JP4795313B2 - Water-absorbing film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a film that has a uniform film thickness and a surface free of defects such as eye fishes, and has good water absorption properties and heat resistance. <P>SOLUTION: This film is composed of a layer of a water absorptive resin composition comprising (A) a polyethylene resin composition of 100 parts by mass and (B) a water absorptive filler of 5-200 parts by mass. The polyethylene resin composition (A) comprises (A-1) an ethylene polymer of 99-60 mass% having following characteristics of (i)-(iv): (i) a peak top melting point (Tm) at the highest temperature side in a DSC melting curve is &ge;110&deg;C, (ii) an amount of heat of melting (&Delta;H) in the DSC melting curve is 90-180 J/g, (iii) crystallinity at 110&deg;C (Xc 110) is 10-60%, and (iv) MFR (190&deg;C, 21.18 N) is &ge;0.1 g/10 min and &lt;10 g/10 min, and (A-2) an acid-modified resin of 1-40 mass%, wherein the total amount of the component (A-1) and the component (A-2) is 100 mass%, and the water absorptive filler (B) has a particle size (D99) of &le;30 &mu;m and a particle size (D50) of &le;20 &mu;m. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

The present invention relates to a film excellent in water absorption and heat resistance. In particular, the present invention relates to a film that can be used to protect moisture-sensitive contents such as foods, pharmaceuticals, clothing, footwear, electronic components, electronic devices, secondary batteries, and the like.

Conventionally, dry products such as dry matter, confectionery, and medicines are packaged together with a small bag in which a desiccant such as silica gel is enclosed. This packaging is carried out by putting a dry product into a bag-shaped packaging material, further feeding a small bag containing a desiccant, and sealing the bag-shaped packaging material. Although the process of introducing the desiccant-containing sachet is usually automated, it complicates the packaging process and may be a manual operation depending on the dried product. Furthermore, in foods such as confectionery, since the desiccant is enclosed in the food, the desiccant may be mistakenly mixed into the food or accidentally swallowed.

Then, it replaced with the desiccant containing small bag and the film containing the desiccant which can be utilized as a packaging material is proposed. For example, a molecular sieve (zeolite) as a desiccant is kneaded with a base resin mainly composed of a high melt flow rate (MFR) ethylene methacrylic acid copolymer (EMAA) on a PET base film by the T-die method. A film obtained by extrusion lamination is known (for example, Patent Document 1). High MFR EMAA has good miscibility with molecular sieves, so that good film formation is possible even when the molecular sieve is highly filled. However, this film is inferior in heat-resistant fusing property and solvent resistance because EMAA as a base has a low melting point. Among the contents that are protected by moisture-absorbing film and dislike moisture, especially in the case of electronic components, electronic devices, secondary batteries, etc., they can be protected with sufficient drying even when they become high temperature. In addition, the film is required to be heat resistant. Therefore, the film cannot be used in such a field.

Also known is a film obtained by kneading a molecular sieve with a resin of MFR 10 or higher and coextruding it with a thermoplastic resin by an inflation method (for example, Patent Document 2). A resin with a high MFR improves the miscibility with the molecular sieve to some extent and enables film formation even when the molecular sieve is highly filled. However, the improvement in the miscibility is not sufficient, and the film thickness stability of the film is also poor. It is enough.
JP 2002-206046 A JP-A-2005-280188

An object of the present invention is to provide a film having a uniform film thickness and a surface free from defects such as bumps and having good water absorption and heat resistance.

As a result of intensive investigations to obtain a film having excellent appearance and film thickness stability and excellent heat resistance even when highly filled with a water-absorbing filler, the inventor has found a specific melting point as a resin mixed with the water-absorbing filler. The use of a mixture of an ethylene polymer having a heat of fusion, crystallinity and MFR with a specific amount of acid-modified resin improves both the miscibility with the water-absorbing filler and the heat resistance. The headline, the present invention has been reached.

