JP2008023907A - Method for manufacturing flexible shape retaining sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a shape retaining sheet which contains no glass beads nor metal, excels in shape retaining properties, is soft and easy to twist, and is easy to conform even to a minute shape. <P>SOLUTION: The method comprises bending a uniaxially drawn polyolefin resin sheet in the direction approximately perpendicular to a draw direction, the sheet is composed of a polyolefin resin having a weight average molecular weight of 100,000-500,000, rolled by not less than five folds of rolling ratio by applying pressure, and thereafter uniaxially drawn 10-40 folds of draw ratio. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for producing a flexible shape-retaining sheet.

  Conventionally, in order to bind a plurality of parts and members, a binding tape that can be easily bound by hand is used. As this type of binding tape, a metal wire whose outer surface is coated with a vinyl chloride resin or a polyethylene terephthalate resin is commercially available. This binding tape utilizes the metal wire shape retaining property, that is, the property of retaining the bent shape as it is when bent by hand.

  However, recyclability was low because it mainly consists of metal wires. Furthermore, when used on farms, livestock may accidentally eat tying tape and cause digestive problems.

On the other hand, as a substitute for the binding tape using the metal wire described above, a tape mainly composed of synthetic resin has been proposed. For example, a coreless structure composed of a composition obtained by mixing a crystalline thermoplastic synthetic resin such as ultrahigh molecular weight polyethylene, polypropylene, polyamide, polybutylene terephthalate, polyethylene terephthalate, and fine particle glass beads having a particle size of 60 μm or less. A twist tie is disclosed. Here, by using the fine particle glass beads instead of the metal wire, the twist holding property when twisted by hand is given (for example, see Patent Document 1).
JP-A-3-124573

  However, since glass beads are used, there is still a problem in recyclability, and in the case of extrusion from an extruder, there is also a problem that the screw is worn by the glass beads. Furthermore, the glass beads are added to the crystalline thermoplastic synthetic resin to give twist retention, but the twist retention is not always sufficient as compared with the conventional binding tape using a metal wire.

In order to eliminate the above-described drawbacks, a polyethylene binding tape having a total draw ratio of 10 times or more that has been uniaxially stretched after rolling a sheet mainly composed of high-density polyethylene having a weight average molecular weight of 500,000 or less has been proposed (for example, Patent Documents). 2).
JP-A-11-222256

  However, the polyethylene binding tape does not contain glass beads or metal and has excellent shape retention. However, since it is stretched at a high magnification by rolling and stretching, it is hard and difficult to twist. In addition, it is difficult to follow the minute shape, and there is a risk that the object to be bound will fall off when the one having fine irregularities is bound.

  In view of the above problems, an object of the present invention is to provide a method for producing a shape-retaining sheet that does not include glass beads or metal, has excellent shape-retaining properties, is flexible and easily twisted, and is easy to follow in a minute shape. There is.

  The method for producing a flexible shape-retaining sheet of the present invention is a method in which a uniaxially stretched polyolefin resin sheet having a weight average molecular weight of 100,000 to 500,000 and a total stretch ratio of 10 to 40 times is substantially orthogonal to the stretching direction. It bends in the direction to do.

  The stretched polyolefin resin sheet is a polyolefin resin sheet obtained by uniaxially stretching a polyolefin resin sheet having a weight average molecular weight of 100,000 to 500,000 to a total stretching ratio of 10 to 40 times.

  As the polyolefin-based resin constituting the stretched polyolefin-based resin sheet, any olefin-based resin having a film forming ability can be used. For example, a high-density polyethylene resin, a medium-density polyethylene resin, a low-density polyethylene resin, a linear low-density Polyethylene resin, polypropylene resin, ethylene-propylene copolymer, ethylene-butene-1 copolymer, ethylene-pentene-1 copolymer, ethylene-hexene-1 copolymer, ethylene-octene-1 copolymer, ethylene -Vinyl acetate copolymer, ethylene- (meth) acrylic acid ester copolymer, ethylene-vinyl chloride copolymer, ethylene-propylene-butene copolymer, etc. are mentioned, and high-density polyethylene resin is preferably used. .

  When the weight average molecular weight of the polyolefin resin is less than 100,000, the polyolefin resin becomes brittle, the stretchability becomes poor, and a stretched polyolefin resin sheet having sufficient strength or creep resistance can be obtained. Conversely, if it exceeds 500,000, the melt viscosity becomes high, the hot melt molding processability is lowered, and it becomes difficult to obtain a uniform sheet.

