KR102093566B1 - Polypropylene resin composition for a heat shrinkable blown film and heat shrinkable blown film prepared therefrom - Google Patents

Abstract

According to an embodiment of the present invention, a polypropylene resin composition comprising a terpolymer of ethylene/propylene/1-α-olefin is provided. The polypropylene resin composition is not only excellent in processability, but also excellent in transparency, adhesion properties, and shrinkage properties of films prepared through a double bubble film process, thereby being suitable for use as a heat-shrinkable film.

Description

Polypropylene resin composition for a heat shrinkable blown film and a heat shrinkable blown film produced therefrom {Polypropylene resin composition for a heat shrinkable blown film and heat shrinkable blown film prepared therefrom}

The present invention relates to a polypropylene resin composition for a heat-shrinkable blown film. In detail, the present invention is excellent in processability, polypropylene resin composition for a heat-shrinkable blown film having improved transparency, adhesion properties, and shrinkage properties, etc., and a double bubble film process produced therefrom. It relates to a heat shrinkable blown polypropylene film.

A heat-shrinkable film is a film having a property of being contracted in a form before stretching after being oriented and stretched at a predetermined temperature or more, and is widely used for labels, packaging and sealing.

Polyvinyl chloride (PVC) -based films, stretched polystyrene (OPS) -based films, and polyester-based films have been used as such heat-shrinkable films. However, PVC-based heat-shrinkable films have a problem in that dioxins are harmful to the human body upon incineration, OPS-based heat-shrinkable films have insufficient heat resistance, and polyester-based heat-shrinkable films may deform when heat-shrinked.

On the other hand, as a polypropylene-based heat-shrinkable film, Japanese Patent Application Publication No. 2006-052313 is obtained by homopolymerization of propylene in the presence of a metallocene catalyst or by copolymerization of α-olefin having 2 to 20 carbon atoms except propylene and propylene. , n-decane soluble component is disclosed as a (co) polymer for a heat-shrinkable film having 3% by weight or less. However, this polypropylene-based resin composition did not provide a heat-shrinkable film having excellent transparency, adhesion properties, and shrinkage properties.

In addition, Korean Patent Application Publication No. 2006-0052988 discloses a polypropylene random copolymer obtained by using ethylene and an α-olefin having 2 to 20 carbon atoms as a comonomer. However, this polypropylene-based resin composition also failed to provide a heat-shrinkable film having excellent transparency, adhesive properties, and shrinkage properties.

Japanese Patent Application Publication No. 2006-05231 Republic of Korea Patent Application Publication No. 2006-0052988

Accordingly, an object of the present invention is to provide a polypropylene resin composition for a heat-shrinkable blown film having not only excellent processability but also improved transparency, adhesion properties, and shrinkage properties.

Another object of the present invention is to provide a heat-shrinkable blown polypropylene film excellent in transparency, adhesion properties, and shrinkage properties.

According to one embodiment of the present invention for achieving the above object, as a polypropylene resin composition for a heat-shrinkable blown film comprising a terpolymer of ethylene / propylene / 1-α- olefin, the ethylene in the terpolymer The content is more than 1.5% by weight and less than 5.0% by weight, and the content of 1-α-olefin exceeds 3.5% by weight, but the content of ethylene (A weight%) and the content of 1-α-olefin (B weight%) is as follows. Satisfying Equation 1:

[Equation 1]

8.0 <2 * A + B <15.0

The content of the solvent extract in this ternary copolymer is 5.0 to 20.0% by weight, the melt index is 3.0 to 6.5 g / 10 minutes when measured at 230 ° C under a 2.16 kg load, the melting temperature (Tm) is 135 ° C or less, and heat shrinkage A polypropylene resin composition for a heat-shrinkable blown film is provided, wherein the sex-blown film has a shrinkage of 50 to 70% and a haze of 2.0% or less.

Preferably, the 1-α-olefin may be one or more selected from the group consisting of 1-butene, 1-pentene, 1-hexene, 1-heptene and 1-octene. Most preferably, the 1-α-olefin is 1-butene.

The polypropylene resin composition according to an embodiment of the present invention is one type selected from the group consisting of antioxidants, slip agents, anti-blocking agents, processing lubricants, reinforcing materials, fillers, weathering stabilizers, antistatic agents, nucleating agents, flame retardants, pigments and dyes The additive may be further included.

