KR102067308B1 - Polypropylene film for in-mold labels - Google Patents

Abstract

Provided are polypropylene films suitable for in mold label applications. A film composed mainly of polypropylene resin, wherein the thermal shrinkage in the MD direction and the TD direction at 150 ° C. is both 9% or less, the Young's modulus in the MD direction is 2 GPa or more, the Young's modulus in the TD direction is 4 GPa or more, and the haze It is 6% or less, The polypropylene film for in-mold labels.

Description

Polypropylene film for in mold label {POLYPROPYLENE FILM FOR IN-MOLD LABELS}

The present invention relates to a polypropylene film for in-mold label having excellent heat resistance and mechanical properties.

The conventional polypropylene film has a shrinkage ratio at 150 ° C. of several tens percent, and is low in heat resistance and low in stiffness as compared with PET. Thus, curling due to shrinkage is liable to occur during the lamination processing, which causes a defect.

In order to solve these problems, the technique which is made into the film which has high solidity regularity and has a high temperature rigidity and heat resistance by making it a stretched film using polypropylene with a narrow molecular weight distribution was known (for example, refer patent document 1 etc.). .

Moreover, the technique which can use suitably as a capacitor film which has high stereoregularity and is excellent in electrical insulation, a mechanical characteristic, etc. by using polypropylene which has a wide molecular weight distribution and is excellent is known (for example, patent document 2 etc.). Reference).

Moreover, the technique which makes a separator film using the polypropylene which is low molecular weight and the soluble content of 0 degreeC by a temperature rising fractionation method in a specific range is known, and this film is considered to be excellent also in the dimensional stability in a drying process and a printing process. (For example, refer patent document 3).

However, the films described in Patent Literatures 1 to 3 had difficulty in stretchability and were inferior in mechanical properties.

By adding a small amount of long-chain branched or crosslinked polypropylene to the medium molecular weight component, it promotes the formation of porcelain lamellae to improve the elongation, and is excellent in mechanical properties, heat resistance and voltage resistance characteristics, and excellent uniformity of product properties. The technique which makes a film was known (for example, refer patent document 4).

Moreover, the technique which balances rigidity and workability is known by making into a film using polypropylene which contains almost the same amount of high molecular weight components and a medium molecular weight component (there are few low molecular weight components), and has a wide molecular weight distribution and little decalin soluble content. (For example, refer patent document 5 etc.).

The films described in these patent documents 4 to 5 cannot be said to have sufficient heat resistance at high temperatures, and have no high heat resistance, and no polypropylene film having excellent impact resistance and transparency is known. That is, these are not exceeding the area | region of the conventional polypropylene film, The use is limited and, for example, it has not paid attention to the heat resistance in high temperature exceeding 150 degreeC.

When the label is applied to the outer surface of a resin container having a polypropylene or polyethylene container as a representative example, the in-mold labeling method that adheres to the outer surface of the container simultaneously with molding of the container is capable of full surface adhesion and is difficult to peel off. In terms of designability, such as point and large-area label display, and many other advantages, such as having a label, the container itself can be made thinner by increasing the rigidity of the container itself.

Conventionally, paper, synthetic paper, a plastic film, etc. are used as an in-mold label base material (for example, refer patent document 6, patent document 7, patent document 8, etc.).

In the case of a plastic film, in order to perform printing, lamination processing, adhesive processing, etc., bonding of the same plastic film or joining the plastic film of the various material which conforms to a label specification is comprised widely in order to comprise an in-mold label. As this plastic film, many polypropylene films are used from an adhesive viewpoint with a container.

However, in the conventional polypropylene film for in-mold labels, since the film is stretched or shrunk due to their processing, specifically, the tension under heating applied to the film during printing or lamination, the label of the label after completion as a label It is also known that curling often becomes a problem (see Patent Document 9, for example).

In order to suppress curling, in printing and laminating processing, the processing conditions may be adjusted to a high frequency, the thickness of the polypropylene film may be thickened, or the widthwise center portion of the polypropylene film may be selected and used as an in-mold label substrate. Labels have been forced to costly construction.

Japanese Patent Publication No. 8-325327 Japanese Patent Laid-Open No. 2004-175932 Japanese Patent Laid-Open No. 2001-146536 Japanese Patent Laid-Open No. 2007-84813 Japanese Patent Publication No. 2008-540815 Japanese Patent Laid-Open No. 58-69015 Japanese Patent Publication No. 02-7814 Japanese Patent Publication No. 02-84319 Japanese Patent Laid-Open No. 2005-208355

The present invention has been made in the background of these prior art problems. That is, an object of the present invention is to provide a polypropylene film suitable for in-mold label use.

MEANS TO SOLVE THE PROBLEM As a result of earnestly examining in order to achieve this objective, the present inventors completed the present invention. That is, the present invention is a film mainly composed of a polypropylene resin, the heat shrinkage in both the MD direction and the TD direction at 150 ° C is 9% or less, the Young's modulus in the MD direction is 2 GPa or more, and the TD direction The Young's modulus is 4 GPa or more, and haze is 6% or less, It is a polypropylene film for in-mold labels.

In this case, it is suitable that the minimum of the isotactic meso pentad fraction of the polypropylene resin which comprises the said film is 96%, and the minimum of the plane orientation coefficient of a film is 0.0125.

Moreover, in this case, it is suitable that the upper limit of the amount of copolymerization monomers of the polypropylene resin which comprises the said film is 0.1 mol%.

Moreover, in this case, it is suitable that the normal temperature xylene soluble content of the polypropylene resin which comprises the said film is 7 mass% or less.

Even when a plastic film of various materials is bonded to the polypropylene film of the present invention to form an in-mold label, the polypropylene film of the present invention is less likely to be stretched due to the tension at the time of printing or laminating processing, and the label after bonding is curled. Can be prevented.

1 is a DSC chart of a polypropylene film of Example 1 and Comparative Example 1. FIG.

The present invention relates to a polypropylene film for in-mold label. The polypropylene film for in-mold labels of the present invention is a film mainly composed of polypropylene resin, and the heat shrinkage in the MD direction and the TD direction at 150 ° C is both 9% or less, and the Young's modulus in the MD direction is 2 GPa or more, The Young's modulus in the TD direction is 4 GPa or more, and the haze is 6% or less.

(Film characteristics)

The lower limit of the heat shrinkage at 150 ° C. in the MD and TD directions of the polypropylene film of the present invention is preferably 0.5%, more preferably 1%, still more preferably 1.5%, particularly preferably 2 %, Most preferably 2.5%. When the thermal contraction rate is 0.5% or more, realistic manufacture may be easy or thickness nonuniformity may become small in terms of cost. In addition, MD direction is a flow direction of a film, and TD direction is a direction perpendicular | vertical to the flow direction of a film.

The upper limit of the thermal contraction rate in 150 degreeC of MD direction and TD direction is 9%, Preferably it is 8%, More preferably, it is 7%, More preferably, it is 6%, Most preferably, it is 5%. When the said heat shrinkage rate is 9% or less, the film excellent in heat resistance can be obtained and it becomes easier to use in the use which may be exposed to high temperature about 150 degreeC. In the case where the thermal contraction rate at 150 ° C. is about 2.5% or more, for example, it is possible to adjust the stretching conditions and heat fixing conditions to increase the molecular weight of about 100,000 low molecular weight polypropylene (hereinafter referred to as low molecular weight component). If lower than about 2.5%, annealing offline is preferable. Moreover, in the conventional polypropylene film, the thermal contraction rate in 150 degreeC of MD direction and TD direction exceeds 15%, and the thermal contraction rate in 120 degreeC is about 3%.

