JP5089835B2 - Method for producing stretched film - Google Patents

Description

表１の結果、実施例１、２はいずれも延伸ムラがなく良好であったのに対して、比較例のものは延伸ムラが発生すると共に、突刺し強度は幅方向にバラツキが大きく、均質性に劣るものであることが分かる。
【図面の簡単な説明】
【図１】フィルムの結晶配向を説明する模式図
【図２】本発明に係る延伸フィルムの製造方法の一実施形態を表す概略工程模式図
【図３】図２の下流側工程を示す概略模式図
【図４】図３のテンター装置の概略平面図
【符号の説明】
３１ フィルム状物
Ｆ 延伸フィルム[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a stretched film, and more particularly to a method capable of producing a stretched film made of a crystalline thermoplastic resin having a good mechanical balance without causing stretch breakage during stretching.
[0002]
[Prior art]
A film made of a crystalline thermoplastic resin is excellent in strength such as a high elastic modulus. However, when biaxial stretching is performed by a tenter device or the like, stretched spots are easily generated or transparency is easily lowered. For this reason, a technique has been developed that eliminates the drawbacks that stretch spots and transparency are easily reduced by controlling the stretching temperature, stretching speed conditions, etc. during biaxial stretching in a complicated manner (for example, see Japanese Patent Application Laid-Open (JP-A)). 58-90924).
[0003]
However, even if it does in this way, it is not possible to surely eliminate the defects that cause stretch spots and the transparency tends to decrease, and furthermore, by strictly setting the stretching conditions, let's eliminate the defects of the prior art. (For example, JP-A-5-4276).
[0004]
[Problems to be solved by the invention]
However, all of the above conventional production methods require complicated control of stretching conditions, and the homogeneity of the obtained stretched film is still not sufficient, and in particular, the crystallinity is high, and hence the elastic modulus is high. In the case of a thermoplastic resin having high strength and excellent strength, stretching unevenness has not been solved with certainty, and there is room for improvement.
[0005]
Accordingly, in view of the above-described problems of the prior art, an object of the present invention is to produce a stretched film having a good mechanical balance and high homogeneity made of a crystalline thermoplastic resin without causing stretch breakage during stretching. It is to provide a method that can.
[0006]
[Means for Solving the Problems]
The above object can be achieved by the inventions described in the claims. That is, the method for producing a stretched film according to the present invention is a method of stretching a crystalline thermoplastic resin film-like material in its TD direction, and its characteristic configuration is as the crystalline thermoplastic resin film-like material, The object is to use a thermoplastic resin crystal having a c-axis orientation coefficient of 0.8 or more with respect to the MD direction of the film-like material. Here, the MD direction of the film-like product is a flow direction during the production of the film-like product, and the TD direction is a direction orthogonal to both the flow direction and the thickness direction of the film-like product.
[0007]
According to this configuration, a film produced from a thermoplastic resin having a high crystallinity can be produced without causing breakage or the like during stretching of a stretched film having excellent mechanical balance, little stretching unevenness, and high uniformity. A method can be provided.
[0008]
In the present invention, “the orientation coefficient of the c-axis of the crystal of the thermoplastic resin in the crystalline thermoplastic resin film with respect to the MD direction” is a Hermans orientation coefficient determined by wide-angle X-ray diffraction.
[0009]
As shown in FIG. 1A, a crystalline thermoplastic resin film-like product 31 that has been roll-formed through at least a drawing process using a pair of rolling rolls is fed from a calender roll 33 and taken up on a roll 36. It is done. The crystallized portion X of the film-like product 31 thus manufactured is schematically shown in FIG. As shown in this figure, the c-axis (axis in the lamellar thickness direction) of 80% or more of the polymer molecules 35 constituting the crystalline thermoplastic resin constituting the film-like material is oriented in the MD direction. The state in which the orientation coefficient of the c-axis of the crystal in the film-like material is 0.8 or more with respect to the MD direction of the film-like material is an example of the state.
