copolymer, and the inner layer is made of a mixture of high-density polyethylene and an ethylene-zolopyrene copolymer elastomer. In addition, there is provided a method for producing a packaging bag, characterized in that the outer layer and the inner layer are bonded together in a die and molded by inflation coextrusion, blow ratio, and S-g. It is something to do. The bag of the present invention, as shown in FIG. 1, is formed from two layers of film. As already mentioned, the outer layer 1 is made of low density polyethylene or low density polyethylene and ethylene-2.
It consists of a mixture with vinyl acetate copolymer. There are various types of low density polyethylene (LDPE), but preferably melt index (MI) is 0.3.
-/ 09/ / 0 minutes. A material with a density in the range of 0.9/7-0.9351/crL3 is used. If the MI exceeds 109//0 minutes, the 1J impact resistance will decrease and it will be impractical; on the other hand, if the MI exceeds 0.
If it becomes smaller by 39 /IO, there will be a problem in moldability. Regarding MI of LDPR, especially 0.3-'II/1
A value of 0 minutes is optimal. The above LDPE may be high pressure LDpE + low pressure LDPE, and low pressure LDPE is a combination of ethylene and α-olefin having 3 to 72 carbon atoms (e.g. propylene, butene-7, etc.). Polymers can also be used. The outer layer 1 in the bag of the present invention may be formed of only the above-mentioned LDPE, but it may also be formed of a mixture of this LDPE and ethylene-vinyl acetate copolymer # (EVA). When using a mixture of LDPE and EVA in this way,
The mixing ratio is not particularly limited, but usually LDPE/E
vA=10/qO-qS/S (weight ratio), preferably 60/1IO-90/10 (weight ratio). If the amount of EVA is too large, the bags will have an acetic acid odor, and at the same time, the surface will be too non-slip, causing blocking between the bags, and the belts of rollers and belt conveyors used for automatic packaging. It is undesirable because it will get stuck in the transport equipment such as the above and the work efficiency will be significantly deteriorated. It is made of a mixture of copolymer and elastomer. Here, high density polyethylene (HDPE) has various types, but usually MI 0.0 /-/, 09/ /
0 minutes. A material with a density of 0.9'I O-0,9709/cm3 is used, preferably MI O,02-0,2g/cm3.
/ 0 minutes should be used. MI is 7.09/
If the heating time exceeds 10 minutes, mechanical strength such as tensile strength of the film decreases, which is not preferable. On the other hand, there are various ethylene-progylene copolymer elastomers (Ep), but ethylene-progylene copolymer and ethylene-progylene terpolymer are preferred, and Mooney viscosity is 170-/! ;0 is preferred. If the Mooney viscosity is less than 0, the mechanical strength of the film will decrease, which is not preferable. The mixing ratio of the mixture of I (DPE and EP that forms the inner layer 2 of the bag of the present invention is not particularly limited as long as it can be adjusted as appropriate depending on the purpose of use of the bag, etc., but usually HDP'E/EP= 9
! ;/3-30/! ; QC weight ratio), preferably 90/
It should be selected within the range of 10-roO/daO (weight ratio). If the EP content is less than 5% by weight, the puncture strength and sealing strength of the film will decrease, and the film will be more likely to tear when the bag is dropped. On the other hand, if it exceeds 50% by weight, the molding workability is poor and the bag obtained also has a weak stiffness, which is not preferable. The bag of the present invention is composed of the above-mentioned outer layer 1 and inner layer 2, more specifically, a film forming the outer layer 1 and a film forming the inner layer 2 are laminated. Here, the thickness ratio of both layers may be determined as appropriate depending on the purpose of the bag, but usually outer layer/inner layer = //q9-A O/'I
Defined within the range of O. If the thickness of the outer layer exceeds 60% of the total thickness of both layers, the tensile strength and rigidity of the bag will be undesirably low, and if it is less than 7%, the molding operation will be difficult. The bag of the present invention, which has an outer layer and an inner layer as described above, can be manufactured by various methods, but according to the method of the present invention described above, a packaging bag with better physical properties can be efficiently manufactured. be able to. That is, according to the method of the present invention, first, the raw material resins for the outer layer and inner layer are melt-kneaded and extruded using an extruder at a normal molding temperature, and then introduced into a two-layer circular die. Both layers were bonded in the die with a blow ratio of 2. ! ;-g
, preferably inflation molding in steps 3-6. Here, the outer layer and the inner layer may be bonded by either in-die adhesion or out-of-die adhesion, but in-die adhesion is preferable because the bonding strength between the two layers is greater. In addition, when manufacturing the bag of the present invention, pigments and slip agents are used. Additives such as antioxidants, antistatic agents, and weathering agents may be added to one or both of the outer layer and the inner layer at any stage of molding, if necessary. The bag of the present invention having the structure as described above has extremely superior film puncture strength, tear strength, etc., as well as sealing strength and low-temperature impact strength compared to conventional bags. Therefore, it is sufficiently durable for storing and transporting heavy objects, especially angular heavy objects such as broilers. Furthermore, the bag of the present invention has low blocking properties and is strong, so it is suitable for automatic packaging and has very high packaging workability. Moreover, since the bag has high mechanical strength, the wall thickness of the bag is l・θμ.
