JPH02294337A - Highly transparent propylene polymer film or sheet - Google Patents

Abstract

PURPOSE:To obtain the title odorless film or sheet particularly suitable for packaging articles with its contents desired to be visibly recognized, by extrusion forming, under specified conditions, of a propylene polymer composition containing a specific methylbutene-1 polymer. CONSTITUTION:The objective film or sheet can be obtained by extrusion forming of a propylene polymer composition containing 0.003-0.5wt.% of a 3 methylbutene-1 polymer >303 deg.C in melting point and 2-50sec in crystallization time under such conditions that a draft ratio expressed by relationship I (G is width of die slit; t is film thickness; pm is resin density; pf is film density; BUR is blow-up ratio; for T-die forming, BUR=1) falls between 1 and 60 and a cooling rate index tau expressed by relationship II (tau is cooling rate index (sec); AG is distance between cooling mandrel and the air gap in T-die forming or the die in inflation forming (cm); V1 is take-up speed (cm/sec); V0 is linear velocity of the molten resin at the die exit (cm/sec)) falling at or below 7.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to highly transparent propylene polymer films or sheets. More specifically, specific 3-methylbutene-l
The present invention relates to a propylene polymer film or sheet containing a polymer and having excellent optical properties.

[Conventional technology and its issues]

Propylene polymer film has good optical properties such as transparency and gloss, mechanical properties such as tensile strength and rigidity, and moisture resistance, and is also inexpensive, so it is used in a wide range of applications such as food packaging, textile packaging, etc. It is used. However, depending on the application, these properties are not fully satisfied, and in particular, there are problems with optical properties, which greatly limits the field of use.

For this reason, various attempts have been made to improve the optical properties of propylene polymer films. For example, the addition of aluminum salts of aromatic carboxylic acids, dibenzylidene sorbitol, substituted dibenzylidene sorbitol, etc. It is known that the above-mentioned problems can be alleviated by acting as a nucleating agent for crystal nuclei (hereinafter referred to as a nucleating agent). However, all of these nucleating agents are low molecular weight substances and have the disadvantages of odor and bleeding problems, contamination of cooling rolls during molding, and deterioration of thermal stability, making long-term operation difficult. be.

On the other hand, several methods have been proposed in which a polymer compound is used as a nucleating agent to improve the drawbacks of these nucleating agents. For example, JP-A-60-/. ? ? 7.7/, a method is proposed in which a vinylcycloalkane polymer having 6 or more carbon atoms is used as a polymer nucleating agent. Although this method gives relatively good results, vinylcycloalkanes are expensive, and their high boiling points require complicated washing operations in the monomer removal process. There are several problems in producing process polymers.

3-Methylbutene-1 is cheaper than vinylcycloalkanes, and has a low boiling point and is easy to handle.
Although several attempts have been made to improve transparency by using methylbutene-7 polymer as a polymer nucleating agent, the expected effects have not yet been obtained.

For example, in JP-A-4/-2//elf, the transparency of a 0.1 III sheet obtained by melt extruding a propylene homopolymer containing 12 ppm by weight of 3-methylbutene-1 polymer was evaluated. However, almost no effect of improving transparency was observed compared to that containing no 3-methylbutene-7 polymer.

Also, Tokukai Showa O=/3? 3L also describes the transparency of a 11-tight press sheet of a propylene polymer containing 200 pm by weight of 3-methylbutene-1 polymer, but this is also compared to one that does not contain 3-methylbutene-1 polymer. However, almost no improvement effect was observed.

In addition, JP-A/-13/20'l, JP-A 62-2
Sll and JP-A. ? -69109 etc. also have descriptions of propylene polymers containing 3-methylbutene-1 polymer, but these are all aimed at improving crystallinity and rigidity, and there is no mention of improving transparency. .

In view of the current situation as described above, as a result of intensive studies, the present inventors determined the content of 3-methylbutene-1 polymer in the propylene polymer to be specific and selected appropriate molding conditions. The present invention was achieved by discovering that a propylene polymer film or sheet with excellent transparency can be obtained by the above method.

That is, the gist of the present invention is that the melting point exceeds 303°C.
-Methylbutene-1 polymer at 0.00 J to θ. jw
t% and whose crystallization time is 2 to 50 seconds, the draft rate shown by the following formula (1) is /
-60, a highly transparent propylene polymer film or sheet obtained by extrusion molding into a film or sheet under conditions where the cooling rate index expressed by the following formula (II) is 7 or less.

