JP2008018731A - Production process for transparent polypropylene sheet and transparent polypropylene sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a production process for a transparent polyproylene sheet which has impact resistance and rigidity while securing transparency and is free from whitening during fold processing as a secondary processing, and the transparent polypropylene sheet. <P>SOLUTION: The production apparatus 1 of the present invention is equipped with a sheet molding means 11 to melt and knead a raw material and extrude it into sheet form, a first cooling means 12 to cool and solidify a sheet 20, a preheating means 13 to reheat the cooled sheet 20, a heat treatment means 14 to heat-treat the sheet 20 into a sheet 21, and a second cooling means 15 to cool the heat-treated sheet 21. The raw material thereof comprises 60-97 mass% of a polypropylene resin (A) that is 0.85-0.99 in isotactic pentad fraction and 2-10 g/10 min in melt index, and 40-3 mass% of a polypropylene resin (B) that is 0.15-0.50 in racemic pentad fraction and 2-10 g/10 min in melt index. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for producing a transparent polypropylene sheet and a transparent polypropylene sheet.

  Conventionally, polyvinyl chloride resins that are frequently used in the field of transparent sheets have been used. However, with the recent increase in awareness of environmental problems and the like, new transparent sheets that replace polyvinyl chloride resins are required. As these sheets, sheets made of polypropylene are used. However, depending on the application, not only the transparency but also other physical properties, in particular, a sheet superior in impact resistance is desired.

  As a method for improving the impact resistance of a transparent polypropylene sheet, (1) a rapid cooling method using an HPP (homopolypropylene) resin composition containing a low crystalline ethylene-butene-1 copolymer (see Patent Document 1) (2) A rapid cooling method using a low-density ethylene-propylene-butene-1 copolymer and a nucleating agent-containing HPP resin composition, and in this case, PP is blended with RPP (random polypropylene) as PP (patent) A method of (3) and a rapid cooling method using HPP blended with an ethylene-propylene rubber and an ethylene-α-olefin copolymer are known.

  Furthermore, as a method for improving the rigidity and transparency of a transparent polypropylene sheet, (4) a method of blending a raw material of polypropylene with a clarifying agent such as a nucleating agent or petroleum resin is known.

Japanese Patent Laid-Open No. 62-227722 JP-A-1-306448

  However, in the methods (1), (2) and (3), although improvement in impact resistance can be expected, there is a reduction in sheet rigidity and sacrifices transparency. In addition, new problems such as transparency due to the generation of gel during sheet recycling, poor appearance, poor printability, and whitening during folding are generated. Further, in the method (4), a decrease in impact resistance becomes a problem.

  An object of the present invention is to provide a method for producing a transparent polypropylene sheet that has impact resistance and rigidity while ensuring transparency and has no whitening during bending as a secondary process, and a transparent polypropylene sheet. is there.

  As a result of intensive studies to develop a transparent polypropylene sheet having the above-mentioned preferable properties, the present inventors have obtained a shock resistance while ensuring transparency from a resin composition comprising a polypropylene resin having a specific composition. It has been found that a transparent polypropylene sheet having high properties and rigidity and having no whitening during bending as a secondary process can be obtained. The present invention has been completed based on such findings.

  That is, in the method for producing a transparent polypropylene sheet of the present invention, (A) the isotactic pentad fraction is 0.85 to 0.99, and the racemic pentad fraction [rrrr / (1-mmmm)] is 0. Less than .15 or more than 0.50 and a melt index of 2 to 10 g / 10 min of polypropylene resin 60 to 97% by mass, and (B) racemic pentad fraction [rrrr / (1-mmmm)] of 0.15 A resin composition comprising 40 to 3% by mass of a polypropylene resin having an isotactic pentad fraction of less than 0.85 or more than 0.99 and a melt index of 2 to 10 g / 10 min. A molding step of melt-extruding the sheet, a cooling step of rapidly cooling the melt-extruded sheet, and the cooled sheet Characterized in that it comprises a heat treatment step of heat-treating the following emission resin melting point.

  The component ratio of the polypropylene resin (A) is 60 to 97% by mass, preferably 70 to 95% by mass of the entire resin composition. Moreover, the component ratio of a polypropylene resin (B) is 40-3 mass% of the whole resin composition, Preferably, it is 30-5 mass%.

  The melt index (MI) can be measured by a method based on JIS K7210. The melt index of the polypropylene resin (A) is 2 to 10 g / 10 minutes, preferably 2 to 5 g / 10 minutes. The melt index of the polypropylene resin (B) is 2 to 10 g / 10 minutes, preferably 2 to 5 g / 10 minutes.

