WO2004079083A1

WO2004079083A1 - Olefinic tarpaulin and method for preparing the same

Info

Publication number: WO2004079083A1
Application number: PCT/KR2003/000412
Authority: WO
Inventors: Young-Sang Ki
Original assignee: Individual
Current assignee: Individual
Priority date: 2003-03-03
Filing date: 2003-03-03
Publication date: 2004-09-16
Anticipated expiration: 2005-09-03
Also published as: AU2003214661A1

Abstract

The present invention relates to an olefinic tarpaulin prepared by melting and mixing an olefinic copolymer, an olefinic copolymer comprising randomly-coupled ethylene and propylene or vinylacetate, and styrene-ethylene-butane block copolymer in a single screw extruder, and coating the resulting high flexibility and toughness composition on one or both surfaces of a polypropylene woven cloth (multi-filaments) or polyethylene woven cloth (split yarns), and a method for preparing the same. The olefinic tarpaulin comprises a woven cloth formed by weaving polypropylene or polyethylene, and resin layers formed by melting and mixing at least one of ethylene-propylene copolymer and ethylene-vinylacetate copolymer, and styrene-ethylene-butane block copolymer, and styrene-ethylene-butane block copolymer, and coating the resulting composition on one or both surfaces of the woven cloth layer.

Description

Olefinic tarpaulin and method for preparing the same

TECHNICAL FIELD

The present invention relates to an olefinic tarpaulin and a method for preparing the same, and more particularly to an olefinic tarpaulin which shows high flexibility and toughness, reduces its weight, does not generate environmentally-harmful gases in incineration, is recyclable and maintains certain mechanical strength, by melting and mixing an olefinic tarpaulin, an olefinic copolymer comprising randomly-coupled ethylene and propylene or vinylacetate, and styrene-ethylene-butane block copolymer in a single screw extruder, and coating the resulting high flexibility and toughness composition on one or both surfaces of polypropylene woven cloth (multi-filaments, staple fibers, non-woven fabrics, split yarns, etc.) or polyethylene woven cloth (split yarns), and a method for preparing the same.

BACKGROUND ART

In general, olefinic tarpaulins used for a waterproof tent, a protective cover, an original cloth for a temporary tent and an intercepting film for building are classified into PE tarpaulins and PVC tarpaulins according to used materials.

The PE tarpaulin is prepared by drawing HDPE (High Density Polyethylene) films to be a woven cloth, and laminating LDPE (Low Density Polyethylene) resins on both surfaces of the woven cloth. Fig. 1 shows schematic steps of a process for preparing a general PE tarpaulin.

The process for preparing the general PE tarpaulin will now be briefly explained with reference to Fig. 1. An HDPE woven cloth 7 which is a main material of tarpaulin is woven and positioned in an unwinder 6 to be fetched. The woven cloth 7 fetched from the unwinder 6 is transferred to a pressurizing roll 9 of a first extruding unit 21. At the same time, an LDPE mixed resin 2 uniformly mixed in a blender mixer 1 for a predetermined time by operation of a motor M is supplied into a hopper 3 of the first extruding unit 21, and molten and mixed by an extruder 4. The resin extruded into high temperature mobile films through a die 5 is coated on one side surface of the woven cloth 7 transferred from the unwinder 6. Here, the resin passes between a cooling roll 8 and the pressurizing roll 9 of the first extruding unit 21, and thus is coated on the woven cloth 7 under pressure.

The LDPE mixed resin 2 transferred to a second extruding unit 22 and supplied in the same manner is compressed and coated on the other side surface of the woven cloth 7, to prepare a PE tarpaulin. The completed product is wound around a winder 11 in a roll shape.

The PE tarpaulin does not contain environmental contamination substances in production, is recyclable and shows relatively light weight. However, the uses of PE tarpaulin are restricted due to low flexibility and mechanical strength.

In order to solve the foregoing problems, the applicant concerned applied 'Flexible tarpaulin using low density polyethylene weaving' for registration on June 29, 1998, and secured it for registration on June 20, 2000 under Korean Patent Reg. No. 266086. This tarpaulin partially improves flexibility, but does not satisfy conditions of industrial tarpaulin, such as sufficient flexibility and mechanical strength.

