JPH09157601A - Adhesive tape base material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an adhesive tape base material which comprises a crosslinked polyethylene resin foam prepared by crosslinking and foaming a polyethylene resin polymerized with a specific polymerization catalyst, having no smell, excellent in flexibility, mechanical strength and resistance to solvents. SOLUTION: As a polymerization catalyst, a metallocene complex containing a tetravalent transition metal such as bis(cyclopentadienyl)titanium dichloride is used to prepare a polyethylene resin and the polyethylene resin is crosslinked and foamed to give a crosslinked polyethylene resin foam with an apparent density of 0.02-0.33g/cm<3> , the gel fraction of 12-70wt.%. This polyethylene resin preferably has <=20 deg.C temperature range from the melting peak temperature to that at which the whole crystals finishes to melt down to the end. In addition, this polymer has the temperature range of <=28 deg.C from that on 10% elution according to the cross fractionation to that on 100% elution and the ratio of 1.7-3 at the weight average molecular weight to the number average molecular weight.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure-sensitive adhesive tape substrate made of a crosslinked polyethylene resin foam which is flexible and has excellent mechanical strength.

[0002]

2. Description of the Related Art Adhesive tape substrates made of crosslinked polyethylene resin foam are known. In order to improve the flexibility and mechanical strength of such an adhesive tape substrate, Japanese Patent Publication No.
-2198 gazette proposes to use a crosslinked polyethylene resin foam composed of a linear low-density polyethylene and an ethylene-vinyl acetate copolymer or an ethylene-ethyl acrylate copolymer as an adhesive tape substrate. There is.

[0003]

However, the pressure-sensitive adhesive tape substrate made of the above-mentioned cross-linked polyethylene resin foam, which has been proposed, improves the flexibility and mechanical strength to some extent, but is still sufficiently satisfactory. Not a thing. That is, when the amount of the ethylene-vinyl acetate copolymer is increased in order to further improve the flexibility, there is a problem that the tensile strength of the foam is particularly lowered and the acetic acid odor is slightly increased.

Further, since the surface of the adhesive tape base material made of the above-mentioned proposed crosslinked polyethylene resin foam is roughened by an organic solvent such as toluene, the adhesive agent applied to such an adhesive tape base material. Another problem is that the solution is restricted.

The present invention solves the above-mentioned problems, and an object of the present invention is to form a crosslinked polyethylene resin foam having no odor, excellent flexibility and mechanical strength, and excellent solvent resistance. It is to provide an adhesive tape substrate.

[0006]

[Means for Solving the Problems] The above object is obtained by crosslinking and foaming a polyethylene-based resin obtained by using a metallocene compound containing a tetravalent transition metal as a polymerization catalyst, and having an apparent density of 0.02 to 0.02. This can be achieved by an adhesive tape base material made of a crosslinked polyethylene resin foam having a gel fraction of 0.33 g / cm ³ and a gel fraction of 12 to 70% by weight.

The polyethylene resin used in the present invention is obtained by homopolymerizing ethylene or copolymerizing ethylene and α-olefin using a metallocene compound containing a tetravalent transition metal as a polymerization catalyst. It is a polyethylene resin. Examples of the α-olefin include propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-heptene, 1-octene and the like.

Here, the metallocene compound generally means
A compound having a structure in which a transition metal is sandwiched between π-electron unsaturated compounds, and a bis (cyclopentadienyl) metal complex is typical. Examples of such metallocene compounds include tetravalent transition metals such as titanium, zirconium, nickel, palladium, hafnium, and platinum, and one or more cyclopentadienyl rings or an analog thereof as a ligand (ligand).
The compounds present as are mentioned.

Specific examples of the ligand include a cyclopentadienyl ring; a cyclopentadienyl ring substituted with a hydrocarbon group, a substituted hydrocarbon group or a hydrocarbon-substituted metalloid group; a cyclopentadienyl oligomer ring; an indenyl ring An indenyl ring substituted by a hydrocarbon group, a substituted hydrocarbon group or a hydrocarbon-substituted metalloid group is exemplified, and one or more of these ligands are present.

