JPH0739517B2 - Resin composition for shrink film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention has, for example, good low-temperature shrinkability, transparency, and
The present invention relates to a propylene copolymer-based resin composition suitable for a shrink film having excellent gloss, slipperiness, and blocking resistance.

<Prior Art> Films for polypropylene resin shrink wrapping have been used for a long time, and ethylene-propylene random copolymers, ethylene-butene-1-propylene ternary random copolymers, and the like have been stretched. Films are known (for example, JP-A-52-16588). Although these films have been used favorably due to less food hygiene and disposal problems, they are inferior in low-temperature shrinkability to shrink films made of polyvinyl chloride, and their improvement is desired. In order to improve the low temperature shrinkability, it has been known that it is necessary to be able to stretch at a lower temperature, but in order to make it possible,
It is necessary to reduce the crystallinity of the propylene-based copolymer. However, if the resin composition obtained by blending conventionally known silica as an anti-blocking agent in a propylene copolymer having a reduced crystallinity is stretched at a relatively low temperature, the transparency of the film becomes poor, and at the same time, There is a problem that blocking resistance and slipperiness are deteriorated, probably because of low crystallinity and softness.

On the other hand, a composition in which zeolite powder is added to highly crystalline polypropylene is known (Japanese Patent Publication No. 52-16134), but what is disclosed therein is a biaxially stretched film obtained by stretching at high temperature. is there. This film is a self-supporting film having rather unfavorable shrinkage characteristics, and the particle size of the added zeolite is as large as 2-3 .mu.m, and the addition amount is 0.2 parts or less, which is a relatively small amount. According to the knowledge of the present inventors, when the above-mentioned zeolite is added to a propylene-based copolymer having lower crystallinity and the stretching treatment is performed at a relatively low temperature, the transparency of the film is also lost and at the same time, It also has poor blocking properties and slipperiness.

Further, JP-A-58-213031 discloses that a polypropylene homopolymer having high crystallinity and an aluminosilicate powder of 0.
A film obtained by biaxially stretching a resin composition containing 2 parts at a high temperature (150 ° C.) is disclosed. However, according to the findings of the present inventors, a propylene-based copolymer having a lower crystallinity is added to the above aluminosilicate. If the powder is added in the same way and stretching is performed at a relatively low temperature, the transparency of the film is lost,
They have poor blocking resistance and slipperiness.

<Problems to be Solved by the Invention> In view of the above situation, the present invention has good low-temperature shrinkability obtained by stretching a propylene-based copolymer having relatively low crystallinity at relatively low temperature, and An object of the present invention is to provide a resin composition for obtaining a shrink wrapping film having excellent transparency, gloss, slipperiness, and blocking resistance.

<Means for Solving the Problems> The inventors of the present invention formed a resin composition in which a specific content of a specific antiblocking agent was added to a propylene copolymer having a Vicat softening point of a specific temperature or lower, and then stretching. It was found that a film for shrink wrapping having all of the above-mentioned various properties can be obtained by processing, and the present invention was completed.

That is, the present invention is a resin composition for a shrinkable film, which is obtained by adding 0.25 to 2.0 parts by weight of an aluminosilicate powder having an average particle size of 1 µ or less to a propylene copolymer having a Vicat softening point of 130 ° C or less.

The resin composition of the present invention is characterized in that it can be stretched at a relatively low temperature, and the stretched film has good low-temperature shrinkability and is excellent in transparency, gloss, slipperiness, and blocking resistance. That is.

The present invention will be described in detail below.

The propylene copolymer used in the present invention is a known crystalline one. For example, a well-known ethylene-propylene random copolymer or ethylene-butene-1-propylene random terpolymer having a comonomer content of 1 to 15 is used.
wt% and cold xylene soluble part (hereinafter referred to as CXS) 15w
In a blend composition of t% or less or a specific propylene-α-olefin copolymer shown below with these random copolymers, the blending ratio of the propylene-α-olefin copolymer is 20% by weight. More than that. Among these, the latter blend composition is preferable because it is easy to obtain good transparency even when stretched at a relatively low temperature.

