JPH07310273A - Method for reticulating polypropylene laminated film - Google Patents

Abstract

PURPOSE:To ensure the operation for a long period and obtain a split nonwoven fabric excellent in bonding strength, heat resistance, etc., by improving splittability of a polypropylene laminated film and eliminating problems such as remelting of split parts, fuzzing, production of unsplit parts or breakage of branched fibers. CONSTITUTION:The characteristic of this method for reticulating a polypropylene laminated film comprises forming innumerable fine notches in a longitudinally or a transversely uniaxially oriented unit 6, comprising a film prepared by laminating a bonding layer (II), comprising a mixture of a polypropylene-based resin with a polyethylene-based resin and having a lower melting point than that of the polypropylene-based resin in a polypropylene-based resin layer (I) to one or both surfaces thereof according to any one of a mechanical, an air jet, an ultrasonic and a laser methods.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reticulation method for producing a reticulated body of a polypropylene laminated film having a heat seal layer (adhesive layer), which is used for a polypropylene split fiber nonwoven fabric and the like.

[0002]

2. Description of the Related Art Conventionally, as a split nonwoven fabric, a film in which low-density polyethylene is laminated on both sides of high-density polyethylene is stretched and then split, and the resulting mesh film is laminated in a longitudinal direction so that the orientation axes intersect. Has been developed, and non-woven polyethylene made by heat fusion has been developed for agricultural and horticultural use such as agricultural covering materials, green covers for golf courses, filters, drainers, various bags, oil adsorbents, flower wraps, house wraps, etc. Used for materials and construction materials. However, recently, due to the diversification of applications, there has been a demand for inexpensive ones having higher heat resistance, tear resistance, adhesive strength and the like, and improvement of this kind of nonwoven fabric is desired. To meet these demands, polypropylene resin is mentioned as a material having heat resistance superior to that of polyethylene non-woven fabric, and development of polypropylene non-woven fabric using this is expected. However, as a heat seal layer (adhesive layer) laminated on the polypropylene resin layer, propylene-
When an ethylene random copolymer is used, the splitting portion may be re-fused by the high-speed rotation of the rotary blade during splitting, the frictional force during sliding may increase, and fluffing and splitting may occur. Since a phenomenon such as generation of a defective fiber portion or breakage of branch fibers occurs, it is difficult to continue operation for a long period of time, and a good product cannot be obtained. That is,
In this case, there is a drawback that a nonwoven fabric having high adhesive strength and heat resistance cannot be obtained as a final product.

[0003]

DISCLOSURE OF THE INVENTION The inventors of the present invention have made extensive studies to solve the above-mentioned problems, and as a result, by improving the adhesive layer of a multi-layer film based on polypropylene having high crystallinity, The present invention was completed by finding that a split nonwoven fabric having improved splitting properties and excellent properties can be obtained. That is, the object of the present invention, for the high-speed rotation of the rotary blade during splitting, re-fusion of splitting portion, fluffing,
It is an object of the present invention to provide a good product that does not cause a phenomenon such as a defective splitting portion or breaks in branch fibers, ensures long-term operation, and has excellent adhesive strength and heat resistance.

[0004]

The present invention comprises a mixture of a polypropylene resin and a polyethylene resin on one or both sides of the polypropylene resin layer (I), and comprises a polypropylene resin of the resin layer (I). A uniaxially oriented body composed of a film in which an adhesive layer (II) having a low melting point is laminated,
It is a method for reticulating a polypropylene laminated film, which is characterized by forming innumerable fine cuts by any one of a mechanical method, an air jet method, an ultrasonic method, and a laser method.

The present invention will be described in more detail below. In the present invention, examples of the polypropylene-based resin used in the polypropylene-based resin layer (I) include a polypropylene homopolymer, a random copolymer or a block copolymer with other α-olefin containing propylene as a main component. To be Examples of the α-olefin include ethylene and butene-
1,4-methylpentene-1, hexene-1 and the like can be mentioned. The content of these comonomers is selected from the range of 3 to 30 mol%. The MFR of the polypropylene resin is 0.01 to 50 g / 10 minutes, preferably 0.1 to 30.
g / 10 minutes, more preferably 0.2 to 20 g / 10 minutes.

Examples of the polypropylene resin used in the adhesive layer (II) in the present invention include the same or different polypropylene resins as those used in the polypropylene resin layer (I). However, it is important that the melting point of the resin mixture used for the adhesive layer (II) is lower than the melting point of the resin used for the polypropylene resin layer (I),
Therefore, the polypropylene-based resin of the adhesive layer (II) is preferably a random copolymer or block copolymer of propylene and α-olefin, and particularly a random copolymer of propylene and ethylene, 1-butene or the like. Is preferred.

