JPH01135806A - Straight-chain low-density polyethylene for non-crosslinking expansion molding - Google Patents

Abstract

PURPOSE:To obtain the subject polyethylene, having a specified melt index, density and peak temperature range of fusion curve measured by using a differential scanning calorimeter, excellent expansion moldability and capable of providing moldings with a high expansion ratio and homogeneous cell diameter. CONSTITUTION:A specific polyethylene, having 0.5-4g/10min, preferably 1-3g/10min melt index, 0.900-0.940g/cm<3>, preferably 0.910-0.935g/cm<3> density and >=10 deg.C peak temperature range of fusion curve measured by a differential scanning calorimeter and containing 3-12C alpha-olefin units (e.g., butene-1 or propylene) as alpha-olefine units other than ethylene units. For example, the above- mentioned polyethylene is synthesized by polymerizing ethylene with the alpha- olefines other than ethylene in the presence of a catalyst obtained from an Mg compound, Ti compound and organoaluminum compound at 120-300 deg.C temp. without feeding hydrogen.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to linear low-density polyethylene for non-crosslinked foaming, and more specifically, it has excellent foaming moldability.

The present invention relates to linear low-density polyethylene for non-crosslinked foaming, in which the resulting foamed molded product has a high expansion ratio and a uniform cell diameter.

[Prior Art] Conventionally, in a method of manufacturing a foamed molded product by filling a mold with polyethylene particles and heating, non-crosslinked straight button low density polyethylene has been proposed as a material for the foamed molded product. JP-A-62-15239 describes non-crosslinked linear low-density polyethylene pre-expanded particles. The pre-expanded particles have a melting point of 115-130°C and a density of 0.915-0.940 g/c layer 3. The melt index is 0.1 to 5 g/10 min, the α-olefin unit other than the ethylene unit is an α-olefin unit having 4 to 10 carbon atoms, and the average cell diameter is 120 to 1200.

However, even when molding is performed using the pre-expanded particles, there are problems such as insufficient molding, a molded product with a high expansion ratio, and the inability to stably mold the foam. there were.

An object of the present invention is to overcome the drawbacks of the prior art and provide a linear low-density polyethylene for non-crosslinked foaming that can be stably molded and produce a foamed molded product with a high expansion ratio. shall be.

[Means for Solving the Problems] As a result of intensive research by the present inventors to achieve the above object,
Straight button-shaped low-density polyethylene for non-crosslinking foaming, for which the melt index, density, type of α-olefin units other than ethylene units, and peak width of the melting curve by differential scanning calorimetry have been specified, has excellent foaming moldability and high foaming properties. It was discovered that a foamed molded product having a uniform cell diameter can be obtained depending on the magnification,
The present invention has now been completed.

That is, the configuration of the present invention has a melt index of 0.
5-4g/10min, density 0.900-0.94
0 g/cm3, the α-olefin unit other than the ethylene unit is an α-olefin unit having 3 to 12 carbon atoms, and the peak temperature width of the melting curve measured by a differential scanning calorimeter is 10°C or more. Characteristics of non-crosslinked foamable straight button low density polyethylene (hereinafter referred to as LLDPE)
It is.

The melt index of the LLDPE of the present invention is 0.5 to 4.
g/10 minutes, preferably 1 to 3 g/10 minutes.

If the melt index is less than 0.5 g/10 minutes, it is difficult to obtain a foamed molded product with a high expansion ratio, and if it exceeds 4 g/10 minutes, the uniformity of cell diameter will decrease.

The density of LLDPE of the present invention is 0.900 to 0.940
g/am3. Preferably 0.910-0.935g/
It is cm3.

If this density is less than 0.900 g/cm3, the rigidity of the obtained foamed molded product decreases and becomes 0.940 g/c+
If it exceeds s3, the impact resistance of the foamed molded product decreases.

The LLDPE of the present invention has α-olefin units having 3 to 12 carbon atoms, preferably 4 to 10 carbon atoms, as α-olefin units other than ethylene units.

In the present invention, two or more types of the α-olefin units other than ethylene units may be contained in LLDPE.

Monomers providing this α-olefin unit include, for example, propylene, butene-1,4-methylpentene-
1, hexene-1, hepcene-1, octene-1, nonene-1, decene-1, undecene-1, dodecene-1, etc., preferably butene-1,4-methylpentene-1, octene-1, etc. 1 etc.