  The melt index (hereinafter referred to as MI) of the polyolefin resin is preferably 0.1 to 20 (g / 10 minutes), more preferably 0.2 to 10 (g / 10 minutes), which is excellent in film moldability. is there. MI is an index representing the melt viscosity of a thermoplastic resin specified in JIS K 7210.

Furthermore, in the case of a high density polyethylene resin, 0.94 g / cm ³ or more is preferable because the mechanical strength does not improve even if the density is reduced even if the density is reduced.

  The stretched polyolefin-based resin sheet only needs to be uniaxially stretched at a total stretch ratio of 10 to 40 times, but is uniaxially stretched at a high ratio of 10 to 40 times. Furthermore, it is preferable that the total draw ratio is uniaxially drawn to 10 to 40 times.

  Rolling of the polyolefin-based resin sheet is a method in which the polyolefin-based resin sheet is supplied to a pair of rolls rotating in opposite directions and pressed to reduce the thickness of the sheet and extend, and the rolled sheet is a stretched sheet and In contrast, since the olefin resin is dense without being oriented, it is highly uniaxially stretched easily.

  When the rolling temperature is lowered, uniform rolling cannot be performed, and when it is raised, the melt is cut. Therefore, the roll temperature during rolling is preferably in the range of “melting point−40 ° C.” to melting point of the olefin resin of the polyolefin resin sheet to be rolled. More preferably, it is “melting point−30 ° C.” to “melting point−5 ° C.” of the olefin resin. The melting point means the maximum point of the endothermic peak accompanying the melting of the crystal, which is recognized when thermal analysis is performed with a differential scanning calorimeter (DSC).

  If the applied pressure (linear pressure) applied to the polyolefin resin sheet by the rolling roll is too small, it may not be possible to obtain a predetermined rolling magnification, and conversely if it is too large, not only will the bending of the rolling roll occur, Sliding is likely to occur between the rolling roll and the raw sheet, and uniform rolling may be difficult. Therefore, the applied pressure is preferably 100 MPa to 3000 MPa, and more preferably 300 to 1000 MPa.

  When the rolling ratio is less than 5 times, the effect of suppressing necking cannot be obtained when the uniaxial stretching is performed later, or the high uniaxial stretching cannot be performed. Since a burden is applied, it is 5 times or more, preferably 7 times or more. Although there is no particular upper limit to the rolling ratio, the higher the rolling ratio is, the more load is applied to the rolling equipment.

  The rolling magnification is defined as (cross-sectional area of polyolefin resin sheet) / (cross-sectional area of polyolefin resin sheet after rolling), but the width of the polyolefin resin sheet hardly changes before and after rolling. (Thickness of resin sheet) / (thickness of polyolefin resin sheet after rolling).

  The rolled polyolefin resin sheet is then uniaxially stretched at a total draw ratio of 10 to 40 times, and uniaxial stretching may be any conventionally known method, for example, roll uniaxial stretching method, zone uniaxial stretching, etc. Examples of the method include a method of stretching while heating with a heater or hot air.

  In the uniaxial stretching, the rolled polyolefin resin sheet is stretched to a high degree of 10 to 40 times. Therefore, a multi-stage uniaxial stretching method in which the uniaxial stretching is repeated a plurality of times is preferable. When performing multistage uniaxial stretching, the number of stretching is preferably 2 to 20 times, more preferably 3 to 15 times, still more preferably 4 to 10 times.

  When performing multi-stage stretching by a roll uniaxial stretching method, it is desirable to install a feeding pinch roll, a take-up pinch roll, and at least one, preferably a plurality of contact rolls that rotate at a constant speed between these rolls. By installing such a contact roll, uniform stretchability is improved and stable stretch molding can be performed.

  The contact roll performs uniaxial stretching by applying a frictional force to the polyolefin resin sheet without being pinched. Further, the contact roll may be connected to the feeding roll and / or the take-up roll by a connecting member made of a gear, a chain, a pulley, a belt, or a combination thereof.

  The uniaxial stretching temperature cannot be uniformly stretched when it is low, and the sheet melts and cuts when it is high. Therefore, the range of “melting point−60 ° C.” to the melting point of the polyolefin resin of the polyolefin resin sheet to be stretched is more preferable, It is “melting point−50 ° C.” to “melting point−5 ° C.” of the polyolefin resin.

