JP3113589B2 - Laminated sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a method for forming a resin coating layer having good sealing properties at low temperatures and excellent peel strength and breaking strength on both surfaces of a woven fabric in which drawn yarns made of a thermoplastic resin are woven. The present invention relates to a laminate sheet obtained by the above method, and is particularly effective for a raw material of a large transport bag or a flexible container used for transporting various kinds of powders such as synthetic resin pellets, chemicals, cereals, feed, and minerals. It relates to a laminate sheet.

[0002]

2. Description of the Related Art Conventionally, as a flexible container,
A bag made of soft tarpaulin with a coating layer formed of polyvinyl chloride resin or rubber on the surface of a woven fabric made of synthetic resin fibers such as polyester and polyamide, and other fibers is used. I was The polyvinyl chloride resin used as the coating layer contains a large amount of plasticizer for the purpose of improving thermal stability, flexibility, etc., so that the liquid component elutes (bleeds) and migrates to the content filling. Problems, such as hygiene, handling, and safety, due to the fact that the resin itself has a high specific gravity and is inferior in workability, and toxic hydrogen chloride gas is generated during combustion. Have been.

Therefore, recently, an ethylene-vinyl acetate copolymer has been used instead of the polyvinyl chloride resin. Although this resin is relatively lightweight and excellent in safety, it has problems in that it is inferior in heat resistance, durability and abrasion resistance and has an odor.

[0004] As an easily moldable, lightweight and inexpensive material, there has been proposed a base material in which the surface of a woven fabric made of a polyolefin fiber such as polypropylene or high density polyethylene is coated with a low melting point polyolefin resin. There is an inconvenience that the base material is liable to undergo shrinkage deformation and strength reduction during the fusion processing, and that the fusion strength and the peel strength of the sealing portion are not sufficiently exhibited.

[0005] Therefore, a resin composition to be a coating layer is characteristic, and a specific ethylene-α-olefin copolymer is used as a raw material for a flexible container having improved heat resistance and abrasion resistance. (Japanese Unexamined Patent Publication No.
As a tarpaulin suitable for a flexible container substrate having improved heat resistance and weldability, a cloth obtained by kneading a composition obtained by kneading an olefin polymer with a specific ethylene-vinyl acetate copolymer is used.
(JP-A-5-104683), a woven cloth made of synthetic resin flat yarn is coated with a resin mainly composed of linear low-density polyethylene as a polyethylene cloth suitable for a flexible container substrate having improved seal strength. What
(Japanese Utility Model Publication No. 4-32273).

In addition, a multifilament made of isotactic polypropylene is used as a tarpaulin suitable for a flexible container substrate having improved fusibility as a characteristic feature of the structure of the woven fabric and the yarn used. (JP-A-59-224341), a flexible container base material having improved durability, flexibility and creep resistance, polypropylene as a core layer, outer layer (Japanese Unexamined Patent Publication No. 1-124649) in which a resin layer is laminated on a woven fabric made of a multilayer tape in which high-density polyethylene is disposed.

[0007]

However, none of these laminate sheets satisfies various properties such as tensile strength, fusion strength, peel strength, heat resistance and the like as a raw material for flexible containers. The method of forming the cloth, the method of coating the resin, the method of making the bag, and the like are complicated and the productivity is often deteriorated, and further improvement has been demanded.

The present invention solves the above-mentioned drawbacks of the prior art, and is particularly useful as a raw material for a flexible container which can be bag-formed by a heat fusion method, is lightweight and robust, and can be manufactured at low cost. An object is to provide an effective laminate sheet.

[0009]

Means for Solving the Problems The present inventors can solve the above problems by coating a base material, which is a woven fabric of a thermoplastic resin yarn, with a laminate resin having a specific property. And completed the invention.

That is, the laminate sheet of the present invention
A laminate sheet having a resin coating layer formed on both sides of a woven fabric woven from a drawn yarn made of polypropylene as a base material, wherein the coating layer has a syndiotactic pentad fraction of 0.7 or more. It is characterized by being.

Further, in a laminate sheet having a woven fabric woven from a drawn yarn made of polypropylene as a base material and a resin coating layer formed on both surfaces thereof, the coating layer may have: A) a syndiotactic pentad fraction A syndiotactic polypropylene of not less than 0.7 to 5 to 5% by weight; and B) a propylene-ethylene copolymer having an ethylene content of 1 to 10% by weight. .

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, a laminating resin used as a coating layer of a laminate sheet includes:
It is a syndiotactic polypropylene having a syndiotactic pentad fraction of at least 0.7, preferably at least 0.8, as measured by ¹³ C-NMR.

If the syndiotactic pentad fraction of the syndiotactic polypropylene is less than 0.7, the low-temperature sealability at the time of heat-sealing, the seal strength and the impact strength of the heat-sealed portion are not sufficient.