[0010]
According to the present invention, a crystalline thermoplastic resin having an orientation coefficient of 0.8 or more of the c-axis MD direction of a thermoplastic resin crystal measured by wide-angle X-ray diffraction is used as a film, using a tenter device or the like. Thus, a stretched film is obtained by stretching in the TD direction. The draw ratio is not particularly limited, but is preferably about 2 to 10 times.
[0011]
As a method for obtaining a film of crystalline thermoplastic resin, there are an inflation method, an extrusion method using a T-die, etc., but by producing the crystalline thermoplastic resin by rolling, the c-axis of the thermoplastic resin crystal A crystalline thermoplastic resin film having an orientation coefficient of 0.8 or more in the MD direction can be obtained with certainty.
[0012]
In the present invention, the “crystalline thermoplastic resin” means a thermoplastic resin showing clear crystallinity in X-ray analysis, and more specifically, the crystallinity obtained by wide-angle X-ray diffraction is 10% or more. Means a thermoplastic resin. The “thermoplastic resin” in the above definition includes not only a single type of thermoplastic resin but also a mixture of two or more types of thermoplastic resins. That is, a mixture of two or more types of thermoplastic resins having a crystallinity of 10% or more determined by wide-angle X-ray diffraction of the mixture is used as the “crystalline thermoplastic resin” in the present invention. can do. In the case of a mixture of two or more kinds of thermoplastic resins, it is not necessary that all of the thermoplastic resins to be mixed have crystallinity. That is, even if it is a mixture of a crystalline thermoplastic resin and an amorphous thermoplastic resin, if the crystallinity of the entire mixture is 10% or more, the mixture is referred to as a “crystalline thermoplastic resin” in the present invention. Can be used.
[0013]
Thermoplastic resins include homopolymers of olefins such as ethylene, propylene, butene, hexene or copolymers of two or more types of olefins, and one or more types of polymerizability that can be polymerized with one or more types of olefins. Polyolefin resins that are copolymers with monomers, acrylic resins such as polymethyl acrylate, polymethyl methacrylate, and ethylene-ethyl acrylate copolymers, butadiene-styrene copolymers, acrylonitrile-styrene copolymers, polystyrene, styrene- Styrene resins such as butadiene-styrene copolymer, styrene-isoprene-styrene copolymer, styrene-acrylic acid copolymer, vinyl fluoride resins such as vinyl chloride resin, polyvinyl fluoride, polyvinylidene fluoride, 6 -Nylon, 6,6-na Ron, amide resins such as 12-nylon, saturated ester resins such as polyethylene terephthalate and polybutylene terephthalate, polycarbonate, polyphenylene oxide, polyacetal, polyphenylene sulfide, silicone resin, thermoplastic urethane resin, polyether ether ketone, polyether imide And various thermoplastic elastomers or cross-linked products thereof.
[0014]
The crystalline thermoplastic resin having a crystallinity of 10% or more alone includes olefin homopolymers such as ethylene, propylene, butene and hexene, copolymers of two or more olefins, and one or more olefins. Polyolefin resins, vinyl chloride resins, polyvinyl fluoride, polyvinylidene fluoride and other vinyl resins, polyethylene terephthalate, polybutylene terephthalate, etc., which are copolymers of this olefin and one or more polymerizable synthetic monomers Saturated ester resins, polyphenylene sulfide, polyphenylene oxide, polyether ether ketone, and the like. Even if it is a thermoplastic resin that does not have a crystallinity of 10% or more by itself, it is incorporated into the present invention by blending with a crystalline thermoplastic resin that has a crystallinity of 10% or more alone in an appropriate blending ratio. Can be applied.
[0015]
When polyolefin resin is used as the thermoplastic resin, the molded film is excellent in recyclability and solvent resistance, and since it does not generate dioxins or the like even when incinerated, it does not deteriorate the environment. Therefore, a polyolefin resin can be particularly preferably used.
[0016]
Examples of the olefin constituting the polyolefin resin include ethylene, propylene, butene, hexene and the like. Specific examples of the polyolefin resin include low density polyethylene, linear polyethylene (ethylene-α-olefin copolymer), polyethylene resin such as high density polyethylene, polypropylene resin such as polypropylene and ethylene-propylene copolymer, poly (4-methylpentene-1), poly (butene-1), ethylene-vinyl acetate copolymer and the like.