The Vicat softening point of the propylene copolymer used in the present invention is 130 ° C or lower, preferably 125 ° C or lower, and more preferably 115 ° C or lower. If the Vicat softening point exceeds the upper limit, stretching at a relatively low temperature becomes impossible, and the low temperature shrinkability of the obtained film is unfavorable.

The above-mentioned specific propylene-α-olefin copolymer used as a preferred embodiment of the present invention is a known catalyst for stereoregular polymerization of α-olefins, that is, a so-called Ziegler-Natta catalyst, that is, the periodic table. IV-
A group VIII transition metal compound, an organic compound of a group I to III typical metal of the periodic table, and a third component such as an electron donating compound are used, and the polymerization method is a solvent polymerization method of polymerizing in a solvent, or It can be produced by a gas phase polymerization method of polymerizing in a gas phase. For example, it can be obtained by the method of polymerizing the copolymer (B) described in Japanese Patent Application No. 61-164505, but any polymer satisfying the conditions specified below may be used.

The propylene-α-olefin copolymer is a copolymer of propylene and α-olefin having 4 or more carbon atoms, or a copolymer of propylene, α-olefin having 4 or more carbon atoms and ethylene, and α having 4 or more carbon atoms of the copolymer. -Olefin content 8
-35 mol% The ethylene content of the copolymer is 5 mol% or less. The copolymer satisfies the condition that the cold xylene-soluble part of the copolymer is 15 to 70 wt%.

The propylene-α-olefin copolymer is used in combination with a small amount of α-olefin having 4 or more carbon atoms or ethylene as a comonomer. As the α-olefin having 4 or more carbon atoms, butene-1, pentene-1, hexene-
Examples thereof include 1,4-methyl-pentene-1 and the like, which may be used alone or in combination, but for example, butene-1 is preferable because it is difficult to liquefy when gas phase polymerization is carried out and a high partial pressure is obtained.

The content of α-olefin having 4 or more carbon atoms in the propylene-α-olefin copolymer is 8 to 35 mol%,
30 mol% is preferred. When the content of the α-olefin having 4 or more carbon atoms falls below the lower limit, the blend composition obtained by blending the propylene-α-olefin copolymer cannot be stretched at a relatively low temperature. Or, the transparency of the film after stretching is deteriorated, which is not preferable. Carbon number 4
If the above α-olefin content exceeds the upper limit, the slidability and blocking resistance of the stretched film are deteriorated, which is not preferable.

The ethylene content of the propylene-α-olefin copolymer is 5 mol% or less, preferably 3 mol% or less. When the ethylene content exceeds the upper limit, the transparency of the film is deteriorated with time, the blocking resistance and the slip are deteriorated, which is not preferable.

The cold xylene-soluble part (CXS) of the propylene-α-olefin copolymer is 15 to 70 wt%, more preferably 16 to 60 wt%. When CXS falls below the lower limit, the propylene-α
The blend composition obtained by blending the olefin copolymer is not preferable because it cannot be stretched at a relatively low temperature, or the transparency of the stretched film becomes poor.
If the CXS exceeds the upper limit, it is not preferable because the film after stretching has poor slip resistance and blocking resistance.

In obtaining a propylene copolymer as a preferred embodiment of the present invention by blending the propylene-α-olefin copolymer and the random copolymer, the blending ratio of the propylene-α-olefin copolymer is 20% by weight. Is over, 30
It is preferably at least wt%, more preferably at least 40 wt%. If the blending ratio of the propylene-α-olefin copolymer is below the lower limit, it is difficult to obtain good transparency of the film by stretching at a relatively low temperature, which is not preferable.

The melt index of the propylene copolymer used in the present invention is preferably 0.5 to 50 g / 10 minutes. If the melt index is lower than the lower limit, the processability is deteriorated, which is not preferable, and if the melt index is higher than the upper limit, the stretchability of the film is deteriorated, which is not preferable.

The aluminosilicate powder used in the present invention is a natural zeolite or a synthetic zeolite, or, for example, JP-A-58-21.
It is an amorphous aluminosilicate as shown in 3031 and may contain a basic component in addition to the essential components of the alumina component and the silica component.

The aluminosilicate powder used in the present invention has an average particle size (by Coulter counter) of 1 μm or less. If the average particle size exceeds 1 μ, the transparency of the film deteriorates when a resin composition containing it is stretched at a relatively low temperature, which is not preferable.