Here, the isotactic pentad fraction is an isotactic fraction in pentad units (one in which five propylene monomers are isotactically bonded) in a resin molecular chain. That is, it refers to the mmmm ratio (PI value) in the pentad fraction measured using ¹³ C-NMR for the stereoregularity of homopolypropylene.
This mmmm (00000) or (11111) means an isotactic pentad. m represents an isotactic yard, 0, 1 represents the configuration of individual monomer units along the polymer chain, 0 represents one configuration, and 1 represents the opposite configuration.

A method for measuring this isotactic pentad fraction has been published in Macromolecules 6925 (1973).
The isotactic pentad fraction of the polypropylene resin (A) is 0.85 to 0.99, preferably 0.87 to 0.96. When the isotactic pentad fraction is less than 0.85, the elastic modulus and other strengths are lowered. When it exceeds 0.99, the internal haze in a rapid cooling process will deteriorate, and the use as a transparent polypropylene sheet will become difficult.

  Here, the rrrr of the racemic pentad fraction [rrrr / (1-mmmm)] is a side chain with respect to a main chain of carbon-carbon bonds composed of any five consecutive propylene units. This means a three-dimensional structure in which methyl groups are alternately positioned in the opposite direction or a proportion thereof, and mmmm is a side chain with respect to a main chain of carbon-carbon bonds composed of any five consecutive propylene units. This means a three-dimensional structure in which two methyl groups are located in the same direction or a proportion thereof.

  The racemic pentad fraction of the polypropylene resin (B) is 0.15 to 0.50, preferably 0.20 to 0.45. If this value is less than 0.15, the impact strength and transparency are insufficient, and the whitening at the time of bending worsens, and if it exceeds 0.50, the tensile elastic modulus becomes insufficient. From the viewpoint of the balance of characteristics of the transparent polypropylene sheet, the preferred rrrr / (1-mmmm) is in the range of 0.20 to 0.40.

The rrrr / (1-mmmm) is specifically a value measured as follows. That is, using JNM-FX-200 (manufactured by JEOL Ltd., ¹³ C-nuclear resonance frequency 50.1 MHz), measurement mode: complete proton decoupling method, pulse width: 6.9 μs (45 °), pulse repetition time: 3 s, cumulative number: 10,000 times, solvent: 1,2,4-trichlorobenzene / heavy benzene (90/10 vol%), sample concentration 250 mg / 2.5 ml solvent, measurement temperature: 130 ° C., ¹³ C-NMR measurement was performed, and the pentad fraction was measured from the difference in chemical shift due to the stereoregularity of the methyl group, that is, from the area intensity ratio of each mmmm to mrrm peak appearing in the 22.5 to 19.5 ppm region. , Rrrr / (1-mmmm) was determined.
mmmm: 21.86 ppm
mmr: 21.62 ppm
mmrr: 21.08 ppm
mmrm + rrmr: 20.89 ppm
rrrr: 20.36 ppm
mrrm: 19.97 ppm

  The resin composition having the above composition may be blended with 4% by weight or less of other known olefin-containing copolymers for sheet forming, known sheet forming additives, antistatic agents, and colorants. Etc. may be added.

  Through the molding process, the resin composition is molded into a sheet shape. As a melt extrusion method in the forming step, a T-die extrusion method is preferable. The shape of the sheet-shaped resin composition is once fixed by the cooling process. Examples of the cooling method in the cooling step include water cooling, air cooling, an endless belt, a roll, or the like.

By the heat treatment step, the surface of the resin composition once solidified into a sheet-like body can be finished finely. In this heat treatment step, heat treatment can be performed using an endless belt, a roll, or the like. By heat-treating the resin composition at 70 ° C. or higher and below the melting point of the polypropylene resin, the surface of the resin composition can be molded before it completely melts. The surface of the object can be finished finely, such as flat and mirrored.
Here, if it is less than 70 degreeC, a resin composition may become difficult to soften and surface finishing may become difficult. If it is higher than the melting point of the polypropylene resin, the resin composition may be completely melted and it may be difficult to perform the heat treatment process while maintaining the sheet shape.

  According to the present invention, the resin composition having the above composition is molded, cooled, and heat-treated to ensure transparency while providing impact resistance, rigidity, and secondary processing. A transparent polypropylene sheet without whitening during bending is obtained.

