JPH11116720A - Crosslinked ethylene resin foam and medical tape base material comprising the foam - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a crosslinked ethylene resin foam having uniform and fine closed cells, excellent flexibility, stretchability and mechanical strength, and being odorless. Further, the present invention provides a medical tape base material having a small thickness, excellent physical properties and followability to the skin, and having good touch. SOLUTION: The density obtained by using a metallocene compound containing a tetravalent transition metal as a polymerization catalyst, is 0.840 to less.
A crosslinked ethylene-based resin foam comprising 0.890 g / cc of an ethylene-based resin, and a medical tape base comprising the foam.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a crosslinked ethylene resin foam and a medical tape base comprising the foam.

[0002]

2. Description of the Related Art Conventionally, there has been a demand for a crosslinked foam having uniform and fine closed cells, having excellent flexibility, elasticity and mechanical strength, and being chemically stable. For a medical tape base material such as a surgical tape to be adhered to a medical device, there is a demand for a material having a small thickness, excellent physical properties and followability to the skin, and good touch.

As a method for obtaining the above-mentioned crosslinked foam, there is known a method of blending ethylene-vinyl acetate with an olefin resin which is a chemically stable resin to form a crosslinked foam. For example, Japanese Patent Publication No. 2-33387 discloses a medical tape base material obtained by crosslinking and foaming a linear low-density polyethylene and an ethylene-vinyl acetate copolymer.

However, in the above-mentioned method, although an ethylene-vinyl acetate copolymer is used, an odor of vinyl acetate remains, albeit very slight, and the ethylene-vinyl acetate copolymer is used for further improving flexibility. When the blending amount of the polymer is increased, there is a problem that the mechanical strength is reduced.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a crosslinked ethylene resin foam which has uniform fine cells, is excellent in flexibility, stretchability and mechanical strength, and is odorless. It is in. Another object of the present invention is to provide a medical tape base material which has a small thickness, is excellent in the above physical properties and skin followability, and has a good touch.

[0006]

Means for Solving the Problems The crosslinked ethylene resin foam of the present invention is obtained by using a metallocene compound containing a tetravalent transition metal as a polymerization catalyst, and has a density of 0.840 to 0.85.
It is characterized by being composed of 0.890 g / cc ethylene resin.

The ethylene resin used in the present invention is polymerized by using a metallocene catalyst containing a tetravalent transition metal. For example, ethylene homopolymer, ethylene-α Linear low-density polyethylene or linear ultra-low-density polyethylene which is an olefin copolymer;
More than one species may be used in combination. Examples of the α-olefin include propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-heptene,
Octene and the like.

When the density of the ethylene-based resin decreases, the crystallinity decreases and the polymerization from the monomer becomes difficult, and when the density increases, the flexibility and stretchability of the obtained foam decrease. Limited to 0.890 g / cc,
Preferably it is 0.850-0.890 g / cc.

Generally, a metallocene compound is a compound having a structure in which a transition metal is sandwiched between π-electron unsaturated compounds.
In the present invention, a compound in which at least one cyclopentadienyl ring or its analog is present as a ligand (ligand) on a tetravalent transition metal such as titanium, zirconium, nickel, palladium, hafnium, and platinum is used.

As the ligand, other than the cyclopentadienyl ring, for example, a cyclopentadienyl oligomer ring, an indenyl ring, a cyclopentadienyl group substituted with a hydrocarbon group, a substituted hydrocarbon group or a hydrocarbon monosubstituted metalloid group. Examples include an enyl ring and an indenyl ring. Also,
In addition to the ligand of the π-electron unsaturated compound, for example, chlorine or bromine monovalent anion or divalent anion chelate, hydrocarbon group, alkoxide, arylalkoxide, aryloxide, amide, arylamide,
A phosphide, an aryl phosphide, or the like may be coordinated with the transition metal.

Examples of the hydrocarbon group substituted with the cyclopentadienyl ring and the indenyl ring include a methyl group, an ethyl group, a propyl group, a butyl group, an isobutyl group,
Examples thereof include an amyl group, an isoamyl group, a hexyl group, a 2-ethylhexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, a cetyl group, and a phenyl group.

Specific examples of such a metallocene compound include, for example, cyclopentadienyl titanium tris (dimethylamide), methylcyclopentadienyl titanium tris (dimethylamide), bis (cyclopentadienyl) titanium dichloride, dimethyl Silyltetramethylcyclopentadienyl-t-butylamidozirconium dichloride, dimethylsilyltetramethylcyclopentadienyl-t-butylamidohafnium dichloride, dimethylsilyltetramethylcyclopentadienyl-pn-butylphenylamidozirconium chloride, Methylphenylsilyltetramethylcyclopentadienyl-t-butylamidohafnium dichloride, indenyl titanium tris (dimethylamide), indenyl titanium tri (Diethylamide), indenyl titanium tris (di -n- propyl amide), indenyl titanium bis (di -n- butylamide) (di -n-
Propylamide) and the like.