In the present invention, the polyethylene resin used in the adhesive layer (II) has a density of 0.87 to 0.97.
Examples thereof include a polyethylene homopolymer of g / cm ³ and a random copolymer or block copolymer containing ethylene as a main component and another α-olefin having a carbon number of 3 to 12.
Specific examples of the α-olefin include propylene, butene-1, 4-methylpentene-1, and hexene-1. The content of these comonomers is selected in the range of 3 to 30 mol%. Further, as other examples, ethylene homopolymer by high-pressure radical polymerization method, ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, ethylene-acrylic acid ester copolymer, Examples thereof include copolymers of ethylene and a monomer having a polar group, such as ethylene-methacrylic acid ester copolymers. The polyethylene resin has an MFR of 0.01 to 50 g / 10 minutes, preferably 0.1 to 30 g / 10 minutes,
More preferably, it is selected from the range of 0.2 to 20 g / 10 minutes. Among these, high-density polyethylene or ethylene-α-olefin copolymer having a density of 0.94 to 0.97 g / cm ³ is preferable in terms of maintaining splitting property and heat resistance.

The thickness of the polypropylene resin layer (I) before the stretching of the uniaxially oriented body made of the multilayer film is 5
It is in the range of 0 to 200 μm. Further, if the thickness of the adhesive layer (II) is 5 μm or more, the required physical properties such as the adhesive strength at the time of heat fusion are satisfied, but it is usually 5 to 150 μm, preferably 10 to 100 μm. Further, in order not to lose the stretching effect of the polypropylene-based resin layer (I) and for manufacturing reasons, the melting point of the resin of the adhesive layer (II) and the melting point of the resin of the polypropylene-based resin layer (I) are It is preferable to have a temperature difference of 5 ° C or higher, particularly 10 to 50 ° C or higher.

The blending ratio of the mixture of the polypropylene resin and the polyethylene resin forming the adhesive layer (II) used in the present invention is 95 to 70% by weight, preferably 90 to 75% by weight, more preferably polypropylene resin. Is 90
To 80% by weight, the polyethylene resin is 5 to 30% by weight, preferably 10 to 25% by weight, more preferably 1
It is 0 to 20% by weight. If the mixing ratio of the polyethylene-based resin is less than 5% by weight, problems such as re-fusion of splitting portions, fluffing, generation of defective splitting portions, and breakage of branch fibers occur during splitting. On the other hand, when it exceeds 30% by weight, the compatibility of the polypropylene-based resin and the polyethylene-based resin in the adhesive layer is low, which causes a problem such as a decrease in adhesive strength of the product.

The reticulation in the present invention means a mechanical method such as a method of beating a uniaxially oriented body made of the above-mentioned multilayer film, a method of twisting, a method of sliding rubbing (rubbing), a method of brushing, an air jet method, It refers to the formation of innumerable minute cuts by either the ultrasonic method or the laser method, and a mechanical method using a rotary device is particularly preferable. Examples of the method using such a rotary apparatus include various types of splitters such as a tap screw splitter, a file-like rough surface splitter, and a needle roll splitter. FIG. 1 is a partial perspective view of a tap screw splitter. Tap screw type splitter 1a
Usually has a screw thread 3 at the ridge of a prism 2 having a pentagonal or hexagonal cross-sectional shape. A thread having 10 to 40 threads, preferably 15 to 35 threads per inch is used. Further, as the file-like rough surface splitter, the one disclosed in Japanese Utility Model Publication No. 51-38980 is suitable. The file-like rough surface splitter described above forms the surface of the circular cross-section axis into a file of a round file for ironwork or a rough surface of a similar shape, and
The spiral groove of the strip is cut at an equal pitch.

The reticulation method of the present invention is not particularly limited, but a typical example thereof is shown in FIG. The splitter 1 is arranged between each pair of nip rolls 4, 4a and 5, 5a, the uniaxially oriented body 6 is moved along the splitter 1 while applying tension, and is slidably contacted with the rotating splitter 1 to countless numbers. Form fine cuts and reticulate.