The content of the α-olefin units other than ethylene is usually 60 to 99.95%, preferably 70 to 9%.
The weight is 9.5%.

The LLDPE of the present invention has a temperature peak width of 10°C or more in a melting curve measured by a differential scanning calorimeter, preferably 15°C or more.
~50°C.

If the temperature peak width is less than 10° C., foam moldability is unstable, a highly foamed molded product cannot be obtained, and a molded product with uniform cell diameters cannot be obtained.

The temperature peak width is determined as follows.

First, using a PerkinElmer DSCZ model as a measurement base, 10 g of sample was heated at 190°C for 3 minutes, and after melting, lO
The temperature is lowered to 50° C. at a rate of 50° C./min, held at 50° C. for 5 minutes, and then heated at a rate of 10° C./min while recording the melting curve shown in FIG. 1, for example.

Next, taking the melting curve shown in FIG. 1 as an example, the points of 60°C and 130°C of the Mi melting curve are connected as a base line,
Let h be the distance between the intersection point (b) of the base line and the perpendicular line drawn from the highest part of the peak of the melting curve to the line No^, and the apex (a).

Next, a straight line parallel to the base line is drawn on a perpendicular line 0.7 h from the apex, and among the intersections with the melting curve, the low temperature side is C1, and the high temperature side is d. The melting temperatures of C1d are Ti and T, respectively.
b, the temperature peak width (Fosc) can be determined by the following formula: % formula %.

LLDPE having the aforementioned characteristics can be manufactured as follows.

That is, the LLDPE of the present invention is capable of producing α-olefins other than ethylene ethylene in the presence of a catalyst obtained from a magnesium compound, a titanium compound, and an organoaluminum compound at a temperature of 120 to 300°C without supplying hydrogen. It can be obtained by polymerizing.

As the magnesium compound, the following formula % formula % (wherein, R1 is an alkyl group having 1 to 18 carbon atoms,
It represents an alkoxyl group, a cycloalkyl group, an alkylaryl group, an aryl group, an aryloxy group, an aralkyl group, or an arylalkoxyl group, X represents a halogen atom, and n represents a real number satisfying 0≦n≦2. ) can be mentioned.

Among the various magnesium compounds represented by the above general formula, anhydrous magnesium chloride, ethyl-n-butylmagnesium and the like are preferred, and ethyl-n-butylmagnesium and the like are particularly preferred.

Note that these various magnesium compounds may be used singly or in combination by mixing or compounding two or more types.

There are various compounds as the organoaluminum compound, but usually a compound having at least one aluminum-carbon bond in the molecule can be used, for example, the following formula: R33-pA I X p .

R33-tAl (OR4)Xt.

R33AJ12X3 (wherein, R3 and R4 represent an alkyl group or an aryl group having 1 to 20 carbon atoms, X is the same as above, P represents 0.1 or 2, and t represents 0 or 1. , ) can be mentioned.

Among these, organic aluminum represented by R33AJ12X3 is preferred, and ethylaluminum sesquichloride is particularly preferred.

The titanium compound may be of the following formula % formula % (wherein R2 represents carbon!l[1-10, preferably 1-6, alkyl group, cycloalkyl group, aryl group or aralkyl group, and X is It is the same halogen atom as above, and m is usually an integer of 0.1 to 4, but is not necessarily an integer and is a real number that satisfies O≦m≦4 as an average value of a mixture of various titanium compounds. ) can be used.

Among these, tetraalkoxy titanium represented by the general formula Ti(OH2)n is preferable, particularly tetra-n
-butoxytitanium is preferred.

These various titanium compounds may be used alone or in combination of two or more.

Further, the polymerization catalyst can be obtained by preparing the magnesium compound, the aluminum compound, and the titanium compound.

There are no particular restrictions on the method for preparing the catalyst; for example, the magnesium compound, the organic aluminum compound, and the titanium compound may be separately added to a polymerization reaction vessel having a seven-layer container and then mixed.

A preferred method for preparing the catalyst includes, for example, a method in which the magnesium compound and the organoaluminum compound are reacted, and the resulting reaction product is mixed with the titanium compound.

This method will be described in more detail as follows.

That is, the magnesium compound and the organoaluminum compound are added to an inert solvent and heated to a temperature of, for example, O.
The contact reaction is carried out at 240° C., for example, for up to 1 hour, with stirring.

