JP2006077238A - Release polypropylene film, and laminated film and laminated sheet made therefrom - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide polypropylene film of high releasability free from the curing toxicity of mainly silicone rubbers and also slight in the transfer of low-molecular materials. <P>SOLUTION: The polypropylene film comprises a polypropylene resin 155-163°C in melting point, being 0.1-2 wt.% in cold xylene solubles(CXS wt.%) and 0.01-1 in the ratio(AO/CXS), wherein AO(wt.%) is the addition proportion of an antioxidant contained. Specifically, CXS(wt.%) is the ratio of the weight of the component attributable to atactic polypropylene extracted from the polypropylene film with cold xylene to the weight of the polypropylene film, and AO(wt.%) is the ratio of the total weight of the antioxidant contained in the polypropylene film to the weight of the polypropylene film. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a polypropylene film for mold release having excellent thermal dimensional stability, and particularly to a polypropylene film preferably used for the production of thermosetting resins such as epoxy resins and silicone resins and / or rubber-like materials. It is. Here, for mold release, for example, when molding a thermosetting resin sheet or member, it is used as a support until the resin or the like is cured, or for the purpose of separation so as not to adhere to other members. Is.

  Since the polypropylene film does not have a polar group in its molecular structure, it has the characteristics that the surface energy is small and the releasability is excellent. In particular, isotactic polypropylene having high stereoregularity is excellent in heat resistance, and is used as a release sheet or release film for manufacturing flexible printed circuit boards, fiber-reinforced plastic moldings, vulcanized rubber, etc. The number of cases used has increased.

  Most of the resins used in these materials are thermosetting resins, and a viscous composition comprising a resin precursor, necessary fillers, and a solvent as necessary is formed into a sheet on a release film. After forming and removing the solvent, the curing reaction proceeds in an oven or the like to obtain the desired material. At this time, the component contained in the release film may be transferred to the composition, but depending on the component, there is a possibility that the curing reaction may be hindered or the characteristics may be deteriorated.

  Specifically, there is a production method in which a slurry liquid that becomes a precursor when producing a crosslinked polymer material sheet represented by silicone rubber is sandwiched between polypropylene films and heated to advance the crosslinking reaction. The polypropylene film may inhibit the crosslinking reaction of silicone. For example, the following description can be found in Non-Patent Document 1 regarding the poisoning substance of addition-type silicone rubber.

“Additional silicone rubber uses a platinum compound as a curing catalyst, and this platinum compound has a relatively strong interaction with a certain compound, which has the disadvantage of losing the ability of hydrosilylation and causing poor curing. Yes. ”
Examples of such poisonous substances include organic compounds containing N, P, S, etc., ionic compounds of heavy metals such as Sn, Pb, Hg, Bi, As, and organic compounds containing multiple bonds such as acetylene groups. As organic rubber (sulfur vulcanized products and anti-aging agents), amines (epoxy, urethane resin cross-linking agents and curing agents, catalysts, aminosilanes, etc.), solder flux, plasticizers and stabilizers contained in soft PVC Type silicone rubber (especially one using Sn-based catalyst).

  In other words, polypropylene films use various additives to stabilize the resin and add functions, but these additives are used in polypropylene films so that they do not interfere with the crosslinking reaction in the production process of silicone rubber, etc. It was necessary to select the composition of the agent.

In addition, since it is necessary to advance the reaction by heating in such a molding process, the thermal dimensional stability of the release film is required. For this reason, by defining the low molecular weight component and melting point of the polypropylene resin used, Attempts to reduce the heat shrinkage rate have been proposed (for example, Patent Document 1). However, when such a polypropylene resin is selected, it is difficult to obtain a uniform and thick film because the stretchability is deteriorated. In particular, it is thick enough to be used as a support for release. It was difficult to produce the film.
Kunio Ito “Silicone Handbook”, Nikkan Kogyo Shimbun (September 1990), p. 391 JP 2001-146536 A (Claims)

  The present invention provides a polypropylene film that does not inhibit the crosslinking reaction in the production process of a silicone rubber sheet or the like, and is excellent in heat resistance and durability, and a laminated sheet comprising the same.