That is, the present invention
(A) A film comprising a layer of a water-absorbent resin composition containing 100 parts by mass of a polyethylene-based resin composition and (B) 5 to 200 parts by mass of a water-absorbent filler, wherein the polyethylene-based resin composition (A) is:
(A-1) 99-60 mass% of low density polyethylene or linear low density polyethylene having the following properties (i) to (iv):
(I) The peak top melting point (Tm) on the highest temperature side in the DSC melting curve is 110 ° C. or higher.
(Ii) The heat of fusion (ΔH) in the DSC melting curve is 90 to 180 J / g.
(Iii) Crystallinity (Xc110) at 110 ° C. is 10 to 60%, and (iv) MFR (190 ° C., 21.18N) is 0.1 g / 10 min or more and less than 10 g / 10 min, and
(A-2) Acid-modified resin 1-40 mass%
Where the total amount of component (A-1) and component (A-2) is 100% by weight,
The water-absorbing filler (B) has a particle size (D99) of 30 μm or less and a particle size (D50) of 20 μm or less. Here, D99 and D50 are accumulated from the smaller particle size in the particle size distribution to 99. It is the film which says the particle diameter in the point used as mass% and 50 mass%.

The film of the present invention has a uniform film thickness and a surface free from defects such as bumps, and has good hygroscopicity and heat resistance, so that it is sensitive to moisture, such as food, medicine, clothing, footwear, electronic It is useful for protecting parts, electronic devices, secondary batteries, etc.

Further, by further including a specific polyolefin layer as the outer layer, the heat resistance is further enhanced, and the film can be easily handled.

(A) Polyethylene resin composition The polyethylene resin composition in the present invention includes an ethylene polymer (A-1) and an acid-modified resin (A-2).

(A-1) Ethylene-based polymer The ethylene-based polymer needs to satisfy the following (i) to (iv) so as to have sufficient heat resistance and filler acceptability.
(I) The peak top melting point (Tm) on the highest temperature side in the DSC melting curve is 110 ° C. or higher.
(Ii) The heat of fusion (ΔH) in the DSC melting curve is 90 to 180 J / g.
(Iii) The crystallinity (Xc110) at 110 ° C. is 10 to 60%, and (iv) MFR (190 ° C., 21.18N) is 0.1 g / 10 min or more and less than 10 g / 10 min.

When the peak top melting point (Tm) is lower than 110 ° C., the heat resistance may be insufficient. The peak top melting point (Tm) is preferably 120 ° C. or higher, more preferably 125 ° C. or higher.

Further, if the heat of fusion (ΔH) is less than 90 J / g, the heat resistance may be insufficient, and if it exceeds 180 J / g, the filler acceptability may be insufficient and the film forming property may be inferior. The heat of fusion (ΔH) is preferably 100 to 170 J / g.

Further, if the crystallinity (Xc110) is less than 10%, the heat resistance may be insufficient, and if it exceeds 60%, the filler acceptability may be insufficient and the film forming property may be inferior. The crystallinity (Xc110) is preferably 15 to 45%. The crystallinity at 110 ° C. means the ratio of the heat of fusion at 110 ° C. or higher to the total heat of fusion ΔH in the DSC melting curve.

Further, when the MFR is 10 g / 10 min or more, the melt-kneading property (filler dispersibility) between the polyethylene resin composition (A) and the water-absorbing filler (B) becomes insufficient, and the pulling property during film formation is reduced. In some cases, the thickness of the film may be difficult to adjust at less than 0.1 g / 10 minutes. The MFR is preferably 0.2-7 g / 10 min, most preferably 0.5-5 g / 10 min.

In the present specification, unless otherwise specified, the DSC melting curve is obtained by using a DSC Q1000 model of TA Instruments (TE Instruments Japan Co., Ltd.) and holding the sample at 190 ° C. for 5 minutes. Obtained by performing DSC measurement with a temperature program of cooling to −10 ° C. at a temperature decrease rate of 10 ° C./min, holding at −10 ° C. for 5 minutes, and then heating to 190 ° C. at a temperature increase rate of 10 ° C./min. It is a curved line.

