JPH0852808A - Method for prevention of blocking of stretchable film consisting of thermoplastic polyurethane resin composition - Google Patents

Abstract

PURPOSE:To provide a method for prevention of blocking of a stretchable film consisting of a thermoplastic polyurethane resin composition. CONSTITUTION:A detachable film made of a resin composition consisting of 40-60wt.% of thermoplastic polyurethane, 10-30wt.% of ethylene-propylene-diene copolymer, 10-30wt.% of low density polyethylene resin, 10-30wt.% of styrene elastomer modified with unsaturated carboxylic acid or its derivative, and 2-10wt.% of unmodified styrene elastomer is prevented from being blocked by this method. This method is composed of the following processes; (A) a raw fabric of the stretchable film is taken off so that hardness from a surface of a take-off material [according to spring hardness test (type C) specified in JIS K 6301] is 60 degree or under; (B) the taken-off material of the raw fabric is aged at 60 deg.C or lower for 3hr or longer; (C) the raw fabric is drawn out and slit by a specific width; and (D) the slit raw fabric is taken off so that the hardness from the surface of the coiled material is 75 degree or under.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for preventing an elastic film made of a thermoplastic polyurethane resin composition from blocking, and is used for various gathers in disposable diapers and the like by laminating it with a non-woven fabric or the like by hot melt. The present invention relates to a method for preventing a stretch film from blocking, which is suitable for

[0002]

2. Description of the Related Art The waist gathers of diapers and gathers of sanitary products are required to have a stretch function with low stress and good hot melt adhesiveness at high speed. Currently, foamed urethane foam, urethane film, etc. are used in terms of functionality. Most of the practical examples are urethane foams, but they are expensive and have problems in performance or productivity when applied to diapers. In addition, the urethane film has a hysteresis strength at 10% to 100% elongation and 10% more than urethane foam.
There is a problem that the residual strain at 0% elongation is large and the adhesiveness with the hot melt adhesive is poor, and that blocking is particularly likely to occur.

Therefore, an object of the present invention is to provide a stretch film made of a thermoplastic polyurethane resin composition,
It is to provide a method of preventing blocking.

[0004]

Means for Solving the Problems As a result of intensive studies in view of the above objects, the present inventors have found that a raw material of a stretchable film made of a thermoplastic polyurethane resin composition is softly wound and aged under predetermined conditions. The present invention was discovered by discovering that blocking was not caused for a long time when a large amount of material was wound so that the hardness from the surface after conditioning and slitting became relatively large, and the present invention was conceived.

That is, the method for blocking an elastic film made of the thermoplastic polyurethane resin composition of the present invention is as follows: (A) The raw material of the elastic film is used to measure the hardness from the surface of the wound material (JIS K6301 spring hardness test). (According to (C type)) is 60 degrees or less, and (B) the wound material of the original fabric is aged at a temperature of 60 ° C. or less for 3 hours or more,
(C) Feeding out the original fabric, slitting it into a predetermined width,
(D) The slit material has a hardness from the surface of the roll.
It is characterized in that it comprises a step of winding so as to be 75 degrees or less.

The present invention will be described in detail below. First, the thermoplastic polyurethane resin composition used in the method of the present invention is as follows.

[1] Component of Thermoplastic Polyurethane Resin Composition (a) Thermoplastic Polyurethane Examples of the thermoplastic polyurethane usable in the present invention include long-chain polyols such as polyester type, adipate type, polyether type, polycaprolactone type, etc. , Short chain polyols,
A polyurethane elastomer obtained by polyaddition reaction of diisocyanate or the like through a urethane bond in the molecule is mentioned. Examples of long-chain polyols include polyethylene glycol and polypropylene glycol, and examples of short-chain polyols include ethylene glycol, 1,4-butanediol, 1,4-hexanediol, and the like, and further diisocyanates. Examples include tolylene diisocyanate, 4,4′-diphenylmethane diisocyanate, hexamethylene diisocyanate, and the like. Among these, an adipate-based polyurethane elastomer is particularly preferable.

Thermoplastic polyurethane has a softening temperature of 170
It is preferable that the hardness at the softening temperature (according to JIS K6301 spring type hardness test (C type). The same applies hereinafter) at 70 to 88 ° C. at ˜190 ° C. If the softening temperature is less than 170 ° C. or the hardness is less than 70 ° C., blocking is likely to occur during film formation by the inflation method or the like, and it is difficult to separate into two after slitting both ears. On the other hand, when the softening temperature exceeds 190 ° C. or the hardness exceeds 88 ° C., the stretchability, flexibility and hot melt contact property of the film become poor.

