JPH11286522A - High-melting and low-density polyethylene resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a high-melting and low-density polyethylene resin retaining good molding processability, high transparency, flexibility and chemical resistance essential to a polyethylene resin produced by a high-pressure radical polymerization method and improved in heat resistance. SOLUTION: This resin is produced by a high-pressure radical polymerization method and has a density ρ (g/cm<3> ) within the range of 0.910<=ρ<=0.930, a melt index MI (g/10 min) within the range of 0.01<=MI<=300, the number of short- chain branches Sb (number of methyl groups/1,000 carbon atoms) within the range of 5<=Sb<=60 and a melting point Tm ( deg.C) within the range of 118.5-0.370×Sb<=Tm<=118.5-0.170×Sb. The composition contains the resin. The molded product (a power cable insulating layer or a coaxial cable expanded layer, or the like.) is obtained from the resin or the composition. The method for producing the resin comprises polymerizing ethylene under a high reactional pressure (100-400 MPa) at a low polymerization peak temperature (180-320 deg.C).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a high melting point low density polyethylene resin. More specifically, the present invention relates to a polyethylene resin that exhibits a higher melting point at the same density as compared to a conventional high pressure polyethylene resin. The high-melting low-density polyethylene resin of the present invention can be used for various molded products such as a power cable insulating layer, a coaxial cable foam layer, a packaging film, a hot water transport pipe, a back-in-box, a laminate layer, and a bottle that require heat resistance. Used for manufacturing.

[0002]

2. Description of the Related Art Conventionally, polyethylene resins produced by a high-pressure radical polymerization method have good moldability and processability.
It is used in various industrial fields because of its excellent transparency, flexibility, chemical resistance, etc., but due to the polymerization method called high-pressure radical polymerization, a long-chain branch branched from the polyethylene main chain. Are generated, so that there is a problem that the crystallinity is lowered and the density and the melting point are lowered.

In recent years, the density range of low-density polyethylene (hereinafter, also referred to as HP-LDPE) produced by a high-pressure radical polymerization method is 0.910 to 0.9.
An ethylene-α-olefin copolymer having a density equivalent to 30 g / cm ³ has been produced. This is called linear low-density polyethylene (LLDPE), which is excellent in mechanical strength and heat resistance and low in production cost.
LDPE applications have been partially replaced. But H
P-LDPE applications where excellent processing properties, electrical properties, transparency, flexibility, foamability, etc. are required, such as power cable insulation layers, coaxial cable foam layers, photographic paper support layers,
HP-LDPE is still used in highly transparent films, highly transparent squeeze bottles, food packaging films, and the like. If the heat resistance can be improved while maintaining the excellent moldability of HP-LDPE,
Its use can be expanded.

[0004]

As described above, LL
Despite the appearance of DPE, there are still application fields where product properties cannot be satisfied without HP-LDPE, and it is desired to further improve physical properties such as heat resistance of HP-LDPE. ing. The present invention has been made in view of such a situation,
HP-LDPE maintaining the excellent physical properties of conventional HP-LDPE, and having improved physical properties such as heat resistance, a method for producing the same, provision of a composition containing the resin, and further produced from the resin or the composition. The object of the present invention is to provide a molded product and a method for producing the same.

[0005]

Means for Solving the Problems In the electric cable insulation layer, the dielectric strength at a higher voltage and a higher temperature than before has been improved.
The coaxial cable foam layer has high mechanical properties and heat resistance at a high degree of foaming, the highly transparent film has high tear strength, puncture resistance and heat resistance, and the highly transparent squeeze bottle has high heat resistance and self-sustainability. The heat resistance and the rigidity of the film are required for the film for use, however, these required characteristics are the same density HP
The present inventors have conceived that LDPE can be satisfied by using a material having a high melting point.
In order to develop a novel HP-LDPE having a higher melting point by a high-pressure radical polymerization method, the present inventors have developed production conditions such as pressure, polymerization reaction peak temperature, type and concentration of a chain transfer agent, and radical generation catalyst. The present invention has been completed by intensive studies on combinations of the types, concentrations, and the like.