The ethylene polymer in the present invention is not particularly limited as long as it satisfies the above requirements (i) to (iv). For example, low density polyethylene, linear low density polyethylene, ultra-low density polyethylene, high density polyethylene, and a copolymer of ethylene and an α-olefin (for example, 1-butene, 1-hexene, 1-octene, etc.) can be mentioned. An ethylene copolymer using vinyl acetate, methyl acrylate, ethyl acrylate, or the like as a comonomer has a large decrease in crystallinity due to the comonomer, and thus it is difficult to satisfy the requirements (i) to (iv).

An ethylene-type polymer can be used individually by 1 type or as a mixture which mix | blended 2 or more types arbitrarily. When used as a mixture, the entire mixture may satisfy the above requirements (i) to (iv).

(A-2) Acid-modified resin The acid-modified resin has improved water miscibility by improving the miscibility between the hydrophobic ethylene-based polymer (A-1) and the hydrophilic water-absorbing filler (B). It is a component for facilitating the dispersion of the functional filler so that the film does not have defects such as bumps when it is formed.

The acid-modified resin used in the present invention may be anything as long as it is a resin modified with an unsaturated carboxylic acid or a derivative thereof. Examples of unsaturated carboxylic acids include, for example, maleic acid, itaconic acid, fumaric acid, and examples of derivatives thereof include, for example, maleic acid monoester, maleic acid diester, maleic anhydride, itaconic acid monoester, Examples include itaconic acid diester, itaconic anhydride, fumaric acid monoester, fumaric acid diester, fumaric anhydride and the like. Examples of the resin include linear polyethylene, ultra-low density polyethylene, high density polyethylene, ethylene-vinyl acetate (VA) copolymer, ethylene-ethyl acrylate (EA) copolymer, ethylene-methacrylate copolymer, and other ethylene. Examples thereof include a polymer, a propylene polymer, and a styrene elastomer. In view of miscibility with the ethylene polymer (A-1), the resin is most preferably an ethylene polymer.

The acid-modified resin preferably has an MFR (190 ° C., 21.18 N) of 0.1 to 10 g / 10 min. More preferably, it is 0.2 to 7 g / 10 minutes, and most preferably 0.5 to 5 g / 10 minutes. If the MFR is higher than the above upper limit, the drawability during film formation may be reduced. If the MFR is lower than the lower limit, it may be difficult to adjust the thickness of the film.

Specific examples of acid-modified resins include Admer (trade name) manufactured by Mitsui Chemicals, Adtex (trade name) manufactured by Nippon Polyolefin Co., Ltd., Polybond (trade name) manufactured by Crompton, and Sumitomo Chemical Co., Ltd. ) Manufactured Bond First (trade name).

The acid-modified resins can be used alone or in combination of two or more.

The polyethylene resin composition (A) contains 99 to 60% by mass of the ethylene polymer (A-1) and 1 to 40% by mass of the acid-modified resin (A-2). More preferably, they are 97-70 mass% of ethylene-type polymer (A-1), and 3-30 mass% of acid-modified resin (A-2), More preferably, ethylene-type polymer (A-1) 95- 80% by mass and 5 to 20% by mass of the acid-modified resin (A-2). When the acid-modified resin (A-2) is small (that is, the ethylene polymer (A-1) is large), the water-absorbing filler (B) is not sufficiently dispersed, and there is a large amount of grease during film formation. Or defects such as bumps are likely to occur in the resulting film. On the other hand, when the acid-modified resin (A-2) is large (that is, the ethylene polymer (A-1) is small), the interaction between the acid-modified resin and the water-absorbing filler becomes very strong, and the water-absorbing resin composition In some cases, the kneading load during production of the product and the extrusion load during film formation are increased. Moreover, the tensile elongation of the film obtained may fall.

