JP4991156B2 - Protective film - Google Patents

Description

  The present invention relates to a protective film used for protecting the surface of various industrial members, such as painting and decoration.

  In general, when transporting or storing industrial members such as synthetic resin plates, metal plates, decorative plywood, painted steel plates, etc., members are used to prevent the surfaces of these members from being scratched or contaminated. The method of protecting the member surface by sticking a protective film on the surface is taken.

  For example, as a method of protecting the painted surface of automobile steel plates, the painted surface of automobile steel plates may be damaged during transportation or storage of automobiles by bonding a protective film such as a white polypropylene resin film to the painted surfaces of automobile steel plates. Prevents dirt and dirt.

  When the protective film is used, the adhesive film or adhesive solution is applied to one side of the protective film and dried at a high temperature to provide an adhesive surface on one side. In the drying process of this protective film, if the heat resistance of the protective film is not sufficient, the protective film shrinks to cause wrinkles, and the appearance of the protected surface such as the painted surface of the automobile steel sheet to which the protective film is bonded is inferior. Therefore, a protective film having excellent heat resistance is required.

  As a method of laminating such a protective film, first, a protective film is manually pasted on the surface to be protected, and then, air bubbles (air) caught between the protected surface and the protective film during the manual pasting operation. ) By manually sliding the jig over the surface of the protective film and expelling the bubbles from between the protected surface and the protective film (hereinafter referred to as “bubble expelling work”). ing.

  As such a protective film, Patent Document 1 contains a predetermined amount of a polypropylene block polymer containing a predetermined amount of ethylene propylene rubber, titanium oxide and an ultraviolet stabilizer, a thickness of 150 μm or less, and a yield point of 15. A sheet for protecting a coating film excellent in flexibility, strength, and adhesion to a curved surface has been proposed, which is characterized in that a pressure-sensitive adhesive layer is provided on a support film of ˜50 N / 25 mm.

  However, the coating film protection sheet has a low surface slipperiness during the bubble evacuation operation, and the jig is difficult to slide on the surface of the sheet. There has been a problem that the work man-hours increase and the work volume is greatly reduced.

  In addition, in order to solve the above problem, when the surface of the coating film protection sheet is provided with irregularities, and the coating film protection sheet is given appropriate slipperiness, the surface of the coating film protection sheet is There has been a problem that the matte state is lost and the gloss with a high-class feeling is impaired.

Japanese Patent No. 2832579

  The present invention provides a protective film that is excellent in adhesion to a curved surface portion of a protected surface such as the surface of an industrial member and heat resistance, and that has appropriate slipperiness and high-grade gloss.

The protective film of the present invention comprises 3 to 40% by weight of an ethylene-methyl methacrylate copolymer and 60 to 97% by weight of an ethylene-propylene random copolymer as a polyethylene resin .

The polypropylene resin is limited to an ethylene-propylene random copolymer .

  When the melting point of the polypropylene resin is low, the heat resistance of the protective film becomes insufficient, and the protective film is wrinkled when the pressure-sensitive adhesive (adhesive) applied to the back surface of the protective film is dried. Therefore, it is preferably 135 ° C. or higher, and more preferably 140 to 162 ° C. In addition, the surface of a protective film means the surface where an adhesive (adhesive) is not apply | coated, and the back surface of a protective film is the surface where the adhesive (adhesive) is applied, or the surface where it is applied. Say. The melting point of the polypropylene resin is the melting peak temperature of the DSC curve measured according to JIS K7121, and when there are a plurality of melting peak temperatures, the melting point is the peak temperature with the largest area of the melting curve. .

  On the other hand, if the MFR (melt flow rate) of the polypropylene resin is small, the flexibility and film forming stability of the protective film may be insufficient. On the other hand, if the MFR is large, the mechanical strength of the protective film is insufficient. Therefore, it is preferably 2.0 to 10.0 g / 10 minutes. In addition, MFR (melt flow rate) of the polypropylene resin in the present invention refers to that measured under conditions of 230 ° C. and a load of 21.18 N in accordance with JIS K7210.