That is, the present invention is produced by a high pressure radical polymerization method and has a density ρ (g / cm ³ ) of 0.910 ≦
ρ ≦ 0.930, melt index MI (g / 10
Is 0.01 ≦ MI ≦ 300, and the number of short-chain branches Sb represented by the number of methyl groups per 1000 carbon atoms is 5 ≦ Sb.
≦ 60, melting point Tm (° C.) 118.5-0.370 × S
The present invention relates to a high melting point low density polyethylene resin, wherein b ≦ Tm ≦ 118.5−0.170 × Sb. The present invention also relates to a resin composition comprising the high melting point low density polyethylene resin of the present invention. Further, the present invention relates to a molded article produced from the high melting point low density polyethylene resin or the resin composition of the present invention and a method for producing the same. Further, the present invention provides a method for producing ethylene in the presence of a radical generating catalyst and a chain transfer agent.
Polymerization reaction peak temperature of ~ 320 ° C, 100 ~ 400MP
The present invention relates to a method for producing the high melting point low density polyethylene resin of the present invention, which comprises polymerizing at a polymerization pressure of a.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The high melting point low density polyethylene resin of the present invention has a density ρ of 0.910 to 0.930 g / c.
m ³ , melt index MI is 0.01 to 300 g /
The number of short-chain branches Sb is 5 to 60 for 10 minutes. MI is 0.
If it is less than 01 g / 10 minutes, the processability is reduced, and 300 g
When the time exceeds / 10 minutes, physical properties such as impact resistance and elongation are undesirably reduced. If Sb is less than 5, the workability decreases, and if Sb exceeds 60, the modulus of elasticity decreases with the decrease in crystallinity, which is not preferable. Moreover, the melting point Tm of the polyethylene resin of the present invention is in the range of (118.5-0.370 × Sb) or more and (118.5-0.170 × Sb) or less, and compared with the conventional HP-LDPE. It has a higher melting point at the same density.

The high-melting low-density polyethylene resin of the present invention is polymerized by a method called high-pressure radical polymerization in a polymerization reaction vessel under high pressure and high temperature conditions in the presence of a radical generating catalyst and a chain transfer agent. Can be manufactured. The polymerization reaction peak temperature of the monomer ethylene is 1
80-320 ° C., particularly preferably 200-300 ° C.
It is in the range of ° C. The polymerization reaction pressure is in the range of 100 to 400 MPa, particularly preferably 150 to 300 MPa, as measured at the temperature at the inlet of the reaction vessel.

The radical generating catalyst used in the production of the polyethylene resin of the present invention includes conventional catalysts such as organic peroxides, azo compounds and oxygen. Organic peroxides include di-tert-butyl peroxide,
Tertiary butyl benzoate, dodecanol peroxide, lauryl peroxide, diacetyl peroxide, dipropyl peroxide, tertiary butyl peroxyacetate, tertiary butyl peroxyisobutyrate, dicumyl peroxide, tertiary butyl peroxide Valate, di (tertiary butyl peroxy) adipate, tertiary butyl peroxy laurate and the like can be mentioned. Azo compounds include:
Azobisisobutyronitrile and the like.

Examples of the chain transfer agent include hydrogen, propylene, butene-1, a saturated aliphatic hydrocarbon having 1 to 20 or more carbon atoms, a saturated aliphatic alcohol having 1 to 20 or more carbon atoms, Examples thereof include saturated aliphatic carbonyl compounds having 1 to 20 or more carbon atoms such as methanol, ethanol, propanol and isopropanol, such as carbon dioxide, acetone and methyl ethyl ketone, and aromatic compounds such as toluene, ethylbenzene and xylene.

Although the cause of the increase in the melting point of the high-melting low-density polyethylene resin of the present invention is not clear, the reaction pressure is set higher than usual polymerization conditions and the polymerization peak temperature is set lower during the production. A change in molecular structure, in which the side chain arrangement specific to polyethylene resin changes, leads to a high melting point due to the formation of highly ordered crystals, which is expected to significantly improve heat resistance. .

The high-melting low-density polyethylene resin of the present invention may be used alone or as a mixture thereof, and may contain common additives such as antioxidants, antifogging agents, antistatic agents, crosslinking agents, It may be used together with anti-blocking agents, slip agents, colorants, anti-treeing agents, crystal nucleating agents and the like, or common fillers such as talc, mica, carbon black and the like. The mixing of the resins of the present invention, the mixing of the additives used in the present invention or the mixing of the resin and the additive, pellets, powder, solid state such as granular, or in a liquid state, V-type blender, It is performed by a tumbler type blender, a ribbon blender, a blender with a rotary wing or a fixed wing, a Henschel mixer, or the like, to obtain a so-called dry blend or soak. As another mixing method, Banbury mixer, buscon kneader, mixing roll, intensive mixer, single screw extruder, twin screw extruder, multi-resin, There is a method in which the mixture is charged into a screw extruder, a static mixer, or the like, and is heated and kneaded. The heat-melted kneaded material can be supplied to a molding machine as it is or as pellets or powder to form a molded product. The mixing order of the above components may be arbitrary. May be produced and blended with other components by dry blending or heat-melt kneading. The high-melting-point low-density polyethylene resin of the present invention can be used together with an ordinary high-pressure polyethylene resin. In this case, the amount of the ordinary high-pressure polyethylene resin is preferably small.

