JPS61195837A - Laminated polypropylene film - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention (a) Industrial Application Field The present invention relates to a laminated polypropylene film that has excellent tearability, good writability and matte properties, and more specifically, a laminated polypropylene film that is easy to cut by hand and with a dispenser. The present invention relates to a laminated polypropylene film that is useful as a base material for adhesive tapes that require the following, particularly adhesive tapes for drafting repair.

(b) Conventional technology Polypropylene film is widely used as a packaging material due to its excellent mechanical properties, chemical properties, transparency, etc. However, due to its excellent mechanical properties, it cannot be easily torn by hand. That is difficult.

On the other hand, with the aim of applying it as a base material for adhesive tapes and the like that require cutability by hand and dispenser, for example, a method of imparting tearability to a polypropylene film by stretching and orienting it, and a method of imparting tearability to brittle resins such as polystyrene have been developed. A method of imparting tearability to a polypropylene film by mixing it with the polypropylene film has been proposed.

However, these conventional techniques are not satisfactory in terms of the balance between rigidity, tensile strength, and manual tearability that are practically required for films.

Furthermore, the surface of the polypropylene film has a mirror-like luster and cannot be marked with a pencil or the like.

(Problems to be Solved by the Invention The purpose of the present invention is to provide a polypropylene film that provides guidance requirements that conventional polypropylene films could not meet and that also has excellent writability, matte properties, etc. This was done as a.

2) Means for Solving the Problems The laminated polypropylene film of the present invention will be described in detail below. The laminated polypropylene film of the present invention is made of polypropylene, and the intermediate layer contains 10 to 40% by weight of petroleum resin. , at least one of both surface layers contains 15 to 50% by weight of an inorganic filler; one surface layer is biaxially stretched;
and the other surface layer is uniaxially stretched.

Polypropylene in the present invention includes not only propylene homopolymers but also copolymers with ethylene, butene-1, etc.

In addition, petroleum resins contained in the polypropylene of the intermediate layer include aliphatic, alicyclic, aromatic, etc., but from the viewpoint of compatibility with polypropylene and heat resistance, ring-based petroleum resins are used. Preferably XA.

These petroleum resins are contained in an amount of 10 to 40% by weight, preferably 20 to 30% by weight, based on the total amount with polypropylene.

Oil 4 in the middle j-! If the fat content is less than 10% by weight, the requirements for laminated polypropylene film production are insufficient, and if it exceeds 40% by weight, it will tear too easily and the formation of laminated polypropylene films (described later) will be insufficient. Cutting occurs frequently during the stretching process.

In addition, the inorganic fillers contained in at least one layer of the polypropylene of both surface layers include calcium carbonate, talc,
Clay, zeolite, etc., which are usually used in polyolefins, are used.

These inorganic fillers are contained in an amount of 15 to 50% by weight, preferably 20 to 40% by weight, based on the total amount with polypropylene.

If the content of the inorganic filler in the surface layer is less than 15% by weight, the writing and matte properties of the laminated polypropylene film will be insufficient, and if it exceeds 50wts, the strength will be weakened and the laminated polypropylene film will not have sufficient strength. Cutting tends to occur during molding (stretching process described later).

In addition, when the laminated polypropylene film is particularly required to have whiteness, these inorganic fillers can be added to the intermediate layer depending on the degree of whiteness.

In the laminated polypropylene film of the present invention having the above-mentioned 14 structures, one surface layer is double-stretched, the intermediate layer and the other surface layer are uniaxially stretched, and both the intermediate layer and both surface layers are double-stretched. If it is axially stretched, it cannot be easily torn by hand.