  The uniaxial stretching ratio may be determined so that the entire stretching ratio is within this range in consideration of the rolling ratio since the entire stretching ratio is 10 to 40 times. Since the mechanical strength is not improved, 1.2 times or more is preferable, more preferably 1.4 times or more, and further preferably 2 times or more. Moreover, although an upper limit is not specifically limited, 4 times or less are preferable, More preferably, it is 3.5 times or less. The overall draw ratio is a numerical value obtained by multiplying the rolling ratio and the uniaxial draw ratio.

  In order to improve the dimensional stability of the uniaxially stretched stretched polyolefin resin sheet, the stretched polyolefin resin sheet that has been uniaxially stretched is the melting point of the polyolefin resin of “melting point−60 ° C.” to the melting temperature or lower. It is preferable to anneal at a temperature.

  If the annealing temperature is lowered, the dimensional stability will not improve, warping will occur if used for a long time, and if it is raised, the polyolefin resin will dissolve and the orientation will disappear and the tensile modulus, tensile strength, etc. will decrease. The resin is annealed at a temperature ranging from “melting point−60 ° C.” to the melting point and below the rolling temperature.

  Annealing is a heat treatment in the production line, and when annealing, the polyolefin resin sheet is stretched if a large tension is applied, and it is not tensioned or shrinks in a very small state. It is preferable to carry out in a state where the length of the polyolefin resin sheet in the rolling direction is not substantially changed, and it is preferable that no pressure is applied to the polyolefin resin sheet. That is, it is preferable to anneal so that the length of the annealed polyolefin resin sheet is 1.0 or less of the length of the polyolefin resin sheet before annealing.

  Accordingly, when the uniaxially stretched stretched polyolefin resin sheet is continuously annealed while being moved in the heating chamber by a roll such as a pinch roll, the feed rate ratio of the polyolefin resin sheet on the inlet side and the outlet side is 1.0. It is preferable that the annealing is performed with setting as follows.

  The heating method at the time of annealing is not particularly limited, and examples thereof include a method of heating with hot air, a heater, a heating plate, hot water or the like. The time for annealing is not particularly limited and varies depending on the thickness of the uniaxially stretched polyolefin-based resin sheet and the annealing temperature, but is generally preferably 10 seconds or more, more preferably 30 seconds to 60 minutes, and still more preferably 1 to 20 minutes.

  The annealed polyolefin resin sheet may be further aged in a temperature range of 40 ° C. to the melting point of the polyolefin resin. The dimensional stability of the polyolefin resin sheet annealed by aging becomes better.

  Aging is not a continuous process in the production line, but a polyolefin resin sheet that has been processed once, such as cut and wound, is used for heat treatment of sheets, scrolls, etc., for a relatively long time (minutes, time units). It means laying down and heat-treating.

  The aging temperature is the same as that left at room temperature when the temperature is low, and when it is high, it is thermally deformed, so the temperature range is from 40 ° C. to the melting point of the polyolefin resin, and the aging time is not effective in a short time and is too long. Even if an effect does not increase, 12 hours-7 days are preferable.

  The thickness of the polyolefin resin sheet is not particularly limited, but if it is too thick, a large pressing force and take-up force are required to crush the polyolefin resin sheet with the rolling roll in the rolling process, and the bending of the rolling roll, etc. In some cases, uniform rolling in the width direction may be difficult.Conversely, if it is too thin, the thickness of the polyolefin resin sheet after rolling becomes too thin and uniform rolling becomes difficult. May be shortened and the life of the rolling roll may be shortened, so 0.05 to 15 mm is desirable.

  In the present invention, flexibility is imparted by bending the uniaxially stretched polyolefin resin sheet in a direction substantially perpendicular to the stretching direction. If the bending direction is close to parallel to the stretching direction, the effect of imparting flexibility is reduced only by the risk of the uniaxially stretched polyolefin resin sheet breaking, so the direction is substantially perpendicular to the stretching direction, It is preferable to bend at an angle of 30 degrees or less, more preferably in the orthogonal direction.

