JPH07138470A - Thermoplastic polyurethane composition - Google Patents

Abstract

PURPOSE:To obtain the subject composition excellent in hot-melt adhesiveness, stretchability, the residual strain after small stretching/contraction, useful for e.g. various gathers for paper diapers, comprising a polyurethane resin, specific diene copolymer, PE-based resin and both of modified and unmodified styrene- based elastomers. CONSTITUTION:This polyurethane composition comprises (A) 40-70 pts.wt. of a thermoplastic polyurethane resin such as a polyester-based urethane elastomer, (B) 10-25 pts.wt. of an ethylene-propylene-diene copolymer, (C) 10-25 pts.wt. of a low-density polyethylene resin, (D) 5-20 pts.wt. of an unsaturated carboxylic acid (derivative)-modified styrene-based elastomer <=30wt.% in styrene proportion and (E) 0-20 pts.wt. of an unmodified styrene-based elastomer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermoplastic polyurethane composition, and particularly to hot-melt laminating with a non-woven fabric,
The present invention relates to a thermoplastic polyurethane composition suitable for a polyurethane film that can be used for various gathers in disposable diapers.

[0002]

2. Description of the Related Art Waist gathers for baby diapers require a stretch function with low stress and a hot melt adhesive property at a high speed during manufacturing. Currently, foamed urethane foam, urethane film, etc. are used from the functional aspect. There is. Most of the examples of use are urethane foams, but there are problems with price and diaper productivity. Further, the conventional urethane film has a problem that the hysteresis curve at 30 to 100% elongation is stronger than that of the foamed urethane foam, the residual strain at 100% elongation is large, and the adhesiveness with the hot melt adhesive is poor. Therefore, there is a demand in the market for a low-priced film having a function equivalent to that of foamed foam.

[0003]

SUMMARY OF THE INVENTION In view of the above prior art, the present invention is excellent in hot melt adhesiveness at a high speed during manufacturing, is excellent in stretchability at low stress, and has a small residual stretch strain. Moreover, it aims at providing the technique which can have moderate strength.

[0004]

The present invention comprises (a) 40 to 70% by weight of thermoplastic polyurethane resin, (b) 10 to 25% by weight of ethylene-propylene-diene copolymer (c).
Low-density polyethylene-based resin 10 to 25% by weight (d) Styrene-based elastomer 5 modified with unsaturated carboxylic acid or its derivative and having a styrene content of 30% by weight or less
˜20% by weight and (e) powder-modified styrenic elastomer 0 to 20% by weight.

The present invention will be described in detail below. Examples of the (a) thermoplastic polyurethane resin in the present invention include:
Examples thereof include polyurethane elastomers obtained by polyaddition reaction of long-chain polyols, short-chain polyols, diisocyanates, etc., such as polyester-based, adipate-based, polyether-based, polycaprolactone-based, etc. as raw materials through urethane bonds in the molecule. Of these, polyester-based polyurethane elastomers are preferred for the purposes desired by the present invention. Here, examples of the long-chain polyol include polyethylene glycol and polypropylene glycol, examples of the short-chain polyol include ethylene glycol, 1,4-butanediol, and 1,4-hexanediol, and examples of the diisocyanate include: , Tolylene diisocyanate, 4,4′-diphenylmethane diisocyanate, hexamethylene diisocyanate and the like. It is desirable that such a thermoplastic polyurethane elastomer has a softening temperature of 170 to 190 ° C. and a Shore A hardness (JIS A hardness) of 70 to 88. If the softening temperature is less than 170 ° C., the inflation tube is likely to be blocked during film formation, and it will be difficult to separate the two tubes after slitting both ears. On the other hand, if the softening temperature exceeds 190 ° C., the stretch flexibility and hot melt adhesiveness of the film will be poor. If the Shore A hardness is less than 70, the inflation tube is likely to be blocked during film formation, making it difficult to peel it off into two sheets after slitting both ears. On the other hand, if the Shore A hardness is more than 88, the stretch flexibility and hot melt adhesiveness of the film will be poor.

The ethylene-propylene-diene copolymer (b) 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 (EPD
M) preferably has an ethylene content of 60 to 70 mol%, a propylene content of 30 to 40 mol%, and a diene compound content of 1 to 10 mol%. A more preferable range is 62 to 66 mol% for ethylene, 33 to 37 mol% for propylene, and 3 to 6 mol% for a diene compound. The number average molecular weight of the ethylene-propylene-diene copolymer is preferably 400,000 to 600,000, and the density is preferably 0.87 g / cm ³ or less. Furthermore, the ethylene-propylene-diene copolymer has a melt index (190 ° C, 2.16 kg load) of 0.1 to 1
It is preferably in the range of 2.0 g / 10 minutes, more preferably 0.3 to 5.0 g / 10 minutes.