In the formula, the symbols are as follows, and in the case of T-die molding, it is expressed as BUR=/.

τ: Cooling rate index (seconds) AG: Air gap (distance between T-die and cooling roll) in the case of T-die molding or distance between the goo and the cooling mandrel (cWL) in the case of inflation molding v1: Take-up speed (α/sec) ■. : Linear velocity of molten resin at die exit (an/sec) In the present invention, the higher the degree of crystallinity of the 3-methylbutene-1 polymer used, the greater the effect of improving optical properties. One measure of the degree of crystallinity is the melting point or heat of fusion measured with a differential scanning calorimeter.

The melting point of the 3-methylbutene-7 polymer used in the present invention is higher than soJ°C, and the heat of fusion is preferably iscat / 1 or more, and more preferably J-methylbutene-1
The melting point of the polymer is higher than 3θta℃ and the heat of fusion is tAca
l/y or more.

The 3-methylbutene-1 polymer of the present invention may be a copolymer with other α-olefins having from 1 to 1 carbon atoms as long as the above conditions are satisfied.

The catalyst system used to obtain such a 3-methylbutene-1 polymer is a Ziegler-Natta catalyst that provides a polymer with particularly high stereoregularity.

Examples of such catalysts include Tokko Sho SE-27G7/
No. Publication, same! ;! f-g'l! FI No. 56-g
'l! ; Publication No. 2, Publication j&-ff00.7, Publication No. 3
It is described in the -3-39/4k publication, the same ss-itIosti publication, etc.

For example, the aluminum content is expressed as the atomic ratio of aluminum to titanium. A catalyst system comprising a solid titanium trichloride catalyst complex containing a complexing agent and an organic aluminum 9 or further an electron-donating compound such as an ether, ester, amine, or amide as a third component is preferred. used for. In addition, a titanium-based catalyst supported on a magnesium compound can also be used satisfactorily.

The amount of 3-methylbutene-1 polymer in the propylene polymer is preferably 0.00 J to 0.3% by weight, more preferably o. o o z〜θ. It is outside the 3 weight range.

If the content of the J-methylbutene-1 polymer is too small, the effect of improving the crystallization rate, which will be described later, will be insufficient and the transparency will decrease. On the other hand, if the content of 3-methylbutene-1 polymer is too high, fish eyes may occur, the 3-methylbutene-i polymer itself or the crystallization rate may become too fast, resulting in decreased transparency, increased cost, etc. I don't like the problem.

By setting the content of the 3-methylbutene-1 polymer within the above range, the crystallization rate of the brobylene polymer will be 2 to 3.
The range is 0 seconds. When the crystallization rate is λ seconds or less, the crystallization rate is too fast, and the adhesion of the propylene polymer film to the chill roll deteriorates, resulting in a decrease in transparency. Moreover, if the crystallization rate is Sθ seconds or more, the growth of spherulites will be impaired or the transparency will be reduced.

The method for producing the propylene polymer composition containing 3-methylbutene-1 polymer used in the present invention includes the following steps: 1) Polymerizing 3-methylbutene-1 using a Ziegler-Natta catalyst or the like to form a 3-methylbutene-7 polymer. Subsequently, homopolymerization of propylene or propylene and other α-
Perform copolymerization with olefin.

2) Propylene is homopolymerized or copolymerized with other α-olefins using a Ziegler-Natsume catalyst, followed by polymerization of 3-methylbutene/in the presence of a brobylene polymer.

3) A masterbatch polymer is produced by the method 1) or 2) above, and this is mixed with brobylene alone or a copolymer of propylene and another α-olefin.

4) Methods include mixing separately polymerized 3-methylbutene-1 polymer and propylene alone or a copolymer of propylene and other α-olefins, but in terms of the balance between performance and productivity. Method 3) is the most preferred method.

That is, in the method of 1) in which 3-methylbutene-1 is polymerized and then propylene is polymerized, a decrease in activity or stereoregularity may occur during propylene polymerization.
In addition, in method 2), after a large amount of brobylene is polymerized, a trace amount of 3-methylbutene-1 is polymerized, and switching of monomers is complicated.

