CN115697671A

CN115697671A - Method for producing conductive film

Info

Publication number: CN115697671A
Application number: CN202180041621.2A
Authority: CN
Inventors: 礒健大; 田中章博
Original assignee: Gunze Ltd
Current assignee: Gunze Ltd
Priority date: 2019-12-20
Filing date: 2021-06-23
Publication date: 2023-02-03
Also published as: JP6906095B2; JP2021098354A; WO2022059284A1

Abstract

The present invention relates to a method for producing a conductive film, comprising a step of preparing a resin composition containing a polyolefin resin and carbon black, a step of discharging the resin composition from a die by using an extruder having a die, and a step of winding the resin composition discharged from the die by using a winder having a cooling roll to obtain a conductive film, wherein when the thickness of the conductive film is measured at 3 points in the TD direction and 300 points in total at 100 points 1cm apart in the MD direction, the average thickness is 200 [ mu ] m or less, the variation width shown in the following formula (1) is 15% or less, and when a change in the elongational viscosity of a test piece is measured in a state where uniaxial elongation deformation is applied to the test piece at a predetermined strain rate by pulling both ends of a columnar test piece made of the resin composition, the difference between the logarithmic value of the elongational viscosity at the predetermined strain rate of 0.02 (/ s) and the logarithmic value of the elongational viscosity at the predetermined strain rate of 0.1 (/ s) is less than 0.5Pa · 1 s) at the time when 5 seconds(s) from the start of the measurement, the logarithmic value of the equation (1 Pa · 5.5 s) is less than 0.5 × 1 (/ s): fluctuation width (%) =100 × (maximum film thickness-minimum film thickness)/average film thickness.

Description

Method for producing conductive film

Technical Field

The present invention relates to a method for manufacturing a conductive film.

Background

Jp 2017-105889 a (patent document 1) discloses a substrate film for polyolefin-based decorative sheets. In the base material film for polyolefin decorative sheets, a predetermined elongation viscosity change rate is 300% or more under a predetermined condition. In a film formed using the substrate film for a polyolefin-based decorative sheet, the occurrence of so-called draw resonance (see patent document 1) is suppressed.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2017-105889

Disclosure of Invention

Technical problem to be solved by the invention

The stretching resonance phenomenon disclosed in patent document 1 may occur when a conductive film is formed by extrusion molding, for example.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a method for producing a conductive film from a resin composition capable of suppressing occurrence of tensile resonance.

Technical solution for solving technical problem

The resin composition of the present invention contains a polyolefin resin and carbon black, and is processed into a conductive film by extrusion molding. When the change in the elongational viscosity of the test piece is measured in a state in which uniaxial elongation deformation at a predetermined strain rate is applied to the test piece by pulling both ends of a columnar test piece made of the resin composition, the difference between the logarithmic value of the elongational viscosity at a predetermined strain rate of 0.02 (/ s) and the logarithmic value of the elongational viscosity at a predetermined strain rate of 0.1 (/ s) is less than 0.5 (Pa · s) at the time when 5(s) has elapsed since the start of the measurement.

For example, in the extrusion molding of a conductive film, a neck-in phenomenon may occur in the vicinity of a resin discharge portion of a die. When the neck-in occurs, the passage length of the resin differs in each region of the conductive film being processed. That is, the length of the resin passing through both ends in the width direction of the conductive film being processed is longer than the length of the resin passing through the center in the width direction of the conductive film. Therefore, the strain rate of the resin is different in each region of the conductive film being processed. In this case, if the elongational viscosity changes greatly in response to the change in the speed of the strain, the elongation state of the resin varies greatly in each region of the conductive film during processing, which causes tensile resonance. In the resin composition of the present invention, even if the strain rate in the test varies between 0.02 (/ s) and 0.1 (/ s), the variation in the logarithmic value of the elongational viscosity is less than 0.5 (Pa · s). Therefore, since the resin composition has a limited change in the elongation viscosity due to a change in the strain rate, even if the conductive film undergoes necking during extrusion molding, the resin in each region of the conductive film does not undergo a large variation in the elongation state, and the occurrence of tensile resonance can be suppressed.