  In order to solve the above problems, the polypropylene film of the present invention has the following constitution. That is, the polypropylene film of the present invention is made of a polypropylene resin having a melting point of 155 to 163 ° C., and the ratio of cold xylene solubles (CXS (wt%)) is 0.1 to 2 wt%. It is a polypropylene film. Here, the ratio CXS (% by weight) of the cold xylene-soluble component means the ratio of the weight of the component derived from the polypropylene resin to the polypropylene film weight in the cold xylene-soluble component of the polypropylene film.

  Moreover, according to the preferable aspect of this invention, in the said polypropylene film, ratio (AXS (weight%)) of the addition ratio of antioxidant to contain to the ratio (CXS (weight%)) of cold xylene soluble content (CXS (weight%)) AO / CXS) is 0.01-1. Here, the addition ratio AO (% by weight) of the antioxidant contained means the ratio of the total weight of the antioxidant contained in the polypropylene film to the weight of the polypropylene film.

  According to the present invention, it is possible to obtain a polypropylene film and a laminated sheet that do not inhibit the crosslinking reaction in the production process of a thermosetting resin sheet such as a silicone rubber sheet and that are excellent in heat resistance and durability.

  Hereinafter, the present invention will be described in detail together with preferred embodiments. The melting point of the polypropylene resin applied to the polypropylene film of the present invention is required to be 155 to 163 ° C, preferably 156 to 162 ° C, more preferably 156 to 161 ° C. When the melting point is lower than 155 ° C, the heat resistance is deteriorated. When the melting point is higher than 163 ° C, the stretchability is deteriorated and thickness spots and heat shrinkage spots are generated, resulting in poor flatness and thermal dimensional stability. Become. A polypropylene resin having a melting point in the range of 155 to 163 ° C. is a method of controlling by stereoregularity, a method of copolymerizing ethylene and α-olefin, and a copolymer of propylene, ethylene and α-olefin as a polypropylene homopolymer. A blending method and the like are exemplified, but a method of controlling by stereoregularity is preferable because it is easy to keep CXS low. The stereoregularity is determined by the catalyst configuration, and can be obtained by controlling the mesopentad fraction, which is an index of stereoregularity, in the range of 0.86 to 0.96.

  Further, a method of copolymerizing α-olefin with propylene is also a preferable method for controlling the melting point within a desired range, and α-olefin includes 1-butene, 1-pentene, 1-hexene, 1-octene, 3 -Methyl-1-butene, 4-methyl-1-pentene and the like are exemplified, but 1-butene is particularly preferable because of good stretchability. The copolymerization amount of α-olefin at this time may be appropriately set so that the melting point is in the above range, but it is preferably 0.5 to 4 mol%, more preferably 1 to 3 mol%. It is preferable.

  The polypropylene film of the present invention is required to have a cold xylene soluble fraction (CXS (wt%)) of 0.1 to 2 wt%, preferably 0.2 to 1 wt%, more preferably Is 0.2 to 0.7% by weight. Here, the ratio CXS (wt%) of the soluble part of cold xylene is the ratio of the weight of the component due to the polypropylene resin to the weight of the polypropylene film out of the soluble part when the polypropylene film is extracted with cold xylene. Means that. If CXS is less than 0.1% by weight, the film-forming stability is inferior, and if it exceeds 2% by weight, thermal shrinkage increases. The method of bringing CXS into the desired range is to reduce the low molecular weight component as much as possible by increasing the catalytic activity, or after washing with propylene after obtaining a polypropylene bulk powder by a known polymerization method, etc. There is a way.

  Next, in the polypropylene film of the present invention, the ratio (AO / CXS) of the total weight of antioxidants contained in the polypropylene film to the weight of the polypropylene film (AO (% by weight)) and the aforementioned CXS (AO / CXS) is 0.01. ~ 1 is preferred. More preferably, it is 0.1-0.4. When AO / CXS is less than 0.01, the deterioration of the mechanical properties of the film becomes a problem due to oxidation deterioration or the like. On the other hand, if AO / CXS is larger than 1, problems such as crosslinking inhibition may occur as a side effect of the excess antioxidant.

