JPH02265928A - Uniaxially oriented polypropylene band - Google Patents

Abstract

PURPOSE:To obtain the title band excellent in transparency and strengths by extruding a specified crystalline PP resin composition and uniaxially orienting the extrudate. CONSTITUTION:A crystalline PP resin composition of a melt flow rate of 0.5-5g/10min, obtained by mixing 100 pts.wt. propylene polymer (e.g. crystalline PP) with 5-20 pts.wt. aliphatic or alicyclic petroleum resin (e.g. Alcon P-125), is extruded, and the extrudate is uniaxtally oriented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a polypropylene uniaxially stretched band with excellent transparency.

[Prior art] Polypropylene (hereinafter sometimes referred to as PP) bands have traditionally had superior physical properties such as strength and chemical resistance, and are also cheaper than bands made of thermoplastic resins such as polyester and nylon. From, for house holding, grain,
It is used in a wide range of applications, from pesticides such as fertilizers to light packaging for mail, parcels, books, securities, etc., and for packaging materials such as pallet building materials, steel plates, and machine necks. .

Regarding the size and shape of the band, the band ranges from 5 to 50 mm in width and 0.2 to 2 mm in thickness, and is used for bundling by hand, automatic packing machine, etc.

However, conventional PP bands have inferior transparency compared to bands made of polyester, nylon, etc., and therefore have the disadvantage that the parts bound and packed with the bands lack transparency. That is, when a plurality of books, securities, newspapers, etc. are packaged together using a PP band, there is a problem that the PP band covers letters, numbers, figures, etc., making them difficult to read. In order to make this determination, the band must be shifted and the package must be looked into. However, shifting the band may loosen the tightening force of the packaging and cause the packaged item to collapse.

Therefore, a highly transparent PP band is required so that characters, numbers, figures, etc. of the package can be seen through the band and read.

As methods for improving the transparency of PP bands, methods such as adding a nucleating agent to the PP resin and quenching at low temperatures during melt extrusion processing have been proposed, but in both cases, the effect of improving the transparency of the band is Especially when a nucleating agent is used, whitening due to voids tends to occur during stretching, and in order to suppress this, the stretching ratio must be lowered, resulting in a decrease in the strength of the band.

In addition, in the case of the method of rapid cooling at low temperatures, the interior of the melt-extruded product, such as a sheet, is cooled slowly compared to the rapid cooling of the surface, so the crystallization between the surface layer and the inner layer becomes uneven, and during the stretching process. There are a number of problems in this process, including the tendency to develop unevenness in stretching, resulting in decreased productivity and strength.

[Problems to be Solved by the Present Invention] As a result of intensive studies to obtain a PP band with excellent transparency, the inventors discovered that transparency can be improved by a composition made by mixing a specific petroleum resin with a PP resin. They discovered this and completed the present invention.

It is an object of the present invention to solve the problems that cannot be obtained with the prior art and to provide a PP uniaxially stretched band with excellent transparency suitable for seeing through the characters, etc. of a package.

c.Means to solve the problem] The present invention has the following configuration +1).

(1) 5 to 20 parts by weight of aliphatic or alicyclic petroleum resin is blended to 100 parts by weight of propylene polymer, and the melt 7o-rate (MFR) is 0.5 to 5 g/l [1 minute This is a polypropylene uniaxially stretched band characterized by being formed by extruding a crystalline polypropylene resin composition and then uniaxially stretching it.

The PP resin composition that can be used in the present invention is composed of a mixture of propylene polymer and petroleum resin, and must have a melt flow rate (MFR) of 5 to 5 g/10 minutes.

The propylene polymer is preferably a crystalline propylene homopolymer obtained by polymerizing propylene using a catalyst consisting of a transition metal compound and an organometallic compound. 4-Methylpentene-1, octene-!
Copolymers obtained by copolymerizing α-olefins such as the following can also be used.

There is no particular limitation on the polymerization method, and the polymerization can be produced using any method such as a gas phase method, a slurry method, a solution method, or a combination thereof. In addition, each f! which is normally used for PP% products as needed! Additives such as heat stabilizers, antioxidants, ultraviolet absorbers, lubricants, etc. may be used to the extent that they do not impair the purpose of the present invention.

Furthermore, the petroleum resin used in the present invention is a hydrogenated hydrocarbon polymer, has an iodine value lower than 50, and has an iodine value of about 70°C.
It has a ring and ball softening point of more than 500 and an average molecular weight (Last method) of about 500 or more.