When the polypropylene film is a biaxially oriented film, the lower limit of the Young's modulus (23 ° C.) in the MD direction is 2 GPa, preferably 2.1 GPa, more preferably 2.2 GPa, still more preferably 2.3 GPa, most preferably For example, 2.4 GPa. The upper limit of the Young's modulus in the MD direction is preferably 4 GPa, more preferably 3.7 GPa, still more preferably 3.5 GPa, particularly preferably 3.4 GPa, most preferably 3.3 GPa. When the Young's modulus of MD direction is 2 GPa or more and 4 GPa or less, manufacture may be easy or MD-TD balance may become favorable realistically.

When a polypropylene film is a biaxially stretched film, the minimum of Young's modulus (23 degreeC) of a TD direction is 4 GPa, More preferably, it is 4.2 GPa, More preferably, it is 4.3 GPa. The upper limit of the Young's modulus in the TD direction is preferably 8 GPa, more preferably 7.5 GPa, still more preferably 7 GPa, and particularly preferably 6.5 GPa. When the Young's modulus in the TD direction is 3.8 GPa or more and 8 GPa or less, manufacturing may be easy or the MD-TD balance may be improved in reality.

Moreover, a Young's modulus can be enlarged by making a draw ratio high, In the case of MD-TD extending | stretching, the Young's modulus of a TD direction can be enlarged by setting a draw ratio a little low in MD direction, and increasing a draw ratio of a TD direction.

The lower limit as a realistic value of the haze of the polypropylene film of the present invention is preferably 0.1%, more preferably 0.2%, still more preferably 0.3%, particularly preferably 0.4%, most preferably 0.5 %to be. The upper limit of the haze of a film is 6%, Preferably it is 5%, More preferably, it is 4.5%, More preferably, it is 4%, Most preferably, it is 3.5%. When haze is 6% or less, it may become easy to use for the use which transparency is calculated | required. The haze tends to be large when the stretching temperature or the heat setting temperature is too high, when the cooling roll temperature is high and the cooling rate is slow, when there are too many low molecular weight components, and it can be brought into the above range by adjusting these.

Preferably the upper limit of the curl amount of the polypropylene film of this invention is 15 mm, More preferably, it is 14 mm, More preferably, it is 13 mm, Most preferably, it is 12 mm. If the amount of curl is 15 mm or less, the defective generation of the film caused by curl can be suppressed. In addition, the measuring method of a curl amount is mentioned later.

(Polypropylene resin)

The polypropylene resin constituting the film of the present invention has a characteristic wide molecular weight distribution. The polypropylene resin used in the present invention is mainly a low molecular weight polypropylene (low molecular weight component) having a mass mean molecular weight (M _w ) of about 100,000, for example, and a very high molecular weight of M _w of about 1.5 million, for example. It is preferable that this high molecular weight polypropylene (henceforth a high molecular weight component) is contained. It is thought that the crystallinity can be largely improved by mainly using the low molecular weight component, and the high stiffness and high heat resistance polypropylene film which is not conventionally obtained is obtained. On the other hand, the low molecular weight polypropylene resin has a low melt tension at the time of heat softening, and generally it is difficult to obtain a stretched film. The polypropylene film of the present invention can be easily formed because the high molecular weight component can be stretched by the presence of a high molecular weight component therein, and the high molecular weight component can act as a crystal nucleus and can increase the crystallinity of the film. I think it can be obtained.

Number as the parameter indicative of the polymeric molecular weight-average molecular weight (M _n), weight average molecular weight (M _w), Z-average molecular weight (M _{z), Z} + 1-average molecular weight (M _{z + 1),} peak molecular weight (M _p), etc. a can be mentioned, which are defined as follows by the number of molecules (N _i) having a molecular weight (M _i).

The number-average molecular _{weight: M n = Σ (N i} · M i) / ΣN i

Mass average molecular weight: M _w = Σ (N _i M _i ² ) / Σ (N _i M _i )

Z-average molecular _{weight: M z = Σ (N i} · M i 3) / Σ (N i · M i 2)

Z + 1-average molecular _{weight: M z + 1 = Σ (} N i · M i 4) / Σ (N i · M i 3)

Peak molecular weight: M _p (molecular weight of peak position of gel permeation chromatography (GPC) curve)

And, as the parameter indicative of the molecular weight distribution is the ratio commonly used in these average molecular weight of, for example, may include a M _w / M _n, M _{z + 1} / M _n, etc., the characteristics of the polypropylene resin used in the present invention M _{z + 1} / M _n is suitable for showing a typical molecular weight distribution. As a measuring method of such molecular weight and molecular weight distribution, GPC is generally used.

The lower limit of M _{z + 1} / M _n is preferably 50, more preferably 60, still more preferably 70, particularly preferably 80, and most preferably 90. If the M _{z + 1} / M _n is less than 50 in some cases the effects of the present invention, such as low thermal shrinkage at high temperature to be difficult be obtained. The upper limit of M _{z + 1} / M _n is preferably 300, and more preferably 200. Exceeds M _{z + 1} / M _n of 300 there is a case where in reality the difficult manufacture of the resin.

Preferably the minimum of M _{z + 1} of the whole polypropylene resin which comprises a film is 2500000, More preferably, it is 3000000, More preferably, it is 3300000, Especially preferably, it is 3500000, Most preferably, it is 3700000. If Mz _{+ 1} is 2500000 or more, a high molecular weight component is enough and the effect of this invention is easy to be acquired. Preferably the upper limit of M _{z + 1} of the whole polypropylene resin which comprises a film is 40000000, More preferably, it is 35000000, More preferably, it is 30000000. When Mz _{+ 1} is 4000000 or less, manufacture of resin may become easy, extending | stretching may become easy, or there may be less fish eye in a film.

The lower limit of the total of the polypropylene resin constituting the film is preferably a M _n of 20,000, and more preferably 22,000, and more preferably 24000, and particularly preferably from 26,000 and most preferably 27,000. If _n is more than 20000 M becomes stretching is easy, there is a case where the advantage of being small in thickness irregularity, the temperature and the heat setting temperature becomes higher the lower the heat shrinkage ratio in the stretching occurs easily. The upper limit of the total of the polypropylene resin constituting the film M _n is preferably from 65000, and is more preferably 60,000, and more preferably 55000, and particularly preferably from 53000, most preferably 52000. M _n is less than 65,000 it may become easy to the effect of the low molecular weight component expression, such as low thermal shrinkage at high temperatures or stretch easily be obtained is easy.

The lower limit of the total of the polypropylene resin constituting the film is preferably a M _w 250,000, and more preferably 260000, and more preferably 270000, and especially preferably 280,000, and most preferably 290000. When the M _w is more than 250,000 become stretching is easy, there is a case that the thickness non-uniformity is small and the temperature or the heat setting temperature becomes high, this will lower the advantage heat shrinkage occurs easily stretched. The upper limit of the total of the polypropylene resin constituting the film is preferably a M _w 500,000, and more preferably 450,000, and more preferably 400000, more preferably 380000, most preferably 370 000. Is less than the M _w 500000 there are cases in which the mechanical load is smaller elongation easily.

The lower limit of M _w / M _n is preferably 5.5, more preferably 6, still more preferably 6.5, particularly preferably 7 and most preferably 7.2.

The upper limit of M _w / M _n is preferably 30, more preferably 25, still more preferably 20, particularly preferably 15, and most preferably 13.