  Examples of the antioxidant used in the present invention include phenolic, hindered amine, phosphite, lactone, and tocopherols. Specifically, dibutylhydroxytoluene, pentaerythritol tetrakis [3- (3,5- Di-t-butyl-4-hydroxyphenyl) propionate] (Ciba Specialty Chemicals Co., Ltd .: Irganox® 1010), 1,3,5-trimethyl-2,4,6-tris (3,5 -Di-t-butyl-4-hydroxy) benzene (Ciba Specialty Chemicals Co., Ltd .: Irganox (registered trademark) 1330), Tris (2,4-di-t-butylphenyl) phosphite (Ciba Specialty) Chemicals Co., Ltd .: Irgafos (registered trademark) 168). Among these, at least one selected from phenolic antioxidants or a combination thereof, a combination of phenolic and phosphite, and phenolic and lactone, phenolic and phosphite and lactone Is preferable from the viewpoint of improving the stability of polypropylene.

  Since phosphorus antioxidants usually function as secondary antioxidants, they are often used in combination with phenols that are primary antioxidants. On the other hand, phosphorus-based antioxidants often have a relatively strong inhibitory activity on the silicone crosslinking reaction and are preferably added efficiently. From this point of view, when the antioxidant contains a phosphorus-based antioxidant, the phosphorus-based antioxidant is preferably 20% by weight or less, more preferably 10% by weight or less of the total antioxidant. . From this point of view, when selecting a combination of phenolic and phosphorus antioxidants, it is preferable to use a lactone combined system because the amount of phosphorus antioxidant added can be easily reduced.

  Further, among the phenolic antioxidants, those having a higher melting point tend to reduce the inhibition of the crosslinking reaction, and the melting point is preferably 100 to 250 ° C. in balance with the function as an antioxidant. .

  A polypropylene film having such properties is preferably used when a rubbery polymer crosslinked sheet is produced. Specifically, the precursor slurry is sandwiched between two polypropylene films, and a heat crosslinking reaction is allowed to proceed at 100 to 140 ° C. in an oven. At this time, in order to avoid the deformation of the sheet due to the shrinkage of the polypropylene film, it is preferable to attach a polyester film to the polypropylene film. From the viewpoint of reducing sheet deformation, the thickness ratio of the polyester film to the polypropylene film (the thickness of the polyester film: the thickness of the polypropylene film) is preferably in the range of 2: 1 to 10: 1. On the other hand, when the polypropylene film is used alone, the thickness is preferably about 30 to 200 μm in order to strengthen the waist and improve convenience. Here, the polyester film bonded to the polypropylene film is selected from polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene (2,6) naphthalate (PEN), polypropylene terephthalate (PPT), and these resins. A film made of a mixed resin and / or copolymer resin is exemplified, but from the viewpoint of heat resistance, the melting point is preferably 200 ° C. or higher, more preferably 230 ° C. or higher. From this viewpoint, a film made of a resin selected from PET and PEN is particularly preferable.

  In the present invention, the polypropylene film of the present invention alone or as a laminated film with the polyester film is preferably used as a thermosetting resin sheet molding step and / or a support film of the resin. Here, examples of the thermosetting resin sheet include silicone rubber, melamine resin, epoxy resin, urea resin, and the like, and inorganic and / or organic fillers are added to the resin as necessary. In particular, the film of the present invention is excellent in the thermal dimensional stability of polypropylene film, and since there is little bleeding out of the surface such as antioxidants, it hardly causes problems of inhibition of curing such as silicone resins and rubbers. It is preferable because of its excellent moldability. When the heat shrinkage rate at 120 ° C. is a polypropylene film alone as a measure showing thermal dimensional stability, it is preferably 3.0% or less in the longitudinal direction. Moreover, it becomes about 0.5 to 1.5% of a longitudinal direction by setting it as a laminated film with a polyester film, and is more preferable.

  The rubber-like crosslinked polymer sheet thus obtained is stored in a state in which the polypropylene film is bonded, and the polypropylene film is peeled off if necessary. Therefore, the wetting tension indicating the peeling force of the polypropylene film is required to be 40 mN / m or less on the peeling surface, and more preferably 36 mN / m or less.