Specifically, the polypropylene resin composition according to an embodiment of the present invention, tetrakis (methylene (3,5-di-t-butyl-4-hydroxy) hydrosilylate), 1, with respect to 100 parts by weight of the composition At least one member selected from the group consisting of 3,5-trimethyl-tris (3,5-di-t-butyl-4-hydroxy benzene) and tris (2,4-di-t-butylphenyl) phosphite Antioxidants may further include 0.05 to 0.2 parts by weight.

In addition, the polypropylene resin composition according to an embodiment of the present invention may further include 0.05 to 0.5 parts by weight of an amide-based slip agent with respect to 100 parts by weight of the composition.

In addition, the polypropylene resin composition according to an embodiment of the present invention may further include 0.05 to 0.5 parts by weight of at least one anti-blocking agent selected from the group consisting of porous silica, zeolite, and combinations thereof with respect to 100 parts by weight of the composition. have.

According to another embodiment of the present invention, there is provided a heat-shrinkable blown polypropylene film prepared from the above polypropylene resin composition through a double bubble film process.

The heat-shrinkable blown polypropylene film according to an embodiment of the present invention has a shrinkage of 50-70% and a haze of 2.0% or less.

The polypropylene resin composition according to an embodiment of the present invention is not only excellent in processability, but also the film produced through the double bubble film process has improved transparency, adhesion properties and shrinkage properties, and thus is suitable for use as a heat-shrinkable film. Do.

Hereinafter, the present invention will be described in more detail.

The polypropylene resin composition for a heat-shrinkable blown film according to an embodiment of the present invention includes a terpolymer of ethylene / propylene / 1-α-olefin, and the content of ethylene in the terpolymer is more than 1.5% by weight 5.0 Less than 1% by weight, the content of 1-α-olefin exceeds 3.5% by weight, but the content of ethylene (A% by weight) and the content of 1-α-olefin (B% by weight) satisfies Equation 1 below:

[Equation 1]

8.0 <2 * A + B <15.0

The content of the solvent extract of this ternary copolymer is 5.0 to 20.0% by weight, the melt index is 3.0 to 6.5 g / 10 minutes when measured at 230 ° C under a 2.16 kg load, and the melting temperature (Tm) is 135 ° C or less.

The polypropylene resin composition according to an embodiment of the present invention includes a terpolymer of ethylene / propylene / 1-α-olefin.

The content of ethylene in the terpolymer of this ethylene / propylene / 1-α-olefin is more than 1.5% by weight and less than 5.0% by weight, preferably 2.0 to 4.5% by weight. If the content of ethylene is 1.5% by weight or less, the crystallinity of the film is high and shrinkage characteristics are deteriorated, which may not be suitable as a shrinkage film. If the content of ethylene is 4.5% by weight or more, the content of xylene solvent extract is high, so die build-up may occur, and the sticky properties are strong, preventing sticking to each other during film storage and blocking. Problems may arise. In addition, the soft properties of the film may be so strong that it may be difficult to use as a shrink film.

The 1-α-olefin in the terpolymer of ethylene / propylene / 1-α-olefin may have 4 to 8 carbon atoms. Specifically, the 1-α-olefin may be at least one selected from the group consisting of 1-butene, 1-pentene, 1-hexene, 1-heptene and 1-octene, and 1-butene is most preferred.

The content of 1-α-olefin in the terpolymer of ethylene / propylene / 1-α-olefin is more than 3.5% by weight, preferably 4.0 to 5.5% by weight. When the content of 1-α-olefin is 3.5% by weight or less, the crystallinity of the film is high and the shrinkage property is deteriorated, which may not be suitable as a shrinkage film.

Here, the ethylene content (A wt%) and the content of 1-α-olefin (B wt%) in the terpolymer of ethylene / propylene / 1-α-olefin satisfy Equation 1 below:

[Equation 1]

8.0 <2 * A + B <15.0.

Preferably, the ethylene content (A weight%) and the content of 1-α-olefin (B weight%) in the terpolymer of ethylene / propylene / 1-α-olefin satisfies Equation 1a below:

[Equation 1a]

8.5 <2 * A + B <13.5.

