JPH0577372A - Multi-layer stretch tape, woven fabric for flexible container and processed fabric for flexible container manufacturing - Google Patents

Abstract

(57) [Summary] [Structure] An outer layer 2 made of a heat-adhesive resin having a melting point lower than that of polypropylene used for the intermediate layer 1 is laminated on both surfaces of an intermediate layer 1 made of a mixture of polypropylene and linear low-density polyethylene. A multilayer stretched tape in which a laminate having at least a three-layer structure is stretched to have a predetermined width. Woven fabric for flexible containers woven using this yarn. A work cloth for producing a flexible container in which a protective resin layer 5 is formed on at least one surface of this woven cloth. [Effect] Since the intermediate layer 1 is formed of a mixture of PP and LLDPE, the adhesiveness with the outer layer 2 is sufficiently retained by mixing the LLDPE while maintaining the heat resistant creep characteristic tensile strength originally possessed by PP. It becomes a yarn. Further, in the work cloth for manufacturing a flexible container in which the protective resin layer is formed, there is no peeling between the intermediate layer and the outer layer of the multilayer stretched tape, so that the heat seal strength and the high welding strength can be maintained. Moreover, it is more flexible than the PP-only yarn.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a large-sized transport container for transporting powder and granular materials, a multilayer stretched tape suitable for a flexible container, and a woven fabric for a flexible container woven using this tape (hereinafter referred to as woven fabric). And a work cloth for producing a flexible container (hereinafter referred to as a work cloth) in which a protective resin is laminated thereon.

[0002]

2. Description of the Related Art A tape made of polypropylene (hereinafter abbreviated as PP) or high density polyethylene (hereinafter abbreviated as HDPE) is used for mass transportation of various resins, chemicals, agricultural chemicals or food materials. A flexible container is used in which a bag-shaped container is obtained by subjecting a woven fabric (called a yarn) to a sewing process such as sewing and heat sealing.

There is also provided a flexible container using a processed woven fabric in which a plastic protective coating is formed on the woven fabric to impart waterproofness or prevent foreign matter from entering.

[0004]

However, a woven fabric woven using PP yarns has a problem in weather resistance, and requires an inner bag depending on the type of contents.
Due to the high rigidity of the woven cloth, there were drawbacks in handling during sewing and during handling during powder filling. Also, PP
PP resin is unavoidable for the work cloth in which the protective film is formed on the woven cloth woven by the yarn, but for this reason, the handleability during sewing and the handling during filling of powder and granules are further improved. It was difficult.

On the other hand, when a yarn made of HDPE having a relatively low melting point is used, it is superior to the PP woven fabric in terms of handleability of the woven fabric at the time of sewing and formation of a protective film, but the filling content is If the temperature is higher than 60 ° C, the storage condition after filling exceeds 40 ° C, or the product is piled up in multiple stages and used for a long period of time, the yarn will be stretched and cut. There was a problem.

In order to solve these problems, Japanese Patent Application No. 62-279494 proposes a woven fabric for a flexible container made of a three-layer yarn in which a simple substance of PP is used for the intermediate layer and HDPE is laminated on both sides thereof. There is. Although this product is sufficiently satisfactory in various points such as heat-resistant creep properties, the adhesiveness between the PP of the intermediate layer and the HDPE of the outer layer is somewhat insufficient, so a flexible container using this processed cloth is recommended. If it is used for a long time at a high temperature of 40 ° C or more or repeatedly used, the layer interface between the intermediate layer and the outer layer peels off at the heat-sealing part during the bag-making process, remarkably reducing the strength of the work cloth and breaking the bag. It turned out that it is likely to occur.

Based on the above experience, the inventors of the present invention conducted a study on a yarn which, while satisfying the heat-resistant creep property, does not cause delamination from the interlayer even when it is used for a long period of time. Completed

[0008]

The yarn of the present invention is made of PP
P used for the intermediate layer on both sides of the intermediate layer made of a mixture of a linear low density polyethylene (hereinafter referred to as LLDPE)
A laminate having at least a three-layer structure in which outer layers each made of a thermo-adhesive resin having a melting point lower than P are laminated is stretched and then divided into a predetermined width, or divided into a predetermined width and then stretched.