On the other hand, the PVC tarpaulin is prepared by coating liquid phase PVC on both surfaces of polyester woven cloth and hardening it according to a curing process, or by producing PVC films according to a calendering process, applying heat to both surfaces of the polyester woven cloth, and laminating the PVC films thereon.

The PVC tarpaulin which shows high weather resistance, excellent flexibility even in low temperature and high mechanical strength has been widely used for industrial purposes. However, the PVC tarpaulin is heavy due to its high density, and generates a lot of dioxin in incineration due to environmental hormone substances used in production.

The present inventor made every effort to overcome disadvantages of the two kinds of tarpaulins, and finally found out that a high flexibility and toughness composition could be prepared by melting and mixing thermoplastic elastomer comprising randomly-coupled ethylene and α-olefin, or styrene-ethylene-butane block copolymer with an olefinic copolymer in a single screw extruder. The resulting composition was uniformed, and coated on one or both surfaces of polypropylene woven cloth (multi-filaments, staple fibers, non-woven fabrics, split yarns, etc.) or polyethylene woven cloth (split yarns) through a T type die. It overcomes disadvantages of the general PE and PVC tarpaulins.

DISCLOSURE OF THE INVENTION An object of the present invention is to provide an olefinic tarpaulin which shows high flexibility and toughness, reduces its weight, prevents environmental problems, is recyclable and maintains high mechanical strength for industrial purposes like a PVC tarpaulin, and a method for preparing the same. In order to achieve the above-described object of the invention, there is provided an olefinic tarpaulin comprising a woven cloth layer formed by weaving polypropylene or polyethylene, and resin layers formed by melting and mixing at least one of ethylene-propylene copolymer and ethylene-vinylacetate copolymer, and styrene-ethylene-butane block copolymer, and coating the resulting composition on one or both surfaces of the woven cloth layer.

Preferably, the resin layers are formed by melting and mixing 30 to 100wt% of ethylene-propylene copolymer, 50 to 70wt% of ethylene-vinylacetate copolymer, and 0 to 50wt% of styrene-ethylene-butane block copolymer.

Preferably, the ethylene-propylene copolymer comprises 50 to 80wt% of thermoplastic elastomer (ethylene-propylene rubber).

Preferably, the ethylene-vinylacetate copolymer comprises 10 to 28wt% of vinylacetate. Preferably, the resin composition is compressed and coated at a cylinder temperature of an extruder ranging from 150 to 280°C, and a temperature of a die ranging from 250 to 300°C.

In addition, there is provided a method for preparing an olefinic tarpaulin including the steps of: supplying a woven cloth formed by weaving polypropylene or polyethylene; preparing a resin composition by melting and mixing at least one of ethylene-propylene copolymer and ethylene-vinylacetate copolymer, and styrene-ethylene-butane block copolymer; and compressing and coating the resin composition on one or both surfaces of the woven cloth. Preferably, the step for preparing the resin composition melts and mixes 30 to 100wt of ethylene-propylene copolymer, 50 to 70wt% of ethylene-vinylacetate copolymer, and 0 to 50wt% of styrene-ethylene-butane block copolymer.

Preferably, the ethylene-propylene copolymer is molten and mixed at a melting index ranging from 20 to 60g/10min.

Preferably, the ethylene-vinylacetate copolymer is molten and mixed at a melting index ranging from 10 to 20g/10min.

Preferably, the styrene-ethylene-butane block copolymer is molten and mixed at a melting index ranging from 3 to lOg/lOmin.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a schematic process diagram showing a process for preparing a general PE tarpaulin; and

Figs. 2 and 3 are structure diagrams illustrating an olefinic tarpaulin in accordance with the present invention, wherein Fig. 2 shows a both-side coated tarpaulin, and Fig. 3 shows an one-side coated tarpaulin.

BEST MODE FOR CARRYING OUT THE INVENTION

An olefinic tarpaulin and a method for preparing the same in accordance with the present invention will now be described in more detail with reference to the accompanying drawings.