When the ethylene content (A weight%) and the content of 1-α-olefin (B weight%) in the terpolymer of ethylene / propylene / 1-α-olefin satisfy the above equation (1), a heat-shrinkable film produced therefrom The transparency, adhesion properties and shrinkage properties of can be improved.

On the other hand, the content of the solvent extract in the terpolymer of ethylene / propylene / 1-α-olefin is 5.0 to 20.0 wt%, preferably 6.0 to 18.0 wt%. At this time, xylene is preferred as a solvent for measuring the solvent extract. Exceeding the upper limit of this range is not preferable because the excessive dispersed phase may aggregate to deteriorate the mechanical properties of the film.

In addition, the terpolymer of ethylene / propylene / 1-α-olefin has a melt index of 3.0 to 6.5 g / 10 min when measured at 230 ° C. under a load of 2.16 kg according to ASTM D1238, and preferably 5.0 to 6.0 g / 10 minutes. If the melt index of the ternary copolymer is less than 3.0 g / 10 min, the extruder is heavily loaded during film processing, which may cause problems in productivity and processability. On the other hand, when the melt index exceeds 6.5 g / 10 min, the load on the extruder is reduced, but the melt strength is lowered, resulting in a tube-shaped resin coming out of a ring die from the extruder. The film may explode or stretch during the process of being transferred to the air blow equipment that is expanded by the air pressure or the process of stretching in the air blow equipment, and processing may not be properly performed. In addition, mechanical properties such as tensile strength of the heat-shrinkable blown film produced from this composition may be deteriorated, which is not preferable.

Further, the melting temperature (Tm) of the terpolymer of ethylene / propylene / 1-α-olefin is 135 ° C. or less, preferably 120 to 135 ° C. If the melting temperature exceeds 135 ° C, the heat-sealing properties of the film may be poor, or processing may be required at high temperatures during heat sealing, which may cause processing difficulties. On the other hand, if the melting temperature is too low, heat shrinkage may occur in the storage process and blocking of the film may occur, which is not preferable.

There is no particular limitation on a method for preparing a terpolymer of ethylene / propylene / 1-α-olefin, which is a main component of a polypropylene resin composition according to an embodiment of the present invention, and the polypropylene polymer known in the art to which this invention belongs The manufacturing method may be used as it is or as appropriately modified.

For example, a bulk polymerization method, a solution polymerization method, a slurry polymerization method, a gas phase polymerization method, or the like can be used, and either a batch type or a continuous type is possible. Moreover, you may combine these polymerization methods, and a continuous-phase gas phase polymerization method is preferable from an economic viewpoint.

Specifically, Mitsui's Hypol manufacturing process, in which three bulk reactors and one gas phase reactor are connected in series, one loop having two reaction zones (Liondellbasell's Spherizone manufacturing process in which a loop reactor and one gas phase reactor are connected in series, or two tubular reactors and one gas phase reactor in series) The ternary copolymer of ethylene / propylene / 1-α-olefin may be prepared using a connected Lyondellbasell manufacturing process such as Spheripol, but is not limited thereto.

When a ternary copolymer of ethylene / propylene / 1-α-olefin is prepared by using any one of the manufacturing processes listed above, ethylene, propylene and 1-α-olefin are supplied to each reactor in a desired content and polymerized. A desired terpolymer of ethylene / propylene / 1-α-olefin can be prepared. At this time, the melt index of the resulting copolymer can be controlled by injecting hydrogen into each reactor.

In the polymerization process of each of the above reactors, the catalysts known in the art can be used without limitation, but it is preferable to use a Ziegler-Natta catalyst. At this time, the catalyst is prepared by reacting a titanium compound such as titanium chloride with an internal electron donor such as phthalate, diether, or succinate based on a carrier such as dialkoxy magnesium or magnesium chloride (MgCl ₂ ). Can be.

It is preferable to use a co-catalyst and an external electron donor. As the cocatalyst, an alkyl aluminum compound can be used. Examples of the alkyl aluminum compound include, but are not limited to, triethyl aluminum, diethylchloro aluminum, tributyl aluminum, trisisobutyl aluminum, trioctyl aluminum, and the like.