The woven fabric for flexible containers of the present invention is woven using the yarn for at least one of warp and weft.

Further, the processed cloth of the present invention is one in which a protective resin layer is formed on at least one surface of the woven cloth.

The present invention will be described below with reference to the drawings. FIG. 1 shows a cross section of a yarn according to the present invention. In the figure, reference numeral 1 is an intermediate layer, and 2 is an outer layer formed on both surfaces of the intermediate layer 1, respectively. The intermediate layer 1 is a mixture of PP and LLDPE, and the mixture can improve the adhesiveness with the outer layers formed on both surfaces.

The mixing ratio of PP and LLDPE forming the intermediate layer 1 is 50 to 90 parts by weight of PP, and LLDPE is 50 to 90 parts by weight.
The amount of PP is preferably 10 to 50 parts by weight, and when the proportion of PP exceeds 90 parts, the properties of the yarn are close to those of the PP yarn, resulting in poor flexibility of the yarn, the yarn becomes hard, and the adhesiveness with the outer layer 2 becomes low. Get scarce. On the other hand, LLDPE
When the ratio is large, a yarn having good adhesion to the outer layer 2 is obtained, but the strength of the yarn itself is insufficient, and the heat-resistant creep property of the obtained woven fabric is deteriorated.

The outer layer 2 is made of HDPE, LLDPE alone or a mixture thereof, or the above HDPE or LLD.
It is preferably formed of a mixed resin in which PE is mixed with another polyolefin resin. When the mixed resin is used, the mixing ratio is preferably, for example, about 40 to 1 part by weight of another resin with respect to 60 to 99 parts by weight of HDPE, and the mixing can improve the adhesiveness with the intermediate layer 1. It is possible to effectively prevent yarn cutting and yarn splitting during weaving of a woven fabric for flexible containers. Also, by mixing HDPE and LLDPE,
It is possible to improve the adhesion between the flexible container woven fabric 4 woven using this yarn and the protective layer 5 described later.

The thickness ratio of the intermediate layer 1 and the outer layer 2 is determined by the mechanical strength of the obtained yarn. The intermediate layer 1 is 50 to 90%, and the outer layer 2 is 10 to 5%.
The ratio is set to 0%. That is, when the obtained yarn has 2000 denier, the intermediate layer 1 has 1
000-1800 denier, outer layer 2 200-1000
It is preferable to determine the intermediate layer 1 and the outer layer 2 so as to have a denier. When the ratio of the intermediate layer 1 is large, the heat-resistant creep property is good, but the adhesive state between the intermediate layer 1 and the outer layer 2 is lowered, and the joint strength of the heat-sealed portion of the work cloth is lowered. On the other hand, when the ratio of the intermediate layer 1 is small, the adhesion between the intermediate layer 1 and the outer layer 2 is good, but the heat-resistant creep property is deteriorated, and the mechanical strength of the woven cloth or the processed cloth tends to be decreased.

As a method for producing this yarn, a film to be the intermediate layer 1 and a film to be the outer layer 2 are respectively formed, and these are adhered and laminated with an isocyanate adhesive or the like, or the intermediate layer 1 HDPE on both sides of
Although the outer layer 2 may be formed by extrusion coating, each resin is made into three layers by a coextrusion method using a known device such as inflation and T-die so that the outer layer 2 is formed on both sides of the intermediate layer 1. When the film is formed and stretched with the constitution, the adhesiveness between the intermediate layer 1 and the outer layer 2 can be sufficiently secured, and the manufacturing cost is cheaper and more advantageous than the former.

The fineness of the yarn is determined in consideration of the mechanical strength required for the woven fabric 4 which will be described later, but is generally 1000 to 3000 denier in view of the productivity of the yarn. Range, preferably 1500
It is about 2,500 denier. The width of the yarn is 3 to 1 in relation to the weave density of the woven fabric 4 described later.
It is set to about 2 mm, preferably 6 to 10 mm.