The minimum of melt flow rate (MFR) (230 degreeC, 2.16 kgf) of the whole polypropylene resin which comprises a film becomes like this. Preferably it is 1 g / 10min, More preferably, it is 1.2g / 10min, More preferably, it is 1.4g / 10 Minutes, particularly preferably 1.5 g / 10 minutes, most preferably 1.6 g / 10 minutes. When MFR is 1 g / 10 minutes or more, mechanical load may be small and extending | stretching may become easy. The upper limit of the MFR of the entire polypropylene resin constituting the film is preferably 11 g / 10 minutes, more preferably 10 g / 10 minutes, still more preferably 9 g / 10 minutes, and most preferably 8.5 g / 10 minutes. When MFR is 11 g / 10min or less, extending | stretching becomes easy, thickness nonuniformity becomes small, extending | stretching temperature or heat setting temperature becomes high easily, and a thermal contraction rate may become lower.

When the gel permeation chromatography (GPC) integration curve of the whole polypropylene resin which comprises a film is measured, the minimum of the ratio of the component of molecular weight 10,000 or less in the whole polypropylene resin becomes like this. Preferably it is 2 mass%, and more Preferably it is 2.5 mass%, More preferably, it is 3 mass%, Especially preferably, it is 3.3 mass%, Most preferably, it is 3.5 mass%. When the proportion of the component having a molecular weight of 10,000 or less is 2% by mass or more, the effects of the present application, such as a low heat shrinkage ratio at a high temperature that is an effect of a low molecular weight product, may be more easily obtained, or stretching may be easier.

Preferably the upper limit of the ratio of the component of molecular weight 10,000 or less in the whole polypropylene resin in a GPC integration curve is 20 mass%, More preferably, it is 17 mass%, More preferably, it is 15 mass%, Especially Preferably it is 14 mass%, Most preferably, it is 13 mass%. When the proportion of the component having a molecular weight of 10,000 or less is 20% by mass or less, the stretching may be easy, the thickness nonuniformity may be small, the stretching temperature or the heat setting temperature may be high, and the heat shrinkage rate may be lowered.

A molecule having a molecular weight of 10,000 or less does not contribute to the entanglement between molecular chains, and has an effect of plasticizing the entanglement between molecules. By including a specific amount of the component having a molecular weight of 10,000 or less, the entanglement of molecules at the time of stretching is easy to be released, and the stretching at low stretching stress is possible, and as a result, the residual stress is low and the shrinkage rate at high temperature can be lowered. I think.

Preferably the minimum of the ratio of the component of the molecular weight 100,000 or less in the whole polypropylene resin in a GPC integration curve is 35 mass%, More preferably, it is 38 mass%, More preferably, it is 40 mass%, Especially Preferably it is 41 mass%, Most preferably, it is 42 mass%. When the proportion of the component having a molecular weight of 100,000 or less is 35% by mass or more, the effect of the low molecular weight substance is likely to be expressed, and a low heat shrinkage ratio at a high temperature may be easily obtained or the stretching may be easy.

Preferably the upper limit of the ratio of the component of molecular weight 100,000 or less in the whole polypropylene resin in a GPC integration curve is 65 mass%, More preferably, it is 60 mass%, More preferably, it is 58 mass%, Especially Preferably it is 56 mass%, Most preferably, it is 55 mass%. When the proportion of the component having a molecular weight of 100,000 or less is 65% by mass or less, the stretching may be easy, the thickness nonuniformity may be small, the stretching temperature or the heat setting temperature may be high, and the thermal shrinkage may be easily lowered.

In the past, sufficient stretching was not possible with polypropylene mainly composed of low molecular weight components, but by using polypropylene resin having such a characteristic molecular weight distribution, it is possible to stretch even polypropylene mainly composed of low molecular weight components, and high heat. It is considered that a fixed temperature can be adopted, and the heat shrinkage ratio at high temperature can be lowered due to the synergistic effect of high crystallinity and strong thermal fixation.

The high molecular weight component and the low molecular weight component which are preferably used to obtain a polypropylene resin having such molecular weight distribution characteristics will be described below.

(High molecular weight component)

The lower limit of the MFR (230 DEG C, 2.16 kgf) of the high molecular weight component is preferably 0.0001 g / 10 minutes, more preferably 0.0005 g / 10 minutes, still more preferably 0.001 g / 10 minutes, particularly preferably 0.005 g. / 10 minutes. When MFR of a high molecular weight component is 0.0001g / 10min or more, manufacture of resin may be easy or the fisheye of a film may be reduced realistically.

In addition, the MFR of the high molecular weight component at 230 ° C. and 2.16 kgf may be too small, making it difficult to measure in reality. In terms of MFR at 10 times the load (21.6 kgf) of 2.16 kgf, the lower limit is preferably 0.1 g / 10 minutes, more preferably 0.5 g / 10 minutes, still more preferably 1 g / 10 minutes, and particularly preferably 5 g. / 10 minutes.

The upper limit of the MFR (230 DEG C, 2.16 kgf) of the high molecular weight component is preferably 0.5 g / 10 minutes, more preferably 0.35 g / 10 minutes, still more preferably 0.3 g / 10 minutes, particularly preferably 0.2 g. / 10 minutes, most preferably 0.1 g / 10 minutes. When the MFR of the high molecular weight component is 0.5g / 10min or less, many high molecular weight components are not necessary to maintain the MFR of the entire polypropylene resin, and the effect of the low molecular weight component is easily expressed, and the low heat shrinkage at high temperature It may become easier to obtain it.

The lower limit of the M _w of the high molecular weight component is preferably 500000, more preferably 600000, still more preferably 700000, particularly preferably 800000, most preferably 1000000. And if the molecular weight of component M _w is more than 500 000 in order to maintain MFR of the whole polypropylene resin, without the need for a positive number of polymer components, tends to be the effect of the low molecular weight component expression, it is obtained than is such low thermal shrinkage at high temperature It may become easy to be caught.

The upper limit of M _w of the high molecular weight component is preferably 10000000, more preferably 8000000, still more preferably 6000000, particularly preferably 5000000. When the M _w of the high molecular weight component 10 million or less, there is a case that the production of the resin in reality can be easily reduced or fish eyes of the film.

Preferably the minimum of the quantity of a high molecular weight component is 2 mass%, More preferably, it is 3 mass%, More preferably, it is 4 mass%, Especially preferably, it is 5 mass%. When the amount of the high molecular weight component is 2% by mass or more, it is not necessary to raise the molecular weight of the low molecular weight component in order to maintain the MFR of the entire polypropylene resin, and the effect of the present invention such as low heat shrinkage at high temperature is more easily obtained. There is.

Preferably the upper limit of the quantity of a high molecular weight component is 30 mass%, More preferably, it is 25 mass%, More preferably, it is 22 mass%, Especially preferably, it is 20 mass%. When the amount of the high molecular weight component is 30% by mass or less, the effect of the low molecular weight component is likely to be expressed, and low heat shrinkage at high temperature may be more easily obtained. In addition, the ratio of the high molecular weight component with respect to the whole polypropylene resin which comprises a film shall be calculated | required by performing peak separation from the molecular weight distribution curve measured using GPC, and the same also applies to other components, such as a low molecular weight component mentioned later.

Here, as the high molecular weight component, a polypropylene resin having a long chain branch or a crosslinked structure may be used instead of the linear polypropylene resin, which is known as a high melt tension polypropylene, and is manufactured by Borealis Daploy) "WB130HMS", "WB135HMS", and the like.

(Low molecular weight component)

The lower limit of the MFR (230 ° C., 2.16 kgf) of the low molecular weight component is preferably 70 g / 10 minutes, more preferably 80 g / 10 minutes, still more preferably 100 g / 10 minutes, particularly preferably 150 g / 10 minutes, Most preferably 200 g / 10 min. If the MFR of the low molecular weight component is 70 g / 10 min or more, crystallinity may be improved, and a low heat shrinkage ratio at high temperature may be more easily obtained.