  Subsequently, although the manufacturing method of this invention polypropylene film and laminated | multilayer film is described, it is not limited to this.

  In the production process of polypropylene bulk powder, a polypropylene bulk powder whose CXS value is controlled by reducing the low molecular weight component as much as possible, or by washing with propylene after obtaining the polypropylene bulk powder and eliminating low molecular weight products. obtain. In order to obtain a copolymer of propylene and α-olefin, it can be achieved by using the method described in JP-A No. 2002-128825, and the CXS value is controlled by washing.

  Then, in the next granulation step, various antioxidants are added while adjusting their amounts. The polypropylene resin thus obtained is supplied to an extruder, melted at a temperature of 240 ° C. to 270 ° C., passed through a filtration filter, extruded using a T die, molded with a metal drum controlled at 20 to 100 ° C., and unstretched. A film was obtained. This unstretched film is preheated to a temperature of 110 to 150 ° C., stretched 3 to 10 times in the longitudinal direction, cooled to room temperature, and then stretched 4 to 12 times in the transverse direction at 140 to 185 ° C. with a tenter type stretching machine. After relaxing at 0 to 8% at 140 to 160 ° C., necessary surface treatment was performed and wound up to obtain a biaxially stretched polypropylene film for mold release. The polypropylene film thus obtained has a CXS value of 0.1 to 2% by weight and an AO / CXS of 0.01 to 1. In the case of a laminated film, an adhesive such as an acrylic adhesive is applied to the surface-treated surface side of this biaxially stretched polypropylene film, and a polyester film, a thermosetting resin sheet, and a rubber-like polymer crosslinked sheet are applied to the surface. Manufactured by winding after bonding.

Next, the measurement method and evaluation method used in the present invention will be described.
(1) Melting point Using a Seiko RDC220 differential scanning calorimeter, measurement was performed under the following conditions.

  Preparation of sample: 10 mg of polypropylene resin is weighed into an aluminum pan for measurement, and the aluminum pan is sandwiched with a crimper.

Measurement condition:
1st run: The temperature is raised to 280 ° C. at a rate of 20 ° C./min and held for 5 minutes. Thereafter, the temperature is lowered to 25 ° C. at a rate of 20 ° C./min.

  2nd run: Immediately after the 1st run, the temperature is increased to 280 ° C. at a rate of 20 ° C./min.

  The melting peak value at 2nd run is read as the melting point. When there are a plurality of melting peak values, the melting peak having the largest peak area is adopted.

The above measurement was repeated 5 times, and the average value of the remaining 3 points, excluding the maximum and minimum values, was taken as the melting point.
(2) CXS value (cold xylene solubles)
After dissolving 0.5 g of a polypropylene film sample in 100 ml of boiling xylene and allowing to cool, the polypropylene components dissolved in the filtrate after being recrystallized in a constant temperature water bath at 20 ° C. for 1 hour are obtained by liquid chromatography. Quantify (X (g)). Using the precision value (X0 (g)) of 0.5 g of the sample, the following formula is used.

CXS value (% by weight) = X / X0 × 100
(3) Mesopentad fraction A polypropylene film sample is dissolved in a solvent, and a mesopentad fraction (mmmm) (100 fraction) is determined under the following conditions using 13C-NMR. The measurement conditions were as follows.

Apparatus: manufactured by Bruker, DRX-500
Measurement nucleus: 13C nucleus (resonance frequency: 125.8 MHz)
Measurement concentration: 10% by weight (% by weight of the polypropylene film sample with respect to the solvent)
Solvent: benzene / heavy orthodichlorobenzene = 1: 3 mixed solution (volume ratio)
Measurement temperature: 130 ° C
Spin rotation speed: 12Hz
NMR sample tube: 5 mm tube Pulse width: 45 ° (4.5 μs)
Pulse repetition time: 10 seconds Data point: 64K
Number of conversions: 10000 times Measurement mode: complete decoupling
In analyzing the measured results, Fourier transform was performed with an LB (line broadening factor) of 1.0, and the mmmm peak was 21.86 ppm. Peak splitting is performed using WINFIT software (manufactured by Bruker). At that time, the peak splitting is performed from the peak on the high magnetic field side as shown below, and the soft automatic fitting is performed to optimize the peak splitting. The sum of the peak fractions is defined as the mesopentad fraction (mmmm). The measurement is performed with n = 5, and the average value is obtained. The following 10 types of peaks are detected. The above mmmm is (i) and ss is (h).