Such materials include mixed unsaturated monomers derived from deep cracking of petroleum, including known industrially available materials such as those described in British Patent No. 1,024,718, such as aliphatic carbonization. Polymers obtained by catalytic polymerization of hydrogen, vinyl aromatic hydrocarbons, cyclopentadiene, etc. and acyclic, monocyclic and dicyclic compounds containing alloocimene, carene, dipentene, terpinonene, etc. or fractions and various other terpenes. Included are dimers and higher order polymers obtained by polymerizing and/or copolymerizing terpene hydrocarbons, such as cyclic monoterpenes and mixtures thereof, followed by hydrogenation under pressure.

Polymerization of petroleum products, terpenes or terpene mixtures can be carried out by known methods using sulfuric acid, phosphoric acid, amphoteric metal chlorides such as zinc chloride or aluminum chloride, etc. in a solvent or without a solvent. This polymerization is desirably conducted under conditions that result in all hydrocarbon monomers reacting with minimal dimer formation.

Hydrogenation of this hydrocarbon polymer can be carried out using a catalyst such as nickel, cobalt or zirconia. This hydrogenation is carried out in the presence of a solvent such as methylcyclohexane, toluene, p-methane, hydrogenated terbennimonomer-trimer, etc. for 50-10. Co.

Preferably, it is carried out using a pressure in the range of 1.0 pis and a temperature in the range of 150 to 300°C.

Prepared by known methods, average molecular weight of about 500 (last method) and above, iodine number of about 50 or less, about 70
Any hydrogenated hydrocarbon polymer having a ring and ball softening point above 0.degree. C. and compatibility with polypropylene can be used.

For example, the molecular weight SOO~5,000 and the softening point 50~ shown in JP-A No. 51-91,955! Examples include aliphatic or alicyclic petroleum resins at 50°C.

The blending ratio of the petroleum resin in the present invention is required to be 5 to 20 parts by weight per 100 parts by weight of the propylene polymer. If the petroleum resin is less than 5 parts by weight, the effect of improving transparency is slight. When the number exceeds 20 ridges, the strength of the band decreases so much that it is difficult to maintain a strength of 3 g/d or more, and the improvement in transparency by increasing the amount reaches its limit, which is not preferable.

Therefore, the blending amount is particularly preferably 10 to 151 parts in order to maintain the strength of the band and improve transparency.

The crystalline PPPA resin composition composed of a propylene polymer and a petroleum resin used in the present invention is produced by melt extrusion molding and has a melt flow rate (Jrs K 721.0) from the viewpoint of being used as a raw material for manufacturing bands for binding, packaging, etc. -1978
Test conditions: 230°C, 2.1.6 kg, hereinafter referred to as VFR. )0.5-5g710min.

MFR is an index for drawing out the band strength.
If the FR is lower than o, sH/io, the melt viscosity during melt extrusion is high, which tends to cause extrusion fluctuations called surging and streamline breakage of the resin called melt fracture at the die exit, and the unstretched product obtained by extrusion molding This is not preferable because the roughness of the surface of the sheet reduces transparency.

In addition, if the MFR exceeds 5 g/710 minutes, it is not possible to maintain the same strength as when using a band of 38 to 5 g/10 minutes.In order to improve transparency and maintain strength, the VFR is 0.8 to 3 g. /Io is more preferable. Also, as a method for blending the propylene polymer and petroleum resin, a commonly used mixer such as a drum blender,
■Blender, Henschel mixer, Banbury mixer 1 and other mixing machines can be used. Furthermore, after this mixing, the crystalline PP resin composition used in the present invention is obtained by pelletizing by known techniques such as various extruders such as an axle-shaft extruder and a twin-screw extruder.

Next, the band manufacturing method of the present invention will be explained. The band of the present invention is produced using the crystalline PP resin composition obtained by the above-described method as a raw material, but the method of production is not particularly limited, and can be carried out using any known or commonly used apparatus and method for band production.

For example, using an extruder with a T-die, the raw material is
After melt-kneading at a temperature of 00° C., extrusion is performed through a wide die or slit die, and the extruded wide sheet or strip is cooled and solidified using a cooling water tank or a cooling roll. After this, the strip is left as it is, and the sheet is slit to a predetermined width and then heated with a hot air heating furnace, hot water tank, heating roll, hot plate, far infrared heating furnace, etc. at different rotation speeds. Between two or more sets of nip rolls,
Multi-stage stretching of one stage or two or more stages can be performed in the length direction.

The degree of stretching governs the degree of molecular orientation of the band and determines the strength of the band product.

The stretching conditions may be the usual stretching temperature and stretching ratio for stretching crystalline PP resin. Specifically, the stretching temperature is 100 to 200°C as the temperature of the heating medium, and the stretching ratio is 2.
The stretching temperature is preferably 1.20 to 12 times, but preferably 1.20 to 12 times.
175° C., and the stretching ratio is in the range of 4 to 10 times.