(B) Water-absorbing filler The water-absorbing filler may be any water-absorbing filler as long as it has water absorption and is stable and does not elute into the solvent. For example, magnesium sulfate, aluminum oxide, silica gel, lime, calcined hydrotalcite, and molecular sieve can be used, and these can be used alone or in combination of two or more.

As the water-absorbing filler, those having a controlled particle size distribution are used so that a uniform film can be obtained which is well dispersed in the polyethylene-based resin composition and has no defects such as blisters. That is, the water-absorbing filler used in the present invention has a particle size (D99) of 30 μm or less and a particle size (D50) of 20 μm or less, where D99 and D50 each have a small particle size in the particle size distribution. The particle diameter at the point where it becomes 99% by mass and 50% by mass is accumulated. D99 is preferably 20 μm or less, more preferably 15 μm or less. Moreover, D50 becomes like this. Preferably it is 0.01-15 micrometers, More preferably, it is 0.1-10 micrometers. A coarse filler having a particle size exceeding the upper limit may become a film defect or foreign matter when it is formed. In addition, fillers with too fine particles aggregate to form defects or foreign matter of the film, or if they do not aggregate, a large amount of air is embraced, resulting in poor melt-kneading workability in the production of the water absorbent resin composition. There is a case to do. In order to control the particle size distribution, there are a method of generating large particles and pulverizing and classifying them, and a method of generating fine particles from the beginning and classifying them. Either method may be used as long as the particle size distribution can be controlled within the above range, and is not particularly limited. However, from the viewpoint of extrusion load and film forming property, a method of generating fine particles from the beginning is more preferable.

The water-absorbent resin composition according to the present invention is 5 to 200 parts by weight, preferably 10 to 150 parts by weight, more preferably 15 parts by weight of the water-absorbent filler (B) with respect to 100 parts by weight of the polyethylene resin composition (A). Included in an amount of ~ 120 parts by weight. When the blending amount of the water-absorbing filler (B) is less than the above lower limit, a sufficient water absorbing function cannot be obtained, and when it exceeds the upper limit, the film forming property may be deteriorated.

In addition to the above components, the water-absorbent resin composition according to the present invention includes a slip agent, phosphorus-based, phenol-based, sulfur-based antioxidant, anti-aging agent, light stabilizer, and ultraviolet absorber as necessary. Weathering agent such as copper damage prevention agent, aromatic phosphate metal salt-based, gelol-based nucleating agent, anti-static agent such as glycerin fatty acid monoester, coloring agent, fragrance, antibacterial agent, magnesium oxide, zinc oxide Further, additives such as fillers such as calcium carbonate, talc and metal hydrate, plasticizers such as glycerin fatty acid ester-based, paraffin oil, phthalic acid-based and ester-based plasticizers may be included.

The slip agent can improve the melt-kneading workability during the production of the water-absorbent resin composition, and can avoid the occurrence of die scum and eye grease during film formation. Examples of the slip agent include metal soaps such as calcium stearate, fatty acid amides such as oleic acid amide and erucic acid amide, polyethylene wax, silicone gum, and silicone oil. 0.1-20 mass parts is preferable with respect to 100 mass parts of polyethylene-type resin compositions (A), and, as for the addition amount of a slip agent, More preferably, it is 1-10 mass parts.

The water-absorbent resin composition according to the present invention can be obtained by melt-kneading the above components (A-1), (A-2) and (B) and optionally an optional additive. The melt-kneading can be performed using a conventional apparatus such as a twin screw extruder or a Banbury mixer. The kneading temperature is preferably higher than the film-forming temperature in order to avoid moisture-absorbing foaming troubles during film formation. The resulting composition can be pelletized by a granulator and then subjected to normal film formation using a T die or the like. In that case, the pelletization is performed using water such as a hot cut method. It is preferable to carry out by a method that does not intervene. Further, a vacuum vent may be provided or a gear pump or the like may be used. Furthermore, it is also possible to use a method in which film formation is directly performed without pelletization, for example, a method in which a composition obtained by melt kneading is directly sent to a T die via a gear pump or the like to form a film.