The molded articles produced from the high-melting low-density polyethylene resin of the present invention are of various types, for example, a power cable insulating layer, a coaxial cable foam layer, a photographic paper support layer, various packaging films, and a pipe for transporting hot water. , Including back-in-box, laminate layer, bottle, etc., especially for power cable insulation layer, coaxial cable foam layer, highly transparent film, highly transparent squeeze bottle, food packaging film etc. which require high workability and heat resistance. Include.

[0014]

Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

Example 1 Using a tubular reactor, using a normal organic peroxide as a catalyst, in the presence of a chain transfer agent, the polymerization peak temperature was 280.
Ethylene was polymerized at a temperature of 260 ° C. and a polymerization pressure of 260 MPa to obtain a high-pressure polyethylene resin. The resin obtained is M
I = 0.1 g / 10 min, density ρ = 0.921 g / c
m ³ , the number of short-chain branches Sb was 22.9. The actually measured melting point Tm of this resin is 110.8 ° C., which is higher than 110.0 ° C., which is a value calculated from the following equation 1: 118.5−0.370 × Sb (1). , A new resin that has never been reported before.

Example 2 A polymerization peak temperature of 270 was obtained using a conventional organic peroxide as a catalyst in a tubular reactor in the presence of a chain transfer agent.
Ethylene was polymerized under the conditions of ° C and a polymerization pressure of 295 MPa to obtain a high-pressure polyethylene resin. The resin obtained is M
I = 5.2 g / 10 min, density ρ = 0.929 g / c
m ³ and the number of short-chain branches Sb = 11.5. The measured melting point Tm of this resin is 115.4 ° C., which is higher than 114.2 ° C., which is the value calculated from the above formula 1, and is a novel resin that has not been reported before. there were.

Example 3 Using a tubular reactor, using a normal organic peroxide as a catalyst, in the presence of a chain transfer agent, the polymerization peak temperature was 290.
Ethylene was polymerized at a temperature of 230 ° C. and a polymerization pressure of 230 MPa to obtain a high-pressure polyethylene resin. The resin obtained is M
I = 38 g / 10 min, density ρ = 0.914 g / cm ³ ,
The number of short-chain branches Sb was 36.5. The measured melting point Tm of this resin is 107.5 ° C., which is higher than the value calculated from the above formula 1, 105.0 ° C., and is a novel resin which has not been reported so far. there were.

Example 4 Using a tubular reactor and a normal organic peroxide as a catalyst, in the presence of a chain transfer agent, a polymerization peak temperature of 260
Ethylene was polymerized at a temperature of 200 ° C. and a polymerization pressure of 205 MPa to obtain a high-pressure polyethylene resin. The resin obtained is M
I = 65 g / 10 min, density ρ = 0.915 g / cm ³ ,
The number of short-chain branches Sb was 39.3. The actually measured melting point Tm of this resin is 105.5 ° C., which is higher than 104.0 ° C., which is the value calculated from the above formula 1, and is a novel resin which has not been reported before. there were.

Comparative Example 1 Using a tubular reactor, a polymerization peak temperature of 34
Ethylene was polymerized under the conditions of 0 ° C. and a polymerization pressure of 210 MPa to obtain a high-pressure polyethylene resin. The obtained resin had MI = 0.15 g / 10 min and density ρ = 0.919 g / c.
m ³ , the number of short-chain branches Sb was 32.1. The actually measured melting point Tm of this resin was 105.6 ° C., which was lower than the value calculated from the above formula 1, 106.6 ° C., and was a conventionally manufactured resin.

Comparative Example 2 Using a tubular reactor, polymerization peak temperature was 33
Under a condition of 0 ° C. and a polymerization pressure of 230 MPa, ethylene was polymerized to obtain a high-pressure polyethylene resin. The obtained resin had MI = 4.2 g / 10 min and density ρ = 0.927 g / cm.
^{3. The} number of short-chain branches Sb was 18.0. The actually measured melting point Tm of this resin was 110.9 ° C., which was lower than the value calculated from the above formula 1, 111.8 ° C., and was a conventionally manufactured resin.

Comparative Example 3 Using a tubular reactor, polymerization peak temperature was 35
Under a condition of 5 ° C. and a polymerization pressure of 185 MPa, ethylene was polymerized to obtain a high-pressure polyethylene resin. The obtained resin had MI = 42 g / 10 min and density ρ = 0.914 g / c.
m ³ , the number of short-chain branches Sb was 42.3. The actually measured melting point Tm of this resin was 100.5 ° C., which was lower than the value calculated from the above formula 1, 102.8 ° C., and was a conventionally manufactured resin.

Table 1 shows the measurement results of the physical properties of the high-pressure polyethylene obtained in Examples 1-4 and Comparative Examples 1-3.
Are shown together.

