KR0148775B1 - Propylene resin sheet - Google Patents

Abstract

The present invention relates to a propylene resin sheet and a method for producing the same. The propylene resin sheet prepared according to the method of the present invention has a β crystal content of 10 to 50% of the total crystal structure, and has a haze of 1 to 5%, a light transmittance of 90 to 95%, and a glossiness of 120 to 95%. Very transparent as 150%. In addition, the processability is excellent, and manufacturing is easy.

Description

Propylene Resin Sheet and Manufacturing Method Thereof

1 is a graph showing the diffraction intensity of a polypropylene sheet measured using an X-ray diffractometer.

2 is a block diagram of an apparatus for manufacturing a thermoplastic resin sheet according to an embodiment of the present invention.

3 is a view showing the interior of the extruder subdivided according to temperature.

* Explanation of symbols for main parts of the drawings

1: Extruder 2: Hopper

3: extruder 4: drive motor

5: T-die 11, 12: cooling roll

13: Heating roll 14: steel valve

15: nip roll 16: drive motor

20: static elimination device 30: annealing device

31: Roll 40: Roll up roll

The present invention relates to a transparent propylene resin sheet having a good post-processing property and a method for producing the same. Specifically, the propylene resin sheet has a uniform thickness, embossing, corona discharge treatment, and coating treatment, and particularly excellent transparency. And a method for producing the same.

Even in the active research on various plastic packaging materials, polyolefin resins that are light and harmless and can be used for various purposes have been spotlighted as general purpose resins. Among them, polypropylene has a density of 0.90 to 0.92 g / cm 3, which is the lightest and most transparent plastic among general purpose plastics. It is excellent in heat resistance, electrical insulation, chemical resistance, flex resistance and post-processing, and is harmless. The range of use and the amount of is increasing rapidly.

On the other hand, since polyvinyl chloride is very transparent and inexpensive, it has been widely used as a packaging substrate for food, daily necessities, medicines, etc., and its use is regulated because harmful gases generated during incineration cause serious pollution problems. Therefore, transparent and harmless polymer resins are being considered as a replacement for polyvinyl chloride. In particular, the use of propylene-based resin has been proposed, and the sheet made of such a resin has a disadvantage in that it does not have a transparency similar to that of polyvinyl chloride, and thus there is a limit to extending its use to polyvinyl chloride. It is becoming. Therefore, various methods for producing a highly transparent propylene resin sheet have been devised, and the present invention relates to this.

The transparency of thermoplastic sheets, such as polypropylene resins, is related to several factors, which are generally determined by the type of crystals, the crystal size and the degree of crystallization. In particular, the crystallization occurs in the process of melting and extruding the thermoplastic resin at high temperature and then cooling it, and is determined according to the structural characteristics of the polymer itself and the molding conditions of the sheet in this regard.

On the other hand, the manufacturing method of the thermoplastic resin sheet is melted and extruded the thermoplastic resin chip through the tee-die to form a molten sheet, and the molded sheet is subjected to a process of solidifying by a cooling roll installed below the die. It is common.

Moreover, as a method of crimping a molten sheet to a roll in the manufacturing process of a thermoplastic resin sheet, there exist an air knife method and a polishing roll method. Among them, the air knife method utilizes the air pressure ejected from the air nozzle to press the melt sheet extruded from the tee die onto the roll. This method is widely used when forming sheets that do not care about appearance, such as transparency. The thickness variation is large, it is difficult to obtain a transparent sheet, and the production speed cannot be more than 20 m / minute, and a sheet having a thickness of 500 μm or more can be obtained. There is a problem that can not be.

The polishing roll method, which is another method, compresses the melt sheet extruded from the tee die at the tangential portion of the metal roll, and is mainly used to produce sheets having a thickness of 400 μm or more with embossing or gloss. However, in this method, the pressing time is short, and it is impossible to set the molding speed to 5 m / min or more, and it is difficult to quench the high-transparency sheet because it needs to be operated at a high temperature in order to give a shape to the sheet surface.

As such, according to the conventional method, there is a disadvantage that a sheet having a nonuniform thickness or an opacity is obtained and its manufacturing speed is slow. In particular, transparency is a property necessary for use as a substitute for polyvinyl chloride, and it is common that the polymer sheet is opaque at a higher crystal speed.

On the other hand, since the degree of crystallinity of the sheet is proportional to the cooling time of the melt sheet, methods for rapidly cooling the melt sheet extruded from the die have been devised to obtain a transparent sheet such as polyvinyl chloride.

Japanese Laid-Open Patent Publication No. 58-203018 discloses a multi-stage slit method of quenching a cooling water by flowing a cooling water in a melt sheet and a method of quenching a molten resin extruded from a T-die into a cooling water tank immediately. However, the multi-slit slit method has a limited cooling effect, which does not have a significant effect on improving transparency, and has a problem of poor surface uniformity. The quenching method of the cooling water tank has a large variation in sheet thickness and streaks on the surface. There are disadvantages.

It is therefore an object of the present invention to solve the above problems and to provide a method for producing a propylene resin sheet having a uniform thickness, good appearance, and very transparent.