In addition to these ligands, monovalent anion ligands such as chlorine and bromine, or divalent anion chelate ligands, hydrocarbons, alkoxides, arylamides, aryloxides, amides, arylamides, phosphides, arylphosphides. And the like may be coordinate-bonded to the transition metal atom.

Hydrocarbon groups for substitution on the cyclopentadienyl ring include methyl, ethyl, propyl, butyl, amyl, isoamyl, hexyl, isobutyl, heptyl,
Examples include octyl, nonyl, decyl, cetyl, 2-ethylhexyl and phenyl.

Examples of the metallocene compound in which these ligands are coordinated include cyclopentadienyl titanium tris (dimethylamide), methylcyclopentadienyl titanium tris (dimethylamide), bis (cyclopentadienyl) titanium dichloride, and dimethyl. Silyltetramethylcyclopentadienyl-t-butylamide zirconium dichloride, dimethylsilyltetramethylcyclopentadienyl-t-butylamide hafnium dichloride, dimethylsilyltetramethylcyclopentadienyl-pn-butylphenylamide zirconium chloride, Methylphenylsilyl tetramethylcyclopentadienyl-t-butylamide hafnium dichloride, indenyl titanium tris (dimethylamide),
Indenyl titanium tris (diethyl amide), indenyl titanium tris (di-n-propyl amide),
Indenyl titanium bis (di-n-butylamide)
(Di-n-propylamide) and the like.

The metallocene compound exerts a function as a catalyst in the polymerization of various olefins by changing the kind of metal and the structure of the ligand and combining it with a specific cocatalyst (cocatalyst). More specifically, the polymerization is usually carried out in a catalyst system in which methylaluminoxane, a boron-based compound or the like as a cocatalyst is added to these metallocene compounds. The ratio of the cocatalyst used to the metallocene compound is 10 to 1,000,000 times, preferably 50 to 5,000 times.

The polymerization conditions are not particularly limited, and a solution polymerization method using an inert medium, a bulk polymerization method substantially free of an inert medium, a gas phase polymerization method and the like can be used. Polymerization temperature is -100 ° C to + 300 ° C, polymerization pressure is 1 to 10.
It is generally performed at 0 kg / cm ² .

The metallocene catalyst is characterized in that the properties of active sites are uniform. Since the metallocene catalyst has the same activity at each active site, the homogeneity of the molecular weight, the molecular weight distribution, the composition, and the composition distribution of the polymer to be synthesized is improved. Therefore, the polyolefins polymerized with these metallocene catalysts have a narrow molecular weight distribution, and in the case of a copolymer, the copolymer components are introduced in almost equal proportions in every molecular weight component.

Examples of polyethylene resins obtained by using a metallocene compound as a polymerization catalyst include, for example, Dow.
It is marketed under the trade names "Affinity" and "Engage" by the chemical company, and under the trade name "EXACT" by the Exxon chemical company.

In particular, the polyethylene resin has one crystal melting peak measured using a differential scanning calorimeter (DSC), and the temperature range from the melting peak temperature to the end of melting of all crystals is 20 ° C. Those within the range are preferable. A single crystal melting peak includes a case where the peak is not clearly divided into two or more peaks.

The differential scanning calorimetric analysis is performed by the following method. That is, about 10 mg of a polyethylene resin sample was put in a platinum pan, and a differential scanning calorimeter (DSC) was used.
(For example, SSC5200 manufactured by Seiko Instruments Inc.). The sample is melted once, cooled to -50 ° C at a rate of 5 ° C / minute, and then heated at a rate of 5 ° C / minute to measure.

The presence of a plurality of crystal melting peaks means that there are a plurality of components having different crystallinity. In that case, the viscosity of the molten resin is uneven during foaming,
It is difficult to obtain a homogeneous foam. Melting peak is 1
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 the polyethylene molecules having high crystallinity and the one having low crystallinity becomes large, After all, the viscosity of the molten resin becomes uneven during foaming, which makes it difficult to obtain a homogeneous foam.