  And when there is little content of the said polypropylene resin in the protective film of this invention, heat resistance will become inadequate, and when drying the adhesive (adhesive) apply | coated to the protective film, On the other hand, if the amount is large, the slipperiness of the surface of the protective film is increased, and the workability of expelling air bubbles between the protected surface and the protective film is reduced, so that the weight is 60 to 97 weight. % And is preferably 70 to 95% by weight.

The protective film contains an ethylene-methyl methacrylate copolymer .

  Further, if the MFR (melt flow rate) of the polyethylene resin is small, the flexibility and film-forming stability of the protective film may be insufficient, while if large, the mechanical strength of the protective film is insufficient. Therefore, it is preferably 1.0 to 10.0 g / 10 minutes. In addition, MFR (melt flow rate) of the polyethylene-type resin in this invention says what was measured on condition of 190 degreeC and load 21.18N based on JISK7210.

  And if there is little content of the said polyethylene-type resin in the protective film of this invention, while the lubricity of the surface of a protective film will become high and workability | operativity of a bubble chasing work will fall, on the other hand, if it is large, the heat resistance of a protective film Becomes insufficient, and when the pressure-sensitive adhesive (adhesive) applied to the back surface of the protective film is dried, wrinkles are likely to occur in the protective film, so it is limited to 3 to 40% by weight, and 5 to 30%. % By weight is preferred.

  In addition, in the protective film of this invention, if the polypropylene resin and polyethylene resin of the ratio mentioned above are contained, within the range which does not impair the physical property, thermoplastics other than the above-mentioned polypropylene resin and polyethylene resin A resin may be contained. Such a thermoplastic resin is not particularly limited, and examples thereof include low density polyethylene, medium density polyethylene, high density polyethylene, and linear low density polyethylene.

  When the bending elastic modulus of the protective film of the present invention is small, the protective film becomes too soft and the workability may be lowered. On the other hand, when the protective film is large, the followability to the uneven shape of the protected surface may be deteriorated. Therefore, it is preferable that it is 100-1500 MPa. In addition, the bending elastic modulus of a protective film says what was measured based on ASTMD790.

  And if the glossiness of the surface of the protective film of the present invention is small, the glossiness of the protective film may be insufficient and the appearance may be deteriorated. On the other hand, if the glossiness is large, the surface of the protective film becomes highly slippery. Thus, the workability of the bubble evacuation work may be reduced, so 40 to 60% is preferable, and 45 to 60% is more preferable. In addition, the glossiness of the surface of a protective film means what was measured using the glossiness meter on the conditions whose incident angle and light-receiving angle are 45 degrees based on JISK7105.

  In the protective film of the present invention, for the purpose of imparting heat resistance to the film, a heat-resistant layer made of a polypropylene resin may be laminated and integrated on the surface side. In this case, it is preferable that the bending elastic modulus and the glossiness of the surface of the protective film in which the heat-resistant layers are laminated and integrated are within the above-described ranges.

  Although it does not specifically limit as polypropylene resin which comprises the said heat resistant layer, For example, a polypropylene, an ethylene-propylene random copolymer, an ethylene-propylene block copolymer etc. are mentioned, An ethylene-propylene random copolymer is preferable. .

  In addition, when the heat-resistant layer made of polypropylene resin is laminated and integrated on the surface side of the protective film as described above, a polyethylene-based material is provided between the protective film and the heat-resistant layer for the purpose of imparting flexibility to the protective film. A flexible layer made of resin may be integrated as an intermediate layer.

  And as a polyethylene-type resin which comprises the said flexible layer, although it does not specifically limit, For example, a low density polyethylene, a medium density polyethylene, a high density polyethylene, a linear low density polyethylene, an ethylene vinyl acetate copolymer, ethylene- (Meth) acrylic acid copolymer, ethylene- (meth) acrylic acid ester copolymer, etc. are mentioned, and ethylene- (meth) acrylic acid copolymer and ethylene- (meth) acrylic acid ester copolymer are preferable.

  In addition, you may add additives, such as a plasticizer and a pigment, to the said protective film in the range which does not impair the physical property.

