JP2730079B2 - Film with excellent low-temperature impact resistance - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a polypropylene film having improved transparency at low temperatures without impairing the transparency, heat blocking properties and seal strength of the polypropylene film itself. It is.

[Prior art] Since a crystalline polypropylene film is excellent in transparency, heat blocking property and seal strength, it can be used alone as a polypropylene film or as a laminate with other various films or as a laminate. It is used for packaging of various articles such as goods or pharmaceuticals.

However, the polypropylene-based film has a problem that the impact resistance, particularly at low temperatures, is low.
To solve this problem, Japanese Patent Application Laid-Open No. Sho 58-210949 discloses a method in which a rubber-like elastomer (ethylene-α-olefin copolymer resin) is mixed with polypropylene and the molecular weight is reduced by using an organic peroxide. JP-A-61-98756 discloses a composition in which polypropylene is blended with linear low-density polyethylene and a soft elastomer.

[Problems to be Solved by the Invention] However, in each of the above techniques, the transparency, heat blocking property, or seal strength decreases as the proportion of an elastomer or linear low-density polyethylene added increases.

Therefore, in the present invention, a polypropylene film excellent in impact resistance at a low temperature without deteriorating transparency, heat blocking property, seal strength and the like was examined.

[Means for Solving the Problems] A film excellent in low-temperature impact resistance of the present invention which can solve the above problems is a polypropylene-based polymer, a plasticizer: 0.2 to 5%, an elastomer: 3 to 20%, Linear low-density polyethylene: It has a gist in that it is composed of one containing 5 to 20%.

[Function] When a plasticizer is added to a polymer substance, a softening point, a glass transition point, an elastic modulus, and the like are lowered, and thermal and mechanical properties are changed. It is believed that this can be explained as follows.

Plasticizers act as lubricants to reduce intermolecular friction.

While the linear polymer tries to form a three-dimensional network structure by the intermolecular force, the plasticizer acts to disturb the structure.

However, the above-mentioned effects of plasticizers on all polymer substances have not been confirmed, and polypropylene has not been confirmed. Accordingly, the present inventors have made various studies to reduce the softening temperature by adding a plasticizer to the polypropylene-based polymer and to improve the flexibility at low temperatures (impact resistance at low temperatures). As a result, it has been found that when 0.2 to 5% of a plasticizer is added, impact resistance at a low temperature is improved. 3-20% elastomer and 5-20% linear low density polyethylene
It was confirmed that the impact resistance at a low temperature became better by the addition of.

The polypropylene-based polymer in the present invention is not particularly limited. In particular, a propylene homopolymer having an MFR (230 ° C.) of 1 g / 10 min to 20 g / 10 min, a propylene-ethylene random or block copolymer having an ethylene content of 10% or less, an ethylene content of 10 % Or less and a butene content of 10% or less in the case of a propylene / ethylene / butene random terpolymer and a composition comprising at least one selected from these, the effect of adding a plasticizer is remarkably exhibited.

The plasticizer to be contained in these polypropylene polymers is not particularly limited, but dimethyl phthalate, diethyl phthalate, dibutyl phthalate, diisobutyl phthalate, diheptyl phthalate, di-2-ethylhexyl phthalate, diisooctyl phthalate , Dicapril phthalate,
Di-n-octyl phthalate, dinonyl phthalate, diisodecyl phthalate, diundecyl phthalate, ditridecyl phthalate, diallyl phthalate, dicyclohexyl phthalate, butyl benzyl phthalate, butyl lauryl phthalate, ethyl phthalyl ethyl glycolate, butyl Phthalates such as phthalylbutyl glycolate, mixtures of the above-mentioned esters of phthalic acid, diethylene glycol dibenzoate, dipropylene glycol dibenzoate,
Octyl oxybenzoate, tri-2-ethylhexyl trimellitate, tri-n-octyl trimellitate,
Aromatic carboxylic esters such as tetra-2-ethylhexyl pyromellitic acid, diisononyl adipate, dicapryl adipate, di-2-ethylhexyl adipate, diisodecyl adipate, di-2-ethylhexyl azelate, dibutyl sebacate, sebacine Acid di-2
-Ethylhexyl, di-2-ethylhexyl tetrahydrophthalate, di-n-octyl tetrahydrophthalate,
Aliphatic dibasic acid esters such as di-2-ethylhexyl hexahydrophthalate and di-2-ethylhexyl dodecane diacid, butyl oleate, butyl stearate, methyl acetyl ricinoleate, dipentaerythritol ester, triacetin, tributyrin, etc. Fatty acid ester derivatives, such as tributyl phosphate, trioctyl phosphate, tricresyl phosphate, octyl diphenyl phosphate, triphenyl phosphate, cresyl diphenyl phosphate, trichloroethyl phosphate, etc., epoxidized soybean oil, epoxidized linseed oil, epoxy stearic acid Epoxy plasticizers such as butyl, octyl epoxystearate, benzyl epoxystearate, di-2-ethylhexyldiisodecyl epoxyhexahydrophthalate, chlorinated paraffins (Cl40
%), Chlorinated paraffin (Cl50%), chlorinated paraffin (Cl70%), chlorine-containing plasticizers such as chlorinated fatty acid methyl, methoxychlorinated fatty acid methyl, and polyester-based plasticizers such as polypropylene adipate and polypropylene sebacate. Other tributyl acetyl citrate, trimethylolpropane trimethacrylate, toluene sulfone-n
-Ethylamide, alkylbenzene, partially hydrogenated terphenyl, camphor and the like.