The oil absorption of the aluminosilicate powder used in the present invention is 10
It is preferably 0 (ml / 100 g) or less. The smaller the oil absorption is, the easier it is to improve the slipperiness of the film, which is preferable.

The resin composition of the present invention is obtained by adding 0.25 to 2.0 parts by weight of the aluminosilicate powder to the propylene copolymer defined above, and the addition amount is preferably 0.30 to 1.5 parts by weight. If the amount added is less than the lower limit, the film has poor blocking resistance and slippage, which is not preferable. If the amount added exceeds the upper limit, the transparency of the film deteriorates, which is not preferable.

In the present invention, a relatively low crystallinity propylene copolymer, in particular, for a propylene copolymer containing a specific propylene-α-olefin copolymer, fine aluminosilicate powder is not present in the past, and a large amount is added. Only with the resin composition described above, a film having good transparency and good blocking resistance and slipperiness was obtained for the first time by stretching at a relatively low temperature, which was unexpected.

A slip agent can be suitably added to the resin composition of the present invention.
Further, additives such as an antistatic agent, an antifogging agent, a stabilizer and a nucleating agent can be added. As the anti-blocking agent, at least the anti-blocking agent specified in the present invention may be contained in the specified amount, and non-specified anti-blocking agents may be used in combination.

A small amount of a polymer compound (for example, a hydrocarbon resin such as petroleum resin) can be added to the resin composition of the present invention. The resin composition of the present invention can be obtained by uniformly dispersing it by any known method. For example, a method of extrusion-melt blending after mixing with Henschel, a method of Banbury blending, and the like.

The resin composition of the present invention is suitably used as a film for shrink wrapping, but it is used after being stretched after forming the film. As a method for forming a film, a known processing method such as a T-die casting method or a water cooling inflation method can be adopted. As a method for performing the stretching treatment, known uniaxial stretching methods such as roll stretching, roll rolling and tenter transverse uniaxial stretching, as well as tenter biaxial stretching and tubular 2 are used.
A known biaxial stretching method such as axial stretching can be adopted. The stretching temperature is from room temperature to the melting point of the copolymer or lower, but the lower the Vicat softening point of the propylene copolymer, the easier the stretching at a lower temperature. The draw ratio is preferably 2 to 10 times. In this case, the MD and TD stretch ratios do not necessarily have to be balanced, and can be arbitrarily selected according to their respective uses. Moreover, you may heat-set.

The data and evaluations in Examples and Comparative Examples were carried out according to the following methods.

(1) Vicat softening point Compliant with ASTM D 1525 (2) Melt index (MI) Compliant with ASTM D 1238 (3) Haze value (Haze) Compliant with ASTM D 1003 (4) Sliding (μs ... static friction coefficient) ASTM D 1894 (5) Heat shrinkage rate A 5 cm square film sample is immersed in a glycerin bath at a predetermined temperature for 10 seconds, and the MD and TD shrinkage rates are measured.

(6) Blocking Two films are superposed on each other, and the condition is adjusted at 23 ° C. for 3 hours while applying a load of 20 kg per area of 25 cm ² . Then 2
Load increasing speed for a sheet of film in the direction perpendicular to the film surface
Peeling is performed at 10 g / min, and the maximum load (g) at that time is calculated and expressed in terms of 100 cm ^{2 of} film area.

(7) α-Olefin content in copolymer Measured using an infrared spectrophotometer. Butene-1 was quantified by a conventional method from the characteristic absorption at 770 cm ^-1 . In the measurement with the infrared spectrophotometer, propylene, butene-1, and the copolymer were quantified by preparing a calibration curve from the quantitative value by ¹³ C-NMR.

(8) Ethylene content in copolymer Using an infrared spectrophotometer, it was quantified by a conventional method from characteristic absorptions at 732 cm ⁻¹ and 720 cm ⁻¹ . In the measurement with an infrared spectrophotometer, a calibration curve was prepared and quantified by the quantified value of the ¹⁴ C-labeled ethylene copolymer measured by radiation.