  In the manufacturing method of the transparent polypropylene sheet of this invention, it is preferable that the said cooling process cools the said sheet-like body by allowing the said sheet-like body to pass through the slit into which cooling water flows down.

  According to this, the cooling step allows the cooling water to be directly cooled with water while the sheet-like body passes through the slit by passing the sheet-like body through the slit through which the cooling water flows. The sheet-like body can be cooled and solidified without causing distortion or the like in the sheet shape of the body.

  In the method for producing a transparent polypropylene sheet of the present invention, the heat treatment step is carried out by sandwiching and heating the front and back surfaces of the sheet-like body with a metal endless belt and / or metal roll having a mirror surface. Is preferred.

  According to this, the heat treatment step is carried out by sandwiching the front and back surfaces of the sheet-like body with a metal endless belt and / or metal roll having a mirror surface, and heating the sheet-like body. Since the surface in contact with the mirror is a mirror surface, the surface of the sheet-like body can be mirror-finished.

  The transparent polypropylene sheet of the present invention has a (A) isotactic pentad fraction of 0.85 to 0.99 and a racemic pentad fraction [rrrr / (1-mmmm)] of less than 0.15 or 0. .50 and a melt index of 2 to 10 g / 10 minutes of polypropylene resin 60 to 97% by mass, and (B) racemic pentad fraction [rrrr / (1-mmmm)] of 0.15 to 0.50, And the isotactic pentad fraction is less than 0.85 or exceeds 0.99, the melt index is 2 to 10 g / 10 min of polypropylene resin 40 to 3% by mass, and the tensile in the extrusion direction (MD direction) When the elastic modulus is 1700 MPa or more and the sheet thickness is t [mm], the total haze H is

It is characterized by being within the range of the above formula.

  Here, the thickness of the transparent polypropylene sheet is 150 to 1000 μm, preferably 200 to 600 μm.

Further, the tensile elastic modulus can be measured by a method or the like based on JIS K7113. Here, if the tensile elastic modulus in the extrusion molding direction (MD direction) is less than 1700 MPa, it may not be practical in terms of strength.
The total haze H can be measured by a method based on JIS K7105. All haze H

If it is the following ranges of said formula, the transparent polypropylene sheet excellent in transparency can be obtained.

  According to the present invention, by comprising the polypropylene resin having the composition as described above, while ensuring transparency, it has impact resistance, rigidity, and whitening at the time of bending as secondary processing. There will be no transparent polypropylene sheet.

In the transparent polypropylene sheet of this invention, it is preferable that the impact strength in 5 degreeC is 2000 J / m or more, More preferably, it is 2000-3000 J / m.
Here, if the impact strength is less than 2000 J / m, the impact strength required for practical use such as packaging materials and clear files may not be satisfied.

  In the transparent polypropylene sheet of the present invention, the polypropylene resins (A) and (B) preferably do not contain a nucleating agent.

  According to this, since the nucleating agent has a nucleating effect that increases the crystallization speed, when it is reheated and molded, it is crystallized until it reaches a predetermined shape, and the shape is fixed. On the other hand, since the polypropylene resins (A) and (B) do not contain a nucleating agent, the moldability is not deteriorated.

  According to the present invention, it is possible to obtain a transparent polypropylene sheet having impact resistance and rigidity while ensuring transparency and having no whitening at the time of bending as secondary processing.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[First Embodiment]
FIG. 1 shows a transparent polypropylene sheet manufacturing apparatus 1 according to the first embodiment of the present invention.
The manufacturing apparatus 1 includes a sheet forming unit 11 that melts and kneads the raw material and extrudes it into a sheet, a first cooling unit 12 that cools and solidifies the sheet 20, a preheating unit 13 that reheats the cooled sheet 20, and a sheet 20 And a second cooling means 15 for cooling the sheet 21 after the heat treatment.

The sheet forming means 11 has an existing extruder 111 such as a single-screw extruder or a multi-screw extruder, for example, and a T-die 112 for forming a sheet is provided at the tip of the extruder 111.
By these, the melt-kneaded sheet composition is extruded from the T-die 112 and formed into a planar shape, and sheet forming is performed.

  In this sheet composition, (A) the isotactic pentad fraction is 0.85 to 0.99, and the racemic pentad fraction [rrrr / (1-mmmm)] is less than 0.15 or 0. .50 and a melt index of 2 to 10 g / 10 min of polypropylene resin 60 to 97% by mass, and (B) racemic pentad fraction [rrrr / (1-mmmm)] of 0.15 to 0.50, And it is a resin composition containing 40-3 mass% of polypropylene resins with an isotactic pentad fraction of less than 0.85 or exceeding 0.99 and a melt index of 2-10 g / 10 min.