The low-density polyethylene-based resin (c) used in the present invention is a homopolymer of ethylene by a high-pressure method or a copolymer with ethylene as a main component and 20% by weight or less of a vinyl-based compound, such as ethylene- Examples thereof include vinyl acetate copolymers and ethylene-ethyl acrylate copolymers. It may be linear low density polyethylene. The density of the low density polyethylene resin is 0.93.
5 g / cm ³ or less is preferable, and the melt index (MI, 190 ° C., load 2,16 kg) is 0.0.
It is preferably 5 to 20 g / 10 minutes.

The styrene-based elastomer (d) modified with the unsaturated carboxylic acid or its derivative and having a styrene content of 30% by weight or less used in the present invention is, for example, a styrene-based elastomer containing an unsaturated carboxylic acid or its derivative. It can be obtained by subjecting a derivative to an addition reaction. As the styrene-based elastomer, a styrene-butadiene block copolymer comprising a polymer block mainly containing styrene and a polymer block mainly containing butadiene or isoprene, or a block copolymer of styrene-isoprene or the block copolymer An elastomer obtained by hydrogenating the coalescence can be mentioned. Specific examples thereof include styrene-butadiene-styrene block copolymer (SBS), styrene-ethylene-butene-styrene block copolymer (SEBS), styrene-isoprene-styrene block copolymer (SIS), styrene-ethylene. -Propylene-styrene butadiene block copolymer (SEPS) etc. are mentioned. Among these, hydrogenated products are preferable from the viewpoint of coloring and stability of physical properties. As the styrene elastomer, one having a styrene ratio of 30% or less is used. For example,
By hydrogenating the styrene-butadiene-styrene block copolymer, styrene-ethylene-butene-
A styrene block copolymer (SEBS) is used, but a styrene (S) and ethylene (E) -butene (B) blending ratio S / EB having a styrene ratio of 30% or less is used. Others are the same. When the ratio of the styrene exceeds 30%, the obtained film is hard,
The distortion increases. Examples of the unsaturated carboxylic acid or its derivative include maleic acid, fumaric acid, itaconic acid, acrylic acid, crotonic acid, endo-bi-cyclo-
Examples include [2,2,1] -5-heptene-2,3-dicarboxylic acid, cis-4-cyclohexene 1,2-dicarboxylic acid and their anhydrides and imidized products.
Preference is given to using maleic anhydride. The amount of addition of the unsaturated carboxylic acid or its derivative is 0.01 to 1
0% by weight is preferred.

As the (e) powder-modified styrene-based elastomer used in the present invention, the above-mentioned styrene-based elastomer can be used. Even in the powder-modified styrene-based elastomer, the (d) unsaturated carboxylic acid or It is preferable that the ratio of styrene is 30% by weight or less as in the case of the styrene elastomer modified with the derivative for the same reason.

The blending ratio of each component in the composition used in the present invention is (a) thermoplastic polyurethane resin 40 to
70% by weight, (b) ethylene-propylene-diene copolymer 10 to 25% by weight (c) low density polyethylene resin 10 to 25% by weight (d) of styrene modified with unsaturated carboxylic acid or its derivative The ratio is 5 to 20% by weight of styrene-based elastomer and 30 to 20% by weight of (e) powder-modified styrene-based elastomer.

The above-mentioned (a) thermoplastic polyurethane resin is 4
When it is less than 0% by weight, the properties of the polyurethane elastomer are lost, the stretch flexibility is deteriorated, and the properties of polyurethane such as abrasion resistance, heat resistance and mechanical strength are deteriorated. On the other hand, when it exceeds 70% by weight, the hot melt adhesiveness at high speed becomes poor. In addition, the inflation tube is easily blocked, and it becomes difficult to peel it off into two sheets after slitting both ears.

When the content of the ethylene-propylene-diene copolymer (b) is less than 10% by weight, the stability of film formation becomes insufficient. On the other hand, if it exceeds 25% by weight, the elasticity of the product, hot melt adhesiveness, rubber elasticity (10
The hysteresis strain after 0% expansion / contraction is large) and the like.

If the blending ratio of the low density polyethylene resin (c) is less than 10% 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. On the other hand, when the content is 25% by weight or more, the elasticity of the product, hot melt adhesiveness, rubber elasticity (100%
The hysteresis strain after expansion and contraction is large) and so on.

(D) If the compounding ratio of the styrene elastomer modified with an unsaturated carboxylic acid or its derivative and having a styrene ratio of 30% by weight or less is less than 5% by weight, the hot melt adhesiveness is poor, and Film formation becomes difficult. On the other hand, if it exceeds 20% by weight,
Discoloration and mechanical strength decrease.