The film comprising the water-absorbing resin composition layer thus obtained has a good appearance without defects such as bumps, is uniform in thickness, and has sufficient water absorption and heat resistance.

The film of the present invention may further have a polyolefin layer on both sides of the water absorbent resin composition layer. Since the film having no polyolefin layer has high water absorption, when it is placed in the atmosphere, it can absorb water unnecessarily and lower the film function. Therefore, the film having no polyolefin layer needs to be stored and handled in an environment where the humidity is sufficiently low. However, by having the polyolefin layer on both surfaces, the water absorption rate of the water-absorbent resin composition layer can be suppressed, and therefore, it is not necessary to make the environmental conditions related to humidity too strict when managing and handling the film. .

The polyolefin may be any hydrophobic one for the purpose of reducing unnecessary water absorption, but satisfies the following (1) to (2) so that the heat resistance of the film can be further improved. Is preferred.
(1) The peak top melting point (Tm) on the highest temperature side in the DSC melting curve is 125 ° C. or higher, and (2) the crystallinity (Xc120) at 120 ° C. is 55% or higher.
The peak top melting point is more preferably 130 ° C. or higher, still more preferably 135 ° C. or higher, and the crystallinity is more preferably 60% or higher, still more preferably 65% or higher.

Examples of the polyolefin include homopolypropylene, propylene-based polymers such as copolymers of propylene and α-olefins (for example, ethylene, 1-butene, 1-hexene, 1-octene, etc.), low density polyethylene, linear low Examples include density polyethylene, ultra-low density polyethylene, and high density polyethylene.

Specific examples of the polyolefin include F-730NV (trade name, propylene random copolymer) and SP4530 (trade name, high density polyethylene) manufactured by Prime Polymer Co., Ltd.

A film having a polyolefin layer as an outer layer can be produced by co-extrusion using at least three or more multilayer T dies or multilayer spiral dies.

The film comprising the layer of the water-absorbent resin composition of the present invention and the film further having a polyolefin layer as the outer layer of the above film have good water absorption, and therefore, foods such as confectionery and dry foods that are sensitive to moisture It is useful as a protective material for drugs such as drugs and test drugs (for example, urine test paper), clothes, footwear, electronic components, electronic devices, and secondary batteries. Specifically, for example, it is useful as a packaging material for foods, a packaging material for secondary batteries, a hygroscopic material for secondary batteries, an insole for footwear, a cover for clothes, and a packaging material for inspection drugs. In addition, the film further including a polyolefin layer as an outer layer is easier to manage and has improved heat resistance, and is particularly useful as a protective material for electronic parts, electronic devices, and secondary batteries.

EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited to a following example.

Examples 1-7 and Comparative Examples 1-10
Production of a film comprising a layer of a water absorbent resin composition:
The components (parts by mass) shown in Table 1 were dry blended and melt kneaded with a 20 L pressure kneader of Moriyama Co., Ltd. to obtain a water absorbent resin composition, which was then pelletized with a granulator. . The discharge temperature (melt kneading temperature) was 220 ° C., and granulation was performed by a hot cut method. Subsequently, the obtained pellet was formed into a film with a film thickness of 50 μm using a PCM-46 twin screw extruder manufactured by Ikegai Co., Ltd. and a T die manufactured by Toshiba Machine Co., Ltd. The obtained film was stored in a gas substitution type glove box (SG-1000 of As One Co., Ltd.) having a dew point temperature of −50 ° C. or lower. The film formation was performed using a vacuum vent under conditions of a T-die outlet resin temperature of 200 ° C., a chill roll temperature of 40 ° C., and a take-off speed of 10 m / min. The obtained film was subjected to the following evaluation tests (1) to (6). The results are shown in Table 1.