A thickness of about 200 μm is sufficient, and the film can be made thinner, which is also economically advantageous. Although the bag of the present invention has the above-mentioned excellent properties, if it is manufactured by the method of the present invention described above, a bag with even better physical properties can be obtained. Next, the present invention will be explained in more detail with reference to Examples and Comparative Examples. Example/-/6' After uniformly mixing the specified raw material resins for forming the outer layer and the inner layer at the compounding ratio shown in Table 1, they were melted and kneaded using respective extruders. , then introduced into an in-die adhesive type circular die, and then subjected to inflation molding at a blow ratio of 3, so that the wall thickness ratio of the outer layer and the inner layer was /: lI
A cylindrical two-layer film having a thickness of gθμ was obtained, and from this film a bag having a width of SOO and a length of 620 mm was heat-sealed at one end. Various physical property tests were conducted using the small bag. Results first
Shown in the table. The physical property tests were conducted as follows. Impact strength: Measured using a film impact tester (manufactured by Toyo Seiki Co., Ltd., standard impact amount 30:9, impact diameter/inch). Puncture strength: Based on rIs-z-g'lO/. Tear strength: Based on JIS-p-g//b. Tensile modulus: Based on JIS-Z-/702. Tensile strength: Based on JIS-Z-/RI02. Elongation: Based on JIS-Z-/702. Seal strength: Based on ASTM-D-/g2:). Practical drop test: Fill a bag with 20 kg of chemical fertilizer and drop it from a height of 2.5 tn onto a concrete floor with the bag surface horizontal to measure the bag breakage rate (number of broken bags/number of dropped bags). did. Formability: Continuous operation during forming a two-layer film by the inflation method was observed and evaluated as follows. ◎..."Excellent", i.e., capable of continuous stable operation for over / week ○..."Good", i.e., capable of continuous operation for /-6 days △..."Good", i.e., capable of continuous operation for 3 hours Appearance : Visually evaluate. ○: Indicates good condition. Blocking: After the film was made into a bag, evaluation was made based on whether or not the inner surfaces of the film were in close contact with each other when the bag was opened. ◎・・・Items that can be opened easily. △: Slightly difficult to open. Comparative Example/2 A bag was obtained in the same manner as in Example 1 except that the inner layer was made of only HDPE, and a physical property test was conducted. The results are shown in Table 1. Comparative Example 3 Commercially available low density polyethylene for general heavy bags (density 0.92
A f! /23. The same physical property test as in Example 1 was conducted using a film having a thickness/gθμ of MI 0.119//0 min). The results are shown in Table 1. Comparative Example q Commercially available low density polyethylene for general heavy bags (density 0.92.
b 9 /cIrL3. MI O,lIg/ / 0
Physical property tests similar to those in Example 1 were conducted using a film having a thickness gθμ of The results are shown in Table 1. Example/7 The bag of Example 3 filled with 20 kg of chemical fertilizer, -
After being left in a room at 20°C for a day and night, a practical drop test was conducted to determine the bag breakage rate. The results are shown in Table 2. Example/g The bag of Example DA was filled with 20 parts of chemical fertilizer 9, -
After being left in a room at 20°C for a day and night, a practical drop test was conducted to determine the bag breakage rate. The results are shown in Table 2. Comparative Example S The bag of Comparative Example 2 was filled with 20% of chemical fertilizer 9, -
After being left in a room at 20°C for a day and night, a practical drop test was conducted to determine the bag breakage rate. The results are shown in Table 2. Comparative Example 6 Comparative Example 30 bags filled with 20 to 9 of chemical fertilizer, -
After being left in a room at 20°C for a day and night, a practical drop test was conducted to determine the bag breakage rate. The results are shown in Table 2. Comparative Example 7 The bag of Comparative Example q was filled with compound fertilizer 20 and 9, -
After being left in a room at 20°C for a day and night, a practical drop test was conducted to determine the bag breakage rate. The results are shown in Table 2. (*1) A is density 0.934'I/cIrL3
．． Mr 39//0 minute high pressure LDPE (*2) B has a density of 0.92 bl/7cm3.