(B) Ethylene-propylene-diene copolymer (EPDM) EPDM is an elastomeric copolymer composed of ethylene, propylene and a diene compound, and examples of the diene compound include ethylidene norbornene and 1,4-hexadiene. , Dicyclopentadiene and the like. Such ethylene-propylene-diene copolymer has an ethylene content of 59 to 70 mol% and a propylene content of 29 to 40.
The mol% and the content of the diene compound are preferably 1 to 10 mol%. More preferably ethylene is 62-66
Mol%, propylene 31-37 mol%, and diene compound 3-6 mol%.

The number average molecular weight of EPDM is preferably 400,000 to 600,000 and the density is preferably 0.87 g / cm ³ or less. Furthermore, the melt index (MI, 190 ° C, 2.16kg load) is 0.1-
12.0 g / 10 min is preferred, more preferably 0.3-5.0 g
/ 10 minutes.

(C) Low Density Polyethylene Resin As the low density polyethylene resin used in the present invention,
High-pressure ethylene homopolymer (low-density polyethylene, LDPE) or copolymer containing ethylene as a main component and 20% by weight or less of a vinyl compound, such as ethylene-vinyl acetate copolymer, ethylene-acryl. Examples thereof include ethyl acid copolymers. It may also be linear low density polyethylene (LLDPE).

In the case of LDPE, the density is preferably 0.935 g / cm ³ or less, more preferably 0.920 to 0.925 g / cm ³ , and the melt index (MI, 190 ° C., 2.16 kg load) is 0.05 to 20 g / 10 minutes is preferred, more preferably 0.
It is 5 to 5 g / 10 minutes.

In the case of LLDPE, the density is preferably 0.935 g / cm ³ or less, more preferably 0.918 to 0.925 g / cm ³ , and the melt index (MI, 190 ° C, 2.16 kg load) is 0.5 to 10 g / 10 minutes is preferred, more preferably 0.
It is 8 to 5 g / 10 minutes.

(D) Modified Styrenic Elastomer The modified styrenic elastomer can be obtained, for example, by subjecting a styrene elastomer to an addition reaction (for example, grafting) with an unsaturated carboxylic acid or a derivative thereof. As the styrene elastomer, a styrene-butadiene block copolymer composed of a polymer block mainly containing styrene and a polymer block mainly containing butadiene or isoprene, a block copolymer of styrene-isoprene, or a block thereof. Hydrogenated products of copolymers can be mentioned. Specific examples include styrene-butadiene-styrene block copolymer (SBS), styrene-ethylene-butene-styrene block copolymer (SEBS), styrene-isoprene-styrene block copolymer (SI).
S), styrene-ethylene-propylene-styrene block copolymer (SEPS) and the like. Of these, hydrogenated compounds (SEB
S, SEPS) is preferred.

The styrene elastomer preferably has a styrene ratio of 30% by weight or less. For example, by hydrogenating a styrene-butadiene-styrene block copolymer, a styrene-ethylene-butene-styrene block copolymer (SEBS) is obtained, but the compounding ratio of styrene (S) and ethylene-butene (EB) is used. S / E
Use B of 30/70 or less. The same applies to other styrene-based elastomers. When the ratio of styrene exceeds 30% by weight (S / EB is 30/70), the elastic film obtained is hard and the strain becomes large.

As the unsaturated carboxylic acid or its derivative, maleic acid, fumaric acid, itaconic acid, acrylic acid,
Crotonic acid, endo-bi-cyclo- [2,2,1] -5-heptene
-2,3-dicarboxylic acid, cis-4-cyclohexene-1,2
-Dicarboxylic acids and their anhydrides, imidized products and the like can be mentioned, but maleic anhydride is preferably used. Acid value of 2 by adding unsaturated carboxylic acid or its derivative
It is preferable to be ~15mgCH ₃ ONa / g, more preferably from 5~10mgCH ₃ ONa / g.

(E) Unmodified Styrenic Elastomer The unmodified styrenic elastomer has poor compatibility with the thermoplastic polyurethane, so that it causes micro-roughness on the surface of the film, resulting in adhesion when the films are superposed. It has the effect of reducing the sex and improving the blocking property. As the unmodified styrene-based elastomer, the above
The styrene-based elastomer described in (d) can be used. In this case, it is preferable to use one having a styrene ratio of 30% by weight or less.

In addition to the above-mentioned components, an antioxidant, an ultraviolet absorber, a colorant, an inorganic filler and the like can be appropriately added to the thermoplastic polyurethane resin composition.