The polyethylene resin is preferably one having a temperature range of 30 ° C. or less, particularly 28 ° C. or less, from the temperature at the time of elution of 10% by weight to the completion of the elution of 100% by weight by the cross fractionation method described later. , The value of weight average molecular weight / number average molecular weight is 1.5 to 3.5, especially 1.7 to
A value of 3.0 is preferable.

The cross fraction analysis is performed by the following method.
First, the polyethylene resin is dissolved in o-dichlorobenzene at 140 ° C. or a temperature at which the polyethylene resin is completely dissolved, and then cooled at a constant rate, and a thin polymer is applied to the surface of an inert carrier prepared in advance. The layers are formed in order of increasing crystallinity and increasing molecular weight.

Next, the temperature is raised continuously or stepwise, and the concentration of the components eluted in sequence is detected to measure the composition distribution (crystallinity distribution). The temperature rising elution fractionation (Te
temperature Rising Elution
Fractionation; TREF). At the same time, the components that were sequentially eluted were added to the high temperature GPC (Size Ex
sion Chromatograph; SE
The molecular weight and molecular weight distribution are measured by analysis according to C).

In the present invention, the measurement is carried out using a cross fractionation chromatograph device (for example, CFC-T150A type manufactured by Mitsubishi Petrochemical Co., Ltd.) equipped with both the temperature rising elution fractionation part and the high temperature GPC part as a system. It

When the width of the temperature at the time of elution of 10% by weight by the cross fractionation method to the temperature at the end of 100% by weight elution is more than 30 ° C., the polyethylene resin contains a component with high crystallinity and a component with low crystallinity. Are present at the same time, unevenness occurs in the viscosity of the molten resin during foaming, and it is difficult to obtain a homogeneous foam.

The weight average molecular weight / number average molecular weight (Mw / Mn) value measured by the cross fractionation method is 1.5.
When it is less than the above range, the strength of the resin foam is improved, but the resin becomes difficult to flow when melted, and molding becomes difficult. vice versa,
If this value exceeds 3.5, the variation in the molecular weight distribution becomes large, the abundance ratio of low molecular weight molecules and high molecular weight molecules increases, and the viscosity of the molten resin during foaming becomes uneven, resulting in a uniform foam. Hard to get.

The polyethylene resin used in the present invention is
Usually, the density is in the range of 0.840 to 0.950 g / cm ³ , preferably 0.860 to 0.910 g / cm ³ . When the density is low, the crystallinity of the polyethylene resin is low, and the heat resistance of the foam is low. Conversely, higher densities reduce the flexibility and elongation of the foam.

The above polyethylene-based resin contains phenol-based, phosphorus-based, and
Various additives used in conventional polyethylene resin foams, such as amine-based and sulfur-based antioxidants, flame retardants, antistatic agents, light stabilizers, cell nucleating agents, and pigments, can be added. .

In order to produce the crosslinked polyethylene resin foam used for the pressure-sensitive adhesive tape base material of the present invention, for example, the following method is preferably adopted. First, a heat-decomposable foaming agent was blended with the above-mentioned polyethylene resin and melt-kneaded at a temperature at which the foaming agent did not decompose to form a foamable sheet, which was irradiated with ionizing radiation to crosslink the resin. Then, it is manufactured by a method of heating and foaming.

As the thermal decomposition type foaming agent, those having a decomposition temperature of about 180 to 270 ° C. are generally preferable.
Azodicarbonamide, benzenesulfonyl hydrazide, N, N'-dinitrosopentamethylenetetramine,
p-Toluenesulfonyl hydrazide, p, p′-oxybis (benzenesulfonylhydrazide) and the like are used. These may be used alone or in combination of two or more. In addition, if necessary, a decomposition accelerator for the foaming agent, a cell nucleus control agent, and a cross-linking aid are added.

The amount of the thermal decomposition type foaming agent to be blended is generally 1 to 35 parts by weight, preferably 2 to 20 parts by weight, based on 100 parts by weight of the polyethylene resin, and is set according to the desired expansion ratio. To be done. The apparent density of the foam is 0.0
It is limited to 2 to 0.33 g / cm ³ , preferably 0.0
It is set to 25 to 0.20 g / cm ³ . Apparent density is 0.
When it is lower than 02 g / cm ³ , the tensile strength of the foam is insufficient, and when the apparent density is higher than 0.33 g / cm ³ , the tensile strength of the foam is high but the flexibility is insufficient. To do.