The inert solvent used at this time is as follows.

Examples include alicyclic hydrocarbons having 5 to 16 carbon atoms, alicyclic hydrocarbons, aromatic hydrocarbons, and the like.

Further, the ratio of the magnesium compound and the organoaluminum compound added here is not particularly limited, and may be set appropriately within the range of the ratio of each metal component in the catalyst described below.

There is no particular restriction on mixing the reaction product of the magnesium compound and the organoaluminum compound with the titanium compound.

However, when mixing, the proportion of each metal component in the catalyst is
Magnesium/titanium (atomic ratio) = 0.1-200. In particular, it is preferably within the range of 0.5 to 30, and aluminum/titanium (atomic ratio) is preferably within the range of 1 to 200, particularly 2 to 100.

In addition, during the polymerization, the catalyst is further added with a known activator,
For example, it is possible to coexist with a halide of an element belonging to Group I of the periodic table and use it as a polymerization catalyst system, and by doing so, it is possible to further increase the activity.

Examples of the activator include carbon, silicon, germanium, tin, and lead halide.

There are no particular restrictions on the procedure for blending the activator and polymerization catalyst prior to polymerization, and examples include (1) separately mixing the magnesium compound, the organoaluminum compound, the titanium compound, and the activator in a polymerization reaction vessel; (2) When preparing the catalyst, the entire amount of the activator may be mixed with any of the magnesium compound, organoaluminium compound, and titanium compound, and then other components of the catalyst may be mixed therein; or (3) When preparing the catalyst, a part of the activator is mixed with any of the magnesium compound, organoaluminum compound, and titanium compound, and then when other components of the catalyst are mixed and prepared, the magnesium compound, the organic The remainder of the activator may be added to either the aluminum compound or the titanium compound.

The proportion of oil-temperature catalyst supplied to the polymerization reactor should be appropriately set in consideration of the type and composition of the catalyst used, the type of monomer, the physical properties of the desired polymer, and various other factors such as those mentioned above. It is suitable that the catalyst concentration in the reaction system is about 0.001 to 10 mmol/view, preferably about 0.001 to 1.0 mmol/view as a titanium concentration.

Further, the conversion amount of the activator is usually Ova≦5.0, preferably 0, when the molar ratio of activator/A is a.
．． It may be set within the range of 01≦a≦1.0.

The ratio of the ethylene (A) and the α-olefin other than ethylene (B) may be selected from various values depending on the type and characteristics of the desired ethylene copolymer. , the total of (A) and (B) used is 1
00 mol%, (A) is usually 60 to 99.9
By setting (A) in a range of 5 mol%, preferably in the range of 70 to 99.5 mol%, the LLD of the present invention
It is possible to suitably produce PE.

The reaction temperature for carrying out the polymerization reaction is usually 120 to 300°C, but within this temperature range, a temperature range in which the produced polymer dissolves, for example, a temperature range of about 150 to 250°C is preferable.

The reaction pressure is normally set at 10 to 150 kg/cm2G, preferably 20 to 90 kg/cm2G.

The method for obtaining a foam molded product using the LLDPE of the present invention is as follows:
There is no particular limit, but the melting point of low density polyethylene is 25
Perform pre-foaming within the range of ~+10°C to achieve an average particle size of 2.
After obtaining pre-expanded particles of ~6 mm, preferably 3~5 μm, the particles are heated for 12~7 μm immediately or at room temperature and under normal pressure.
After curing for 2 hours, put it in a mold and heat it to a temperature of 105 to 1.
A foamed molded product can be produced by steam heating under the conditions of 30° C. and a steam pressure of 0.5 to 4 kg/cm2G.

Pre-foaming involves dispersing LLDPE particles and a volatile foaming agent in water in the presence of a dispersant in a pressure-resistant container, and heating the resin particles to a temperature close to the melting point of the particles to form volatile foam within each particle. After impregnating the container with the agent, the contents of the container are released into an atmosphere with a lower pressure than the inside of the container while maintaining the temperature and pressure inside the pressure container at a constant level with the vapor produced by the volatile foaming agent. Let's do it.

Examples of the volatile blowing agent include aliphatic hydrocarbons such as propane, butane, pentane, hexane, and heptane having a boiling point of 150 to 120°C, trichlorofluoromethane, dichlorodifluoromethane, dichlorotetrafluoromethane,
Examples include halogenated hydrocarbons such as trichlorotrifluoromethane, and dichlorodifluoromethane is particularly preferred.