(9) Cold xylene soluble part (CXS) After dissolving 5 g of the polymer in 500 ml of xylene, it is cooled to room temperature. Then, the mixture is left in a bath at 20 ° C. for 4 hours and then filtered, and the filtrate is concentrated, dried, dried and weighed.

Hereinafter, the present invention will be described in more detail with reference to Examples.
The present invention is not limited to the examples as long as the gist thereof is not exceeded.

<Example> Example 1 Ethylene-butene-1-propylene random terpolymer (2.1 wt% ethylene, butene-1 content 5.5 wt%, Vicat softening point 123 ° C, CXS 4.3 wt%, MI 5.9 g / 10 min) As a stabilizer, BHT 0.1 part, Mizusawa Chemical's Shilton AMT (amorphous aluminosilicate powder, average particle size 0.8μ, oil absorption 62ml / 100g)
Of 0.3 parts and 0.2 parts of erucic acid amide were mixed with a Henschel mixer, and melt-blended with a 65φ extruder to obtain a resin composition. The following experiments were conducted to evaluate the properties of this resin.

A sheet of about 500μ was obtained from the resin composition by a pressing method, and then a 90-square sheet was collected to obtain a biaxially stretched film under the following conditions.

Stretching machine: Tabletop biaxial stretching machine manufactured by Toyo Seiki Temperature: 110 ° C Preheating time: 3 minutes Stretching ratio: MD 5 times, TD 5 times Stretching speed: 15 m / min Physical properties of the film with a thickness of about 20μ obtained above The results are shown in Table 1. The physical properties of the film are shown by the average value of MD and TD.

This film was excellent in transparency, slippage and blocking resistance, and was also excellent in low temperature shrinkability.

Example 2 Propylene-α-olefin copolymer (butene-1 content 16.9 mol%, CXS 20.5 wt%, Vicat softening point 100 ° C., MI
A resin composition was obtained in the same manner as in Example 1 except that 0.4 part of the same aluminosilicate powder used in Example 1 was added to 5.5 g / 10 minutes). Next, a biaxially stretched film was obtained under the same conditions except that the stretching temperature was 90 ° C. under the conditions of Example 1. The physical properties of the film are shown in Table 1. This film was excellent in transparency, slippage and blocking resistance, and also excellent in low temperature shrinkability.

Example 3 The same propylene-α-olefin copolymer as in Example 2 was added to A-type zeolite powder (average particle size 0.8 μ, oil absorption 60 ml /
A resin composition was obtained in the same manner as in Example 1 except that 0.3 part of 100 g) was added. Next, a biaxially stretched film was obtained under the same conditions as in Example 1 except that the stretching temperature was 100 ° C. The physical properties of the film are shown in Table 1. This film was as good as the film of Example 2.

Example 4 70% by weight of the same propylene-α-olefin copolymer as used in Example 2 and an ethylene random copolymer (ethylene content 4.8 wt%, CXS 4.1 wt%, MI 8.4 g / 10 min). Propylene copolymer consisting of 30% by weight (Vicat softening point 103
A resin composition was obtained in the same manner as in Example 1 except that 0.4 part of the same aluminosilicate powder as used in Example 1 was added to (° C.). Next, a biaxially stretched film was obtained under the same conditions except that the stretching temperature was 90 ° C. under the conditions of Example 1. The physical properties of the film are shown in Table 1. This film was as good as the film of Example 2.

Example 5 Propylene-α-olefin copolymer (butene-1 content 22.3 mol%, CXS 27.8 wt%, MI 3.1 g / 10 min) 30 wt%
And ethylene random copolymer (ethylene content 4.8wt
%, CXS 4.1 wt%, MI 8.4 g / 10 min) 70 wt% propylene copolymer (Vicat softening point 110 ° C. 0.4 part addition of the same aluminosilicate powder used in Example 1) Aside from the above, a resin composition was obtained in the same manner as in Example 1. Next, a biaxially stretched film was obtained under the same conditions as in Example 1, except that the stretching temperature was 100 ° C. The results are shown in Table 1. This film was as excellent as the film of Example 2.