The upper limit of the MFR of the low molecular weight component is preferably 2000 g / 10 minutes, more preferably 1800 g / 10 minutes, still more preferably 1600 g / 10 minutes, and most preferably 1500 g / 10 minutes. When MFR of a low molecular weight component is 2000g / 10min or less, it may become easy to maintain MFR in the whole polypropylene resin, and may be excellent in film forming property.

The lower limit of M _w of the low molecular weight component is preferably 50000, more preferably 53000, still more preferably 55000, particularly preferably 60000, most preferably 70000. When the M _w of 50,000 or more low molecular weight components make it easier to maintain MFR of the whole polypropylene resin, there is a case is excellent in film-forming property.

The upper limit of M _w of the low molecular weight component is preferably 170000, more preferably 165000, still more preferably 160000, particularly preferably 155000, and most preferably 150000. Is a M _w of low molecular weight components like the crystallinity is less than 170000, there is a case where the low thermal shrinkage at high temperature than that easily be obtained.

Preferably the minimum of the quantity of a low molecular weight component is 40 mass%, More preferably, it is 50 mass%, More preferably, it is 55 mass%, Especially preferably, it is 60 mass%. When the amount of the low molecular weight component is 40% by mass or more, a low heat shrinkage ratio at high temperature, which is an effect of the low molecular weight component, may be more easily obtained.

Preferably the upper limit of the quantity of a low molecular weight component is 98 mass%, More preferably, it is 97 mass%, More preferably, it is 96 mass%, Especially preferably, it is 95 mass%. When the amount of the low molecular weight component is 98% by mass or less, it is not necessary to increase the molecular weight of the low molecular weight component in order to maintain the MFR in the entire polypropylene resin, and low heat shrinkage at high temperature may be more easily obtained.

The lower limit of the MFR ratio of the MFR / high molecular weight component of the low molecular weight component is preferably 500, more preferably 1000, still more preferably 2000, and particularly preferably 4000. When the MFR ratio of the low molecular weight component / MFR of the high molecular weight component is 500 or more, the effects of the present invention, such as low heat shrinkage at high temperature, may be more easily obtained. The upper limit of the MFR ratio of the low molecular weight component / MFR of the high molecular weight component is preferably 1000000.

The high molecular weight component and the low molecular weight component may be a mixture of two or more resins corresponding to the respective components, and the compounding amount in this case is a total amount.

Moreover, in order to adjust MFR in the whole polypropylene resin other than the said high molecular weight component and the low molecular weight component, you may add the component which has molecular weights other than the low molecular weight component and high molecular weight component of this invention. For example, a polypropylene (hereinafter referred to as a medium molecular weight component) that is M _w that is larger than the low molecular weight component and smaller than the high molecular weight component may be included. In addition, in order to ease the entanglement of the molecular chain to control elongation and the like, preferably a polypropylene resin of less than M _w 50,000, more preferably a polypropylene resin of M _w 30,000 or less, particularly preferably M _w You may add 10,000 or less polypropylene resin.

And the lower limit of the ratio of the molecular weight components of the entire polypropylene constituting the film may vary depending on the M _w of the molecular components of use, preferably 5% by mass, more preferably 10% by mass, and more preferably 13 mass%, Especially preferably, it is 15 mass%, Most preferably, it is 16 mass%. When the proportion of the medium molecular weight component is 5% by mass or more, the fish eye can be reduced or the stretching may be easy.

Preferably the upper limit of the ratio of the medium molecular weight component with respect to the whole polypropylene resin which comprises a film is 58 mass%, More preferably, it is 56 mass%, More preferably, it is 54 mass%, Especially preferably, it is 52 mass %, And most preferably 50 mass%. When the ratio of the medium molecular weight component is 58% by mass or less, the stretching may be easy, the thickness nonuniformity may be small, the stretching temperature or the heat setting temperature may be high, and the thermal contraction rate may be lowered.

The ratio of the lower limit of polypropylene of M _w less than 50,000 for the entire polypropylene constituting the film is preferably 0% by mass, more preferably 1% by mass, more preferably 2% by mass, in particular Preferably it is 3 mass%, Most preferably, it is 4 mass%. By the addition of polypropylene with less than 5 _w man M has the effects of the present invention, such as low thermal shrinkage at high temperature to be easily be obtained more.

The upper limit of the ratio of the polypropylene of M _w less than 50,000 for the entire polypropylene constituting the film is preferably 20% by mass, and is more preferably 18% by mass, more preferably 17% by mass, in particular Preferably it is 16 mass%, Most preferably, it is 15 mass%. When the ratio of the polypropylene of less than 50,000 M _w less than or equal to 20% by weight to facilitate stretching or in some cases a non-uniform thickness may be decreased.

Polypropylene molecules of less than M _w 50,000 are less likely to form entanglements between molecular chains, and plasticizers have an effect of loosening entanglements between molecules. By containing a specific amount of the polypropylene component of less than M _w 50,000, the entanglement of molecules is easy to be released at the time of stretching, the stretching at low stretching stress is possible, as a result, the residual stress is also low, resulting in low shrinkage at high temperatures. I think it can be done.

In order to make the molecular weight distribution of a polypropylene resin into a preferable state using a high molecular weight component and a low molecular weight component, when the molecular weight of the low molecular weight component used is low, for example, raise the molecular weight of a high molecular weight component, and increase the quantity of a high molecular weight component It can adjust so that it may become MFR which is easy to manufacture as a stretched film, while adjusting the state of molecular weight distribution.

(Stereoregularity of polypropylene resin)

The lower limit of the isotactic meso pentad fraction (hereinafter sometimes referred to as mmmm), which is an index of stereoregularity of the polypropylene resin constituting the film, is preferably 96%, more preferably 96.5%, and even more preferably It is 97%. When mmmm is 96% or more, crystallinity may improve and the thermal contraction rate in high temperature may become lower.

Preferably the upper limit of mmmm is 99.5%, More preferably, it is 99.3%, More preferably, it is 99%. When mmmm is 99.5% or less, manufacture may become easy practically.

In the polypropylene resin constituting the film, it is preferable that heterogeneous bonds such as head-head bonds of propylene monomers are not recognized. In addition, "a heterogeneous bond is not recognized" means that a peak is not seen by ¹³ C-NMR.

Preferably the minimum of the isotactic meso average chain length (henceforth meso average chain length) of the polypropylene resin which comprises a film is 100, More preferably, it is 120, More preferably, it is 130. If meso average chain length is 100 or more, crystallinity may improve and the thermal contraction rate in high temperature may become small. Preferably the upper limit of the meso average chain length of the polypropylene resin which comprises a film is 5000 from a realistic viewpoint.

The minimum of the normal temperature xylene soluble content of the polypropylene resin which comprises a film becomes like this. Preferably it is 0.1 mass% from a realistic viewpoint. Preferably the upper limit of a xylene soluble content is 7 mass%, More preferably, it is 6 mass%, More preferably, it is 5 mass%. If xylene soluble content of a propylene resin is 7 mass% or less, crystallinity may improve and the thermal contraction rate at high temperature may become small.

It is most preferable that the polypropylene resin which comprises a film is a propylene homopolymer (complete homo polypropylene) obtained only from a propylene monomer, but the copolymer of a trace amount monomer other than a propylene monomer and a propylene monomer may be sufficient. As monomer species (copolymerization monomer species) other than a propylene monomer, ethylene, butene, hexene, octene, etc. are possible.

Preferably the upper limit of the ratio of monomers other than a propylene monomer is 0.1 mol%, More preferably, it is 0.05 mol%, More preferably, it is 0.01 mol%. If the ratio of monomers other than a propylene monomer is 0.1 mol% or less, crystallinity may improve and the thermal contraction rate at high temperature may become small.