[Table 1] MI ¹⁾ ρ ²⁾ Sb ³⁾ Calculated melting point Vicat calculated from Equation 1 ⁴⁾ Tm ⁵⁾ Softening temperature ⁶⁾ Example 1 0.1 0.921 22.9 110.0 110.8 97.1 Example 2 5.2 0.928 11.5 114.2 115.4 104.0 Execution Example 3 38 0.914 36.5 105.0 107.5 75.5 Example 4 65 0.915 39.3 104.0 105.5 71.6 Comparative Example 1 0.15 0.919 32.1 106.6 105.6 84.4 Comparative Example 2 4.2 0.927 18.0 111.8 110.9 98.5 Comparative Example 3 42 0.914 42.3 102.8 100.5 70.0 (footnote) ¹⁾ MI The unit of (melt index) is g / 10 minutes. The measurement conforms to JIS K6760, the test temperature is 190 ° C,
The test was performed under the conditions of a test load of 2160 gf. ²⁾ The unit of ρ (density) is g / cm ³ . Measurement is JIS K6
760. ³⁾ Sb (number of short-chain branches) is unit / 1000C (carbon atom). A sheet having a thickness of 0.2 mm was created, and a Fourier transform infrared spectrophotometer System2000 manufactured by Perkin-Elmer was used.
From the absorbance of 1378 (cm ^-1 ) belonging to the short-chain branch,
It was calculated using a separately prepared calibration curve. ⁴⁾ Melting point calculated from equation 1 (118.5−0.370 × Sb), in units of ° C. ⁵⁾ Measurement of Tm (melting point) is based on JIS K7121.
About 5 mg of the sample was weighed, and the measurement was performed using a TA Instruments type differential scanning calorimeter 2920.
It was expressed as the peak temperature of the melting curve measured in (° C./min).
The unit is ° C. ⁶⁾ The unit of Vicat softening temperature is ° C. Measurement is JIS K72
06.

[0023]

As described in detail above, the high-melting low-density polyethylene resin of the present invention retains the moldability, transparency, flexibility and chemical resistance possessed by the conventional high-pressure radical polymerization polyethylene resin. Moreover, it has a higher melting point and is superior in heat resistance as compared with a polyethylene resin having the same density manufactured by a conventional high-pressure radical polymerization method. For this reason, the high-melting low-density polyethylene resin of the present invention and the composition containing the resin can be used even in fields where conventional heat resistance was inferior and could not be used, and a higher-performance molded product could be provided. Suitable especially for applications requiring heat resistance such as power cable insulation layer, coaxial cable foam layer, photographic paper support layer, various packaging films, hot water transport pipe, back-in-box, laminate layer, bottle, etc. used. According to the method for producing the resin of the present invention, which comprises performing the polymerization by setting the reaction pressure higher and lowering the polymerization peak temperature lower than the ordinary polymerization conditions, according to the conventional high-pressure radical polymerization method as described above. Provided is a polyethylene resin which maintains characteristics such as high moldability of the polyethylene resin and has improved heat resistance. In addition, the method for producing a high-melting low-density polyethylene resin of the present invention can be performed according to an easy operation using a conventional apparatus as it is.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Takeshi Tachikawa 1-17-1-405, Konan-ku, Yokohama-shi, Kanagawa Prefecture (72) Wataru Minoshima 1139-1-3-111, Shinyoshida-cho, Kohoku-ku, Yokohama-shi, Kanagawa Prefecture

Claims (5)

[Claims] 1. Produced by a high-pressure radical polymerization method, having a density ρ (g / cm ³ ) of 0.910 ≦ ρ ≦ 0.930 and a melt index MI (g / 10 minutes) of 0.01 ≦ MI.
≦ 300, the number of short-chain branches Sb expressed by the number of methyl groups per 1000 carbon atoms is 5 ≦ Sb ≦ 60, and the melting point Tm
(° C.) is 118.5−0.370 × Sb ≦ Tm ≦ 11
A high-melting low-density polyethylene resin having a range of 8.5 to 0.170 × Sb. 2. A resin composition comprising the high melting point low density polyethylene resin according to claim 1. 3. A molded article produced from the high melting point low density polyethylene resin according to claim 1 or the resin composition according to claim 2. 4. A method for producing a molded product, comprising using the high melting point low density polyethylene resin according to claim 1 or the resin composition according to claim 2. 5. The high-melting low-density polyethylene according to claim 1, wherein ethylene is polymerized at a polymerization reaction peak temperature of 180 to 320 ° C. and a polymerization pressure of 100 to 400 MPa in the presence of a radical generating catalyst and a chain transfer agent. Method of manufacturing resin.