Moreover, the form of the raw material made into a sheet composition is arbitrary, such as a powder, a granule, and a pellet form, and it mixes so that a sheet composition may become the said ratio.
The above resin composition may be blended with 4% by weight or less of other known olefin-containing copolymers for sheet molding, and known sheet molding additives, antistatic agents, and colorants. Etc. may be added, but a nucleating agent is not included.

  The first cooling means 12 includes a large water tank 120, a first roll 121 and a second roll 122 which are arranged opposite to each other in the large water tank 120 and sandwich the sheet 20, and the large water tank 120 than these rolls 121 and 122. A third roll 123 installed near the bottom of the large water tank, a fourth roll 124 provided near the periphery of the large water tank 120 on the preheating means 13 side, and a small water tank 125 disposed above the large water tank 120. Has been.

  As shown in FIG. 2, a slit 126 is formed at a position and a size corresponding to the opening of the T die 112 at the substantially central portion of the bottom surface of the small water tank 125. The slit 126 is formed perpendicular to the bottom surface of the small water tank 125, but may have a shape that decreases in diameter as it goes below the slit 126.

The space | interval of the slit 126 is 1-20 mm at the entrance side of the slit 126, Preferably it is 3-10 mm. On the other hand, at the exit side of the slit 126, it is at least thicker than the sheet 20, and is 0.5 mm or more, preferably 1.0 mm or more. In addition, the slit 126 is a wall-shaped thing normally about 1-10 mm in thickness and 30-70 mm in length. Furthermore, the distance between the slit 126 and the T die 112 is usually about 30 to 250 mm.
Although illustration is omitted, cooling water or the like for cooling the seat 20 can be continuously supplied into the small water tank 125 by a pump or the like from the outside.

  Thus, the sheet 20 formed by the forming means 11 flows down through the slit 126 together with the cooling water continuously supplied to the small water tank 125, and then the large water tank as the rolls 121, 122, 123 rotate. It is introduced into 120 and cooled and solidified.

The preheating means 13 is disposed at a position sandwiched between the preheating rolls 131 and 133 and the first and third preheating rolls 131 and 133 provided in parallel at substantially the same height, and is slightly shifted downward. The preheating roll 132 and the pressurizing auxiliary roll 134 whose peripheral surface is pressed and rolled by the third preheating roll 133 and sandwiches the sheet 20 from above and below.
In addition, the preheating rolls 131, 132, and 133 have built-in electric heaters and the like, and are heated so that their peripheral surfaces have a desired temperature.
Moreover, you may install the draining equipment between the 1st preheating roll 131 and the 4th roll 124 as needed.
As a result, the cooled and solidified sheet 20 is pressed against the peripheral surfaces of the preheating rolls 131, 132, and 133 and preheated.

  The heat treatment means 14 includes first, second, and third heating rolls 141, 142, and 143, a cooling roll 144, an endless belt 145, a pressure-contact auxiliary roll 146, and a peeling roll 147.

The first and second heating rolls 141 and 142 and the cooling roll 144 are provided in parallel at substantially the same height, and the third heating roll 143 is provided in parallel immediately below the heating roll 142.
The peripheral surfaces of the first to third heating rolls 141, 142, and 143 are each provided with an electric heater or the like, so that the temperature is 70 ° C. or more and the melting point of the polypropylene resins (A) and (B) (for example, about 175 ° C.) and heated, while the peripheral surface of the cooling roll 144 has a structure in which cooling water or the like circulates and is cooled to a desired temperature.

The endless belt 145 is wound around the first and third heating rolls 141 and 143 and the cooling roll 144 so as to be disposed inside. Thereby, the endless belt 145 is stretched in a state where it is pushed in from the outside to the inside by the second heating roll 142.
The endless belt 145 has a mirror-finished outer surface, and the thickness may be in the range of 0.1 to 3.0 mm, preferably 0.4 to 1.5 mm.
Further, the material of the endless belt 145 is preferably SUS301, SUS304, SUS316, or an equivalent material, and metals such as carbon copper and titanium can also be used.

