JPH0827445A - Surface-protecting film - Google Patents

Abstract

PURPOSE:To obtain a surface-protecting film using a polyolefin-based resin film as a substrate and suitably used for applying machining such as drawing. CONSTITUTION:The olefinic resin forming a substrate comprises a propylene- based copolymer copolymerized by a reactor blend method. The propylene-based copolymer contains 30-60wt.% of a rubber component composed of an ethylene- propylene component, and has >=20wt.% of ethylene content in the rubber component and 40-70% crystallinity, 0.885-0.915g/cm<3> density and <=5g MFR/10min.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a metal plate such as a stainless steel plate, an aluminum plate, a colored steel plate or a colored aluminum plate, which is processed, transported or stored, and has dust or scratches on its surface. The present invention relates to a surface protective film which is used to prevent the occurrence of sticking, and is suitable for use when mechanical processing such as drawing is performed in a state of being adhered to an adherend.

[0002]

2. Description of the Related Art Conventionally, as a surface protective film suitable for machining a metal plate or the like, it is mechanically processed while it is temporarily attached to the surface of an adherend. It is required to have machinability in addition to the properties of temporary adhesion and removability. Of the existing films, the soft vinyl chloride resin film is the most suitable material with this machinability, so the soft vinyl chloride resin film formed by extrusion is used as the base material, and one side A method in which a pressure-sensitive adhesive layer is provided and adhered to an adherend, or a polyvinyl chloride sol is directly applied to the adherend to form a dry film is widely used.

However, a film made of a soft vinyl chloride resin has a problem in hygiene and pollution since it emits a toxic gas when it is discarded by incineration after it is used. Hiring has been considered.

For example, Japanese Patent Application Laid-Open No. 53-21239 discloses a technique of using a copolymer obtained by copolymerizing ethylene with an α-olefin having 4 or more carbon atoms as a raw material for a base film. This is so-called linear low-density polyethylene, and its purpose is to utilize the mechanical strength and flexibility of the copolymer resin.

On the other hand, Japanese Patent Publication No. 14265/1989 discloses that
A technique of using a film formed from a blend of polyethylene and polypropylene as a substrate is disclosed. That is, the purpose is to combine the flexibility of polyethylene with the excellent mechanical strength of polypropylene.

[0006]

However, among the surface protective films having the above-mentioned olefin resin film as a base material, those having a base material of a copolymer cannot increase the α-olefin content in the copolymerization stage. Difficult,
The resulting film has excessive flexibility,
On the other hand, when the base material is made of a blend, it is technically extremely difficult to uniformly mix both resins at a predetermined mixing ratio, and it is impossible to obtain a material having desired mechanical properties. was there.

The present invention solves various problems of the above-mentioned surface protective film, and is particularly suitable for use in those subjected to mechanical processing such as drawing, and does not cause problems in hygiene and pollution. It was made for the purpose of providing things.

[0008]

In the surface protective film of the present invention, the olefin resin forming the substrate is a propylene copolymer copolymerized by the reactor blending method. Here, the reactor blending method is a polymerization method in which a plurality of types of polymers can be continuously produced by performing multi-stage polymerization of two or more steps instead of completing the polymerization once. It is a completely different method from the so-called ordinary polymer blending method of obtaining a mixed resin composed of different kinds of polymers using a conventional method, and it is a method of producing a blend type copolymer resin at the molecular level. is there. By finely dispersing the components, the resin thus obtained faithfully embodies the machinability having different properties, which the mixed resins have. A specific manufacturing method is, for example, the method described in JP-A-3-205439.

In the present invention, the propylene-based copolymer has a rubber component comprising an ethylene-propylene component (hereinafter simply referred to as a rubber component) in an amount of 30 to 60% by weight,
The amount of ethylene in the rubber component must be 20% by weight or more. If the rubber component is less than 30% by weight,
This is because breakage is likely to occur during the drawing process, and when it exceeds 60% by weight, it becomes excessively flexible and mechanical strength is generally insufficient, resulting in poor machinability. Further, when the amount of ethylene in the rubber component is less than 20% by weight, the rubber component becomes hard and the bending process becomes difficult, the cold-working followability is poor, and a break occurs during the drawing process.

The propylene-based copolymer used in the present invention has a crystallinity of 40 to 60% and a density of 0.
885 to 0.915 g / cm ³ , and MFR is 5 g / cm ^3.
Must be 10 minutes or less.

When the crystallinity is less than 40%, the elastic modulus of the base material is lowered, so that the initial tensile strength is lowered, and the film is excessively extended at the time of film molding, film sticking and peeling, resulting in moldability, Workability deteriorates, and conversely, the crystallinity is 60
This is because if it exceeds%, the alloy becomes hard and the stress relaxation property becomes poor, and floating occurs during drawing.

[0012] Density mechanical properties decreases in general is less than ^{0.885g / cm 3, 0.915g / cm} 3 cold working follow-up property is deteriorated becomes poor flexibility exceeds, drawing This is because a break sometimes occurs.

