JPH09137011A - Resin composition and film comprising the composition - Google Patents

Abstract

(57) Abstract: [PROBLEMS] To obtain a resin composition exhibiting excellent rubber elasticity and extension recovery at a temperature of about body temperature. SOLUTION: The value of weight average molecular weight / number average molecular weight is 1.5 to 3.0 and the density is 0.885 to 0.920.
It is in the range of g / cm ³ , the temperature range from the start of melting of all the crystals of the film to the end of melting when measured using a differential scanning calorimeter is within 20 ° C., and the single crystal melting peak is present. And a linear low-density polyethylene resin, a styrene-based thermoplastic resin elastomer, and an organic peroxide.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a resin composition which is excellent in flexibility and processability, and is also excellent in rubber elasticity, particularly in elongation recovery, and a film made of the composition.

[0002]

2. Description of the Related Art A resin composition excellent in flexibility, processability and rubber elasticity is disclosed in Japanese Patent Laid-Open No. 270746/1992.
A resin composition obtained by partially cross-linking a composition composed of a styrene elastomer having rubber elasticity, an ethylene-vinyl acetate copolymer, and an organic peroxide is disclosed.

These resin compositions are used as a rubber elastic body in the form of a film in the gather portion of sanitary materials such as disposable diapers.

[0004]

However, the above-mentioned conventional resin compositions have the drawback of being inferior in heat resistance. Therefore, when used as a gather for sanitary materials or the like and kept in a tension state under a temperature of about body temperature for a long time, the stretch recovery property is lost, and there is a problem that the effect as a gather is remarkably reduced. .

The object of the present invention is to obtain a body temperature of about
It is an object of the present invention to provide a resin composition capable of exhibiting excellent rubber elasticity and extension recovery and a film made of the composition.

[0006]

The resin composition of the present invention comprises:
The value of weight average molecular weight / number average molecular weight (Mw / Mn) is 1.5 to 3.0, and the density is 0.885 to 0.920.
is in the range of g / cm ³ , and the temperature range from the start of melting of all the crystals of the film to the end of melting when measured using a differential scanning calorimeter (DSC) is within 20 ° C.,
Further, it is characterized by being composed of a linear low-density polyethylene (LLDPE) having a single crystal melting peak, a styrene thermoplastic resin elastomer, and an organic peroxide.

The linear low-density polyethylene resin used in the present invention has a weight average molecular weight / number average molecular weight value within the range of 1.5 to 3.0. When this value is less than 1.5, the film moldability is lowered, and this value is 3.
If it exceeds 0, the heat resistance decreases. The density is 0.88
When the density is in the range of 5 to 0.920 g / cm ³ , and the density is lower than this range, the heat resistance is lowered, and when the density is higher than this range, rubber elasticity is lost.

Further, the linear low-density polyethylene resin used in the present invention has a temperature range within 20 ° C. from the start of melting of all the crystals of the film to the end of melting as measured by DSC, and It shows one crystal melting peak. If the temperature range from the start of melting of all the crystals of the film to the end of melting is greater than 20 ° C,
The heat resistance decreases, and the crystal melting peak is not single,
When there are a plurality of these, the elongation recovery property decreases.

The linear low-density polyethylene resin used in the present invention can be obtained, for example, by polymerizing using a metallocene compound containing a tetravalent transition metal as a polymerization catalyst.

Examples of the tetravalent transition metal include titanium, zirconium, nickel, palladium, hafnium and platinum. Compounds in which one or more cyclopentadienyl rings and their analogs exist as ligands in these tetravalent transition metals are generally called metallocene compounds.

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, Examples thereof include an indenyl ring and an indenyl ring substituted with a hydrocarbon group, a substituted hydrocarbon group or a hydrocarbon-substituted metalloid group, and these ligands are present in one or more. Other ligands include
Examples thereof include monovalent anion ligands such as chlorine and bromine or divalent anion chelate ligands, hydrocarbons, alkoxides, arylalkoxides, aryloxides, amides, arylamides, phosphides, arylphosphides and the like.