(E) The powder-modified styrenic elastomer is
Although it is an optional component in 0 to 20% by weight, the addition thereof causes
The hot melt adhesiveness can be improved. However, 20% by weight
If it exceeds, the film-forming property and mechanical strength of the film will deteriorate.

In the composition of the present invention, an antioxidant, an ultraviolet absorber, a colorant, an inorganic filler and the like can be appropriately blended in addition to the above components.

The composition is prepared by adding the above-mentioned constituents and, if necessary, other components, and preliminarily dry blending using, for example, a Henschel mixer or a high speed mixer.
It can be obtained by melt-kneading and extruding into pellets under heating at, for example, about 180 to 220 ° C. using an extruder or the like. The method for producing a film from the composition can be formed as a flat film by a T-die extruder, which is a known method for forming a polyolefin film, and the film has a longitudinal and lateral strength balance and a thin film. Considering high-speed moldability (improvement in productivity) and the like, the air-cooled inflation method of molding as a tube-shaped film by the inflation method is preferable. In the inflation molding method using the air cooling method, the resin temperature is 180
It is preferable to carry out at a blow ratio of 2.0 to 5.0 at ˜220 ° C. The thickness of the film is appropriately selected according to various uses, but it is usually preferable to mold the film with a thickness of 100 μm or less. If the film thickness exceeds 100 μm, the film becomes hard. In the above film forming, a film is prepared by an air-cooled inflation film forming apparatus and slit into a predetermined width to obtain a rolled product. You may go through a stretching process.

[0018]

EXAMPLES The present invention will be described in more detail with reference to Examples and Comparative Examples. The test methods in Examples and Comparative Examples are as follows. In addition, each measured value is shown in the MD (longitudinal) direction of the film. (1) Strength at 50% elongation; conforming to JIS L1096. (2) Strength at 100% elongation; conforms to JIS L1096. (3) Strength at break: According to JIS L1096. (4) Elongation at break: According to JIS L1096. (5) One cycle strain after 100% elongation; JIS L1
According to 096. (6) Hot melt adhesiveness: In-house method. Horizontal 40 mm x Vertical 1
On top of a 20 mm acrylic plate, 30 mm x 30 mm hot melt adhesive (a hot melt adhesive applied to both sides of release paper in a sheet shape with a thickness of 5 μm) was pasted, a sample was placed, and a 230 g load rubber roll was used. Press lightly. Sample width: 30 mm x 150 mm, chuck interval: 100 mm, pulling speed: 300 mm / mi
n, atmosphere temperature: under a temperature of 23 ° C., a 180 ° peel test is performed using Strograph W manufactured by Toyo Seiki.

Example 1. Ester-based thermoplastic polyurethane (hereinafter sometimes referred to as PU. Grade P327 manufactured by Dainichiseika Kogyo KK, Shore hardness; 85 degrees, softening temperature;
187 ° C.) 50 wt% and ethylene-propylene-diene copolymer (hereinafter also referred to as EPDM. Exxon Chemical Co., Ltd. trade name Vistalon V3708) 15 wt% and high-pressure low-density polyethylene (hereinafter also referred to as LDPE. Unicar Grade NUC-850
6. Hydrogenated product of styrene-butadiene-styrene block copolymer modified with maleic anhydride and having a density of 15 wt% of 0.923 g / cm ³ (hereinafter also referred to as modified SEBS. Asahi Kasei Corp., trade name Tuftec M19
13. A kneading resin composed of a thermoplastic elastomer composition containing 13, S / EB ratio 30/70) 20 wt% was formed into a film having a thickness of 35 μm and a folding width of 820 mm (blow-up ratio: 3.5 by using an air-cooled inflation film forming apparatus. ) Was prepared, and both ears were slitted to obtain a sample wound into a sheet, and the physical properties of the sample were examined according to the above-mentioned test methods. The results are shown in Table 1.

Example 2. In the same manner as in Example 1 except that 54 wt% of the ester-based thermoplastic polyurethane, 18 wt% of the ethylene-propylene-diene copolymer, 18 wt% of the high-pressure low-density polyethylene, and 10 wt% of the modified SEBS were used. The kneaded resin composed of the thermoplastic elastomer composition was formed into a film in the same manner as above using an air-cooled inflation film forming apparatus to obtain a sample, and the physical properties of the sample were examined according to the above-mentioned test methods. The results are shown in Table 1.

Example 3. In Example 1, 55 wt% of the ester-based thermoplastic polyurethane, 15 wt% of the ethylene-propylene-diene copolymer, 15 wt% of the high-pressure low-density polyethylene, and the modified SEBS having a S / EB ratio of 20/80 were used. Asahi Kasei Co., Ltd., trade name Tough Tech M1943), and its compounding amount is 5 wt%
In addition, a kneading resin made of a thermoplastic elastomer composition was manufactured by air-cooled inflation in the same manner as in Example 1 except that SEBS (manufactured by Asahi Kasei, trade name Tuftec H1052, S / EB ratio 20/80) was added in an amount of 10 wt%. A film was formed in the same manner as above using a membrane device to obtain a sample, and the physical properties of the sample were examined according to the test methods described above. The results are shown in Table 1.

