JPH0872191A - Surface protective film - Google Patents

Abstract

PURPOSE: To improve heat resistance, cold resistance, transparency, scuff resistance, tensile strength, strength at yield point, drawing processability, punching processability, cutting properties, curling resistance and adhesive properties by mixing specific two types of polyolefins with ultra-low density ethylene-α- olefin copolymer at a specific ratio. CONSTITUTION: 100 pts.wt. of ultra-low density ethylene-a-olefin copolymer having a density of 0.885-0.910g/ml, a melt index of 0.1-3g/l0min, a melting point of 116 deg.C or more and 12-20wt.% of α-olefin content is prepared. 10-100 pts.wt. of ethylene-vinyl acetate copolymer having 30-25wt.% of vinyl acetate content manufactured by a high-pressure radical polymerization method, a melt index of 0.3-5g/10min is prepared. Further, 10-100 pts.wt. of polypropylene having a density of 0.9-9.01g/ml, a melt flow rate of 3-30g/10min is prepared. These three types of specific resin compositions are molded.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a surface protective film. More specifically, the present invention relates to a surface protective film having a pressure-sensitive adhesive layer provided on a film made of an ultra-low density linear ethylene-α-olefin copolymer, ethylene-vinyl acetate copolymer and polypropylene, The film is excellent in heat resistance, cold resistance, transparency, scratch resistance, tensile strength, yield strength, drawing workability, punching workability, cuttability, curl resistance, etc., and is a metal plate, glass plate, wood decorative plate. It is also used as a surface protection film for plastic plates and the like.

[0002]

2. Description of the Related Art Conventionally, aluminum plate, stainless plate,
Steel plates, glass plates, engineering plastic plates, acrylic glass plates, wood decorative plates, etc. are generally surface-protective films or sheets having temporary adhesive properties in order to prevent surface contamination and external damage during storage, transportation or secondary processing. Affixed to the surface of.

As the surface protective film (sheet), a thin paper such as kraft paper to which an adhesive having a weak adhesive force was applied was used at first, but the paper is opaque and protected. The color, pattern, and other design features of the article to be processed cannot be confirmed through the surface protective film (sheet), and there is a drawback in that it is inconvenient in use, inventory control, and processing.

Next, vinyl chloride resins are inexpensive, have high transparency, have a film flexibility, and have excellent handleability, and also have excellent tensile strength, yield point strength, and scratch resistance. It has excellent secondary workability (bending, two-step drawing, punching) and has been used in large quantities. However, vinyl chloride resins have low cold resistance, are difficult to bond in winter, and generate chlorine during incineration, so there is concern over pollution in recent years, and substitution with other materials is being considered. .

As a material which does not show opacity, low cold resistance, chlorine generation upon incineration, which are the drawbacks of paper and vinyl chloride resins, high-pressure low density polyethylene, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate. Copolymer,
Linear low-density ethylene with a density of 0.910 g / ml or more
α-Olefin copolymers, high-density polyethylene, polypropylene and the like are used as surface protection films (sheets). However, the high-pressure low-density polyethylene has low tensile strength, the ethylene-vinyl acetate copolymer has low heat resistance, the film is not stiff, the ethylene-ethyl acrylate copolymer is expensive, and the cost rises. The chain low-density ethylene-α-olefin copolymer may not be cut only when the plate is cut while the film is temporarily attached to the plate (the cut is inferior), and it is transparent. Somewhat inferior in properties, high-density polyethylene has very poor transparency, low tear strength, polypropylene has orientation, and may cause problems when pasting, punching and processing on metal plates. When used in combination with a resin, there were problems such as deterioration of transparency.

[0006]

As described above, the conventional surface protective film is excellent in some aspects but has some problems in other aspects. Therefore, the present invention overcomes these drawbacks, that is, heat resistance, cold resistance, transparency, scratch resistance, tensile strength, yield strength, drawing workability, punching workability, cutting performance, curl resistance and An object of the present invention is to provide a surface protective film having excellent adhesiveness between a pressure sensitive adhesive and a substrate.

[0007]

The present inventor has recently found that an ultra-low density ethylene-α-olefin copolymer having a density of 0.91 g / ml or less, which the applicant of the present invention has commercialized and commercialized, has a melting point of 116 ° C. As mentioned above, the heat resistance, the mechanical strength, and the excellent transparency are examined, and the availability as a surface protection film is examined. It is difficult to produce a film, and although the obtained film is superior in heat resistance and tensile strength to high pressure method low density polyethylene,
It was found that the film was still unsatisfactory, the stiffness was low, the handleability of the film was poor, and the films caused blocking, so that the film could not be used as it is as a surface protective film. Therefore, the present inventor takes advantage of the excellent physical properties of the ultra-low density ethylene-α-olefin copolymer, and in order to improve the drawbacks thereof, a large number of resin compositions prepared by blending various polyolefin-based resins into the copolymer. Was produced, and a film was formed to evaluate the surface protective film, and when the two specific types of polyolefin were blended in the ultra-low density ethylene-α-olefin copolymer in a specific ratio, The inventors have found that the problems of the present invention can be solved and completed the present invention.