(A) mrrm, (b) (c) rrrrm (divided as two peaks), (d) rrrr, (e) mrmm + rmrr, (f) mmrr, (g) mmr, (h) ss (mmmm spinning sideband Peak), (i) mmmm, (j) rmmr
(4) Wetting tension The wetting tension of a polypropylene film sample is measured based on a measurement method defined in JIS K 6768 using a mixed solution of formamide and ethylene glycol monoethyl ether. The wetting tension is good if it is 40 mN / m or less.
(5) Heat shrinkage rate The heat shrinkage rate in the longitudinal direction of a polypropylene film sample or a laminated film sample of a polypropylene film and a polyester film is measured according to the method A of the heat shrinkage rate of JIS Z1712. The heat shrinkage ratio is good if it is 3.0% or less for a polypropylene film sample and 0.5 to 1.5% for a laminated film sample of a polypropylene film and a polyester film.
(6) AO / CXS
5 g of a sample piece obtained by cutting a polypropylene film is put into a Soxhlet extractor and extracted with chloroform continuously for 8 hours. This solution is concentrated to about 20 to 40 ml with an evaporator (water bath temperature 40 ° C.) and then transferred to a 50 ml volumetric flask. The container is washed with chloroform and transferred to a volumetric flask, and further chloroform is added to make a 50 ml solution. 2 ml of this is placed in a 10 ml volumetric flask, and acetonitrile is added while shaking the container to make a 10 ml solution. The deposited precipitate is filtered through a disk filter, and then subjected to HPLC analysis under the following measurement conditions.

System: Shimadzu LC-10A (sys-4) system Column: TSKgel ODS-120T 4.6 × 150 mm
Mobile phase: acetonitrile: water = 97: 3 (volume ratio)
Flow rate: 1.5 ml / min
Column temperature: 45 ° C
Detector: Photodiode array Injection volume: 20 μl
In this way, each antioxidant is quantified, and AO is calculated as the sum. A value obtained by dividing AO by CXS is defined as AO / CXS.
(7) Evaluation Method for Curing Thermosetting Resin Sheet A polypropylene film sample or a laminated film sample of a polypropylene film and a polyester film, sandwiching a slurry-like silicone having a size of 400 mm × 400 mm and a thickness of 2 mm (laminated film sample) When sandwiched between, the polypropylene film surface and the slurry-like silicone are placed in contact with each other. After curing at 120 ° C. for 15 minutes, the degree of cure of the silicone resin sheet is measured by a penetration test according to JIS K2207. To do. The penetration value was 1 at 0.1 mm, and it was determined that the curing reaction proceeded without inhibition of curing with a numerical value of 40-80.
(8) 1-butene content According to the method described in the paragraph of (i) Random Copolymer in page 256 of Polymer Analysis Handbook (published by Asakura Shoten in 1985), the content is determined by weight% from the following formula, mol% Converted to.

1-butene copolymerization amount (% by weight) = 1.208 K ′
Absorbance at K ′ = 767 cm ⁻¹

  Six polypropylene resins A to F having different stereoregularity and CXS content were prepared by changing the washing time in the polypropylene polymerization catalyst and the propylene washing step of the raw powder (Table 1). Using this resin, a film was prepared as follows and the characteristics were evaluated. Moreover, the amount of 1-butene was adjusted using the method of Unexamined-Japanese-Patent No. 2002-128825, and the washing | cleaning time of the raw powder was adjusted, and the polypropylene resin G which copolymerized 1 mol of 1-butene in propylene was prepared ( Table 1).