  On the other hand, if the thickness of the protective film is thin, the mechanical strength of the protective film may be insufficient. On the other hand, if the thickness is thick, the flexibility of the protective film is reduced, and the protective film is applied to the surface to be protected. The workability at the time of combining may decrease, and the material used to form the protective film may increase, resulting in poor resource saving. In addition, the thickness of a protective film means what was measured using the dial gauge based on JISK7130.

  Next, the manufacturing method of a protective film is demonstrated. Although it does not specifically limit as a film forming method of the protective film of this invention, For example, a T-die method, an inflation method, an extrusion laminating method etc. are mentioned, T-die method is preferable.

  And in order to be able to bond the protective film formed into a film by the above methods to a to-be-protected surface, an adhesive (adhesive) is apply | coated to the back surface of a protective film, 70-130 degreeC, 5 Dry for ~ 300 seconds.

  The pressure-sensitive adhesive is not particularly limited. For example, (meth) acrylic pressure-sensitive adhesive, polyisobutylene-based pressure-sensitive adhesive, butyl rubber-based pressure-sensitive adhesive, hydrogenated styrene-butadiene-based pressure-sensitive adhesive, etc. have excellent weather resistance. The polyisobutylene-based pressure-sensitive adhesive is preferable.

  Furthermore, if the wettability of the back surface of the protective film of the present invention is low, the applied adhesive (adhesive) may be repelled, so the surface tension of the back surface of the protective film may be 36 mN / mm or more. Preferably, it is 38-45 mN / mm. In addition, as a method for adjusting the surface tension of the back surface of the protective film, surface wettability improving treatment such as corona discharge treatment is preferable.

The protective film of the present invention comprises 3 to 40% by weight of an ethylene-methyl methacrylate copolymer as a polyethylene resin and 60 to 97% by weight of an ethylene-propylene random copolymer as a polypropylene resin. . Therefore, since the protective film has excellent heat resistance, when the pressure-sensitive adhesive (adhesive) applied to the protective film is dried, the protective film shrinks and causes wrinkles. No appearance and excellent appearance.

  Moreover, since the protective film of the present invention has the above-described configuration and has excellent flexibility, the work when the protective film is manually pasted on a protected surface such as a painted surface of an automobile steel plate. In addition to excellent properties, it also has excellent adhesion to the curved surface portion of the protected surface. Therefore, according to the protective film of the present invention, when the protective film is manually attached to the protected surface, the protective film can be adhered exactly along the shape of the protected surface. It is possible to reduce bubbles (air) biting into the.

  Furthermore, since the protective film has moderate slipperiness, when the protective film is manually attached to the protective film, when the air bubble caught between the protected surface and the protective film is expelled by the jig, the jig is the protective film. There is almost no difficulty in working due to excessive sticking or slipping on the surface. Therefore, according to the protective film of the present invention, the protective film can be beautifully attached to the protected surface with a small number of work steps, so that the workability of the protective film bonding work can be improved. Work volume can be increased.

  Moreover, the protective film has a profound gloss, and the finished surface to which the protective film is bonded has a beautiful gloss with a high-class luster. It is suitably used for the protection of surface painting and decoration.

  Hereinafter, embodiments of the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples.

Example 1
An extruder having a T-die disposed at the tip was prepared, and an ethylene-propylene random copolymer (trade name “Sun Aroma” manufactured by Sun Allomer Co., Ltd., ethylene content: 3.5% by weight, melting point: 141 ° C. was used in this extruder. , MFR: 7.0 g / 10 min) 90 parts by weight, ethylene- methyl methacrylate copolymer (trade name “Acrylift” manufactured by Sumitomo Chemical Co., Ltd., methyl methacrylate content: 10 wt%, MFR: 2.0 g / 10 min) 10 parts by weight, and 15 parts by weight of a white pigment masterbatch (titanium oxide content: 60% by weight, low density polyethylene content: 40% by weight) made of titanium oxide and low density polyethylene were supplied and heated, melted and kneaded. Then, a protective film having a thickness of 45 μm was obtained by extrusion film formation from a T die.

