JP2861035B2 - Surface protection film - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a surface protection film, and more particularly to a surface protection film to be attached to a surface of an object coated with a fluoroolefin vinyl ether copolymer coating. .

(Prior art) When transporting, storing, and processing various products such as plastic plates, painted steel plates, aluminum plates, stainless steel plates, and glass plates, use protective films on product surfaces to prevent damage, contamination, and deterioration. Attach. As such a surface protective film, a film having a base material of polyvinyl chloride or polyolefin and a pressure-sensitive adhesive layer of polyisobutyl rubber, acrylic rubber or the like is known.

On the other hand, a fluororesin paint is known as a coating material having excellent ultraviolet resistance and durability. For example, vinylidene fluoride resin, ethylene tetrafluoride resin, ethylene trifluoride chloride resin, and the like. Since these are insoluble in a solvent, they are usually used in a non-aqueous dispersion system, and require high-temperature baking at about 250 to 380 ° C. when forming a coating film, and the coating film surface is slightly inferior in smoothness (sharpness). Recently, fluoroolefin vinyl ether copolymers have been used as another type of fluororesin that has improved this point. Since it is a solvent-soluble type, it is easy to handle, and has features such as good clarity and recoatability. Further, since a carboxyl group, a hydroxyl group, or the like can be introduced into the resin derived from vinyl ether, the resin can be cured at room temperature with melamine, polyisocyanate, or the like.

(Problems to be Solved by the Invention) Since the fluoroolefin vinyl ether copolymer coating film is solvent-philic, there are some problems to be solved with respect to the surface protective film. For example, in the case of a protective film based on polyvinyl chloride, the plasticizer contained therein migrates to the surface of the coating film and easily swells the coating film. Polyolefin-based surface protection films have no problems caused by plasticizers, but the selection of adhesives is difficult due to the inherent properties of polyolefins such as inertness and non-polarity, and the weather resistance is poor. It is still insufficient as a protective film for use. Therefore,
In order to improve the tackiness of the polyolefin substrate, it was necessary to corona-treat the polyolefin surface, chemically oxidize the polyolefin itself, or apply a special primer. Further, in order to improve the weather resistance, it was necessary to incorporate a large amount of an expensive ultraviolet absorber. In addition, when an acrylic rubber-based adhesive is used, the solvent component in the adhesive easily migrates to the coating film surface, and causes dirt and gloss (gloss) change on the coating film surface.

(Means for Solving the Problems) In order to solve the above problems, the present invention provides a polyolefin film containing carbon black as a base material, and applies an isobutyl rubber-based pressure-sensitive adhesive layer to one surface of the base material. It was used as a surface protection film for a polymer coating film.

 Hereinafter, the present invention will be described in detail.

As the polyolefin, polyethylene, polypropylene, or ethylene / propylene copolymer is used. As the polyethylene, low density polyethylene having a density of 0.93 or less is preferable.

As carbon black, usually, particle size 20-80mμ,
Granular brand products for general pigments having a bulk density of 0.3 to 0.4 g / cm ³ are used. The amount added to the polyolefin is usually
It is selected from 0.05-10% by weight, preferably 0.1-5% by weight. When blending, carbon black content is 10 ~
50% by weight. It is preferable to use the master batch after appropriately diluting it.

A polyolefin film containing carbon black is used as a base material, and an isobutyl rubber-based pressure-sensitive adhesive is applied to one surface thereof. As the isobutyl rubber, a homopolymer of isobutylene, a random copolymer of isobutylene and normal butylene, a copolymer of isobutylene and isoprene or a vulcanized product thereof is used, and usually has a molecular weight of 150,000 to 150,000 and an unsaturated degree. Those having 0.5 to 5 mol% and a Mooney viscosity of 60 or less are used, and commercially available products such as Vistanex and Essobutyl (both are trade names of Esso Corporation) are known. Such isobutyl rubber is used as an isobutyl rubber-based pressure-sensitive adhesive by dissolving it in an organic solvent such as benzene, toluene, xylene, and normal hexane at a concentration of 3 to 30% by weight, preferably 5 to 20% by weight. In the present invention, since carbon black is contained in the polyolefin film serving as the base material, it is not necessary to add another polar rubber or tackifier to the isobutyl rubber-based adhesive, and to use a primer. And can be applied directly to the surface of the polyolefin film. But if necessary rosin,
It is possible to use a mixture of pine and indene / coumarone resin.

Fluoroolefin vinyl ether copolymer, tetrafluoroethylene, chlorotrifluoroethylene,
It is a copolymer of a fluoroolefin such as vinyl fluoride and vinylidene fluoride and a hydroxyalkyl vinyl ether such as hydroxyethyl vinyl ether, hydroxybutyl vinyl ether and hydroxypentyl vinyl ether. In the copolymerization, a comonomer such as hydroxyethyl acrylate, hydroxybutyl acrylate, acrylic acid, methacrylic acid, crotonic acid, and maleic acid may be used. The copolymer thus obtained has a fluorine atom and a hydroxyl group, and when acrylic acid or the like is copolymerized, a carboxyl group can be introduced. The fluorine atom content is 1 to 40% by weight, the hydroxyl group content is 20 to 150 as a hydroxyl value, the carboxyl group content is 0 to 15, preferably 2 to 13 as an acid value, and the weight average molecular weight is about 3,000 to 20,000. Is usually used. Such a copolymer is dissolved in an organic solvent such as hydrocarbons, ketones, esters, and alcohols together with a crosslinking agent to form a coating composition, which is then applied to a steel plate, an aluminum plate, or the like.
The coating film is formed by drying and baking. Examples of the crosslinking agent include melamine resins, amino resins such as urea resins, polyisocyanates such as hexamethylene diisocyanate, xylylene diisocyanate, tolylene diisocyanate, and methylene diphenylmethane diisocyanate, and isocyanates obtained by reacting the polyisocyanate with a polyhydric alcohol. Examples of the compound at the terminal of the group include a polyisocyanate compound blocked with a monohydric alcohol or a phenol compound. In addition, a desired colored coating film can be obtained by blending a pigment in these coating compositions.