The pressure auxiliary roll 146 is pressed and rolled from above the first heating roll 141 to the peripheral surface.
The peeling roll 147 peels the sheet 20 from the endless belt 145 and is provided in the vicinity of the cooling roll 144 with a predetermined interval.
As a result, the preheated sheet 20 is pressed against the endless belt 145 by the rotation of the heating rolls 141, 142, 143 and the cooling roll 144, heated to a desired temperature, and surface-molded.

The second cooling means 15 is provided in parallel at substantially the same height, and is pressed against the first, second, and third cooling rolls 151, 152, and 153 and the third cooling roll 153 that are cooled respectively. It is comprised with the press-contact auxiliary | assistant roll 154 which is moved and pinches | interposes the sheet | seat 20. As shown in FIG.
However, it is preferable that the peripheral surface temperature of the cooling rolls 151, 152, and 153 is lower than that of the cooling roll 144.
Thus, the surface-formed sheet 20 is brought into contact with the peripheral surfaces of the cooling rolls 151, 152, and 153, and is cooled while moving.

  In the present embodiment configured as above, first, the sheet forming means 11 extrudes the sheet composition from the T die 112 into a sheet shape to form the sheet 20 (forming step).

Next, the sheet 20 is introduced into the first cooling means 12 and cooled and solidified.
That is, the sheet 20 flows down through the slit 126 together with the cooling water constantly supplied to the small water tank 125, and then is guided into the large water tank 120 between the first roll 121 and the second roll 122. Between the large water tank 120 and the fourth roll 124. The sheet 20 is cooled and solidified while moving in the large water tank 120 (first cooling step).

Next, the cooled and solidified sheet 20 is introduced into the preheating means 13 and preheated to a predetermined temperature.
That is, the sheet 20 is guided from the fourth roll 124 to the upper peripheral surface of the first preheating roll 131, and above the third preheating roll 133 through the lower peripheral surface of the second preheating roll 132. It is sent to the peripheral surface and is sent out while being sandwiched by the pressure welding auxiliary roll 134.
The sheet 20 is meandered up and down in this manner and sufficiently pressed against the peripheral surfaces of the preheating rolls 131, 132, and 133, so that the sheet 20 is efficiently preheated uniformly to a predetermined temperature (preheating step).

Next, the preheated sheet 20 is introduced into the heat treatment means 14, and the surface is formed to be smooth.
That is, the sheet 20 is guided from the preheating roll 133 to the peripheral surface above the first heating roll 141, and is sandwiched and pressed together with the endless belt 145 by the pressure auxiliary roll 146, and is in close contact with the endless belt 145.
The sheet 20 is guided to the lower peripheral surface of the second heating roll 142 together with the endless belt 145, and is pressed against the endless belt 145 again by the second heating roll 142.

Subsequently, the sheet 20 is sent together with the endless belt 145 above the cooling roll 144, cooled by the cooling roll 144, guided to the peeling roll 147, and peeled from the endless belt 145.
As a result, the sheet 20 is sufficiently pressed against the mirror-finished endless belt 145 while being heated to 70 ° C. or higher and below the melting point of the resin composition. Obtained (heat treatment step).

Next, the surface-formed sheet 21 is introduced into the second cooling means 15 and cooled to a predetermined temperature.
That is, the sheet 21 is guided from the peeling roll 147 to the upper peripheral surface of the first cooling roll 151 and is sent to the third cooling roll 153 via the lower peripheral surface of the second cooling roll 152. And press-contacted by the press-contact auxiliary roll 154.
In this manner, the sheet 21 is sufficiently abutted against the cooling rolls 151, 152, and 153 to be cooled (second cooling step).
The transparent polypropylene sheet 21 of this embodiment is obtained by the above.

According to this embodiment as described above, the following effects are obtained.
(1) A transparent polypropylene sheet 21 having impact resistance and rigidity while ensuring transparency and having no whitening during bending as a secondary process is obtained.
(2) By heat-treating the sheet 20 as the resin composition at a temperature within the range of 70 ° C. or more and below the melting point of the resin composition, the surface can be molded before the resin composition is completely melted. Therefore, the surface of the resin composition can be finished finely, such as flattened or mirrored, while maintaining the sheet shape.