In the resin composition, the polyolefin resin may be a polypropylene resin having a long-chain branched structure.

In the above resin composition, the carbon black may be furnace black.

The method for manufacturing a conductive film of the present invention includes: a step of preparing a resin composition containing a polyolefin resin and carbon black; discharging the resin composition from a die by an extruder having the die; and a step of winding the resin composition discharged from the die by a winder having a cooling roll to obtain a conductive film,

the thickness of the conductive film is 200 μm or less on average when measured at 3 points in the TD direction and 300 points in total at 100 points in the MD direction at 1cm intervals,

the range of variation shown by the following formula (1) is 15% or less,

formula (1): fluctuation range (%) =100 × (maximum film thickness-minimum film thickness)/average film thickness,

when the change in the elongational viscosity of a columnar test piece made of the resin composition is measured in a state where the test piece is uniaxially elongated at a predetermined strain rate by pulling both ends of the test piece,

when 5(s) has elapsed since the start of the measurement, the difference between the logarithmic value of the elongational viscosity at the time when the predetermined strain rate is 0.02 (/ s) and the logarithmic value of the elongational viscosity at the time when the predetermined strain rate is 0.1 (/ s) is less than 0.5 (Pa · s).

In the method for producing a conductive film, the content of the carbon black in the resin composition may be 27wt% or more.

In the method for producing a conductive film, the average thickness of the film measured at the 300 points may be 50 μm or less, and the variation width represented by the formula (1) may be 10% or less.

A method for determining the composition of a resin composition for manufacturing a conductive film, comprising: measuring a change in the elongational viscosity of a columnar test piece made of the resin composition while uniaxial elongation deformation is applied to the test piece at a predetermined strain rate by pulling both ends of the test piece; and

and a step of determining, as the composition of the resin composition for producing the conductive film, a composition of the resin composition when a difference between a logarithmic value of the elongational viscosity at the time when the predetermined strain rate is 0.02 (/ s) and a logarithmic value of the elongational viscosity at the time when the predetermined strain rate is 0.1 (/ s) is less than 0.5 (Pa · s) at a time point when 5(s) has elapsed from the start of the measurement.

The method for manufacturing a second conductive film of the present invention includes: measuring a change in the elongational viscosity of a columnar test piece made of a resin composition containing a polyolefin resin and carbon black while uniaxial elongation deformation is applied to the test piece at a predetermined strain rate by pulling both ends of the test piece;

determining, as the composition of the resin composition for producing the conductive film, a composition of the resin composition when a difference between a logarithmic value of the elongational viscosity at the time when the predetermined strain rate is 0.02 (/ s) and a logarithmic value of the elongational viscosity at the time when the predetermined strain rate is 0.1 (/ s) is less than 0.5 (Pa · s) at a time when 5(s) has elapsed from the start of the measurement; and

and a step of processing a resin composition containing the polyolefin resin and the carbon black into a conductive film by extrusion molding according to the determined composition of the resin composition.

In the method for producing the second conductive film, the polyolefin resin may be a polypropylene resin having a long-chain branched structure.

In the method for producing the second conductive film, the carbon black may be furnace black.

The method for determining the composition of a resin composition for producing a conductive film of the present invention comprises: measuring a change in the elongational viscosity of a columnar test piece made of a resin composition while uniaxial elongation deformation is applied to the test piece at a predetermined strain rate by pulling both ends of the test piece; and

and a step of determining, as the composition of the resin composition for producing the conductive film, a composition of the resin composition when a difference between a logarithmic value of the elongational viscosity at the time when the predetermined strain rate is 0.02 (/ s) and a logarithmic value of the elongational viscosity at the time when the predetermined strain rate is 0.1 (/ s) is less than 0.5 (Pa · s) at a time when 5(s) has elapsed from the start of the measurement.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the method for producing a conductive film of the present invention, occurrence of stretching resonance can be suppressed.