[0017]
In the present invention, the film-like material is used as a concept including not only a film originally called a film but also a somewhat thick sheet-like material.
[0018]
The film-like product may contain 10 to 300 parts by weight of a filler with respect to 100 parts by weight of the crystalline thermoplastic resin.
[0019]
According to this configuration, when stretched, a porous film having a high elastic modulus can be obtained, and it can be used for various purposes such as filters, separators for batteries or electrolytic capacitors, filtration membranes, moisture-permeable waterproof clothing.
[0020]
When the filler is less than 10 parts by weight, a porous film having air permeability cannot be obtained, and when it exceeds 300 parts by weight, there is a possibility that the film is stretched during stretching. The amount of the filler is more preferably 50 to 200 parts by weight with respect to 100 parts by weight of the crystalline thermoplastic resin. This is because a homogeneous porous film can be obtained.
[0021]
As the filler, inorganic and organic fillers are used. For example, as the inorganic filler, calcium carbonate, talc, clay, kaolin, silica, hydrotalcite, diatomaceous earth, magnesium carbonate, barium carbonate, calcium sulfate, magnesium sulfate, Barium sulfate, aluminum hydroxide, magnesium hydroxide, calcium oxide, magnesium oxide, titanium oxide, alumina, mica, zeolite, glass powder, zinc oxide and the like can be used.
[0022]
As the organic filler, various resin particles can be used, and preferably styrene, vinyl ketone, acrylonitrile, methyl methacrylate, ethyl methacrylate, glycidyl methacrylate, glycidyl acrylate, methyl acrylate or the like alone or in two or more kinds. Examples thereof include particles of a polymer, a polycondensation resin such as melamine and urea.
[0023]
The crystalline thermoplastic resin constituting the film-like material preferably contains 10% by weight or more of a polyolefin having a molecular chain length of 2850 nm or more (referred to as a long molecular chain polyolefin in the present invention).
[0024]
A film containing a long molecular chain polyolefin having a molecular chain length of 2850 nm or more in a crystalline thermoplastic resin is particularly excellent in strength, and such a long molecular chain polyolefin is contained in an amount of 10% by weight or more, more preferably 20% by weight or more. If it is, the strength is remarkably improved, so that it can be used for various purposes, and if it is contained in an amount of 30% by weight or more, a higher strength can be obtained.
[0025]
The long molecular chain polyolefin is preferably used in combination with a polyolefin wax in view of processing. When used in combination with such a wax, there are advantages that the texture of the film is improved and that it is easy to make the film non-porous (for example, when used for a battery separator or the like, safety is increased).
[0026]
Specific examples of the polyolefin wax include low-density polyethylene, linear polyethylene (ethylene-α-olefin copolymer), polyethylene resin such as high-density polyethylene, polypropylene resin such as polypropylene and ethylene-propylene copolymer, Poly (4-methylpentene-1), poly (butene-1), ethylene-vinyl acetate copolymer wax, and the like.
[0027]
For example, a polyolefin resin containing 10% by weight or more of a polyolefin having a molecular chain length of 2850 nm or more includes a polyolefin [A] having a weight average molecular chain length of 2850 nm or more and a polyolefin wax [B] having a weight average molecular weight of 700 to 6000. [A] / [B] = 90/10 to 50/50, and can be obtained by melt kneading.
[0028]
The molecular chain length, weight average molecular chain length, molecular weight, and weight average molecular weight of polyolefin are measured by GPC (gel permeation chromatography), and the mixing ratio (% by weight) of polyolefin in the specific molecular chain length range or specific molecular weight range is The molecular weight distribution curve obtained by GPC measurement can be obtained by integration.
[0029]
The film-like product is preferably stretched in the TD direction at a temperature T that satisfies the following (Condition 1).
(Condition 1) Tm>T> Tm-50
Here, Tm is the melting point of the crystalline thermoplastic resin.