Examples of the coating composition in which the above-mentioned fluoroolefin vinyl ether copolymer and a curing agent are appropriately blended include Bonflon (trade name of Bontile Co., Ltd.), Duflon (trade name of Nippon Paint Co., Ltd.), V-Flon (Dainippon Co., Ltd.) Paints Co., Ltd.) New Garmet (Toa Paint Co., Ltd.)
It is commercially available as (trade name) or the like, and can be cured under predetermined conditions after application to obtain a cured coating film.

In order to produce the surface protective film of the present invention, a polyolefin composition containing carbon black at a predetermined concentration is melt-extruded from a T-die or an inflation die to form a film. The film thickness is about 50-200μ,
In some cases, a film can be formed by coextrusion so that a polyethylene layer and a polyethylene / polypropylene mixed layer form two layers. The formed polyolefin film is then applied to a coater to apply an organic solvent solution of isobutyl rubber, and then dried to form an isobutyl rubber-based pressure-sensitive adhesive layer. The thickness of the pressure-sensitive adhesive layer is usually about 1 to 100 µ, preferably about 5 to 50 µ.

(Examples) Next, the present invention will be described specifically with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist.

Example 1 A toluene solution containing a fluoroethylene vinyl ether copolymer having an acid value of 10, a hydroxyl value of 100, a weight average molecular weight of 15,000, a fluorine atom content of 25% by weight and a predetermined amount of a blocked polyisocyanate compound as a curing agent (solids concentration 65
(% By weight) was applied to a degreased, caustic-treated and primer-treated aluminum plate, and heated at 140 ° C. for 30 minutes for baking and curing. The film thickness was 30 μ as a cured coating film.

A masterbatch pellet containing 30% by weight of carbon black for pigment with low density polyethylene having a density of 0.92 and a melt index of 4.2 is blended with the above low density polyethylene pellets so that the carbon black concentration becomes 1.0% by weight. A film was formed on a 120 μm thick film.

Next, a toluene solution of polyisobutylene rubber was applied to one side of the polyethylene film and dried to produce a surface protective film. The thickness of the pressure-sensitive adhesive layer in the surface protective film was 30 μm.

The obtained surface protective film was affixed to an aluminum plate provided with the above-mentioned cured film of the fluoroethylene vinyl ether copolymer, and a QUV accelerated exposure test was performed as described below to measure the peel strength and elongation retention. Also, JIS K5400
The glossiness of the coating surface was measured according to 6.7. The results are shown in Table 1. In Table 1, the surface glossiness "good" indicates the initial glossiness, and "poor" indicates that the glossiness has changed by 3% or more compared to the initial glossiness.

Test conditions Exposure is repeated with one cycle of ultraviolet irradiation 16 hours / 60 ° C and water coagulation 8 hours / 50 ° C.

Peel strength Displayed in g / 25mm according to JIS Z0237.

Elongation retention Indicated in% according to JIS Z0237.

Example 2 The results in Table 1 were obtained in the same manner as in Example 1 except that the content of carbon black was changed to 0.5% by weight.

Comparative Example 1 The results in Table 1 were obtained in the same manner as in Example 1 except that no carbon black was blended.

Comparative Example 2 The results in Table 1 were obtained in the same manner as in Example 1 except that an acrylic rubber (a 20% by weight toluene solution) was used instead of the polyisobutylene rubber.

Comparative Example 3 The results shown in Table 1 were obtained in the same manner as in Example 1 except that a PVC-based surface protection film (commercially available) coated with polyvinyl chloride and coated with an isobutyl rubber-based adhesive was used.

(Effect of the Invention) The fluoroolefin vinyl ether copolymer is soluble in a solvent, and can form a coating film with good clarity by an easy operation. The surface protective film of the present invention is to be adhered to the above-mentioned coating film, and the base material contains carbon black and is a polyolefin containing no plasticizer. No swelling solubilization, no stain, no change in luster (gloss). In addition, since isobutyl rubber having a lipophilic property is used as the pressure-sensitive adhesive layer, there is no danger that the solvent component in the isobutyl rubber migrates to the surface of the coating film. Furthermore, since the base material contains carbon black and exhibits an ultraviolet absorbing effect, the base material and the adhesive are hardly deteriorated by ultraviolet light, and the peel strength and the elongation retention are stable for a long period of time.

Claims (3)

(57) [Claims] 1. A surface protection film to be attached to the surface of an object coated with a fluoroolefin vinyl ether copolymer, wherein the adhesion surface of the protection film is an isobutyl rubber-based pressure-sensitive adhesive layer, and the base material is carbon black. A surface protective film, which is a polyolefin layer contained therein. 2. A coating film obtained by reacting a fluoroolefin vinyl ether copolymer having a carboxyl group and a hydroxyl group with a melamine resin or a polyisocyanate and curing the fluoroolefin vinyl ether copolymer coating film. 2. The surface protective film according to claim 1. 3. The surface protective film according to claim 1, wherein the substrate is a polyethylene layer containing 0.05 to 10% by weight of carbon black.