JP2000226463A - Polyethylene based resin composition and foam - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide polyethylene based resin compositions excellent in foam moldability, and foams to be obtained by molding the same. SOLUTION: Polyethylene based resin compositions comprise (A) a polyethylene based resin, (B) a crosslinked polyethylene to be obtained by adding 2×10-4-10×10-4 mol peroxide to 100 g ethylene homopolymer or ethylene/α- olefin copolymer and heating the resulting mixture, and (C) a blowing agent, and meet the conditions of (a) a gel content fraction of 0.05-20 wt.%, (b) a ratio of weight average molecular weight to number average molecular weight of the gel content-removed component, measured by GPC, of 1-10, (c) an MFI at 190 deg.C under a load of 2,160 g of 0.1-10 g/10 min.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyethylene resin composition suitable for foam molding and a foam obtained by molding the same.

[0002]

2. Description of the Related Art Foams of polyethylene resin are widely used mainly for cushioning materials, cushioning materials, shock absorbing materials and the like. Most of them are manufactured by a technique called gas foaming. In recent years, from the viewpoint of environmental protection, there has been a great demand for replacing a foam of urethane or a soft vinyl chloride resin with a foam of another resin. Polyethylene resin is often taken up as a candidate for the alternative material, but gas foaming can only produce a strand-shaped foam, which limits its use in sheet-shaped products. In addition, if a method of foaming after cross-linking the polyethylene resin is used, a sheet-like product can be obtained, but the entire system is three-dimensionally cross-linked and cannot be recycled, which is not preferable from the viewpoint of environmental protection.

[0003]

SUMMARY OF THE INVENTION The present invention relates to a polyethylene resin composition which is recyclable and suitable for producing a sheet-shaped polyethylene foam, and a polyethylene foam obtained by molding the same. It provides the body.

[0004]

Means for Solving the Problems The present inventors have conducted intensive studies to solve the above problems, and as a result, have found that a polyethylene resin composition having a specific composition has excellent foam moldability. The invention has been completed. That is, the present invention relates to a polyethylene resin (A), an ethylene homopolymer or an ethylene / α-olefin copolymer 10
It is composed of a crosslinked polyethylene (B) and a foaming agent (C) obtained by adding 2 × 10 ⁻⁴ to 10 × 10 ⁻⁴ mol of peroxide per 0 g and then heating, and comprises the following (a) to (c) The present invention relates to a polyethylene resin composition and a foam that satisfy the conditions.

(A) The gel fraction is 0.05 to 20% by weight. (B) The ratio of the weight-average molecular weight to the number-average molecular weight of the component from which the gel component has been removed as measured by gel permeation chromatography (GPC) is determined. (C) Melt flow rate (MFR) at 190 ° C. under a load of 2160 g is 0.1 to 10 g / 10 min.

The polyethylene resin (A) used in the resin composition of the present invention is a high-density polyethylene or a low-density polyethylene which is an ethylene homopolymer, and ethylene and α.
-Linear low-density polyethylene, medium-density polyethylene, ultra-low-density polyethylene, ethylene / vinyl acetate copolymer, and ethylene / propylene copolymer having a propylene content of 60% by weight or less, which are copolymers with olefin. And one or more of these are used.
The method for producing the polyethylene resin (A) is not particularly limited, and the polyethylene resin (A) can be produced using various catalysts such as a titanium catalyst, a vanadium catalyst, and a metallocene catalyst.

The MFR of the polyethylene resin (A) used in the resin composition of the present invention at 190 ° C. under a load of 2160 g is preferably 0.1 to 10 g / 10 minutes. By being in this range, the obtained resin composition becomes a material suitable for foam molding.

The ratio between the weight average molecular weight and the number average molecular weight of the polyethylene resin (A) used in the resin composition of the present invention measured by gel permeation chromatography (GPC) is 1 to 10. Is preferred. By being in this range, the obtained resin composition becomes a material suitable for foam molding.