[2] Mixing Ratio of Each Component (a) Thermoplastic Polyurethane Based on 100% by weight of the total amount of thermoplastic polyurethane, 40 to 40% of thermoplastic polyurethane is used.
The amount is 60% by weight, preferably 45 to 55% by weight. If the blending amount of the thermoplastic polyurethane is less than 40% by weight, the properties of the polyurethane elastomer are lost and the stretch flexibility is poor,
In addition, the characteristics of polyurethane, such as abrasion resistance, heat resistance, and mechanical strength, are low. On the other hand, when it exceeds 60% by weight, the hot melt adhesiveness at high speed becomes poor. Further, the inflation tube is easily blocked, and it becomes difficult to separate it into two pieces after slitting both ears.

(B) Ethylene-propylene-diene copolymer The total amount is 100% by weight, the ethylene-propylene-diene copolymer is 10 to 30% by weight, preferably 15 to 25% by weight. If the amount is less than 10% by weight, the stability of the film during film formation is insufficient, and the product's stretch flexibility, hot melt adhesiveness, rubber elasticity (large hysteresis strain after 100% stretch) is inferior. . On the other hand, if it exceeds 30% by weight, the inflation tube tends to be blocked, and it becomes difficult to peel it off into two pieces after slitting both ears.

(C) Low-Density Polyethylene Resin Based on the total amount of 100% by weight, low-density polyethylene-based resin
The amount is 10 to 30% by weight, preferably 15 to 25% by weight. When the blending amount of the low density polyethylene resin is less than 10% by weight,
Because the inflation tube is easy to block,
Difficult to peel into two after slitting both ears. On the other hand, if it exceeds 30% by weight, the flexibility and hot-melt adhesiveness of the product, the rubber elasticity (the hysteresis strain after 100% expansion and contraction is large) and the like become poor.

(D) Modified styrene-based elastomer The total amount is 100% by weight, the modified styrene-based elastomer is 10 to 30% by weight, and preferably 10 to 25% by weight.
If the amount of the modified styrene-based elastomer compounded is less than 10% by weight, the hot melt adhesiveness is poor and it is difficult to form a film. On the other hand, if it exceeds 30% by weight, discoloration and mechanical strength decrease.

(E) Unmodified Styrenic Elastomer The total amount of the unmodified styrenic elastomer is 100% by weight and 2 to 10% by weight, preferably 3 to 7% by weight. If it is less than 2% by weight, the effect of improving the hot melt property cannot be obtained, and if it exceeds 10% by weight, the film-forming property and the mechanical strength of the film are deteriorated.

[3] Production Method After adding other components to the thermoplastic polyurethane resin composition of the above components, if necessary, and dry-blending in advance using, for example, a Henschel mixer or a high speed mixer, for example, 180 to The mixture is melted and kneaded by using an extruder or the like under heating at about 230 ° C. and extruded to form pellets.

As a method for producing a film, a T-die method which is a usual polyolefin film forming method can be used. Considering this, the air-cooled inflation molding method for molding a tubular film is preferable. The air-cooled inflation molding method is preferably carried out at a resin temperature of 180 to 230 ° C. and a blow ratio of 2.0 to 5.0. The thickness of the film can be appropriately selected according to various uses, but is usually preferably 100 μm or less. The more preferable film thickness is 20 to 60 μm. Film thickness is 100 μm
If it exceeds, the film becomes hard, which is not preferable. In the above film forming method, for example, an air-cooled inflation film forming device is used to form a film, which is slit into a predetermined width to form a sheet-shaped or tape-shaped rolled product. Moreover, you may go through a stretching process.

[4] Blocking prevention treatment Blocking prevention treatment includes (A) a loose winding process of the original fabric, (B) a conditioning process by aging, (C) a slitting process after feeding, and (D) a large amount winding process. It consists of a taking process.
Hereinafter, these steps will be described in detail.

(A) Raw Fabric Winding Step The film prepared by the above method (in the case of inflation film, a film having both ears slit) is loosely wound as a raw fabric. At this time, the winding degree is such that the hardness from the surface is 60 degrees or less, and preferably 20 to 50 degrees. If the hardness from the surface of the wound material exceeds 60 degrees, shrinkage due to aging causes the winding to become too tight and blocking tends to occur.