In addition, when the propylene homopolymer is used, the conventional polypropylene film is difficult to form industrially since the range of conditions that can be stretched is very narrow, such as a high crystallinity and a rapid decrease in melt tension after melt softening. About 0.5 mol% of copolymerization component (mainly ethylene) was added. However, in the polypropylene resin of the above molecular weight distribution state, even if it contains little or no copolymerization component, the tension | strength fall after melt softening is gentle, and industrial stretching is possible.

(Method for producing polypropylene resin)

Polypropylene resin is obtained by superposing | polymerizing the propylene used as a raw material using well-known catalysts, such as a Ziegler-Natta catalyst and a metallocene catalyst. Especially, it is preferable to use the catalyst which is hard to contain a heterogeneous bond like a Ziegler-Natta catalyst and can superpose | polymerize with high stereoregularity.

As a polymerization method of propylene, a known polymerization method can be used, a method of polymerization in an inert solvent such as hexane, heptane, toluene, xylene, a polymerization in liquid propylene or ethylene, a catalyst is added to propylene or ethylene which is a gas. And a method of polymerization in a gaseous state, or a combination of these and the like.

The method for realizing the polypropylene having the molecular weight distribution of the present invention is not particularly limited, but it is necessary to substantially include a high molecular weight component and a low molecular weight component. For example, the high molecular weight component and the low molecular weight component may be separately polymerized and then mixed, or may be produced in a series of plants in a multistage reactor. In particular, a method using a plant having a multistage reactor and polymerizing the high molecular weight component for the first time and then polymerizing the low molecular weight component in the presence thereof is preferred.

Although the additive and other resin may be added to the resin composition for polypropylene film molding of this invention other than polypropylene resin etc. as needed, It is preferable that these mass is 30 mass% or less. As an additive, antioxidant, a ultraviolet absorber, an antistatic agent, a lubricating agent, a nucleating agent, an adhesive, an antifogging agent, a flame retardant, an anti blocking agent, an inorganic or organic filler, etc. are mentioned, for example. As other resin, the polypropylene resin other than the polypropylene resin used by this invention, the random copolymer which is a copolymer of propylene and ethylene, and / or a C4 or more alpha-olefin, various elastomers, etc. are mentioned. Butene, hexene, octene etc. are mentioned as a C4 or more alpha olefin. These may be blended with a polypropylene resin and a Henschel mixer, or may be diluted with polypropylene so that the master pellet previously produced using the melt kneading machine may become predetermined concentration, or it may melt-knead whole quantity beforehand and use it.

(Film properties)

Preferably the minimum of the surface orientation coefficient of the polypropylene film of this invention is 0.0125, More preferably, it is 0.0126, More preferably, it is 0.0127, Especially preferably, it is 0.0128. The upper limit of the plane orientation coefficient of the polypropylene film of the present invention is a realistic value, preferably 0.0155, more preferably 0.0150, still more preferably 0.0148, and particularly preferably 0.0145. The surface orientation coefficient can be adjusted by adjustment of the draw ratio of MD direction and a TD direction. Thickness nonuniformity of a film is also favorable as the surface orientation coefficient of a film is 0.0125 or more and 0.0155 or less.

Preferably the minimum of the refractive index Nx of the polypropylene film of this invention is 1.502, More preferably, it is 1.503, More preferably, it is 1.504. Preferably the upper limit of Nx is 1.520, More preferably, it is 1.517, More preferably, it is 1.515.

Preferably the minimum of the refractive index Ny of the polypropylene film of this invention in the TD direction is 1.523, More preferably, it is 1.525. The upper limit of Ny is preferably 1.535, more preferably 1.532.

Preferably the minimum of the refractive index Nz of the thickness direction of the polypropylene film of this invention is 1.480, More preferably, it is 1.489, More preferably, it is 1.501. Preferably the upper limit of Nz is 1.510, More preferably, it is 1.507, More preferably, it is 1.505.

(Film crystallinity)

The polypropylene film of this invention has the following high crystalline characteristics.

The lower limit of the crystallinity of the polypropylene film of the present invention is preferably 55%, more preferably 56%, still more preferably 57%, particularly preferably 58%, most preferably 59%. When the degree of crystallinity of the film is less than 55%, the heat shrinkage at high temperature may increase. The upper limit of the crystallinity of the polypropylene film of the present invention is preferably 85%, more preferably 80%, still more preferably 79%, particularly preferably 78%, most preferably 77%. When the crystallinity of the film exceeds 85%, realistic manufacture may be difficult. The crystallinity of the film can be adjusted by a method such as reducing or eliminating the copolymerized monomer, increasing the low molecular weight component, and setting the stretching temperature and the heat setting temperature to a high temperature.

Preferably the minimum of the melting peak temperature of the polypropylene film of this invention is 168 degreeC, More preferably, it is 169 degreeC. When melting peak temperature of a film is 168 degreeC or more, the thermal contraction rate in high temperature may become small. Preferably the upper limit of the melting peak temperature of the polypropylene film of this invention is 180 degreeC, More preferably, it is 177 degreeC, More preferably, it is 175 degreeC. When melting peak temperature of a film is 180 degrees C or less, manufacture may become easy practically. The melting peak temperature can be adjusted by reducing or eliminating the copolymerized monomer, increasing the low molecular weight component, and setting the stretching temperature and the heat setting temperature to a high temperature.

In the conventional polypropylene film, even when the melting peak temperature is around 170 ° C., the peak rises from the vicinity exceeding 140 ° C. when measured with a differential scanning calorimeter (hereinafter also referred to as DSC). Start), and even if heat resistance at 140 ° C. can be expected, thermal contraction rate rapidly increased at 150 ° C. However, in the polypropylene film of this invention, there is no peak rise even at 150 degreeC, and the polypropylene film of this invention is thought to be low in heat shrinkability even at 150 degreeC.

The polypropylene film of this invention can maintain a physical property even if exposed to 150 degreeC or more environment, and can be used also in the high temperature environment which was not conceivable with the conventional polypropylene film. In addition, melting | fusing start can be calculated | required from a DSC chart.

The lower limit of the degree of crystallinity at 150 ° C. is preferably 48%, more preferably 49%, still more preferably 50%, and particularly preferably 51%. When the degree of crystallinity at 150 ° C. is 48% or more, the thermal contraction rate at high temperature may be smaller. The upper limit of the degree of crystallinity at 150 ° C. is preferably 85%, more preferably 80%, still more preferably 79%, and particularly preferably 78% from a realistic standpoint. The degree of crystallinity at 150 ° C. can be within the range by reducing or eliminating the copolymerized monomer, increasing the low molecular weight component, and setting the stretching temperature and the heat setting temperature to a high temperature.

The melting peak temperature (Tmp), the crystallinity of the film, and the crystallinity at 150 ° C. can be obtained by using a differential scanning calorimeter (DSC).

The melting endothermic peak temperature obtained when it heated up to 230 degreeC by the ratio of 20 degreeC / min from room temperature was made into Tmp. Then, the heat of fusion is determined from the endothermic peak area, and the degree of crystallinity can be obtained by dividing the heat of fusion by 209 J / g, which is the heat of fusion of polypropylene complete crystals. In addition, the heat of fusion is determined from the endothermic peak area of 150 ° C. or more in the endothermic peak area, and the heat of fusion is divided by 209 J / g, which is the heat of fusion of polypropylene complete crystal, to determine the crystallinity in all samples at 150 ° C. In addition, the heat of fusion of polypropylene complete crystal is described in H. Bu, S. Z. D. Cheng, B. Wunderlich et al., Makromoleculare Chemie, Rapid Communication, Vol. 9, p. 75 (1988)], and the same values were used in the examples described later.

