JPH0511550B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention is particularly suitable for unstretched films, and particularly provides a propylene copolymer that has significantly improved slipperiness after high-temperature aging of multilayer films, and has good transparency and heat sealability. The present invention relates to a film made of a resin composition. [Prior Art] In general, unstretched polypropylene films are made of polypropylene, which has excellent properties such as transparency, heat resistance, moisture resistance, mechanical properties, and gloss, as well as excellent smoothness. Because of this, it is widely used in the packaging field as a single-layer film or multi-layer film. This multilayer film includes a film in which a propylene copolymer resin is laminated as a heat seal layer on the surface of a polypropylene base material using a coextrusion method, and a polypropylene base film and a propylene copolymer resin surface layer film are laminated by elution extrusion of polyethylene. There are films in which layers are laminated, and films in which biaxially stretched polypropylene or nylon is used as a base film and a propylene copolymer resin film is dry laminated using an adhesive. The first quality required for such an unstretched polypropylene film is that it has low-temperature heat sealability. With the recent increase in packaging speed due to high-speed automatic packaging, sealing temperature control has become particularly important when laminating with highly heat-shrinkable films. The second reason is that the film is highly slippery. If the film's slipperiness is insufficient, it not only reduces the processing speed in high-order processing processes such as bag making, but also makes it difficult to handle the processed product, such as problems with opening the bag, and greatly impairs work efficiency. Therefore, slipperiness is one of the important required characteristics. In addition, good anti-blocking properties and no deterioration in transparency due to changes over time are listed. Conventionally, known methods for imparting slipperiness to propylene polymers for films include adding organic fatty acid amides such as stearic acid amide and erucic acid amide, and adding inorganic compounds such as silica and talc. ing. [Problems to be Solved by the Invention] However, poor slip properties often occur in multilayer films, especially dry laminated films. That is, in the case of dry lamination, for example, a solution containing an adhesive is applied to a base material layer such as a biaxially oriented polypropylene film, and after drying the solvent, an unoriented propylene polymer film is adhered to the coated surface. A multilayer film is manufactured using the following steps. At this time, it is preferable to perform aging at a high temperature to shorten drying time and increase adhesive strength.
Since aging significantly deteriorates slipperiness, the current temperature must be limited to 35°C or less. Therefore, improvement in this respect is strongly desired. [Means for Solving the Problems] The present invention has found that the above-mentioned drawbacks can be solved by using a composition for films in which a specific silicone resin powder is blended in a fixed amount with a specific propylene copolymer resin. This is what was done. That is, the present invention provides a non-melting type having a three-dimensional network structure with an average particle size of 0.5 to 7 microns in 100 parts by weight of a propylene-α-olefin copolymer resin with a melting peak temperature of 145°C or less as determined by the DSC method. A propylene copolymer film characterized in that an unstretched film made of a composition containing 0.01 to 0.5 parts by weight of silicone resin powder is laminated on a base film via an adhesive layer. [Function] The propylene-α-olefin copolymer resin used in the present invention has a melting peak temperature of 145 by the DSC method.
℃ or below. Here, α-olefin is
Ethylene, butene-1, pentene-1, 4-methylpentene-1, hexene-1, octene-1, etc. having carbon atoms of 10 or less, and one or more types as a copolymerization component with the majority of the weight of propylene. can be used. Preferred copolymer resins include a propylene-ethylene random copolymer and a propylene-ethylene-butene-1 random copolymer, which have appropriate heat sealability. The melt flow rate (MFR) of these copolymer resins may be as long as they can be molded, but usually 0.5 to 100 g/10 minutes, especially 1 to 50 g/10 minutes,
Particularly preferred is 3 to 30 g/10 minutes. In addition, those whose melting peak temperature exceeds 145℃,
Low-temperature heat sealability is poor and it cannot be put to practical use. In addition, the non-melting silicone resin powder used in the present invention is a silicone resin powder that has a three-dimensional network structure due to siloxane bonds, and organic groups that bond to silicon include fatty acids such as methyl groups and ethyl groups. Examples include a group hydrocarbon group, an aromatic hydrocarbon group such as a phenyl group, and an unsaturated hydrocarbon group having a vinyl group. Among them, methyl group is preferred. In addition, various modified silicone resin powders can also be used as long as they do not impair the effects of the present invention. Silicone resin is generally available as a silicone varnish made by dissolving an initial condensate in a suitable solvent, but the silicone resin used in the present invention has an average particle size of 0.5 to 7 microns (μ ), and is a substantially insoluble and infusible substance that has been heat-cured. In addition, the shape of the silicone resin powder used in the present invention has a sphericity f expressed by the following formula (1).
