JPH0859981A - Moisture-permeable urethane-based elastomer film - Google Patents

Abstract

PURPOSE: To prepare a urethane-based elastomer film, having good moisture permeability and waterproofness, improved in moldability through increasing its melt-tension and its blocking resistance, etc., in particular, surpassing the level of a moisture permeability of >=2000g/m<2> .24hrs. and that of a water resistance of >=1000mmH2 O considered as the respective targets in the diaper field, by using a polyether-based thermoplastic polyurethane excellent in mechanical strength and stretchability. CONSTITUTION: This elastomer film is prepared by film-formation of a thermoplastic elastomer composition obtained by blending 5-40 pts.wt. of a filler with 100 pts.wt. of a polyurethane-based resin composition comprising 75-95wt.% of a thermoplastic polyurethane resin with the soft segments consisting of a polyether and 5-25wt.% of an ethylene-propylene-diene copolymer rubber.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a urethane elastomer film, and more particularly, it has moisture permeability and waterproofness in the fields of sanitary materials such as gathers and back sheets of diapers, and clothing such as coats. The present invention relates to a urethane-based elastomer film which can be effectively used in a required field.

[0002]

2. Description of the Related Art As a conventional method for producing a moisture-permeable urethane film, a polyether-based thermoplastic polyurethane is used, and a polyurethane coating is carried out by using a continuous coating apparatus as described in JP-A-62-290714. A method in which the combined solvent solution is applied to release paper, and then the solvent is dried by passing through a drying oven, and then the formed film is not peeled from the release paper or is peeled off and wound onto a take-up roll. There is. However, a method of applying a solvent solution of the polyurethane polymer to release paper and drying the solvent to obtain a urethane film requires recovery of the solvent, a drying step, and the like, which leads to high costs and problems in productivity. is there.

Further, since the thermoplastic polyurethane elastomer has high tackiness, is easy to block, and has a low melt tension, it is difficult to form a film by a casting method or an inflation method by itself, so that the thermoplastic polyurethane is used. It has been proposed to improve the processability by mixing a resin having a high melt tension and a low temperature dependence or a resin that improves the blocking property. However, the film obtained by increasing the amount of such resin added has improved moldability, but impairs the original moisture permeability of the urethane resin, and there is still room for improvement in blocking resistance. I have left.

[0004]

SUMMARY OF THE INVENTION The present invention solves the drawbacks of the prior art and improves the moldability by improving the melt tension, blocking, etc. and uses a polyether-based thermoplastic polyurethane for moisture permeability. , A urethane-based elastomer film that is highly waterproof, with the aim of providing a urethane-based elastomer film that also has excellent mechanical strength, and in particular has a water vapor transmission rate of 2000 g / m ² · 24 hrs or more, which is an index in the diaper field. , Water resistance 10
It is an object of the present invention to provide a urethane-based elastomer film having a stretchability of more than 00 mmH ₂ O and having a high level of elasticity.

[0005]

The present invention has been studied in view of the above objects, and as a result, a specific amount of a thermoplastic thermoplastic polyurethane resin is blended with a resin having a high melt tension and a low temperature dependence and a filler. This completes the present invention. That is, (a) 75-95% by weight of a thermoplastic polyurethane resin whose soft segment is composed of polyether.
(B) Ethylene-propylene-diene copolymer rubber 5 to
A moisture-permeable urethane which is formed by film-forming a thermoplastic elastomer composition obtained by adding (c) 5 to 40 parts by weight of filler to 100 parts by weight of a polyurethane resin composition consisting of 25% by weight. System elastomer film.

The present invention will be described in detail below. Examples of the (a) thermoplastic polyurethane resin in the present invention include:
A polyether polyurethane elastomer whose soft segment is polyether is used. The thermoplastic polyurethane resin is an addition polymer of a long-chain glycol, a short-chain glycol, and a diisocyanate. The thermoplastic polyurethane resin in which the soft segment is composed of polyether is polytetramethylene glycol (PTMG) as a long-chain glycol, Polyethylene glycol (PE
G), polyether compounds such as polypropylene glycol (PPG), ethylene glycol, 1,4-butanediol, 1,4-hexanediol as the short-chain glycol, and tolylene diisocyanate, 4,4′-as the diisocyanate. It can be obtained by addition polymerization using diphenylmethane diisocyanate, hexamethylene diisocyanate or the like.

The (b) ethylene-propylene-diene copolymer used in the present invention is a copolymer containing ethylene, propylene and a diene compound. Examples of the diene compound include ethylidene norbornene, 1,
4-hexadiene, dicyclopentadiene and the like.
The ethylene-propylene-diene copolymer rubber (EP
The DM) preferably has a propylene content of 10 to 80% by weight. More preferably, it is 15 to 70% by weight. The number average molecular weight of the ethylene-propylene-diene copolymer is preferably 400,000 to 600,000, and the density is 0.87.
It is preferably g / cm ³ or less. Furthermore, the melt index (190 ° C., 2.16 kg load) is 0.1
It is preferably in the range of ˜12.0 g / 10 minutes, more preferably 0.1 to 5.0 g / 10 minutes.