[0030]
According to this configuration, a porous stretched film having good mechanical balance and high homogeneity can be produced without causing stretching unevenness during stretching. When the temperature T of the film-like material at the time of stretching is Tm or higher, a porous film cannot be obtained because it is a nonporous film, and when it is (Tm-50) or lower, stretching is likely to occur at the time of stretching.
[0031]
The melting point is a peak temperature in DSC (Differential Scanning Calorimetry). When there are a plurality of peaks, the peak temperature with the highest heat of fusion ΔH (J / g) is taken as the melting point. Further, the rate of temperature rise when measuring the melting point is 5 ° C./min.
[0032]
DETAILED DESCRIPTION OF THE INVENTION
The manufacturing method of the stretched film which concerns on this invention is demonstrated in detail below. A film-like material is produced from a thermoplastic resin composition containing a crystalline thermoplastic resin and a filler (in the case of producing a porous film), slit into a predetermined width, and then stretched by a stretching apparatus described later. The film is stretched 2 to 10 times in the TD direction to obtain a stretched film. When producing the porous film performs stretching at a temperature lower than the melting point T _m of a crystalline thermoplastic resin, to remove the filler with an acid as needed. A specific process example will be described below with reference to the drawings.
[0033]
<Manufacturing process of film-like product>
FIG. 2 is a schematic diagram showing a production line for producing a crystalline thermoplastic resin film. This production line is composed of a kneading step 1, a rolling step 2, and a slit step 3 in the order of steps. In the example shown below, a polyolefin resin is used.
[0034]
A screw kneading apparatus 10 is used in the kneading step 1, and this kneading apparatus 10 includes a first hopper 11 that supplies a long molecular chain polyolefin PE1 and a polyolefin wax PE2. A filler such as an inorganic filler is supplied from a separately provided second hopper (not shown). By kneading step 1, for example, a resin composition containing 100 parts by weight of a polyethylene resin having a molecular chain length of 2850 nm or more, 10 to 300 parts by weight of a filler, and optionally a nonionic surfactant is obtained. The resin composition may contain other additives such as fatty acid esters, stabilizers, antioxidants, ultraviolet absorbers, and flame retardants as long as the object of the present invention is not impaired.
[0035]
The screw kneading apparatus 10 includes a biaxial screw 13 and strongly kneads and extrudes the mixed resin supplied from the first hopper 11. The resin composition obtained by kneading is pelletized.
[0036]
In the rolling step 2, a screw extruder 20 is used. The apparatus 20 includes a hopper 21 for charging pellets of the resin composition obtained in the kneading step 1 and a screw 22. With this apparatus 20, the resin composition is extruded forward while being plasticized and kneaded, discharged as a rod-shaped or sheet-shaped molten resin with a die 23, and rolled with a rolling roll mechanism 24 to obtain a film.
[0037]
In this case, the surface temperature To of the pair of rolling rolls R1 and R2 located upstream of the rolling roll mechanism 24 on the downstream side of the die 23 is set to a temperature that satisfies the following (Condition 2) and (Condition 3). It is preferable.
[0038]
(Condition 2) Temperature To at which melt tension MT and elongation L of the thermoplastic resin composition are in the following ranges
MT> 10g and L> 100%
(Condition 3) To> Tm
Here, Tm is the melting point of the crystalline thermoplastic resin.
[0039]
In this way, since a film-like product made of resin with high thickness accuracy is obtained, stretching such a film-like product has little unevenness in stretching, and a uniform stretched film can be obtained. In addition, the thickness accuracy is high. A stretched film is obtained.
[0040]
Furthermore, it is preferable that the pair of rolling rolls R1 and R2 be formed by rolling at a substantially constant peripheral speed. In this way, since the surface of the obtained film-like product is excellent in smoothness and beautiful, and a resinous film-like product having a higher film thickness accuracy can be produced, when stretched in the subsequent steps, Thus, a stretched film with even greater thickness accuracy can be obtained. In this case, the peripheral speeds of the pair of rolling rolls R1 and R2 are substantially constant, that both the rolling rolls are strictly the same peripheral speed, or the peripheral speeds of both the rolling rolls are different, but their peripheral speeds are different. It means that the difference in speed is within ± 5%.