In order to achieve the above another object, in the present invention,

Melting and kneading the propylene resin chip through an extruder;

Melting and kneading the resin in the step is extruded through a die to form a molten sheet; And rapidly melting and solidifying the melt sheet, wherein the propylene resin chip has a melt index of 1 to 20 (g / 10 minutes) and a melting temperature of 130 to 170. Rapid cooling and solidification of the molten sheet is carried out by fastening and rotating the first cooling roll, the second cooling roll and the heating roll at positions corresponding to the vertices of the triangle and being cooled by the first cooling roll. The molten sheet is injected and attached between a steel belt and a nip roll positioned opposite to the first cooling roll with respect to the steel belt; In the state attached to the steel belt is transported along the bottom side of the triangle, and then passing through the second cooling roll portion is provided a method characterized in that it is made.

Another object of the present invention is to provide a propylene resin sheet having a uniform thickness, good appearance, and very transparent.

In order to achieve the above another object, the present invention provides a propylene resin sheet which is prepared according to the above method, wherein the β crystal content is 10 to 50% of the total crystal structure.

In the present invention, the content of β crystal structure in the crystal structure present in the polypropylene sheet is characterized in that a certain range. That is, the polypropylene sheet has a crystal structure roughly divided into a monoclinic α crystal structure and a hexagonal β crystal structure (see FIG. 1). The double β crystal structure is related to surface roughness and transparency. Therefore, a highly transparent sheet can be obtained when the β crystal content of the entire crystal structure is calculated by the same method as in the following formula.

However, the larger the K value, the more transparent the sheet becomes.

Hereinafter, the present invention will be described in detail through a specific method for preparing a polymer sheet.

2 is a block diagram of an apparatus for manufacturing a propylene resin sheet according to an embodiment of the present invention.

First, the propylene resin chip is put into the extruder 3 through the hopper 2. The extruder 3 incorporates a screw (not shown) that is rotated by the drive motor 4, so that the temperature rises as it proceeds toward the tee-die at the chip inlet. That is, there is raised gradually to a temperature (T _f) of the portion where the resin is melt-extruded at a temperature (T _i) of a portion which the chip is turned on (see also FIG. 3), in particular temperature T _f is 200 to 280 ℃, The rotational speed of the screw is preferably 40 to 120 (times / minute). This is because when the temperature of the molten resin extruded from the T-die is less than 200 ° C., the resin coagulates and the extrusion state is poor. In addition, when the screw rotation speed is less than 40rpm, not only is the load on the screw shaft too high, but also it is difficult to sufficiently mix the molten resin, and if the screw speed is greater than 120rpm, the discharge amount is too large.

The propylene resin chips introduced into the extruder under such conditions are melted while being sufficiently kneaded and dispersed, and are compressed at high temperature. The hot compressed molten resin is extruded through the tee-die 5, molded into a molten sheet, and sent to the cooling apparatus 10.

The molten sheet extruded from the tee die is attached to the steel belt 14 as it enters between the steel belt 14 and the nip roll 15 on the first cooling roll 11, and in the attached state, the triangle-shaped bottom After being transported along the portion, the second cooling roll 12 passes through the cooling apparatus 10. In this case, the temperature of the steel belt 14 is preferably 100 to 150 ℃, which is less than 100 ℃ in the roll and the sheet is not adhered well surface layer is not formed, in the case of more than 150 ℃ to quench the melt sheet Because it is difficult to make.

On the other hand, as can be seen in FIG. 2, the cooling apparatus 10 includes a first cooling roll 11, a second cooling roll 12, a heating roll 13, three of which are driven by a motor 16. It consists of the steel belt 14 and the nip roll 15 which rotate on the rolls 11, 12, and 13 of this.

Here, the nip roll 15 serves to form the extruded melt sheet to a certain thickness and to uniformly cool the same, and to keep the surface temperature at 15 to 40 ° C. by circulating the cooling water therein.

The first cooling roll 11 is coated on the surface of the steel belt 14 with a circular rubber band in order to prevent the deterioration of the steel belt 14, and serves to suppress the formation of spherical crystals by rapidly cooling the melt sheet.

The second cooling roll 12 cools the steel belt 14 to serve to easily detach the sheet conveyed by being attached to the steel belt 14.

In addition, the heating roll 13 is to reheat the steel belt 14, so that the melt sheet extruded from the tee-die enters between the first cooling roll 11 and the nip roll 15 to be completely in contact with the steel belt (14). It works.

Passing through the cooling device 10, the cooled and solidified sheet is passed through the static electricity removing device 20 to remove the static electricity on the surface. Finally, it is slowly cooled completely through an annealing unit 30 having a plurality of rolls 31 intersecting up and down, and then wound on a take-up roll 40 to obtain high transparency polypropylene. A resin sheet is produced.

On the other hand, the propylene resin usable in the present invention includes a copolymer with polypropylene or other olefins. The propylene copolymer has a melt index of 1 to 20 (g / 10 minutes) and a melting temperature of 130 to 170 ° C., but the composition ratio is 95 to 99 mol% of propylene, preferably an olefin other than the remaining propylene. . Examples of preferred copolymers include propylene-ethylene copolymers, propylene-butene copolymers, propylene-ethylene-butene copolymers, and the like.