That is, the present invention has a density of 0.885-
0.910 g / ml, melt index 0.1-3 g
/ 10 minutes, melting point 116 ° C. or higher, α-olefin content 1
2 to 20% by weight of ultra-low density linear ethylene-α-olefin copolymer (hereinafter, also referred to as VLDPE) 100
Parts by weight, vinyl acetate content produced by the high pressure radical polymerization method 3 to 25% by weight, melt index 0.3 to 5 g
/ 10 min ethylene-vinyl acetate copolymer (hereinafter, EV
Also described as A) 10 to 100 parts by weight, density 0.90 to
0.91 g / ml, melt flow rate 3 to 30 g / 1
0 minute polypropylene (hereinafter also referred to as PP) 10
The present invention relates to a surface protection film, which is characterized in that a pressure-sensitive adhesive layer is provided on a film obtained by molding and processing a resin composition consisting of 100 parts by weight.

The ultra-low density linear ethylene-α-olefin copolymer (VLDPE) used in the present invention means a transition metal compound of Group 4-8 of the periodic table and an organic metal of Group 1-3. It is produced by a gas phase / low pressure method using a catalyst system formed by combining with a compound, a so-called Ziegler-Natta catalyst, and has a density of 0.885 to 0.910.
g / ml, melt index 0.1 to 3 g / 10
Min, melting point is above 116 ° C., and α-olefin content is from 12 to 20% by weight. If the density of VLDPE is less than 0.885 g / ml, the films block each other, the stiffness is weak, the film formation is difficult, and the heat resistance is poor. If it exceeds 0.910 g / ml, EVA or PP
Compatibility with, transparency, and elasticity deteriorate, which is not desirable.
Also, the melt index of VLDPE is 0.1 g / 1.
If it is less than 0 minutes, the film-forming property is poor, and if it exceeds 3 g / 10 minutes, the tensile strength, scratch resistance and the like are deteriorated, which is not desirable. VL
When the melting point of DPE is less than 116 ° C, heat resistance cannot be obtained, which is not desirable.

The α-olefin of VLDPE includes butene-1, hexene-1, octene-1,4-methyl-.
Penten-1 or the like is used, and the content thereof is 12 to 20% by weight as described above, but if it is less than 12% by weight, transparency, elasticity, compatibility with EVA and PP are poor, and 20% by weight. When it exceeds, blocking occurs between the films,
It is not desirable because it has poor rigidity, film formation is difficult, and heat resistance is poor.

A typical method for producing VLDPE in the present invention is as follows: At a temperature of 10 to 80 ° C. and a pressure of 7,000 kPa or less in a fluidized bed reaction zone, the molar ratio of (a) higher α-olefin: ethylene is: 0.35: 1 to 8.0:
1, and at least one higher α-olefin having 3 to 8 carbon atoms, and (b) at least 25
A gas mixture containing mol% of at least one diluent gas is represented by the formula: Mg _m Ti (OR) _n X _p [ED] _q (wherein R is an aliphatic or aromatic group having 1 to 14 carbon atoms). Represents a group hydrocarbon group or a group COR ′, R ′ represents an aliphatic or aromatic hydrocarbon group having 1 to 14 carbon atoms, and X
Is selected from the group consisting of chlorine atom, bromine atom, iodine atom and mixtures thereof, and ED is an organic group selected from the group consisting of alkyl esters of aliphatic or aromatic acids, aliphatic ethers, cyclic ethers and aliphatic ketones. Represents an electron donating compound, m is 0.5 to 56, n is 0, 1 or 2, p is 2 to 116, and q is 2 to 85). Is continuously contacted with particles of a catalyst system consisting of and the precursor composition is diluted with an inert carrier material and is of the formula: Al (R ′) _d X ′ _e H _f (where X ′ is a chlorine atom). Or a group OR ″, R ′ and R ″ represent a saturated hydrocarbon group having 1 to 14 carbon atoms, e is 0 to 1.5, f is 0 or 1, and d is
+ E + f = 3), and the activation compound is completely activated in the reaction zone at a molar ratio of total aluminum: titanium of 10: 1.
Use in an amount to give ~ 400: 1. The above V
The method for producing LDPE is described in detail in JP-A-59-230011.