The above-mentioned metallocene compound functions as a catalyst in the polymerization of an ethylene-based resin by changing the type of metal and the structure of the ligand and combining with a specific cocatalyst. In a system in which methylaluminoxane (MAO), a boron compound and the like are added as a cocatalyst. The use ratio of the cocatalyst to the metallocene compound is 10 to 1,000,000 mole times, preferably 50 to 5,000 mole times.

The polymerization conditions are not particularly limited, and for example, a solution polymerization method using an inert medium, a bulk polymerization method in which no inert medium is present, a gas phase polymerization method, and the like can be employed. Polymerization temperature is -100 ° C to 300 ° C, polymerization pressure is normal pressure to 100k
It is generally performed at g / cm ² .

The ethylene-based resin polymerized using the metallocene compound as described above has a narrow molecular weight distribution, and when the ethylene-based resin is a copolymer, the copolymerization components are introduced in substantially equal proportions. An example of an ethylene-based resin is Dow Chemical's product name “Engage”
Etc. are commercially available.

As a method for obtaining the crosslinked ethylene resin foam of the present invention from the above ethylene resin, any conventionally known method can be employed. As a general method, for example, a method by ionizing radiation crosslinking, peroxidation, A method by chemical crosslinking in which a radical generator such as a substance is thermally decomposed, a method by silane crosslinking, and the like are exemplified.

Hereinafter, a method by ionizing radiation crosslinking will be described in detail. In this method, in addition to a thermal decomposition type foaming agent, a crosslinking aid and the like are added as necessary to the ethylene resin, and a single screw extruder and a twin screw extruder are used at a temperature at which the thermal decomposition type foaming agent is not substantially decomposed. ,
After melt-kneading with a Banbury mixer, kneader mixer, calender roll, etc., it is extruded into a foamable sheet, and cross-linked by irradiating ionizing radiation from one or both sides of the foamable sheet, hot air heater, salt bath, metal bath, etc. The foaming is carried out by heating the foaming temperature to the foaming temperature of the pyrolytic foaming agent or higher by the method of (1) to obtain a crosslinked ethylene resin foam. The foaming temperature is a temperature at which the foaming agent is decomposed to generate gas or a temperature at which the foaming agent is gasified.

The above-mentioned pyrolytic foaming agent is one that generates a decomposed gas by heating or gasifies by heating. For example, azodicarbonamide, benzenesulfonylhydrazide, N, N-dinitrosopentamethylenetetramine, toluene Sulfonyl hydrazide, 4,4-oxybis (benzenesulfonyl hydrazide) and the like may be mentioned, and these may be used alone or in combination of two or more. Among them, azodicarbonamide is preferred because the amount of generated gas, handling safety and the like are excellent. The amount of the pyrolytic foaming agent to be added is not particularly limited, and is appropriately determined depending on a desired expansion ratio.
The amount is preferably 1 to 25 parts by weight, more preferably 2 to 20 parts by weight with respect to parts by weight.

Examples of the crosslinking aid include polyfunctional monomers and monofunctional monomers generally used for foams.
For example, divinylbenzene, ethylvinylbenzene, divinylnaphthalene, trimethylolpropane trimethacrylate, 1,6-hexanediol dimethacrylate, 1,9-nonanediol dimethacrylate, 1,1
0-decanediol dimethacrylate, neopentyl glycol dimethacrylate, triallylic acid triallyl ester, triallyl isocyanurate, 1,2,4-
Benzyltricarboxylic acid triallyl ester, lauryl methacrylate, stearyl methacrylate and the like can be mentioned. If the amount of the crosslinking aid is too small, the desired degree of crosslinking cannot be obtained, and if it is too large, the degree of crosslinking becomes too large and the foaming property is reduced. -10 parts by weight is preferred.

When the degree of crosslinking of the ethylene-based resin is small, the resin cannot retain air bubbles during foaming, and a phenomenon called outgassing tends to occur. Since the foam of the foam to be obtained tends to be non-uniform, the content is preferably 3 to 70%, more preferably 1 to 70%.
It is 0 to 60%, more preferably 15 to 45%.

The degree of crosslinking referred to in the present invention is a value measured by the following method using the obtained foam. About 0.2 g of the obtained foam was precisely weighed in the thickness direction, immersed in 100 ml of xylene at 120 ° C. for 24 hours, and then filtered through a 200-mesh stainless steel wire mesh to dry insoluble matter on the wire mesh in vacuo. Then, the weight is precisely weighed, and the degree of crosslinking is calculated as a percentage by the following equation. Degree of crosslinking (%) = (weight of insoluble matter / weight of foam) × 1
00

Examples of the ionizing radiation include electron beams, X-rays, α-rays, β-rays, and γ-rays. When the irradiation amount of the ionizing radiation is too small, a desired degree of crosslinking cannot be obtained, and when it is too large, the degree of crosslinking becomes too large and the foaming property is reduced. Therefore, the irradiation amount is usually 1 to 50 Mrad.

