JP3357197B2 - Crosslinked polyethylene resin foam - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION This invention relates to crosslinked port Riechiren resin foam, and more particularly, foaming is good and uniform appearance beautiful shape of cells, tough and flexible cross-linking onset <br/> For foam. Crosslinked foams are also excellent in secondary workability .

[0002]

2. Description of the Related Art Foams of polyethylene resin are excellent in flexibility and heat insulation, and have been used for various purposes as cushioning materials and heat insulation materials. The type of polyethylene resin is selected according to the purpose of use.For example, when flexibility is particularly required, low-density polyethylene is used, but when more toughness is required, straight-chain polyethylene is used. A low-density polyethylene or a resin composition comprising a low-density polyethylene and a linear low-density polyethylene has been used (Japanese Patent Publication No. 61-57334).

[0003] Linear low-density polyethylene is a copolymer of ethylene and an α-olefin. However, in order to increase flexibility, a resin containing an increased amount of an α-olefin as a copolymer component is used. In general, such resins are divided into a polymer component having a low molecular weight in which a copolymer component is introduced into a molecular chain and a polymer component having a high molecular weight in which a copolymer component is hardly introduced. A great variation occurs in the viscosity, and the foaming property decreases. Specifically, the expansion ratio does not increase, or even if a foam having a satisfactory expansion ratio is obtained, problems such as unevenness in appearance occur, very large bubbles and small bubbles are mixed, and during the secondary processing There was a problem of breaking from the non-uniform foamed portion.

Further, a thin-walled foam is used instead of a cloth or a soft synthetic resin sheet for a tape base material or a sheet base material used for a compress material, an anti-inflammatory analgesic plaster, and the like.
Such a tape substrate or sheet substrate is required to have flexibility and toughness (good elongation and tensile strength).
As this kind of tape base material or sheet base material, there has been proposed a cross-linked foam comprising a resin composition of an ethylene-vinyl acetate copolymer and a linear low-density polyethylene (Japanese Patent Publication No. 2-33387). However, the above-mentioned crosslinked foam for a tape substrate or a sheet substrate has a poor balance between flexibility and toughness. That is, when the composition ratio of the ethylene-vinyl acetate copolymer is increased in order to obtain a more flexible product, there is a problem that the tensile strength is reduced.

[0005] In addition, since the viscosity of a conventional polyethylene resin at a high temperature or at the time of melting is extremely reduced, it is generally necessary to secure the viscoelasticity required at the time of foaming and to retain generated bubbles. Crosslinking is applied. Crosslinking of polyethylene-based resin is performed by irradiation crosslinking method with ionizing radiation, peroxide crosslinking method in which resin radicals are generated by peroxide and crosslinking, and polyfunctional monomer is used when radicals are generated by irradiation or peroxide. A method of adding and crosslinking, or a crosslinking method by silanol condensation (silane crosslinking method) is industrially performed .

However, conventional polyethylene resins are:
It is difficult to control the degree of cross-linking, and it is not easy to produce a cross-linked foam of constant quality .

On the other hand, in recent years, various studies have been made on a method of polymerizing a polyolefin having a narrow molecular weight distribution by using a metallocene compound as an α-olefin polymerization catalyst so that a copolymer component is uniformly present in a molecular chain. (JP-A-3-188092, JP-A-4-27959)
No. 2), the possibility of a new polyethylene resin is expected. However, no studies or proposals have been made on foaming of a polyethylene resin using a metallocene catalyst.

[0008]

[SUMMARY OF THE INVENTION An object of the present invention, foaming is good and uniform appearance beautiful shape of cells, with strong and <br/> flexible, crosslinked port Riechiren excellent in secondary processability An object of the present invention is to provide a system resin foam .

It is a further object of the present invention to provide a crosslinked polyethylene resin foam having good foamability, toughness and flexibility for a tape base or a sheet base.

As a result of intensive studies, the present inventors have found that the above object can be achieved by using a polyethylene resin obtained by using a metallocene compound as a polymerization catalyst or a polyethylene resin having specific physical properties. The present invention has been completed based on the findings.

[0011]

According to the present invention, a homopolymer of ethylene or a mixture of ethylene and α obtained by using a metallocene compound containing a tetravalent transition metal as a polymerization catalyst is provided.
-Crosslinking a polyethylene resin consisting of a copolymer with an olefin and foaming at a foaming ratio of at least 2 times or more.
Crosslinking Po Riechiren resin foam is provided that. Also,
According to the invention, the density is between 0.860 and 0.950 g / c
m ³ , the temperature range from the temperature at which 10% by weight is eluted by the cross fractionation method to the temperature at which 100% by weight is eluted is 30 ° C. or less, and the value of weight average molecular weight / number average molecular weight is 1 crosslinking the polyethylene resin comprising a copolymer of .5～3.5 ethylene homopolymer or ethylene and α- olefin ing foamed at least twice or more expansion ratio crosslinked port Riechiren resin A foam is provided .