(3) In the first cooling step, the sheet 126 that is a sheet-like body is passed through the slit 126 through which the cooling water flows together with the cooling water, and the sheet 20 is cooled, so that the sheet 20 passes through the slit 126, Since the cooling water is directly water-cooled, the sheet 20 can be cooled and solidified without causing distortion or the like in the sheet shape of the sheet 20.
(4) The heat treatment step is performed by the endless belt 145 having a mirror surface sandwiching and heating the front and back surfaces of the sheet 20 that is a sheet-like body, whereby the surface that contacts the sheet 20 is a mirror surface. Therefore, the surface of the transparent polypropylene sheet 21 can be mirror-finished.
(5) Since the nucleating agent has a nucleating effect that accelerates the crystallization speed, when it is reheated and molded, it is crystallized until it reaches a predetermined shape, and the shape is fixed. On the other hand, since the polypropylene resins (A) and (B) do not contain a nucleating agent, the moldability is not deteriorated.

[Second Embodiment]
Next, a second embodiment of the present invention will be described. In the following description, the same parts and members as those already described are denoted by the same reference numerals and the description thereof is simplified.
With reference to FIG. 3, the manufacturing apparatus 2 of the transparent polypropylene sheet which concerns on 2nd Embodiment is demonstrated. In the manufacturing apparatus 1 of the first embodiment, the first cooling means 12 that cools and solidifies the sheet 20 includes the large water tank 120 and the small water tank 125 having the slit 126.

  On the other hand, in the manufacturing apparatus 2 of the second embodiment, the first cooling means 22 is a metal endless belt 215 wound between the first cooling roll 213 and the second cooling roll 214. A third cooling roll 216 that is in contact with the first cooling roll 213 via the sheet 20 and a metal endless belt 215, and a fourth roll 217 provided in the vicinity of the second cooling roll 214. It differs in that it is prepared.

  As indicated by a chain line in FIG. 1, another cooling roll 215A is provided in front of the first roll 213, and the endless belt 215 is further cooled by contacting it from the inside of the endless belt 215. Good.

The surface of the first cooling roll 213 is covered with an elastic material 218 such as fluororubber. The elastic material 218 has a hardness (conforming to JIS K6301 A type) of 60 degrees or less and a thickness of 3 mm or more.
The metal endless belt 215 is made of stainless steel or the like and has a mirror surface with a surface roughness of 0.5 S or less.
At least one of the first and second cooling rolls 213 and 214 has a rotation shaft 219 connected to a rotation driving means (not shown).

  The third cooling roll 216 also has a mirror surface with a surface roughness of 0.5 S or less. The cooling roll 216 is provided so as to come into contact with the first cooling roll 213 via the sheet 20 and the metal endless belt 215 and to hold the sheet 20 pressed to the cooling roll 216 side by the endless belt 215. It has been. That is, the metal endless belt 215 and the sheet 20 in contact with the endless belt 215 meander around the part of the peripheral surface of the third cooling roll 216.

The fourth roll 217 guides the sheet 20 so that the sheet 20 is pressed against the second cooling roll 214 via the endless belt 215.
Each of the cooling rolls 213, 214, and 216 is provided with a temperature adjusting means (not shown) such as a water cooling type that can adjust the surface temperature.

Similarly to the first embodiment, after performing the forming process using the sheet forming means 11, the sheet 20 is introduced into the first cooling means 22 and cooled and solidified.
Specifically, first, each of the cooling rolls 213, 214, 216 is maintained so that the surface temperatures of the endless belt 215 and the third cooling roll 216 that are in direct contact with the sheet 20 are kept at 50 ° C. or lower and above the dew point. Keep the temperature control.

  Then, the sheet 20 extruded from the T-die 112 of the extruder is contacted with the endless belt 215 that is in contact with the first cooling roll 213 and the third cooling roll 216 at approximately the same time. It introduce | transduces between the 3rd cooling rolls 213 and 216, the sheet | seat 20 is press-contacted with the 1st and 3rd cooling rolls 213 and 216, and it cools to 50 degrees C or less.

At this time, the elastic member 218 is compressed and elastically deformed by the pressing force between the first and third cooling rolls 213 and 216, and the elastic member 218 is elastically deformed from the center of both rolls 213 and 216. In the angle θ ₁ portion, the sheet 20 is in a planar pressure contact by both rolls 213 and 216. The surface pressure at this time is 0.1 MPa to 20.0 MPa.

Subsequently, the sheet 20 is pressed against the third cooling roll 216 with the mirror-like endless belt 215 and cooled to 50 ° C. or lower. The sheet 20 pressed toward the cooling roll 216 by the endless belt 215 is held by the cooling roll 216 at an angle θ ₂ from the center of the cooling roll 216, and the sheet 20 is endless belt 215 at the holding angle θ ₂ portion. And the third cooling roll 216 are press-contacted in a planar shape. The surface pressure at this time is 0.01 MPa to 0.5 MPa.