Drawings

Fig. 1 is a view showing a part of an extrusion molding machine.

Fig. 2 is a schematic view showing the inside of the measuring apparatus from the front direction.

Fig. 3 is a schematic view showing the inside of the measuring apparatus from the side direction.

FIG. 4 is a graph showing the measurement results of elongational viscosity in example 1.

FIG. 5 is a graph showing the measurement results of elongational viscosity in example 2.

FIG. 6 is a graph showing the measurement results of elongational viscosity in example 3.

FIG. 7 is a graph showing the measurement results of elongational viscosity of comparative examples.

Detailed Description

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding portions are denoted by the same reference numerals, and redundant description thereof is omitted.

[1. Summary ]

Fig. 1 is a view showing a part of an extrusion molding machine 10 configured to manufacture a conductive film 20 using the resin composition of the present embodiment. As shown in fig. 1, the extrusion molding machine 10 includes a T-die 100 and a cooling roll 110. The resin composition is extruded from the T-die 100 and cooled by the cooling roll 110, thereby being processed into the conductive film 20.

For example, in the extrusion molding of the conductive film 20, a necking phenomenon may occur in the vicinity of the resin discharge portion of the T-die 100. When the necking-in occurs, the resin passage length differs in each region of the conductive film 20 being processed. For example, the length of passage of the resin in the region P1 is different from the length of passage of the resin in the region P2. That is, the resin passage length is longer at both ends in the width direction of the conductive film 20 being processed than at the center in the width direction of the conductive film 20.

Therefore, the strain rate of the resin is different in each region of the conductive film 20 being processed. In this case, if the elongational viscosity of the resin composition changes greatly with a change in strain rate, the elongation state of the resin varies greatly in each region of the conductive film 20 during processing, which causes tensile resonance.

The inventors of the present invention have found that the occurrence of the above-described stretching resonance in the conductive film can be suppressed by preparing the conductive film using a resin composition having an appropriate elongational viscosity. The resin composition of the present embodiment is specifically described below.

[2. Resin composition ]

The resin composition of the present embodiment includes a polyolefin resin and carbon black. Examples of the polyolefin resin include the following types a and B.

The a-type polyolefin resin is, for example, i) a mixture of polypropylene resins having different molecular weight distributions mixed with each other (e.g., an ultrahigh molecular weight component is added, ii) a polypropylene resin partially crosslinked by irradiation with an electron beam or a reaction with a peroxide, or iii) a polypropylene resin having a long chain branched structure.

The polyolefin-based resin B is, for example, a polyolefin-based resin obtained by reacting a polyolefin-based resin B with a polyolefin-based resin composition at a temperature of 230 ℃ under a load of 2.16kg in accordance with JIS K7210-1:2014 is a polypropylene resin having a melt Mass Flow Rate (MFR) greater than 20.

Examples of the carbon black include furnace black and acetylene black.

The resin composition of the present embodiment is characterized in that, when a change in the elongational viscosity of a test piece is measured in a state in which uniaxial elongation deformation based on a predetermined strain rate is applied to a columnar test piece made of the resin composition by pulling both ends of the test piece, the difference between the logarithmic value of the elongational viscosity at a predetermined strain rate of 0.02 (/ s) and the logarithmic value of the elongational viscosity at a predetermined strain rate of 0.1 (/ s) is less than 0.5 (Pa · s) at a time point 5(s) elapses from the start of the measurement. Preferably, when 5(s) has elapsed since the start of the measurement, the difference between the logarithmic value of the elongational viscosity at the predetermined strain rate of 0.02 (/ s) and the logarithmic value of the elongational viscosity at the predetermined strain rate of 0.1 (/ s) is 0.42 (Pa · s) or less. The method for measuring the elongational viscosity will be described in detail later.

According to this resin composition, since the change in the elongational viscosity due to the change in the strain rate is limited, even if the neck-in occurs during the extrusion molding of the conductive film 20, the resin elongation state in each region of the conductive film 20 does not vary greatly, and the occurrence of tensile resonance can be suppressed.