FIG. 2 shows a flexible container woven fabric 4 woven using the yarn of the present invention.
The woven cloth 4 may be made by using the yarn of the present invention for at least one of the warp and the weft, but in general, the woven cloth 4 obtained is obtained.
Considering the strength balance of the above, it is preferable to use it for both the circumstances. Although various methods such as plain weave, twill weave, and satin weave can be used for weaving the woven cloth 4, it is preferable to use a plain weave which is economically advantageous in consideration of the strength balance of the warp and weft.

The weaving density of the woven cloth 4 varies depending on the size of the flexible container to be manufactured, the weight of the contents, and the size of the powder or granules of the contents, but in general, it is 1 inch (25. It is preferable that the number is about 10 to 20 per 4 mm). However, you are not bound by this.

In the woven cloth 4, it is possible to use yarns having different fineness depending on the warp and weft, but in general, from the viewpoint of the balance of the mechanical strength of the woven cloth 4, the denier yarn with the same warp and weft is used to weave. It is preferable that the densities are substantially the same.

FIG. 3 shows a woven fabric 4 obtained as described above.
3 shows a cross section of a work cloth obtained by laminating the protective resin layer 5 on both surfaces of the work cloth.

The protective resin layer 5 has the purpose of preventing foreign matter such as dust from entering from the outside and preventing the contents from being contaminated due to the permeation of water into the inside, and also the woven cloth 4
Are laminated to reinforce the mechanical strength of the woven fabric 4, for example, the friction resistance against the ground surface or the concrete surface. Generally, the synthetic resin is melt-extruded on at least one surface of the woven cloth 4.

As the synthetic resin forming the protective resin layer 5, polyethylene or ethylene-vinyl acetate copolymer having various densities, polyethylene copolymer resin such as ionomer, PP, etc. may be used alone or in combination. good. A plurality of layers made of these synthetic resins may be laminated. In order not to reduce the mechanical strength of the woven cloth 4, it is desirable to form the protective resin layer 5 using low density polyethylene LLDPE or ethylene-vinyl acetate copolymer resin that can be extruded at a relatively low temperature. Although the thickness of the protective resin layer 5 is not particularly limited, it is generally preferable to set the thickness to about 40 to 100 μm.

The yarn of the present invention is made of PP and LLDP.
P used for the intermediate layer on both sides of the intermediate layer consisting of the mixture of E
It has at least a three-layer structure in which outer layers made of a heat-adhesive resin having a melting point lower than P are respectively laminated, but a case in which two or more layers having the three-layer structure are stacked is also included in the scope of the present invention. Of course. As a method for producing a yarn in which two or more layers each having a three-layer structure are stacked, for example, a film having a three-layer structure is extruded into a tubular shape by a coextrusion method using an inflation device as described above, and this is crushed. There is a way. The yarn produced in this way has an outer layer located inside the two three-layer constructions, which is also within the scope of the present invention.

[0024]

The yarn of the present invention comprises the intermediate layer 1 made of a mixture of PP and LLDPE, and the outer layer 2 made of a heat-adhesive resin having a melting point lower than that of PP used on both sides thereof. It is also possible to form a woven fabric 4 having improved adhesive strength and excellent creep resistance. Further, the adhesion with the protective resin layer 5 is possible at a lower temperature than the case where PP is used as the protective layer, and the adhesion is also good.

[0025]

【Example】

(Example 1) Polypropylene homopolymer having a density of 0.90 g / cm ³ and a melt flow index of 12 g / 10 min (Showa Denko KK: Shiyo Aroma PY02)
Is a linear low-density polyethylene having a density of 0.918 g / cm ³ and a melt flow index of 0.80 g / 10 min (manufactured by Showa Denko K.K.
08F) was mixed at a ratio of 7: 3 to prepare a mixed resin as a material for forming the intermediate layer 1. On the other hand, as a material for forming the outer layer 2, a high density polyethylene having a density of 0.952 g / cm ³ and a melt flow index of 0.80 g / 10 min (manufactured by Showa Denko KK: SHYO-REX HY0).
1) was prepared. These materials were extrusion-molded by the inflation method so that the thickness of the intermediate layer and the outer layer was 20/60/20 to prepare a three-layer coextruded film. Then, slit this into a width of 22 mm, and then 100 ℃
Was drawn at a temperature of about 7.5 times to obtain a multilayer drawn yarn having a width of 8.5 mm. The properties of this yarn are shown in Table 1.