Next, the seat 20 is moved to the second cooling roll 214 along with the rotation of the endless belt 215 in a state where the seat 20 is overlapped with the endless belt 215, and the sheet 20 is moved to the second cooling roll via the endless belt 215. It is pressed against 214 and cooled to 50 ° C. or lower. The sheet 20 guided by the fourth roll 217 and pressed to the side of the cooling roll 214 is pressed into contact with the endless belt 215 in a plane at an angle θ ₃ portion from the center of the cooling roll 214. The surface pressure at this time is 0.01 MPa to 0.5 MPa (first cooling step).

Thereafter, as in the first embodiment, the sheet 20 is subjected to a preheating step by the preheating means 13, a heat treatment step by the heat treatment means 14, and a second cooling step by the second cooling means 15 to obtain a transparent polypropylene sheet.

According to the present embodiment as described above, in addition to the effects of the first embodiment described above (excluding (3)), the following effects are obtained.
(6) Sheet pressure contact and cooling of the sheet 20 by both rolls 213 and 216 at the angle θ ₁ portion of the first and third rolls 213 and 216 where the elastic material 218 is elastically deformed, and metal at the holding angle θ ₂ portion The sheet 20 is pressed and cooled by the endless belt 215 and the third cooling roll 216, and the sheet 20 is pressed and cooled by the endless belt 215 and the second cooling roll 214 at the angle θ ₃ portion. The sheet 20 can be manufactured at a high speed.

It should be noted that the present invention is not limited to the above-described embodiments, and modifications and improvements as long as the object of the present invention can be achieved are included in the present invention. For example, as the heat treatment step, the endless belt 145 is used in each of the above embodiments, but the heat treatment step is not limited to this, and the heat treatment step may be performed with a metal roll or the like.
In addition, the specific structure, shape, and the like when carrying out the present invention may be other structures and the like as long as the object of the present invention can be achieved.

Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. In addition, this invention is not limited to the content of the Example.
Using the production apparatus 1 (see FIG. 1) of the first embodiment, a transparent polypropylene sheet 21 was produced under specific conditions as described below and in Table 1.

Polypropylene resin (A)
HPP-1 (homopolypropylene): isotactic pentad fraction 0.90
: MI 3.0 g / 10 min HPP-2 (homopolypropylene): Isotactic pentad fraction 0.92
: MI 2.0g / 10min

Polypropylene resin (B)
TPO (Thermo Plastic Olefin elastmer)
: Racemic pentad fraction [rrrr / (1-mmmm)] 0.24
: Isotactic pentad fraction 0.76
: MI 2.8 g / 10 min: Melting point [measured by DSC method] 158.7 ° C.
: Enthalpy of melting [ΔH] 81 J / g

The above-mentioned isotactic pentad fraction and racemic pentad fraction [rrrr / (1-mmmm)]) are specifically measured as follows. That is, using JNM-FX-200 (manufactured by JEOL Ltd., ¹³ C-nuclear resonance frequency 50.1 MHz), measurement mode: complete proton decoupling method, pulse width: 6.9 μs (45 °), pulse repetition time: 3 s, cumulative number: 10,000 times, solvent: 1,2,4-trichlorobenzene / heavy benzene (90/10 vol%), sample concentration 250 mg / 2.5 ml solvent, measurement temperature: 130 ° C., ¹³ C-NMR measurement was performed, and the pentad fraction was measured from the difference in chemical shift due to the stereoregularity of the methyl group, that is, from the area intensity ratio of each mmmm to mrrm peak appearing in the 22.5 to 19.5 ppm region. , Rrrr / (1-mmmm) was determined.
mmmm: 21.86 ppm
mmr: 21.62 ppm
mmrr: 21.08 ppm
mmrm + rrmr: 20.89 ppm
rrrr: 20.36 ppm
mrrm: 19.97 ppm

Random polypropylene RPP: ethylene content 3wt%
: MI 5.0g / 10min

Linear low density polyethylene LLDPE: Density 907kg / m3
: MI 3.0g / 10min

Resin composition temperature: 240 ° C.
Temperature near the opening of the T-die 112: 280 ° C
Temperature of preheating rolls 131, 132, 133 in the preheating process: 110 ° C.
Temperature of heating rolls 141, 142, 143 in the surface forming process: 145 ° C
Endless belt 145 lap speed: 15-25 m / min

  Here, each characteristic of the completed transparent polypropylene sheet 21 was evaluated. The evaluation results are shown in Table 1. The tensile elastic modulus was measured by a method based on JIS K7113. Note that TD means a direction perpendicular to the MD direction (the direction of molding extrusion).