The blending ratio of each component in the polyurethane resin composition used in the present invention is as follows: (a) 75 to 95% by weight of a thermoplastic polyurethane resin in which the soft segment is composed of polyether, (b) ethylene-propylene- The diene copolymer rubber is 5 to 25% by weight. When the content of the thermoplastic polyurethane resin (a) in which the soft segment is composed of polyether is less than 75% by weight, the properties of the polyurethane elastomer are lost, the moisture permeability is deteriorated, and the properties of the polyurethane such as abrasion resistance and mechanical strength are deteriorated. descend. On the other hand, if it exceeds 95% by weight, the inflation tube is likely to be blocked, and it becomes difficult to peel it off into two pieces after slitting both ears. Further, since the urethane resin has a high temperature dependency on the melt property, the bubbles are unstable and it becomes difficult to form a film by the inflation method. (B) If the ethylene-propylene-diene copolymer rubber is less than 5% by weight, the inflation tube tends to be blocked,
It becomes difficult to peel it into two pieces after slitting both ears, and the stability in film formation of the film becomes insufficient. On the other hand, if it exceeds 25% by weight, the flexibility of stretching is maintained, but the moisture permeability of the product is significantly lowered.

In the above polyurethane resin composition, by blending a low density polyethylene resin,
The moldability can be improved by further improving the melt tension and blocking. As the low-density polyethylene-based resin, a homopolymer of ethylene by a high-pressure method, linear low-density polyethylene or 20% by weight containing ethylene as a main component
The following copolymers with vinyl compounds and the like, for example, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer and the like can be mentioned. The density of the low density polyethylene resin is preferably 0.935 g / cm ³ or less,
Also, melt index (MI, 190 ° C, load 2, 1
6 kg) is preferably 0.05 to 20 g / 10 minutes. When blending low density polyethylene resin, (b)
It is preferably up to 40% by weight of the ethylene-propylene-diene copolymer rubber. If the blending ratio of the low-density polyethylene-based resin is 40% by weight or more, the moisture permeability of the product will be impaired, and the flexibility of stretching will be insufficient.

A filler (c) is added to the thermoplastic elastomer composition of the present invention. Examples of the filler (c) include talc, calcium carbonate, gypsum, carbon black, clay, kaolin, silica, diatomaceous earth, magnesium carbonate, barium carbonate, magnesium sulfate, barium sulfate, calcium sulfate, calcium phosphate, and aluminum hydroxide. , Zinc oxide, magnesium hydroxide, calcium oxide, magnesium oxide, titanium oxide, alumina,
Mica, silas balun, zeolite, silicate clay, cement, silica fume, mica powder, nylon powder and the like having an anti-blocking effect can be used, but talc, titanium oxide, calcium carbonate, silica and the like are particularly preferable. preferable. These fillers can be used alone or in combination. The filler may be surface-treated. The amount of the filler added is 5 to 40 parts by weight based on 100 parts by weight of the polyurethane resin composition. When the amount of the filler added is less than 5 parts by weight, the physical property balance in the MD / TD direction of the film is good, but the blocking resistance is not improved. If it exceeds 40 parts by weight, blocking resistance is improved, but strength is increased and flexibility is impaired.

If necessary, an antioxidant, an ultraviolet absorber, a colorant and the like can be added to the above thermoplastic elastomer composition.

In the present invention, the thermoplastic elastomer composition is melt-kneaded by using a twin-screw extruder or the like to form a film. The method for producing a film from the composition,
Although it can be usually formed into a flat film by a T-die extruder, which is a known method for forming a polyolefin film, an air-cooled inflation method of forming a tube-shaped film by an inflation method is preferable. In the air-cooled inflation method, it is possible to stabilize the bubbles required for thinning and high-speed molding, and to reduce the blocking property without deteriorating the characteristics of the thermoplastic polyurethane resin. In the inflation molding method using the air-cooling method, in order to stabilize the bubbles necessary for thinning the film and speeding up the molding, and to reduce the blocking property without deteriorating the characteristics of the thermoplastic polyurethane resin, a resin temperature of 180 to Two
It is preferable to carry out at 20 ° C. and a blow ratio of 2.0 to 5.0. The matters disclosed in JP-A-3-128945 can be applied to such a film manufacturing method. The thickness of the film is appropriately selected according to various uses, but it stabilizes the bubbles required for thinning and high-speed molding,
In order to reduce the blocking property without deteriorating the characteristics such as moisture permeability of the thermoplastic polyurethane resin, it is usually preferable to mold the thermoplastic polyurethane resin in the range of about 25 to 40 μm.