Further, when the amount of filler (for example, the amount of carbon black) contained in the resin composition increases, the conductive film 20 produced using the resin composition is liable to undergo tensile resonance. This is because the amount of plastic deformation of most fillers in the conductive film 20 during molding is very small, and therefore, when the amount of the filler contained in the resin composition is large, the resin portion of the conductive film 20 that can be plastically deformed is divided to be small. When the amount of the filler contained in the resin composition is large, the occurrence of tensile resonance in the produced conductive film 20 becomes remarkable. On the other hand, according to the resin composition of the present embodiment, even if the mass% concentration of the filler is 23wt% or more, the occurrence of the tensile resonance in the conductive film 20 to be formed can be suppressed.

[3. Method for measuring elongational viscosity ]

The elongational viscosity of the resin composition was measured using the measuring device 30. First, the measurement device 30 will be described, and then a method of measuring the elongational viscosity using the measurement device 30 will be described.

Fig. 2 is a schematic view showing the inside of the measuring apparatus 30 from the front direction. Fig. 3 is a schematic diagram showing the inside of the measurement device 30 from the side direction. The directions indicated by the arrows X1, X2, Y1, Y2, Z1, Z2 are common in fig. 2 and 3.

As shown in fig. 2 and 3, the measuring apparatus 30 includes an oil bath 31, a plurality of (two) rollers 300A, a plurality of (two) rollers 300B, a light source 320, an optical fiber 330, a plurality of (two) light irradiators 340A, mirrors 350A, 350B, and a camera 360.

The oil bath 31 is filled with silicone oil. The plurality of rollers 300A, the plurality of rollers 300B, and the

mirrors

350A, 350B are immersed in silicone oil, respectively.

The test piece 40 is composed of a resin composition to be measured. The test piece 40 has a cylindrical shape or a prismatic shape, for example.

The

rollers

300A and 300B in the direction close to the arrow X1 and the

rollers

300A and 300B in the direction close to the arrow X2 are each arranged to hold an end portion of the test piece 40. The

rollers

300A and 300B are each configured to rotate at a constant speed and pull the test piece 40 in the arrow X1 direction or the arrow X2 direction.

At least one of the

rollers

300A, 300B in the direction close to the arrow X1 and the

rollers

300A, 300B in the direction close to the arrow X2 has a load cell configured to detect a load applied to the test strip 40. The test piece 40 is uniaxially deformed by pulling both ends of the test piece 40 by the

rollers

300A and 300B. In addition, the uniaxial elongation deformation means that the first is separated by L ₀ The distance between the two points is changed according to the following equation (1).

L(t)＝L ₀ exp(εt)…(1)

Epsilon: strain rate (sec) ^﹣1 ) (ii) a t: time (sec).

The light source 320 is configured to emit light, and the optical fiber 330 is configured to transmit the light emitted by the light source 320. The

light irradiators

340A, 340B are arranged to irradiate the

mirrors

350A, 350B with light, respectively. The

mirrors

350A and 350B reflect light, respectively, and the reflected light is irradiated to the test piece 40. The camera 360 is configured to photograph light reflected by the test strip 40.

When the above uniaxial elongation deformation is applied to the test piece 40, the cross-sectional area S (t) of the test piece 40 has an initial value of the cross-sectional area S ₀ The number of (2) is reduced as shown in the following equation.

S(t)＝S ₀ exp(-εt)…(2)

In the measurement of the elongational viscosity in the present embodiment, uniaxial elongation deformation is applied to the test piece 40 by the

rollers

300A, 300B, and the load applied to the test piece 40 at this time is detected by the

rollers

300A, 300B having the load cells. Further, the diameter of the test piece 40 is detected based on the image captured by the camera 360 in the state where the uniaxial elongation deformation is applied. The strain rate to which the test piece 40 is subjected is calculated from the data of the detected diameter and the above equation (2). The elongational viscosity is calculated from the cross-sectional area, the calculated strain rate, and the data of the detected load, and the following equation (3).