A method for producing this syndiotactic polypropylene is described in, for example, JP-A-2-41303.
JP, JP-A-2-41305, JP-A-2-27
No. 4703, JP-A-2-274704, JP-A-3-179005, JP-A-3-179006, etc. can be obtained by polymerizing propylene by using a metallocene catalyst or the like. . This metallocene catalyst is a catalyst composed of a metallocene compound having an asymmetrical ligand represented by, for example, isopropyl (fluorenyl) (cyclopentadienyl) zirconium dichloride, and methylaluminoxane (MAO) as a cocatalyst. .

The above-mentioned syndiotactic polypropylene is preferably a propylene homopolymer, but an α-olefin other than propylene, for example, ethylene, butene-1, 4-methylpentene-1 or the like is used in an amount of 10% by weight or less. Copolymers may be used.

The MFR of the syndiotactic polypropylene is preferably selected in the range of 1 to 30 g / 10 min., More preferably 5 to 20 g / 10 min.

[0017] The coating layer of the laminate sheet of the present invention further comprises a propylene-ethylene copolymer having an ethylene content of 1 to 10% by weight with respect to the syndiotactic polypropylene, so that the low-temperature sealability and peelability can be further improved. A laminate sheet having excellent strength and breaking strength can be obtained.

The propylene-ethylene copolymer is a propylene-ethylene copolymer produced by a known method, and either a block or random copolymer is used. The ethylene content of this copolymer is from 1 to 10% by weight, preferably from 4 to 7% by weight. Among these propylene-ethylene copolymers, a random copolymer having a low melting point is preferred.

MF of the above propylene-ethylene copolymer
R is preferably selected in the range of 1 to 30 g / 10 min., More preferably 5 to 20 g / 10 min.

It is also possible to mix a polyolefin resin other than the propylene-ethylene copolymer without departing from the spirit of the present invention.

When a propylene-ethylene copolymer is used in combination with syndiotactic polypropylene, the blending ratio of the propylene-ethylene copolymer to be blended is 5 to 5.
It is 95% by weight, preferably 10 to 90% by weight. If the blending ratio of the propylene-ethylene copolymer exceeds 95% by weight, the properties of syndiotactic polypropylene cannot be utilized, and the low-temperature sealability, peel strength, and breaking strength are insufficiently improved. The bonding strength becomes insufficient.

As a method of mixing the syndiotactic polypropylene and the propylene-ethylene copolymer, a dry blend of pellets may be used. However, a predetermined amount of a single-screw or twin-screw extruder, a Banbury mixer,
Those kneaded with a kneader or the like are preferred.

The base material of the laminate sheet of the present invention is a woven fabric in which drawn yarns made of a thermoplastic resin are woven.

The yarn constituting the base material has high strength as a fiber shape, has little deterioration during weaving,
Multifilaments, monofilaments, flat monofilaments, flat yarns, etc. are not particularly limited as long as weaving efficiency is good, but multifilaments are liable to break single yarns during weaving and are inferior in handleability. However, there is a problem that the cross-sectional diameter is large, the thickness of the woven fabric is large, and the flexibility is lacking, and flat monofilaments and flat yarns having this point are suitably used.

The thermoplastic resin used for this yarn has high strength as a yarn or its woven fabric , and is lightweight and
Inexpensive with excellent moldability, especially high strength as drawn yarn
Degree and good melt adhesion with the laminate coating layer
Preferred polypropylene is used.

Examples of the polypropylene include a polypropylene homopolymer produced using a known heterogeneous catalyst, and a high crystallinity produced using a heterogeneous catalyst and having an isotactic pentad fraction of 0.95 or more. Polypropylene, a highly crystalline polypropylene having an isotactic pentad fraction of 0.95 or more, produced using a metallocene catalyst, or the like is used.

The melting point of the thermoplastic resin used for these yarns is at least 10 ° C. lower than the melting points of the syndiotactic polypropylene, propylene-ethylene copolymer, and a mixture thereof used for the laminate coating layer.
More preferably, it is higher. As a result, thermal degradation given to the woven fabric at the time of laminating can be suppressed, and a laminate sheet having good melt adhesion can be obtained while maintaining high strength without shrinkage.

Further, as a method for suppressing thermal deterioration of the yarn, the structure of the composite yarn is preferable. Specifically, a woven fabric using a composite yarn having a first polypropylene resin as a core layer and an outer layer of a second polypropylene resin having a lower melting point than the first polypropylene resin on the outer surface thereof is used as a part of the process. It is cloth.