  As a method of bending, any conventionally known method may be employed, and examples thereof include a method of bending a uniaxially stretched polyolefin resin sheet by hand. That is, a flexible shape can be obtained by manually bending a uniaxially stretched polyolefin resin sheet to one side of the sheet so as to be substantially orthogonal to the stretching direction, then returning to the original shape and bending to the opposite side. A retainable sheet is obtained.

  However, since it is difficult to make the entire uniaxially stretched polyolefin resin sheet uniform and flexible when bent by hand, it is preferable to bend mechanically, and it is preferable to bend it around a cylindrical body.

  If the diameter of the columnar body is too small, it will be bent, and if it is too large, the bending rate will be small and the effect of softening the uniaxially stretched polyolefin resin sheet by bending will be small, so 3-40 mm is preferred.

  When the uniaxially stretched polyolefin resin sheet is wound around a cylindrical body and bent, it is preferable to bend from both sides of the stretched polyolefin resin sheet. One surface is wound around a cylindrical body having a diameter of 3 to 40 mm, bent, and then peeled off. Then, the other surface is preferably wound around a cylindrical body having a diameter of 3 to 40 mm and bent.

  In addition, the bending is preferably performed a plurality of times, but the decrease in Young's modulus of the uniaxially stretched polyolefin resin sheet becomes saturated and becomes substantially constant as the number of bends increases, so one surface of the stretched polyolefin resin sheet has a diameter of 3 to 40 mm. It is preferable to bend 1 to 10 sets when the step of winding and bending the cylindrical body is then peeled, and then the other surface is wound around a cylindrical body having a diameter of 3 to 40 mm and bent.

  Further, the uniaxially stretched polyolefin resin sheet may be bent by being wound around a cylindrical roll body and passing therethrough. If the diameter of the cylindrical roll body is too small, it will be bent, while if it is too large, the bending rate will be small, and the effect of softening the uniaxially stretched polyolefin resin sheet by bending will be small, so 3-40 mm is preferable.

  Even when the uniaxially stretched polyolefin resin sheet is bent by being wound around and passed through a cylindrical roll body, it is preferable to bend the uniaxially stretched polyolefin resin sheet a plurality of times, as shown in FIG. Are installed in parallel and wound around the plurality of cylindrical roll bodies so that the traveling direction of the uniaxially stretched polyolefin resin sheet 2 is parallel to the front and rear of the cylindrical roll body and passes in the opposite direction. It is preferable to bend. By bending in this way, the uniaxially stretched polyolefin resin sheet 2 can be bent uniformly in a direction substantially orthogonal to the uniaxial stretch direction.

  When the uniaxially stretched polyolefin resin sheet is wound around a cylindrical roll body and bent, the stretched polyolefin resin sheet is bent from both sides when passing through the two cylindrical roll bodies. It is preferable to bend around a cylindrical roll body.

  Two or more uniaxially stretched polyolefin resin sheets may be laminated and bent. The stretch direction of the laminated uniaxially stretched polyolefin resin sheets is preferably the same, but there may be a deviation of about 30 degrees or less. Moreover, you may laminate | stack the flexible formation holding | maintenance sheet | seat obtained by bending the uniaxially stretched polyolefin resin sheet.

  The structure of the method for producing a flexible shape-retaining sheet of the present invention is as described above, a uniaxially stretched polyolefin resin sheet having a weight average molecular weight of 100,000 to 500,000 and a total stretch ratio of 10 to 40 times Is bent in a direction substantially perpendicular to the stretching direction, a flexible shape-retaining sheet can be easily produced, and the obtained flexible shape-retaining sheet does not contain glass beads or metal and has a shape. It has excellent retention, is flexible and easy to twist, and easily follows fine shapes.

  Next, examples of the present invention will be described, but the present invention is not limited to the following examples.

(Example 1)
A high-density polyethylene resin (manufactured by Nippon Polychem Co., Ltd.) having a weight average molecular weight (Mw) of 330,000 and a melting point of 135 ° C. is supplied to the same-direction twin-screw kneading extruder (manufactured by Plastic Engineering Laboratory) and melt-kneaded at a resin temperature of 200 ° C. After that, the melt-kneaded material was formed into a sheet having a width of 390 mm and a thickness of 5.6 mm by a calender molding machine controlled at a roll temperature of 110 ° C. to obtain a polyethylene resin sheet.