In addition, in the propylene-based resin, known additives such as antistatic agents, dispersants, electrostatic agents, slip agents, nucleating agents, and various pigments may be added at low temperature without impairing the effects of the present invention.

Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples, but the present invention is not necessarily limited thereto.

The following methods were used for the various performance evaluation of the film manufactured in the Example and comparative example of this invention.

1) β crystal content (K value)

The diffraction intensity was measured using an X-ray diffractometer (model name: D-MAX3C) manufactured by PKGAKU (Japan), and then calculated according to the above formula (I).

2) haze

Using a Hadometer of Gardner Neotax (USA), the scattered light and transmitted light values were measured using a C-light source and calculated according to the following equation.

3) light transmittance

Scattered light, transmitted light and total generated light were measured using a C-light source using a light transmittance measuring instrument of Gardner Neotek Co., Ltd. (measured diameter: 25 mm, scattering angle). : 2.5 degrees)

4) glossiness

It was measured using a glossiness gauge (model name: GC-4010) of Gardner Neotek Co., Ltd. (USA, reference diameter: black diameter, measuring angle: 60 degrees).

5) tear strength

The load applied per unit length during tearing was measured using a tear tester (model name: Heavy Duty Elmendorf) of THING-ALVENT INSTRUMENTS (USA).

6) filter pressure

During melt extrusion, the pressure applied to the filter housing combined with three screen filters, 40, 60 and 80 mesh, respectively, was measured.

7) Fairness

It was determined by the adhesion of the melt-extruded resin to the steel belt.

Example 1

While maintaining the outlet temperature of the extruder at 220 ° C. and the slew rotation speed of 80 rpm, the melt polypropylene resin having a melt index of 4 (g / 10 min) and a melting point of 155 ° C. was melt-compressed by 270 kg per hour. Subsequently, under the condition that the rotation speed of the steel belt is 20 (m / min) and the temperature of the nip roll is maintained at 30 ° C., the melt sheet extruded from the T-die is cooled and solidified. To prepare a polypropylene sheet.

Various physical properties of the prepared sheet were measured, and the quality was excellent as K value 35%, haze 1.8%, light transmittance 95%, glossiness 135%, tear strength 420g / cm, and the processability was also very good.

Example 2-5

As shown in Table 1, the polypropylene resin sheet was prepared while the conditions were changed within the scope of the present invention, and the physical properties thereof were measured. Fairness was also excellent overall.

[Comparative Example 1-6]

The physical properties of the polypropylene resin sheet were prepared in the same manner as in Example 1, except that at least one or more conditions of the extruder temperature, the scour speed, and the nip roll temperature were outside the scope of the present invention. As can be seen from Table 1, when the sheet is prepared by deviating from the conditions of the present invention, the physical properties of the film are poor or the processability is poor.

As can be seen from the above, the polypropylene resin sheet produced according to the method of the present invention has excellent tear strength and uniform thickness, in particular, haze of 1 to 5%, light transmittance of 90 to 95%, glossiness 120-150%, very transparent. In addition, the processability is excellent, and manufacturing is easy.

Claims (9)

Melting and kneading the propylene resin chip through an extruder; Melting and kneading the resin in the step is extruded through a die to form a molten sheet; And rapidly melting and solidifying the melt sheet, wherein the propylene resin chip has a melt index of 1 to 20 (g / 10 minutes) and a melting temperature of 130 to 170. Rapid cooling and solidification of the molten sheet is carried out by fastening and rotating the first cooling roll, the second cooling roll and the heating roll at positions corresponding to the vertices of the triangle and being cooled by the first cooling roll. Injecting the molten sheet between the steel belt and the nip roll positioned opposite to the first cooling roll with respect to the steel belt, and attaching the molten sheet; In the state attached to the steel belt is transported along the bottom side of the triangle, and then passing through the second cooling roll portion characterized in that it is made through the step. The method for producing a propylene resin sheet according to claim 1, wherein the propylene resin is homo polypropylene. The method for producing a propylene resin sheet according to claim 1, wherein the propylene resin is a copolymer of propylene with at least one olefin selected from the group consisting of ethylene and butene. The method for producing a propylene resin sheet according to claim 3, wherein the content of the propylene monomer is 95 to 99 mol% with respect to the propylene resin. The method for producing a propylene resin sheet according to claim 1, wherein in the step of melting and kneading the propylene resin chip, the screw rotation speed in the extruder is 40 to 120 (times / minute). The method for producing a propylene resin sheet according to claim 1, wherein the temperature of the melt sheet extruded through the die is 200 to 280 ° C. The method of claim 1, wherein the temperature of the steel belt is maintained in the range of 100 to 150 ℃. The method of claim 1, wherein the surface temperature of the nip roll is maintained in the range of 15 to 40 ℃ propylene-based resin sheet production method. A propylene-based resin sheet prepared according to any one of claims 1 to 8, wherein the β-crystal content is 10 to 50% of the total crystal structure.