Further, according to the present invention, an ethylene homopolymer or ethylene having a density of 0.840 to 0.925 g / cm ³ can be obtained by using a metallocene compound containing a tetravalent transition metal as a polymerization catalyst. When crosslinking the polyethylene resin comprising a copolymer of α- olefins, low <br/> without even crosslinked polyethylene resin for or sheet substrate tape base material formed by foaming with 4 times expansion ratio A foam is provided. Furthermore, according to the invention, the density is 0,0.
840 to 0.925 g / cm ³ , a temperature range from the temperature at which 10% by weight is eluted by the cross fractionation method to the temperature at which 100% by weight is eluted is 30 ° C. or less, and the weight average molecular weight / number The value of the average molecular weight is 1.5-3.
Crosslinking polyethylene resin consisting of homopolymer of ethylene or copolymer of ethylene and α-olefin
And, cross-linked polyethylene-based resin foam for or sheet substrate tape base material formed by foaming with 4 times expansion ratio even without least is provided.

Hereinafter, the present invention will be described in detail. Polyethylene resin The polyethylene resin used in the present invention comprises a homopolymer of ethylene or a copolymer of ethylene and an α-olefin . Examples of the α-olefin include propylene, 1-butene, 1-pentene, 1-hexene,
4-methyl-1-pentene, 1-heptene, 1-octene and the like.

The polyethylene resin used in the present invention comprises:
First, a polyethylene-based resin obtained by polymerizing ethylene or ethylene and an α-olefin using a metallocene compound containing a tetravalent transition metal as a polymerization catalyst, and is preferably a differential scanning calorimeter (DSC) )), And the temperature range from the melting peak temperature to the end of melting of all crystals within 20 ° C. is one.

The polyethylene resin used in the present invention comprises:
Second, the density is 0.840 to 0.950 g / cm ³ , and the temperature range from the temperature at which 10% by weight is eluted to the temperature at which 100% by weight is eluted by the cross separation method described below is 30 ° C. or less. And the value of weight average molecular weight / number average molecular weight is 1.5 to 3.5. Such a polyethylene resin can be preferably obtained using a metallocene compound containing a tetravalent transition metal as a polymerization catalyst.

Metallocene Compound In the present invention, a polyethylene resin obtained using a metallocene compound (metallocene catalyst) as a polymerization catalyst can be used. A metallocene compound generally refers to a compound having a structure in which a transition metal is sandwiched between π-electron unsaturated compounds, and a bis (cyclopentadienyl) metal complex is a typical example. More specifically, as the metallocene compound in the present invention, a tetravalent transition metal such as titanium, zirconium, nickel, palladium, hafnium, and platinum is combined with one or more cyclopentadienyl rings or analogs thereof as a ligand ( Ligands).

Specific examples of the ligand include a cyclopentadienyl ring; a cyclopentadienyl ring substituted by a hydrocarbon group, a substituted hydrocarbon group or a hydrocarbon-substituted metalloid group; a cyclopentadienyl oligomer ring; And an indenyl ring substituted with a hydrocarbon group, a substituted hydrocarbon group or a hydrocarbon-substituted metalloid group. In addition to these π-electron unsaturated compounds, other ligands include monovalent anion ligands such as chlorine and bromine, or divalent anion chelate ligands, hydrocarbons, alkoxides, arylamides, aryloxides, amides, and arylamides. , Phosphide, aryl phosphide and the like may be coordinated to the transition metal atom.

Examples of the hydrocarbon group substituted on the cyclopentadienyl ring include, for example, methyl, ethyl, propyl, butyl, amyl, isoamyl, hexyl, isobutyl, heptyl, octyl, nonyl, decyl, cetyl, 2-ethylhexyl, phenyl And the like.

Examples of such a metallocene compound include cyclopentadienyl titanium tris (dimethylamide), methylcyclopentadienyl titanium tris (dimethylamide), bis (cyclopentadienyl) titanium dichloride and dimethylsilyltetramethyl. Cyclopentadienyl-tert-butylamidozirconium dichloride, dimethylsilyltetramethylcyclopentadienyl-tert-butylamidohafnium dichloride, dimethylsilyltetramethylcyclopentadienyl-pn-butylphenylamidozirconium chloride, methylphenylsilyl Tetramethylcyclopentadienyl-tert-butylamido hafnium dichloride, indenyl titanium tris (dimethylamide), indenyl tita Umutorisu (diethylamide), indenyl titanium tris (di -n- propyl amide), indenyl titanium bis (di -n- butylamide) (di -n- propyl amide) and the like.