Example 1
A polypropylene resin in which 1500 ppm of Irganox (registered trademark) 1010 and 3000 ppm of dibutylhydroxytoluene as an antioxidant is added to polypropylene resin B is supplied to an extruder, heated and melted to 260 ° C., extruded using a T die, and a metal drum of 40 ° C. And solidified by cooling to obtain an unstretched film. This unstretched film is preheated to a temperature of 140 ° C. and stretched 4.5 times in the longitudinal direction, cooled to room temperature and then led to a tenter-type stretching machine heated to 160 ° C., stretched 8 times in the width direction, Furthermore, it heat-processed, relaxing 5% at 140 degreeC, and obtained the 50-micrometer-thick biaxially-stretched polypropylene film. The polypropylene film has 1.0% by weight of CXS and 0.12 of AO / CXS, is uniformly stretched, has a heat shrinkage rate of 1.7% at 120 ° C. and has excellent heat resistance, and has a wetting tension. Was 32 mN / m, which was suitable for mold release applications. Further, as shown in FIG. 1, even when both sides of the slurry-like silicone were sandwiched between the polypropylene films and subjected to a curing treatment at 120 ° C. for 15 minutes, crosslinking was not inhibited, and silicone curing was confirmed.

(Example 2)
A biaxially stretched polypropylene film having a thickness of 50 μm was obtained in the same manner as in Example 1 except that a polypropylene resin in which the amount of Irganox (registered trademark) 1010 added to polypropylene resin C was 3000 ppm and dibutylhydroxytoluene was added 3000 ppm was used. The polypropylene film has a CXS of 1.5% by weight and an AO / CXS of 0.16, is uniformly stretched, has a heat shrinkage ratio of 120% at a longitudinal direction of 2.0%, and is excellent in heat resistance, and has a wetting tension. Was 32 mN / m, which was suitable for mold release applications. Further, silicone curing was confirmed by the same method as in Example 1.

(Example 3)
A biaxially stretched polypropylene film having a thickness of 49 μm was obtained in the same manner as in Example 1 except that a polypropylene resin in which the amount of Irganox (registered trademark) 1010 added to polypropylene resin C was 1500 ppm and dibutylhydroxytoluene was added 3000 ppm was used. The polypropylene film has a CXS of 1.5% by weight and an AO / CXS of 0.08, is uniformly stretched, has a heat shrinkage rate of 1.9% in the longitudinal direction at 120 ° C., and is excellent in heat resistance. Was 32 mN / m, which was suitable for mold release applications. Further, silicone curing was confirmed by the same method as in Example 1.

Example 4
A biaxially stretched polypropylene film having a thickness of 50 μm was obtained in the same manner except that the polypropylene resin composed of polypropylene resin A was used in Example 1. The polypropylene film is 0.5% by weight of CXS and 0.24 of AO / CXS, is uniformly stretched, has a heat shrinkage ratio of 120% at 120 ° C. and excellent heat resistance, and has a wetting tension. Was 31 mN / m, which was suitable for mold release. Further, silicone curing was confirmed by the same method as in Example 1.

(Example 5)
A film obtained by laminating a 50 μm thick polyester film on the polypropylene film of Example 1, and the both sides of the slurry-like silicone were sandwiched so that the polypropylene film surface was in contact with the slurry-like silicone as shown in FIG. Silicone curing was confirmed by the same method as in Example 1.

(Comparative Example 1)
A biaxially stretched polypropylene film having a thickness of 49 μm was obtained in the same manner except that the polypropylene resin composed of polypropylene resin D was used in Example 1. The polypropylene film has CXS of 3.0% by weight and AO / CXS of 0.08, and silicone curing is confirmed by the same method as in Example 1, but the heat shrinkage at 120 ° C. is 4 in the longitudinal direction. .1% indicating poor heat resistance.

(Comparative Example 2)
A biaxially stretched polypropylene film having a thickness of 48 μm was obtained in the same manner except that the polypropylene resin made of polypropylene resin E was used in Example 1. The polypropylene film had the same CXS value and AO / CXS as in Example 1, and silicone curing was confirmed by the same method as in Example 1. However, the film was inferior in stretchability and uneven in thickness.