If the MFR exceeds 5 g / 10 minutes,
The mechanical properties are generally low, and the workability is reduced due to cutting during bending and elongation during peeling.

When the base material for the surface protective film of the present invention is obtained from the above-mentioned raw materials, the thickness of the base material is usually 30 to 30 although it varies depending on the thickness of the adherend to be applied.
In the case of an adherend having a plate thickness of 1 mm or less, which is 100 μm and is often used in drawing, the thickness is preferably about 30 to 70 μm.

The pressure-sensitive adhesive used in the surface protective film of the present invention may be either rubber-based or acrylic-based as long as it can fulfill the function of the surface-protective film. As a method for forming the agent layer, either a coating method or a coextrusion method can be adopted. The thickness of the pressure-sensitive adhesive layer thus obtained is usually 3
˜50 μm.

In order to enhance the practicality of the surface protection film, a release agent is used on the back surface of the base material, and the soft base material makes the surface less slippery. Other compounds such as low density polyethylene (LDP) may be added to a raw material for laminating another resin layer or forming a base material as long as the effect of the present invention is not impaired.
E), linear low-density polyethylene (LLDPE), high-density polyethylene (HDPE) polypropylene, etc. may be mixed and used within a range of 50% by weight, and additives such as pigments may be optionally used. It is preferable to use a material based on (1) because it is easy to improve other physical properties of the film while reducing the influence on the stress relaxation performance of the film. Further, when the desired copolymer is obtained by the above-mentioned reactor blending method, other α-olefin may be contained in order to impart other functions in the polymerization vessel.

[0017]

The surface protective film of the present invention uses the above-mentioned polyolefin resin as a base material and therefore has various machinability such as bending, punching and drawing. It has become a thing.

[0018]

EXAMPLES Examples of the present invention will be described in detail below.

(Example 1) As a propylene-based copolymer copolymerized by the reactor blending method, KS-021P (trade name, rubber component amount = 45% by weight, ethylene amount in rubber component = 20) manufactured by Highmont Co., Ltd. % By weight, crystallinity = 48%, density = 0.892 g / cm ³ , MFR =
0.8 g / 10 min) was used to mold an olefinic resin film having a thickness of 70 μm by an inflation method, and one side of the obtained film was subjected to corona discharge treatment, and then an adhesive solution (manufactured by Soken Chemical Industry Co., Ltd., A product name AG105) was applied so as to have a dry thickness of 5 μm and dried to obtain a surface protection film sample.

(Example 2) The same propylene copolymer as in Example 1 and polypropylene [AG352 manufactured by Mitsubishi Kasei Co., Ltd.
1 (trade name)] in a weight ratio of 3: 1 (rubber component amount = 34 wt%, ethylene amount = 20 wt% or more, crystallinity = 53%, density = 0.8
A surface protection film sample was obtained in the same manner as in Example 1 except that 93 g / cm ³ and MFR = 2.8 g / 10 min) were used.

(Example 3) The same propylene-based copolymer as in Example 1 was used as the resin for forming the middle layer, and polypropylene [AG3521 (trade name) manufactured by Mitsubishi Kasei Co., Ltd.] was used as the resin for forming the inner and outer layers, and three layers were coextruded. By the inflation method, the thickness composition is 10:50:10 and the total thickness is 70 μm.
m of the olefin resin film was molded, and
A surface protection film sample was obtained in the same manner as in.

(Comparative Example 1) Linear ultra-low density polyethylene [Ultzex 3520 (trade name) manufactured by Mitsui Petrochemical Industry Co., Ltd.] and polypropylene [AG3521 manufactured by Mitsubishi Kasei Co., Ltd.]
(Commercial name)] in a weight ratio of 3: 1 [rubber component amount = less than 3% by weight, ethylene amount = less than 20% by weight, crystallinity = 68%, density = 0.
904 g / cm ³ , MFR = 3.3 g / 10 min] was used, and a sample of the surface protective film was obtained in the same manner as in Example 1.

(Comparative Example 2) Propylene-based copolymer [KS-011P (trade name) manufactured by Highmont, amount of rubber component = 2]
7% by weight, ethylene amount = 20% by weight or more, crystallinity = 7
5%, density = 0.892 g / cm ³ , MFR = 10.0
g / 10 min], a surface protection film sample was obtained in the same manner as in Example 1.

(Comparative Example 3) Propylene-based copolymer [KS-051P (trade name) manufactured by Highmont, amount of rubber component = 5)
0% by weight, ethylene amount = 20% by weight or more, crystallinity = 3
6%, density = 0.890 g / cm ³ , MFR = 0.8 g
/ 10 min] was used to obtain a surface protection film sample in the same manner as in Example 1.