As the ionizing radiation, electron beam, α ray, β
Rays, gamma rays, etc. are used. The irradiation dose is generally 1 to 20.
It is about Mrad, and the dose is set according to the desired degree of crosslinking. Instead of the method of crosslinking the resin with ionizing radiation, the resin may be crosslinked with an organic peroxide.

In this case, the polyethylene resin is
When blending the heat-decomposable foaming agent, an organic peroxide such as dicumyl peroxide, di-t-butyl peroxide, methyl ethyl ketone peroxide is blended to form a foamable sheet, which is then heated. The organic peroxide is decomposed, thereby cross-linking the resin forming the foamable sheet. The amount of the organic peroxide compounded is generally 0.3 to 5 parts by weight based on 100 parts by weight of the polyolefin resin.

Here, the degree of crosslinking of the foamable sheet is 12 to 70% by weight, preferably 20 to 60% by weight, in terms of gel fraction.
It is more preferably adjusted to 20 to 45% by weight. If the gel fraction is less than 12% by weight, the viscosity of the resin at the time of foaming is too low and the foamability deteriorates. Conversely, the gel fraction is 70% by weight.
When it exceeds, the elongation of the resin at the time of foaming is insufficient and the foamability deteriorates. The gel fraction is adjusted mainly by adjusting the irradiation dose of ionizing radiation or the blending amount of organic peroxide.

The gel fraction of the expandable sheet has the same value in the foamed product obtained by using the expandable sheet. The gel fraction of such a foamable sheet and a foam is specifically, the foamable sheet or the foam (0.2
g) is precisely weighed, and this is used to measure 50 m of xylene at 120 ° C.
It was immersed in 1 for 24 hours and then filtered through a 200-mesh wire mesh, the insoluble matter on the wire mesh was vacuum-dried, and the weight of this insoluble matter was measured with the precise amount of the foamable sheet or foam (0.2 g). It is shown as a value expressed as a weight percentage relative to the weight.

The foamable sheet in which the resin is cross-linked can be formed, for example, by hot air, infrared rays, a metal bath, an oil bath, or the like.
The resin is foamed by the decomposition gas of the foaming agent by heating to a temperature not lower than the decomposition temperature of the thermal decomposition type foaming agent and not lower than the melting point of the resin, for example, 190 to 290 ° C. Thus, the apparent density is 0.02 to 0.33 g / cm ³ and the gel fraction is 12 to 7
0% by weight of a crosslinked polyethylene resin foam is obtained.

Although the thickness of the foam is not particularly limited,
Since it is used as an adhesive tape substrate, it is 0.1-10m
About m is preferable. This invention uses this crosslinked polyethylene resin foam as an adhesive tape substrate.

[0037]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples and comparative examples of the present invention will be described below. Example 1 Polyethylene resin obtained by using a metallocene compound as a polymerization catalyst (EXACT manufactured by Exxon Chemical Co.)
3027) (density 0.900 g / cm ³ , weight average molecular weight / number average molecular weight 2.0) 100 parts by weight was mixed with 5 parts by weight of azodicarbonamide as a foaming agent, and this was mixed with an extruder at 170 ° C. The mixture was melt-kneaded and extruded into a foamable sheet.

The foamable sheet was irradiated with an electron beam at a dose of 2.6 Mrad to crosslink the polyethylene resin. This crosslinked sheet was continuously passed through an oven at 250 ° C. to be heat-foamed to obtain a crosslinked polyethylene resin foam sheet having a thickness of about 1 mm. The obtained foamed sheet was flexible and had uniform and closed cells.

Regarding this foamed sheet, JIS K67
67, the apparent density, tensile strength and elongation were measured. Table 1 shows the results. Further, Table 1 shows the gel fraction, odor and solvent resistance. Solvent resistance is 2 in toluene at 30 ° C.
The appearance after immersion for 4 hours was visually determined.