The metallocene compound exhibits a function as a catalyst when various olefins are polymerized by changing the type of metal and the structure of the ligand and combining them with a specific cocatalyst (cocatalyst). More specifically, the polymerization is usually performed in a catalyst system obtained by adding methylaluminoxane (MAO), a boron compound, or the like as a cocatalyst to these metallocene compounds. The use ratio of the cocatalyst to the metallocene compound is 1
0 to 1,000,000 mole times, preferably 50 to 5,
000 mol times.

The polymerization conditions are not particularly limited, and examples thereof include a solution polymerization method using an inert medium, a bulk polymerization method in which substantially no inert medium is present, and a gas phase polymerization method. The polymerization temperature is usually from -100 ° C to 300 ° C.
In general, the polymerization is carried out at a temperature of 100 ° C. and a pressure of 100 kg / cm ² .

The metallocene catalyst is characterized in that the active site properties are uniform. Since the metallocene catalyst has the same activity at each active site, the molecular weight, molecular weight distribution, composition, and compositional uniformity of the polymer to be synthesized are improved. Therefore, the molecular weight distribution of the polyolefin polymerized with these metallocene catalysts is narrow, and in the case of a copolymer, the copolymer component is introduced at a substantially equal ratio to any molecular weight component. Examples of the polyethylene resin obtained using a metallocene compound as a polymerization catalyst include, for example,
Dow Chemical's CGCT and Exxon Chemical's EXACT are commercially available.

Cross Separation Method The cross separation method employed in the present invention is as follows. First, a polyethylene-based resin is dissolved in o-dichlorobenzene at 140 ° C. or a temperature at which the polyethylene-based resin is completely dissolved, then cooled at a constant speed, and a thin polymer is placed on the surface of an inert carrier prepared in advance. The layers are formed in order of crystallinity and molecular weight.
Next, the temperature is raised continuously or stepwise, and the concentration of the components eluted sequentially is detected to measure the composition distribution (crystallinity distribution). This was eluted at elevated temperature (Temperata
re Rising Elution Fraction
nation; TREF). At the same time, the components eluted sequentially are subjected to high-temperature GPC (Size Exlusion).
Chromatography (SEC) to determine the molecular weight and molecular weight distribution. In the present invention, the above data was measured using a cross-separation chromatograph (CFC-T150A type, manufactured by Mitsubishi Yuka Co., Ltd.) having both the above-mentioned temperature-rise elution fractionation part and the high-temperature GPC part as a system.

The polyethylene resin used in the present invention has a temperature of 1 wt.
The temperature range at the end of the dissolution of 00% by weight is usually 30 ° C or lower, preferably 28 ° C or lower. This temperature range is 30 ° C
If it is excessive, a high crystallinity component and a low crystallinity component will be present simultaneously in the polyethylene resin, resulting in uneven viscosity of the molten resin during foaming, making it difficult to obtain a uniform foam. is there.

The polyethylene resin used in the present invention usually has a value of weight average molecular weight / number average molecular weight (Mw / Mn) of 1.5 to 3.
5, preferably in the range of 1.7 to 3.0. When this value is less than 1.5, the strength of the resin foam is improved, but the resin becomes difficult to flow at the time of melting, and molding becomes difficult. On the other hand, if this value exceeds 3.5, the dispersion of the molecular weight distribution becomes large, the ratio of the low molecular weight to the high molecular weight increases, and the viscosity of the molten resin at the time of foaming becomes uneven, resulting in uniform foaming. It becomes difficult to get a body.

Differential Scanning Calorimetry The differential scanning calorimetry in the present invention was performed by the following method. About 10 mg of a polyethylene-based resin sample was placed in a platinum pan, and measured with a differential scanning calorimeter (DSC) (SSC5200 manufactured by Seiko Instruments Inc.). The measurement conditions are
Once the sample has been melted, -50 at a rate of 5 ° C./min.
C., and then the temperature was increased at a rate of 5 ° C./min for measurement.

The polyethylene resin used in the present invention usually has one crystal melting peak in differential scanning calorimetry, and has a temperature range of 20 ° C. or less from the melting peak temperature until all crystals are completely melted. Preferably, there is. A single crystal melting peak includes a case where the crystal melting peak is not clearly divided into two or more peaks.

The presence of a plurality of crystal melting peaks means the presence of a plurality of components having different crystallinities. In this case, the viscosity of the molten resin during foaming becomes uneven,
It is difficult to obtain a uniform foam. 1 melting peak
However, if the temperature range from the melting peak temperature to the end of melting of all the crystals exceeds 20 ° C., the difference in crystallinity between high and low crystallinity between polyethylene molecules increases, Again, the viscosity of the molten resin during foaming becomes uneven, making it difficult to obtain a uniform foam.