(1) Film appearance Five films cut to A4 size were visually observed and judged according to the following criteria.
○: No foaming or hole opening, and no puncture with a diameter of 0.1 mm or more Δ: No foaming or hole opening, no pit with a diameter of 0.5 mm or more, but with a diameter of 0.1 mm to less than 0.5 mm There are 1 to 10 x: There is foaming or perforation, and there are also items with a diameter of 0.5 mm or more

(2) Film thickness stability Measure the film thickness at 20 locations every 2 cm in the machine direction around the center of the film width, and the standard deviation is 1.5 μm or less “◯”, exceeding 1.5 μm to 3.0 μm The following was designated as “Δ” and those exceeding 3.0 μm were designated as “x”.

(3) Water absorption capacity in solvent Dimethyl carbonate (DMC) / diethyl carbonate (DEC) / ethylene carbonate (EC) = 1/1/1 (volume ratio) was mixed with a very small amount of water to prepare a test solution. The amount of water in this test solution was measured with a Karl Fischer volumetric titration apparatus (AQ-300 from Hiranuma Sangyo Co., Ltd.) (initial water amount). Next, a 450 cm ² film was immersed in 30 g of this test solution, and the water content in the test solution after storage at 25 ° C. for 48 hours was measured in the same manner. In addition, the above operation was performed at 25 degreeC in the gas substitution type | mold glove box (SG-1000 of ASONE CORPORATION) which made dew point temperature -50 degrees C or less by air dryer QD20-75 of IC Corporation. .

(4) sealed by heat sealing to put the water absorption capacity within the volume 400 cm ³ of the transparent moistureproof bag Shinei handheld temperature hygrometer Hygropalm1 Corporation which was conditioned in the film and the glove box 6000 cm ² in the atmosphere The absolute humidity was measured immediately after sealing (initial), after 25 ° C. × 15 minutes, and after 25 ° C. × 2 hours. The measurement was performed at 25 ° C.

(5) Heat resistance Using an HG-100 heat seal tester manufactured by Toyo Seiki Seisakusho Co., Ltd., the film is melted at a predetermined sealing temperature of 80 to 130 ° C. so that the machine direction becomes the tensile direction of the T-shaped peel test. (4 seconds, pressure 0.2 MPa). Next, a T-shaped peel test was performed using an AE-CT type tensile tester manufactured by Toyo Seiki Seisakusho Co., Ltd., with a peeling width of 25 mm, a peeling speed of 100 mm / min, and a peeling angle of 180 °. Films with good heat resistance are those that are judged to have a higher sealing temperature.
○: No or little fusion (peeling strength <0.1 N / 25 mm)
Δ: Slightly fused (peeling strength 0.1 to 2.0 N / 25 mm)
X: Fusing (peeling strength> 2.0 N / 25 mm)

(6) Breaking strength and elongation at break were punched into a JIS No. 5 dumbbell type test piece so that the machine direction was the tensile direction, and measurement was performed using an AE-CT type tensile tester manufactured by Toyo Seiki Seisakusho Co., Ltd. (Tensile speed 200 mm / min, distance between marked lines 40 mm).