One or more of these can be used.

The amount of the volatile foaming agent used is 10 to 60 parts by weight, preferably 20 to 50 parts by weight, based on M parts of non-crosslinked linear low density polyethylene 1001.

Examples of the dispersant include calcium phosphate, zinc carbonate, titanium oxide, and aluminum oxide, with aluminum oxide being particularly preferred.

The foamed molded product obtained as described above is usually highly foamed with a foaming ratio of 35 to 50 times, and has uniform cell diameters with an average cell diameter of 100 to 700 cells.

Further, when performing the foam molding process using the LLDPE according to the present invention, the LLDPE may be used alone, or the LLDPE and another resin may be blended to perform the foam molding process. You may do so.

Examples of the other resins include low density polyethylene, high density polyethylene, polypropylene, ethylene-vinyl acetate copolymer, polyvinyl chloride, and the like.

When performing foam molding using the blend, the blending ratio of the other resins can be determined as appropriate as long as it does not impede the purpose of the present invention.
Compared to DPH, MI is always 5-50 heavy! , 1%,
Preferably it is 10 to 30 double star%.

[Example] (Example 1) In a continuous polymerization reaction vessel, dehydrated n-hexane and ethylaluminum sesquichloride were fed with ethyl-n-butylmagnesium and tetrabutoxytitanium, and at the same time, ethylene and 1- Butene was continuously supplied, reaction temperature was 185℃, reaction pressure was 0kg/cm2 (0 under the conditions of i), and reaction temperature was 185℃.
．． The polymerization reaction was carried out for 11 hours to obtain 750 g of ethylene-1-butene copolymer.

The obtained ethylene-1-butene copolymer has a melt index of 1.1 g/10 min and a density of 0.920 g/10 min.
cm', the melting point was 117°C, and the temperature peak width (Fosc) of the melting curve measured by a differential scanning calorimeter was 35°C.

100 parts by weight of this ethylene-1-butene, 45 parts by weight of dichlorodifluoromethane, finely divided aluminum oxide N
'll, put 300 parts of water into an autoclave, set the temperature inside the autoclave to 112℃, and set the pressure to 30kg/c layer 2.
G, and while maintaining the internal pressure at 30 kg/c fat 2 G by adding dichlorodifluoromethane, one end of the autoclave was opened and the contents were discharged into the atmosphere to obtain pre-expanded particles.

After curing the obtained pre-expanded particles at room temperature and normal pressure for 48 hours, they were filled into a mold and heated at 112°C with a 1 kg/c layer of 2G of water to fuse the particles together. After that, a foamed molded product was obtained by cooling and taking out from the mold.

The obtained foamed molded product had good moldability, had a foaming ratio of 42 times, and was uniform with an average cell diameter of 430 p.

The results obtained are shown in Table 1.

(Examples 2 to 9) and (Comparative Examples 1 to 4) Foamed molded products were obtained by carrying out the same operations as in Example 1 by changing the type of comonomer and changing the various properties of the low density polyethylene.

In addition, in Comparative Examples 1 to 4, as the low density polyethylene,
Stamilex 4018 (Comparative Example 1), Stamilex 3ots (Comparative Example 2), Stamilex 4016 (
Comparative Example 3) and Stamilex 4046 (Comparative Example 4) (both manufactured by DSM, trade names) were used.

The obtained results are also shown in Table 1.

(The following is a blank space) [Effects of the Invention] As explained above, the LLDPE of the present invention exhibits stable moldability during foam molding, can obtain a highly foamed molded product with a foaming ratio of 35 to 50 times, and is uniform. This method has advantages such as being able to obtain a foamed molded product having a large cell diameter.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing a method for determining the temperature peak width of a melting curve using a differential scanning octameter according to the present invention. Patent applicant: Idemitsu Petrochemical Co., Ltd. Agent: Naoki Fukumura, patent attorney

Claims (1)

[Claims] (1) The melt index is 0.5 to 4 g/10 min, the density is 0.900 to 0.940 g/cm^3, and the α-olefin unit other than the ethylene unit has a carbon number of 3 to 12. A linear low-density polyethylene for non-crosslinking and foaming, characterized in that it contains α-olefin units and has a peak temperature width of 10°C or more in a melting curve measured by a differential scanning calorimeter.