In addition, since it is necessary to make a polymer containing 3-methylbutene-1 for each grade of polypropylene, it is necessary to produce a polymer containing 3-methylbutene/polymer, especially in a continuous polymerization plant where each grade is produced continuously. Many problems arise due to contamination with unnecessary grades.

On the other hand, the above-mentioned problem does not occur in a method in which a propylene polymer master patch containing a relatively large amount of 3-methylbutene-1 polymer is produced and mixed with a propylene polymer prepared by a conventional method.

In the case of method 3), the content of the 3-methylbutene-7 polymer in the 3-methylbutene-1 polymer-containing brobylene polymer composition produced in method 1) or method 2) is not particularly limited, but is 70% by weight or less. is preferable, and more preferably SQ weight % or less.

As a mixing method for the 3) method and the 4) method, general methods such as an extruder, a Prabender kneader, a roll, etc. may be used.

When mixing, it is desirable to knead at a temperature within a range that does not cause melting of the 3-methylbutene-1 polymer. Above 3-
The raw material propylene polymer to be mixed with methylbutene-1 polymer is propylene homopolymer (propylene homopolymer), or brobylene and other α
and block copolymers (the copolymerization proportion of ethylene or other α-olefins is at most 75% by weight, preferably o.i.s.o. weight %).

Melt flow of the above polypropylene resin} (MF
It is abbreviated as R. ) may be any one used in the film field, but according to the method of JIS K-7210, 230
°C, load co. The value measured in zxkg, usually θ. ．． 2~
θ11//0 minutes, preferably θ. Ku~ts
A substance in the range of g//o minutes is preferably used.

In addition, various additives commonly added to polypropylene resins, such as antioxidants, lubricants, antistatic agents, anti-blocking agents, EP rubber, silica, and other known polymer fillers, may be appropriately mixed and used. It is possible.

In the present invention, a propylene polymer composition containing the above-mentioned 3-methylbutene-1 polymer is extruded into a film or sheet with the draft rate and cooling rate index set under specific conditions shown below.

For forming the film or sheet, a conventional film or sheet forming apparatus and forming method, such as an inflation molding method using a circular die, a T-die molding method using a T-die, etc., are employed.

When performing inflation molding, the resin temperature should be
2gθ°C, blow-up ratio 0.5-q. It is preferable to conduct the cooling under conditions in which the draft rate is 1 to 60, preferably 3 to 50, and more preferably the cooling rate index (τ) is 7 or less, preferably 6 or less. As the inflation molding, a water-cooled inflation molding method is particularly preferably used.

In addition, when performing T-die molding, the resin temperature should be set at 79θ to 31
0°C, chill roll temperature 0~100°C, draft rate 1~60, preferably 3~SO, more preferably << is DA~
The cooling rate index (τ) is preferably 7 or less, preferably 6 or less.

Note that in the present invention, a draft book is obtained by the following formula (1).

In addition, in the case of T-die molding, it is expressed as BUR=/.

If the draft rate is less than the lower limit, the optical properties of the film or sheet obtained by molding will deteriorate, and if it is higher than the upper limit, the molding stability will decrease, which is not preferred.

Further, the cooling rate index (τ) indicates the residence time (seconds) until the molten resin is extruded from the die and solidified, and is expressed by the following formula (II).

In the formula, the symbols are as shown below. In the present invention, the cooling rate index (τ) is set to a range of 7 or less. The cooling rate index (τ) can be controlled to a predetermined value by varying each of the requirements in equation (II) above; for example, in the case of inflation molding, by varying the distance t from the gouer to the mandrel. Or,
In the case of T-die molding, the distance between the T-die and the cooling roll can be changed, and ■. In order to change the cooling rate index or V1, it may be controlled by changing the extrusion rate of the extruder or the take-up speed t of the take-off device, and a predetermined cooling rate index is set by combining these factors. If the cooling rate index (τ) exceeds the upper limit, the optical properties of the film will deteriorate significantly, which is not preferable.

What is the thickness of the film or sheet in the present invention? It is preferable to use a material in the range of μm to 1000 μm.

The highly transparent polypropylene obtained in the present invention has excellent optical properties and odorlessness, and can be used for various purposes, and is particularly suitable for food packaging films.

〔Example〕

Examples will be shown below, but the present invention is not limited to the following examples as long as the gist of the invention is not exceeded. Physical property values in the following examples were measured according to the following methods.