The crosslinked polyethylene (B) used in the resin composition of the present invention is 2 × 10 ⁻⁴ per 100 g of ethylene homopolymer or ethylene / α-olefin copolymer.
It is obtained by adding 10 × 10 ⁻⁴ mol of peroxide and then heating. The resulting foam is
The size of the foam cells becomes uniform. The cross-linking reaction is preferably performed without shearing, whereby a foam having a more uniform foam cell size can be obtained. Further, it is preferable that the crosslinked polyethylene is finely crushed by freeze pulverization, mechanical pulverization, or the like, and then blended, since the surface of a product obtained by performing foam molding is reduced.

The gel fraction (the amount of insoluble components) in the crosslinked polyethylene (B) is preferably at least 30% by weight, whereby the foaming ratio is high and the foaming cells are uniform in size. The body is obtained.

The gel fraction was dissolved in 1,2,4-trichlorobenzene at 135 ° C. to prepare a 0.1% solution, which was filtered through a 0.45 micron Teflon filter. It can be evaluated by measuring the weight of the component that could not be obtained.

The blowing agent (C) used in the resin composition of the present invention is optional, and includes organic chemical blowing agents such as azo compounds, nitroso compounds, hydrazine compounds, semicarbazide compounds, azide compounds, triazole compounds and isocyanate compounds. Examples include inorganic chemical blowing agents such as bicarbonate, carbonate, nitrite, and hydride, and one or more of these are used.

The blend ratio of the polyethylene resin (A) and the crosslinked polyethylene (B) is preferably such that (A) / (B) is 99.9 / 0.1 to 70/30 by weight. Thereby, a good foam having a high foaming ratio and a uniform foam cell size can be obtained. The foaming agent (C)
Is preferably 1 to 30 parts by weight of (C) based on 100 parts by weight of (A) + (B) in total, whereby a good foam can be obtained.

The method for producing the resin composition of the present invention is optional. The polyethylene resin (A), the crosslinked polyethylene (B), and the blowing agent (C) are blended by an internal mixer or a roll mill kneader. Can be.

The gel fraction of the resin composition of the present invention is 0.0
5 to 20% by weight. This makes it possible to mold a good foam having a high expansion ratio and a uniform size of the foam cells. The measurement of the gel fraction is performed by the above method. This measurement can also be performed using the product after foam molding, and is characterized in that the gel fraction in the product is 0.05 to 20% by weight.

The components of the resin composition of the present invention from which the gel component has been removed have a (weight average molecular weight / number average molecular weight) of 1 to 10%.
It is. If the ratio is out of this range, a foam having a non-uniform foam cell size may be obtained when foam molding is performed. The component from which the gel component has been removed refers to a component filtered with a Teflon filter at the time of gel fraction measurement. The weight average molecular weight and the number average molecular weight are measured by gel permeation chromatography (GPC). In addition, this measurement can also be performed using the product after performing foam molding.

Further, the resin composition of the present invention has a
° C, melt flow rate (MF
R) is 0.1 to 10 g / 10 min. In addition, this measurement can also be performed using the product after performing foam molding. If the ratio is out of this range, the foaming ratio of the obtained foam may decrease.

The resin composition of the present invention may contain, if necessary,
For example, calcium carbonate, mica, talc, silica, barium sulfate, calcium sulfate, kaolin, clay, pyroferrite, bentonite, sericanite, zeolite, nephelincinite, attapulgite, wollastonite, ferrite, calcium silicate, magnesium carbonate, dolomite, Antimony trioxide, titanium oxide,
An inorganic filler such as iron oxide, molybdenum disulfide, graphite, gypsum, glass beads, glass powder, glass balloon, glass fiber, quartz, quartz glass, or an organic or inorganic pigment may be blended. Also, crystal nucleating agents, clarifying agents, anti-blocking agents, release agents, antistatic agents, slip agents, anti-fog agents, lubricants, heat stabilizers, ultraviolet light stabilizers, light stabilizers, weather resistance stabilizers, fungicides An agent, a rust preventive, an ion trapping agent, a flame retardant, a flame retardant auxiliary, and the like may be added as necessary.