MI'III/10 minute high pressure method I, DPE ($3) C has a density of 0.92/g/m3. Mr.
O,1,,! i' / / 0 minute high pressure LDPE (*4) D is density 0.9/7g/cm3. MIgg
/10 minutes high pressure LDPE (*5) E is density 0.92 Kel/ /cm', MI
311/ / 0 minute high pressure LDPE (*6) F is density 0.9.2/l! /crII
3. Low pressure process LDPK with Mx 3.7 g//0 min, α-olefin content of C8/0-3 wt%. ($7) G is density o, q da El 7cm3. Ml
O, b F! ／ ／ 0 minutes. Gynyl acetate content/3 vrt% EVA (*8)
H has a density of 0-9! ; Q-g/an3. MI O, O
，! ; g/10 min I (DPE (*9) I is Mooney viscosity ML1+4 (/ 00
°c>bo, ethylene-propylene copolymer (*10) with a propylene content of yc>bo, J is Mooney viscosity ML1+4 (1000C
) 90, 7'ropylene content 2 g wt% ethylene-zo'pyrene terpolymer (*11)
)/O3t propylene content qJwt, % ethylene-
Norogi sinter polymer ($12) L HaA -=-viscosityIf ML1+4(/
000c) 4' 2, Norogi Shin included i'13wt,
% ethylene-propylene terpolymer

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing one embodiment of the bag of the present invention. 1...Outer layer, 2...Inner layer, 3...Sealing part. Procedural amendment (voluntary) August 11, 1980 Director General of the Patent Office Kazuo Wakasugi - Case O Medal of Honor 1854-104828 1. Name of the invention A pouch for pith and its manufacturing method 1 Person making the amendment Relationship to the case Patent Applicant Dezaki Ishibei Kagaku Co., Ltd. Kinsha 4 Agent Address: 1-1-10 Kyobashi, Chuo-ku, Tokyo 104 Column for detailed explanation of the invention in the subject specification of liquid stopping Amendment O Contents " as a third component: dienes (divinylbendane, 1,4-hequinadiene, 5-ethylidene-2-norpornene, 5-methylene-2-norporene, dicyclopentadiene, cyclootatadiene, etc.) ) is copolymerized and corrected to ``9 ethysine psylbillentageli!-''. (2) “From 1-P-8114J” on page 11, line 11
amended to ": JXm-M-1702J. aIlil Page 15 Table 1 0 Example 140 X, DIM
Correct the entry in Column O from "-" to "Mu?OJ." (2) Column O of Example 16 in Table 1 of the 15th Summer
Correct the writing from [e”1ooJ to “G’lOJ.” (That’s all)

Claims (1)

[Claims] 1. The outer layer is made of low-density polyethylene or a mixture of low-density polyethylene and an ethylene-vinyl acetate copolymer, and the inner layer is made of a mixture of high-density polyethylene and an ethylene-zologylene copolymer distoner. A packaging bag characterized by comprising: 2. Low density polyethylene has a melt index of 0.3-
101//10 minutes, density 0.9/7-θ, 935g/
The packaging bag according to claim 1, which is crrL3. 3. Claim 1, wherein the low-density polyethylene is a copolymer of ethylene and an α-olefin having a3−/2 carbon atoms.
Packaging bag as described in section. 4. High-density polyethylene has a melt index of 0.0/
-10fi/10min, density 0.9'1.0-0.9
? The packaging bag according to claim 1, which is Og/α3. 5. The packaging bag according to claim 1, wherein the ethylene-propylene copolymer distomer is an ethylene-propylene terpolymer. 6. The mixing ratio of the mixture of high-density 11 polyethylene and ethylene-propylene copolymer elastomer is:
The latter = 95-! ;0:5-30 (weight ratio) The packaging bag according to claim 7. 7. The wall thickness ratio between the inner layer and the outer layer is inner layer:outer layer=qq-tt. :/-60. The packaging bag according to claim 1. 8. An outer layer made of low-density polyethylene or a mixture of low-density polyethylene and an ethylene-vinyl acetate copolymer and an inner layer made of a mixture of high-density polyethylene and an ethylene-propylene copolymer elastomer are bonded inside the gou and subjected to inflation. Coextrusion, blow ratio 2
．． ! ; - A method for manufacturing a packaging bag, characterized by forming it in g.