Density The polyethylene resin used in the present invention generally has a density of 0.860 to 0.950 g / cm ³ , preferably 0.8
It is in the range of 70 to 0.945 g / cm ³ . If the density is less than 0.860 g / cm ³ , the crystallinity of the polyethylene resin is low, and the heat resistance of the foam is reduced.
Conversely, if it exceeds 0.950 g / cm ³ , problems will occur in the flexibility and elongation of the obtained foam.

In particular, when a tape-like crosslinked polyethylene resin foam for a tape substrate or a sheet substrate is obtained, the density is 0.840 to 0.925 g / cm ³ , preferably 0.860 to 0.25 g / cm ³ . A 910 g / cm ³ polyethylene resin is used. If the density is less than 0.840 g / cm ³ , the crystallinity of the polyethylene resin is low, which causes a problem in the heat resistance of the foam. Conversely, if it exceeds 0.910 g / cm ³ , the flexibility and elongation of the obtained foam are reduced.

Optional Components In the present invention, other thermoplastic resins may be added to the polyethylene resin as long as the object of the present invention is not impaired.
For example, a foam can be formed by adding low-density polyethylene, linear low-density polyethylene, medium-density polyethylene, high-density polyethylene, polypropylene, ethylene-propylene rubber, polyvinyl acetate, polybutene, or the like.
The mixing ratio of the other thermoplastic resin is usually 30% by weight or less based on the entire resin component. Among these thermoplastic resins, linear low-density polyethylene is preferred. In the present invention, within a range that does not impair the physical properties of the crosslinked port Riechiren resin foam, phenolic, phosphorus-based, amine-based antioxidant of the sulfur-based or the like, a metal deactivator, flame retardants, fillers, antistatic Agents, stabilizers, pigments and the like may be added.

The polyethylene resin in the crosslinking present invention, as required for heat resistance and foaming process of the finally obtained foam, cross-linking
Is applied. As a general crosslinking method, a method in which a radical generator such as a peroxide mixed in a resin is thermally decomposed and crosslinked, crosslinking by irradiation with ionizing radiation, crosslinking by irradiation with ionizing radiation in the presence of a polyfunctional monomer And silane crosslinking.

[0033]

Method for Producing Foam The foam of the present invention is obtained by, for example, mixing a substance which generates a gas when heating the above-mentioned polyethylene resin, and gasifying or decomposing the substance by heating or reducing the pressure to form a resin. Manufactured by creating bubbles in the body.
As a substance serving as a gas generating source, (1) itself is a gas at normal temperature and normal pressure, but a substance dispersed or dissolved in a resin, specifically, carbon dioxide gas, difluorodichloromethane, etc. 2) gasification when heated,
Specifically, methanol, water, and the like (3) those that generate a decomposition gas by heating, specifically, azodicarbonamide, benzenesulfonylhydrazide, dinitrosopentamethylenetetramine, toluenesulfonylhydrazide,
4,4-oxybis (benzenesulfonyl hydrazide)
And other organic thermal decomposition type foaming agents.

[0035] As a method for producing put that crosslinking port Riechiren based foam to the present invention include, for example, the following manufacturing method.

Foaming method using thermal decomposition type foaming agent The above-mentioned polyethylene type resin, organic thermal decomposition type foaming agent such as azodicarbonamide, and if necessary, other additives and thermoplastic resin are mixed with a single screw extruder, a twin screw extruder. Using a kneading device such as an extruder, a Banbury mixer, a kneader mixer, or a roll, melt-kneading is performed at a temperature lower than the decomposition temperature of the pyrolytic foaming agent to form a foamable resin composition, which is generally formed into a sheet. Molding. Next, when the sheet is heated to a temperature equal to or higher than the decomposition temperature of the foaming agent and foamed, a foam can be obtained.

The mixing ratio of the organic thermal decomposition type foaming agent is usually 1 to 50 parts by weight based on 100 parts by weight of the specific polyethylene resin or a mixture (resin component) of the resin and another thermoplastic resin. Parts, preferably 4 to 25 parts by weight. If the mixing ratio of the organic thermal decomposition type foaming agent is too small, the foaming property of the foam decreases, and if it is too large, the strength of the foam decreases.