1) Melt flow rate (VFR) JIS K-7210 (230℃, load: 76kg)
Measurements were made according to the following.

2) Transparency ■ Haze Measurements were performed according to ASTM D-/o03.

■ Parallel light transmittance Using Clarity Meter TM-10 model manufactured by Murakami Color Research Institute, set the total light transmittance to /00.
A spot was applied to the center of each part of the film piece, the film piece was rotated once, only a straight beam (parallel ray) was taken out, and the maximum amount of light was read to determine the parallel ray transmittance (%).

3) Crystallization temperature (Tc) Measurement was performed using a Perkin-Elmer DSC2CfM differential scanning calorimeter at a temperature increase/decrease rate of 0° C./min.

4) Crystallization rate Using the same differential scanning calorimeter as in 3), melt the sample twice under the conditions shown in Table 1 below, set the temperature to 73°K, and
After holding at 3°K for j minutes, 3 to 6°K at tIo°C/min.
The temperature drops to . ? ? The temperature is maintained at A'K, and the time taken to reach the top of the crystallization peak is measured.

Table 1 0 Catalyst Production Example At room temperature, purified toluene Sl5- was charged into an autoclave having a volume/liter that was sufficiently purged with nitrogen, and while stirring, n-butyl ether A i/,! iI (oz mol)
, titanium tetrachloride? 11.9. 81 (0.5mol
) and diethylaluminum chloride u L6Ii (
0.24<mol) was added to obtain a brown homogeneous solution. Then, the temperature was raised to 30°C. After 30 minutes, the temperature was raised to θ°C and maintained at 11O'G for 1 hour. Then 3211 tipon tetrachloride (o.t 7 mol
) and/j. ．． 1-9 tridecyl methacrylate} (o.os ffmol) was added? The temperature was raised to f°C. After being maintained at qg°C for λ hours, a granular purple solid was separated and washed with toluene to obtain solid titanium trichloride.

0 resin production example 1/ (Production of propylene polymer masterbatch containing 3-methylbutene-1 polymer) Diethylaluminum chloride/. 2 mmol t was added, and 700 cc of liquid 3-methylbutene/Y was further charged.

Next, the temperature was raised to 70°C, 97η of the solid catalyst component obtained in the catalyst production example was added, and 3-methylbutene-1 polymerization Y was carried out for 1 hour. Thereafter, after purging the entire amount of 3-methylbutene/4, diethylaluminum chloride. 7 rnmo
1 Methyl methacryly} 0. / 2 mmo
1 and H2 o. skg/crA, and further added propylene 7009 to carry out homopolymerization of propylene. After 30 minutes, propylene was sterilized, the catalyst was removed with a mixed solvent of imptanol and n-hexane, and 3-
A 7/11 propylene polymer composition was obtained, including a methylbutene-1 polymer.

The amount of 3-methylbutene/polymer produced in an experiment in which propylene polymerization was not conducted under the same polymerization conditions was/
0. It was g9.

The melting point of this 3-methylbutene-1 polymer is . ? //℃,
The heat of fusion was 2o cal/I.

The content of 3-methylbutene-7 polymer in the brobylene polymer composition calculated from the yield of the above-mentioned 3-methylbutene-tIJ combination is U. It was 0% by weight.

The MFR of this polymer is 0.2 7 11/ / 0 minutes;
The melting point is /A. 7. ll℃, crystallization temperature is lko6.6
It was ℃.

0 Resin Production Example 11 7 parts by weight of the eight polymers obtained in Resin Production Example 11 and 0.7 parts by weight of calcium stearate as a stabilizer, BH
T(2,A-di-tertiarybutylhydroxytoluene)0. , 2 parts by weight, Irganox IOIO {antioxidant manufactured by Ciba Geigy, Tetrakis [methylene-3 (
3/. t/-di-t-butyl-hydroxyphenyl)probionate]methane}θ. Og weight part was converted to propylene homobolymer l210F (MFR:
Da. lalto minute, melting point: / AO. 3°C, crystallization temperature: llλ. 3°C, crystallization rate: //7 seconds) after adding 100 parts by weight and mixing with a Henschel mixer! O t
The mixture was granulated into pellets using a ml extruder. The 3-methylbutene-1 polymer (nucleating agent) content of this resin composition is 0.05
Heavy weight, VFR is t. ．． The melting point was 762.3 °C, the crystallization temperature was / / 9.0 °C, and the crystallization rate was 3 l seconds.