Comparative Example 1 The polypropylene homopolymer used in Example 1 was prepared as a material for the intermediate layer. The high-density polyethylene used in Example 1 was prepared as a material for the outer layer. These were molded in the same manner as in Example 1 by the inflation method so that the thickness ratio was 20/60/20 to prepare a three-layer coextruded film. Then, this film was slit-stretched under the same conditions as in Example 1 to obtain a yarn. The properties of this yarn are also shown in Table 1.

(Test) Tensile strength of the yarn of Example 1 and the yarn of Comparative Example 1 obtained as described above,
The tensile elongation and the interlayer-outer layer adhesive strength were examined. The results are shown in Table 1.

[Table 1]

As can be seen from the results in Table 1, the yarn of Example 1 in which the intermediate layer 1 was formed of the resin in which LLDPE was mixed was compared with the yarn of Comparative Example 1 in which LLDPE was not mixed, and the intermediate layer 1 and the outer layer 2 were It can be seen that the adhesive strength with is sufficient.

(Example 2) The yarn obtained in Example 1 was woven on a loom to have a warp of 14.5 yarns / inch and a weft of 14.5 yarns / inch.
An inch plain weave woven fabric 4 was produced. (Comparative Example 2) Using the yarn of Comparative Example 1, a plain woven fabric having a warp of 14.5 yarns / inch and a weft of 14.5 yarns / inch was produced in the same manner as in Example 2.

The characteristic values of these woven fabrics are shown in Table 2.

[Table 2]

As can be seen from the results shown in Table 2, the woven fabric 4 of Example 2 using the yarn of Example 1 is excellent in mechanical strength such as tensile strength and has an excellent appearance for a flexible container and is extremely useful. I understand.

Example 3 A protective resin layer 5 having a density of 0.916 g / cm 2 is formed on both sides of the woven fabric 4 obtained in Example 2.
³ , LLDP with melt flow index 6g / 10min
E (Showa Denko KK: SHOREX LINEAR 107L
-A) was laminated by the extrusion laminating method so as to have a thickness of 60 μm, to prepare a work cloth. Comparative Example 3 A protective resin layer 5 made of the same material as in Example 3 and having a thickness of 60 μm was formed on both surfaces of the woven fabric obtained in Comparative Example 2 by melt extrusion.

The characteristic values of the work cloth thus obtained are shown in Table 3.

[0034]

[Table 3]

In Table 3, the methods for measuring the peel strength of the welded portion, the shear strength of the welded portion, the residual strength of the original fabric portion, and the residual strength of the welded portion shear strength are as follows.

Peeling strength of welded portion Two work cloths each having a width of about 30 cm are overlapped, and the end portion thereof is
A sample was obtained by hot-pressing under a condition of 320 ° C. and 2 Kg / cm ² over 30 mm and cutting into a width of 30 mm. Then,
The end portion of the sample was fixed to each chuck by an Instron type tensile tester and peeled by 180 degrees at a gripping interval of 50 mm and a pulling speed of 50 mm / min to obtain a welded portion peel strength.

Shear strength of welded portion Two work cloths having a width of about 30 cm are alternately stacked, and the overlapped portion is spread over 40 mm at 320 ° C. and 2 Kg / cm.
^Under the conditions of ² , hot air pressure bonding was performed, and the sample was cut into a width of 30 mm. Then, using an Instron type tensile tester, the end of the sample was fixed to each chuck, and the gripping interval 15
It was pulled up and down at 0 mm and a pulling speed of 200 mm / min to obtain the welded portion shear strength.

Residual strength of original fabric portion A work cloth having a width of 30 mm was used as a sample, and the end portion of the sample was fixed to each chuck by an Instron type tensile tester, and the gripping interval was 150 mm and the pulling speed was 200 mm / min. The tensile strength and the breaking strength were A. On the other hand, a similar sample with a weight of 62 kg lowered was placed in an atmosphere of 60 ° C for 72
The sample was allowed to stand for a period of time, and then the breaking strength of this sample was measured under the same conditions as the above sample, which was designated as breaking strength B. And B
/ A × 100 was defined as the strength residual ratio of the original fabric portion.