In order to prepare an olefinic tarpaulin which shows high flexibility and toughness, reduces its weight, does not generate harmful gases such as dioxin in incineration, is recyclable and maintains mechanical strength equivalent to a PVC tarpaulin, the present invention suggests a method for preparing a following resin composition, and coating it on one or both surfaces of a woven cloth formed by weaving polypropylene or polyethylene.

The resin composition of the invention is an olefinic copolymer prepared by melting and mixing ethylene-propylene copolymer or ethylene-vinylacetate copolymer (component A), and styrene-ethylene-butane block copolymer (component B).

That is, as shown in Fig. 2, the olefinic tarpaulin 30 comprises a woven cloth 32 formed by weaving polypropylene or polyethylene, and resin layers 34 and 36 formed by melting and mixing at least one of ethylene-propylene copolymer and ethylene-vinylacetate copolymer, and styrene-ethylene-butane block copolymer, and coating the resulting composition on one or both surfaces of the woven cloth layer 32.

Here, component A is ethylene-propylene copolymer where a thermoplastic elastomer (ethylene-propylene rubber) comprising randomly-coupled ethylene and propylene exists in a domain type on a propylene copolymer matrix. The thermoplastic elastomer is 50 to 80wt% of poly-olefinic resin. In addition, a melting index of the ethylene-propylene copolymer is preferably 20 to 60g/10min., more preferably 25 to 40g/10min.

If a content of the thermoplastic elastomer is less than 50wt%, sufficient flexibility cannot be obtained. It is also impossible to industrially produce the thermoplastic elastomer over 80wt%. In this case, a melting tension is too high, and thus the process using the facilities of Fig. 1 cannot be performed. In addition, if the melting index is lower than 20g/10min., drawability decreases in the compression and coating process, and if it is over 60g/10min., the thermoplastic elastomer is not smoothly molten and mixed with ethylene-vinylacetate and component B.

In the case of the copolymer comprising the randomly-coupled ethylene and vinylacetate, a content of vinylacetate is preferably 10 to 28wt%, more preferably 15 to 21wt% of poly-olefinic resin. Here, a melting index preferably ranges from 10 to 20g/10min.

If the content of vinylacetate is less than 10wt%, flexibility is reduced, and if it is over 20wt%, the compression and coating process of Fig. 1 cannot be performed due to the increased melting tension. If the melting index is lower than 10g/10min., drawability decreases during the compression and coating process, and if it is over 20g/10min., vinylacetate is not smoothly molten and mixed with ethylene-propylene and component B. Component B is styrene-ethylene-butane block copolymer, namely block copolymer comprising styrene polymer block. That is, component B is a three-component copolymer prepared by adding hydrogen to styrene polymer block and butadiene polymer block, and partially generating ethylene block. A melting index of component B is preferably 3 to 10g/10min., more preferably 4.5 to 7g/10min.

If the melting index is lower than 3g/10min., drawability decreases in the compression and coating process and component B is not smoothly mixed with component A. If it is over 10g/10min., the polymer excessively comprises low molecular weight substances. As a result, the low molecular weight substances lie on the entrance of the T type die of Fig. 1 to cause defects of the products, and make the surfaces of the products sticky to intercept unwinding of the products.

The resin composition of the invention comprises 50 to 100wt%, preferably 60 to 95wt% of ethylene-propylene copolymer as component A, and 0 to 50wt%, preferably 5 to 40wt% of styrene-ethylene-butane block copolymer as component B.

If a content of component A is less than 50wt% and a content of component B is over 50wt%, drawability decreases during the process, and thus the facilities of Fig. 1 cannot be used. In the case that uses of products do not require high flexibility, it is possible to solely employ component A.

In addition, the resin composition comprises 30 to 50wt%, preferably 20 to 40wt% of ethylene-propylene copolymer and 50 to 70wt%, preferably 40 to 60wt% of ethylene-vinylacetate copolymer as component A, and 0 to 30wt%, preferably 10 to 20wt% of styrene-ethylene-butane block copolymer as component B.

In this composition ratio, if the ethylene-propylene copolymer is less than 30wt%, the ethylene-vinylacetate copolymer is over 70wt%, and component B is over 20wt%, the compression and coating process is hardly performed due to excessive melting tension. In addition, if the ethylene-vinylacetate copolymer is less than 50wt%, a bonding process using radio frequency cannot be performed. Therefore, more than 50wt% of ethylene-vinylacetate copolymer must be mixed so as to perform the bonding process using radio frequency.