Example 1 The pellets obtained in Resin Production Example-2 were processed using a JOm91T die extruder (die width lIocWL, clearance/.Om
) Chemical use, resin temperature 1gθ℃, extrusion rate 20kg/hr,
Melt extrusion was performed at a take-up rate of t o m /min, and the product was cooled and solidified using a chill roll at 60°C to obtain a T-die film having a thickness of 70 μm and a width of 4 Iocm. The transparency (haze, average light transmittance) of this film was evaluated and the results are shown in Table 1. Note that the linear velocity of the molten resin at the die exit is (Vo-Q/Pm-D-G
, Q = extrusion amount, ρm = melt density, D = die width, G = clearance). Also, the film density is J
Measured by IS K-Alt,o.

Examples Co-da and Comparative Example 1 The same procedures were carried out in actual mflJ/ except that the molding conditions shown in Table 1 were changed.

The results are shown in Table 1.

Comparative Examples λ to Example 1 The same procedure as in Example 1 was carried out except that pellets of polypropylene homobolymer 12 OFH manufactured by Mitsubishi Kasei Corporation were used alone and the molding conditions were as shown in Table 1. The results are shown in Table 1.

Comparative Examples S to 6 Except that in Example 1, the nucleating agent was changed to commercially available dibenzylidene sorbitol (manufactured by Marubishi Yuka Co., Ltd., trade name: Denon YK-/) (nucleating agent A) K, and the molding was performed under the molding conditions shown in Table 1. was done in the same way. The results are shown in Table 1.

Comparative Example ff-9 In Example 1, nucleating agent t commercially available i,3,t,4I-di(
Table 2
The molding was carried out in the same manner except that the molding conditions were as shown in . The results are shown in Table a.

Comparative Example 1O ~// In Example 1, commercially available P-talibutylpenzoic acid aluminum 9M (trade name AI-PTBBA, manufactured by Shell Chemical Co., Ltd.) (nucleating agent C) was used as the nucleating agent. The molding process was carried out in the same manner except that the molding conditions shown in 1 were used.

Table the results. 2K is shown.

Comparative Examples l-i. y In Example 1, the molding was carried out under the molding conditions shown in Table 2K, replacing the commercially available methylene bisacid phosphate sodium salt (?f' with the trade name MARKNA-//UY manufactured by Argus Chemical Co., Ltd.) (nucleating agent D) as the nucleating agent. Other than that, it was done in the same way.

The results are shown in Table 1.

〔Effect of the invention〕

The film or sheet of the present invention has excellent transparency and is odorless, and is suitably used as a packaging film or sheet for various articles including foods, especially for articles for which it is desirable to visually recognize the contents.

Claims (3)

[Claims] (1) The following (I
) A highly transparent propylene polymer film or sheet obtained by extrusion molding into a film or sheet under conditions where the draft rate is 1 to 60 as shown by the formula (II) below, and the cooling rate index is 7 or less as shown in the following formula (II) . Draft rate = (ρm/ρf)・(G/t)・(1/BU
R) ...... (I) In the formula, the starting numbers are as follows [G: Width of the die slit t: Thickness of the obtained film ρm: Density of the resin extruded from the die slit ρf: Thickness of the film Density BUR: Blow-up ratio] In the case of T-die molding, BUR is expressed as 1. τ=[(AG)/(V_1-V_0)]ln[(V_1
)/(V_0)]・・・・・・・・・・・・(II)[τ
: Cooling rate index (seconds) AG: Air gap (distance between T-die and cooling roll) in case of T-die molding or distance between die and cooling mandrel (cm) in case of inflation molding V_1: Take-up speed ( cm/sec) V_0: Linear velocity of molten resin at die exit (cm/sec) (2) In the film according to claim 1,
a propylene polymer in which a 3-methylbutene-1 polymer composition is polymerized in the presence of a 3-methylbutene-1 polymer;
A highly transparent propylene polymer stretched film, characterized in that it is obtained by mixing propylene polymers. (3) In the film described in claim 1, 3
- The methylbutene-1 polymer-containing propylene polymer composition is obtained by mixing a 3-methylbutene-1 polymer polymerized in the presence of a propylene polymer and a propylene polymer. Highly transparent propylene polymer stretched film.