In order to obtain a crosslinked foam by this method, the above-mentioned polyethylene resin, an organic pyrolysis type foaming agent, a polyfunctional monomer as a cross-linking aid if desired, and an optional compounding agent as desired are added to the pyrolysis type foaming agent. Is melted and kneaded at a temperature lower than the decomposition temperature to form a sheet. The obtained foamable resin composition sheet is irradiated with a predetermined amount of ionizing radiation to crosslink the polyethylene resin, and then the crosslinked sheet is foamed by heating it to a temperature not lower than the decomposition temperature of the foaming agent. Examples of ionizing radiation include α-rays, β-rays, γ-rays, and electron beams. In addition, peroxide crosslinking or silane crosslinking can be performed instead of irradiation crosslinking with ionizing radiation.

The molding the foaming process the polyethylene resin in a pressure vessel a sheet by a press machine or an extruder, into a desired shape such as a block shape. Then
The molded body is put into a pressure vessel, the physical foaming agent is sufficiently dissolved in the resin, and then the pressure is reduced to produce a foamed body. Further, in a pressure vessel into which the molded body has been charged, pressurize after filling with a physical foaming agent at room temperature,
It is also possible to take out after decompression and to heat it in an oil bath, oven or the like to foam it. If the molded article is crosslinked in advance, a crosslinked foam can be obtained.

The crosslinking port Riechiren resin foam crosslinked port Riechiren resin foam of the invention is a homogeneous beautiful foam expansion ratio more than twice, flexibility, toughness,
Excellent moldability .

Further, crosslinking port Riechiren resin foam of the invention, the expansion ratio is crosslinked foam for or sheet substrate for 4 times more uniform beautiful tape base material, particularly flexibility and toughness Are better. The reason for such a result is not clear, but is presumed as follows.

Since the polymerization reaction using a metallocene catalyst has the feature that the reaction active sites are uniform, a polymer having the same molecular weight and the same degree of branching is produced. The most remarkable phenomenon of this phenomenon is a copolymerization of ethylene and an α-olefin as compared with the case of polymerization using a usual Ziegler-Natta catalyst. In the polymerization using a normal catalyst, α is a copolymer component in a polymer component having a low molecular weight.
-A large amount of olefin is introduced and hardly introduced into the high molecular weight polymer component. As a result, a very hard and highly crystalline component and a soft and low crystalline component are mixed in the formed resin. The process of foaming is divided into a process of growing bubbles in the molten resin and a process of fixing the bubble cells by crystallization and solidification of the resin. Further, if there is a difference in the crystallization speed, it affects the process of fixing the bubble cells, respectively, resulting in poor foaming due to outgassing and poor appearance due to variations in bubble diameter. In other words, polymerization using a metallocene catalyst can provide a polyethylene-based resin having a small variation in molecular weight and crystallinity, and thus it is considered that the above problem does not occur when the resin is foamed.

Further, in the polyethylene resin obtained by using the metallocene catalyst, a considerable amount of long-chain branching is generated together with short-chain branching. As a result, in the region below the melting point, this resin has a structure in which a component having high crystallinity is dispersed in a component having low crystallinity. It becomes a resin rich in properties. On the other hand, in the region of the resin having a melting point or higher, the melt viscosity is increased by entanglement of long chain branches . In melting point below the melting point or more regions, by the action of branched short chain and long chain, highly flexible foam can be obtained.

The polyethylene resin as described above is not only defined as a polyethylene resin obtained using a metallocene catalyst, but also has a density of 0.840 to 0.950.
g / cm ³ , and 10% by weight by a cross-fractionation method.
100% by weight from the temperature at the time of elution The temperature range at the time of completion of elution is 30 ° C. or less, and the value of weight average molecular weight / number average molecular weight is defined as 1.5 to 3.5. It is possible to use a polyethylene resin having such properties. Examples of the polyethylene-based resin include those obtained using a vanadium-based catalyst.

[0045]

The present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited to these examples. In addition, the measuring method and evaluation method of various physical properties are as follows. <Appearance> The foam was visually observed and evaluated according to the following criteria. ：: No blur, blister, dent, surface roughness, etc. X: There is one or more spots such as blurring, blisters, dents, and surface roughness. <Bubble shape> A cross section of the foam was photographed with a scanning electron microscope S-2300 manufactured by Hitachi, Ltd. at a magnification of 50 times using an electron micrograph. The micro bubbles having a diameter of 20 μm or less and a diameter of 3 m were obtained.
The presence or absence of a maximal bubble of m or more was confirmed.