Desirable properties of the plasticizer include good compatibility with the resin, non-volatility (retention property), good low-temperature flexibility, good plasticization efficiency, and colorlessness, tastelessness, odorlessness, and non-toxicity. It has excellent water resistance and oil resistance, and examples of those satisfying these properties include diisononyl adipate, butyl stearate, and octyl epoxy stearate.

The plasticizer content is 0.2 to 5% based on the total amount of the composition. If it is less than 0.2%, the effect of improving impact resistance at low temperatures is not exhibited, and if it exceeds 5%, heat blocking properties and seam strength are impaired.

In the present invention, the polypropylene-based polymer further contains 3 to 20% of an elastomer and 5 to 20% of a linear low-density polyethylene, whereby the impact resistance at a low temperature is further improved.

Examples of the elastomer include an ethylene-α-olefin copolymer and a propylene-α-olefin copolymer. When the content of the elastomer is less than 3%, the effect of improving the impact resistance at low temperatures is almost nil. If it exceeds, blocking failure occurs. Examples of the linear low-density polyethylene include those in which the carbon chain of the comonomer is C ₄ , C ₆ , C _8, etc. When the content of the linear low-density polyethylene is less than 5%, the impact resistance at low temperatures is improved. Little effect, 20
%, Blocking failure occurs.

[Examples] Hereinafter, the configuration, operation, and effects of the present invention will be described more specifically with reference to Examples, but the present invention is not limited to the following Examples.

The measurement items and evaluation methods shown in the examples are as follows.

Haze (%): Measured using an integrating sphere haze meter manufactured by Nippon Denshoku Industries Co., Ltd. in accordance with JIS-K-6714. The evaluation was based on the ratio of the amount of transmitted turbulent light to the amount of transmitted light.

Impact strength (kg · cm): According to ASTM-D3420, the impact strength was measured with an impact tester equipped with a pendulum having a half-inch hemispherical penetrating part at the tip and freely vibrating and rotating 90 degrees in an arc. For low-temperature impact strength evaluation, set the low temperature to 0.
℃, the standard was 23 ℃.

Heat seal strength (℃ / 1.6kg): Heat gradient type heat sealer manufactured by Toyo Seiki Seisaku-sho, Ltd., pressure 21kg / cm ² × 2
After heat-sealing a sample having a width of 15 mm in seconds, the sealing temperature at which the breaking strength when peeled off was 1.6 kg was measured, and the low-temperature heat sealability was evaluated.

Blocking (g): According to ASTM D1893, the sample was heated to 60 ° C., and was subjected to close contact blocking with a constant load, and a 200 mm wide sample was measured for a peel resistance stress with a 0.25 inch diameter rod.

(Examples and Comparative Columns) The results of examining the physical properties of the polypropylene films having the compositions shown in Table 1 are shown in the same table. The comparative examples are outside the range regulated by the present invention.
However, in Table 1, PHP: propylene homopolymer (melting point: 165 ° C) PERCP: propylene / ethylene random copolymer (melting point: 145 ° C) PEBCP: propylene / ethylene block copolymer (melting point: 158 ° C) PEBRCP: propylene / ethylene / butene random Terpolymer (melting point: 138 ° C) EOSt: Octyl epoxy stearate [Sanso Cider E
6000, Nippon Rika Co., Ltd.] ESO: Epoxidized soybean oil [Sansoizer E2000, Nippon Rika Co., Ltd.] DINA: Diisononyl adipate [Sanso Sizer DINA, Nippon Rika Co., Ltd.] DOA: Adipine Di-2-ethylhexyl acid [Sansosizer DOA, manufactured by Nippon Rika Co., Ltd.] BSt: butyl stearate [ESDIEBS, manufactured by Nippon Rika Co., Ltd.] E-α: Elastomer (ethylene-α-olefin copolymer) , Melting point: 55 ° C) LLDPE: linear low-density polyethylene (melting point: 118 ° C) was used.

As is apparent from Table 1, the impact strength at 0 ° C. of the examples of the present invention is higher than that of the additive-free product, and the low-temperature impact resistance is improved. In addition, haze, heat seal strength, and blocking properties show the same values, indicating that the transparency, heat sealing properties, and blocking properties are not impaired.

[Effects of the Invention] Since the present invention is constituted as described above, a polypropylene film having excellent low-temperature impact resistance can be obtained without impairing transparency, heat sealing properties, and blocking properties.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location C08L 23:16 23:08)

Claims (1)

(57) [Claims] 1. Polypropylene-based polymer containing plasticizer: 0.2 to 5% (meaning by weight, the same applies hereinafter) Elastomer: 3 to 20% Linear low density polyethylene: 5 to 20% A film having excellent low-temperature impact resistance.