(Comparative Example 4) A propylene-based copolymer [KS-021P (trade name) manufactured by Highmont Co.] and polypropylene [AG3521 (trade name) manufactured by Mitsubishi Kasei Co.] were mixed at a weight ratio of 1: 3. A mixed resin mixed so that [amount of rubber component = 11% by weight, amount of ethylene = 20% by weight or more, crystallinity = 64%, density = 0.899 g / cm ³ ,
A surface protective film sample was obtained in the same manner as in Example 1 except that MFR = 4.5 g / 10 min) was used.

Comparative Example 5 A propylene-based copolymer [KS-021P (trade name) manufactured by Highmont Co.] and a linear low-density polyethylene [Ultox 35 manufactured by Mitsui Petrochemical Co., Ltd.]
20L (trade name)] in a weight ratio of 1: 3, mixed resin [rubber component amount = 11% by weight,
Ethylene amount = 20% by weight or more, crystallinity = 62%, density = 0.923 g / cm ³ , MFR = 3.2 g / 10 minutes)
A sample of the surface protection film was obtained in the same manner as in Example 1 except that was used.

The surface protection film samples obtained in each of the above Examples and Comparative Examples were subjected to bending, punching and drawing, and their machinability was evaluated, and the results are shown. Shown in 1. In addition, in Table 1, in addition, the crystallinity of the resin for forming a film,
The density, MFR, rubber component amount, ethylene amount, etc. are displayed.
The test method and evaluation are as follows.

Bending workability: Each sample was adhered to a stainless plate (thickness: 0.6 mm, # SUS430BA), bent at 90 ° by a press machine, and after cutting and peeling of the film in the vicinity of the bent part after processing. Visually observe the condition of the stainless steel plate. The evaluation was ◎ when no abnormality was observed in the state of the metal plate after cutting and peeling of the film in the vicinity of the bent portion, ⊙ when abnormality was observed in one, × when abnormality was observed in both And

Punching workability: Each sample was attached to the same stainless steel plate as described above, a circular hole having a diameter of 20 mm was punched out by a pressing machine, and the cut surface after punching and the state of the stainless steel plate after peeling were visually observed. The evaluation was rated as ⊚ when no abnormalities were found in both the cut surface and the state of the metal plate after peeling, Δ when abnormalities were found in one, and X when abnormalities were found in both.

Drawability: Each sample was adhered to the same stainless steel plate as above, and formed into a cylinder with a diameter of 30 mm and a depth of 15 m.
m squeezing process and leaving it in a constant temperature room at 40 ° C for 1 day, then visually observing the floating state of the film, and then
Peel off the film and observe if the peeled film is broken. In the evaluation, the floating state of the film was evaluated as ⊚ without floating, and the floating condition was evaluated as ×, and the presence or absence of breakage of the film was evaluated as ⊚ and the broken condition was evaluated as x.

Peeling workability: The film after processing was peeled off, and when it was peeled off cleanly, it was marked with ◯, when it was stretched, it was marked with Δ, and when it was broken, it was marked with x.

[0032]

[Table 1]

As is clear from the results shown in Table 1, in each of the examples, an excellent evaluation was obtained in each machinability, whereas in the case of Comparative Example 1, the amount of the rubber component was extremely small. ,
Lifting or breakage occurs during drawing. In the case of Comparative Example 2, the crystallinity is high, the stress relaxation property is poor, floating occurs during drawing, the MFR is extremely large, the mechanical strength is generally lowered, and the bendability is poor. Also, there are some cuts during drawing. In the case of Comparative Example 3, the crystallinity is low, the bending workability and the punching workability are somewhat poor, and the drawing workability is good, but it is elongated at the time of peeling. In the case of Comparative Example 4, since the amount of the rubber component is small, the stress relaxation property is poor, and the floating occurs during the drawing process, and the cutting also occurs. Further, in the case of Comparative Example 5, since the amount of the rubber component is small and the density is high, the stress relaxation property is poor and the floating occurs during the drawing process, and the cutting also occurs.

[0034]

EFFECTS OF THE INVENTION The surface protective film of the present invention uses the propylene-based copolymer as described above as the polyolefin-based resin for forming the base material, so that the bendability,
It has excellent machinability such as punching workability and drawing workability.

Therefore, it is suitable for use in surface protection of an adherend that has undergone a metal plate processing step, and in particular, for machining. Moreover, since an olefin resin film is used as the base material, there is no problem of toxic gas generation during incineration and temperature dependence is small compared to the one using a soft vinyl chloride resin film as the base material, so the temperature dependence is small. Since there is no need to change or adjust the base material composition due to, and the specific gravity is small, it is possible to increase the product size, and it is also excellent in on-site workability. it can.

Claims (1)

[Claims] 1. A surface protective film having an adhesive layer formed on one surface of a base material made of an olefin resin film, wherein the olefin resin forming the base material is propylene-based copolymerized by a reactor blending method. In the propylene-based copolymer, the rubber component comprising an ethylene-propylene component is 30 to 60% by weight, the amount of ethylene in the rubber component is 20% by weight or more, and the degree of crystallinity is 40-70%, density 0.885-0.91
A surface protective film having a MFR of 5 g / cm ³ and an MFR of 5 g / 10 minutes or less.