The lower limit of the thickness nonuniformity of the polypropylene film of the present invention is preferably 0%, more preferably 0.1%, still more preferably 0.5%, and particularly preferably 1%. The upper limit of the thickness nonuniformity of the polypropylene film of the present invention is preferably 20%, more preferably 17%, still more preferably 15%, particularly preferably 12%, most preferably 10%. . When thickness nonuniformity of a film is 0% or more and 20% or less, defect will hardly arise at the time of subsequent processing, such as coating and printing, and it is easy to use for the use which requires precision.

And the lower limit of the density of the polypropylene film of the present invention is preferably 0.910g / cm ³ and, more preferably 0.911g / cm ^3, more preferably 0.912g / cm ^3, more preferably 0.913g / cm ³ . If the film has a density of 0.910 g / cm ³ or more, the crystallinity is high and the heat shrinkage rate may be small.

And poly upper limit of the density of the polypropylene film of the present invention is preferably 0.925g / cm ³ and, more preferably 0.922g / cm ^3, more preferably 0.920g / cm ^3, more preferably 0.918g / cm ³ . If the density of the film is 0.925 g / cm ³ or less, the production may be facilitated in reality. The density of the film can be increased by increasing the draw ratio and temperature, increasing the heat setting temperature, and further offline annealing.

(Method for producing polypropylene film)

As a polypropylene film of this invention, although the uniaxial stretched film of a longitudinal direction (MD direction) or a lateral direction (TD direction) may be sufficient, it is preferable that it is a biaxially stretched film. In the case of biaxial stretching, it may be continuous biaxial stretching or simultaneous biaxial stretching.

By extending | stretching and manufacturing a polypropylene film, the film with a low thermal contraction rate can be obtained also at 150 degreeC which was not anticipated with the conventional polypropylene film.

Although the manufacturing method of the film of the sequential biaxial stretching of longitudinal stretch-horizontal stretch which is the most preferable example below is demonstrated, the manufacturing method of a polypropylene film is not limited to this.

First, the polypropylene resin is heated and melted by a single screw or twin screw extruder and extruded onto a cooling roll to obtain an unstretched sheet. As melt-extrusion conditions, it is set to 200-280 degreeC as resin temperature, and it extrudes in a sheet form from a T die, and solidifies by cooling with a cooling roll of 10-100 degreeC temperature. Then, the film is stretched 3 to 8 times in the longitudinal direction (MD direction) with a stretching roll at 120 to 160 ° C, and then 155 ° C to 175 ° C, preferably 157 ° C to 170 ° C in the width direction (TD direction). Stretch at 4 to 15 times the temperature.

Further, heat treatment (heat fixation) is performed while relaxing (relaxing) 1 to 15% at an ambient temperature of 165 to 175 캜, preferably 166 to 173 캜.

The roll film can be obtained by carrying out the corona discharge process to at least one surface to the polypropylene film obtained in this way as needed, and then winding up by a winder.

The lower limit of the draw ratio in the MD direction is preferably 3 times, more preferably 3.5 times. When the draw ratio of MD direction is less than 3 times, it may become thickness nonuniformity. Preferably the upper limit of the draw ratio of MD direction is 8 times, More preferably, it is 7 times. When the draw ratio in MD direction exceeds 8 times, it may become difficult to continue extending | stretching in the TD direction performed continuously.

Preferably the minimum of the temperature at the time of extending | stretching of MD direction (henceforth extending | stretching temperature) is 120 degreeC, More preferably, it is 125 degreeC, More preferably, it is 130 degreeC. When the extending | stretching temperature of MD direction is less than 120 degreeC, a mechanical load may become large, thickness nonuniformity may become large, or surface roughening of a film may arise. Preferably the upper limit of extending | stretching temperature of MD direction is 160 degreeC, More preferably, it is 155 degreeC, More preferably, it is 150 degreeC. The higher the stretching temperature in the MD direction is preferable for lowering the heat shrinkage ratio, but may be attached to the roll and may not be able to extend.

It is preferable to preheat a film before extending | stretching in a TD direction. In order to raise a film temperature rapidly to the extending | stretching temperature of a TD direction, Preferably the said preheating temperature (henceforth a preheating temperature) is set to 10-15 degreeC higher than the extending | stretching temperature of a TD direction.

The lower limit of the draw ratio in the TD direction is preferably 4 times, more preferably 5 times, still more preferably 6 times. When the draw ratio in the TD direction is less than 4 times, there may be a thickness nonuniformity. Preferably the upper limit of the draw ratio of a TD direction is 15 times, More preferably, it is 14 times, More preferably, it is 13 times. When the draw ratio in the TD direction exceeds 15 times, the heat shrinkage rate may increase or break during stretching.

Stretching in the TD direction can be performed at a higher temperature than a conventional polypropylene film, and the lower limit of the stretching temperature in the TD direction is preferably 155 ° C, and more preferably 157 ° C. If the extending | stretching temperature of a TD direction is less than 155 degreeC, it may not be fully softened and it may fracture | rupture or heat contraction rate may become high. Preferably the upper limit of extending | stretching temperature of a TD direction is 175 degreeC, More preferably, it is 170 degreeC. In order to lower the heat shrinkage rate, the higher the temperature is, the better, but when the stretching temperature in the TD direction exceeds 175 ° C, the low molecular weight component may melt and recrystallize, resulting in surface roughening or whitening of the film.

It is preferable to heat-fix the film after extending | stretching by heat processing. The heat fixation can be performed at a higher temperature than the conventional polypropylene film, and the lower limit of the heat treatment temperature (hereinafter referred to as heat fixation temperature) for performing heat fixation is preferably 165 ° C, more preferably 166 ° C. to be. If the heat setting temperature is less than 165 ° C, the heat shrinkage rate may increase. In addition, in order to lower the heat shrinkage rate, a long time is required, and the productivity may be lowered. Preferably the upper limit of heat setting temperature is 175 degreeC, More preferably, it is 173 degreeC. When the heat setting temperature exceeds 175 ° C, the low molecular weight component may melt and recrystallize, resulting in surface roughening or whitening of the film.

It is desirable to relax at the time of heat setting. The lower limit of the relaxation rate is preferably 1%, more preferably 2%. If the relaxation rate is less than 1%, the heat shrinkage rate may increase. The upper limit of the relaxation rate is preferably 15%, more preferably 10%. When the relaxation rate exceeds 15%, the thickness nonuniformity may increase.

In addition, in order to reduce the thermal contraction rate, the film produced at the said process may be once wound up in roll shape, and you may anneal off-line.

The lower limit of the temperature to be annealed offline (hereinafter, referred to as offline annealing temperature) is preferably 160 ° C, more preferably 162 ° C, and even more preferably 163 ° C. If offline annealing temperature is less than 160 degreeC, the effect of annealing may not be acquired. Preferably the upper limit of offline annealing temperature is 175 degreeC, More preferably, it is 174 degreeC, More preferably, it is 173 degreeC. When offline annealing temperature exceeds 175 degreeC, transparency may fall or thickness nonuniformity may become large.

The lower limit of the time of annealing off-line (hereinafter, referred to as an offline annealing time) is preferably 0.1 minutes, more preferably 0.5 minutes, still more preferably 1 minute. If the offline annealing time is less than 0.1 minutes, the effect of annealing may not be obtained. The upper limit of the offline annealing time is preferably 30 minutes, more preferably 25 minutes, still more preferably 20 minutes. If offline annealing time exceeds 30 minutes, productivity may fall.