The laminated polypropylene film is produced by a conventional sequential biaxial stretching method. Specifically, polypropylene containing or not containing an inorganic filler is melt-extruded from a T-die, solidified with a cooling roll, and then stretched 5 to 9 times in the machine direction at a stretching temperature of 120 to 150°C. Then, a coextrusion of polypropylene containing petroleum resin without or containing an inorganic filler is laminated onto this longitudinally stretched film so that the polypropylene containing petroleum resin forms an intermediate layer. The film is stretched 8 to 12 times in the transverse direction using a tenter at a stretching temperature of 160 to 190°C and heat set. In addition, stretching in the longitudinal direction can be carried out in multiple stages, and in that case, stretching can be carried out again in the longitudinal direction after the transverse stretching.

In addition, when molding a laminated polypropylene film containing an inorganic filler only on one surface, it is preferable from the viewpoint of stretching stability that the surface layer containing the inorganic filler be the side to be uniaxially stretched. .

In addition, to the polypropylene of each 1-, other thermoplastic resins and additives such as antistatic agents, slip agents, and antioxidants, and when containing inorganic fillers, their dispersants may be added. I can do it.

The thickness of each 1 m layer in the laminated polypropylene film of the present invention is such that the ratio of the biaxially stretched surface layer, the uniaxially stretched intermediate layer, and the uniaxially stretched surface layer is 1:2 to 10.
: A range of 0.5 to 1.5 gives particularly favorable results.

((e) Effect) The laminated polypropylene film of the present invention has the above-described structure, which gives it excellent hand-manufacturability, and at the same time, since it contains an inorganic filler in the surface layer, it has good writability and matte properties. It has the following.

(f) Examples Example 1. 2. Comparative Example 1.2 Melt Index 4. Of/10 minutes polypropylene (manufactured by Mitsubishi Yuka Co., Ltd., Mitsubishi Noprene) and calcium carbonate were each blended composition shown in Table 1 and stretched 7 times in the longitudinal direction.

This longitudinally stretched film was coated with polypropylene with a melt index of 2.3 f/10 min (manufactured by Mitsubishi Yuka Co., Ltd.) containing 25 weight liters of alicyclic hydrogenated petroleum resin (selected by Arayo Kagaku Co., Ltd., Alcon P-1251). , Mitsubishi Noblen F'L6CK) was laminated with the same blended composition as before so that it would become the intermediate layer.At this time, the thickness of the intermediate layer was 0-2.
mm, and the thickness of the surface layer was 0.05+w.

This three-layer film is passed through a tenter and stretched to a stretching source 1.
Jj After stretching 10 times in the transverse direction at 170°C, heat setting at 175°C, consisting of a biaxially stretched surface layer, a uniaxially stretched intermediate layer, and a uniaxially stretched surface layer, each layer having a thickness of 5
Three-layer laminated polypropylene films of μ, 20μ, and 5μ were manufactured.

These films have h lengthwise and widthwise dimensions. On the other hand, 41! The evaluation results of the stretchability of the film at the time of manufacture, the pencil writability and matteness (gloss) of the obtained film on the biaxially stretched layer side are as shown in the following table.

Comparative Example 3 A coextruded three-layer laminate made of the same materials used in Example 1 was heated 7 times in the machine direction at 140°C and 10 times in the transverse direction at 175°C.
Biaxially stretched three-layer laminated polypropylene film with the same thickness composition ratio as Example 1 after being stretched twice!!
! ! a L 7'C0 Although the writing properties and matte properties of this film were good, it was difficult to tear it by hand in both the vertical and horizontal directions.

Comparative Example 4 Same as Example 1 except that the content of petroleum resin in the intermediate layer was 5% by weight. It has excellent writing properties and matte properties, and is particularly useful as a base material for adhesive tapes and the like.

Patent applicant: Mitsubishi Yuka Co., Ltd. Agent: Patent Attorney Hidetoshi Furukawa (1 other person)

Claims (1)

[Claims] A three-layer laminate of polypropylene, the middle layer containing 10 to 40% by weight of petroleum resin, and at least one of both surface layers containing 15 to 50% by weight of inorganic filler;
A laminated polypropylene film characterized in that one surface layer is biaxially stretched, and the intermediate layer and the other surface layer are uniaxially stretched.