(Example 6)
A biaxially oriented polypropylene film having a thickness of 50 μm was obtained in the same manner as in Example 1 except that 10000 ppm of Irganox (registered trademark) 1010 and 10000 ppm of Irgafos (registered trademark) were added as antioxidants. The polypropylene film has the same CXS value as in Example 1, and the heat shrinkage ratio is 120 ° C. and 2.0% in the longitudinal direction, which is excellent in heat resistance, but AO / CXS is 1.5 and When silicone curing treatment was performed in the same manner, crosslinking was inhibited.

(Comparative Example 3)
When a polypropylene resin composed of the polypropylene resin F was used in Example 1, when the film was formed in the same manner as in Example 1, the film was broken in the middle of the process and could not be stably produced.

(Comparative Example 4)
In the film obtained by laminating the polyester film having a thickness of 50 μm on the polypropylene film of Comparative Example 1, the heat shrinkage rate at 120 ° C. is 1.5% in the longitudinal direction, but at the same time, the film is curled greatly toward the polypropylene film side for silicone curing molding. Could not be used.

(Example 7)
A biaxially stretched polypropylene film having a thickness of 49 μm was obtained in the same manner except that the polypropylene resin made of polypropylene resin G was used in Example 1. The polypropylene film has a CXS of 1.5% by weight and an AO / CXS of 0.08, is uniformly stretched, has a heat shrinkage rate of 1.9% in the longitudinal direction at 120 ° C., and is excellent in heat resistance. Was 31 mN / m, which was suitable for mold release. Further, silicone curing was confirmed by the same method as in Example 1.

  The results of each Example and Comparative Example are summarized in Table 2.

  The present invention is not limited to films used in the production process of silicone rubber and the like, but can also be used as a release sheet or film for production of flexible printed substrates, fiber reinforced plastic moldings, vulcanized rubber, etc. The range is not limited to these.

The cross-sectional schematic diagram of the lamination sheet concerning Examples 1-4, 7 of this invention is shown. The cross-sectional schematic diagram of the lamination sheet concerning Example 5 of this invention is shown.

Explanation of symbols

1: Polypropylene film 2: Rubber-like crosslinked polymer sheet (slurry silicone)
3: Polyester film

Claims (12)

A polypropylene film comprising a polypropylene resin having a melting point of 155 to 163 ° C., and having a cold xylene soluble fraction (CXS (wt%)) of 0.1 to 2 wt%.
(However, CXS (% by weight): weight ratio of components derived from the polypropylene resin to the polypropylene film in the cold xylene solubles of the polypropylene film) The ratio (AO / CXS) of the addition ratio of antioxidant (AO (wt%)) to the ratio of cold xylene solubles (CXS (wt%)) is 0.01-1 The polypropylene film according to claim 1.
(However, AO (% by weight): ratio of the total weight of the antioxidant contained in the polypropylene film to the weight of the polypropylene film) The polypropylene film according to claim 1 or 2, wherein the polypropylene resin is a copolymer of propylene and an α-olefin. The polypropylene film according to claim 3, wherein the α-olefin is 1-butene. The polypropylene film according to any one of claims 2 to 4, wherein the antioxidant contains a phenol-based antioxidant having a melting point of 100 to 250 ° C. The polypropylene film according to any one of claims 1 to 5, which has a thickness of 30 to 200 µm. A laminated film obtained by laminating the polypropylene film according to any one of claims 1 to 6 and a polyester film. The laminated film according to claim 7, wherein the melting point of the resin constituting the polyester film is 200 ° C. or higher. A laminated sheet obtained by laminating the polypropylene film according to any one of claims 1 to 6 on at least one surface of a thermosetting resin sheet. A laminated sheet obtained by laminating the laminated film according to claim 7 or 8 on at least one side of a thermosetting resin sheet so that the thermosetting resin sheet and the polypropylene film side of the laminated film are in contact with each other. The laminated sheet according to claim 9 or 10, wherein the thermosetting resin of the thermosetting resin sheet is a rubber-like crosslinked polymer. The laminated sheet according to claim 11, wherein the rubbery polymer crosslinked body is a silicone rubber.

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