Further, other rubbers and thermoplastic resins may be blended in the resin composition of the present invention without departing from the object of the present invention. Examples of such rubber include natural rubber, acrylonitrile butadiene rubber, butadiene rubber, isoprene rubber, styrene butadiene rubber, silicone rubber, polynorbornene rubber, and chloroprene rubber. Further, as the thermoplastic resin, for example, ethylene / ethyl acrylate copolymer, polybutene, acid-modified polyolefin, polyamide,
Styrene-based thermoplastic elastomers, polyolefin-based thermoplastic elastomers and the like can be mentioned.

The method of foam molding of the resin composition of the present invention is not particularly limited. However, it is preferable that the resin composition is once formed into a sheet or rod shape and then heated and foamed in a heating furnace. here,
The temperature for forming into a sheet or rod shape must be lower than the decomposition temperature of the blowing agent used. The heating furnace to be used is not limited, and a batch type, a continuous type, or a salt bath can be used. The foam thus obtained has excellent appearance and uniform foam cells.

[0021]

EXAMPLES The present invention will be described below with reference to examples, but these are merely examples, and the present invention is not limited to these examples.

Various measurements in the examples and comparative examples are shown below.

Melt Flow Rate (MFR) Measured at 190 ° C. under a load of 2160 g according to JIS K7210.

Measurement of Gel Fraction (Insoluble Component Amount) A 0.1% solution is prepared by dissolving a crosslinked polyethylene, composition or foam in 1,2,4-trichlorobenzene at 135 ° C. When this was filtered through a 0.45 micron Teflon filter, the weight of the component that could not be filtered was measured and determined.

-Measurement of molecular weight distribution- A polyethylene resin, a composition or a foam from which a gel component has been removed are dissolved in 1,2,4-trichlorobenzene at 135 ° C, and gel permeation chromatography (Millipore Co., Ltd.) ), 150C type GPC), and the weight average molecular weight Mw and the number average molecular weight Mn were measured, and the ratio Mw / Mn was determined.

-Size distribution of foam cells- The foam was cut by a cutter, and the cut surface was observed with a scanning electron microscope. The diameter (Di) of 500 or more foam cells is checked, and (ΣniDi ² / ΣniDi) / (Σ
niDi / Σni) was determined by defining a parameter CSD representing the distribution of cell size. Here, ni represents the number of cells having the diameter Di. The smaller the CSD, the more uniform the cell size.

-Measurement of expansion ratio- Specific gravity (SA) before foam molding and specific gravity (S) after foam molding
B) Substitute hydrometer (trade name ARCHIMIDE)
S, manufactured by NADA Electronics), and (SA) / (SB) was defined as the expansion ratio ER.

Example 1 High-density polyethylene (manufactured by Tosoh Corporation, trade name: Nipolon Hard # 5110, MFR: 0.9 g / 10 min) 5
Was mixed with a roll mill kneader at a surface temperature of 150 ° C., and α, α′-bis (t-butylperoxy-m-isopropyl) benzene (trade name: Perbutyl P, manufactured by NOF CORPORATION) as a peroxide. ) Is 25 × 10 ^-4 mo
1 was added. The obtained kneaded product was crosslinked by heating with a compression molding machine set at 190 ° C. for 15 minutes to obtain a crosslinked polyethylene, which was finely pulverized by freeze-pulverization. The gel fraction of this crosslinked polyethylene was 46%.