FIG. 3 shows the file-like rough surface splitter. FIG. 3 (a) is a partial front view thereof, and the file-like rough surface body splitter 1b has a circular cross-section shaft 7
The spiral groove 9, 9a is formed by grinding two rough grooves 9 and 9a at an equal pitch on the rough surface body on which the filed surface 8 is formed.
9a is formed by a square groove having a depth equal to or higher than the height of a file-like blade on the surface. FIG. 3B is a cross-sectional view taken along line bb of FIG. 3A when the uniaxially oriented body 6 is slid and split into the file-like rough surface body splitter 1b shown in FIG. 3A. Is. Further, FIG. 3C is a partial cross-sectional view of an upper portion when the splitter 1b of FIG. 3B is axially cut. The uniaxially oriented body 6 fits into the spiral grooves 9 and 9a of the splitter 1b by its tension, and at the portion in contact with the filed surface 8, the tension concentrates and receives a large pressing force, and also receives a tensile force in the width direction. It is split. FIGS. 4A and 4B are partial plan views showing examples (10, 13) of a reticulated product of a polypropylene laminated film.
In the figure, 11 is a trunk fiber and 12 is a branch fiber.

The moving speed of the uniaxially oriented body 6 is usually from 1 to
It is 1000 m / min, preferably 10 to 500 m / min.
The rotation speed (peripheral speed) of the splitter can be appropriately selected depending on the physical properties of the film, the moving speed, the properties of the target reticulated film, etc.
It is 3000 m / min, preferably 50 to 1000 m / min. Further, the angle formed by the uniaxially oriented body before and after contacting the splitter is 30 to 180 degrees, preferably 60 to 1
It is 60 degrees. Since the uniaxially oriented body is slippery, it may be difficult to hold the film at a predetermined speed in the nip rolls installed before and after the splitter.Therefore, a nip roll and a clover roll may be used together, or a Nelson roll may be used. It is desirable to take anti-slip measures, such as using the above or combining them.

In the method of brushing at the time of reticulation and the method of using a rotary splitter, it is preferable to operate by applying tension to the uniaxially oriented body. The magnitude of the tension is such that the film undergoes deformation (elongation) of 0.1 to 3%, preferably 0.5 to 2%. In addition, control means such as a dancer roll may be provided to keep the tension of the film constant during splitting.

The temperature during splitting is usually -20 to +1.
The temperature is in the range of 00 ° C., preferably −5 to + 50 ° C., and more preferably 0 to 20 ° C. Further, the split treatment may be performed not only in one step but also in multiple steps, and for a material having a larger thickness. On the other hand, you may perform a split process from the front and back. It is also possible to press the uniaxially oriented body with a rotary baking blade heated above the melting point of the resin and form slits in a zigzag pattern to form a net.

In the present invention, various fillers such as carbon black, calcium carbonate, silica, titanium oxide, mica, antioxidants, flame retardants,
You may mix | blend additives, such as a crosslinking agent, a foaming agent, a coloring agent, a pigment, an antistatic agent, a ultraviolet absorber, and a lubricant.

[0017]

EXAMPLES The present invention will be described in more detail below with reference to examples. <Experimental Examples 1 to 6> First, a multilayer film was produced by a multilayer water-cooled inflation method. That is, 150 mmφ
As a resin for the core layer, the polypropylene (density =
0.90 to 0.91 g / cm ³ , MFR = 1.8 g / 10 minutes, trade name: Nisseki Polypro E120G, manufactured by Nippon Petrochemical Co., Ltd.)
Heat seal layer (adhesive layer) that supplies heat to both sides
Propylene-ethylene random copolymer (trade name: Chisso Polypro FK841, manufactured by Chisso Co., Ltd.)
And high-density polyethylene (density = 0.956g / cm ³ , MFR
= 1.0 g / 10 minutes, trade name: Nisseki Staflen E710, manufactured by Nippon Petrochemical Co., Ltd.) were mixed in the compounding amounts shown in Table 1 and fed to a 90 mmφ extruder, and blown downward. By a water-cooling method in which water is enclosed in bubbles, a multi-layer film having a thickness of 1 μm for each adhesive layer of 15 μm / core layer of 100 μm / adhesive layer of 15 μm is formed for each 20,000
m manufactured. Table 1 shows the results of measurement of static friction force and dynamic friction force of the obtained multilayer film. Then, after stretching the above-mentioned multilayer film 9 times, the film is brought into contact with the splitting tool shown in Japanese Utility Model Publication No. 51-38980 under rotation under the following splitting conditions, and the films are brought into contact with each other in the longitudinal direction by a split treatment. A large number of split fibers were applied to the zigzag hook to produce a longitudinally uniaxially stretched reticulated film. Table 1 shows the evaluation results of the splitting property. Further, the reticulated film thus obtained was laminated in a back-and-forth direction so that the orientation axes intersected with each other to produce a reticulated split nonwoven fabric. The tensile strength, the elongation and the adhesive strength are shown in Table 2. (Splitting condition) Rotation speed of the rotary blade (splitter): 550 rpm Film speed: 105 m / min