η _E ＝F/(S×ε)…(3)

η _E : elongation viscosity (Pa · s); f: a load (N); s: cross sectional area (m) ² ) (ii) a Epsilon: strain rate (sec) ^﹣1 )。

The elongational viscosity of the resin composition was measured according to the above method.

[4. Characteristics ]

As described above, the resin composition of the present embodiment contains the polyolefin resin and the carbon black, and is processed into the conductive film 20 by extrusion molding. When a change in the elongational viscosity of the test piece 40 is measured in a state where uniaxial elongation deformation based on a predetermined strain rate is applied to the test piece 40 by pulling both ends of a columnar test piece 40 made of the resin composition, the difference between the logarithmic value of the elongational viscosity at a predetermined strain rate of 0.02 (/ s) and the logarithmic value of the elongational viscosity at a predetermined strain rate of 0.1 (/ s) is less than 0.5 (Pa · s) at a time when 5(s) passes from the start of the measurement.

Therefore, according to this resin composition, since the change in the elongational viscosity due to the change in the strain rate is limited, even if the contraction occurs at the time of extrusion molding of the conductive film 20, the degree of resin elongation in each region of the conductive film 20 does not vary greatly, and the occurrence of tensile resonance can be suppressed.

[5. Examples and comparative examples ]

(5-1. Example 1)

The resin composition of example 1 contained a polypropylene resin having a long-chain branched structure and furnace black. In the resin composition, the mass percentage concentration of the polypropylene resin having a long-chain branched structure was 73wt%, and the mass percentage concentration of the furnace black was 27wt%.

FIG. 4 is a graph showing the measurement results of elongational viscosity of example 1. Referring to fig. 4, the horizontal axis represents time(s) and the vertical axis represents a logarithmic value of elongational viscosity (Pa · s). In example 1, when 5(s) elapsed from the start of measurement of the elongational viscosity, the difference between the logarithmic value of the elongational viscosity at the strain rate of 0.02 (/ s) and the logarithmic value of the elongational viscosity at the strain rate of 0.1 (/ s) was 0.00.

(5-2. Example 2)

The resin composition of example 2 contains a polypropylene resin having a long-chain branched structure and furnace black. In the resin composition, the polypropylene resin having a long-chain branched structure was at a concentration of 70wt%, and the furnace black was at a concentration of 30wt%.

FIG. 5 is a graph showing the measurement results of elongational viscosity in example 2. Referring to fig. 5, the horizontal axis represents time(s) and the vertical axis represents a logarithmic value of elongational viscosity (Pa · s). In example 2, when 5(s) elapsed from the start of measurement of the elongational viscosity, the difference between the logarithmic value of the elongational viscosity at the strain rate of 0.02 (/ s) and the logarithmic value of the elongational viscosity at the strain rate of 0.1 (/ s) was 0.02.

(5-3. Example 3)

The resin composition of example 3 contained the resin composition as defined in JIS K7210-1: a polypropylene resin having a melt Mass Flow Rate (MFR) greater than 20 as determined by the method of 2014, and acetylene black. In the resin composition, the polypropylene resin having an MFR of more than 20 is 75% by mass, and the acetylene black is 25% by mass.

FIG. 6 is a graph showing the measurement results of elongational viscosity of example 3. Referring to fig. 6, the horizontal axis represents time(s) and the vertical axis represents a logarithmic value of elongational viscosity (Pa · s). In example 3, when 5(s) had passed since the start of measurement of the elongational viscosity, the difference between the logarithmic value of the elongational viscosity at the strain rate of 0.02 (/ s) and the logarithmic value of the elongational viscosity at the strain rate of 0.1 (/ s) was 0.42.

(5-4. Comparative example)

The resin composition of the comparative example contained a polypropylene resin having a long-chain branched structure and ketjen black. In the resin composition, the polypropylene resin having a long-chain branched structure was at a concentration of 70wt%, and the ketjen black was at a concentration of 30wt%.