[Example 1] (Crosslinked foam) A polyethylene resin obtained by using a metallocene compound as a polymerization catalyst (EXACT3 manufactured by Exxon Chemical Co., Ltd.)
027: Density = 0.900 g / cm ³ ; Weight average molecular weight / Number average molecular weight = 2.0; The measurement results of the cross fractionation method and the DSC are as shown in Table 1. ) With 100 parts by weight of divinylbenzene 0.8 as a crosslinking aid
Parts by weight, 11 parts by weight of azodicarbonamide as a foaming agent, 0.3 parts by weight of 2,6-di-t-butyl-p-cresol and 0.3 parts by weight of dilaurylthiodipropionate as antioxidants, and metal 0.5 parts by weight of methylbenzotriazole was added as a harm inhibitor, and the mixture was melt-kneaded at 170 ° C. using two rolls. The foamable resin composition obtained by melt-kneading was hot-pressed to form a sheet having a thickness of 1 mm. The sheet was irradiated with an electron beam at an acceleration voltage of 700 kV for 2.0 Mrad to crosslink the polyethylene resin. This crosslinked sheet was suspended in an oven at 250 ° C. and foamed. The foam obtained had a foaming ratio of 20 times and uniform appearance. Table 1 shows the results of evaluating the appearance and cell shape of the obtained polyethylene resin foam.
Shown in

Example 2 (Cross-Linked Foam) A polyethylene resin obtained by using a metallocene compound as a polymerization catalyst (EXACT4 manufactured by Exxon Chemical Co., Ltd.)
011: density = 0.885 g / cm ³ ; weight average molecular weight / number average molecular weight = 2.1; the measurement results of the cross fractionation method and the DSC are as shown in Table 1. ) 8 parts by weight of azodicarbonamide as a foaming agent, 0.3 parts by weight of 2,6-di-t-butyl-p-cresol and 0.3 parts of dilaurylthiodipropionate as antioxidants, based on 30 parts by weight Parts by weight and 0.5 parts by weight of methylbenzotriazole as a metal damage inhibitor were added and melt-kneaded at 170 ° C. using two rolls. The foamable resin composition obtained by melt-kneading was hot-pressed to form a sheet having a thickness of 1 mm. The sheet was irradiated with an electron beam at an acceleration voltage of 700 kV for 4 Mrad to crosslink the polyethylene resin.
This sheet was suspended in an oven at 250 ° C. and foamed. The foam obtained had an expansion ratio of 8.5 times and uniform appearance. Table 1 shows the results of evaluating the appearance and cell shape of the obtained polyethylene resin foam.

[0048]

[0049]

[Comparative Example 1] (Crosslinked foam) As a polyethylene resin, a linear low-density polyethylene resin obtained by using a titanium trichloride catalyst (1044D, manufactured by Idemitsu Petrochemical Co., Ltd .: density = 0.925 g / cm ³ ; weight average molecular weight / number average molecular weight = 4.0; the measurement results of the cross fractionation method and the DSC are as shown in Table 1.)
When a crosslinked foam was produced in the same manner as in Example 1 except for using, a foam having an expansion ratio of 18 times was obtained. This foam had irregularities on the surface, and in some places, a thin portion of the resin, which appeared to be caused by large bubbles when held over light, was observed. Table 1 shows the results of evaluating the appearance and cell shape of the obtained polyethylene resin foam.

[0051]

[0052]

[Table 1] (Footnote) * 1: Mw = weight-average molecular weight, Mn = number-average molecular weight * 2: T1 = temperature at which 10% by weight of total resin elutes by GPC analysis T2 = temperature at which elution of all resins elutes by GPC analysis * 3: T3 = Melting peak temperature by DSC analysis T4 = melting end temperature by DSC analysis

[0053]

[0054]

[0055]

[0056]

[0057]

[0058]

[0059]

[0060]

[0061]

Example 3 (Crosslinked Foam for Tape Base Material or Sheet Base Material) Polyethylene resin obtained by using a metallocene compound as a polymerization catalyst (EXACT3 manufactured by Exxon Chemical Co., Ltd.)
027, density = 0.900 g / cm ³ ; weight average molecular weight / number average molecular weight = 2.0; the measurement results of the cross fractionation method and the DSC are as shown in Table 2 . 5) Azodicarbonamide as a foaming agent, 2 parts by weight of zinc stearate as a foaming aid, and 0.3 parts by weight of 2,6-di-t-butyl-p-cresol as an antioxidant, based on 100 parts by weight. Part and dilauryl thiodipropionate 0.3
Parts by weight, and 0.5 parts by weight of methylbenzotriazole as a metal damage inhibitor, and 170
The mixture was melt-kneaded at ℃. The foamable resin composition obtained by melt-kneading was hot-pressed to form a sheet having a thickness of 1 mm.
An electron beam is applied to this sheet at an acceleration voltage of 700 kV for 2.0 M.
Radiation was applied to crosslink the polyethylene resin. This crosslinked sheet was suspended in an oven at 220 ° C. and foamed. The obtained crosslinked foamed sheet had a foaming ratio of 9.6 times and uniform appearance. In order to evaluate the flexibility and toughness of the crosslinked foamed sheet, surface hardness (Shore A hardness), elongation and tensile strength (JIS K67) were evaluated.
67 based). Table 2 shows the results of these evaluations .