As an external electron donor, an organic silane compound is preferable. Examples of the organosilane compound include diphenyldimethoxysilane, phenyltrimethoxysilane, phenylethyldimethoxysilane, phenylmethyldimethoxysilane, methoxytrimethylsilane, isobutyltrimethoxysilane, diisobutyldimethoxysilane, di Isopropyldimethoxysilane, di-t-butyldimethoxysilane, dicyclopentyldimethoxysilane, cyclohexylmethyldimethoxysilane, dicyclohexyldimethoxysilane, and the like, but are not limited thereto.

The polypropylene resin composition according to an embodiment of the present invention may further include conventional additives within the scope of the present invention. For example, the polypropylene resin composition may include one or more additives selected from the group consisting of antioxidants, slip agents, anti-blocking agents, processing lubricants, reinforcing materials, fillers, weathering stabilizers, antistatic agents, nucleating agents, flame retardants, pigments and dyes. It may include, but is not limited to these.

Preferably, the polypropylene resin composition according to an embodiment of the present invention may further include an antioxidant. For example, the antioxidant may be at least one selected from the group consisting of a phenolic antioxidant, a phosphite-based antioxidant, a thiothiopropionate antioxidant, and combinations thereof. Specifically, tetrakis (methylene (3,5-di-t-butyl-4-hydroxy) hydrosilylnate), 1,3,5-trimethyl-tris (3,5-di-t-butyl-4- Hydroxy benzene) and tris (2,4-di-t-butylphenyl) phosphite, but may be one or more selected from the group consisting of, but is not limited to.

At this time, the antioxidant may be added in an amount of 0.05 to 0.2 parts by weight, preferably 0.05 to 0.1 parts by weight based on 100 parts by weight of the polypropylene resin composition. When the content of the antioxidant is less than 0.05 parts by weight, it is difficult to secure the antioxidant effect of the polypropylene resin composition, and when the content of the antioxidant exceeds 0.2 parts by weight, the antioxidant may be eluted or the economics of the product may deteriorate. not.

Preferably, the polypropylene resin composition according to an embodiment of the present invention may further include a slip agent. For example, the slip agent may be an amide-based slip agent, but is not limited thereto.

At this time, the slip agent may be added in an amount of 0.05 to 0.5 parts by weight, preferably 0.05 to 0.3 parts by weight based on 100 parts by weight of the polypropylene resin composition. If the content of the slip agent is less than 0.05 parts by weight, the processability of the resin composition may be lowered or the film produced may not have sufficient slip properties. When the content of the slip agent exceeds 0.5 parts by weight, the slip agent may be eluted or the economics of the product may be deteriorated, which is not preferable.

Preferably, the polypropylene resin composition according to an embodiment of the present invention may further include an antiblocking agent. For example, the anti-blocking agent may be porous silica or zeolite, but is not limited thereto.

At this time, the blocking inhibitor may be added in an amount of 0.05 to 0.5 parts by weight, preferably 0.05 to 0.3 parts by weight based on 100 parts by weight of the polypropylene resin composition. When the content of the antiblocking agent is less than 0.05 parts by weight, it is difficult to prevent the film from being adhered to each other, and when the content of the antiblocking agent exceeds 0.5 parts by weight, haze of the produced film may not be good.

The method of manufacturing the heat-shrinkable polypropylene film according to another embodiment of the present invention is not particularly limited, and methods known in the art to which the present invention pertains may be used. For example, the heat-shrinkable polypropylene film may be prepared by processing the polypropylene resin composition according to an embodiment of the present invention by a conventional method such as a double bubble film process, extrusion molding, and casting molding. . Of these, the double bubble film process is most preferred.

The heat-shrinkable blown polypropylene film according to an embodiment of the present invention has a shrinkage of 50 to 70%, and preferably a shrinkage of 52 to 65%.

In addition, the heat-shrinkable blown polypropylene film according to an embodiment of the present invention has a haze of 2.0% or less, and preferably has a haze of 0.5 to 1.5%.

The blown polypropylene film according to an embodiment of the present invention is not only excellent in shrinkage and haze, but also has good heat adhesion and opening property, and is suitable for use as a film for heat shrinking.

Example

Hereinafter, the present invention will be described in more detail through examples and comparative examples. However, the following examples are only for illustrating the present invention, and the scope of the present invention is not limited to them.