[0041]
In addition to the rolling method described above, by carrying out the stretching method described later, the mechanical balance is also achieved for difficult-to-mold resin materials such as highly crystalline thermoplastic resin compositions containing a large amount of resins having a high melt viscosity and a low melt elongation. It is possible to obtain a porous film having excellent uniformity, low stretching unevenness and high homogeneity. Moreover, in this case, even when the film is stretched to a thickness of 200 μm or less, a porous film can be obtained with a high thickness accuracy of about ± 2%.
[0042]
In the slit process 3, the film obtained in the rolling process 2 is cut into two in the width direction, and for example, two 300 mm wide film rolls 36 are obtained from a 600 mm wide rolled film.
[0043]
In addition, the slit process 3 is a process performed as needed, for example, for the purpose of removing unnecessary portions from a resinous film-like material obtained by rolling, or for the purpose of cutting the rolled film into a desired width. Can be omitted.
[0044]
<Process for producing stretched film>
After obtaining the resinous film-like material 31 by the above steps, as shown in FIG. 3, subsequently, the process 4 for stretching the obtained film-like material 31 and the slitting step 5 for further cutting the stretched film are performed. A stretched film is obtained. The slit process 5 is a process performed as needed, for example, for the purpose of removing unnecessary portions from the stretched film or for cutting the stretched film into a desired width, and can be omitted.
[0045]
In the stretching step 4, using the tenter device or the like under the above (Condition 1), the above-mentioned 300 mm-wide rolled film-like material is stretched 2 to 10 times, preferably 4 to 5 times in the TD direction (film width direction). . Thereby, the thermoplastic resin film F extended | stretched to the width direction can be obtained. The stretched film F has a high elastic modulus and strength in the width direction.
[0046]
When producing a porous film from a film-like material containing a filler, more preferably, the stretching step 4 is divided into three heating zones as shown in FIG. Using a tenter device. That is, the tenter device T takes in the film-like material 31 fed from the upstream side from the inlet, and stretches the film-like material in the preheating portion A and TD directions in order to stretch the film-like material 31 while heating. The film is divided into three zones, namely, a stretched part B to be removed and a heat treatment part C to be thermally fixed by removing internal stress due to stretching, and a stretched film having a predetermined thickness is manufactured through each part. And by setting each zone to the temperature conditions according to the following (Condition 4) to (Condition 6), it is possible to produce a stretched film that can be stretched uniformly and without stretch unevenness.
[0047]
(Condition 4) T1 / T2> 1.05
(Condition 5) 1.5> T3 / T2> 1.2
(Condition 6) Tm>T3> (Tm-5)
Here, T1 is a preheating temperature in the preheating portion during stretching, T2 is a stretching temperature in the stretching portion, T3 is a heat setting temperature in the heat treatment portion, and Tm is a melting point of the crystalline thermoplastic resin.
[0048]
In this way, even from a film produced from a crystalline thermoplastic resin composition containing a large amount of a long-chain polyolefin resin, which is a resin composition having a high melt viscosity and a low melt elongation, there is even less stretching unevenness. A highly homogeneous porous film can be produced. Moreover, the filler in a film can be further removed using an acid etc. as needed.
[0049]
In the final slitting step 5, the obtained crystalline thermoplastic resin film is cut into a desired width dimension.
[0050]
Even if the stretched film produced as described above is made of a material having high crystallinity, the stretched film has little stretch unevenness and high homogeneity with good mechanical balance, and also has high elasticity and strength. It was an excellent film. In addition, the film containing no filler was excellent in transparency.
[0051]
【Example】
Hereinafter, actual measurement test results will be described. The measurement results were evaluated for the appearance and puncture strength results.
[0052]
[Measurement of puncture strength]
The maximum load (gf) at which a hole is opened when a metal needle having a needle tip radius of curvature of 0.5 mm and a length of 1 mm is pierced into the fixed film at a rate of 200 mm / min was determined.