Example 6 Propylene α-olefin copolymer (butene-1 content
11.7 mol%, ethylene content 1.6 mol%, CXS21.0 wt%,
A resin composition was obtained in the same manner as in Example 1 except that 0.4 part of the same aluminosilicate powder used in Example 1 was added to the Vicat softening point of 101 ° C., MI 2.5 g / 10 minutes). . Next, except that the stretching temperature was 90 ° C. under the conditions of Example 1,
A biaxially stretched film was obtained under the same conditions. The physical properties of the film are shown in Table 1. This film was as good as the film of Example 2.

Comparative Example 1 The same propylene-α-olefin copolymer as that used in Example 2 was supplemented with Mizusawa Chemical Co., Ltd. Shilton AMT (amorphous aluminosilicate average particle size 1.9 μ, oil absorption 64 ml / 100 g).
A resin composition was obtained in the same manner as in Example 1 except that 2 parts were added. Next, a biaxially stretched film was obtained under the same conditions except that the stretching temperature was 90 ° C. under the conditions of Example 1. The physical properties of the film are shown in Table 1. This film is transparent,
The slip resistance and blocking resistance were poor.

Comparative Example 2 The same propylene-α-olefin copolymer as that used in Example 2 was added with 0.2 part of Mizusukasil p-527 (silica powder average particle size: 1.5 μm) manufactured by Mizusawa Chemical Co., Ltd. A resin composition was obtained in the same manner as in 1. Next, Example 1
A biaxially stretched film was obtained under the same conditions except that the stretching temperature was 90 ° C. under the above conditions. The physical properties of the film are shown in Table 1.
The film had somewhat poor transparency and poor sliding and blocking resistance.

Comparative Example 3 Same as Example 1 except that 0.2 part of the same aluminosilicate powder used in Example 1 was added to the same propylene-α-olefin copolymer used in Example 2. To obtain a resin composition. Next, a biaxially stretched film was obtained under the same conditions except that the stretching temperature was 90 ° C. under the conditions of Example 1. The physical properties of the film are shown in Table 1. This film was excellent in transparency but poor in slip resistance and blocking resistance.

Comparative Example 4 Aside from the same propylene-α-olefin copolymer used in Example 2, 0.2 parts of Fuji DeVison Syroid-150 (silica powder average particle size 2.5 μm) was added,
A resin composition was obtained in the same manner as in Example 1. Next, a biaxially stretched film was obtained under the same conditions except that the stretching temperature was 90 ° C. under the conditions of Example 1. The physical properties of the film are shown in Table 1. This film had the same bad characteristics as in Comparative Example 1.

Comparative Example 5 The same propylene-α-olefin copolymer used in Example 2 was added to A-type zeolite powder (average particle size 2.2 μ,
A resin composition was obtained in the same manner as in Example 1 except that 0.2 part of oil absorption 50 ml / 100 g) was added. Next, a biaxially stretched film was obtained under the same conditions except that the stretching temperature was 90 ° C. under the conditions of Example 1. The physical properties of the film are shown in Table 1. This film had the same bad characteristics as in Comparative Example 1.

Comparative Example 6 Propylene-random copolymer (ethylene content 2.1 wt
%, CXS3.1wt%, Vicat softening point 139 ° C, MI8.6g / 10 minutes)
A resin composition was obtained in the same manner as in Example 1 except that 0.2 part of the same aluminosilicate powder as used in Comparative Example 1 was added. Next, under the conditions of Example 1, the stretching temperature was set to 15
A biaxially stretched film was obtained under the same conditions except that the temperature was 0 ° C. The physical properties of the film are shown in Table 1. This film is
The transparency and blocking resistance were good, and the slippage was somewhat bad, but there was no low-temperature shrinkage at all, which was beyond the scope of the present invention.

<Effects of the Invention> As described in detail above, the resin composition of the present invention produces a shrink-wrapping film having, for example, good low-temperature shrinkability and excellent transparency, slipperiness, and blocking resistance. It is a very good one.

Continuation of front page (56) References JP-A-60-118727 (JP, A) JP-A-56-4642 (JP, A) JP-A-61-9448 (JP, A)

Claims (1)

[Claims] 1. A resin composition for a shrinkable film, comprising 0.25 to 2.0 parts by weight of an aluminosilicate powder having an average particle size of 1 μm or less added to a propylene copolymer having a Vicat softening point of 130 ° C. or less.