Furthermore, since the PP band obtained by the stretching has a small elongation and is easily shrunk, it is preferable to perform heat treatment (annealing) using a known device and method at a relaxation rate of 20% or less in order to prevent deterioration of physical properties over time.

EXAMPLES AND COMPARATIVE EXAMPLES The present invention will be specifically explained below using Examples and Comparative Examples, but the present invention is not limited to the following Examples unless the gist thereof is exceeded.

The measurement methods used in the Examples and Comparative Examples are as follows.

(1) MFR: Based on JIS K 5758 (2) Tensile test; Testing machine Toyo Seiki Tensilon Type I between gauge lines 200+am/min Tensile speed 200mm/+m1n (3) Total haze: Based on ASTM-D-1003 Total haze was used as an indicator of transparency. The smaller the transparency value, the more transparent it is.

(4) Measurement environment: Temperature: 23±1℃ Humidity: 50±3% Examples 1 to 3 VFR-2g/l (1 minute crystalline polypropylene mixed with petroleum resin (trade name: Alcon P125, manufactured by Munyo Kagaku ■) for 5~
After mixing for 3 minutes at room temperature using a Henschel mixer (trade name) of 15 parts by weight, the mixture was pelletized using a 40 φ extruder with a set temperature of 230°C to obtain a composition.

The composition was extruded into a sheet with a cooling roll temperature of 30°C using a 65φ extruder equipped with a T-die at a set temperature of 250°C to form a sheet with a thickness of 2IIm. A uniaxially stretched band having a thickness of 0.5 cm was formed in the longitudinal direction using a roll stretching machine at a stretching ratio of 9 times.

A band with excellent transparency was obtained.

Example 4 A uniaxially stretched band was obtained in the same manner as in Examples 1 to 3, except that 15 parts by weight of petroleum resin (trade name Alcon P125, manufactured by Arayo Kagaku ■) was blended with crystalline polypropylene having a VFR of 1 g and 710 minutes.

A band with excellent transparency and strength was obtained.

Comparative Example I A uniaxially stretched band of crystalline polypropylene having a weight ratio of 3 g/10 minutes was obtained under the same molding conditions as in Examples 1 to 3.

Implementation compared to each side! J The brightness was poor and it was over.

Comparative Example 2 A uniaxially stretched band of crystalline polypropylene with MFR=1 g/10 minutes was obtained under the same molding conditions as in Examples 1 to 3.

Transparency was poor compared to Examples.

Comparative Example 3 V F R-2g 710 minutes of crystalline polypropylene and petroleum resin (manufactured by Arayo Kagaku ■, trade name Alcon P125)
Uniaxially stretched bands were obtained under the same molding conditions as in Examples 1 to 3, except that 3 parts by weight was added.

Although the transparency improves in the comparative examples, the degree of improvement is small.

Comparative Example 4 A uniaxially stretched band was obtained under the same molding conditions as Examples 1 to 3, except that 30 parts by weight of petroleum resin (trade name Alcon PL25, manufactured by Arayo Kagaku ■) was blended with crystalline polypropylene of MFR = 2 g/10 min. Ta.

Although the transparency is excellent, the strength is greatly reduced and it is unsuitable as a stretched product.

Comparative Examples 5 to 6 MFR-2 g/10 minutes of crystalline polypropylene was added with 0 nucleating agent methylene bis(2,4-di-t-butylphenol) acid phosphate (manufactured by Adeka Argus Hatake, trade name MARK-NA11.IJF). Uniaxially stretched bands were obtained under the same molding conditions as in Examples 1 to 3, except that .2 to 11.4 double plate portions were added.

This band became white due to stretching, and transparency could not be obtained.

Examples 1 to 4 of the present invention and Comparative Examples 1 to 6 are shown in Table-1.

P with excellent transparency and strength according to Examples 1 to 4 of the present invention
It can be seen that a P uniaxially stretched band is obtained.

[Operations and Effects of the Present Invention] The PP band of the present invention has significantly superior transparency compared to conventional PP bands, so that it can be easily used after packing paper, books, slips, mail, printed matter, etc. Characters, numbers, figures, etc. on the packaged items can be clearly read, and there is no need to take the trouble to shift the band, preventing the packaged items from collapsing, leading to improved transportation efficiency.

Claims (1)

[Claims] (1) Crystalline polypropylene resin containing 5 to 20 parts by weight of aliphatic or alicyclic petroleum resin to 100 parts by weight of propylene polymer and having a melt flow rate (MFR) of 0.5 to 5 g/10 min. A polypropylene uniaxially stretched band, characterized in that it is made by extruding a composition and then uniaxially stretching it.