FIG. 7 is a graph showing the measurement results of elongational viscosity of the comparative examples. Referring to fig. 7, the horizontal axis represents time(s) and the vertical axis represents a logarithmic value of elongational viscosity (Pa · s). In the comparative example, when 5(s) had elapsed since the start of measurement of the elongational viscosity, the difference between the logarithmic value of the elongational viscosity at the strain rate of 0.02 (/ s) and the logarithmic value of the elongational viscosity at the strain rate of 0.1 (/ s) was 1.42. The results of examples 1 to 3 and comparative examples are summarized in table 1 below.

[ Table 1]

(5-5 evaluation results of tensile resonance)

Conductive films were prepared using the respective resin compositions of examples 1 to 3 and comparative example, and the respective conductive films were evaluated for tensile resonance. Specifically, the tensile resonance was evaluated by the following method.

Using a full flight single screw extruder (

L/D = 29), the resin composition was extruded under conditions of a 550mm wide clothes hanger die (die lip opening 0.8 mm), a cylinder temperature of 180 to 230 ℃, and a die temperature of 215 ℃, and wound by a winder having a cooling roll (roll temperature 30 ℃), thereby producing a film.

The resin discharge amount was adjusted to be constant in all test zones of each example, so that the change in the thickness level at the same resin composition was dependent only on the change in the winding speed. The film thickness was measured at 300 points in total, wherein 100 points were taken at 1cm intervals in the MD at 3 points in the TD direction at the center of the film and at 15cm positions on both sides of the film.

The occurrence of tensile resonance was evaluated using the fluctuation range shown in the following formula (4).

Fluctuation range (%) =100 × (maximum film thickness-minimum film thickness)/average film thickness value 8230; (4)

The case where the fluctuation range was 10% or less was evaluated as "excellent", the case where the fluctuation range was 15% or less was evaluated as "good", and the case where the fluctuation range exceeded 15% was evaluated as "poor". The evaluation results are summarized in table 2 below.

[ Table 2]

As shown in table 2, example 1 and example 2 were evaluated as "good" at all film thicknesses. Example 3 was evaluated as "excellent" when the film thickness was 200 μm, and as "good" when the film thicknesses were 50 μm and 100. Mu.m. On the other hand, the comparative example was evaluated as "good" when the film thickness was 200 μm, but was evaluated as "poor" when the film thickness was 50 μm and 100 μm.

Description of the symbols

10: an extrusion molding machine; 20: a conductive film; 30: a measuring device; 31: an oil bath groove; 40: a test piece; 100: performing T mold; 110: a cooling roll; 300A, 300B: a roller; 320: a light source; 330: an optical fiber; 340A, 340B: a light irradiation section; 350A, 350B: a mirror; 360: a camera; p1, P2: and (4) a region.

Claims

1. A method for manufacturing a conductive film, comprising:

a step of preparing a resin composition containing a polyolefin resin and carbon black;

a step of discharging the resin composition from a die by using an extruder having the die; and

a step of winding the resin composition discharged from the die by a winder having a cooling roll to obtain a conductive film,

the thickness of the conductive film is 200 [ mu ] m or less on average when measured at 300 points in total at intervals of 100 points of 1cm in the TD direction and the MD direction,

the range of variation shown by the following formula (1) is 15% or less,

when the change in the elongational viscosity of a columnar test piece made of the resin composition is measured in a state where uniaxial elongation deformation at a predetermined strain rate is applied to the test piece by pulling both ends of the test piece,

when 5 seconds have elapsed since the start of the measurement, the difference between the logarithmic value of the elongational viscosity at the predetermined strain rate of 0.02/s and the logarithmic value of the elongational viscosity at the predetermined strain rate of 0.1/s is less than 0.5Pa · s.

2. The method for manufacturing a conductive film according to claim 1, comprising:

the content of the carbon black in the resin composition is 27wt% or more.

3. The method for manufacturing a conductive film according to claim 1 or 2, characterized in that:

the film thickness is measured at the 300 points, and the average value is 50 μm or less, and the variation width shown in the formula (1) is 10% or less.