Regarding the polyethylene resin (EXACT3027 manufactured by Exxon Chemical Co., Ltd.), a cross fractionation chromatograph (CFC-T1 manufactured by Mitsubishi Petrochemical Co., Ltd.) was used.
Cross-fractionation analysis result measured using a 50A type) and a differential scanning calorimeter (DSC) (SSC5 manufactured by Seiko Instruments Inc.)
Table 2 shows the results of DSC analysis measured using a 200 type).

Comparative Example 1 The procedure of Example 1 was repeated, except that the electron beam irradiation dose was changed to 0.8 Mrad, but it was difficult to obtain a foamed sheet because the degree of crosslinking was too low.

Comparative Example 2 The procedure of Example 1 was repeated except that the electron beam irradiation dose was changed to 5.5 Mrad, but it was difficult to obtain a foamed sheet because the degree of crosslinking was too high.

Comparative Example 3 Except that the amount of azodicarbonamide was changed to 1 part by weight,
A crosslinked polyethylene resin foam sheet having a thickness of about 0.5 mm was obtained in the same manner as in Example 1, but the apparent density was too high and the flexibility was poor.

Comparative Example 4 A crosslinked polyethylene resin foam sheet having a thickness of about 1.5 mm was obtained in the same manner as in Example 1 except that the amount of azodicarbonamide was changed to 35 parts by weight, but the apparent density was low. It was too low and the tensile strength was poor.

Comparative Example 5 Polyethylene resin obtained by using a metallocene compound as a polymerization catalyst (EXACT manufactured by Exxon Chemical Co.)
3027), an ethylene-vinyl acetate copolymer (SHOREX EL12-5 manufactured by Showa Denko KK, vinyl acetate content 15% by weight, density 0.932 g / c).
m ^3, a melt cum index is 2.0 g / 10 min) and 70 parts by weight, linear low density polyethylene (Tosoh Co. Niporon -L, F20, density 0.919 g / cm ^3, a melt cum index is 2. 0 g / 10 min) 30 parts by weight and 100 parts by weight of the mixture. Further, the irradiation dose of the electron beam was changed to 2.2 Mrad.

Otherwise in the same manner as in Example 1 to obtain a crosslinked polyethylene resin foam sheet having a thickness of about 1 mm.
The apparent density, tensile strength and elongation of this foamed sheet were measured in the same manner as in Example 1. Table 1 shows the results. Further, Table 1 shows the gel fraction, odor and solvent resistance.

[0047]

[Table 1]

[0048]

[Table 2]

[0049]

As described above, the pressure-sensitive adhesive tape substrate of the present invention is formed by crosslinking and foaming a polyethylene resin obtained by using a metallocene compound containing a tetravalent transition metal as a polymerization catalyst, and has an apparent density of 0.02-0.33g / c
m ^3, the gel fraction is from 12 to 70 wt% of crosslinked polyethylene resin foam, thereby uniformly foamed excellent flexibility and mechanical strength without odor, yet has excellent solvent resistance adhesive A tape substrate is obtained.

Claims (3)

[Claims] 1. A polyethylene resin obtained by using a metallocene compound containing a tetravalent transition metal as a polymerization catalyst is crosslinked and foamed, and has an apparent density of 0.02 to 0.
An adhesive tape substrate made of a crosslinked polyethylene resin foam having a gel fraction of 33 g / cm ³ and a gel fraction of 12 to 70% by weight. 2. The polyethylene resin has one crystal melting peak measured by using a differential scanning calorimeter (DSC), and the temperature range from melting peak temperature to the end of melting of all crystals is within 20 ° C. The adhesive tape substrate according to claim 1, which is 3. The temperature of 100% by weight from the temperature when the polyethylene resin is eluted by 10% by weight by the cross fractionation method.
The pressure-sensitive adhesive tape substrate according to claim 1, wherein the temperature range at the time of completion of elution is 30 ° C. or less, and the weight average molecular weight / number average molecular weight value is 1.5 to 3.5.