Example 4. In Example 3, instead of SEBS, SIS (trade name VECTOR manufactured by Exxon Chemical Co., Ltd.
4111) except that the kneaded resin composed of the thermoplastic elastomer composition was filmed in the same manner as above using an air-cooled inflation film forming apparatus to obtain a sample, and the sample was tested according to the test method described above. The physical properties were investigated. The results are shown in Table 1.

Comparative Example 1. In Example 1, modified SEB
An air-cooled inflation film forming apparatus was used to prepare a kneading resin composed of a thermoplastic elastomer composition in the same manner as in Example 1 except that S was changed to a modified SEBS having an S / EB ratio of 40/60 (manufactured by Asahi Kasei Corp., trade name Tuftec M1953). A film was obtained in the same manner as described above using, to obtain a sample, and the physical properties of the sample were examined according to the above-mentioned test methods. The results are shown in Table 1.

Comparative Example 2. In Example 3, modified SEB
A kneaded resin made of the thermoplastic elastomer composition was filmed in the same manner as above using an air-cooled inflation film forming apparatus in the same manner as in Example 3 except that S was not blended to obtain a sample. The physical properties were investigated in accordance with. The results are shown in Table 1.

Comparative Example 3. A thermoplastic elastomer composition was prepared in the same manner as in Example 1 except that the ester thermoplastic polyurethane was 60 wt%, the high-pressure low-density polyethylene was 20 wt%, and the modified SEBS was 3 wt%. The kneaded resin was filmed in the same manner as above using an air-cooled inflation film forming apparatus to obtain a sample, and the physical properties of the sample were examined according to the above-mentioned test methods. The results are shown in Table 1.

Comparative Example 4. Physical properties of a commercially available polyurethane film (trade name: Silklon manufactured by Okura Kogyo Co., Ltd.) were examined in the same manner as described above. The results are shown in Table 1.
Shown in.

[0027]

[Table 1]

The following can be seen from Table 1. The films of Examples 1 to 4 of the present invention have small strength at low stress. For example, the strength at the time of double expansion and contraction (100% 1 cycle hysteresis curve) is 300 gf / 25 mm or less, and the strain at that time is 13% or less. Further, the usual urethane film has a poor adhesiveness to the hot melt adhesive, which is a serious problem depending on the application, but the films of Examples 1 to 4 are also excellent in hot melt adhesiveness. When such a film is laminated with a non-woven fabric or the like with a hot melt adhesive and used for various uses such as waist gathers, side gathers, and crotch gathers of disposable paper diapers, the feel, feel and the like are optimal. On the other hand, the film of Comparative Example 1 has a styrene / ethylene-butene ratio of the modified SEBS in the resin composition of 40/60 wt%, and has a high styrene content, so that the strength and strain during double stretching are large. Also, there is a problem such as becoming hard again. Comparative Example 2 is a system in which ester-based thermoplastic polyurethane and SEBS are mainly used, and a modified SEBS which is a compatibilizing agent for the both is not used. With this combination, film formation was impossible. Comparative Example 3
Shows that the modified SEBS is added in an amount of 3 wt%, and the hot melt adhesiveness is poor. Comparative Example 4 is a commercially available urethane film, which has problems of poor hot melt adhesion and high strength at low stress.

[0029]

As described above, according to the present invention, it is suitable for a film having an excellent expansion / contraction function under a low stress, a small expansion / retraction residual strain, an excellent hot melt adhesive property at a high speed, and an appropriate strength. A thermoplastic polyurethane composition can be provided. Conventional urethane film is 30 ~
Hysteresis curve at 100% elongation is stronger than urethane foam, and residual strain at 100% elongation is also large.
Although there were problems such as poor adhesion with hot melt adhesives, the composition of the present invention eliminates these drawbacks,
It is possible to provide a low-cost film having a function equivalent to that of foamed foam, and in particular, it is useful as a polyurethane film which can be hot-melt laminated with a non-woven fabric or the like and used for various gathers in disposable diapers.

Claims (1)

[Claims] 1. (a) Thermoplastic polyurethane resin 40 to 7
0% by weight, (b) ethylene-propylene-diene copolymer 10 to 25% by weight (c) low density polyethylene resin 1
0 to 25% by weight (d) 5 to 20% by weight of a styrene elastomer modified with an unsaturated carboxylic acid or a derivative thereof and having a styrene ratio of 30% by weight or less, and (e) 0 to 20% by weight of a modified styrene elastomer. % Of a thermoplastic polyurethane composition.