JPS608346A - Manufacture of polyethylene molded article having excellent transparency - Google Patents

Abstract

PURPOSE:To obtain the titled molded article having excellent compatibility with polyethylene and excellent transparency and rigidity, by adding a small amount of a polypropylene wax having a specific physical property to a specific low-density linear polyethylene, and molding the composition at a temperature within a specific range. CONSTITUTION:The objective molded article is obtained by compounding (A) a low-density linear polyethylene having a density of 0.90-0.94g/cm<3> by density gradient tube, a melt flow rate of 0.1-90g/10min under the load of 2.16kg at 190 deg.C, exhibiting one or more melting points by differential scanning calorimeter wherein the highest melting point is 100-130 deg.C with (B) 0.05-0.9wt% polypropylene wax having an intrinsic viscosity of 0.05-1dl/g measured in decaline at 135 deg.C, a melting point of >=145 deg.C measured by a differential scanning calorimeter, and an isotacticity of >=95 measured by nuclear magnetic resonance adsorption, and molding the composition at <=160 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a linear low-density polyethylene molded product with excellent transparency.

Linear low-density polyethylene has superior mechanical strength such as tensile strength, tear strength, and impact strength compared to high-pressure low-density polyethylene, and has a high softening temperature and excellent heat resistance.
It has good cold resistance, high rigidity, strong elasticity, and excellent stress cracking resistance and heat sealability.
It is used for various daily necessities and packaging materials. However, in terms of transparency, high pressure method low density d? Because it is inferior to polyethylene, it is not suitable for applications where aesthetics and decoration are desired.
'He is wearing a cap on his back.

In general, ink can be produced without improving the transparency of polyethylene by changing the processing conditions of polyethylene, such as stretching at a high magnification, rapidly cooling the molten resin, or combining stretching and rapid cooling. is proposed. However, high-magnification stretching limits the shape and precision of the molded product obtained.

In the rapid cooling method, the mold, cooling roll, etc. must be cooled to below room temperature, which causes problems such as dew condensation and complicated equipment. Furthermore, the crystallinity of the molded product decreases, resulting in loss of mechanical strength and rigidity.

In a method that combines stretching and quenching, the orientation effect is small when stretched in a molten state, and there are problems during quenching as described above.

Attempts have also been made to improve transparency by adding a nucleating agent to polyethylene to promote crystallization during crystal solidification of molten polyethylene and to reduce the crystal form. However, many of the conventionally known nucleating agents have a strong effect of promoting crystallization, and as a result, although molded products with excellent mechanical strength and rigidity can be obtained, optical properties such as transparency and gloss are poor. I couldn't get anything good. Moreover, many nucleating agents have problems with compatibility with polyethylene.
If too much is added, bleed-out will occur. Furthermore, many of the materials emit a foul odor when exposed to high heat during molding, which creates a poor environment during molding and is not good for the health of workers.

Therefore, the present inventors conducted extensive research to find a nucleating agent that improves the transparency of linear low-density polyethylene without impairing its excellent properties, has excellent compatibility, and does not cause bleed-out. As a result, it has been found that the above object can be achieved by blending a specific amount of polypropylene wax with specific physical properties and molding in a specific temperature range.

By the way, an attempt was made to improve the physical properties of polyethylene by blending a certain type of polypropylene wax into polyethylene at a ratio of about 1 to 60% by weight, as reported in Japanese Patent Publication No. 37-14.
It is known from the publication No. 625.

According to this publication, polyethylene has an average molecular weight of 100
0 to 8000 (IshiO-506e/g with intrinsic viscosity of 0.05 at +40"C in Tetralin solvent), density of at least 0.90 g/α3, softening point of at least 13
If you mix about 1 to 50% by weight, preferably about 5 to 15% by weight of polypropylene wax, which has a needle strength of 0 at 0°C and a load of 100g for 5 seconds and a load of 250g for 5 seconds and has an acid value of 0, it will become stiff. Rust, tear strength,
It is stated that tensile strength etc. are improved. Although it has been described that this composition has excellent transparency, it has not been clarified whether the transparency is improved by adding the polypropylene wax. Regarding linear low density polyethylene, which is not specifically described in this publication, the present inventors have developed a polypropylene wax having the above-mentioned physical properties. Even if an amount such as J1 to 30% by weight is incorporated, especially an amount such as about 5 to 15% by weight recommended in this publication, transparency is not significantly improved, but rather particles of polypropylene wax in linear low density polyethylene are incorporated. It was found that the transparency did not decrease due to the precipitation of , or bleed-out did not occur, and that the mechanical strength decreased on the contrary. Based on this knowledge, the present inventors conducted further research and found that polypropylene wax having the physical properties shown below was added to linear low-density polyethylene in an amount of 1 weight smaller than that intended in the published technique. By adding very small amounts of less than % and molding under specific temperature conditions, it is possible to improve not only transparency but also mechanical strength such as rigidity without impairing many of the excellent physical properties of linear low-density polyethylene. It turns out.