The ethylene-vinyl acetate copolymer (EVA) used in the present invention is produced by a high pressure radical polymerization method and has a straight chain branching and a vinyl acetate content of 3 to 25% by weight, Melt index 0.3-5g / 1
It is in the range of 0 minutes. When the vinyl acetate content of EVA is less than 3% by weight, elasticity, compatibility with VLDPE and PP, transparency, film-forming property, cold resistance and the like are insufficient, and when it exceeds 25% by weight, the film is Causes blocking, has poor stiffness, and has poor heat resistance, which is not desirable. E
When the melt index of VA is less than 0.3 g / ml, the film-forming property of the film is deteriorated, and when it exceeds 5 g / 10 minutes, the tensile strength and scratch resistance of the film become insufficient, which is not desirable.

In the present invention, EVA is VLDPE10.
It is used in an amount of 10 to 100 parts by weight based on 0 parts by weight. 1
If it is less than 0 parts by weight, the film-forming property, transparency, cold resistance, elasticity, tear resistance, etc. are poor, and if it exceeds 100 parts by weight, the rigidity of the film is weakened and the handleability is deteriorated, and the heat resistance is deteriorated. In addition, drawing workability and punching workability are also deteriorated, which is not desirable.

In the present invention, polypropylene (PP) means homopolymerization of propylene in the presence of a Ziegler-Natta type or its applied type catalyst system, propylene and a small amount of ethylene, butene-1, hexene-1,4-methyl-. It is a copolymer of pentene-1 and the like and has a density of 0.90 to
0.91 g / ml, melt flow rate (ie 23
Melt index measured at 0 ° C.) 3 to 30 g / 10
Minutes. When the density of PP is less than 0.90 g / ml, the heat resistance, tensile strength, waist strength of the film and the like are poor, and when it exceeds 0.91 g / ml, polypropylene having 90% by weight or more of propylene cannot be polymerized, Not available. In addition, the melt flow rate of PP is 3 g / 10
If it is less than 10 minutes, the film-forming property is inferior, and if it exceeds 30 g / 10 minutes, the tensile strength and scratch resistance are inferior, which is not desirable.

In the present invention, PP is VLDPE100.
It is used in 10 to 100 parts by weight with respect to parts by weight. 10
When it is less than 100 parts by weight, heat resistance, tensile strength, yield point strength, scratch resistance, drawing workability, punching workability, cutting property, blocking resistance, etc. deteriorate, and when it exceeds 100 parts by weight, cold resistance, tear resistance and wrinkle resistance. Properties, curl resistance, elasticity, and anchoring property of the pressure-sensitive adhesive are deteriorated, which is not desirable.

In order to produce a base film of the surface protective film of the present invention, that is, a film before the pressure-sensitive adhesive layer is provided (hereinafter, simply referred to as a base film), first, the above-mentioned VLDPE and EVA are used. A resin composition comprising and PP is prepared. At this time, various additives such as an antioxidant, a weather resistance improver, an ultraviolet absorber, and the like are added to the resin composition.
A colorant, a pigment, a dye, a filler, an antistatic agent, an antifogging agent, a cross-linking agent, a flame retardant, an antirust agent, an antibacterial agent, a fragrance, a plasticizer, a processing aid and the like may be appropriately mixed. After heating and kneading the resin composition containing additives as desired at 170 to 230 ° C., the resin composition may be molded into a base film by pelletizing, but each of VLDPE, EVA, PP and the like may be used. The pellet may be mixed with a masterbatch of various additives, if desired, to obtain a resin composition for forming a base film.

Then, the above resin composition for forming a base film is melt-extruded by an extruder and then subjected to an inflation method by air cooling or water cooling or a T-die method using a cooling roll to obtain a base film. .

In the present invention, the thickness of the base film is not particularly limited, but is preferably in the range of 30 to 500 μm. If it is less than 30 μm, the tensile strength, tear strength, etc. are insufficient and handling is difficult.
If it exceeds m, the cost is increased, and the punching workability, the drawing workability, the cuttability, etc. are deteriorated, which is not desirable.

The surface protective film of the present invention can be produced by applying a pressure-sensitive adhesive dissolved in a solvent onto the above-mentioned base film and drying the film, or the above-mentioned base film and the pressure-sensitive adhesive. May be produced by a two-layer coextrusion method in which and are simultaneously extruded by inflation or T-die. The pressure-sensitive adhesive layer provided as described above may be provided on the entire one surface of the substrate film or may be provided on only a part of the one surface.