In other words, the present invention utilizes the fact that the second polypropylene resin is firmly joined to the laminate coating layer without losing the stretching effect of the first polypropylene resin constituting the composite yarn. The difference in melting point between the first polypropylene resin and the second polypropylene resin is 10
It is important that the temperature be at least 20 ° C, preferably at least 20 ° C. Here, specifically, as the first polypropylene-based resin, a polypropylene homopolymer produced using a known heterogeneous catalyst, and an isotactic pentad fraction produced using a heterogeneous catalyst are used. 0.95 or more highly crystalline polypropylene, isotactic pentad produced by using a metallocene catalyst, a high crystalline polypropylene of 0.95 or more, and syndiotactic as a second polypropylene resin. Syndiotactic polypropylene having a pentad fraction of 0.7 or more,
Alternatively, a mixture of a syndiotactic polypropylene having a syndiotactic pentad fraction of 0.7 or more and a propylene-ethylene copolymer having an ethylene content of 1 to 10% by weight may be used.

As the composite yarn, a three-layer film composed of a core layer and both outer layers laminated or coextruded by a multi-layer T-die flat method or an inflation method or laminated by a sequential extrusion lamination method was cut. The core layer and the resin layer of the sheath layer are extruded and coated on the core layer and the outer surface from a composite flat yarn obtained by longitudinally uniaxially stretching and then performing a heat treatment, or a die in which discharge holes are provided substantially concentrically. A typical example is a monofilament having a core-sheath structure obtained by longitudinally uniaxially stretching the composite filament thus obtained and then performing a heat treatment.

The fineness of the above-described polypropylene yarn is determined in consideration of the required mechanical strength, and is not particularly limited. For example, when the base material for a flexible container is used, the fineness is preferably 500 ~ 500
0dr, more preferably 1000-3000dr. That is, if the fineness is less than 500 dr, the mechanical strength of the yarn constituting the base material for the flexible container is not sufficient. On the other hand, if the fineness exceeds 5000 dr, not only the weaving efficiency is inferior, but also the flexibility as a woven fabric increases. It is inferior, and furthermore, the lamination with the laminate coating layer is not tightly formed, which is a problem in that the physical properties required for the flexible container base material such as peel strength and welding strength cannot be satisfied.

The polypropylene yarn is woven using a known loom such as a circular loom, a sulzer loom, a water jet loom, and the like, and the woven fabric has various weaves such as plain weave, twill weave, and entangled weave. Shape is applied.

This woven fabric has a coating layer formed on both the front and back surfaces to form a laminate sheet. By forming this coating layer, the mechanical strength of the sheet is increased, and the sheet has a strong heat-sealing property by heat sealing. It is possible to prevent contamination of the filler due to penetration of moisture or the like into the bag.

In forming the coating layer on the woven fabric, known techniques such as an extrusion laminating method, a calendering method, a coating method, and a dipping method are employed. At the time of this resin coating, the molten resin penetrates into the gaps of the woven fabric so that they adhere to each other, or the resin penetrates between the front and back sides of the gap generated at the intersection of the warp yarns, thereby joining the front and back layers to form a bridge effect If it appears, the peel strength can be improved and it is effective. Further, the thickness of the coating layer is not particularly limited, but generally 40 to 10 per side in consideration of the substrate strength and the heat-fusibility.
Preferably, the thickness is about 0 μm.

The thus obtained laminate sheet of the present invention has good sealing properties at low temperatures and is effective as a sheet having excellent peel strength and break strength at the heat-sealed portion. It becomes the most suitable laminated sheet for the flexible material used for the flexible container.

In the present invention, an antioxidant, a lubricant, an ultraviolet absorber, a flame retardant, an antistatic agent, a pigment, and the like may be added to the thermoplastic resin used without departing from the gist of the present invention depending on the purpose of use.
Additives such as an inorganic filler, an organic filler, a crosslinking agent, a foaming agent, and a nucleating agent may be blended.

[0037]

EXAMPLES Hereinafter, embodiments of the present invention will be specifically described with reference to examples.

Example 1 Polypropylene (MFR = 2.0 g / 10 min., Mw
/Mn=6.0, Tm = 161 ° C.), put into an extruder, form an extruded film from a circular die by an inflation method, shred it into a tape form, and draw ratio by hot plate contact drawing method. Fineness of 2000dr stretched by 5.2 times
Was used as warp and weft to form a plain woven fabric having a driving density of 15 × 15 yarns / inch and used as a base material. In forming a coating layer on the front and back surfaces of this substrate, syndiotactic polypropylene (syndiotactic pentad fraction = 0.82, MFR = 15.0 g / 10) produced using a metallocene catalyst as a laminate resin
min., Mw / Mn = 2.0, Tm = 130 ° C.) by a melt extrusion lamination method to obtain a laminate sheet with a thickness of 60 μm on each of the front and back surfaces.