All haze and internal haze were measured using a haze measuring machine (manufactured by Nippon Denshoku Industries Co., Ltd.) in accordance with JIS K7105. The glossiness was measured using an automatic colorimetric color difference meter (manufactured by Suga Test Instruments Co., Ltd.) in accordance with JIS K7105.
The impact strength was measured at 23 ° C., 5 ° C., and −5 ° C. using a film impact tester (Toyo Seiki Seisakusho Co., Ltd.) under the conditions of a test load of 30 kg and a 1 inch head. In addition, NB in Table 1 is a measurement limit value of 10000 J / m, and indicates that no material destruction occurred during measurement.

Further, the whitening property of the resulting transparent polypropylene sheet 21 when folded was also evaluated.
(Double-circle): It does not whiten.
◯: Mild whitening, visible to the naked eye.
Δ: Whitening can be confirmed with the naked eye.

  As can be seen from Table 1, Examples 1 to 1 containing the polypropylene resin (B) are contained, as compared with Comparative Examples 1 and 2 containing RPP and LLDPE without containing the polypropylene resin (B). It can be seen that No. 3 is a transparent polypropylene sheet having impact resistance and rigidity while ensuring transparency and having no whitening at the time of bending as secondary processing.

It is the schematic which shows the manufacturing apparatus of 1st Embodiment of this invention. It is the elements on larger scale of the small water tank in embodiment of FIG. It is the schematic which shows the manufacturing apparatus of 2nd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 2 Manufacturing apparatus 11 Sheet forming means 12, 22 Cooling means 14 Heat treatment means 20 Sheet 21 Transparent polypropylene sheet 111 Extruder 112 T die 120 Large water tank 125 Small water tank 126 Slit 141, 142, 143 Heating roll 144 Cooling roll 145 Endless belt 213, 214, 216 Cooling roll 215 Endless belt 215A Cooling roll 216 Cooling roll

Claims (6)

(A) The isotactic pentad fraction is 0.85 to 0.99, the racemic pentad fraction [rrrr / (1-mmmm)] is less than 0.15 or more than 0.50, and the melt index is 60 to 97% by mass of polypropylene resin of 2 to 10 g / 10 min, (B) racemic pentad fraction [rrrr / (1-mmmm)] of 0.15 to 0.50, and isotactic pentad content A molding step of melting and extruding a resin composition containing 40 to 3% by mass of a polypropylene resin having a rate of less than 0.85 or exceeding 0.99 and having a melt index of 2 to 10 g / 10 min;
A cooling step of rapidly cooling the melt-extruded sheet,
A method for producing a transparent polypropylene sheet, comprising: a heat-treating step of heat-treating the cooled sheet-like body at 70 ° C. or higher and below the melting point of the polypropylene resin. In the manufacturing method of the transparent polypropylene sheet of Claim 1,
The said cooling process cools the said sheet-like body by allowing the said sheet-like body to pass through the slit where cooling water flows down, The manufacturing method of the transparent polypropylene sheet characterized by the above-mentioned. In the manufacturing method of the transparent polypropylene sheet of Claim 1 or Claim 2,
The method for producing a transparent polypropylene sheet is characterized in that the heat treatment step is carried out by sandwiching and heating the front and back surfaces of the sheet-like body with a metal endless belt and / or metal roll having a mirror surface. (A) The isotactic pentad fraction is 0.85 to 0.99, the racemic pentad fraction [rrrr / (1-mmmm)] is less than 0.15 or more than 0.50, and the melt index is 60 to 97% by mass of polypropylene resin of 2 to 10 g / 10 min, (B) racemic pentad fraction [rrrr / (1-mmmm)] of 0.15 to 0.50, and isotactic pentad content The rate is less than 0.85 or more than 0.99, and the melt index is 2 to 10 g / 10 min.
The tensile elastic modulus in the extrusion molding direction (MD direction) is 1700 MPa or more,
If the sheet thickness is t [mm], the total haze H is

A transparent polypropylene sheet characterized by: In the transparent polypropylene sheet according to claim 4,
A transparent polypropylene sheet having an impact strength at 5 ° C. of 2000 J / m or more. In the transparent polypropylene sheet according to claim 4 or 5,
The said polypropylene resin (A) and (B) does not contain a nucleating agent, The transparent polypropylene sheet characterized by the above-mentioned.

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