As the pressure-sensitive adhesive used in the present invention, natural rubber or synthetic rubber such as butyl rubber, ethylene propylene rubber, polyisoprene rubber, styrene-butadiene rubber, polybutadiene rubber, atactic polypropylene, polybutyl acrylate, Polyisobutylene, ethylene-vinyl acetate copolymer, rubber polymers such as ethylene-acrylic acid ester, asphalt, pine resin,
A synthetic rosin, low-molecular-weight polystyrene, an asphalt or rosin-based substance such as polyterpene, a petroleum resin or the like as a main component, to which a plasticizer, a lubricant or the like is appropriately mixed can be used.

In the present invention, the surface of the substrate film or the surface protective film may be subjected to corona discharge treatment to improve the adhesiveness.

[0022]

The present invention will be described in more detail based on the following examples, but the invention is not intended to be limited to these examples. Example 1 Production of substrate film Density 0.905 g / ml, melt index 1 g / 1
0 minutes, melting point 117 ° C., butene-1 content 13% by weight gas phase ultra-low density ethylene-butene-1 copolymer (manufactured by Union Carbide, trade name: DFDA-1137) 100 parts by weight, high-pressure radical weight 90% by weight of an ethylene-vinyl acetate copolymer (manufactured by Nippon Unicar, trade name: NUC-3753) having a vinyl acetate content of 15% by weight and a melt index of 1.5 g / 10 min manufactured by a legal method, and a density of 0.91 g /
ml, a resin composition consisting of 10 parts by weight of a polypropylene (manufactured by Tonen Kagaku, trade name: F-409B) having a melt flow rate of 9 g / 10 min at 180 ° C. in a Banbury mixer.
After kneading for 10 minutes, pelletized with a granulator. Next, from the pellets of this resin composition, a thickness of 100 μm and a folding diameter of 235 m were obtained by an air cooling method under the following apparatus and processing conditions.
m blown film was produced. This is used as a base film: (1) Extrusion device: Φ40 mm inflation film manufacturing device (manufactured by Placo Co., Ltd.) (2) Die: Φ75 mm, die gap width 1.5 mm,
Extrusion temperature 185 ° C (made by Modern Machinery Co., Ltd.) (3) Cooling device: with single lip straight and conical color (4) Discharge rate: 15 kg / hour (5) Blow ratio: 2.0 (6) Frost line: 180 mm.

[0023] Evaluation (1) Tensile strength of the base film: machine direction 340 kg / cm ² lateral 260 kg / cm ² (measured in accordance with ASTM D882) (2) Elongation: longitudinal 530% transverse direction 720% (ASTM (Measured according to D882) (3) 1% siccant modulus (waist strength): longitudinal direction 1
850 kg / cm ² Horizontal direction 2000 kg / cm ² 100% siccant modulus: Vertical direction 127 kg / cm
² Lateral direction 75kg / cm ² (measured according to ASTM D882) (4) Tear strength: longitudinal direction 97kg / cm Lateral direction 215kg / cm (measured according to ASTM D1004) (5) Yield point strength: longitudinal direction 130 kg / cm ² Lateral direction 95 kg / cm ² (measured in accordance with ASTM D882) (6) Puncture resistance: 250 g [Measured in accordance with NUC method (using an Instron type pressure tester, nail-shaped push rod Press to pierce and puncture, and measure the load when it is torn)] (7) Haze: 3.2% (measured in accordance with ASTM D1003) (8) Scratch resistance: The base film surface has a half radius of 0.12
A 5 mm stainless needle was placed vertically, a 5 g weight was attached to the needle, and the needle was reciprocated 100 times to the left and right at a speed of 30 times per minute, but no scratch occurred. (9) Low temperature resistance: The base film was bent at −50 ° C., but no brittle fracture occurred.

Production of Surface Protective Film Next, the surface of the base film is subjected to corona discharge treatment, and a pressure-sensitive adhesive having the following composition is applied to the surface in a thickness of 5 μm and dried to obtain a surface protective film. It was Pressure-sensitive adhesive composition Styrene-butadiene-styrene block copolymer (manufactured by Shell Chemical Co., Ltd., trade name: Kraton G-1657) 100 parts by weight Hydrogenated petroleum resin (manufactured by Exxon Chemical Co., trade name: Escoletz 5300) 50 parts by weight ethylene- Vinyl acetate copolymer (manufactured by Nippon Unicar, product name: NUC-3185) 50 parts by weight Octadecyl isocyanate-added polyethyleneimine (manufactured by Nippon Shokubai) 1 part by weight Hindered phenol type antioxidant (manufactured by Nippon Ciba Geigy, product name: Irganox) 1010) 1 part by weight