After supporting titanium chloride (TiCl ₄ ) on a magnesium chloride (MgCl ₂ ) carrier, dicyclopentyl dimethoxysilane as an external electron donor and triethyl aluminum as a cocatalyst for activation of the catalyst were added to obtain a Ziegler-Natta catalyst. . A ternary copolymer of ethylene / propylene / 1-butene was prepared by injecting ethylene, propylene and 1-butene in the presence of the above Ziegler-Natta catalyst in three bulk polymerization tanks arranged in series in the Hypole manufacturing process.

The properties of the resulting ternary copolymer were measured by the following method, and the results are shown in Table 1 below.

(1) Melt Index

It was measured at a temperature of 230 ° C. with a load of 2.16 kg according to the method of ASTM D 1238.

(2) Solvent extract (xylene soluble) content

Each resin was dissolved in xylene at a concentration of 1% by weight at 135 ° C for 1 hour, and after 2 hours at room temperature, the extracted weight was measured, and this was expressed as a percentage of the total weight of the resin.

(3) Melting temperature (Tm)

Using TA Instrument Q2000 differential scanning calorimetry (DSC), samples are kept at 200 ° C for 10 minutes to remove the thermal history, then cooled from 200 ° C to 30 ° C at 10 ° C per minute and crystallized for the same heat history. After having it, the temperature was maintained at 30 ° C. for 10 minutes, and the temperature was increased by 10 ° C. per minute to obtain a melting temperature (Tm) from the peak temperature.

unit Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Melt Index g / 10 minutes 5.2 5.3 5.1 5.3 5.4 5.2 5.1 Tm ℃ 135 130 124 139 138 116 114 Ethylene weight% 2.2 2.9 4.1 1.1 2.2 6.1 4.2 1-butene weight% 4.1 5.1 5.2 5.1 2.1 5.1 8.8 Solvent extract weight% 6.2 12 16 4.5 3.8 > 20 > 20

Irganox 1010 and IRGAFOS 168 are 0.1 parts by weight, and 0.5 parts by weight of amide-based slip agent (Erucamide; Sigma-Aldrich), and porous silica blocking agent as 0.2 parts by weight of antioxidant per 100 parts by weight of each ternary copolymer resin shown in Table 1 above. 0.5 parts by weight were mixed and the resin composition was pelletized in an extruder at 200 ° C.

The pellets of the obtained resin composition were film-molded and cooled using an extruder and a circular die at 200 ° C., and then stretched at 120 ° C. (3 and 8 times respectively for MD and TD stretching ratios) in a double bubble manner, 20 μm. A final film of thickness was obtained.

The properties of each film were measured in the following manner, and the results are shown in Table 2.

(1) Shrinkage

The stretched film was cut to a size of 10 cm × 10 cm, soaked in oil at 120 ° C. for 10 seconds, and the length was measured to calculate the shrinkage.

(2) haze

The haze of the stretched film was measured according to ASTM D-1003.

(3) Haze change over time

When the stretched film was stored in an oven at 80 ° C. for 1 hour, and when the haze was measured again, it was evaluated as good (○) when the haze was maintained at 5% or less, and bad (X) when it exceeded 5%.

(4) Anti-blocking aperture

As a criterion for determining how easily the film falls when stored in a superimposed state, two films of 2 cm in width are superimposed and 24 hours elapsed in an oven at 40 ° C. while holding an area of 2 cm × 2 cm with a weight of 400 g. Then, the adhesive strength of the pressed portion was measured. When the adhesive strength was 0.2 kgf / cm or less, it evaluated as good (○), and when it was 0.2 kgf / cm or more, it evaluated as bad (X).

(5) Heat adhesion

The heat adhesion temperature (test condition: 2 kgf / 1 second) between the films was measured, and evaluated as good (○) when less than 120 ° C and bad (X) when more than 120 ° C.

unit Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Shrinkage % 52% 57 63 46% 43% 46% 43% Haze % 1.5 0.9 0.8 2.7 2.5 2.7 2.5 Haze changes over time ○ ○ ○ ○ ○ ○ ○ Openness ○ ○ ○ ○ ○ ○ ○ Heat adhesion ○ ○ ○ X X X X

As can be seen from Table 2 above, the films prepared from the polypropylene resin compositions of Examples 1 to 3 belonging to the scope of the present invention have shrinkage, haze (cloudiness), haze change over time, aperture and heat adhesion. All were excellent.