[0013]

EXAMPLES Next, examples of the present invention will be shown. The test methods in Examples and Comparative Examples are as follows. (1) Water vapor transmission rate; conforms to JIS Z0208. (2) Water resistance: According to JIS L1092. (3) Strength at break: According to JIS L1096. (4) Elongation at break: According to JIS L1096. (5) 50% 2-cycle strain; conforming to JIS L1096. (6) Film-forming property: ◎ ... Bubbles are stable and do not block at all, ○ ... Bubbles are stable and do not block, Δ ... Bubbles are unstable and block, X
... No film formation.

Examples 1-3. Thermoplastic polyurethane resin whose soft segment is composed of polyether (trade name: Rezamin P-210 manufactured by Dainichiseika Kogyo Co., Ltd.) and ethylene-propylene-diene copolymer (number average molecular weight 450,000, density 0.87 g / cm ³ , MI = 0.1 g / 10 min, propylene content 27 wt%) and high-pressure low-density polyethylene (density 0.935 g / cm ³ , MI = 0.8 g / 1
The composition obtained by adding 30 parts by weight of stearic acid-treated calcium carbonate (average particle size 2 μm) to 100 parts by weight of the composition having the compounding ratio shown in Table 1 is 180 minutes.
The film was melt-kneaded with a biaxial kneader at 0 ° C., and films having a thickness of 30 μm, a thickness of 40 μm and a thickness of 30 μm were formed into films by the air-cooled inflation method under the following conditions, to give Examples 1, 2 and 3, respectively. Die diameter: 150 mm, Blow ratio: 3.5, Cylinder temperature of extruder: 190 ° C Resin temperature at die outlet: 195 ° C, Resin pressure at die outlet: 200 kg / cm ² , extrusion rate ... 35-45 kg / hr, take-up speed ... 10 m / min,

Regarding the obtained elastomer film,
Moisture vapor transmission rate, water resistance, strength at break, elongation at break, and 50
% 2 cycle strain was measured. The results are shown in Table 1.

Comparative Example 1. 50 wt% of the thermoplastic polyurethane resin whose soft segment used in Examples 1 to 3 is polyether, 30 wt% of ethylene-propylene-diene copolymer, and 20 wt% of high-pressure low-density polyethylene.
% In the same manner as in Example 1.
The film was melted and kneaded by a biaxial kneader at ℃, and a film was formed by an air-cooled inflation method. The film-forming property and the mechanical properties are good, but the moisture permeability is impaired because the amount of the thermoplastic polyurethane resin is small.

Comparative Example 2. A film was formed in the same manner as in Example 1 except that the stearic acid-treated calcium carbonate was not added and the film thickness was changed to 60 μm. During film formation, the film was inflated by an air-cooled inflation method and then pressed with a nip roll to fold the tube and then trimmed both ears to divide it into two pieces, but they were blocked and did not come off. The measured values of the water vapor transmission rate and the water resistance in Table 1 are the values for the two-layer stack. Moreover, it was found that it was difficult to feed the film from the winder after the film formation. Other mechanical properties could not be measured.

Comparative Example 3. An attempt was made to form a film in the same manner as in Example 1 except that the ethylene-propylene-diene copolymer was not blended, but the melt tension was low and film formation was impossible.

[0019]

[Table 1]

[0020]

As described above, according to the present invention, the melt tension is improved,
A urethane elastomer film that has improved mechanical properties due to improved blocking properties, and uses a thermoplastic thermoplastic polyurethane based on an inflation method with low cost and high productivity, which has excellent moisture permeability and waterproof properties as well as excellent mechanical strength. Can be provided. In particular, it has cleared the water vapor permeability of 2000 g / m ² · 24 hrs or more and the water resistance of 1000 mmH ₂ O or more, which are indicators in the diaper field,
It was possible to provide a urethane-based elastomer film having excellent stretchability.

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Claims (3)

[Claims] 1. A thermoplastic polyurethane resin comprising: (a) a soft segment composed of polyether;
(B) Ethylene-propylene-diene copolymer rubber 5 to
A moisture-permeable urethane which is formed by film-forming a thermoplastic elastomer composition obtained by adding (c) 5 to 40 parts by weight of filler to 100 parts by weight of a polyurethane resin composition consisting of 25% by weight. Type elastomer film. 2. The moisture-permeable urethane elastomer film according to claim 1, wherein the polyurethane resin composition contains a low density polyethylene resin. 3. The moisture-permeable urethane elastomer film according to claim 1, wherein the film is formed by an inflation method.