Evaluation of Workability of Surface Protective Film (1) Punching Workability: The work was adhered to an aluminum plate having a thickness of 0.4 mm and punched with a 50φ punch, but the surface protective film was also punched cleanly. (2) Drawability: Drawability was performed three times, but no floating or tearing of the surface protection film occurred. (3) Cuttability: It was attached to an acrylic plate and cut with a saw, but it was cut cleanly and the film cut part did not expand or contract. (4) Curling resistance: stuck to a glass plate and kept at 60 ° C for 10
It was left for 0 days, but it was not curled and peeled off.

Examples 2 to 4 Resin compositions were prepared by changing the types or amounts of VLDPE, EVA and PP used in Example 1, and then, Example 1
A surface protective film was produced in the same manner as in 1., and the film was evaluated in the same manner as in Example 1. The results are summarized in Table 1.

Comparative Examples 1 to 3 VLDPE, EVA or P as the resin for the substrate film
The same operation as in Example 1 was carried out except that P was used alone to produce an inflation film having a thickness of 100 μm and a folding diameter of 235 mm, and a surface protection film was produced from the film for evaluation. The results are summarized in Table 2.

[0028]

[Table 1]

[0029]

[Table 2]

(Footnotes in Tables 1 and 2) * 1 Trade name of DFDA-1137 = ethylene-butene-1 copolymer (manufactured by Union Carbite, melt index 1 g / 10 minutes, density 0.905 g / ml) * 2 ETS-9063 = trade name of ethylene-butene-1 copolymer (manufactured by Union Carbide, melt index 0.5 g / 10 min, density 0.910 g / ml) * 3 FB-821 = ethylene-vinyl acetate copolymer Combined product name (Made by Nippon Unicar, melt index 3g / 1
0 minutes, vinyl acetate content 10% by weight) * 4 NUC-3753 = trade name of ethylene-vinyl acetate copolymer (manufactured by Nippon Unicar, Melt Index 1.
5 g / 10 min, vinyl acetate content 15% by weight) * 5 F-409B = trade name of polypropylene (manufactured by Tonen Kagaku, melt flow rate 9 g / 10 min, density 0.91)
0 g / ml) * 6 F-403CE = trade name of polypropylene (manufactured by Tonen Kagaku, melt flow rate 30 g / 10 minutes, density 0.
905 g / ml) * 7 The unit of each numerical value is as follows: tensile strength (kg / cm ² ), elongation (%), 1% siccant modulus (kg / cm ² ), 100% sicant modulus (k).
g / cm ² ), tear strength (kg / cm 2), yield strength (kg / cm ² ), puncture resistance (g), haze (%). Criteria for evaluation of scratch resistance and low temperature resistance (test method is Example 1
Reference): ○ (no scratch or brittle fracture occurred), △
(Slight scratches or brittle fracture occurred), × (Many scratches or brittle fracture occurred). * 8 Evaluation criteria for each workability (see Example 1 for the test method): Good (good), Fair (somewhat bad), Bad (bad).

[0031]

As described in detail above, the surface protective film of the present invention comprises the specific ultra-low density linear ethylene-α-olefin copolymer, ethylene-vinyl acetate copolymer and polypropylene. By blending in a specific ratio to form a base film, and providing a pressure-sensitive adhesive on it, heat resistance, cold resistance, transparency, scratch resistance, tensile strength, yield strength, drawing workability, punching workability It has excellent cuttability and curl resistance. As described above, the film for surface protection of the present invention has various properties required for the film, and thus can be suitably used as a film for surface protection of metal plate, glass plate, wood decorative plate, plastic plate and the like.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location C09J 7/02 JHU JLF // C08L 23/08 LDJ 23/12

Claims (1)

[Claims] 1. A density of 0.885 to 0.910 g / ml,
Melt index 0.1-3 g / 10 minutes, melting point 116
100 ° C. or more, ultra low density linear ethylene-α-olefin copolymer having an α-olefin content of 12 to 20% by weight, a vinyl acetate content of 3 to 25% by weight produced by a high-pressure radical polymerization method, Melt index 0.3-5g /
10 to 100 parts by weight of ethylene-vinyl acetate copolymer for 10 minutes, density of 0.90 to 0.91 g / ml, and melt flow rate of 3 to 30 g / 10 minutes of polypropylene 10 to 10
A surface protective film comprising a pressure-sensitive adhesive layer formed on a film obtained by molding a resin composition comprising 0 parts by weight.