That is, the present invention provides the following features:
．． 94 within the range of green5, (B) Load 2j
'6k l, the mel i70-rate measured at 190°C is in the range of 0.1 to 90g710m1n, (
C) Linear low-density polyethylene with one or more melting points measured by differential scanning calorimeter and whose highest melting point is in the range of lo[) to +5(]''C (effect) in decalin solvent. Intrinsic viscosity measured at 165°C [
η] is in the range of 0.05 to 1 dl/g, and (11
Melting point (Tm) measured by differential scanning calorimeter is 145°C
(F) 0.05 to 0.9 polypropylene wax having a tacticity (1, I) of 95 or more as measured by nuclear magnetic resonance absorption.
It relates to a method for producing a polyethylene molded product with excellent transparency, which is characterized in that the polyethylene molded product is blended by weight% and melt-molded at a molding temperature of 160°C or less.

Linear low-density polyethylene is made of ethylene produced using a Ziegler type catalyst and α-carbon having 4 to 20 carbon atoms.
A copolymer with olefin, specifically 1-butene, 1-pentene, 1-hexene, 4-methyl-1-
Pentene, 3-methyl-1-pentene, 1-octene,
It is a copolymer with 1-decene, 1-tetradecene, 1-octadecene, etc. This linear low density polyethylene is
The melt flow rate (ASTM D +258K) under a load of 2.16 kQ at 190°C is 0.1
~90g/10m1n, especially 0.5~5
0g/lQmin, and the melting point measured from the endothermic curve of a differential scanning calorimeter (DuPont 9q 0type) at a heating rate of 10°C/min is one or more, often two or six. It is preferable that the highest melting point is in the range of 100 to 130°C, especially 100 to 125°C.The melt flow rate is (L 1g
/10 m1-n, the fluidity properties are poor and the moldability becomes poor.

Also, the melt flow rate is 90 g/IQ mtn
Those exceeding this value have poor impact resistance, tear resistance, etc. Those with a melting point of less than 100°C have poor heat resistance when made into a film, and those with a melting point of more than +30"C have poor low-temperature heat sealing properties. In addition, the density measured using a density gradient tube is
-94g, /Cm' or less, especially in terms of tensile strength and rigidity balance when made into a film or tube
．． 90m and 0.9551g/cm', Saraniha 0.
It is preferably in the range of 91 to 0-93 g/Cm5.

The polypropylene wax, which is one of the components used in the present invention, has an intrinsic viscosity [η] of 0.05 to 1 dj at 155°C in a decalin solvent. /g, especially 0.08 to 0
-8dji'/g, and the melting point (Tm) as measured by a differential scanning calorimetry needle is 145°C or higher, especially 150°C
Thus, the optical activity (I, I) as measured by nuclear magnetic resonance absorption is in the range of 95 or more. Polypropylene wax with an intrinsic viscosity [η] of less than 0.05 d1/g has poor rigidity and transparency improvement effect, and
If the amount exceeds /g, the compatibility with polyethylene will decrease, leading to poor dispersion, which will actually worsen various physical properties. In addition, if the melting point Tm is less than 145°C or the tacticity (c) is less than 95, the crystallinity of the polypropylene wax will be too low, resulting in nucleation that can improve transparency and rigidity. It cannot be shown to be effective as a drug.

Here, the tacticity is the triad tacticity obtained by ff1ffi using the carbon signal of the methyl group by C-NMR. However, the methyl group of propylene adjacent to ethylene was excluded.