30 g of finely ground crosslinked polyethylene,
Linear low-density polyethylene (trade name, manufactured by EXXON)
EXACT3028, MFR: 1.1 g / 10 min, Mw
/ Mn: 1.8) 470 g, hindered phenol-based heat stabilizer (manufactured by Ciba-Geigy, trade name Irganox 1010) 3 g, phosphorus-based heat stabilizer (manufactured by Ciba-Geigy, trade name: Irgafos 168) 3 g The surface temperature 1
The mixture was kneaded with a roll mill kneader at 00 ° C. for 15 minutes. Further, 50 g of p, p'-oxybisbenzenesulfonylhydrazine (manufactured by Sankyo Kasei Co., Ltd., trade name: Cellmic s) is added as a foaming agent, and the mixture is kneaded for 3 minutes to obtain a target resin composition. MFR was measured. This composition was charged into a molding machine to obtain a roll sheet. After compression molding this roll sheet at 100 ° C., it was placed in an oven that had been heated in advance, and foam molding was performed. The oven heater temperature was 190 ° C. and the time was 4 minutes. After the foam was taken out of the oven, the gel fraction, MFR, expansion ratio, molecular weight distribution of the sol, and the distribution of the size of the foam cell of the foam were examined.

Example 2 Linear low-density polyethylene (trade name, manufactured by EXXON)
EXACT4051, MFR: 2.3 g / 10 min, Mw
/ Mn: 1.9) 100 g of peroxide α, α'-bis (t-butylperoxy-m-isopropyl) benzene (trade name: Perbutyl P, manufactured by NOF CORPORATION)
A target composition was obtained in the same manner as in Example 1 except that × 10 ^-4 mol was added to obtain a crosslinked polyethylene (gel fraction: 36%), and various measurements and molding were performed.

Example 3 Instead of linear low-density polyethylene, an ethylene / vinyl acetate copolymer (trade name: UE634, manufactured by Tosoh Corporation)
MFR: 4 g / 10 min, vinyl acetate content: 26% by weight,
Except for using Mw / Mn: 3.9), the target composition was obtained in the same manner as in Example 1, and various measurements and molding were performed.

Comparative Example 1 In Example 1, various measurements and molding were carried out without adding the crosslinked polyethylene.

Comparative Example 2 A composition was obtained in the same manner as in Example 1 except that the concentration of the peroxide was adjusted to 20 × 10 ⁻⁴ mol and the crosslinked polyethylene was prepared, and various measurements were performed.

Comparative Example 3 A composition was obtained in the same manner as in Example 1 except that the concentration of the peroxide was adjusted to 1 × 10 ⁻⁴ mol to ^prepare a crosslinked polyethylene, and various measurements were carried out.

Comparative Example 4 Instead of linear low-density polyethylene, high-density polyethylene (Nipolon Hard # 20, manufactured by Tosoh Corporation)
00, MFR: 15 g / 10 min, Mw / Mn: 4.7)
A composition was obtained in the same manner as in Example 1 except that the composition was used, and various measurements were performed.

Comparative Example 5 A composition was obtained in the same manner as in Example 1 except that 300 g of crosslinked polyethylene and 200 g of linear low-density polyethylene were used, and various measurements were made.

Comparative Example 6 In Example 3, various measurements and molding were carried out without adding the crosslinked polyethylene.

[0038]

[Table 1]

[0039]

The polyethylene resin composition obtained according to the present invention has excellent foam moldability.

Claims (2)

[Claims] 1. A polyethylene resin (A), an ethylene homopolymer or an ethylene / α-olefin copolymer 100
It consists of a crosslinked polyethylene (B) and a foaming agent (C) obtained by adding 2 × 10 ⁻⁴ to 10 × 10 ⁻⁴ mol of peroxide per g and then heating, and comprises the following (a) to (c) A polyethylene resin composition that satisfies the conditions. (A) The gel fraction is 0.05 to 20% by weight. (B) The ratio of the weight-average molecular weight to the number-average molecular weight of the component from which the gel component has been removed measured by gel permeation chromatography (GPC) is 1 to 10. (C) Melt flow rate (MFR) at 190 ° C. and 2160 g load is 0.1 to 10 g / 10 min. 2. A polyethylene foam obtained by molding the resin composition according to claim 1.