Residual rate of shear strength of welded portion A sample having the same shear strength as that of the welded portion was prepared, and this sample was left under the condition of a weight of 35 kg lowered at 30 ° C. for 48 hours and then at 40 ° C. for 24 hours. did. Then, the shear strength of the welded portion of this sample was measured. The welding portion shear strength B thus measured and the welding portion shear strength A measured without applying the above-mentioned load, B / A × 100 was taken as the welding portion shear strength residual rate.

Looking at the column of the peel strength of the welded portion in Table 3, the processed cloth of Example 3 showed a better adhesion state between the protective resin layer 5 and the woven cloth 4 than that of Comparative Example 3. It is found that the heat-resistant creep property is good.

[0041]

As described above, the yarn of the present invention comprises an intermediate layer made of a mixed resin of PP and LLDPE and an outer layer made of a heat-adhesive resin such as HDPE having a melting point lower than that of polypropylene used for the intermediate layer. Since the yarn has a three-layer structure, the yarn retains the heat-resistant creep property and tensile strength originally possessed by PP and also has sufficient adhesiveness with the outer layer by mixing with LLDPE. Moreover, PP
It is also more flexible than chisel yarn.

Further, the woven fabric of the present invention woven using this yarn has sufficient mechanical strength as a woven fabric for flexible containers.

Further, since the yarn of the present invention uses a heat-adhesive resin such as HDPE having good adhesiveness in the outer layer, the woven fabric made of this yarn has a protective resin such as LLDPE and ethylene-vinyl acetate copolymer resin. The processed cloth for producing a flexible container of the present invention in which the above are laminated can sufficiently secure the adhesiveness between the protective resin layer and the woven cloth.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an example of a multilayer stretched tape (yarn) of the present invention.

FIG. 2 is a plan view showing an embodiment of the woven fabric of the present invention.

FIG. 3 is a sectional view showing a work cloth of the present invention.

[Explanation of symbols]

 1 Middle Layer 2 Outer Layer 4 Woven Fabric 5 Protective Resin Layer

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical display location D06M 15/227 7199-3B (72) Inventor Ikuo Nagaya 1-3-3 Nihonbashi-Horidomecho, Chuo-ku, Tokyo 15 Heisei Polymer Co., Ltd. (72) Inventor Shiro Yamamoto 1-4-16 Nihonbashi Bakurocho, Chuo-ku, Tokyo Fujimori Kogyo Co., Ltd. (72) Inventor Toshiyuki Takeda 1-4-16 Nihonbashi Bakuro-cho, Chuo-ku, Tokyo Fujimori Kogyo Co., Ltd. (72) Inventor Shinichiro Yoshiba 1-4-1 Nihonbashi Bakurocho, Chuo-ku, Tokyo Fujimori Kogyo Co., Ltd.

Claims (5)

[Claims] 1. A laminate having at least three layers in which an outer layer made of a heat-adhesive resin having a melting point lower than that of polypropylene used for the intermediate layer is laminated on both sides of an intermediate layer made of a mixture of polypropylene and linear low-density polyethylene. Is a multi-layer stretched tape having a predetermined width. 2. The mixing ratio of polypropylene and linear low-density polyethylene of the mixture forming the intermediate layer is 10 to 50 parts by weight of linear low-density polyethylene to 50 to 90 parts by weight of polypropylene. 1. Multi-layer stretch tape. 3. The multilayer stretch according to claim 1, wherein the heat-adhesive resin is high-density polyethylene, linear low-density polyethylene alone or a mixture thereof, or a mixture of these resins with a polyolefin resin. tape. 4. A woven fabric for a flexible container produced by weaving the multilayer stretched tape according to claim 1 for at least one of warp and weft. 5. A work cloth for producing a flexible container, wherein a protective resin layer is formed on at least one surface of the woven cloth for a flexible container according to claim 4.