Typical of the above hydrocarbon groups are methyl, ethyl, propyl, butyl, amyl, isoamyl,
Hexyl, isobutyl, heptyl, octyl, nonyl,
Decyl, cetyl, 2-ethylhexyl and phenyl.

The metallocene compounds coordinated with these ligands include cyclopentadienyl titanium tris (dimethylamide), methylcyclopentadienyl titanium tris (dimethylamide), bis (cyclopentadienyl) titanium dichloride, dimethylsilyltetra Methylcyclopentadienyl-tert-butylamide zirconium dichloride, dimethylsilyltetramethylcyclopentadienyl-tert-butylamide hafnium dichloride, dimethylsilyltetramethylcyclopentadienyl-pn-butylphenylamide zirconium chloride, methylphenyl Silyltetramethylcyclopentadienyl-tert-butylamide hafnium dichloride, indenyl titanium tris (dimethylamide), indenyl Titanium tris (diethylamide), indenyl titanium tris (di -n- propyl amide), indenyl titanium bis (di -n- butylamide) (di -n- propyl amide) and the like.

Polymerization is usually carried out with these metallocene compounds,
The reaction is carried out in a catalyst system to which methylaluminoxane (MAO), a boron compound or the like is added as a cocatalyst. The use ratio of the cocatalyst to the metallocene compound is 10 to 1000
It is 000 mol times, usually 50 to 5000 mol times.

The polymerization conditions are not particularly limited, and a solution polymerization method using an inert medium, a bulk polymerization method in which substantially no inert medium is present, or a gas phase polymerization method can be used. Generally, the polymerization temperature is from -100 ° C to 300 ° C, and the polymerization pressure is from normal pressure to 100 kg / cm ² .

The polyolefins polymerized with these metallocene catalysts have a narrow molecular weight distribution, and in the case of copolymers, the copolymer components are introduced in almost equal proportions in every molecule. Commercially available products of such polyethylene resins include CGCT manufactured by Dow Chemical Co., Affinity,
Engage and EXACT manufactured by Exxon Chemical Co. are known.

Examples of the styrene-based thermoplastic resin elastomer used in the present invention include styrene-butadiene-
Styrene block copolymer, hydrogenated styrene-butadiene-styrene block copolymer, styrene-isoprene-
Examples thereof include a styrene block copolymer and a hydrogenated styrene-isoprene-styrene block copolymer.

In the present invention, the mixing ratio of the linear low-density polyethylene resin and the styrene-based thermoplastic resin elastomer is 80 to 20% by weight of the linear low-density polyethylene resin, and 20 to 20% of the styrene-based thermoplastic elastomer. 80
% By weight. If the amount of the linear low-density polyethylene resin is less than 20% by weight, the processability into a film tends to deteriorate, and if it exceeds 80% by weight, the flexibility and rubber elasticity tend to deteriorate.

In the present invention, examples of the organic peroxide used for partial crosslinking include benzoyl peroxide and t-
Butyl cumyl peroxide, α, α′-bis (t-butylperoxy-m-isopropyl) benzene, 2,5
-Dimethyl-2,5-di (t-butylperoxy) hexane, 2,5-dimethyl-2,5-di- (t-butylperoxy) hexyne-3,3,5,5-trimethylhexanoylper Oxide, lauroyl peroxide,
1,1-di-t-butyl peroxide, t-butyl benzoate, di-t-butyl peroxide and the like can be mentioned. These may be used alone or in combination.

The amount of the organic peroxide added is preferably 200 to 2000 ppm with respect to 100 parts by weight as the total of the linear low-density polyethylene resin and the styrene thermoplastic elastomer. If the added amount is less than 200 ppm, the rubber elasticity and workability are poor, and the added amount is 2000 pp.
When it exceeds m, the amount of gel increases and a good film cannot be obtained.

Therefore, in a preferred embodiment according to the present invention, the linear low density polyethylene resin is 80 to 20% by weight.
And styrene-based thermoplastic elastomer 20 to 80% by weight
And 200 to 100 parts by weight of the total of these resins.
It consists of 2000 ppm of organic peroxide.