Those having a sphericity of 0.8 or more, especially those having a sphericity of 0.85 or more and an average particle size in the range of 1 to 5 μm are preferable. f=√(4)/Dmax (1) (Here, A is the cross-sectional area of the polymer powder in mm ² and Dmax is the longest diameter of the same cross-section in mm.) The sphericity of the silicone resin powder can be determined by the following method. by. That is, the powder is placed on an electron microscope grid covered with a collodion support film, and observed and photographed at an appropriate magnification. The obtained photograph is processed with an image analyzer, and the sphericity f is determined using the above equation (1). The value of sphericity given by this formula is 0 to 1
, and a true sphere is 1. Sphericity particularly affects slipperiness. If the average particle size of the silicone resin powder exceeds 7μ, the transparency of the film will deteriorate;
If it is less than 1, the effect of improving slipperiness will be reduced. This special silicone resin powder is commercially available (for example, Toshiba Silicone Co., Ltd. “Tospearl”, Toray Silicone Co., Ltd.
Silicone Co., Ltd. "Trefoil" etc.) can be selected and used. The blending ratio of the propylene-α-olefin copolymer and silicone resin powder used in the present invention is as follows:
0.01 to 0.5 parts by weight of silicone resin powder per 100 parts by weight of propylene-α-olefin copolymer;
Preferably it is 0.03 to 0.3 parts by weight. If the amount of silicone resin powder blended is less than 0.01 parts by weight, it is impossible to impart slipperiness to the film, and if it exceeds 0.5 parts by weight, although sufficient slipperiness is provided, the transparency of the film is impaired. This is not desirable because The amount to be added may be set within the above range depending on the use of the film and the type of the propylene copolymer. As for the addition method, mixing may be performed for a predetermined time using a commonly used mixer such as a Henschel mixer, a V blender, or a ribbon blender. Usually, the composition is prepared using a general kneading machine prior to film forming. The blending ratio of the silicone resin powder may be determined by blending the desired amount at once or by blending a larger amount than the desired amount and diluting it with a propylene copolymer during film molding to form a so-called master batch. Furthermore, in the present invention, in addition to the above-mentioned essential components, stabilizers used for ordinary polyolefins, processing aids, and inorganic compounds such as silica and talc can be added for the purpose of improving the blocking and slipping properties of the film. . Particularly preferred lubricants as additional components include aliphatic amides having 18 or more and 22 or less carbon atoms, among which saturated fatty acid amides such as stearic acid amide and behenic acid amide are preferred. Further, the amount of these lubricants added is preferably within a range not exceeding 0.20 parts by weight per 100 parts by weight of the propylene polymer. As a film forming method, conventional forming methods are applied, and the T-die method is generally used. Suitable base films used for lamination include biaxially oriented polypropylene films, biaxially oriented nylon films, biaxially oriented polyester films, etc. as shown in Examples below. Lamination methods include a method in which melt-extruded layers of polyethylene or the like are laminated as an adhesive layer, and a method in which commercially available adhesives are combined and dry laminated. The present invention exhibits more remarkable effects in a lamination method using dry lamination. In addition, in the dry lamination method, adhesive is applied to the base film using a roll such as a gravure roll, and after the solvent is dried in a drying oven,
A common method is to bond unstretched films together on a heated metal roll. At this time, the adhesive used is, for example, vinyl, acrylic, polyamide, epoxy, urethane, or the like. [Example] Evaluation method (1) Transparency: Measured by stacking four films in accordance with ASTM-D1003. (2) Slip property: Compliant with ASTM-D1894 static friction coefficient measurement method. (3) Melting peak by DSC method: Using PerkinElmer DSC, take a sample amount of 5.0 mg,