Example 4 (Crosslinked Foam for Tape Substrate or Sheet Substrate) Polyethylene resin obtained by using a metallocene compound as a polymerization catalyst (EXACT4 manufactured by Exxon Chemical Co., Ltd.)
011; density = 0.855 g / cm ³ ; weight-average molecular weight / number-average molecular weight = 2.1; the measurement results of the cross fractionation method and the DSC are as shown in Table 2 . A crosslinked foamed sheet was obtained in the same manner as in Example 10 except that (1) was used. The obtained crosslinked foamed sheet had an expansion ratio of 10.2 times and uniform appearance. Table 2 shows the evaluation results of the obtained crosslinked foamed sheets.

Example 5 (Crosslinked Foam for Tape Base Material or Sheet Base Material) Polyethylene resin obtained by using a metallocene compound as a polymerization catalyst (EXACT3 manufactured by Exxon Chemical Co., Ltd.)
001, density = 0.910 g / cm ³ ; weight average molecular weight / number average molecular weight = 2.0; the measurement results of the cross fractionation method and DSC are as shown in Table 2 . A crosslinked foamed sheet was obtained in the same manner as in Example 3 except that ( 3 ) was used. The obtained crosslinked foamed sheet had an expansion ratio of 10.4 times and uniform appearance. Table 2 shows the evaluation results of the obtained crosslinked foamed sheets.

Example 6 (Cross-Linked Foam for Tape Base or Sheet Base) Polyethylene resin obtained by using a metallocene compound as a polymerization catalyst (AFFINIT manufactured by Dow Chemical Company)
Y: PL1880, density = 0.920 g / cm ³ ; weight average molecular weight / number average molecular weight = 2.0; the measurement results of the cross fractionation method and DSC are as shown in Table 2 . )
A crosslinked foamed sheet was obtained in the same manner as in Example 3 , except for using. The obtained crosslinked foamed sheet has an expansion ratio of 1
It was 0.1 times and uniform in appearance. Table 2 shows the evaluation results of the obtained crosslinked foamed sheets.

[ Example 7] (Crosslinked foam for tape base material or sheet base material) Polyethylene resin obtained by using a metallocene compound as a polymerization catalyst (EXACT2009 manufactured by Exxon Chemical Co., Ltd., density: = 0.922 g /
cm ^3; weight average molecular weight / number average molecular weight = 2.2; measured results of the cross fractionation method and DSC measurement results of a <br/> cage and Table 2 of. A crosslinked foamed sheet was obtained in the same manner as in Example 3 except that ( 3 ) was used. The obtained crosslinked foamed sheet had a foaming ratio of 10.0 times and uniform appearance. Table 2 shows the evaluation results of the obtained crosslinked foamed sheets.

[Comparative Example 2] (Crosslinked foam for tape base material or sheet base material) Polyethylene resin (EXAC manufactured by Exxon Chemical Co., Ltd.)
T3027) A linear low-density polyethylene resin (1044D, manufactured by Idemitsu Petrochemical Co., density = 0.9) obtained by using a titanium trichloride-based catalyst as a polymerization catalyst instead of 100 parts by weight.
25 g / cm ³ ; weight average molecular weight / number average molecular weight = 4.
0: The measurement result of the cross fractionation method and the measurement result of the DSC are in the table.
2 ) 30 parts by weight and ethylene-vinyl acetate copolymer (Showrex EL12- manufactured by Showa Denko KK)
5, a density = 0.932 g / cm ^3; melt index 2.0; vinyl acetate content of 15 wt%) except for using 100 parts by weight of the resin consisting of 70 parts by weight, Example 3
In the same manner as in the above, a crosslinked foamed sheet was obtained. The obtained crosslinked foamed sheet had an expansion ratio of 10.0 times, but had irregularities on the surface and had a poor appearance. Table 2 shows the evaluation results of the obtained crosslinked foamed sheets.

[Comparative Example 3] (Crosslinked foam for tape base material or sheet base material) Polyethylene resin (EXAC manufactured by Exxon Chemical Co., Ltd.)
T3027) A linear low-density polyethylene resin (1044D, manufactured by Idemitsu Petrochemical Co., density = 0.9) obtained by using a titanium trichloride-based catalyst as a polymerization catalyst instead of 100 parts by weight.
25 g / cm ³ ; weight average molecular weight / number average molecular weight = 4.
0: The measurement result of the cross fractionation method and the measurement result of the DSC are in the table.
2 ) A crosslinked foamed sheet was obtained in the same manner as in Example 3 except that 100 parts by weight was used. The resulting crosslinked foamed sheet had an expansion ratio of 10.1 times, but had irregularities on the surface and had a poor appearance. Table 2 shows the evaluation results of the obtained crosslinked foamed sheets.