The test methods and evaluation criteria are as follows. (1) Dynamic friction force and static friction force Set the multi-layer film on the film holder (1,760 g) so that the surface of the adhesive layer of the multi-layer film is in contact with the steel plate on a horizontal steel plate whose temperature is controlled at 90 ° C. And place the film holder at a constant speed of 500 mm / sec. The initial tensile strength (g) is the static friction force, 15 seconds
The tensile strength after the elapse was defined as the dynamic friction force. (2) Splitting property ◎ --- Small cracks or skips 0 to 1 piece / 5,000m ○ --- Small cracks or skips 2 to 3 pieces / 5,000m △ --- Small cracks or stitches There are 2 to 3 jumps / 500 m × --- There are countless small cracks or skips on the entire surface, and there are also fluffs and large cracks. Note that the skips, small cracks, and large cracks are as follows. Skips (branches): Branch fibers of non-woven fabric have branching of 5 cm or less Small cracks: Branch fibers of non-woven fabric have branching of 10 cm or less Large cracks: More branching (3) Tensile Strength and Elongation A low-speed tension type tensile tester (shopper type) is used, and the interval between the upper and lower parts of the grips of the tester is set to 100 mm, and the test piece (length 200 mm x width 50 mm). Both ends are fixed and pulled at a pulling speed of 200 mm / min, and the load (kg / 5 cm width) and elongation (%) when the test piece is cut are obtained. (4) Adhesive strength Tensilon (trade name, manufactured by Toyo Sokki Co., Ltd.) was used to hang a U-shaped device connected to the load cell of Tensilon from the upper part to the central part of the test piece (length 200 mm x width 150 mm).
Fix the bottom of the test piece to Tensilon. Tensile speed 500
Pull at mm / min and chart speed of 50 mm / min, and find the average value of the amplitude of the load instruction value (kg) when the mesh of the test piece is frayed.

[0019]

[Table 1]

[0020]

[Table 2]

[0021]

According to the present invention, by using a uniaxially oriented film in which a polypropylene resin layer and an adhesive layer made of a mixture of polypropylene resin and polyethylene resin are laminated, splitting property is improved and splitting portion Re-fusion of
It is possible to continuously form a net for a long period of time without causing problems such as fluffing and formation of defective splitting portions, and it is possible to produce a nonwoven fabric excellent in properties such as adhesive strength.

[Brief description of drawings]

FIG. 1 is a partial perspective view of a tap screw splitter.

FIG. 2 is a schematic view of the steps of the reticulation method.

FIG. 3A is a partial front view of a file-like rough surface body splitter, and FIG. 3B is a cross-sectional view taken along the line bb during splitting according to FIG. Further, (c) is a partial cross-sectional view in the axial direction at the time of splitting in FIG.

4 (a) and 4 (b) are partial front views showing an example of a reticulated material according to the present invention.

[Explanation of symbols]

 1 Splitter 1a Tap Screw Type Splitter 1b File-Shaped Rough Surface Splitter 2 Prismatic Column 3 Screw Threads 4, 4a, 5, 5a Nip Roll 6 Uniaxially Oriented Body 7 Circular Section Axis 8 Filed Surface 9, 9a Spiral Groove 10 Example of Reticulated Material 11 Stem Fiber 12 Branch fiber 13 Other examples of reticulated material

Claims (4)

[Claims] 1. An adhesive layer (II) comprising a mixture of a polypropylene resin and a polyethylene resin on one or both sides of the polypropylene resin layer (I) and having a lower melting point than the polypropylene resin of the resin layer (I). ) To a longitudinal or transverse uniaxially oriented body made of a laminated film, a mechanical method,
A method for reticulating a polypropylene laminated film, which comprises forming innumerable fine cuts by any one of an air jet method, an ultrasonic method, and a laser method. 2. The mixture forming the adhesive layer (II) comprises:
The method for reticulating a polypropylene laminated film according to claim 1, which comprises 95 to 70% by weight of a polypropylene resin and 5 to 30% by weight of a polyethylene resin. 3. The adhesive layer (II), wherein the polypropylene resin is a propylene-ethylene random copolymer and the polyethylene resin is a high density polyethylene having a density of 0.94 g / cm ³ or more. A method for reticulating the polypropylene laminated film described. 4. The polypropylene-based resin layer (I) before the orientation of the uniaxially oriented body has a thickness of 50 to 200 μm, and the adhesive layer (II) has a thickness of 5 to 150 μm. The method for reticulating the polypropylene laminated film according to [4].