The materials used are as follows.
KF271: Nippon Polyethylene Corporation , low density polyethylene, Tm = 127 ° C., ΔH = 127 J / g, Xc110 = 26%, Xc120 = 23%, MFR = 2.4 g / 10 min, density 913 kg / m ³
SP2040: Prime Polymer Co., Ltd., linear low density polyethylene, Tm = 117 ° C., ΔH = 147 J / g, Xc110 = 28%, MFR = 4.0 g / 10 min, density 920 kg / m ³
UF240: manufactured by Nippon Polyethylene Co., Ltd., linear low density polyethylene, Tm = 123 ° C., ΔH = 136 J / g, Xc110 = 47%, MFR = 2.1 g / 10 min, density 920 kg / m ³
SP2520: Prime Polymer Co., Ltd., linear low density polyethylene, Tm = 121 ° C., ΔH = 154 J / g, Xc110 = 38%, Xc120 = 19%, MFR = 1.7 g / 10 min, density 928 kg / m ³
F-730NV: Prime Polymer Co., Ltd., propylene random copolymer, Tm = 139 ° C., Xc120 = 66%, MFR = 7 g / 10 min SP4530: Prime Polymer Co., Ltd., high-density polyethylene, Tm = 132 ° C., ΔH = 185 J / g, Xc110 = 80%, Xc120 = 72%, MFR = 2.8 g / 10 min, density 942 kg / m ³
KS571: manufactured by Nippon Polyethylene Co., Ltd., ultra low density polyethylene, Tm = 96 ° C., ΔH = 110 J / g, Xc110 = 0%, MFR = 12.0 g / 10 min, density 907 kg / m ³
KF360: manufactured by Nippon Polyethylene Co., Ltd., ultra-low density polyethylene, Tm = 111 ° C., ΔH = 92 J / g, Xc110 = 5%, MFR = 3.5 g / 10 min, density 898 kg / m ³
20200J: Prime Polymer Co., Ltd., linear low density polyethylene, Tm = 120 ° C., ΔH = 137 J / g, Xc110 = 43%, MFR = 18.5 g / 10 min, density 918 kg / m ³
Admer XE070: manufactured by Mitsui Chemicals, maleic anhydride-modified ethylene polymer, MFR = 3 g / 10 min. Molecular sieve: Molecular sieve 4A powder manufactured by Union Showa, D99 = 9.9 μm, D50 = 2 .5μm
Magnesium sulfate-1: pulverized product of dried magnesium sulfate SN-00, manufactured by Umai Kasei Kogyo Co., Ltd., D99 = 3.5 μm, D50 = 1.3 μm
Magnesium sulfate-2: Dry magnesium sulfate SN-00 manufactured by BAI Kasei Kogyo KK, D99 = 118 μm, D50 = 24 μm
LBT-77: Sakai Chemical Industry Co., Ltd. polyethylene wax

For F-730NV and SP4530, the DSC measurement was held at 230 ° C. for 5 minutes, then cooled to −10 ° C. at a temperature drop rate of 10 ° C./min, held at −10 ° C. for 5 minutes, This was performed using a temperature program of heating to 230 ° C. at a rate of temperature increase of ° C./min.

As is apparent from Table 1, the films of the present invention of Examples 1 to 7 are excellent in appearance, film thickness stability and water absorption, and have sufficient heat resistance and strength.

On the other hand, the film of Comparative Example 1 using a propylene-based polymer as the component (A-1) had insufficient dispersion of the water-absorbing filler, remained fine, and had poor film thickness stability. In addition, the film of Comparative Example 2 in which ΔH and Xc110 are too high as the component (A-1) was also insufficient in dispersion of the water-absorbing filler, and remained fine, and the film thickness stability was insufficient. . The film of Comparative Examples 3 and 4 using Tm and / or Xc110 that is too low as the component (A-1) is inferior in heat resistance. As the component (A-1), the film of Comparative Example 5 in which the MFR was too high was insufficient in dispersion of the water-absorbing filler, had fine irregularities, and had poor film thickness stability. The film of Comparative Example 6 in which the amount of the component (A-2) is too large has a very high extrusion load during film formation, the discharge amount becomes unstable, and the film thickness stability is poor. In the film of Comparative Example 7 in which the component (A-2) was not used, the water-absorbing filler was not sufficiently dispersed, and eye grease was generated during film formation, and fine irregularities remained on the film. Film thickness stability was also insufficient. The film of Comparative Example 8 in which the amount of the water-absorbing filler (B) was too large produced holes in every part of the film, and the film thickness stability was insufficient. The film of Comparative Example 9 in which the amount of the water absorbing filler (B) is too small is inferior in the water absorbing function. The film of Comparative Example 10 using a coarse absorbent particle as the water-absorbing filler (B) had very large amounts and insufficient film thickness stability. About Comparative Examples 8 and 10, since the film could not be formed satisfactorily, other tests were not performed.