Although the thickness of a film is set according to each use, the minimum of the thickness of a film becomes like this. Preferably it is 2 micrometers, More preferably, it is 3 micrometers, More preferably, it is 4 micrometers. The upper limit of the thickness of the film is preferably 300 µm, more preferably 250 µm, still more preferably 200 µm, particularly preferably 150 µm, and most preferably 100 µm.

The polypropylene film thus obtained is usually formed into a roll having a width of 2000 to 12000 mm and a length of about 1000 to 50000 m, and wound in a roll shape. Moreover, it slit according to each use, and is provided as a slit roll about 300-2000 mm in width and about 500-5000 m in length.

The polypropylene film of this invention has the outstanding characteristic which does not exist conventionally as mentioned above.

When the polypropylene film of this invention is used as a film for in-mold labels, since heat resistance is high, the film shrinkage by the heat at the time of in-mold process is not seen, an external appearance is favorable, and a curl is also small. In addition, since the rigidity is high, the handling at the time of in-mold processing is improved.

This application claims the benefit of priority based on Japanese Patent Application No. 2012-176995 for which it applied on August 9, 2012. The entire contents of the specification of Japanese Patent Application No. 2012-176995, filed August 9, 2012, are incorporated herein by reference.

Example

Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited to these Examples. The measuring method of the physical property in an Example is as follows.

1) Melt flow rate (MFR, g / 10 min)

In accordance with JIS K 7210, the temperature was measured at 230 ° C. and a load of 2.16 kgf.

2) molecular weight and molecular weight distribution

Molecular weight and molecular weight distribution were calculated | required by the monodisperse polystyrene reference | standard using the gel permeation chromatography (GPC).

The use column and solvent in GPC measurement are as follows.

Solvent: 1,2,4-trichlorobenzene

Column: TSKgel GMH _HR- H (20) HT × 3

Flow rate: 1.0ml / min

Detector: RI

Measuring temperature: 140 ℃

The number average molecular weight (M _n ), the mass average molecular weight (M _w ), the Z average molecular weight (M _z ), and the Z + 1 average molecular weight (M _{z + 1} ) are respectively determined for each elution position of the GPC curve obtained through the molecular weight calibration curve. by the number of molecules (N _i) having a molecular weight (M _i) defined by the following equation.

The number-average molecular _{weight: M n = Σ (N i} · M i) / ΣN i

Mass average molecular weight: M _w = Σ (N _i M _i ² ) / Σ (N _i M _i )

Z-average molecular _{weight: M z = Σ (N i} · M i 3) / Σ (N i · M i 2)

Z + 1-average molecular _{weight: M z + 1 = Σ (} N i · M i 4) / Σ (N i · M i 3)

Molecular weight distribution: M _w / M _n , M _{z + 1} / M _n

In addition, and the molecular weight of the peak position of the GPC curve to M _p.

When the base line is not clear, the base line is set in the range up to the lowest position of the gentle region on the high molecular weight side of the elution peak closest to the eluting peak of the standard material.

From the obtained GPC curve, peak separation was carried out with two or more components having different molecular weights. The molecular weight distribution of each component was assumed to be a Gaussian function, and was set such that each peak width was M _w / M _n = 4. The average molecular weight was computed from the curve of each obtained component, respectively.

Moreover, the ratio of the component used as the molecular weight 10,000 or less in the whole polypropylene resin which comprises the film, and the ratio of the component used as the molecular weight 100,000 or less were calculated | required from the GPC curve of the whole polypropylene resin which comprises a film.

3) stereoregularity

Measurement of mmmm and meso mean chain length was performed using ¹³ C-NMR. mmmm is determined according to the method described in Zambelli et al., Macromolecules, Vol. 6, p. 925 (1973), and the meso mean chain length is described in chapter 2 (1977) of “Polymer Sequence Distribution” by JC Randall (Academic). Press, New York)].

NMR measurement was carried out using the AVANCE 500 manufactured by Bruker, and 200 mg of the sample was dissolved in 135: 2 mixture of o-dichlorobenzene and heavy benzene at 135 degreeC, and it implemented at 110 degreeC.

4) Density (g / cm ³ )

The density of the film was measured by the density gradient pipe method in accordance with JIS K7112.

5) Melting peak temperature (Tmp, ℃)

The thermal measurement was performed using the DSC-60 differential scanning calorimeter made by Shimadzu Corporation. About 5 mg was cut out from the film to make a sample, and the sample was enclosed in the aluminum pan for a measurement. It heated up from room temperature to 230 degreeC by the ratio of 20 degree-C / min, and made the melting peak temperature of a sample into Tmp.

6) Crystallinity

The heat of fusion (ΔHm, J / g) was determined from the endothermic peak area in the DSC melting profile, and the crystallinity was determined by dividing the value of ΔHm by 209 J / g, which is the heat of fusion of polypropylene complete crystal.

The heat of fusion (ΔHm ', J / g) was obtained from an endothermic peak area of 150 ° C or higher in the DSC melting profile, and the value of ΔHm' was divided by 209J / g, which is the heat of fusion of polypropylene complete crystal, at 150 ° C. The crystallinity degree in all the samples was calculated | required.

7) Room temperature xylene solubles (CXS, mass%)

After dissolving 1 g of polypropylene samples in 200 ml of boiling xylene, after cooling, the mixture was recrystallized in a constant temperature water bath at 20 ° C. for 1 hour, and the ratio to the original sample amount of the mass dissolved in the filtrate was CXS (mass%).

8) Thermal Shrinkage (%)

It measured based on JISZ1712. That is, the polypropylene film was cut in the MD and TD directions by the length of 200 mm by 20 mm width, respectively, and it suspended in the hot air oven, and heated for 5 minutes. The length after heating was measured, and thermal contraction rate was calculated | required by the ratio of the contracted length with respect to the original length.

9) Young's modulus (GPa)

Young's modulus of MD and TD directions was measured at 23 degreeC based on JISK7127.

10) Haze (%)

It was measured according to JIS K 7105.

11) refractive index

It was measured using the Atago refractometer manufactured by Atago. The refractive indexes along the MD and TD directions were respectively Nx and Ny, and the refractive indexes in the thickness direction were Nz.

12) surface orientation coefficient

The surface orientation coefficient (P) was calculated from Nx, Ny, and Nz measured in 11) using the following formula.

P = [(Nx + Ny) / 2] -Nz

13) thickness non-uniformity

The square sample of length 1m was cut out from the wound film roll, and it divided into 10 equal parts in MD direction and TD direction, respectively, and prepared 100 samples for a measurement. The thickness was measured with a contact film thickness meter almost at the center of the sample for measurement.

The average value of obtained data of 100 points was calculated | required, the difference (absolute value) of a minimum value and the maximum value was calculated | required, and the value which divided the absolute value of the difference of a minimum value and the maximum value by the average value was made into the film thickness nonuniformity.

(Example 1)

As the polypropylene resin _{M w / M n = 7.7,} M z + 1 / M n = 140, MFR = 5.0 / 10 bun, mmmm = 97.3% propylene homopolymer (Nippon Polypropylene Co., manufactured by NOVA TECH (registered Trademark) PP "SA4L") (hereinafter referred to as "PP-1") was used. Using a 60 mm extruder, extruded into a sheet form from a T die at 250 ° C., cooled and solidified with a 30 ° C. cooling roll, stretched at 4.5 times in the longitudinal direction (MD direction) at 135 ° C., and then both ends were clipped. Then, the product was led to a hot air oven, preheated at 170 ° C., stretched 8.2 times in the transverse direction (TD direction) at 160 ° C., and then heat-treated at 168 ° C. while relaxing at a relaxation rate of 6.7%. Then, the corona treatment was performed to one side of the film, and it wound up by the winder. The thickness of the film obtained in this way was 20 micrometers, the characteristic of the polypropylene resin, etc. were shown in Table 1, 2, film forming conditions in Table 3, and the physical property of the obtained film in Table 5. As shown in Table 5, the film with low thermal contraction rate and high Young's modulus was obtained. The DSC chart of the stretched propylene film of Example 1 is shown in FIG.