The partial cross-linking with the organic peroxide is carried out by thoroughly mixing the linear low-density polyethylene resin, the styrene-based thermoplastic elastomer and the organic peroxide and then at a temperature equal to or higher than the decomposition temperature of the organic peroxide. It can be carried out by thoroughly kneading the resin with an extruder, a kneader, a Banbury mixer, a hot roll or the like. The partially crosslinked resin composition of the present invention can be easily formed into a film by a method such as inflation or T-die casting.

If desired, additives such as antioxidants, light stabilizers, antistatic agents, lubricants and antiblocking agents can be added to the resin composition of the present invention.

[0024]

INDUSTRIAL APPLICABILITY In the resin composition of the present invention, by combining a specific linear low-density polyethylene resin with a styrene-based thermoplastic resin elastomer and an organic peroxide, excellent flexibility and processability can be obtained. It is possible to obtain a resin composition which is excellent in rubber elasticity, particularly in extension recovery under a temperature of about body temperature.

Therefore, a film molded from such a resin composition is suitable as a rubber elastic body forming gathers in sanitary materials such as paper diapers.

[0026]

EXAMPLES The present invention will be described below with reference to specific examples, but the present invention is not limited to the following examples.

Example 1 Density 0.908 g / cm ³ , melting point 103 ° C., melt index 1.0 g / 10 min, Mw / Mn = 2.6,
LLDPE (manufactured by Dow Chemical Co., trade name “Affinity-PL1840”) having a temperature range of 15.7 ° C. from the start of melting of all crystals in DSC to the end of melting 5
0% by weight and hydrogenated styrene-butadiene-styrene block copolymer (manufactured by Shell Kagaku Co., Ltd. under the trade name "Clayton G"
1657 ") 50% by weight and 1, as an organic peroxide
1-Bis (t-butylperoxy) 3,3,5-trimethylcyclohexane (manufactured by Nippon Petrochemical Co., Ltd., trade name "Perhexa 3M") was added to 500 parts by weight of the above-mentioned resin blend to add 500 ppm. Then, this composition was extruded at 170 ° C. using a twin-screw extruder to obtain a partially crosslinked resin composition. The partially crosslinked resin composition thus obtained was molded into a film having a thickness of 30 μm using a T-die cast molding machine.

About the obtained film, 20 ° C. and 4
The residual strain at 0 ° C. was measured. The residual strain measurement is
The film is stretched to the specified stretch ratio and 2 for each temperature.
After holding for 4 hours, the residual strain when relaxed was measured. Table 1 shows the measurement results.

Comparative Example Instead of the LLDPE of Example 1 above, the vinyl acetate content was 10% by weight and the melt index was 10 g / 10 min.
Using the ethylene-vinyl acetate copolymer (trade name "Ultrasen 541" manufactured by Tosoh Corp.) of No. 3), a 30 μm film was molded with the same compounding amount and the same manufacturing method as in Example 1 above. The residual strain of the obtained film was measured in the same manner as in Example 1 above, and the measurement results are shown in Table 1.

[0030]

[Table 1]

As is clear from the results of Table 1, the resin composition of Example 1 according to the present invention has a small residual strain at temperatures of 20 ° C. and 40 ° C. and is excellent in elongation recovery. Recognize.

Claims (3)

[Claims] 1. The weight average molecular weight / number average molecular weight value is 1.5 to 3.0 and the density is 0.885 to 0.920.
It is in the range of g / cm ³ , the temperature range from the start of melting of all the crystals of the film to the end of melting when measured using a differential scanning calorimeter is within 20 ° C., and the single crystal melting peak is present. Which is a linear low-density polyethylene resin, a styrene-based thermoplastic resin elastomer, and an organic peroxide. 2. The linear low-density polyethylene resin,
The resin composition according to claim 1, which is obtained by using a metallocene compound as a polymerization catalyst. 3. A film formed by using the resin composition according to claim 1.