Examples 8-11
Production of a film having a polyolefin layer as an outer layer:
Polyolefins shown in Table 2 were obtained from the water-absorbent resin composition obtained in Example 1 from a GT-40-24-A type extruder (single screw type, manufactured by Plastic Engineering Laboratory Co., Ltd.) equipped with a vacuum vent. Is extruded from a UT-32-24-A type extruder (single-screw type, manufactured by Plastic Engineering Laboratory Co., Ltd.), and a stack plate type two-layer, three-layer T die (manufactured by Plastic Engineering Laboratory Co., Ltd.) Under the conditions, a three-layer film having a total thickness of 50 μm having a polyolefin layer on both sides of the hygroscopic resin composition layer was produced. The thickness ratio of polyolefin layer / water absorbent resin composition layer / polyolefin layer was 1: 8: 1. About the obtained film, the evaluation test of said (1)-(6) was done. However, regarding the test of (3) above, instead of performing measurement after storage at 25 ° C. for 48 hours, measurement was performed after storage at 25 ° C. for 240 hours. Moreover, regarding the test (4), instead of performing the measurement after 25 ° C. × 2 hours, the measurement was performed after 25 ° C. × 96 hours. The results are shown in Table 2.
T-die outlet resin temperature 220 ° C
Take-off speed 15m / min Chill roll temperature 40 ° C

As is apparent from Table 2, the films of Examples 8 to 11 having a polyolefin layer as an outer layer have a lower water absorption rate than the film of Example 1 having no outer layer. That is, unnecessary water absorption is suppressed. In addition, the heat resistance of the films of Examples 8 to 9, in which Tm and Xc120 within the specific range of the present invention were used as the polyolefin, was further improved than the film of Example 1.

Claims (9)

(A) A film comprising a layer of a water-absorbent resin composition containing 100 parts by mass of a polyethylene-based resin composition and (B) 5 to 200 parts by mass of a water-absorbent filler, wherein the polyethylene-based resin composition (A) is:
(A-1) 99-60 mass% of low density polyethylene or linear low density polyethylene having the following properties (i) to (iv):
(I) The peak top melting point (Tm) on the highest temperature side in the DSC melting curve is 110 ° C. or higher.
(Ii) The heat of fusion (ΔH) in the DSC melting curve is 90 to 180 J / g.
(Iii) Crystallinity (Xc110) at 110 ° C. is 10 to 60%, and (iv) MFR (190 ° C., 21.18N) is 0.1 g / 10 min or more and less than 10 g / 10 min, and
(A-2) Acid-modified resin 1-40 mass%
Where the total amount of component (A-1) and component (A-2) is 100% by weight,
The water-absorbing filler (B) has a particle size (D99) of 30 μm or less and a particle size (D50) of 20 μm or less. Here, D99 and D50 are accumulated from the smaller particle size in the particle size distribution to 99. A film where the particle diameter at the point of mass% and 50 mass% is said. A film comprising a polyolefin layer laminated on both sides of the film according to claim 1. Polyolefin is the following (1)-(2)
The peak top melting point (Tm) on the highest temperature side in the DSC melting curve is 125 ° C or higher, and (2) the crystallinity (Xc120) at 120 ° C is 55% or higher. The film described. The method of using the film of any one of Claims 1-3 for the packaging material of foodstuffs. The method of using the film of any one of Claims 1-3 for the exterior material for secondary batteries. The method of using the film of any one of Claims 1-3 for the hygroscopic material for secondary batteries. A method of using the film according to claim 1 for insoles of footwear. A method of using the film according to any one of claims 1 to 3 for covering clothes. The method of using the film of any one of Claims 1-3 for the packaging material of a test agent.