In the crosslinked ethylene resin foam of the present invention, the mechanical strength decreases when the apparent density (expansion ratio) decreases, and the flexibility decreases when the apparent density increases.
It is preferably 0.500 g / cc, more preferably 0.050 to 0.200 g / cc.

The apparent density in the present invention is defined by JIS K
It is a value measured according to 6767.

The crosslinked ethylene resin foam of the present invention has excellent flexibility and elasticity, and thus has excellent adhesion.
Although it can be used as a joint material for glass and the like, it has excellent flexibility, elasticity and mechanical strength even when the thickness is reduced, so that it is suitably used as a medical tape base material.

When the crosslinked ethylene resin foam of the present invention is used as a medical tape base material, if the thickness is reduced, molding itself into the tape base material becomes difficult, and the crosslinked ethylene resin foam has uniform fine bubbles. Is difficult to obtain, and when it becomes thicker, the ability to follow the skin is reduced.
Usually, it is 0.3 to 4 mm.

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

[0028]

【Example】

(Example 1) A linear low-density polyethylene (Dow.TM.) obtained by using a tetravalent metallocene compound as a polymerization catalyst and copolymerized with 1-octene having a density of 0.870 g / cc.
Chemical company, product name "Engage EG8200") 1
00 parts by weight and azodicarbonamide (decomposition start temperature =
5 parts by weight are melt-kneaded in a twin-screw extruder at a temperature at which azodicarbonamide is not substantially decomposed, then extruded, molded into a sheet having a thickness of 0.6 mm, and 3 Mrad of electron is applied from both sides of the sheet. Cross-linking was performed by irradiating a line to obtain a cross-linked foamable sheet. Next, the crosslinked foamable sheet was heated at 250 ° C.
To form a crosslinked foam of the present invention. The thickness of the obtained crosslinked foam is 1 m
m, the degree of crosslinking and the apparent density are as shown in Table 1,
There was no smell.

Comparative Example 1 1 having a density of 0.910 g / cc and obtained using a metallocene compound as a polymerization catalyst
Octene copolymerized linear low-density polyethylene (trade name "Affinity PL18" manufactured by Dow Chemical Company)
45 ") A crosslinked foam was obtained from 100 parts by weight and 5 parts by weight of azodicarbonamide in the same manner as in Example 1. The thickness of the obtained crosslinked foam was 1 mm, the degree of crosslinking and the apparent density were as shown in Table 1, and there was no odor.

(Comparative Example 2) The density was 0.932 g / cc,
An ethylene-vinyl acetate copolymer having a vinyl acetate content of 15% by weight (trade name "SHOLEX EL" manufactured by Showa Denko KK)
12-5 ") 70 parts by weight, linear low-density polyethylene copolymerized with 1-hexene having a density of 0.919 g / cc (trade name" Nipolon-L, F20 "manufactured by Tosoh Corporation) 30
1 part by weight and 5 parts by weight of azodicarbonamide were prepared in Example 1.
A sheet having a thickness of 0.6 mm was formed in the same manner as described above, and cross-linking was performed by irradiating a 2.2 Mrad electron beam from both sides of the sheet to obtain a cross-linked foamable sheet. Next, the crosslinked foamable sheet was continuously passed through an oven heated to 250 ° C. and foamed to obtain a crosslinked foam. The thickness of the obtained crosslinked foam is 1
The mm, the degree of crosslinking, and the apparent density were as shown in Table 1, and a slight vinyl acetate odor remained.

(Measurement of Tensile Strength) Tensile strength of the obtained crosslinked foam was measured in the width direction and the length direction (the flow direction of the sheet when producing the foam) in accordance with JIS K6767. The values are shown in Table 1.

(Measurement of Elastic Deformation Area) For the obtained crosslinked foam, the tensile strength in the width direction and the length direction (the flow direction of the sheet when producing the foam) and the elongation at that time are represented by J.
It measured according to ISK6767 and obtained the stress-strain curve. Table 1 shows the elongation (%) of the stress-strain curve at the elastic limit.

[0033]

[Table 1]

[0034]

The crosslinked ethylene resin foam of the present invention is
Since it has the above-described configuration, it has uniform and fine closed cells, is excellent in flexibility, elasticity and mechanical strength, and has no odor of vinyl acetate and is odorless. Further, the medical tape substrate according to claim 2 has a small thickness, and
It has excellent physical properties and followability to skin, and has good touch.

Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI // C08F 4/64 A61L 15/06

Claims (2)

[Claims] 1. A density obtained by using a metallocene compound containing a tetravalent transition metal as a polymerization catalyst and having a density of 0.840 to
A crosslinked ethylene resin foam made of 0.890 g / cc ethylene resin. 2. A medical tape base comprising the crosslinked ethylene-based resin foam according to claim 1.