[0053]
Example 1
70% by weight of long molecular chain polyethylene powder (manufactured by Mitsui Chemicals, Ltd., Hi-Zex Million 340M, weight average molecular chain length of 17000 nm, weight average molecular weight of 3 million) and 30% by weight of low molecular weight polyethylene powder (weight average molecular weight of 1000) Kneading in a twin-screw reaction extruder, and adding 120 parts by weight of calcium carbonate (Shiraishi Calcium Co., Ltd. Starpigot 15A) to 100 parts by weight of the resin mixture from the middle of the extruder and melting at 230 ° C. After kneading, the film was rolled with a pair of rolls rotating at an equal speed at a roll surface temperature of 150 ° C. to produce a film having a thickness of about 60 μm. When the orientation of the (110) plane of the obtained film was examined by wide-angle X-ray diffraction, the c-axis orientation coefficient of the resin crystal relative to the MD direction was 0.90. This film was stretched 5 times in the TD direction at 110 ° C. by a tenter stretching machine. The content of polyethylene having a molecular chain length of 2850 nm or more in the resin mixture was 27% by weight.
[0054]
(Example 2)
100 parts by weight of polypropylene (manufactured by Sumitomo Chemical Co., Ltd., FS2011D) was kneaded with a twin screw extruder, and 120 parts by weight of calcium carbonate (Shiraishi Calcium Co., Ltd. Piggot 15A) was added and melt kneaded at 230 ° C., and then rolled with a pair of rolls rotating at a constant surface speed at a roll surface temperature of 175 ° C. to prepare a film having a film thickness of about 60 μm. When the orientation of the (110) plane of the obtained film was examined by wide-angle X-ray diffraction, the c-axis orientation coefficient of the resin crystal relative to the MD direction was 0.91. This film was stretched 5 times in the TD direction at 150 ° C. by a tenter stretching machine.
[0055]
(Comparative Example 1)
The film having a c-axis orientation coefficient of 0.90 with respect to the MD direction prepared in Example 1 was pressed with a two-stage press (220 ° C., 100 kgf / cm ² ), and the c-axis of the resin crystal with respect to the MD direction. A film having an orientation coefficient of 0 and an orientation coefficient of 0.44 with respect to the MD of the a-axis was manufactured. Table 1 shows the measurement results of these Examples and Comparative Examples in which this film was stretched at a stretching ratio of 5 times in the TD direction at 110 ° C. with a tenter stretching machine.
[0056]
[Table 1]

As a result of Table 1, Examples 1 and 2 were all good with no stretching unevenness, whereas the comparative example produced stretching unevenness, and the piercing strength had a large variation in the width direction and was homogeneous. It turns out that it is inferior.
[Brief description of the drawings]
FIG. 1 is a schematic diagram illustrating the crystal orientation of a film. FIG. 2 is a schematic process diagram showing an embodiment of a method for producing a stretched film according to the present invention. FIG. 3 is a schematic diagram showing a downstream process of FIG. FIG. 4 is a schematic plan view of the tenter device of FIG.
31 Film-like product F Stretched film

Claims (3)

A method for producing a stretched film in which a crystalline thermoplastic resin film is stretched in the TD direction, wherein the crystalline thermoplastic resin comprises a polyolefin [A] having a weight average molecular chain length of 2850 nm or more , a weight average A crystalline polyolefin resin containing a polyolefin wax [B] having a molecular weight of 700 to 6000 in a weight ratio of [A] / [B] = 90/10 to 50/50 , and the crystalline polyolefin in the film-like product A method for producing a stretched film, wherein an orientation coefficient of the c-axis of the resin crystal with respect to the MD direction of the film-like material is 0.90 or more.  The manufacturing method of the stretched film of Claim 1 in which the said film-form thing contains 10-300 weight part of fillers with respect to 100 weight part of crystalline thermoplastic resins. The method for producing a stretched film according to claim 1 or 2, wherein the film-like material is stretched in a TD direction at a temperature T that satisfies the following conditions:
Tm>T> Tm-50
Here, Tm is the melting point of the crystalline thermoplastic resin.

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