An adhesive film (TM-386 manufactured by Toyo Moton Corporation) was applied to one side of the polypropylene film of Example 1, and a polypropylene film was further laminated thereon, thereby producing a laminate film that would be a polypropylene film / adhesive / polypropylene film. It was.

This laminating processing conditions are using a gravure type laminator, the unwinding tension 50N / m, the winding tension 55N / m, the adhesive coating amount is 0.6 g / m ² , the drying temperature 90 ℃, drying time 10 seconds. After carrying out heat aging for 24 hours at 40 degreeC atmosphere temperature, this laminated processed product was cut out in the rectangle of the size of 5 cm in a flow direction (MD direction) and 10 cm in a vertical direction (TD direction). Thereafter, the rectangles were seasoned at 23 ° C. under a 65% Rh environment, and the curl amount was measured on a horizontal band. As for the curl amount, the floating amount from the horizontal band with respect to the upper side when the film which apply | coated the adhesive agent for the first time to the upper side was read in millimeters, the average value of the label 4 corner was made into the curl amount, and the curl amount of the label was shown in Table 5.

(Example 2)

To 90 mass parts of said "PP-1", 10 mass parts of low molecular weight polypropylenes (the Mitsui Chemical Co., Ltd. high wax "NP105") of molecular weight 10000 are added, and it is set as 100 mass parts in total, and it is a 30 mm twin screw extruder. Melt kneading was carried out to obtain pellets of the mixture "PP-2". This pellet was obtained by the method similar to Example 1. Table 5 shows the properties of the polypropylene resin in Tables 1 and 2, the film forming conditions in Table 3, and the physical properties of the obtained film and the curl amount of the labels.

(Example 3)

The "PP-1", with respect to 70 parts by weight of _{M w / M n = 4.6,} M z + 1 / M n = 22, MFR = 120g / 10 bun, mmmm = 98.1% of propylene homopolymer, and the addition section 30 by weight Dry blending gave a mixture "PP-3". The film was obtained by the method similar to Example 1 using "PP-3". Table 5 shows the properties of the polypropylene resin in Tables 1 and 2, the film forming conditions in Table 3, and the physical properties of the obtained film and the curl amount of the labels.

(Example 4)

Using the said "PP-1", the film was obtained by the method similar to Example 1 except having set preheating temperature to 173 degreeC, extending | stretching temperature of the TD direction, and heat setting temperature to 167 degreeC. Table 5 shows the properties of the polypropylene resin in Tables 1 and 2, the film forming conditions in Table 3, and the physical properties of the obtained film and the curl amount of the labels.

(Example 5)

The film was obtained by the method similar to Example 2 except having extended | stretched 5.5 times in the longitudinal direction and 12 times in the horizontal direction. Table 5 shows the properties of the polypropylene resin in Tables 1 and 2, the film forming conditions in Table 3, and the physical properties of the obtained film and the curl amount of the labels.

(Example 6)

Using the film produced in Example 1, heat treatment (offline annealing) was performed at 170 ° C. for 5 minutes in a tenter type hot air oven. Table 5 shows the properties of the polypropylene resin in Tables 1 and 2, the film forming conditions in Table 3, and the physical properties of the obtained film and the curl amount of the labels.

(Example 7)

As the polypropylene resin _{M w / M n = 8.9,} M z + 1 / Mn = 110, MFR = 3.0g / 10 bun, mmmm = 97.1% of a propylene homopolymer (Samsung Total (Co., Ltd.) "HU300") (hereinafter referred to as Polypropylene film was obtained in the same manner as in Example 1 except that the preheating temperature was 171 ° C, the stretching temperature in the TD direction was 161 ° C, and the heat setting temperature was 170 ° C. . Table 5 shows the properties of the polypropylene resin in Tables 1 and 2, the film forming conditions in Table 3, and the physical properties of the obtained film and the curl amount of the labels.

(Comparative Example 1)

Sumitomonoglen (manufactured by Sumitomogagaku Co., Ltd.) having M _w / M _n = 4, M _{z +1} / M _n = 21, MFR = 2.5 g / 10 min, ethylene amount = 0.6 mol% as a polypropylene resin Trademark) "FS2011DG3" (hereinafter referred to as "PP-5"), MD stretching temperature is 125 ℃, preheating temperature is 168 ℃, stretching temperature in the TD direction of 155 ℃, heat fixing temperature of 163 ℃ A film was obtained in the same manner as in Example 1 except for the above. Table 6 shows the characteristics of the polypropylene resin and the like, and the film forming conditions are shown in Table 4, and the physical properties of the obtained film and the curl amount of the labels are shown in Table 6. The DSC chart of the stretched propylene film of the comparative example 1 is shown in FIG.

(Comparative Example 2)

A film was produced in the same manner as in Comparative Example 1 except that the preheating temperature was 171 ° C, the stretching temperature in the TD direction was 160 ° C, and the heat setting temperature was 165 ° C. Table 6 shows the characteristics of the polypropylene resin and the like, and the film forming conditions are shown in Table 4, and the physical properties of the obtained film and the curl amount of the labels are shown in Table 6.

(Comparative Example 3)

As the polypropylene resin, a propylene homopolymer (hereinafter referred to as "PP-6") having M _w / M _n = 4.3, M _{z +1} / M _n = 28, MFR = 0.5 g / 10 min, and mmmm = 97.0% was used. And the film was obtained on the conditions similar to Example 7. Table 6 shows the characteristics of the polypropylene resin and the like, and the film forming conditions are shown in Table 4, and the physical properties of the obtained film and the curl amount of the labels are shown in Table 6.

(Comparative Example 4)

Poly as a polypropylene resin _{M w / M n = 2.8,} M z + 1 / M n = 9.2, MFR = 30g / 10 bun, mmmm = 97.9% of the propylene homopolymer of Nippon Poly Nova Technology of manufacturing propylene (note) PP " Triaxial stretching was performed in the same manner as in Example 1 using SA03 '' (hereinafter referred to as "PP-7"), but the film was not obtained by breaking at the time of stretching in the transverse direction. Table 1 and 2 show the characteristics of the polypropylene resin, and film forming conditions are shown in Table 4 below.

Since the polypropylene film of the present invention has high heat resistance and rigidity, it is not only suitable as a molded label with a small curl, but also eliminates the need to use a thick film for the prevention of curl, or eliminates the need for using a deodorizing product, thereby reducing the cost as a label. It is also possible to expect superiority such as lowering.

Claims (4)

As a film containing a polypropylene resin, the heat shrinkage in the MD direction and the TD direction at 150 ° C is both 9% or less, the Young's modulus in the MD direction is 2 GPa or more, the Young's modulus in the TD direction is 4 GPa or more, and the haze is 6% The surface orientation coefficient is 0.0125 or more, and the crystallinity degree in 150 degreeC is 48% or more, The polypropylene film for in-mold labels characterized by the above-mentioned. The polypropylene film according to claim 1, wherein the lower limit of the isotactic meso pentad fraction of the polypropylene resin constituting the film is 96%. The polypropylene film of Claim 1 or 2 whose upper limit of the amount of copolymerization monomers of the polypropylene resin which comprises a film is 0.1 mol%. The polypropylene film of Claim 1 or 2 whose normal temperature xylene soluble content of the polypropylene resin which comprises a film is 7 mass% or less.

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