After holding at 190°C for 3 minutes, crystallize at a cooling rate of 10°C/min to 50°C, and then melt at a heating rate of 10°C/min. Evaluate by the melting peak temperature. Examples 1 to 3, Comparative Examples 1 and 2 Propylene-ethylene random copolymer (ethylene content 4.5% by weight, melting peak temperature 137.5°C,
MFR6.0g/10min) 100 parts by weight, 2,6-di-t-butyl-p-cresol as an antioxidant
0.15 parts by weight of hydrochloric acid, 0.05 parts by weight of calcium stearate as a catch agent, and various additives shown in Table 1 (silicone resin powder manufactured by Toshiba Silicone Co., Ltd.) were added, and after mixing, the mixture was pelletized. The obtained pellets were extruded through a 35 mm diameter T-die at a molding temperature of 230° C. to produce an unstretched single-layer film with a thickness of 30 μm. The wet tension on one side of this film is 40dyn/cm
A corona discharge treatment was carried out so that the temperature of the sample was maintained, and aging was carried out for 2 days in an atmosphere of 40°C. Next, a 25μ biaxially stretched polypropylene film was used as the base layer film, and a urethane-based two-component reactive adhesive was applied, followed by dry lamination with the corona discharge treated surface of the single layer film obtained earlier. carried out,
Aging was performed for 3 days in an atmosphere at 45°C. Slip properties were measured on the single-layer film before dry lamination, which was aged at 40°C for 2 days, and on the multilayer film, which was aged at 40°C for 3 days after dry lamination, without corona discharge treatment. did. For transparency, the single layer film was heated at 40°C.
The measurement was performed on a film before dry lamination that had been aged for two days in an atmosphere of

[Table] Examples 4 and 5, Comparative Example 3 Propylene-ethylene-butene-1 as resin
Random copolymer (ethylene content 2.0% by weight,
Butene-1 content 12.5% by weight, melting peak temperature
131.0° C., MFR 5.5 g/10 minutes), the pellets were formed into pellets according to the formulation shown in Table 2, and an unstretched film was prepared in the same manner as in Example 1. Next, dry lamination was performed using a biaxially oriented nylon film (15μ) and a biaxially stretched polyester film (12μ) as the base material layer to be dry laminated, and evaluation was performed in the same manner as in Example 1. Comparative Example 4 Example 1 except that 0.8 parts by weight of dimethyl silicone oil with a viscosity of 200 centistokes (25°C) was used instead of the silicone resin used in Example 1.
I tried to make pellets in the same way as above, but the pulsation was so intense that I couldn't make pellets with a uniform shape. Further, although an unstretched film with a thickness of 30 μm was formed using this pellet, the pulsation was still severe and a film with a uniform thickness could not be obtained.

[Table] ** Biaxially Stretched Film [Effects of the Invention] The present invention has particularly good slipperiness after high-temperature aging treatment of a multilayer film, and there is no aging temperature limit of 35°C or less as in the past. It is a film that can achieve practical adhesion strength between multiple layers in a short time, and has good transparency and heat sealability.

Claims (1)

[Scope of Claims] 1. A non-melting type having a three-dimensional network structure with an average particle size of 0.5 to 7 microns in 100 parts by weight of a propylene-α-olefin copolymer resin whose melting peak temperature is 145°C or less according to the DSC method. silicone resin powder
1. A propylene copolymer film characterized in that an unstretched film made of a composition containing 0.01 to 0.5 parts by weight is laminated with a base film via an adhesive layer. 2. The film according to claim 1, wherein the propylene-α-olefin copolymer resin is a propylene-ethylene random copolymer resin or a propylene-ethylene-butene-1 random copolymer resin. 3. The film according to claim 1, wherein the non-melting silicone resin powder has a sphericity f expressed by the following formula (1) of 0.8 or more. f=√(4)/Dmax (1) (Here, A is the cross-sectional area of the polymer powder in mm ² and Dmax is the longest diameter of the same cross-section in mm.)