The resin composition of the invention mainly comprises components A and B, which is not intended to be limiting. A variety of additives can be used within the range of maintaining flexibility, toughness and mechanical strength. For example, various inorganic fillers, master batches thereof, ultraviolet ray stabilizers, antioxidants, antistatic agents, organic or inorganic coloring agents and master batches thereof can be appropriately used.

The process for preparing the olefinic tarpaulin by using the resin composition will now be explained.

In order to prepare the resin composition, component A and/or B need(s) to be firstly molten and then mixed. The molten components can be mixed by using generally-known means such as a kneader, a single screw extruder, a double screw extruder and a static mixer. If necessary, each component can be dry blended and then turned into a composition during the formation.

On the other hand, all kinds of fibers except flat yarns (tape yarns) comprising single polymers of polypropylene, for example, staple fibers, woven cloths made of cotton yarns, and non-woven fabrics can be used as the woven cloth of the invention. A woven cloth made of split yarns comprising polyethylene can also be employed. The fibers having tensile strength of 2.5 to 7g/D can be selectively used for the woven cloth. However, the fibers having tensile strength of 6.5 to 7g/D must be used to prepare the olefinic tarpaulin having sufficient mechanical strength for industrial purposes. In the fiber preparation, a variety of additives, such as master batches comprising concentrated antioxidants, ultraviolet ray stabilizers, flame retardants, antistatic agents, and organic or inorganic coloring agents can be appropriately added without reducing the tensile strength.

In order to prepare the olefinic tarpaulin by using the resin composition, and polypropylene or polyethylene woven cloth, the resin composition molten and mixed by the extruder is compressed and coated on one or both surfaces of the woven cloth according to the compression and coating process of Fig. 1. Here, a cylinder temperature of the extruder is controlled between 150 and 280°C according to the extrusion state from a die, and a temperature of the die is controlled between 250 and 300°C, preferably at 250°C. If the temperature of the die is lower than 250°C, drawability 0412

decreases, which restricts an amount of the resin coated on the woven cloth. If it is over 300°C, the resin composition is thermally decomposed, and thus may lose its intrinsic property. However, if the resin or master batch has a high heat resistance property, the process can be performed over 300°C.

As illustrated in Fig. 2, the olefinic tarpaulin 30 having both-side resin layers 34 and 36 is generally prepared by coating the resin composition on both surfaces of the woven layer 32. As shown in Fig. 3, if necessary, a tarpaulin 30' having an one-side resin layer 34' can be prepared by coating the resin composition on one surface of a woven cloth 32'. So as to prepare the olefinic tarpaulin thicker, the resin composition can be coated once more on the resin layer. The thickness of the olefinic tarpaulin can be appropriately controlled. In addition, if necessary, an embossing process can be performed with the coating process of the resin composition by using a cooling roll embossed in various shapes, thereby preparing an embossed tarpaulin.

The present invention will be better understood by following examples, which are not intended to be limiting.

Examples 1~5 In Examples 1 to 3, 95, 85 and 75wt% of ethylene-propylene copolymers were respectively measured as component A, 5, 15 and 25wt% of styrene-ethylene-butane block copolymers were respectively measured as component B, and the measured components were evenly blended in the dry blender, to prepare resin compositions. Thereafter, the resin compositions were supplied to the hopper of the single screw extruder having the T type die. The supplied resin compositions were molten and mixed in the single screw extruder according to the process of Fig. 1, fetched through the T type die, firstly coated on one-side surfaces of the woven cloths (polypropylene multi-filaments having a diameter and size of Table 1 were respectively used in Examples 1 to 3) transferred from the unwinder through the first extruding unit, and secondly coated on the other-side surfaces of the woven cloths through the second extruding unit, to prepare tarpaulins. Here, the temperature was controlled in two parts of the cylinder of the single screw extruder between 180 and 260°C, and the temperature was controlled in seven parts of the T type die between 280 and 300°C.