(B) Conditioning process by aging Next, the wound film raw material is aged to about 2
Shrink ~ 3%. In order to obtain this shrinkage ratio, aging is performed at a temperature of 60 ° C. or lower, preferably 45 ° C. to 60 ° C. for 3 hours or more, preferably 12 to 48 hours. Aging temperature is 60 ℃
If it exceeds, blocking tends to occur, and if the aging time is less than 3 hours, a sufficient effect cannot be obtained.

(C) Slit Step After the aged film original sheet is fed out, it is slit into a predetermined width. The slit width may be, for example, 3 mm or more. (D) Large-scale winding step The heat-treated slit film is wound in a large amount so that the hardness from the surface of the wound material is 75 degrees or less, preferably 50 to 60 degrees, to obtain a product. If the hardness from the surface when a large amount is wound exceeds 75 degrees, the core portion may block during long-term storage, which is not preferable.

[0030]

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited thereto.

The test methods in Examples and Comparative Examples are as follows. Each measured value is shown in the MD (longitudinal) direction of the film.

(1) Strength at 50% elongation: Measured with the following equipment and conditions in accordance with JIS L1096. Equipment used: Strograph W (manufactured by Toyo Seiki Co., Ltd.) Measurement sample size: 25 mm × 150 mm Chuck interval: 100 mm Peeling speed: 300 mm / min Measuring atmosphere: 23 ° C, 50% RH

(2) Strength at 100% elongation: Measured under the same conditions as (1) according to JIS L1096.

(3) Strength at break: Measured with the following equipment and conditions in accordance with JIS L1096. Equipment used: Strograph W (manufactured by Toyo Seiki Co., Ltd.) Measurement sample size: 25 mm × 150 mm Chuck interval: 50 mm Peeling speed: 300 mm / min Measuring atmosphere: 23 ° C, 50% RH

(4) Elongation at break: In accordance with JIS L1096,
The measurement was performed under the same conditions as (3).

(5) One cycle strain after 100% elongation: JIS
Based on L1096, it measured on the same conditions as (1).

(6) Hot melt adhesiveness: acrylic plate (25
mm × 150 mm) with 25 mm × 25 mm hot melt adhesive applied to one end in the longitudinal direction (30 g / m ² ), and the sample film (25 mm × 150 mm) placed on it, and a rubber roll with a load of 250 g. Lightly press once with and stick to an acrylic plate, then under the same conditions as (1), use Strograph W (Toyo Seiki Co., Ltd.)
180 degree peeling test was performed.

(7) Heat seal adhesiveness (minimum adhesive temperature): silicone rubber sheet, sample film (200 mm
× 200 mm), a patch made of the same material as the sample film (diameter 15 mm) is stacked in order from the bottom and covered with a fluoroglass sheet (thickness 0.09 mm), and then a 3.5 kg load is applied from the top of the fluoroglass sheet. The patch and film were heated while pressing the iron for a second to measure the temperature of the film. After that, remove the silicone rubber sheet and the fluoroglass, use the sample patch film, and use the same condition as in (3).
A tensile test was conducted until 0% elongation to examine the occurrence of peeling.
Experiments were conducted at various temperatures, and the lowest heating temperature at which peeling did not occur was defined as the lowest adhesion temperature.

(8) Blocking Degree (Peeling Strength): The original film film is slit into a width of 50 mm, and it is 2,000 by the record winding method.
A film of 0 m is wound on a paper tube with an outer diameter of 90 mm, and the diameter is 300
I got a roll of mm. The resulting wound tape is 1 at 40 ℃
After being left for a week, the peel strength of the tape at a portion 10 mm away from the outer circumference of the paper tube was measured.

(9) Hardness: In accordance with JIS K6301 spring type hardness test (C type), ASKER Type C (KOBUNSHI K
EIKI Co. Ltd.).

Example 1 Adipate thermoplastic polyurethane (PU, trade name: Resamine P327, hardness: 85 degrees, softening temperature: 187 ° C., 48% by weight of Dainichiseika Kogyo Co., Ltd.) and ethylene-propylene-
Diene copolymer (EPDM, trade name: Vistalon V370
8, Exxon Chemical Co., Ltd. 16% by weight, high pressure low density polyethylene (LDPE, trade name: NUC polyethylene NUC-8506, density 0.923 g / cm ³ , Nippon Unicar Co., Ltd.)
12% by weight and a hydrogenated product of a styrene-butadiene copolymer modified with maleic anhydride (modified SEBS, trade name: Tuftec M-1913, S / EB ratio: 30/70, Asahi Chemical Industry Co., Ltd.) 20% by weight, styrene-butadiene-
Hydrogenated styrene block copolymer (unmodified SEB
S, product name: Tuftec H-1052, Asahi Kasei Corporation
4% by weight) was dry-blended using a Henschel mixer, and then melt-kneaded at 225 ° C. using an extruder.
Using the kneaded resin thus obtained, a film having a thickness of 35 μm and a folding width of 1070 mm (blow-up ratio: 4.5) was prepared by an air-cooled inflation film forming apparatus, and both ears were slit and wound into a sheet. At this time, the hardness of the film from the surface was 40 degrees.