(Example 2)
65 parts by weight of ethylene-propylene random copolymer (trade name “Sun Allomer” manufactured by Sun Allomer Co., Ltd., ethylene content: 3.5 wt%, melting point: 141 ° C., MFR: 7.0 g / 10 min), ethylene- methyl methacrylate In the same manner as in Example 1, except that the copolymer (trade name “Acrylift” manufactured by Sumitomo Chemical Co., Ltd., methyl methacrylate content: 10 wt%, MFR: 2.0 g / 10 min) was 35 parts by weight, A protective film having a thickness of 45 μm was obtained.

(Comparative Example 1)
40 parts by weight of ethylene-propylene random copolymer (trade name “Sun Allomer”, manufactured by Sun Allomer Co., Ltd., ethylene content: 3.5 wt%, melting point: 141 ° C., MFR: 7.0 g / 10 min), ethylene- methyl methacrylate In the same manner as in Example 1, except that the copolymer (trade name “Acrylift” manufactured by Sumitomo Chemical Co., Ltd., methyl methacrylate content: 10 wt%, MFR: 2.0 g / 10 min) was 60 parts by weight, A protective film having a thickness of 45 μm was obtained.

(Comparative Example 2)
100 parts by weight of ethylene-propylene random copolymer (trade name “Sun Allomer”, manufactured by Sun Allomer Co., Ltd., ethylene content: 3.5 wt%, melting point: 141 ° C., MFR: 7.0 g / 10 min), ethylene- methyl A protective film having a thickness of 45 μm was obtained in the same manner as in Example 1 except that the methacrylate copolymer was not added.

(Comparative Example 3)
In the same manner as in Comparative Example 2, the film is extruded from a T-die disposed at the tip of the extruder, and then the molten film immediately after extrusion is passed between a metal roll and a rubber roll. The protective film having a thickness of 45 μm having an embossed surface was obtained by narrowing the pressure. In addition, the surface roughness of the obtained protective film was 0.8 micrometer in centerline average roughness (Ra).

  By applying a corona treatment to the back surface of the protective film obtained as described above, and subsequently applying a polyisobutylene-based adhesive solution (toluene: 20% by weight) to this surface and drying at 80 ° C. for 3 minutes. The pressure-sensitive adhesive layer was laminated and integrated on the back surface of the protective film. And the glossiness of these protective films, heat resistance, lubricity, and external appearance were evaluated in the way shown below, and those results were shown in Table 1.

(Glossiness)
In accordance with JIS K7105, the glossiness of the surface of the obtained protective film was measured using an glossiness meter (trade name “Digital Variable Glossiness Meter UGV-6P” manufactured by Suga Test Instruments Co., Ltd.). Measurements were made with both angles set at 45 °.

(Lubricity)
A protective film is attached to a 1 m ² metal plate so that the adhesive is in contact with the metal plate, and the surface of this protective film is a wooden jig having a flat rectangular shape with a pressing surface of 1 cm in length and 30 cm in width. Sensory evaluation of the sliding of the jig at the time of rubbing was performed, and the slipperiness was evaluated according to the following criteria.
○: The jig was able to be rubbed smoothly without excessively sticking or slipping on the surface of the protective film.
X: The jig could not be rubbed well because it struck too much on the surface of the protective film or slipped too much.

(Heat-resistant)
As described above, the protective film immediately after drying the pressure-sensitive adhesive applied to the back surface of the protective film was visually observed, and the protective film had no wrinkles, and the protective film had wrinkles Was evaluated as x.

(Appearance)
The gloss of the surface of the obtained protective film was visually observed, and the appearance was evaluated according to the following criteria.
○: A thick gloss was observed on the surface of the protective film.
Δ: Some gloss was observed on the surface of the protective film.
X: Gloss was not seen on the surface of the protective film.

Claims (2)

A protective film comprising 3 to 40% by weight of an ethylene-methyl methacrylate copolymer as a polyethylene resin and 60 to 97% by weight of an ethylene-propylene random copolymer as a polypropylene resin. 2. The protective film according to claim 1, wherein the glossiness of the surface is 40 to 60%.