Example 2 Syndiotactic polypropylene produced using a metallocene catalyst as the laminating resin (syndiotactic pentad fraction = 0.82, MFR = 15.0 g /
(10 min., Mw / Mn = 2.0, Tm = 130 ° C.) 6
A resin composition in which 40% by weight of a propylene-ethylene random copolymer (MFR = 18.0 g / 10 min., Ethylene content = 6.0 mol%, Tm = 148 ° C.) is blended with respect to 0% by weight. Other than that, it carried out similarly to Example 1.

Comparative Example 1 Example 1 was repeated except that a propylene-ethylene random copolymer (MFR = 18.0 g / 10 min., Ethylene content = 6.0 mol%, Tm = 148 ° C.) was used as the laminating resin. The same was done.

Example 3 Isotactic polypropylene (isotactic pentad fraction = 0.95, MFR = 2.0 g / 10 mi)
n., Mw / Mn = 5.6, Tm = 163 ° C.) as the core resin, and a syndiotactic polypropylene (syndiotactic pentad fraction = 0.82, MFR =) produced using a metallocene catalyst. 15.0g / 10min.,
Mw / Mn = 2.0, Tm = 130 ° C.) and a propylene-ethylene random copolymer (MFR =
18.0 g / 10 min., Ethylene content = 6.0 mol%, Tm = 148 ° C.) A resin composition containing 40 wt% was used as an outer layer resin, and charged into two series of extruders to form an inflation method. After forming an extruded film from a multilayer circular die by using the above method, the extruded film is cut into a tape shape, and stretched at a draw ratio of 5.2 by a hot plate contact stretching method to a fineness of 2,000 d.
The flat yarn of r was used for the warp and the weft, and a plain woven fabric having a driving density of 15 × 15 yarns / inch was used as a base material. In forming a coating layer on the front and back surfaces of this substrate, syndiotactic polypropylene (syndiotactic pentad fraction = 0.82, MFR = 15.0 g / 1) produced using a metallocene catalyst as a laminating resin
0 min., Mw / Mn = 2.0, Tm = 130 ° C.) 80
Using a resin composition in which 20% by weight of a propylene-ethylene random copolymer (MFR = 18.0 g / 10 min., Ethylene content = 6.0 mol%, Tm = 148 ° C.) is blended with respect to% by weight. A laminate sheet was obtained by coating with a thickness of 60 μm on each of the front and back sides by a melt extrusion lamination method.

Comparative Example 2 Example 3 was repeated except that a propylene-ethylene random copolymer (MFR = 18.0 g / 10 min., Ethylene content = 6.0 mol%, Tm = 148 ° C.) was used as the laminating resin. The same was done.

Table 1 shows the measured and evaluated performances of the laminated sheets of Examples and Comparative Examples when used as a raw material for a flexible container.

In the measurement items in Table 1, the tensile strength and the tear strength were measured with a tensile tester according to JISZ1651 using a gripping distance of 150 mm and a tensile speed of 20.
The measurement was performed at 0 mm / min. In addition, the fusion peel strength was set at a pressure of 2 kg / cm ² by changing the fusion temperature to 330, 385, and 410 ° C. with a hot-air pressure bonding machine by laminating two base materials and covering the end portion with a width of 40 mm. Fusion speed 2.1m
/ Min, heat-fused and cut into 30 mm width specimens, using a tensile tester, grasping distance 150 mm,
The peeling was performed at a pulling speed of 200 mm / min by 180 degrees.

[0045]

[Table 1]

From the results shown in Table 1, the laminate sheet of the present example has a good adhesion state between the coating layer and the woven fabric as the base material, and has a higher tensile strength and a lower tensile strength than those using the conventional coating resin.
It was confirmed that both the tear strength and the peel strength became strong, and particularly, the heat sealability at a relatively low temperature was excellent. In addition, the resin composition containing the syndiotactic polypropylene and the propylene-ethylene copolymer was in an extremely good condition such as processability and stability in forming a coating layer by a melt extrusion lamination method.

[0047]

As described above, the laminated sheet of the present invention has good low-temperature sealability and excellent peel strength and break strength of the heat-sealed portion, and is particularly suitable for a flexible container subjected to a heat-sealing process. Useful as a substrate.

Claims (2)

(57) [Claims] 1. A laminate sheet having a resin coating layer formed on both sides of a woven fabric in which a drawn yarn made of polypropylene is woven, wherein the coating layer has a syndiotactic pentad fraction of 0.7 or more. A laminate sheet characterized by being a syndiotactic polypropylene. 2. A laminate sheet having a resin coating layer formed on both sides of a woven fabric in which a drawn yarn made of polypropylene is woven as a base material, wherein the coating layer comprises: A) a syndiotactic pentad fraction of 0; A laminate sheet comprising 95 to 5% by weight of syndiotactic polypropylene of at least 0.7 and B) 5 to 95% by weight of a propylene-ethylene copolymer having an ethylene content of 1 to 10% by weight.