To evaluate the physical properties of the olefinic tarpaulins prepared in Examples 1 to 3, tensile strength and tearing strength thereof were measured according to KS KO520 and KS0363, and shown in Table 2 with thickness and weight thereof. On the other hand, in Examples 4 and 5, 30 and 45wt of ethylene-propylene copolymers and 60 and 50wt% of ethylene-vinylacetate copolymers were respectively measured as component A, and 10 and 5wt% of styrene-ethylene-butane block copolymers were respectively measured as component B, to prepare resin compositions. The procedure of Examples 1 to 3 was repeated by using polypropylene multi-filaments and polyethylene slit yarns as woven cloths, and physical properties of the olefinic tarpaulins were shown in Table 2.

Comparative Examples 1 and 2

For comparative experiment, the commercially- sold PVC tarpaulin was used instead of the resin composition comprising components A and B. Tensile strength and tearing strength of the PVC tarpaulin were measured according to KS KO520 and KS0363, and shown in Table 2 with thickness and weight thereof.

As shown in Table 2, the olefinic tarpaulins comprising the resin compositions in Examples 1 to 5 have higher tensile strength than the PVC tarpaulins of Comparative Examples 1 and 2, the olefinic tarpaulins of Examples 1 to 3 have slightly lower tearing strength than the PVC tarpaulins, and the olefinic tarpaulins of Examples 4 and 5 have tearing strength equivalent to the PVC tarpaulins. Instead, the olefinic tarpaulins of Examples 1 and 2 are lighter in weight than the PVC tarpaulins.

INDUSTRIAL APPLICABILITY

As described above, the olefinic tarpaulin prepared by using the resin composition comprising components A and B has high toughness and flexibility, reduces its weight, does not includes harmful elements causing environmental problems, is recyclable, and maintains mechanical strength equivalent to the general PE tarpaulin or PVC tarpaulin. As a result, the olefinic tarpaulin can be variously used for industrial purposes.

Claims

WHAT IS CLAIMED IS:

1. An olefinic tarpaulin comprising: a woven cloth layer formed by weaving polypropylene or polyethylene; and resin layers formed by melting and mixing at least one of ethylene-propylene copolymer and ethylene-vinylacetate copolymer, and styrene-ethylene-butane block copolymer, and coating the resulting composition on one or both surfaces of the woven cloth layer.

2. The olefinic tarpaulin of claim 1, wherein the resin layers are formed by melting and mixing 30 to 100wt% of ethylene-propylene copolymer, 50 to 70wt% of ethylene-vinylacetate copolymer, and 0 to 50wt% of styrene-ethylene-butane block copolymer.

3 The olefinic tarpaulin of claim 1 or 2, wherein the ethylene-propylene copolymer comprises 50 to 80wt% of thermoplastic elastomer (ethylene-propylene rubber).

4. The olefinic tarpaulin of claim 1 or 2, wherein the ethylene-vinylacetate copolymer comprises 10 to 28wt% of vinylacetate.

5. A method for preparing an olefinic tarpaulin, comprising the steps of: supplying a woven cloth formed by weaving polypropylene or polyethylene; preparing a resin composition by melting and mixing at least one of ethylene-propylene copolymer and ethylene-vinylacetate copolymer, and styrene-ethylene-butane block copolymer; and compressing and coating the resin composition on one or both surfaces of the woven cloth.

6. The method of claim 5, wherein the step for preparing the resin composition melts and mixes 30 to 100wt% of ethylene-propylene copolymer, 50 to 70wt% of ethylene-vinylacetate copolymer, and 0 to 50wt% of styrene-ethylene-butane block copolymer.

7. The method of claim 5 or 6, wherein the ethylene-propylene copolymer is molten and mixed at a melting index ranging from 20 to 60g/10min.

8. The method of claim 5 or 6, wherein the ethylene-vinylacetate copolymer is molten and mixed at a melting index ranging from 10 to 20g/10min.

9. The method of claim 5 or 6, wherein the styrene-ethylene-butane block copolymer is molten and mixed at a melting index ranging from 3 to lOg/lOmin.

10. The method of claim 5 or 6, wherein the resin composition is compressed and coated at a cylinder temperature of an extruder ranging from 150 to 280°C, and a temperature of a die ranging from 250 to 300°C.