The wound web was conditioned in an oven at 50 ° C. for 24 hours, and then slit with a narrow slitter to produce a tape having a width of 50 mm and a length of 2,000 m. I made it. The hardness from the surface of the film at this time was 50 to 60 degrees. The physical properties of the obtained tape were measured according to the above-mentioned test methods. Table 1 shows the measurement results.

Comparative Example 1 The same thermoplastic polyurethane resin composition as in Example 1 was used and wound into a sheet in the same manner as in Example 1, and then the raw fabric was slit with a narrow slitter to give a width of 50 mm. × Length
A 2,000-meter tape was wound into a record. At this time, the hardness of the film from the surface was 80 degrees. The physical properties of the obtained tape were measured in the same manner as in Example 1. Table 1 shows the measurement results.

COMPARATIVE EXAMPLE 2 16% by weight of LDPE was added instead of adding unmodified SEBS.
In the same manner as in Example 1 except for the above, a sheet-shaped roll was obtained. The obtained raw fabric was slit using a narrow slitter and a tape having a width of 50 mm and a length of 2,000 m was wound into a record winding form. At this time, the hardness of the film from the surface was 80 degrees. The physical properties of the obtained tape are shown in Example 1.
It measured similarly to. Table 1 shows the measurement results.

Comparative Example 3 An elastic film was prepared in the same manner as in Example 1 except that the modified SEBS and the unmodified SEBS were not blended, but the adipate thermoplastic polyurethane was 60% by weight, the EPDM was 20% by weight, and the LDPE was 20% by weight. Then roll it up into a sheet,
The physical properties of the film were measured. The hardness from the surface of the film at this time was 85 degrees. Table 1 shows the measurement results.

Table 1 Examples Comparative examples Physical properties 1 1 2 3 Film thickness (μm) 32 32 32 35 Unit weight (g / m ² ) 27 27 30 36 50% Strength at extension (gf / 25mm) 260 270 290 320 100 % Strength at extension (gf / 25mm) 320 320 350 370 Strength at break (gf / 25mm) 2500 2630 2800 1500 Elongation at break (%) 540 680 650 550 100% Strain after elongation (%) 6 10 12 15 Hot Melt adhesion (gf / 25mm) 50 58 35 2 Blocking degree (gf / 25mm) 10 20 40 70

As is apparent from Table 1, the film produced by applying the antiblocking method of the present invention has excellent blocking resistance.

[0048]

As described in detail above, in the method for preventing the stretching film of the present invention from blocking, the raw material of the stretching film made of the softly wound thermoplastic polyurethane resin composition is aged to shrink the film slightly. After
Since a large amount is wound to a higher hardness, the resulting film has excellent blocking resistance without being tightened by shrinkage due to aging.

The elastic film obtained by such a method for preventing the elastic film from blocking according to the present invention is suitable for laminating non-woven fabrics and the like with hot melt and for various gathers in the wings of sanitary products, disposable diapers and the like.

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Claims (2)

[Claims] 1. A method for preventing blocking of a stretchable film comprising a thermoplastic polyurethane resin composition, which comprises (A)
The original fabric of the stretch film has a hardness of 60 from the surface of the roll (according to JIS K6301 spring hardness test (C type)).
(B) Aged the wound material at a temperature of 60 ° C. or less for 3 hours or more, and (C) unwinds the material and slits it into a predetermined width. D) A method comprising a step of winding a slit original fabric so that the hardness from the surface of the roll is 75 degrees or less. 2. A method for preventing a stretchable film from blocking, which comprises the thermoplastic polyurethane resin composition according to claim 1, wherein the thermoplastic polyurethane resin composition comprises:
(a) 40-60 wt% thermoplastic polyurethane, (b) 10-30 wt% ethylene-propylene-diene copolymer, (c) 10-30 wt% low-density polyethylene resin, (d) unsaturated carboxylic acid Alternatively, 10 to 30% by weight of styrene-based elastomer having a ratio of styrene modified with a derivative thereof of 30% by weight or less, and
(e) A method comprising 2 to 10% by weight of an unmodified styrenic elastomer.