  The obtained polyethylene resin sheet was rolled at a rolling ratio of 10 using a rolling molding machine (manufactured by Sekisui Koki Co., Ltd.) heated to 125 ° C. to obtain a rolled polyethylene resin sheet having a width of 390 mm and a thickness of 0.56 mm.

  The obtained rolled polyethylene resin sheet is subjected to multi-stage stretching of 1.4 times with a hot-air heating type multi-stage stretching apparatus (manufactured by Kyowa Engineering) heated to 110 ° C., the total stretching ratio is 14 times, the width is 230 mm, and the thickness is 0. A uniaxially stretched polyethylene resin sheet of 4 m was obtained.

  The obtained uniaxially stretched polyethylene resin sheet was supplied to a hot air heating tank having a line length of 19.25 m set at 125 ° C. with a pinch roll installed at an inlet speed of 2.75 m / min, and an outlet speed of 2.75 m / min. Set to min and perform primary annealing for 7 minutes, followed by secondary annealing in the same manner to obtain an annealed uniaxially stretched polyethylene resin sheet, which is then fed to a constant temperature bath at 60 ° C. and aged for 24 hours Thus, an aged uniaxially stretched polyethylene resin sheet was obtained.

  The obtained aged uniaxially stretched polyethylene resin sheet was cut in the uniaxial stretch direction to obtain a long sheet having a width of 4 mm. The obtained long sheet was bent 1 set, 5 sets, and 10 sets with a metal cylindrical body having a diameter of 5 mm to obtain a shape-retaining sheet a. In addition, 1 set means winding a long sheet around a metal columnar body and peeling it, then winding the opposite surface around the metal columnar body and peeling it off again.

  Using the obtained long sheet and a metal cylindrical body having a diameter of 10 mm, 15 mm and 33 mm, it was bent in the same manner to obtain shape-retaining sheets b, c and d.

  Using the obtained long sheets and shape-retaining sheets a, b, c and d, the 90-degree bending return angle was measured, and the results are shown in Table 1. The 90-degree bending return angle was measured by a protractor after bending the test piece to 90 degrees and holding it in that state for 1 minute, then releasing and returning after 5 minutes.

  Based on the tensile test of JIS K 7113, Young's modulus, maximum load, maximum load stress and breaking strain were measured, and the results are shown in Tables 2 and 3. Further, the reduction rates of the Young's modulus of the shape-retaining sheets a, b, c and d with respect to the Young's modulus of the long sheet were calculated and shown in Tables 2 and 3.

It is explanatory drawing which shows an example of the manufacturing method of the flexible shape-retainability sheet | seat of this invention.

Explanation of symbols

1 Cylindrical roll body 2 Uniaxially stretched polyolefin resin sheet

Claims (7)

  Flexible shape retention characterized by bending a uniaxially stretched polyolefin resin sheet having a weight average molecular weight of 100,000 to 500,000 and a total stretching ratio of 10 to 40 times in a direction substantially perpendicular to the stretching direction Manufacturing method of adhesive sheet.   The flexible shape-retaining property according to claim 1, wherein the uniaxially stretched polyolefin resin sheet is further uniaxially stretched to 10 to 40 times after being rolled to a rolling magnification of 5 times or more. Sheet manufacturing method.   The method for producing a flexible shape-retaining sheet according to claim 1 or 2, wherein the polyolefin-based resin is a high-density polyethylene resin.   The method for producing a flexible shape-retaining sheet according to any one of claims 1 to 3, wherein the uniaxially stretched polyolefin resin sheet is wound around a cylindrical body having a diameter of 3 to 40 mm and bent.   When one surface of a uniaxially stretched polyolefin resin sheet is wound around a cylindrical body having a diameter of 3 to 40 mm and bent, and then the other surface is wound around a cylindrical body having a diameter of 3 to 40 mm and bent, 1 set is obtained. The method for producing a flexible shape-retaining sheet according to claim 4, wherein 10 sets are bent.   The flexible shape-retaining sheet according to any one of claims 1 to 3, wherein the uniaxially stretched polyolefin resin sheet is bent by being wound around and passed through a cylindrical roll body having a diameter of 3 to 40 mm. Method.   The uniaxially stretched polyolefin resin sheet is wound around a plurality of cylindrical roll bodies, and the stretched polyolefin resin sheet is passed in the opposite direction before and after the cylindrical roll body. Method for producing a flexible shape-retaining sheet.

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