Specific examples of the polypropylene wax used in the present invention include propylene homopolymers as well as propylene and other α-olefins, such as ethylene, 1-butene, 1-
Pentene, 1-hexene, 1-heptene, 1-decene,
Copolymers with at least one α-olefin such as 1-octadecene, 6-methyl-1-butene, ro-methyl-1-pentene, 4-methyl-1-pentene, or other copolymerizable comonomers For example, copolymers with styrene, acrylonitrile, vinyl chloride, vinyl acetate, acrylic esters, and methacrylic esters, as well as those obtained by modifying these polymers with unsaturated carboxylic acids or their acid anhydrides, such as acrylic acid, methacrylic acid,
Maleic acid, fumaric acid, citraconic acid, itacone #f
m maleic anhydride, citraconic anhydride, itacone anhydride,
Tetrahydrophthalic acid, methyltetrahydrophthalic acid,
Modified with endocis-bicyclo(2,2,1)hept-5-ene-2,3-dicarboxylic acid, methyl-endocys-bicyclo[2,2,1]hept-5-ene-2,5-dicarboxylic acid, etc. An example of this can be given as an example.

Alternatively, it may be a mixture of the above-mentioned polymers, copolymers, or modified versions of the polymers or copolymers.

In order to produce a polyethylene molded article with excellent transparency according to the method of the present invention, the polypropylene wax is added in an amount of 0.05 to 0.9% by weight, especially 0.05% to 0.9% by weight, based on the silkworm body m of the composition with polyethylene. After blending in an amount of .1 to 0.8% by weight, it is melt-molded at a temperature of 160°C or less. If the amount of polypropylene wax blended is less than the above range, no improvement in transparency or rigidity will be observed, while if it is blended in an amount exceeding the above range, the transparency will on the contrary decrease and mechanical strength will also decrease.

Furthermore, even if the molding is performed at a temperature of +6 o''c or higher, the transparency will not be improved.

Various known methods can be used to add and mix polypropylene wax to polyethylene, such as mixing each resin with a ribbon blender or Henschel mixer and then granulating it with an extruder, or directly using a Panbury mixer kneader. , a method of melt-mixing with two rolls etc. and then granulating with an extruder, or a method of melting and stirring both resins in an autoclave using a solvent, mixing them, then releasing the solvent and granulating with an extruder. Can be mentioned. Among these, dissolving and mixing using a solvent is preferable because even if the amount of polypropylene wax blended is small, the effect of improving optical properties is large. Examples of the solvent used here include hexane, heptane, octane, decane, benbin, toluene, xylene, and the like. The polyethylene composition mixed in this way can be processed using a single screw extruder, a vent extruder, a double screw extruder,
Three screw extruder, conical two screw extruder, conical screw extruder, conical screw extruder, conical screw extruder, planetary screw extruder,
Extrusion molding, vacuum molding, blow molding, pressure molding, injection molding, etc. are performed at a molding temperature of 160°C or less using a gear type extruder, screwless extruder, injection molding machine, etc.

In addition, in the present invention, other known compounding agents such as weathering stabilizer, vinegar Fogging agents, slip agents, lubricants, mold release agents, anti-blocking agents, dyes, pigments, inorganic or organic fillers
It is also possible to add agents and the like.

Examples of the present invention will be shown below to further clarify the content of the invention, but the invention is not limited to these examples in any way.

Examples 1 to 6 and Comparative Example 1-7 Melt Flow Ray) 2.10 g/1010 m1n (A
ST+2? l+8, E), density 0-920 gfim'
Polypropylene wax was blended with linear low-density polyethylene (ASTM D+5O5), and the mixture was melt-mixed using an extruder and pelletized. 1mm from this pellet
A thick sheet was formed and the following tests were conducted. In addition, the intrinsic viscosity [η], melting point, blending amount,
The molding temperature of the sheet is as shown in Table 1.

The results are shown in Table 1.

Claims (1)

[Claims] (~ Density as measured by density gradient tube is 0.90 to 0
．． It is in the range of 94 g/Can', (B) Load 2
．． 16k (j, melt flow rate measured at 190°d is in the range of 0.1 to 90 g/ + Omin, (C) one or more melting points measured by differential scanning calorimeter, and the highest melting point linear low-density polyethylene whose temperature is in the range of 100 to 160°C; ) Melting point (Tm) measured by differential scanning calorimeter is 1
45° C. or higher, and (F) polypropylene wax having a tacticality (1, I) of 95 or higher as determined by nuclear magnetic resonance absorption measurement (0.05%) and 0.0% polypropylene wax.
A method for producing a polyethylene molded product with excellent transparency, characterized by blending 9% by weight and melt molding at a molding temperature of +60"C or less.