[0069]

[Table 2] (Footnote) Same as Table 1.

[0070]

According to the present invention, uniform beautifulness, flexibility,
Toughness, excellent crosslinked port Riechiren resin foam moldability is provided.

Further, according to the present invention, there is provided a crosslinked polyethylene resin foam for a tape base material or a sheet base material which is uniform and beautiful and has excellent flexibility and toughness. The crosslinked foam for a tape base material or a sheet base material is suitably used, for example, by applying an adhesive to both surfaces of the base material and bonding and fixing the side molding of an automobile. Further, for example, a pressure-sensitive adhesive containing an anti-inflammatory agent or other desired agent is applied to one surface of the base material, and is suitably used as a medical tape or sheet.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hiroshi Abe 2-2, Kamitobakamichochocho, Minami-ku, Kyoto Sekisui Chemical Co., Ltd. (72) Inventor Kazuo Yamagata 2-1 Shimomotocho, Mishima-gun, Osaka 2-1. Sekisui Chemical Industry Co., Ltd. (56) References Special Table 8-508764 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) C08J 9/04

Claims (9)

(57) [Claims] 1. A polyethylene-based resin comprising a homopolymer of ethylene or a copolymer of ethylene and an α-olefin obtained by using a metallocene compound containing a tetravalent transition metal as a polymerization catalyst is crosslinked to form at least 2 foamed ing crosslinked by more than twice the expansion ratio Po Riechiren resin foam. 2. A port Riechiren based resin is one crystal melting peak measured using a differential scanning calorimeter (DSC), and the temperature range up to the total crystal melting peak temperature finishes melting 20 Frames of der Ru claim 1, wherein those within ℃
Hashipo Riechiren resin foam. 3. A polyethylene resin having a density of 0.86.
0 to 0.950 g / cm ³ , the temperature range from the temperature at which 10% by weight is eluted by the cross fractionation method to the temperature at which 100% by weight is eluted is 30 ° C. or less, and
Crosslinking port Riechiren system according to claim 1 or 2, wherein the value of the weight average molecular weight / number average molecular weight is of 1.5 to 3.5
Resin onset foam. 4. A density of 0.860 to 0.950 g / cm.
³ , the temperature range from the temperature at which 10% by weight is eluted by the cross fractionation method to the temperature at which 100% by weight is eluted is 30 ° C. or less, and the value of weight average molecular weight / number average molecular weight is 1. crosslinking the polyethylene resin comprising a copolymer of 5 to 3.5 ethylene homopolymer or ethylene and α- olefin foam to name Ru crosslinked port Riechiren based resin foam with at least 2-fold or more expansion ratio body. 5. The port Riechiren based resin is one crystal melting peak measured using a differential scanning calorimeter (DSC), and the temperature range up to the total crystal melting peak temperature finishes melting 20 Frames of der Ru claim 4, wherein those within ℃
Hashipo Riechiren resin foam. 6. A polymerization catalyst obtained by using a metallocene compound containing a tetravalent transition metal as a polymerization catalyst and having a density of 0.840 to
Crosslinking the polyethylene resin comprising a copolymer of 0.925 g / cm ³ of ethylene homopolymer or ethylene and α- olefin, tape base for material formed through foaming by 4 times or more expansion ratio even without least Alternatively, a crosslinked polyethylene resin foam for a sheet substrate. 7. The polyethylene resin has one crystal melting peak measured by using a differential scanning calorimeter (DSC), and has a temperature range of 20 ° C. from the melting peak temperature until all crystals are completely melted. those in which crosslinked polyethylene resin foam for tape base material of claim 6 Symbol mounting or sheet substrate within. 8. The polyethylene resin is 100% by weight from the temperature at which 10% by weight is eluted by the cross fractionation method.
The temperature range at the end of the elution is 30 ° C. or less, and the value of weight average molecular weight / number average molecular weight is 1.5 to 3.
5 of those in which claim 6 or 7 Symbol mounting of the polyethylene resin onset foam crosslinking of tape base material for or sheet substrate. 9. A density of 0.840 to 0.925 g / cm
³ , the temperature range from the temperature at which 10% by weight is eluted by the cross fractionation method to the temperature at which 100% by weight is eluted is 30 ° C. or less, and the value of weight average molecular weight / number average molecular weight is 1. crosslinking the polyethylene resin comprising a copolymer of 5 to 3.5 ethylene homopolymer or ethylene and α- olefin or tape base material formed by foaming with 4 times expansion ratio even without least Crosslinked polyethylene resin foam for sheet base.