On the other hand, in the polypropylene resin compositions of Comparative Examples 1 and 2, the content of ethylene or 1-butene and the content of the solvent extract are below the standard values, so the melting temperature of the resin is high, so that the film has poor thermal adhesion. In addition, the shrinkage rate of the film is less than the reference value (50%), and the initial haze of the film exceeds 2.0%, resulting in poor transparency.

On the other hand, in comparison, the polypropylene resin compositions of 3 and 4 had a good ethylene or 1-butene content and a solvent extract content exceeding the reference values, so that the shrinkage and haze of the film were good, but the heat shrinkage and change over time of the haze were not good. It is not suitable for use as a film.

Therefore, the film produced through the double bubble film process from the polypropylene resin composition according to the embodiment belonging to the scope of the present invention is excellent in transparency, adhesive properties and shrinkage properties, and is used as a heat-shrinkable film. Is suitable for

Claims (8)

A polypropylene resin composition for a heat-shrinkable blown film comprising a terpolymer of ethylene / propylene / 1-α-olefin, wherein the content of ethylene in the terpolymer is more than 1.5% by weight and less than 5.0% by weight, and 1-α -The content of the olefin exceeds 3.5 wt%, but the content of ethylene (A wt%) and the content of 1-α-olefin (B wt%) satisfy Equation 1 below:
[Equation 1]
8.0 <2 * A + B <15.0
The content of the solvent extract in this ternary copolymer is 5.0 to 20.0 wt%, the melt index is 3.0 to 6.5 g / 10 min when measured at 230 ° C under a load of 2.16 kg, the melting temperature (Tm) is 135 ° C or less, and heat shrinkage St. blown film is produced through a double bubble film process (double bubble film process), has a shrinkage rate of 50 to 70% and a haze of 2.0% or less, and a heat shrinkable blown film having a width of 2 cm. A heat-shrinkable blown film characterized by having an adhesive strength of 0.2 kgf / cm or less after 24 hours elapse in an oven at 40 ° C. while holding an area of 2 cm × 2 cm with a weight of 400 g overlaid with a sheet of weight. Polypropylene resin composition. The heat-shrinkable blown film according to claim 1, wherein the 1-α-olefin is at least one member selected from the group consisting of 1-butene, 1-pentene, 1-hexene, 1-heptene and 1-octene. Polypropylene resin composition. The method of claim 1, further comprising at least one additive selected from the group consisting of antioxidants, slip agents, anti-blocking agents, processing lubricants, reinforcing materials, fillers, weathering stabilizers, antistatic agents, nucleating agents, flame retardants, pigments and dyes Polypropylene resin composition for a heat-shrinkable blown film, characterized in that. The tetrakis (methylene (3,5-di-t-butyl-4-hydroxy) hydrosilylnate), 1,3,5-trimethyl-tris according to claim 3, based on 100 parts by weight of the polypropylene resin composition. 0.05 to 0.2 parts by weight of at least one antioxidant selected from the group consisting of (3,5-di-t-butyl-4-hydroxy benzene) and tris (2,4-di-t-butylphenyl) phosphite. Polypropylene resin composition for a heat-shrinkable blown film further comprising. The polypropylene resin composition for a heat-shrinkable blown film according to claim 3, further comprising 0.05 to 0.5 parts by weight of an amide-based slip agent relative to 100 parts by weight of the polypropylene resin composition. The heat-shrinkable property of claim 3, further comprising 0.05 to 0.5 parts by weight of at least one anti-blocking agent selected from the group consisting of porous silica, zeolite, and combinations thereof, with respect to 100 parts by weight of the polypropylene resin composition. Polypropylene resin composition for blown film. A heat-shrinkable blown polypropylene film prepared from a polypropylene resin composition according to any one of claims 1 to 6 through a double bubble film process. The heat shrinkable blown film having a shrinkage rate of 50 to 70% and a haze of 2.0% or less, and having a width of 2 cm, is superimposed on two sheets, and an area of 2 cm × 2 cm is obtained with a weight of 400 g. Heat-shrinkable blown polypropylene film, wherein after 24 hours in an oven at 40 ° C. while pressing, the adhesive strength of the pressed portion is 0.2 kgf / cm or less.